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
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
25 @c readline appendices use @vindex, @findex and @ftable,
26 @c annotate.texi and gdbmi use @findex.
30 @c !!set GDB manual's edition---not the same as GDB version!
31 @c This is updated by GNU Press.
34 @c !!set GDB edit command default editor
37 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
39 @c This is a dir.info fragment to support semi-automated addition of
40 @c manuals to an info tree.
41 @dircategory Software development
43 * Gdb: (gdb). The GNU debugger.
47 This file documents the @sc{gnu} debugger @value{GDBN}.
50 This is the @value{EDITION} Edition, of @cite{Debugging with
51 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
52 Version @value{GDBVN}.
54 Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,@*
55 1999, 2000, 2001, 2002, 2003, 2004, 2005@*
56 Free Software Foundation, Inc.
58 Permission is granted to copy, distribute and/or modify this document
59 under the terms of the GNU Free Documentation License, Version 1.1 or
60 any later version published by the Free Software Foundation; with the
61 Invariant Sections being ``Free Software'' and ``Free Software Needs
62 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
63 and with the Back-Cover Texts as in (a) below.
65 (a) The Free Software Foundation's Back-Cover Text is: ``You have
66 freedom to copy and modify this GNU Manual, like GNU software. Copies
67 published by the Free Software Foundation raise funds for GNU
72 @title Debugging with @value{GDBN}
73 @subtitle The @sc{gnu} Source-Level Debugger
75 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
76 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
80 \hfill (Send bugs and comments on @value{GDBN} to bug-gdb\@gnu.org.)\par
81 \hfill {\it Debugging with @value{GDBN}}\par
82 \hfill \TeX{}info \texinfoversion\par
86 @vskip 0pt plus 1filll
87 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
88 1996, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
89 Free Software Foundation, Inc.
91 Published by the Free Software Foundation @*
92 51 Franklin Street, Fifth Floor,
93 Boston, MA 02110-1301, USA@*
96 Permission is granted to copy, distribute and/or modify this document
97 under the terms of the GNU Free Documentation License, Version 1.1 or
98 any later version published by the Free Software Foundation; with the
99 Invariant Sections being ``Free Software'' and ``Free Software Needs
100 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
101 and with the Back-Cover Texts as in (a) below.
103 (a) The Free Software Foundation's Back-Cover Text is: ``You have
104 freedom to copy and modify this GNU Manual, like GNU software. Copies
105 published by the Free Software Foundation raise funds for GNU
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} Version
120 Copyright (C) 1988-2005 Free Software Foundation, Inc.
123 * Summary:: Summary of @value{GDBN}
124 * Sample Session:: A sample @value{GDBN} session
126 * Invocation:: Getting in and out of @value{GDBN}
127 * Commands:: @value{GDBN} commands
128 * Running:: Running programs under @value{GDBN}
129 * Stopping:: Stopping and continuing
130 * Stack:: Examining the stack
131 * Source:: Examining source files
132 * Data:: Examining data
133 * Macros:: Preprocessor Macros
134 * Tracepoints:: Debugging remote targets non-intrusively
135 * Overlays:: Debugging programs that use overlays
137 * Languages:: Using @value{GDBN} with different languages
139 * Symbols:: Examining the symbol table
140 * Altering:: Altering execution
141 * GDB Files:: @value{GDBN} files
142 * Targets:: Specifying a debugging target
143 * Remote Debugging:: Debugging remote programs
144 * Configurations:: Configuration-specific information
145 * Controlling GDB:: Controlling @value{GDBN}
146 * Sequences:: Canned sequences of commands
147 * TUI:: @value{GDBN} Text User Interface
148 * Interpreters:: Command Interpreters
149 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
150 * Annotations:: @value{GDBN}'s annotation interface.
151 * GDB/MI:: @value{GDBN}'s Machine Interface.
153 * GDB Bugs:: Reporting bugs in @value{GDBN}
154 * Formatting Documentation:: How to format and print @value{GDBN} documentation
156 * Command Line Editing:: Command Line Editing
157 * Using History Interactively:: Using History Interactively
158 * Installing GDB:: Installing GDB
159 * Maintenance Commands:: Maintenance Commands
160 * Remote Protocol:: GDB Remote Serial Protocol
161 * Agent Expressions:: The GDB Agent Expression Mechanism
162 * Copying:: GNU General Public License says
163 how you can copy and share GDB
164 * GNU Free Documentation License:: The license for this documentation
173 @unnumbered Summary of @value{GDBN}
175 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
176 going on ``inside'' another program while it executes---or what another
177 program was doing at the moment it crashed.
179 @value{GDBN} can do four main kinds of things (plus other things in support of
180 these) to help you catch bugs in the act:
184 Start your program, specifying anything that might affect its behavior.
187 Make your program stop on specified conditions.
190 Examine what has happened, when your program has stopped.
193 Change things in your program, so you can experiment with correcting the
194 effects of one bug and go on to learn about another.
197 You can use @value{GDBN} to debug programs written in C and C@t{++}.
198 For more information, see @ref{Supported languages,,Supported languages}.
199 For more information, see @ref{C,,C and C++}.
202 Support for Modula-2 is partial. For information on Modula-2, see
203 @ref{Modula-2,,Modula-2}.
206 Debugging Pascal programs which use sets, subranges, file variables, or
207 nested functions does not currently work. @value{GDBN} does not support
208 entering expressions, printing values, or similar features using Pascal
212 @value{GDBN} can be used to debug programs written in Fortran, although
213 it may be necessary to refer to some variables with a trailing
216 @value{GDBN} can be used to debug programs written in Objective-C,
217 using either the Apple/NeXT or the GNU Objective-C runtime.
220 * Free Software:: Freely redistributable software
221 * Contributors:: Contributors to GDB
225 @unnumberedsec Free software
227 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
228 General Public License
229 (GPL). The GPL gives you the freedom to copy or adapt a licensed
230 program---but every person getting a copy also gets with it the
231 freedom to modify that copy (which means that they must get access to
232 the source code), and the freedom to distribute further copies.
233 Typical software companies use copyrights to limit your freedoms; the
234 Free Software Foundation uses the GPL to preserve these freedoms.
236 Fundamentally, the General Public License is a license which says that
237 you have these freedoms and that you cannot take these freedoms away
240 @unnumberedsec Free Software Needs Free Documentation
242 The biggest deficiency in the free software community today is not in
243 the software---it is the lack of good free documentation that we can
244 include with the free software. Many of our most important
245 programs do not come with free reference manuals and free introductory
246 texts. Documentation is an essential part of any software package;
247 when an important free software package does not come with a free
248 manual and a free tutorial, that is a major gap. We have many such
251 Consider Perl, for instance. The tutorial manuals that people
252 normally use are non-free. How did this come about? Because the
253 authors of those manuals published them with restrictive terms---no
254 copying, no modification, source files not available---which exclude
255 them from the free software world.
257 That wasn't the first time this sort of thing happened, and it was far
258 from the last. Many times we have heard a GNU user eagerly describe a
259 manual that he is writing, his intended contribution to the community,
260 only to learn that he had ruined everything by signing a publication
261 contract to make it non-free.
263 Free documentation, like free software, is a matter of freedom, not
264 price. The problem with the non-free manual is not that publishers
265 charge a price for printed copies---that in itself is fine. (The Free
266 Software Foundation sells printed copies of manuals, too.) The
267 problem is the restrictions on the use of the manual. Free manuals
268 are available in source code form, and give you permission to copy and
269 modify. Non-free manuals do not allow this.
271 The criteria of freedom for a free manual are roughly the same as for
272 free software. Redistribution (including the normal kinds of
273 commercial redistribution) must be permitted, so that the manual can
274 accompany every copy of the program, both on-line and on paper.
276 Permission for modification of the technical content is crucial too.
277 When people modify the software, adding or changing features, if they
278 are conscientious they will change the manual too---so they can
279 provide accurate and clear documentation for the modified program. A
280 manual that leaves you no choice but to write a new manual to document
281 a changed version of the program is not really available to our
284 Some kinds of limits on the way modification is handled are
285 acceptable. For example, requirements to preserve the original
286 author's copyright notice, the distribution terms, or the list of
287 authors, are ok. It is also no problem to require modified versions
288 to include notice that they were modified. Even entire sections that
289 may not be deleted or changed are acceptable, as long as they deal
290 with nontechnical topics (like this one). These kinds of restrictions
291 are acceptable because they don't obstruct the community's normal use
294 However, it must be possible to modify all the @emph{technical}
295 content of the manual, and then distribute the result in all the usual
296 media, through all the usual channels. Otherwise, the restrictions
297 obstruct the use of the manual, it is not free, and we need another
298 manual to replace it.
300 Please spread the word about this issue. Our community continues to
301 lose manuals to proprietary publishing. If we spread the word that
302 free software needs free reference manuals and free tutorials, perhaps
303 the next person who wants to contribute by writing documentation will
304 realize, before it is too late, that only free manuals contribute to
305 the free software community.
307 If you are writing documentation, please insist on publishing it under
308 the GNU Free Documentation License or another free documentation
309 license. Remember that this decision requires your approval---you
310 don't have to let the publisher decide. Some commercial publishers
311 will use a free license if you insist, but they will not propose the
312 option; it is up to you to raise the issue and say firmly that this is
313 what you want. If the publisher you are dealing with refuses, please
314 try other publishers. If you're not sure whether a proposed license
315 is free, write to @email{licensing@@gnu.org}.
317 You can encourage commercial publishers to sell more free, copylefted
318 manuals and tutorials by buying them, and particularly by buying
319 copies from the publishers that paid for their writing or for major
320 improvements. Meanwhile, try to avoid buying non-free documentation
321 at all. Check the distribution terms of a manual before you buy it,
322 and insist that whoever seeks your business must respect your freedom.
323 Check the history of the book, and try to reward the publishers that
324 have paid or pay the authors to work on it.
326 The Free Software Foundation maintains a list of free documentation
327 published by other publishers, at
328 @url{http://www.fsf.org/doc/other-free-books.html}.
331 @unnumberedsec Contributors to @value{GDBN}
333 Richard Stallman was the original author of @value{GDBN}, and of many
334 other @sc{gnu} programs. Many others have contributed to its
335 development. This section attempts to credit major contributors. One
336 of the virtues of free software is that everyone is free to contribute
337 to it; with regret, we cannot actually acknowledge everyone here. The
338 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
339 blow-by-blow account.
341 Changes much prior to version 2.0 are lost in the mists of time.
344 @emph{Plea:} Additions to this section are particularly welcome. If you
345 or your friends (or enemies, to be evenhanded) have been unfairly
346 omitted from this list, we would like to add your names!
349 So that they may not regard their many labors as thankless, we
350 particularly thank those who shepherded @value{GDBN} through major
352 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
353 Jim Blandy (release 4.18);
354 Jason Molenda (release 4.17);
355 Stan Shebs (release 4.14);
356 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
357 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
358 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
359 Jim Kingdon (releases 3.5, 3.4, and 3.3);
360 and Randy Smith (releases 3.2, 3.1, and 3.0).
362 Richard Stallman, assisted at various times by Peter TerMaat, Chris
363 Hanson, and Richard Mlynarik, handled releases through 2.8.
365 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
366 in @value{GDBN}, with significant additional contributions from Per
367 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
368 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
369 much general update work leading to release 3.0).
371 @value{GDBN} uses the BFD subroutine library to examine multiple
372 object-file formats; BFD was a joint project of David V.
373 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
375 David Johnson wrote the original COFF support; Pace Willison did
376 the original support for encapsulated COFF.
378 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
380 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
381 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
383 Jean-Daniel Fekete contributed Sun 386i support.
384 Chris Hanson improved the HP9000 support.
385 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
386 David Johnson contributed Encore Umax support.
387 Jyrki Kuoppala contributed Altos 3068 support.
388 Jeff Law contributed HP PA and SOM support.
389 Keith Packard contributed NS32K support.
390 Doug Rabson contributed Acorn Risc Machine support.
391 Bob Rusk contributed Harris Nighthawk CX-UX support.
392 Chris Smith contributed Convex support (and Fortran debugging).
393 Jonathan Stone contributed Pyramid support.
394 Michael Tiemann contributed SPARC support.
395 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
396 Pace Willison contributed Intel 386 support.
397 Jay Vosburgh contributed Symmetry support.
398 Marko Mlinar contributed OpenRISC 1000 support.
400 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
402 Rich Schaefer and Peter Schauer helped with support of SunOS shared
405 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
406 about several machine instruction sets.
408 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
409 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
410 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
411 and RDI targets, respectively.
413 Brian Fox is the author of the readline libraries providing
414 command-line editing and command history.
416 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
417 Modula-2 support, and contributed the Languages chapter of this manual.
419 Fred Fish wrote most of the support for Unix System Vr4.
420 He also enhanced the command-completion support to cover C@t{++} overloaded
423 Hitachi America (now Renesas America), Ltd. sponsored the support for
424 H8/300, H8/500, and Super-H processors.
426 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
428 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
431 Toshiba sponsored the support for the TX39 Mips processor.
433 Matsushita sponsored the support for the MN10200 and MN10300 processors.
435 Fujitsu sponsored the support for SPARClite and FR30 processors.
437 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
440 Michael Snyder added support for tracepoints.
442 Stu Grossman wrote gdbserver.
444 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
445 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
447 The following people at the Hewlett-Packard Company contributed
448 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
449 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
450 compiler, and the Text User Interface (nee Terminal User Interface):
451 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
452 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
453 provided HP-specific information in this manual.
455 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
456 Robert Hoehne made significant contributions to the DJGPP port.
458 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
459 development since 1991. Cygnus engineers who have worked on @value{GDBN}
460 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
461 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
462 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
463 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
464 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
465 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
466 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
467 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
468 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
469 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
470 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
471 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
472 Zuhn have made contributions both large and small.
474 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
475 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
477 Jim Blandy added support for preprocessor macros, while working for Red
480 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
481 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
482 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
483 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
484 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
485 with the migration of old architectures to this new framework.
488 @chapter A Sample @value{GDBN} Session
490 You can use this manual at your leisure to read all about @value{GDBN}.
491 However, a handful of commands are enough to get started using the
492 debugger. This chapter illustrates those commands.
495 In this sample session, we emphasize user input like this: @b{input},
496 to make it easier to pick out from the surrounding output.
499 @c FIXME: this example may not be appropriate for some configs, where
500 @c FIXME...primary interest is in remote use.
502 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
503 processor) exhibits the following bug: sometimes, when we change its
504 quote strings from the default, the commands used to capture one macro
505 definition within another stop working. In the following short @code{m4}
506 session, we define a macro @code{foo} which expands to @code{0000}; we
507 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
508 same thing. However, when we change the open quote string to
509 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
510 procedure fails to define a new synonym @code{baz}:
519 @b{define(bar,defn(`foo'))}
523 @b{changequote(<QUOTE>,<UNQUOTE>)}
525 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
528 m4: End of input: 0: fatal error: EOF in string
532 Let us use @value{GDBN} to try to see what is going on.
535 $ @b{@value{GDBP} m4}
536 @c FIXME: this falsifies the exact text played out, to permit smallbook
537 @c FIXME... format to come out better.
538 @value{GDBN} is free software and you are welcome to distribute copies
539 of it under certain conditions; type "show copying" to see
541 There is absolutely no warranty for @value{GDBN}; type "show warranty"
544 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
549 @value{GDBN} reads only enough symbol data to know where to find the
550 rest when needed; as a result, the first prompt comes up very quickly.
551 We now tell @value{GDBN} to use a narrower display width than usual, so
552 that examples fit in this manual.
555 (@value{GDBP}) @b{set width 70}
559 We need to see how the @code{m4} built-in @code{changequote} works.
560 Having looked at the source, we know the relevant subroutine is
561 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
562 @code{break} command.
565 (@value{GDBP}) @b{break m4_changequote}
566 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
570 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
571 control; as long as control does not reach the @code{m4_changequote}
572 subroutine, the program runs as usual:
575 (@value{GDBP}) @b{run}
576 Starting program: /work/Editorial/gdb/gnu/m4/m4
584 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
585 suspends execution of @code{m4}, displaying information about the
586 context where it stops.
589 @b{changequote(<QUOTE>,<UNQUOTE>)}
591 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
593 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
597 Now we use the command @code{n} (@code{next}) to advance execution to
598 the next line of the current function.
602 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
607 @code{set_quotes} looks like a promising subroutine. We can go into it
608 by using the command @code{s} (@code{step}) instead of @code{next}.
609 @code{step} goes to the next line to be executed in @emph{any}
610 subroutine, so it steps into @code{set_quotes}.
614 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
616 530 if (lquote != def_lquote)
620 The display that shows the subroutine where @code{m4} is now
621 suspended (and its arguments) is called a stack frame display. It
622 shows a summary of the stack. We can use the @code{backtrace}
623 command (which can also be spelled @code{bt}), to see where we are
624 in the stack as a whole: the @code{backtrace} command displays a
625 stack frame for each active subroutine.
628 (@value{GDBP}) @b{bt}
629 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
631 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
633 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
634 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
636 #4 0x79dc in expand_input () at macro.c:40
637 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
641 We step through a few more lines to see what happens. The first two
642 times, we can use @samp{s}; the next two times we use @code{n} to avoid
643 falling into the @code{xstrdup} subroutine.
647 0x3b5c 532 if (rquote != def_rquote)
649 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
650 def_lquote : xstrdup(lq);
652 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
655 538 len_lquote = strlen(rquote);
659 The last line displayed looks a little odd; we can examine the variables
660 @code{lquote} and @code{rquote} to see if they are in fact the new left
661 and right quotes we specified. We use the command @code{p}
662 (@code{print}) to see their values.
665 (@value{GDBP}) @b{p lquote}
666 $1 = 0x35d40 "<QUOTE>"
667 (@value{GDBP}) @b{p rquote}
668 $2 = 0x35d50 "<UNQUOTE>"
672 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
673 To look at some context, we can display ten lines of source
674 surrounding the current line with the @code{l} (@code{list}) command.
680 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
682 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
685 538 len_lquote = strlen(rquote);
686 539 len_rquote = strlen(lquote);
693 Let us step past the two lines that set @code{len_lquote} and
694 @code{len_rquote}, and then examine the values of those variables.
698 539 len_rquote = strlen(lquote);
701 (@value{GDBP}) @b{p len_lquote}
703 (@value{GDBP}) @b{p len_rquote}
708 That certainly looks wrong, assuming @code{len_lquote} and
709 @code{len_rquote} are meant to be the lengths of @code{lquote} and
710 @code{rquote} respectively. We can set them to better values using
711 the @code{p} command, since it can print the value of
712 any expression---and that expression can include subroutine calls and
716 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
718 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
723 Is that enough to fix the problem of using the new quotes with the
724 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
725 executing with the @code{c} (@code{continue}) command, and then try the
726 example that caused trouble initially:
732 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
739 Success! The new quotes now work just as well as the default ones. The
740 problem seems to have been just the two typos defining the wrong
741 lengths. We allow @code{m4} exit by giving it an EOF as input:
745 Program exited normally.
749 The message @samp{Program exited normally.} is from @value{GDBN}; it
750 indicates @code{m4} has finished executing. We can end our @value{GDBN}
751 session with the @value{GDBN} @code{quit} command.
754 (@value{GDBP}) @b{quit}
758 @chapter Getting In and Out of @value{GDBN}
760 This chapter discusses how to start @value{GDBN}, and how to get out of it.
764 type @samp{@value{GDBP}} to start @value{GDBN}.
766 type @kbd{quit} or @kbd{C-d} to exit.
770 * Invoking GDB:: How to start @value{GDBN}
771 * Quitting GDB:: How to quit @value{GDBN}
772 * Shell Commands:: How to use shell commands inside @value{GDBN}
773 * Logging output:: How to log @value{GDBN}'s output to a file
777 @section Invoking @value{GDBN}
779 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
780 @value{GDBN} reads commands from the terminal until you tell it to exit.
782 You can also run @code{@value{GDBP}} with a variety of arguments and options,
783 to specify more of your debugging environment at the outset.
785 The command-line options described here are designed
786 to cover a variety of situations; in some environments, some of these
787 options may effectively be unavailable.
789 The most usual way to start @value{GDBN} is with one argument,
790 specifying an executable program:
793 @value{GDBP} @var{program}
797 You can also start with both an executable program and a core file
801 @value{GDBP} @var{program} @var{core}
804 You can, instead, specify a process ID as a second argument, if you want
805 to debug a running process:
808 @value{GDBP} @var{program} 1234
812 would attach @value{GDBN} to process @code{1234} (unless you also have a file
813 named @file{1234}; @value{GDBN} does check for a core file first).
815 Taking advantage of the second command-line argument requires a fairly
816 complete operating system; when you use @value{GDBN} as a remote
817 debugger attached to a bare board, there may not be any notion of
818 ``process'', and there is often no way to get a core dump. @value{GDBN}
819 will warn you if it is unable to attach or to read core dumps.
821 You can optionally have @code{@value{GDBP}} pass any arguments after the
822 executable file to the inferior using @code{--args}. This option stops
825 gdb --args gcc -O2 -c foo.c
827 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
828 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
830 You can run @code{@value{GDBP}} without printing the front material, which describes
831 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
838 You can further control how @value{GDBN} starts up by using command-line
839 options. @value{GDBN} itself can remind you of the options available.
849 to display all available options and briefly describe their use
850 (@samp{@value{GDBP} -h} is a shorter equivalent).
852 All options and command line arguments you give are processed
853 in sequential order. The order makes a difference when the
854 @samp{-x} option is used.
858 * File Options:: Choosing files
859 * Mode Options:: Choosing modes
860 * Startup:: What @value{GDBN} does during startup
864 @subsection Choosing files
866 When @value{GDBN} starts, it reads any arguments other than options as
867 specifying an executable file and core file (or process ID). This is
868 the same as if the arguments were specified by the @samp{-se} and
869 @samp{-c} (or @samp{-p} options respectively. (@value{GDBN} reads the
870 first argument that does not have an associated option flag as
871 equivalent to the @samp{-se} option followed by that argument; and the
872 second argument that does not have an associated option flag, if any, as
873 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
874 If the second argument begins with a decimal digit, @value{GDBN} will
875 first attempt to attach to it as a process, and if that fails, attempt
876 to open it as a corefile. If you have a corefile whose name begins with
877 a digit, you can prevent @value{GDBN} from treating it as a pid by
878 prefixing it with @file{./}, e.g.@: @file{./12345}.
880 If @value{GDBN} has not been configured to included core file support,
881 such as for most embedded targets, then it will complain about a second
882 argument and ignore it.
884 Many options have both long and short forms; both are shown in the
885 following list. @value{GDBN} also recognizes the long forms if you truncate
886 them, so long as enough of the option is present to be unambiguous.
887 (If you prefer, you can flag option arguments with @samp{--} rather
888 than @samp{-}, though we illustrate the more usual convention.)
890 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
891 @c way, both those who look for -foo and --foo in the index, will find
895 @item -symbols @var{file}
897 @cindex @code{--symbols}
899 Read symbol table from file @var{file}.
901 @item -exec @var{file}
903 @cindex @code{--exec}
905 Use file @var{file} as the executable file to execute when appropriate,
906 and for examining pure data in conjunction with a core dump.
910 Read symbol table from file @var{file} and use it as the executable
913 @item -core @var{file}
915 @cindex @code{--core}
917 Use file @var{file} as a core dump to examine.
919 @item -c @var{number}
920 @item -pid @var{number}
921 @itemx -p @var{number}
924 Connect to process ID @var{number}, as with the @code{attach} command.
925 If there is no such process, @value{GDBN} will attempt to open a core
926 file named @var{number}.
928 @item -command @var{file}
930 @cindex @code{--command}
932 Execute @value{GDBN} commands from file @var{file}. @xref{Command
933 Files,, Command files}.
935 @item -eval-command @var{command}
936 @itemx -ex @var{command}
937 @cindex @code{--eval-command}
939 Execute a single @value{GDBN} command.
941 This option may be used multiple times to call multiple commands. It may
942 also be interleaved with @samp{-command} as required.
945 @value{GDBP} -ex 'target sim' -ex 'load' \
946 -x setbreakpoints -ex 'run' a.out
949 @item -directory @var{directory}
950 @itemx -d @var{directory}
951 @cindex @code{--directory}
953 Add @var{directory} to the path to search for source files.
957 @cindex @code{--readnow}
959 Read each symbol file's entire symbol table immediately, rather than
960 the default, which is to read it incrementally as it is needed.
961 This makes startup slower, but makes future operations faster.
966 @subsection Choosing modes
968 You can run @value{GDBN} in various alternative modes---for example, in
969 batch mode or quiet mode.
976 Do not execute commands found in any initialization files. Normally,
977 @value{GDBN} executes the commands in these files after all the command
978 options and arguments have been processed. @xref{Command Files,,Command
984 @cindex @code{--quiet}
985 @cindex @code{--silent}
987 ``Quiet''. Do not print the introductory and copyright messages. These
988 messages are also suppressed in batch mode.
991 @cindex @code{--batch}
992 Run in batch mode. Exit with status @code{0} after processing all the
993 command files specified with @samp{-x} (and all commands from
994 initialization files, if not inhibited with @samp{-n}). Exit with
995 nonzero status if an error occurs in executing the @value{GDBN} commands
996 in the command files.
998 Batch mode may be useful for running @value{GDBN} as a filter, for
999 example to download and run a program on another computer; in order to
1000 make this more useful, the message
1003 Program exited normally.
1007 (which is ordinarily issued whenever a program running under
1008 @value{GDBN} control terminates) is not issued when running in batch
1012 @cindex @code{--batch-silent}
1013 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1014 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1015 unaffected). This is much quieter than @samp{-silent} and would be useless
1016 for an interactive session.
1018 This is particularly useful when using targets that give @samp{Loading section}
1019 messages, for example.
1021 Note that targets that give their output via @value{GDBN}, as opposed to
1022 writing directly to @code{stdout}, will also be made silent.
1024 @item -return-child-result
1025 @cindex @code{--return-child-result}
1026 The return code from @value{GDBN} will be the return code from the child
1027 process (the process being debugged), with the following exceptions:
1031 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1032 internal error. In this case the exit code is the same as it would have been
1033 without @samp{-return-child-result}.
1035 The user quits with an explicit value. E.g., @samp{quit 1}.
1037 The child process never runs, or is not allowed to terminate, in which case
1038 the exit code will be -1.
1041 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1042 when @value{GDBN} is being used as a remote program loader or simulator
1047 @cindex @code{--nowindows}
1049 ``No windows''. If @value{GDBN} comes with a graphical user interface
1050 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1051 interface. If no GUI is available, this option has no effect.
1055 @cindex @code{--windows}
1057 If @value{GDBN} includes a GUI, then this option requires it to be
1060 @item -cd @var{directory}
1062 Run @value{GDBN} using @var{directory} as its working directory,
1063 instead of the current directory.
1067 @cindex @code{--fullname}
1069 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1070 subprocess. It tells @value{GDBN} to output the full file name and line
1071 number in a standard, recognizable fashion each time a stack frame is
1072 displayed (which includes each time your program stops). This
1073 recognizable format looks like two @samp{\032} characters, followed by
1074 the file name, line number and character position separated by colons,
1075 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1076 @samp{\032} characters as a signal to display the source code for the
1080 @cindex @code{--epoch}
1081 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1082 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1083 routines so as to allow Epoch to display values of expressions in a
1086 @item -annotate @var{level}
1087 @cindex @code{--annotate}
1088 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1089 effect is identical to using @samp{set annotate @var{level}}
1090 (@pxref{Annotations}). The annotation @var{level} controls how much
1091 information @value{GDBN} prints together with its prompt, values of
1092 expressions, source lines, and other types of output. Level 0 is the
1093 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1094 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1095 that control @value{GDBN}, and level 2 has been deprecated.
1097 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1101 @cindex @code{--args}
1102 Change interpretation of command line so that arguments following the
1103 executable file are passed as command line arguments to the inferior.
1104 This option stops option processing.
1106 @item -baud @var{bps}
1108 @cindex @code{--baud}
1110 Set the line speed (baud rate or bits per second) of any serial
1111 interface used by @value{GDBN} for remote debugging.
1113 @item -l @var{timeout}
1115 Set the timeout (in seconds) of any communication used by @value{GDBN}
1116 for remote debugging.
1118 @item -tty @var{device}
1119 @itemx -t @var{device}
1120 @cindex @code{--tty}
1122 Run using @var{device} for your program's standard input and output.
1123 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1125 @c resolve the situation of these eventually
1127 @cindex @code{--tui}
1128 Activate the @dfn{Text User Interface} when starting. The Text User
1129 Interface manages several text windows on the terminal, showing
1130 source, assembly, registers and @value{GDBN} command outputs
1131 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1132 Text User Interface can be enabled by invoking the program
1133 @samp{gdbtui}. Do not use this option if you run @value{GDBN} from
1134 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1137 @c @cindex @code{--xdb}
1138 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1139 @c For information, see the file @file{xdb_trans.html}, which is usually
1140 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1143 @item -interpreter @var{interp}
1144 @cindex @code{--interpreter}
1145 Use the interpreter @var{interp} for interface with the controlling
1146 program or device. This option is meant to be set by programs which
1147 communicate with @value{GDBN} using it as a back end.
1148 @xref{Interpreters, , Command Interpreters}.
1150 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1151 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1152 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1153 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1154 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1155 @sc{gdb/mi} interfaces are no longer supported.
1158 @cindex @code{--write}
1159 Open the executable and core files for both reading and writing. This
1160 is equivalent to the @samp{set write on} command inside @value{GDBN}
1164 @cindex @code{--statistics}
1165 This option causes @value{GDBN} to print statistics about time and
1166 memory usage after it completes each command and returns to the prompt.
1169 @cindex @code{--version}
1170 This option causes @value{GDBN} to print its version number and
1171 no-warranty blurb, and exit.
1176 @subsection What @value{GDBN} does during startup
1177 @cindex @value{GDBN} startup
1179 Here's the description of what @value{GDBN} does during session startup:
1183 Sets up the command interpreter as specified by the command line
1184 (@pxref{Mode Options, interpreter}).
1188 Reads the @dfn{init file} (if any) in your home directory@footnote{On
1189 DOS/Windows systems, the home directory is the one pointed to by the
1190 @code{HOME} environment variable.} and executes all the commands in
1194 Processes command line options and operands.
1197 Reads and executes the commands from init file (if any) in the current
1198 working directory. This is only done if the current directory is
1199 different from your home directory. Thus, you can have more than one
1200 init file, one generic in your home directory, and another, specific
1201 to the program you are debugging, in the directory where you invoke
1205 Reads command files specified by the @samp{-x} option. @xref{Command
1206 Files}, for more details about @value{GDBN} command files.
1209 Reads the command history recorded in the @dfn{history file}.
1210 @xref{Command History}, for more details about the command history and the
1211 files where @value{GDBN} records it.
1214 Init files use the same syntax as @dfn{command files} (@pxref{Command
1215 Files}) and are processed by @value{GDBN} in the same way. The init
1216 file in your home directory can set options (such as @samp{set
1217 complaints}) that affect subsequent processing of command line options
1218 and operands. Init files are not executed if you use the @samp{-nx}
1219 option (@pxref{Mode Options, ,Choosing modes}).
1221 @cindex init file name
1222 @cindex @file{.gdbinit}
1223 The @value{GDBN} init files are normally called @file{.gdbinit}.
1224 On some configurations of @value{GDBN}, the init file is known by a
1225 different name (these are typically environments where a specialized
1226 form of @value{GDBN} may need to coexist with other forms, hence a
1227 different name for the specialized version's init file). These are the
1228 environments with special init file names:
1231 @cindex @file{gdb.ini}
1233 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1234 the limitations of file names imposed by DOS filesystems. The Windows
1235 ports of @value{GDBN} use the standard name, but if they find a
1236 @file{gdb.ini} file, they warn you about that and suggest to rename
1237 the file to the standard name.
1239 @cindex @file{.vxgdbinit}
1241 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
1243 @cindex @file{.os68gdbinit}
1245 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
1247 @cindex @file{.esgdbinit}
1249 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
1252 CISCO 68k: @file{.cisco-gdbinit}
1257 @section Quitting @value{GDBN}
1258 @cindex exiting @value{GDBN}
1259 @cindex leaving @value{GDBN}
1262 @kindex quit @r{[}@var{expression}@r{]}
1263 @kindex q @r{(@code{quit})}
1264 @item quit @r{[}@var{expression}@r{]}
1266 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1267 @code{q}), or type an end-of-file character (usually @kbd{C-d}). If you
1268 do not supply @var{expression}, @value{GDBN} will terminate normally;
1269 otherwise it will terminate using the result of @var{expression} as the
1274 An interrupt (often @kbd{C-c}) does not exit from @value{GDBN}, but rather
1275 terminates the action of any @value{GDBN} command that is in progress and
1276 returns to @value{GDBN} command level. It is safe to type the interrupt
1277 character at any time because @value{GDBN} does not allow it to take effect
1278 until a time when it is safe.
1280 If you have been using @value{GDBN} to control an attached process or
1281 device, you can release it with the @code{detach} command
1282 (@pxref{Attach, ,Debugging an already-running process}).
1284 @node Shell Commands
1285 @section Shell commands
1287 If you need to execute occasional shell commands during your
1288 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1289 just use the @code{shell} command.
1293 @cindex shell escape
1294 @item shell @var{command string}
1295 Invoke a standard shell to execute @var{command string}.
1296 If it exists, the environment variable @code{SHELL} determines which
1297 shell to run. Otherwise @value{GDBN} uses the default shell
1298 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1301 The utility @code{make} is often needed in development environments.
1302 You do not have to use the @code{shell} command for this purpose in
1307 @cindex calling make
1308 @item make @var{make-args}
1309 Execute the @code{make} program with the specified
1310 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1313 @node Logging output
1314 @section Logging output
1315 @cindex logging @value{GDBN} output
1316 @cindex save @value{GDBN} output to a file
1318 You may want to save the output of @value{GDBN} commands to a file.
1319 There are several commands to control @value{GDBN}'s logging.
1323 @item set logging on
1325 @item set logging off
1327 @cindex logging file name
1328 @item set logging file @var{file}
1329 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1330 @item set logging overwrite [on|off]
1331 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1332 you want @code{set logging on} to overwrite the logfile instead.
1333 @item set logging redirect [on|off]
1334 By default, @value{GDBN} output will go to both the terminal and the logfile.
1335 Set @code{redirect} if you want output to go only to the log file.
1336 @kindex show logging
1338 Show the current values of the logging settings.
1342 @chapter @value{GDBN} Commands
1344 You can abbreviate a @value{GDBN} command to the first few letters of the command
1345 name, if that abbreviation is unambiguous; and you can repeat certain
1346 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1347 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1348 show you the alternatives available, if there is more than one possibility).
1351 * Command Syntax:: How to give commands to @value{GDBN}
1352 * Completion:: Command completion
1353 * Help:: How to ask @value{GDBN} for help
1356 @node Command Syntax
1357 @section Command syntax
1359 A @value{GDBN} command is a single line of input. There is no limit on
1360 how long it can be. It starts with a command name, which is followed by
1361 arguments whose meaning depends on the command name. For example, the
1362 command @code{step} accepts an argument which is the number of times to
1363 step, as in @samp{step 5}. You can also use the @code{step} command
1364 with no arguments. Some commands do not allow any arguments.
1366 @cindex abbreviation
1367 @value{GDBN} command names may always be truncated if that abbreviation is
1368 unambiguous. Other possible command abbreviations are listed in the
1369 documentation for individual commands. In some cases, even ambiguous
1370 abbreviations are allowed; for example, @code{s} is specially defined as
1371 equivalent to @code{step} even though there are other commands whose
1372 names start with @code{s}. You can test abbreviations by using them as
1373 arguments to the @code{help} command.
1375 @cindex repeating commands
1376 @kindex RET @r{(repeat last command)}
1377 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1378 repeat the previous command. Certain commands (for example, @code{run})
1379 will not repeat this way; these are commands whose unintentional
1380 repetition might cause trouble and which you are unlikely to want to
1381 repeat. User-defined commands can disable this feature; see
1382 @ref{Define, dont-repeat}.
1384 The @code{list} and @code{x} commands, when you repeat them with
1385 @key{RET}, construct new arguments rather than repeating
1386 exactly as typed. This permits easy scanning of source or memory.
1388 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1389 output, in a way similar to the common utility @code{more}
1390 (@pxref{Screen Size,,Screen size}). Since it is easy to press one
1391 @key{RET} too many in this situation, @value{GDBN} disables command
1392 repetition after any command that generates this sort of display.
1394 @kindex # @r{(a comment)}
1396 Any text from a @kbd{#} to the end of the line is a comment; it does
1397 nothing. This is useful mainly in command files (@pxref{Command
1398 Files,,Command files}).
1400 @cindex repeating command sequences
1401 @kindex C-o @r{(operate-and-get-next)}
1402 The @kbd{C-o} binding is useful for repeating a complex sequence of
1403 commands. This command accepts the current line, like @kbd{RET}, and
1404 then fetches the next line relative to the current line from the history
1408 @section Command completion
1411 @cindex word completion
1412 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1413 only one possibility; it can also show you what the valid possibilities
1414 are for the next word in a command, at any time. This works for @value{GDBN}
1415 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1417 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1418 of a word. If there is only one possibility, @value{GDBN} fills in the
1419 word, and waits for you to finish the command (or press @key{RET} to
1420 enter it). For example, if you type
1422 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1423 @c complete accuracy in these examples; space introduced for clarity.
1424 @c If texinfo enhancements make it unnecessary, it would be nice to
1425 @c replace " @key" by "@key" in the following...
1427 (@value{GDBP}) info bre @key{TAB}
1431 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1432 the only @code{info} subcommand beginning with @samp{bre}:
1435 (@value{GDBP}) info breakpoints
1439 You can either press @key{RET} at this point, to run the @code{info
1440 breakpoints} command, or backspace and enter something else, if
1441 @samp{breakpoints} does not look like the command you expected. (If you
1442 were sure you wanted @code{info breakpoints} in the first place, you
1443 might as well just type @key{RET} immediately after @samp{info bre},
1444 to exploit command abbreviations rather than command completion).
1446 If there is more than one possibility for the next word when you press
1447 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1448 characters and try again, or just press @key{TAB} a second time;
1449 @value{GDBN} displays all the possible completions for that word. For
1450 example, you might want to set a breakpoint on a subroutine whose name
1451 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1452 just sounds the bell. Typing @key{TAB} again displays all the
1453 function names in your program that begin with those characters, for
1457 (@value{GDBP}) b make_ @key{TAB}
1458 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1459 make_a_section_from_file make_environ
1460 make_abs_section make_function_type
1461 make_blockvector make_pointer_type
1462 make_cleanup make_reference_type
1463 make_command make_symbol_completion_list
1464 (@value{GDBP}) b make_
1468 After displaying the available possibilities, @value{GDBN} copies your
1469 partial input (@samp{b make_} in the example) so you can finish the
1472 If you just want to see the list of alternatives in the first place, you
1473 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1474 means @kbd{@key{META} ?}. You can type this either by holding down a
1475 key designated as the @key{META} shift on your keyboard (if there is
1476 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1478 @cindex quotes in commands
1479 @cindex completion of quoted strings
1480 Sometimes the string you need, while logically a ``word'', may contain
1481 parentheses or other characters that @value{GDBN} normally excludes from
1482 its notion of a word. To permit word completion to work in this
1483 situation, you may enclose words in @code{'} (single quote marks) in
1484 @value{GDBN} commands.
1486 The most likely situation where you might need this is in typing the
1487 name of a C@t{++} function. This is because C@t{++} allows function
1488 overloading (multiple definitions of the same function, distinguished
1489 by argument type). For example, when you want to set a breakpoint you
1490 may need to distinguish whether you mean the version of @code{name}
1491 that takes an @code{int} parameter, @code{name(int)}, or the version
1492 that takes a @code{float} parameter, @code{name(float)}. To use the
1493 word-completion facilities in this situation, type a single quote
1494 @code{'} at the beginning of the function name. This alerts
1495 @value{GDBN} that it may need to consider more information than usual
1496 when you press @key{TAB} or @kbd{M-?} to request word completion:
1499 (@value{GDBP}) b 'bubble( @kbd{M-?}
1500 bubble(double,double) bubble(int,int)
1501 (@value{GDBP}) b 'bubble(
1504 In some cases, @value{GDBN} can tell that completing a name requires using
1505 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1506 completing as much as it can) if you do not type the quote in the first
1510 (@value{GDBP}) b bub @key{TAB}
1511 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1512 (@value{GDBP}) b 'bubble(
1516 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1517 you have not yet started typing the argument list when you ask for
1518 completion on an overloaded symbol.
1520 For more information about overloaded functions, see @ref{C plus plus
1521 expressions, ,C@t{++} expressions}. You can use the command @code{set
1522 overload-resolution off} to disable overload resolution;
1523 see @ref{Debugging C plus plus, ,@value{GDBN} features for C@t{++}}.
1527 @section Getting help
1528 @cindex online documentation
1531 You can always ask @value{GDBN} itself for information on its commands,
1532 using the command @code{help}.
1535 @kindex h @r{(@code{help})}
1538 You can use @code{help} (abbreviated @code{h}) with no arguments to
1539 display a short list of named classes of commands:
1543 List of classes of commands:
1545 aliases -- Aliases of other commands
1546 breakpoints -- Making program stop at certain points
1547 data -- Examining data
1548 files -- Specifying and examining files
1549 internals -- Maintenance commands
1550 obscure -- Obscure features
1551 running -- Running the program
1552 stack -- Examining the stack
1553 status -- Status inquiries
1554 support -- Support facilities
1555 tracepoints -- Tracing of program execution without@*
1556 stopping the program
1557 user-defined -- User-defined commands
1559 Type "help" followed by a class name for a list of
1560 commands in that class.
1561 Type "help" followed by command name for full
1563 Command name abbreviations are allowed if unambiguous.
1566 @c the above line break eliminates huge line overfull...
1568 @item help @var{class}
1569 Using one of the general help classes as an argument, you can get a
1570 list of the individual commands in that class. For example, here is the
1571 help display for the class @code{status}:
1574 (@value{GDBP}) help status
1579 @c Line break in "show" line falsifies real output, but needed
1580 @c to fit in smallbook page size.
1581 info -- Generic command for showing things
1582 about the program being debugged
1583 show -- Generic command for showing things
1586 Type "help" followed by command name for full
1588 Command name abbreviations are allowed if unambiguous.
1592 @item help @var{command}
1593 With a command name as @code{help} argument, @value{GDBN} displays a
1594 short paragraph on how to use that command.
1597 @item apropos @var{args}
1598 The @code{apropos} command searches through all of the @value{GDBN}
1599 commands, and their documentation, for the regular expression specified in
1600 @var{args}. It prints out all matches found. For example:
1611 set symbol-reloading -- Set dynamic symbol table reloading
1612 multiple times in one run
1613 show symbol-reloading -- Show dynamic symbol table reloading
1614 multiple times in one run
1619 @item complete @var{args}
1620 The @code{complete @var{args}} command lists all the possible completions
1621 for the beginning of a command. Use @var{args} to specify the beginning of the
1622 command you want completed. For example:
1628 @noindent results in:
1639 @noindent This is intended for use by @sc{gnu} Emacs.
1642 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1643 and @code{show} to inquire about the state of your program, or the state
1644 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1645 manual introduces each of them in the appropriate context. The listings
1646 under @code{info} and under @code{show} in the Index point to
1647 all the sub-commands. @xref{Index}.
1652 @kindex i @r{(@code{info})}
1654 This command (abbreviated @code{i}) is for describing the state of your
1655 program. For example, you can list the arguments given to your program
1656 with @code{info args}, list the registers currently in use with @code{info
1657 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1658 You can get a complete list of the @code{info} sub-commands with
1659 @w{@code{help info}}.
1663 You can assign the result of an expression to an environment variable with
1664 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1665 @code{set prompt $}.
1669 In contrast to @code{info}, @code{show} is for describing the state of
1670 @value{GDBN} itself.
1671 You can change most of the things you can @code{show}, by using the
1672 related command @code{set}; for example, you can control what number
1673 system is used for displays with @code{set radix}, or simply inquire
1674 which is currently in use with @code{show radix}.
1677 To display all the settable parameters and their current
1678 values, you can use @code{show} with no arguments; you may also use
1679 @code{info set}. Both commands produce the same display.
1680 @c FIXME: "info set" violates the rule that "info" is for state of
1681 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1682 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1686 Here are three miscellaneous @code{show} subcommands, all of which are
1687 exceptional in lacking corresponding @code{set} commands:
1690 @kindex show version
1691 @cindex @value{GDBN} version number
1693 Show what version of @value{GDBN} is running. You should include this
1694 information in @value{GDBN} bug-reports. If multiple versions of
1695 @value{GDBN} are in use at your site, you may need to determine which
1696 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1697 commands are introduced, and old ones may wither away. Also, many
1698 system vendors ship variant versions of @value{GDBN}, and there are
1699 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1700 The version number is the same as the one announced when you start
1703 @kindex show copying
1704 @kindex info copying
1705 @cindex display @value{GDBN} copyright
1708 Display information about permission for copying @value{GDBN}.
1710 @kindex show warranty
1711 @kindex info warranty
1713 @itemx info warranty
1714 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1715 if your version of @value{GDBN} comes with one.
1720 @chapter Running Programs Under @value{GDBN}
1722 When you run a program under @value{GDBN}, you must first generate
1723 debugging information when you compile it.
1725 You may start @value{GDBN} with its arguments, if any, in an environment
1726 of your choice. If you are doing native debugging, you may redirect
1727 your program's input and output, debug an already running process, or
1728 kill a child process.
1731 * Compilation:: Compiling for debugging
1732 * Starting:: Starting your program
1733 * Arguments:: Your program's arguments
1734 * Environment:: Your program's environment
1736 * Working Directory:: Your program's working directory
1737 * Input/Output:: Your program's input and output
1738 * Attach:: Debugging an already-running process
1739 * Kill Process:: Killing the child process
1741 * Threads:: Debugging programs with multiple threads
1742 * Processes:: Debugging programs with multiple processes
1743 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1747 @section Compiling for debugging
1749 In order to debug a program effectively, you need to generate
1750 debugging information when you compile it. This debugging information
1751 is stored in the object file; it describes the data type of each
1752 variable or function and the correspondence between source line numbers
1753 and addresses in the executable code.
1755 To request debugging information, specify the @samp{-g} option when you run
1758 Programs that are to be shipped to your customers are compiled with
1759 optimizations, using the @samp{-O} compiler option. However, many
1760 compilers are unable to handle the @samp{-g} and @samp{-O} options
1761 together. Using those compilers, you cannot generate optimized
1762 executables containing debugging information.
1764 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1765 without @samp{-O}, making it possible to debug optimized code. We
1766 recommend that you @emph{always} use @samp{-g} whenever you compile a
1767 program. You may think your program is correct, but there is no sense
1768 in pushing your luck.
1770 @cindex optimized code, debugging
1771 @cindex debugging optimized code
1772 When you debug a program compiled with @samp{-g -O}, remember that the
1773 optimizer is rearranging your code; the debugger shows you what is
1774 really there. Do not be too surprised when the execution path does not
1775 exactly match your source file! An extreme example: if you define a
1776 variable, but never use it, @value{GDBN} never sees that
1777 variable---because the compiler optimizes it out of existence.
1779 Some things do not work as well with @samp{-g -O} as with just
1780 @samp{-g}, particularly on machines with instruction scheduling. If in
1781 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1782 please report it to us as a bug (including a test case!).
1783 @xref{Variables}, for more information about debugging optimized code.
1785 Older versions of the @sc{gnu} C compiler permitted a variant option
1786 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1787 format; if your @sc{gnu} C compiler has this option, do not use it.
1789 @value{GDBN} knows about preprocessor macros and can show you their
1790 expansion (@pxref{Macros}). Most compilers do not include information
1791 about preprocessor macros in the debugging information if you specify
1792 the @option{-g} flag alone, because this information is rather large.
1793 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1794 provides macro information if you specify the options
1795 @option{-gdwarf-2} and @option{-g3}; the former option requests
1796 debugging information in the Dwarf 2 format, and the latter requests
1797 ``extra information''. In the future, we hope to find more compact
1798 ways to represent macro information, so that it can be included with
1803 @section Starting your program
1809 @kindex r @r{(@code{run})}
1812 Use the @code{run} command to start your program under @value{GDBN}.
1813 You must first specify the program name (except on VxWorks) with an
1814 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1815 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1816 (@pxref{Files, ,Commands to specify files}).
1820 If you are running your program in an execution environment that
1821 supports processes, @code{run} creates an inferior process and makes
1822 that process run your program. (In environments without processes,
1823 @code{run} jumps to the start of your program.)
1825 The execution of a program is affected by certain information it
1826 receives from its superior. @value{GDBN} provides ways to specify this
1827 information, which you must do @emph{before} starting your program. (You
1828 can change it after starting your program, but such changes only affect
1829 your program the next time you start it.) This information may be
1830 divided into four categories:
1833 @item The @emph{arguments.}
1834 Specify the arguments to give your program as the arguments of the
1835 @code{run} command. If a shell is available on your target, the shell
1836 is used to pass the arguments, so that you may use normal conventions
1837 (such as wildcard expansion or variable substitution) in describing
1839 In Unix systems, you can control which shell is used with the
1840 @code{SHELL} environment variable.
1841 @xref{Arguments, ,Your program's arguments}.
1843 @item The @emph{environment.}
1844 Your program normally inherits its environment from @value{GDBN}, but you can
1845 use the @value{GDBN} commands @code{set environment} and @code{unset
1846 environment} to change parts of the environment that affect
1847 your program. @xref{Environment, ,Your program's environment}.
1849 @item The @emph{working directory.}
1850 Your program inherits its working directory from @value{GDBN}. You can set
1851 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1852 @xref{Working Directory, ,Your program's working directory}.
1854 @item The @emph{standard input and output.}
1855 Your program normally uses the same device for standard input and
1856 standard output as @value{GDBN} is using. You can redirect input and output
1857 in the @code{run} command line, or you can use the @code{tty} command to
1858 set a different device for your program.
1859 @xref{Input/Output, ,Your program's input and output}.
1862 @emph{Warning:} While input and output redirection work, you cannot use
1863 pipes to pass the output of the program you are debugging to another
1864 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1868 When you issue the @code{run} command, your program begins to execute
1869 immediately. @xref{Stopping, ,Stopping and continuing}, for discussion
1870 of how to arrange for your program to stop. Once your program has
1871 stopped, you may call functions in your program, using the @code{print}
1872 or @code{call} commands. @xref{Data, ,Examining Data}.
1874 If the modification time of your symbol file has changed since the last
1875 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1876 table, and reads it again. When it does this, @value{GDBN} tries to retain
1877 your current breakpoints.
1882 @cindex run to main procedure
1883 The name of the main procedure can vary from language to language.
1884 With C or C@t{++}, the main procedure name is always @code{main}, but
1885 other languages such as Ada do not require a specific name for their
1886 main procedure. The debugger provides a convenient way to start the
1887 execution of the program and to stop at the beginning of the main
1888 procedure, depending on the language used.
1890 The @samp{start} command does the equivalent of setting a temporary
1891 breakpoint at the beginning of the main procedure and then invoking
1892 the @samp{run} command.
1894 @cindex elaboration phase
1895 Some programs contain an @dfn{elaboration} phase where some startup code is
1896 executed before the main procedure is called. This depends on the
1897 languages used to write your program. In C@t{++}, for instance,
1898 constructors for static and global objects are executed before
1899 @code{main} is called. It is therefore possible that the debugger stops
1900 before reaching the main procedure. However, the temporary breakpoint
1901 will remain to halt execution.
1903 Specify the arguments to give to your program as arguments to the
1904 @samp{start} command. These arguments will be given verbatim to the
1905 underlying @samp{run} command. Note that the same arguments will be
1906 reused if no argument is provided during subsequent calls to
1907 @samp{start} or @samp{run}.
1909 It is sometimes necessary to debug the program during elaboration. In
1910 these cases, using the @code{start} command would stop the execution of
1911 your program too late, as the program would have already completed the
1912 elaboration phase. Under these circumstances, insert breakpoints in your
1913 elaboration code before running your program.
1917 @section Your program's arguments
1919 @cindex arguments (to your program)
1920 The arguments to your program can be specified by the arguments of the
1922 They are passed to a shell, which expands wildcard characters and
1923 performs redirection of I/O, and thence to your program. Your
1924 @code{SHELL} environment variable (if it exists) specifies what shell
1925 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1926 the default shell (@file{/bin/sh} on Unix).
1928 On non-Unix systems, the program is usually invoked directly by
1929 @value{GDBN}, which emulates I/O redirection via the appropriate system
1930 calls, and the wildcard characters are expanded by the startup code of
1931 the program, not by the shell.
1933 @code{run} with no arguments uses the same arguments used by the previous
1934 @code{run}, or those set by the @code{set args} command.
1939 Specify the arguments to be used the next time your program is run. If
1940 @code{set args} has no arguments, @code{run} executes your program
1941 with no arguments. Once you have run your program with arguments,
1942 using @code{set args} before the next @code{run} is the only way to run
1943 it again without arguments.
1947 Show the arguments to give your program when it is started.
1951 @section Your program's environment
1953 @cindex environment (of your program)
1954 The @dfn{environment} consists of a set of environment variables and
1955 their values. Environment variables conventionally record such things as
1956 your user name, your home directory, your terminal type, and your search
1957 path for programs to run. Usually you set up environment variables with
1958 the shell and they are inherited by all the other programs you run. When
1959 debugging, it can be useful to try running your program with a modified
1960 environment without having to start @value{GDBN} over again.
1964 @item path @var{directory}
1965 Add @var{directory} to the front of the @code{PATH} environment variable
1966 (the search path for executables) that will be passed to your program.
1967 The value of @code{PATH} used by @value{GDBN} does not change.
1968 You may specify several directory names, separated by whitespace or by a
1969 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1970 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1971 is moved to the front, so it is searched sooner.
1973 You can use the string @samp{$cwd} to refer to whatever is the current
1974 working directory at the time @value{GDBN} searches the path. If you
1975 use @samp{.} instead, it refers to the directory where you executed the
1976 @code{path} command. @value{GDBN} replaces @samp{.} in the
1977 @var{directory} argument (with the current path) before adding
1978 @var{directory} to the search path.
1979 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1980 @c document that, since repeating it would be a no-op.
1984 Display the list of search paths for executables (the @code{PATH}
1985 environment variable).
1987 @kindex show environment
1988 @item show environment @r{[}@var{varname}@r{]}
1989 Print the value of environment variable @var{varname} to be given to
1990 your program when it starts. If you do not supply @var{varname},
1991 print the names and values of all environment variables to be given to
1992 your program. You can abbreviate @code{environment} as @code{env}.
1994 @kindex set environment
1995 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1996 Set environment variable @var{varname} to @var{value}. The value
1997 changes for your program only, not for @value{GDBN} itself. @var{value} may
1998 be any string; the values of environment variables are just strings, and
1999 any interpretation is supplied by your program itself. The @var{value}
2000 parameter is optional; if it is eliminated, the variable is set to a
2002 @c "any string" here does not include leading, trailing
2003 @c blanks. Gnu asks: does anyone care?
2005 For example, this command:
2012 tells the debugged program, when subsequently run, that its user is named
2013 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2014 are not actually required.)
2016 @kindex unset environment
2017 @item unset environment @var{varname}
2018 Remove variable @var{varname} from the environment to be passed to your
2019 program. This is different from @samp{set env @var{varname} =};
2020 @code{unset environment} removes the variable from the environment,
2021 rather than assigning it an empty value.
2024 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2026 by your @code{SHELL} environment variable if it exists (or
2027 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2028 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2029 @file{.bashrc} for BASH---any variables you set in that file affect
2030 your program. You may wish to move setting of environment variables to
2031 files that are only run when you sign on, such as @file{.login} or
2034 @node Working Directory
2035 @section Your program's working directory
2037 @cindex working directory (of your program)
2038 Each time you start your program with @code{run}, it inherits its
2039 working directory from the current working directory of @value{GDBN}.
2040 The @value{GDBN} working directory is initially whatever it inherited
2041 from its parent process (typically the shell), but you can specify a new
2042 working directory in @value{GDBN} with the @code{cd} command.
2044 The @value{GDBN} working directory also serves as a default for the commands
2045 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2050 @cindex change working directory
2051 @item cd @var{directory}
2052 Set the @value{GDBN} working directory to @var{directory}.
2056 Print the @value{GDBN} working directory.
2059 It is generally impossible to find the current working directory of
2060 the process being debugged (since a program can change its directory
2061 during its run). If you work on a system where @value{GDBN} is
2062 configured with the @file{/proc} support, you can use the @code{info
2063 proc} command (@pxref{SVR4 Process Information}) to find out the
2064 current working directory of the debuggee.
2067 @section Your program's input and output
2072 By default, the program you run under @value{GDBN} does input and output to
2073 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2074 to its own terminal modes to interact with you, but it records the terminal
2075 modes your program was using and switches back to them when you continue
2076 running your program.
2079 @kindex info terminal
2081 Displays information recorded by @value{GDBN} about the terminal modes your
2085 You can redirect your program's input and/or output using shell
2086 redirection with the @code{run} command. For example,
2093 starts your program, diverting its output to the file @file{outfile}.
2096 @cindex controlling terminal
2097 Another way to specify where your program should do input and output is
2098 with the @code{tty} command. This command accepts a file name as
2099 argument, and causes this file to be the default for future @code{run}
2100 commands. It also resets the controlling terminal for the child
2101 process, for future @code{run} commands. For example,
2108 directs that processes started with subsequent @code{run} commands
2109 default to do input and output on the terminal @file{/dev/ttyb} and have
2110 that as their controlling terminal.
2112 An explicit redirection in @code{run} overrides the @code{tty} command's
2113 effect on the input/output device, but not its effect on the controlling
2116 When you use the @code{tty} command or redirect input in the @code{run}
2117 command, only the input @emph{for your program} is affected. The input
2118 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2119 for @code{set inferior-tty}.
2121 @cindex inferior tty
2122 @cindex set inferior controlling terminal
2123 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2124 display the name of the terminal that will be used for future runs of your
2128 @item set inferior-tty /dev/ttyb
2129 @kindex set inferior-tty
2130 Set the tty for the program being debugged to /dev/ttyb.
2132 @item show inferior-tty
2133 @kindex show inferior-tty
2134 Show the current tty for the program being debugged.
2138 @section Debugging an already-running process
2143 @item attach @var{process-id}
2144 This command attaches to a running process---one that was started
2145 outside @value{GDBN}. (@code{info files} shows your active
2146 targets.) The command takes as argument a process ID. The usual way to
2147 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2148 or with the @samp{jobs -l} shell command.
2150 @code{attach} does not repeat if you press @key{RET} a second time after
2151 executing the command.
2154 To use @code{attach}, your program must be running in an environment
2155 which supports processes; for example, @code{attach} does not work for
2156 programs on bare-board targets that lack an operating system. You must
2157 also have permission to send the process a signal.
2159 When you use @code{attach}, the debugger finds the program running in
2160 the process first by looking in the current working directory, then (if
2161 the program is not found) by using the source file search path
2162 (@pxref{Source Path, ,Specifying source directories}). You can also use
2163 the @code{file} command to load the program. @xref{Files, ,Commands to
2166 The first thing @value{GDBN} does after arranging to debug the specified
2167 process is to stop it. You can examine and modify an attached process
2168 with all the @value{GDBN} commands that are ordinarily available when
2169 you start processes with @code{run}. You can insert breakpoints; you
2170 can step and continue; you can modify storage. If you would rather the
2171 process continue running, you may use the @code{continue} command after
2172 attaching @value{GDBN} to the process.
2177 When you have finished debugging the attached process, you can use the
2178 @code{detach} command to release it from @value{GDBN} control. Detaching
2179 the process continues its execution. After the @code{detach} command,
2180 that process and @value{GDBN} become completely independent once more, and you
2181 are ready to @code{attach} another process or start one with @code{run}.
2182 @code{detach} does not repeat if you press @key{RET} again after
2183 executing the command.
2186 If you exit @value{GDBN} or use the @code{run} command while you have an
2187 attached process, you kill that process. By default, @value{GDBN} asks
2188 for confirmation if you try to do either of these things; you can
2189 control whether or not you need to confirm by using the @code{set
2190 confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
2194 @section Killing the child process
2199 Kill the child process in which your program is running under @value{GDBN}.
2202 This command is useful if you wish to debug a core dump instead of a
2203 running process. @value{GDBN} ignores any core dump file while your program
2206 On some operating systems, a program cannot be executed outside @value{GDBN}
2207 while you have breakpoints set on it inside @value{GDBN}. You can use the
2208 @code{kill} command in this situation to permit running your program
2209 outside the debugger.
2211 The @code{kill} command is also useful if you wish to recompile and
2212 relink your program, since on many systems it is impossible to modify an
2213 executable file while it is running in a process. In this case, when you
2214 next type @code{run}, @value{GDBN} notices that the file has changed, and
2215 reads the symbol table again (while trying to preserve your current
2216 breakpoint settings).
2219 @section Debugging programs with multiple threads
2221 @cindex threads of execution
2222 @cindex multiple threads
2223 @cindex switching threads
2224 In some operating systems, such as HP-UX and Solaris, a single program
2225 may have more than one @dfn{thread} of execution. The precise semantics
2226 of threads differ from one operating system to another, but in general
2227 the threads of a single program are akin to multiple processes---except
2228 that they share one address space (that is, they can all examine and
2229 modify the same variables). On the other hand, each thread has its own
2230 registers and execution stack, and perhaps private memory.
2232 @value{GDBN} provides these facilities for debugging multi-thread
2236 @item automatic notification of new threads
2237 @item @samp{thread @var{threadno}}, a command to switch among threads
2238 @item @samp{info threads}, a command to inquire about existing threads
2239 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2240 a command to apply a command to a list of threads
2241 @item thread-specific breakpoints
2245 @emph{Warning:} These facilities are not yet available on every
2246 @value{GDBN} configuration where the operating system supports threads.
2247 If your @value{GDBN} does not support threads, these commands have no
2248 effect. For example, a system without thread support shows no output
2249 from @samp{info threads}, and always rejects the @code{thread} command,
2253 (@value{GDBP}) info threads
2254 (@value{GDBP}) thread 1
2255 Thread ID 1 not known. Use the "info threads" command to
2256 see the IDs of currently known threads.
2258 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2259 @c doesn't support threads"?
2262 @cindex focus of debugging
2263 @cindex current thread
2264 The @value{GDBN} thread debugging facility allows you to observe all
2265 threads while your program runs---but whenever @value{GDBN} takes
2266 control, one thread in particular is always the focus of debugging.
2267 This thread is called the @dfn{current thread}. Debugging commands show
2268 program information from the perspective of the current thread.
2270 @cindex @code{New} @var{systag} message
2271 @cindex thread identifier (system)
2272 @c FIXME-implementors!! It would be more helpful if the [New...] message
2273 @c included GDB's numeric thread handle, so you could just go to that
2274 @c thread without first checking `info threads'.
2275 Whenever @value{GDBN} detects a new thread in your program, it displays
2276 the target system's identification for the thread with a message in the
2277 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2278 whose form varies depending on the particular system. For example, on
2279 LynxOS, you might see
2282 [New process 35 thread 27]
2286 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2287 the @var{systag} is simply something like @samp{process 368}, with no
2290 @c FIXME!! (1) Does the [New...] message appear even for the very first
2291 @c thread of a program, or does it only appear for the
2292 @c second---i.e.@: when it becomes obvious we have a multithread
2294 @c (2) *Is* there necessarily a first thread always? Or do some
2295 @c multithread systems permit starting a program with multiple
2296 @c threads ab initio?
2298 @cindex thread number
2299 @cindex thread identifier (GDB)
2300 For debugging purposes, @value{GDBN} associates its own thread
2301 number---always a single integer---with each thread in your program.
2304 @kindex info threads
2306 Display a summary of all threads currently in your
2307 program. @value{GDBN} displays for each thread (in this order):
2311 the thread number assigned by @value{GDBN}
2314 the target system's thread identifier (@var{systag})
2317 the current stack frame summary for that thread
2321 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2322 indicates the current thread.
2326 @c end table here to get a little more width for example
2329 (@value{GDBP}) info threads
2330 3 process 35 thread 27 0x34e5 in sigpause ()
2331 2 process 35 thread 23 0x34e5 in sigpause ()
2332 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2338 @cindex debugging multithreaded programs (on HP-UX)
2339 @cindex thread identifier (GDB), on HP-UX
2340 For debugging purposes, @value{GDBN} associates its own thread
2341 number---a small integer assigned in thread-creation order---with each
2342 thread in your program.
2344 @cindex @code{New} @var{systag} message, on HP-UX
2345 @cindex thread identifier (system), on HP-UX
2346 @c FIXME-implementors!! It would be more helpful if the [New...] message
2347 @c included GDB's numeric thread handle, so you could just go to that
2348 @c thread without first checking `info threads'.
2349 Whenever @value{GDBN} detects a new thread in your program, it displays
2350 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2351 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2352 whose form varies depending on the particular system. For example, on
2356 [New thread 2 (system thread 26594)]
2360 when @value{GDBN} notices a new thread.
2363 @kindex info threads (HP-UX)
2365 Display a summary of all threads currently in your
2366 program. @value{GDBN} displays for each thread (in this order):
2369 @item the thread number assigned by @value{GDBN}
2371 @item the target system's thread identifier (@var{systag})
2373 @item the current stack frame summary for that thread
2377 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2378 indicates the current thread.
2382 @c end table here to get a little more width for example
2385 (@value{GDBP}) info threads
2386 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2388 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2389 from /usr/lib/libc.2
2390 1 system thread 27905 0x7b003498 in _brk () \@*
2391 from /usr/lib/libc.2
2394 On Solaris, you can display more information about user threads with a
2395 Solaris-specific command:
2398 @item maint info sol-threads
2399 @kindex maint info sol-threads
2400 @cindex thread info (Solaris)
2401 Display info on Solaris user threads.
2405 @kindex thread @var{threadno}
2406 @item thread @var{threadno}
2407 Make thread number @var{threadno} the current thread. The command
2408 argument @var{threadno} is the internal @value{GDBN} thread number, as
2409 shown in the first field of the @samp{info threads} display.
2410 @value{GDBN} responds by displaying the system identifier of the thread
2411 you selected, and its current stack frame summary:
2414 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2415 (@value{GDBP}) thread 2
2416 [Switching to process 35 thread 23]
2417 0x34e5 in sigpause ()
2421 As with the @samp{[New @dots{}]} message, the form of the text after
2422 @samp{Switching to} depends on your system's conventions for identifying
2425 @kindex thread apply
2426 @cindex apply command to several threads
2427 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2428 The @code{thread apply} command allows you to apply the named
2429 @var{command} to one or more threads. Specify the numbers of the
2430 threads that you want affected with the command argument
2431 @var{threadno}. It can be a single thread number, one of the numbers
2432 shown in the first field of the @samp{info threads} display; or it
2433 could be a range of thread numbers, as in @code{2-4}. To apply a
2434 command to all threads, type @kbd{thread apply all @var{command}}.
2437 @cindex automatic thread selection
2438 @cindex switching threads automatically
2439 @cindex threads, automatic switching
2440 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2441 signal, it automatically selects the thread where that breakpoint or
2442 signal happened. @value{GDBN} alerts you to the context switch with a
2443 message of the form @samp{[Switching to @var{systag}]} to identify the
2446 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2447 more information about how @value{GDBN} behaves when you stop and start
2448 programs with multiple threads.
2450 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2451 watchpoints in programs with multiple threads.
2454 @section Debugging programs with multiple processes
2456 @cindex fork, debugging programs which call
2457 @cindex multiple processes
2458 @cindex processes, multiple
2459 On most systems, @value{GDBN} has no special support for debugging
2460 programs which create additional processes using the @code{fork}
2461 function. When a program forks, @value{GDBN} will continue to debug the
2462 parent process and the child process will run unimpeded. If you have
2463 set a breakpoint in any code which the child then executes, the child
2464 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2465 will cause it to terminate.
2467 However, if you want to debug the child process there is a workaround
2468 which isn't too painful. Put a call to @code{sleep} in the code which
2469 the child process executes after the fork. It may be useful to sleep
2470 only if a certain environment variable is set, or a certain file exists,
2471 so that the delay need not occur when you don't want to run @value{GDBN}
2472 on the child. While the child is sleeping, use the @code{ps} program to
2473 get its process ID. Then tell @value{GDBN} (a new invocation of
2474 @value{GDBN} if you are also debugging the parent process) to attach to
2475 the child process (@pxref{Attach}). From that point on you can debug
2476 the child process just like any other process which you attached to.
2478 On some systems, @value{GDBN} provides support for debugging programs that
2479 create additional processes using the @code{fork} or @code{vfork} functions.
2480 Currently, the only platforms with this feature are HP-UX (11.x and later
2481 only?) and GNU/Linux (kernel version 2.5.60 and later).
2483 By default, when a program forks, @value{GDBN} will continue to debug
2484 the parent process and the child process will run unimpeded.
2486 If you want to follow the child process instead of the parent process,
2487 use the command @w{@code{set follow-fork-mode}}.
2490 @kindex set follow-fork-mode
2491 @item set follow-fork-mode @var{mode}
2492 Set the debugger response to a program call of @code{fork} or
2493 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2494 process. The @var{mode} argument can be:
2498 The original process is debugged after a fork. The child process runs
2499 unimpeded. This is the default.
2502 The new process is debugged after a fork. The parent process runs
2507 @kindex show follow-fork-mode
2508 @item show follow-fork-mode
2509 Display the current debugger response to a @code{fork} or @code{vfork} call.
2512 @cindex debugging multiple processes
2513 On Linux, if you want to debug both the parent and child processes, use the
2514 command @w{@code{set detach-on-fork}}.
2517 @kindex set detach-on-fork
2518 @item set detach-on-fork @var{mode}
2519 Tells gdb whether to detach one of the processes after a fork, or
2520 retain debugger control over them both.
2524 The child process (or parent process, depending on the value of
2525 @code{follow-fork-mode}) will be detached and allowed to run
2526 independently. This is the default.
2529 Both processes will be held under the control of @value{GDBN}.
2530 One process (child or parent, depending on the value of
2531 @code{follow-fork-mode}) is debugged as usual, while the other
2536 @kindex show detach-on-follow
2537 @item show detach-on-follow
2538 Show whether detach-on-follow mode is on/off.
2541 If you choose to set @var{detach-on-follow} mode off, then
2542 @value{GDBN} will retain control of all forked processes (including
2543 nested forks). You can list the forked processes under the control of
2544 @value{GDBN} by using the @w{@code{info forks}} command, and switch
2545 from one fork to another by using the @w{@code{fork}} command.
2550 Print a list of all forked processes under the control of @value{GDBN}.
2551 The listing will include a fork id, a process id, and the current
2552 position (program counter) of the process.
2555 @kindex fork @var{fork-id}
2556 @item fork @var{fork-id}
2557 Make fork number @var{fork-id} the current process. The argument
2558 @var{fork-id} is the internal fork number assigned by @value{GDBN},
2559 as shown in the first field of the @samp{info forks} display.
2563 To quit debugging one of the forked processes, you can either detach
2564 from it by using the @w{@code{detach-fork}} command (allowing it to
2565 run independently), or delete (and kill) it using the
2566 @w{@code{delete-fork}} command.
2569 @kindex detach-fork @var{fork-id}
2570 @item detach-fork @var{fork-id}
2571 Detach from the process identified by @value{GDBN} fork number
2572 @var{fork-id}, and remove it from the fork list. The process will be
2573 allowed to run independently.
2575 @kindex delete-fork @var{fork-id}
2576 @item delete-fork @var{fork-id}
2577 Kill the process identified by @value{GDBN} fork number @var{fork-id},
2578 and remove it from the fork list.
2582 If you ask to debug a child process and a @code{vfork} is followed by an
2583 @code{exec}, @value{GDBN} executes the new target up to the first
2584 breakpoint in the new target. If you have a breakpoint set on
2585 @code{main} in your original program, the breakpoint will also be set on
2586 the child process's @code{main}.
2588 When a child process is spawned by @code{vfork}, you cannot debug the
2589 child or parent until an @code{exec} call completes.
2591 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2592 call executes, the new target restarts. To restart the parent process,
2593 use the @code{file} command with the parent executable name as its
2596 You can use the @code{catch} command to make @value{GDBN} stop whenever
2597 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2598 Catchpoints, ,Setting catchpoints}.
2600 @node Checkpoint/Restart
2601 @section Setting a @emph{bookmark} to return to later
2606 @cindex snapshot of a process
2607 @cindex rewind program state
2609 On certain operating systems@footnote{Currently, only
2610 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
2611 program's state, called a @dfn{checkpoint}, and come back to it
2614 Returning to a checkpoint effectively undoes everything that has
2615 happened in the program since the @code{checkpoint} was saved. This
2616 includes changes in memory, registers, and even (within some limits)
2617 system state. Effectively, it is like going back in time to the
2618 moment when the checkpoint was saved.
2620 Thus, if you're stepping thru a program and you think you're
2621 getting close to the point where things go wrong, you can save
2622 a checkpoint. Then, if you accidentally go too far and miss
2623 the critical statement, instead of having to restart your program
2624 from the beginning, you can just go back to the checkpoint and
2625 start again from there.
2627 This can be especially useful if it takes a lot of time or
2628 steps to reach the point where you think the bug occurs.
2630 To use the @code{checkpoint}/@code{restart} method of debugging:
2635 Save a snapshot of the debugged program's current execution state.
2636 The @code{checkpoint} command takes no arguments, but each checkpoint
2637 is assigned a small integer id, similar to a breakpoint id.
2639 @kindex info checkpoints
2640 @item info checkpoints
2641 List the checkpoints that have been saved in the current debugging
2642 session. For each checkpoint, the following information will be
2649 @item Source line, or label
2652 @kindex restart @var{checkpoint-id}
2653 @item restart @var{checkpoint-id}
2654 Restore the program state that was saved as checkpoint number
2655 @var{checkpoint-id}. All program variables, registers, stack frames
2656 etc.@: will be returned to the values that they had when the checkpoint
2657 was saved. In essence, gdb will ``wind back the clock'' to the point
2658 in time when the checkpoint was saved.
2660 Note that breakpoints, @value{GDBN} variables, command history etc.
2661 are not affected by restoring a checkpoint. In general, a checkpoint
2662 only restores things that reside in the program being debugged, not in
2665 @kindex delete-checkpoint @var{checkpoint-id}
2666 @item delete-checkpoint @var{checkpoint-id}
2667 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
2671 Returning to a previously saved checkpoint will restore the user state
2672 of the program being debugged, plus a significant subset of the system
2673 (OS) state, including file pointers. It won't ``un-write'' data from
2674 a file, but it will rewind the file pointer to the previous location,
2675 so that the previously written data can be overwritten. For files
2676 opened in read mode, the pointer will also be restored so that the
2677 previously read data can be read again.
2679 Of course, characters that have been sent to a printer (or other
2680 external device) cannot be ``snatched back'', and characters received
2681 from eg.@: a serial device can be removed from internal program buffers,
2682 but they cannot be ``pushed back'' into the serial pipeline, ready to
2683 be received again. Similarly, the actual contents of files that have
2684 been changed cannot be restored (at this time).
2686 However, within those constraints, you actually can ``rewind'' your
2687 program to a previously saved point in time, and begin debugging it
2688 again --- and you can change the course of events so as to debug a
2689 different execution path this time.
2691 @cindex checkpoints and process id
2692 Finally, there is one bit of internal program state that will be
2693 different when you return to a checkpoint --- the program's process
2694 id. Each checkpoint will have a unique process id (or @var{pid}),
2695 and each will be different from the program's original @var{pid}.
2696 If your program has saved a local copy of its process id, this could
2697 potentially pose a problem.
2699 @subsection A non-obvious benefit of using checkpoints
2701 On some systems such as @sc{gnu}/Linux, address space randomization
2702 is performed on new processes for security reasons. This makes it
2703 difficult or impossible to set a breakpoint, or watchpoint, on an
2704 absolute address if you have to restart the program, since the
2705 absolute location of a symbol will change from one execution to the
2708 A checkpoint, however, is an @emph{identical} copy of a process.
2709 Therefore if you create a checkpoint at (eg.@:) the start of main,
2710 and simply return to that checkpoint instead of restarting the
2711 process, you can avoid the effects of address randomization and
2712 your symbols will all stay in the same place.
2715 @chapter Stopping and Continuing
2717 The principal purposes of using a debugger are so that you can stop your
2718 program before it terminates; or so that, if your program runs into
2719 trouble, you can investigate and find out why.
2721 Inside @value{GDBN}, your program may stop for any of several reasons,
2722 such as a signal, a breakpoint, or reaching a new line after a
2723 @value{GDBN} command such as @code{step}. You may then examine and
2724 change variables, set new breakpoints or remove old ones, and then
2725 continue execution. Usually, the messages shown by @value{GDBN} provide
2726 ample explanation of the status of your program---but you can also
2727 explicitly request this information at any time.
2730 @kindex info program
2732 Display information about the status of your program: whether it is
2733 running or not, what process it is, and why it stopped.
2737 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2738 * Continuing and Stepping:: Resuming execution
2740 * Thread Stops:: Stopping and starting multi-thread programs
2744 @section Breakpoints, watchpoints, and catchpoints
2747 A @dfn{breakpoint} makes your program stop whenever a certain point in
2748 the program is reached. For each breakpoint, you can add conditions to
2749 control in finer detail whether your program stops. You can set
2750 breakpoints with the @code{break} command and its variants (@pxref{Set
2751 Breaks, ,Setting breakpoints}), to specify the place where your program
2752 should stop by line number, function name or exact address in the
2755 On some systems, you can set breakpoints in shared libraries before
2756 the executable is run. There is a minor limitation on HP-UX systems:
2757 you must wait until the executable is run in order to set breakpoints
2758 in shared library routines that are not called directly by the program
2759 (for example, routines that are arguments in a @code{pthread_create}
2763 @cindex memory tracing
2764 @cindex breakpoint on memory address
2765 @cindex breakpoint on variable modification
2766 A @dfn{watchpoint} is a special breakpoint that stops your program
2767 when the value of an expression changes. You must use a different
2768 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
2769 watchpoints}), but aside from that, you can manage a watchpoint like
2770 any other breakpoint: you enable, disable, and delete both breakpoints
2771 and watchpoints using the same commands.
2773 You can arrange to have values from your program displayed automatically
2774 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2778 @cindex breakpoint on events
2779 A @dfn{catchpoint} is another special breakpoint that stops your program
2780 when a certain kind of event occurs, such as the throwing of a C@t{++}
2781 exception or the loading of a library. As with watchpoints, you use a
2782 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2783 catchpoints}), but aside from that, you can manage a catchpoint like any
2784 other breakpoint. (To stop when your program receives a signal, use the
2785 @code{handle} command; see @ref{Signals, ,Signals}.)
2787 @cindex breakpoint numbers
2788 @cindex numbers for breakpoints
2789 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2790 catchpoint when you create it; these numbers are successive integers
2791 starting with one. In many of the commands for controlling various
2792 features of breakpoints you use the breakpoint number to say which
2793 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2794 @dfn{disabled}; if disabled, it has no effect on your program until you
2797 @cindex breakpoint ranges
2798 @cindex ranges of breakpoints
2799 Some @value{GDBN} commands accept a range of breakpoints on which to
2800 operate. A breakpoint range is either a single breakpoint number, like
2801 @samp{5}, or two such numbers, in increasing order, separated by a
2802 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2803 all breakpoint in that range are operated on.
2806 * Set Breaks:: Setting breakpoints
2807 * Set Watchpoints:: Setting watchpoints
2808 * Set Catchpoints:: Setting catchpoints
2809 * Delete Breaks:: Deleting breakpoints
2810 * Disabling:: Disabling breakpoints
2811 * Conditions:: Break conditions
2812 * Break Commands:: Breakpoint command lists
2813 * Breakpoint Menus:: Breakpoint menus
2814 * Error in Breakpoints:: ``Cannot insert breakpoints''
2815 * Breakpoint related warnings:: ``Breakpoint address adjusted...''
2819 @subsection Setting breakpoints
2821 @c FIXME LMB what does GDB do if no code on line of breakpt?
2822 @c consider in particular declaration with/without initialization.
2824 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2827 @kindex b @r{(@code{break})}
2828 @vindex $bpnum@r{, convenience variable}
2829 @cindex latest breakpoint
2830 Breakpoints are set with the @code{break} command (abbreviated
2831 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2832 number of the breakpoint you've set most recently; see @ref{Convenience
2833 Vars,, Convenience variables}, for a discussion of what you can do with
2834 convenience variables.
2836 You have several ways to say where the breakpoint should go.
2839 @item break @var{function}
2840 Set a breakpoint at entry to function @var{function}.
2841 When using source languages that permit overloading of symbols, such as
2842 C@t{++}, @var{function} may refer to more than one possible place to break.
2843 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2845 @item break +@var{offset}
2846 @itemx break -@var{offset}
2847 Set a breakpoint some number of lines forward or back from the position
2848 at which execution stopped in the currently selected @dfn{stack frame}.
2849 (@xref{Frames, ,Frames}, for a description of stack frames.)
2851 @item break @var{linenum}
2852 Set a breakpoint at line @var{linenum} in the current source file.
2853 The current source file is the last file whose source text was printed.
2854 The breakpoint will stop your program just before it executes any of the
2857 @item break @var{filename}:@var{linenum}
2858 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2860 @item break @var{filename}:@var{function}
2861 Set a breakpoint at entry to function @var{function} found in file
2862 @var{filename}. Specifying a file name as well as a function name is
2863 superfluous except when multiple files contain similarly named
2866 @item break *@var{address}
2867 Set a breakpoint at address @var{address}. You can use this to set
2868 breakpoints in parts of your program which do not have debugging
2869 information or source files.
2872 When called without any arguments, @code{break} sets a breakpoint at
2873 the next instruction to be executed in the selected stack frame
2874 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2875 innermost, this makes your program stop as soon as control
2876 returns to that frame. This is similar to the effect of a
2877 @code{finish} command in the frame inside the selected frame---except
2878 that @code{finish} does not leave an active breakpoint. If you use
2879 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2880 the next time it reaches the current location; this may be useful
2883 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2884 least one instruction has been executed. If it did not do this, you
2885 would be unable to proceed past a breakpoint without first disabling the
2886 breakpoint. This rule applies whether or not the breakpoint already
2887 existed when your program stopped.
2889 @item break @dots{} if @var{cond}
2890 Set a breakpoint with condition @var{cond}; evaluate the expression
2891 @var{cond} each time the breakpoint is reached, and stop only if the
2892 value is nonzero---that is, if @var{cond} evaluates as true.
2893 @samp{@dots{}} stands for one of the possible arguments described
2894 above (or no argument) specifying where to break. @xref{Conditions,
2895 ,Break conditions}, for more information on breakpoint conditions.
2898 @item tbreak @var{args}
2899 Set a breakpoint enabled only for one stop. @var{args} are the
2900 same as for the @code{break} command, and the breakpoint is set in the same
2901 way, but the breakpoint is automatically deleted after the first time your
2902 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2905 @cindex hardware breakpoints
2906 @item hbreak @var{args}
2907 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2908 @code{break} command and the breakpoint is set in the same way, but the
2909 breakpoint requires hardware support and some target hardware may not
2910 have this support. The main purpose of this is EPROM/ROM code
2911 debugging, so you can set a breakpoint at an instruction without
2912 changing the instruction. This can be used with the new trap-generation
2913 provided by SPARClite DSU and most x86-based targets. These targets
2914 will generate traps when a program accesses some data or instruction
2915 address that is assigned to the debug registers. However the hardware
2916 breakpoint registers can take a limited number of breakpoints. For
2917 example, on the DSU, only two data breakpoints can be set at a time, and
2918 @value{GDBN} will reject this command if more than two are used. Delete
2919 or disable unused hardware breakpoints before setting new ones
2920 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2921 For remote targets, you can restrict the number of hardware
2922 breakpoints @value{GDBN} will use, see @ref{set remote
2923 hardware-breakpoint-limit}.
2927 @item thbreak @var{args}
2928 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2929 are the same as for the @code{hbreak} command and the breakpoint is set in
2930 the same way. However, like the @code{tbreak} command,
2931 the breakpoint is automatically deleted after the
2932 first time your program stops there. Also, like the @code{hbreak}
2933 command, the breakpoint requires hardware support and some target hardware
2934 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2935 See also @ref{Conditions, ,Break conditions}.
2938 @cindex regular expression
2939 @cindex breakpoints in functions matching a regexp
2940 @cindex set breakpoints in many functions
2941 @item rbreak @var{regex}
2942 Set breakpoints on all functions matching the regular expression
2943 @var{regex}. This command sets an unconditional breakpoint on all
2944 matches, printing a list of all breakpoints it set. Once these
2945 breakpoints are set, they are treated just like the breakpoints set with
2946 the @code{break} command. You can delete them, disable them, or make
2947 them conditional the same way as any other breakpoint.
2949 The syntax of the regular expression is the standard one used with tools
2950 like @file{grep}. Note that this is different from the syntax used by
2951 shells, so for instance @code{foo*} matches all functions that include
2952 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2953 @code{.*} leading and trailing the regular expression you supply, so to
2954 match only functions that begin with @code{foo}, use @code{^foo}.
2956 @cindex non-member C@t{++} functions, set breakpoint in
2957 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2958 breakpoints on overloaded functions that are not members of any special
2961 @cindex set breakpoints on all functions
2962 The @code{rbreak} command can be used to set breakpoints in
2963 @strong{all} the functions in a program, like this:
2966 (@value{GDBP}) rbreak .
2969 @kindex info breakpoints
2970 @cindex @code{$_} and @code{info breakpoints}
2971 @item info breakpoints @r{[}@var{n}@r{]}
2972 @itemx info break @r{[}@var{n}@r{]}
2973 @itemx info watchpoints @r{[}@var{n}@r{]}
2974 Print a table of all breakpoints, watchpoints, and catchpoints set and
2975 not deleted, with the following columns for each breakpoint:
2978 @item Breakpoint Numbers
2980 Breakpoint, watchpoint, or catchpoint.
2982 Whether the breakpoint is marked to be disabled or deleted when hit.
2983 @item Enabled or Disabled
2984 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2985 that are not enabled.
2987 Where the breakpoint is in your program, as a memory address. If the
2988 breakpoint is pending (see below for details) on a future load of a shared library, the address
2989 will be listed as @samp{<PENDING>}.
2991 Where the breakpoint is in the source for your program, as a file and
2992 line number. For a pending breakpoint, the original string passed to
2993 the breakpoint command will be listed as it cannot be resolved until
2994 the appropriate shared library is loaded in the future.
2998 If a breakpoint is conditional, @code{info break} shows the condition on
2999 the line following the affected breakpoint; breakpoint commands, if any,
3000 are listed after that. A pending breakpoint is allowed to have a condition
3001 specified for it. The condition is not parsed for validity until a shared
3002 library is loaded that allows the pending breakpoint to resolve to a
3006 @code{info break} with a breakpoint
3007 number @var{n} as argument lists only that breakpoint. The
3008 convenience variable @code{$_} and the default examining-address for
3009 the @code{x} command are set to the address of the last breakpoint
3010 listed (@pxref{Memory, ,Examining memory}).
3013 @code{info break} displays a count of the number of times the breakpoint
3014 has been hit. This is especially useful in conjunction with the
3015 @code{ignore} command. You can ignore a large number of breakpoint
3016 hits, look at the breakpoint info to see how many times the breakpoint
3017 was hit, and then run again, ignoring one less than that number. This
3018 will get you quickly to the last hit of that breakpoint.
3021 @value{GDBN} allows you to set any number of breakpoints at the same place in
3022 your program. There is nothing silly or meaningless about this. When
3023 the breakpoints are conditional, this is even useful
3024 (@pxref{Conditions, ,Break conditions}).
3026 @cindex pending breakpoints
3027 If a specified breakpoint location cannot be found, it may be due to the fact
3028 that the location is in a shared library that is yet to be loaded. In such
3029 a case, you may want @value{GDBN} to create a special breakpoint (known as
3030 a @dfn{pending breakpoint}) that
3031 attempts to resolve itself in the future when an appropriate shared library
3034 Pending breakpoints are useful to set at the start of your
3035 @value{GDBN} session for locations that you know will be dynamically loaded
3036 later by the program being debugged. When shared libraries are loaded,
3037 a check is made to see if the load resolves any pending breakpoint locations.
3038 If a pending breakpoint location gets resolved,
3039 a regular breakpoint is created and the original pending breakpoint is removed.
3041 @value{GDBN} provides some additional commands for controlling pending
3044 @kindex set breakpoint pending
3045 @kindex show breakpoint pending
3047 @item set breakpoint pending auto
3048 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3049 location, it queries you whether a pending breakpoint should be created.
3051 @item set breakpoint pending on
3052 This indicates that an unrecognized breakpoint location should automatically
3053 result in a pending breakpoint being created.
3055 @item set breakpoint pending off
3056 This indicates that pending breakpoints are not to be created. Any
3057 unrecognized breakpoint location results in an error. This setting does
3058 not affect any pending breakpoints previously created.
3060 @item show breakpoint pending
3061 Show the current behavior setting for creating pending breakpoints.
3064 @cindex operations allowed on pending breakpoints
3065 Normal breakpoint operations apply to pending breakpoints as well. You may
3066 specify a condition for a pending breakpoint and/or commands to run when the
3067 breakpoint is reached. You can also enable or disable
3068 the pending breakpoint. When you specify a condition for a pending breakpoint,
3069 the parsing of the condition will be deferred until the point where the
3070 pending breakpoint location is resolved. Disabling a pending breakpoint
3071 tells @value{GDBN} to not attempt to resolve the breakpoint on any subsequent
3072 shared library load. When a pending breakpoint is re-enabled,
3073 @value{GDBN} checks to see if the location is already resolved.
3074 This is done because any number of shared library loads could have
3075 occurred since the time the breakpoint was disabled and one or more
3076 of these loads could resolve the location.
3078 @cindex negative breakpoint numbers
3079 @cindex internal @value{GDBN} breakpoints
3080 @value{GDBN} itself sometimes sets breakpoints in your program for
3081 special purposes, such as proper handling of @code{longjmp} (in C
3082 programs). These internal breakpoints are assigned negative numbers,
3083 starting with @code{-1}; @samp{info breakpoints} does not display them.
3084 You can see these breakpoints with the @value{GDBN} maintenance command
3085 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3088 @node Set Watchpoints
3089 @subsection Setting watchpoints
3091 @cindex setting watchpoints
3092 You can use a watchpoint to stop execution whenever the value of an
3093 expression changes, without having to predict a particular place where
3096 @cindex software watchpoints
3097 @cindex hardware watchpoints
3098 Depending on your system, watchpoints may be implemented in software or
3099 hardware. @value{GDBN} does software watchpointing by single-stepping your
3100 program and testing the variable's value each time, which is hundreds of
3101 times slower than normal execution. (But this may still be worth it, to
3102 catch errors where you have no clue what part of your program is the
3105 On some systems, such as HP-UX, @sc{gnu}/Linux and most other
3106 x86-based targets, @value{GDBN} includes support for hardware
3107 watchpoints, which do not slow down the running of your program.
3111 @item watch @var{expr}
3112 Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
3113 is written into by the program and its value changes.
3116 @item rwatch @var{expr}
3117 Set a watchpoint that will break when the value of @var{expr} is read
3121 @item awatch @var{expr}
3122 Set a watchpoint that will break when @var{expr} is either read from
3123 or written into by the program.
3125 @kindex info watchpoints
3126 @item info watchpoints
3127 This command prints a list of watchpoints, breakpoints, and catchpoints;
3128 it is the same as @code{info break} (@pxref{Set Breaks}).
3131 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3132 watchpoints execute very quickly, and the debugger reports a change in
3133 value at the exact instruction where the change occurs. If @value{GDBN}
3134 cannot set a hardware watchpoint, it sets a software watchpoint, which
3135 executes more slowly and reports the change in value at the next
3136 @emph{statement}, not the instruction, after the change occurs.
3138 @cindex use only software watchpoints
3139 You can force @value{GDBN} to use only software watchpoints with the
3140 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3141 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3142 the underlying system supports them. (Note that hardware-assisted
3143 watchpoints that were set @emph{before} setting
3144 @code{can-use-hw-watchpoints} to zero will still use the hardware
3145 mechanism of watching expressiion values.)
3148 @item set can-use-hw-watchpoints
3149 @kindex set can-use-hw-watchpoints
3150 Set whether or not to use hardware watchpoints.
3152 @item show can-use-hw-watchpoints
3153 @kindex show can-use-hw-watchpoints
3154 Show the current mode of using hardware watchpoints.
3157 For remote targets, you can restrict the number of hardware
3158 watchpoints @value{GDBN} will use, see @ref{set remote
3159 hardware-breakpoint-limit}.
3161 When you issue the @code{watch} command, @value{GDBN} reports
3164 Hardware watchpoint @var{num}: @var{expr}
3168 if it was able to set a hardware watchpoint.
3170 Currently, the @code{awatch} and @code{rwatch} commands can only set
3171 hardware watchpoints, because accesses to data that don't change the
3172 value of the watched expression cannot be detected without examining
3173 every instruction as it is being executed, and @value{GDBN} does not do
3174 that currently. If @value{GDBN} finds that it is unable to set a
3175 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3176 will print a message like this:
3179 Expression cannot be implemented with read/access watchpoint.
3182 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3183 data type of the watched expression is wider than what a hardware
3184 watchpoint on the target machine can handle. For example, some systems
3185 can only watch regions that are up to 4 bytes wide; on such systems you
3186 cannot set hardware watchpoints for an expression that yields a
3187 double-precision floating-point number (which is typically 8 bytes
3188 wide). As a work-around, it might be possible to break the large region
3189 into a series of smaller ones and watch them with separate watchpoints.
3191 If you set too many hardware watchpoints, @value{GDBN} might be unable
3192 to insert all of them when you resume the execution of your program.
3193 Since the precise number of active watchpoints is unknown until such
3194 time as the program is about to be resumed, @value{GDBN} might not be
3195 able to warn you about this when you set the watchpoints, and the
3196 warning will be printed only when the program is resumed:
3199 Hardware watchpoint @var{num}: Could not insert watchpoint
3203 If this happens, delete or disable some of the watchpoints.
3205 The SPARClite DSU will generate traps when a program accesses some data
3206 or instruction address that is assigned to the debug registers. For the
3207 data addresses, DSU facilitates the @code{watch} command. However the
3208 hardware breakpoint registers can only take two data watchpoints, and
3209 both watchpoints must be the same kind. For example, you can set two
3210 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
3211 @strong{or} two with @code{awatch} commands, but you cannot set one
3212 watchpoint with one command and the other with a different command.
3213 @value{GDBN} will reject the command if you try to mix watchpoints.
3214 Delete or disable unused watchpoint commands before setting new ones.
3216 If you call a function interactively using @code{print} or @code{call},
3217 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3218 kind of breakpoint or the call completes.
3220 @value{GDBN} automatically deletes watchpoints that watch local
3221 (automatic) variables, or expressions that involve such variables, when
3222 they go out of scope, that is, when the execution leaves the block in
3223 which these variables were defined. In particular, when the program
3224 being debugged terminates, @emph{all} local variables go out of scope,
3225 and so only watchpoints that watch global variables remain set. If you
3226 rerun the program, you will need to set all such watchpoints again. One
3227 way of doing that would be to set a code breakpoint at the entry to the
3228 @code{main} function and when it breaks, set all the watchpoints.
3231 @cindex watchpoints and threads
3232 @cindex threads and watchpoints
3233 @emph{Warning:} In multi-thread programs, watchpoints have only limited
3234 usefulness. With the current watchpoint implementation, @value{GDBN}
3235 can only watch the value of an expression @emph{in a single thread}. If
3236 you are confident that the expression can only change due to the current
3237 thread's activity (and if you are also confident that no other thread
3238 can become current), then you can use watchpoints as usual. However,
3239 @value{GDBN} may not notice when a non-current thread's activity changes
3242 @c FIXME: this is almost identical to the previous paragraph.
3243 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
3244 have only limited usefulness. If @value{GDBN} creates a software
3245 watchpoint, it can only watch the value of an expression @emph{in a
3246 single thread}. If you are confident that the expression can only
3247 change due to the current thread's activity (and if you are also
3248 confident that no other thread can become current), then you can use
3249 software watchpoints as usual. However, @value{GDBN} may not notice
3250 when a non-current thread's activity changes the expression. (Hardware
3251 watchpoints, in contrast, watch an expression in all threads.)
3254 @xref{set remote hardware-watchpoint-limit}.
3256 @node Set Catchpoints
3257 @subsection Setting catchpoints
3258 @cindex catchpoints, setting
3259 @cindex exception handlers
3260 @cindex event handling
3262 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3263 kinds of program events, such as C@t{++} exceptions or the loading of a
3264 shared library. Use the @code{catch} command to set a catchpoint.
3268 @item catch @var{event}
3269 Stop when @var{event} occurs. @var{event} can be any of the following:
3272 @cindex stop on C@t{++} exceptions
3273 The throwing of a C@t{++} exception.
3276 The catching of a C@t{++} exception.
3279 @cindex break on fork/exec
3280 A call to @code{exec}. This is currently only available for HP-UX.
3283 A call to @code{fork}. This is currently only available for HP-UX.
3286 A call to @code{vfork}. This is currently only available for HP-UX.
3289 @itemx load @var{libname}
3290 @cindex break on load/unload of shared library
3291 The dynamic loading of any shared library, or the loading of the library
3292 @var{libname}. This is currently only available for HP-UX.
3295 @itemx unload @var{libname}
3296 The unloading of any dynamically loaded shared library, or the unloading
3297 of the library @var{libname}. This is currently only available for HP-UX.
3300 @item tcatch @var{event}
3301 Set a catchpoint that is enabled only for one stop. The catchpoint is
3302 automatically deleted after the first time the event is caught.
3306 Use the @code{info break} command to list the current catchpoints.
3308 There are currently some limitations to C@t{++} exception handling
3309 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3313 If you call a function interactively, @value{GDBN} normally returns
3314 control to you when the function has finished executing. If the call
3315 raises an exception, however, the call may bypass the mechanism that
3316 returns control to you and cause your program either to abort or to
3317 simply continue running until it hits a breakpoint, catches a signal
3318 that @value{GDBN} is listening for, or exits. This is the case even if
3319 you set a catchpoint for the exception; catchpoints on exceptions are
3320 disabled within interactive calls.
3323 You cannot raise an exception interactively.
3326 You cannot install an exception handler interactively.
3329 @cindex raise exceptions
3330 Sometimes @code{catch} is not the best way to debug exception handling:
3331 if you need to know exactly where an exception is raised, it is better to
3332 stop @emph{before} the exception handler is called, since that way you
3333 can see the stack before any unwinding takes place. If you set a
3334 breakpoint in an exception handler instead, it may not be easy to find
3335 out where the exception was raised.
3337 To stop just before an exception handler is called, you need some
3338 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3339 raised by calling a library function named @code{__raise_exception}
3340 which has the following ANSI C interface:
3343 /* @var{addr} is where the exception identifier is stored.
3344 @var{id} is the exception identifier. */
3345 void __raise_exception (void **addr, void *id);
3349 To make the debugger catch all exceptions before any stack
3350 unwinding takes place, set a breakpoint on @code{__raise_exception}
3351 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
3353 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
3354 that depends on the value of @var{id}, you can stop your program when
3355 a specific exception is raised. You can use multiple conditional
3356 breakpoints to stop your program when any of a number of exceptions are
3361 @subsection Deleting breakpoints
3363 @cindex clearing breakpoints, watchpoints, catchpoints
3364 @cindex deleting breakpoints, watchpoints, catchpoints
3365 It is often necessary to eliminate a breakpoint, watchpoint, or
3366 catchpoint once it has done its job and you no longer want your program
3367 to stop there. This is called @dfn{deleting} the breakpoint. A
3368 breakpoint that has been deleted no longer exists; it is forgotten.
3370 With the @code{clear} command you can delete breakpoints according to
3371 where they are in your program. With the @code{delete} command you can
3372 delete individual breakpoints, watchpoints, or catchpoints by specifying
3373 their breakpoint numbers.
3375 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3376 automatically ignores breakpoints on the first instruction to be executed
3377 when you continue execution without changing the execution address.
3382 Delete any breakpoints at the next instruction to be executed in the
3383 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
3384 the innermost frame is selected, this is a good way to delete a
3385 breakpoint where your program just stopped.
3387 @item clear @var{function}
3388 @itemx clear @var{filename}:@var{function}
3389 Delete any breakpoints set at entry to the named @var{function}.
3391 @item clear @var{linenum}
3392 @itemx clear @var{filename}:@var{linenum}
3393 Delete any breakpoints set at or within the code of the specified
3394 @var{linenum} of the specified @var{filename}.
3396 @cindex delete breakpoints
3398 @kindex d @r{(@code{delete})}
3399 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3400 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3401 ranges specified as arguments. If no argument is specified, delete all
3402 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3403 confirm off}). You can abbreviate this command as @code{d}.
3407 @subsection Disabling breakpoints
3409 @cindex enable/disable a breakpoint
3410 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3411 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3412 it had been deleted, but remembers the information on the breakpoint so
3413 that you can @dfn{enable} it again later.
3415 You disable and enable breakpoints, watchpoints, and catchpoints with
3416 the @code{enable} and @code{disable} commands, optionally specifying one
3417 or more breakpoint numbers as arguments. Use @code{info break} or
3418 @code{info watch} to print a list of breakpoints, watchpoints, and
3419 catchpoints if you do not know which numbers to use.
3421 A breakpoint, watchpoint, or catchpoint can have any of four different
3422 states of enablement:
3426 Enabled. The breakpoint stops your program. A breakpoint set
3427 with the @code{break} command starts out in this state.
3429 Disabled. The breakpoint has no effect on your program.
3431 Enabled once. The breakpoint stops your program, but then becomes
3434 Enabled for deletion. The breakpoint stops your program, but
3435 immediately after it does so it is deleted permanently. A breakpoint
3436 set with the @code{tbreak} command starts out in this state.
3439 You can use the following commands to enable or disable breakpoints,
3440 watchpoints, and catchpoints:
3444 @kindex dis @r{(@code{disable})}
3445 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3446 Disable the specified breakpoints---or all breakpoints, if none are
3447 listed. A disabled breakpoint has no effect but is not forgotten. All
3448 options such as ignore-counts, conditions and commands are remembered in
3449 case the breakpoint is enabled again later. You may abbreviate
3450 @code{disable} as @code{dis}.
3453 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3454 Enable the specified breakpoints (or all defined breakpoints). They
3455 become effective once again in stopping your program.
3457 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3458 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3459 of these breakpoints immediately after stopping your program.
3461 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3462 Enable the specified breakpoints to work once, then die. @value{GDBN}
3463 deletes any of these breakpoints as soon as your program stops there.
3464 Breakpoints set by the @code{tbreak} command start out in this state.
3467 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3468 @c confusing: tbreak is also initially enabled.
3469 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3470 ,Setting breakpoints}), breakpoints that you set are initially enabled;
3471 subsequently, they become disabled or enabled only when you use one of
3472 the commands above. (The command @code{until} can set and delete a
3473 breakpoint of its own, but it does not change the state of your other
3474 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3478 @subsection Break conditions
3479 @cindex conditional breakpoints
3480 @cindex breakpoint conditions
3482 @c FIXME what is scope of break condition expr? Context where wanted?
3483 @c in particular for a watchpoint?
3484 The simplest sort of breakpoint breaks every time your program reaches a
3485 specified place. You can also specify a @dfn{condition} for a
3486 breakpoint. A condition is just a Boolean expression in your
3487 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3488 a condition evaluates the expression each time your program reaches it,
3489 and your program stops only if the condition is @emph{true}.
3491 This is the converse of using assertions for program validation; in that
3492 situation, you want to stop when the assertion is violated---that is,
3493 when the condition is false. In C, if you want to test an assertion expressed
3494 by the condition @var{assert}, you should set the condition
3495 @samp{! @var{assert}} on the appropriate breakpoint.
3497 Conditions are also accepted for watchpoints; you may not need them,
3498 since a watchpoint is inspecting the value of an expression anyhow---but
3499 it might be simpler, say, to just set a watchpoint on a variable name,
3500 and specify a condition that tests whether the new value is an interesting
3503 Break conditions can have side effects, and may even call functions in
3504 your program. This can be useful, for example, to activate functions
3505 that log program progress, or to use your own print functions to
3506 format special data structures. The effects are completely predictable
3507 unless there is another enabled breakpoint at the same address. (In
3508 that case, @value{GDBN} might see the other breakpoint first and stop your
3509 program without checking the condition of this one.) Note that
3510 breakpoint commands are usually more convenient and flexible than break
3512 purpose of performing side effects when a breakpoint is reached
3513 (@pxref{Break Commands, ,Breakpoint command lists}).
3515 Break conditions can be specified when a breakpoint is set, by using
3516 @samp{if} in the arguments to the @code{break} command. @xref{Set
3517 Breaks, ,Setting breakpoints}. They can also be changed at any time
3518 with the @code{condition} command.
3520 You can also use the @code{if} keyword with the @code{watch} command.
3521 The @code{catch} command does not recognize the @code{if} keyword;
3522 @code{condition} is the only way to impose a further condition on a
3527 @item condition @var{bnum} @var{expression}
3528 Specify @var{expression} as the break condition for breakpoint,
3529 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3530 breakpoint @var{bnum} stops your program only if the value of
3531 @var{expression} is true (nonzero, in C). When you use
3532 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3533 syntactic correctness, and to determine whether symbols in it have
3534 referents in the context of your breakpoint. If @var{expression} uses
3535 symbols not referenced in the context of the breakpoint, @value{GDBN}
3536 prints an error message:
3539 No symbol "foo" in current context.
3544 not actually evaluate @var{expression} at the time the @code{condition}
3545 command (or a command that sets a breakpoint with a condition, like
3546 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3548 @item condition @var{bnum}
3549 Remove the condition from breakpoint number @var{bnum}. It becomes
3550 an ordinary unconditional breakpoint.
3553 @cindex ignore count (of breakpoint)
3554 A special case of a breakpoint condition is to stop only when the
3555 breakpoint has been reached a certain number of times. This is so
3556 useful that there is a special way to do it, using the @dfn{ignore
3557 count} of the breakpoint. Every breakpoint has an ignore count, which
3558 is an integer. Most of the time, the ignore count is zero, and
3559 therefore has no effect. But if your program reaches a breakpoint whose
3560 ignore count is positive, then instead of stopping, it just decrements
3561 the ignore count by one and continues. As a result, if the ignore count
3562 value is @var{n}, the breakpoint does not stop the next @var{n} times
3563 your program reaches it.
3567 @item ignore @var{bnum} @var{count}
3568 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3569 The next @var{count} times the breakpoint is reached, your program's
3570 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3573 To make the breakpoint stop the next time it is reached, specify
3576 When you use @code{continue} to resume execution of your program from a
3577 breakpoint, you can specify an ignore count directly as an argument to
3578 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3579 Stepping,,Continuing and stepping}.
3581 If a breakpoint has a positive ignore count and a condition, the
3582 condition is not checked. Once the ignore count reaches zero,
3583 @value{GDBN} resumes checking the condition.
3585 You could achieve the effect of the ignore count with a condition such
3586 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3587 is decremented each time. @xref{Convenience Vars, ,Convenience
3591 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3594 @node Break Commands
3595 @subsection Breakpoint command lists
3597 @cindex breakpoint commands
3598 You can give any breakpoint (or watchpoint or catchpoint) a series of
3599 commands to execute when your program stops due to that breakpoint. For
3600 example, you might want to print the values of certain expressions, or
3601 enable other breakpoints.
3605 @kindex end@r{ (breakpoint commands)}
3606 @item commands @r{[}@var{bnum}@r{]}
3607 @itemx @dots{} @var{command-list} @dots{}
3609 Specify a list of commands for breakpoint number @var{bnum}. The commands
3610 themselves appear on the following lines. Type a line containing just
3611 @code{end} to terminate the commands.
3613 To remove all commands from a breakpoint, type @code{commands} and
3614 follow it immediately with @code{end}; that is, give no commands.
3616 With no @var{bnum} argument, @code{commands} refers to the last
3617 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3618 recently encountered).
3621 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3622 disabled within a @var{command-list}.
3624 You can use breakpoint commands to start your program up again. Simply
3625 use the @code{continue} command, or @code{step}, or any other command
3626 that resumes execution.
3628 Any other commands in the command list, after a command that resumes
3629 execution, are ignored. This is because any time you resume execution
3630 (even with a simple @code{next} or @code{step}), you may encounter
3631 another breakpoint---which could have its own command list, leading to
3632 ambiguities about which list to execute.
3635 If the first command you specify in a command list is @code{silent}, the
3636 usual message about stopping at a breakpoint is not printed. This may
3637 be desirable for breakpoints that are to print a specific message and
3638 then continue. If none of the remaining commands print anything, you
3639 see no sign that the breakpoint was reached. @code{silent} is
3640 meaningful only at the beginning of a breakpoint command list.
3642 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3643 print precisely controlled output, and are often useful in silent
3644 breakpoints. @xref{Output, ,Commands for controlled output}.
3646 For example, here is how you could use breakpoint commands to print the
3647 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3653 printf "x is %d\n",x
3658 One application for breakpoint commands is to compensate for one bug so
3659 you can test for another. Put a breakpoint just after the erroneous line
3660 of code, give it a condition to detect the case in which something
3661 erroneous has been done, and give it commands to assign correct values
3662 to any variables that need them. End with the @code{continue} command
3663 so that your program does not stop, and start with the @code{silent}
3664 command so that no output is produced. Here is an example:
3675 @node Breakpoint Menus
3676 @subsection Breakpoint menus
3678 @cindex symbol overloading
3680 Some programming languages (notably C@t{++} and Objective-C) permit a
3681 single function name
3682 to be defined several times, for application in different contexts.
3683 This is called @dfn{overloading}. When a function name is overloaded,
3684 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3685 a breakpoint. If you realize this is a problem, you can use
3686 something like @samp{break @var{function}(@var{types})} to specify which
3687 particular version of the function you want. Otherwise, @value{GDBN} offers
3688 you a menu of numbered choices for different possible breakpoints, and
3689 waits for your selection with the prompt @samp{>}. The first two
3690 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3691 sets a breakpoint at each definition of @var{function}, and typing
3692 @kbd{0} aborts the @code{break} command without setting any new
3695 For example, the following session excerpt shows an attempt to set a
3696 breakpoint at the overloaded symbol @code{String::after}.
3697 We choose three particular definitions of that function name:
3699 @c FIXME! This is likely to change to show arg type lists, at least
3702 (@value{GDBP}) b String::after
3705 [2] file:String.cc; line number:867
3706 [3] file:String.cc; line number:860
3707 [4] file:String.cc; line number:875
3708 [5] file:String.cc; line number:853
3709 [6] file:String.cc; line number:846
3710 [7] file:String.cc; line number:735
3712 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3713 Breakpoint 2 at 0xb344: file String.cc, line 875.
3714 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3715 Multiple breakpoints were set.
3716 Use the "delete" command to delete unwanted
3722 @c @ifclear BARETARGET
3723 @node Error in Breakpoints
3724 @subsection ``Cannot insert breakpoints''
3726 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3728 Under some operating systems, breakpoints cannot be used in a program if
3729 any other process is running that program. In this situation,
3730 attempting to run or continue a program with a breakpoint causes
3731 @value{GDBN} to print an error message:
3734 Cannot insert breakpoints.
3735 The same program may be running in another process.
3738 When this happens, you have three ways to proceed:
3742 Remove or disable the breakpoints, then continue.
3745 Suspend @value{GDBN}, and copy the file containing your program to a new
3746 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3747 that @value{GDBN} should run your program under that name.
3748 Then start your program again.
3751 Relink your program so that the text segment is nonsharable, using the
3752 linker option @samp{-N}. The operating system limitation may not apply
3753 to nonsharable executables.
3757 A similar message can be printed if you request too many active
3758 hardware-assisted breakpoints and watchpoints:
3760 @c FIXME: the precise wording of this message may change; the relevant
3761 @c source change is not committed yet (Sep 3, 1999).
3763 Stopped; cannot insert breakpoints.
3764 You may have requested too many hardware breakpoints and watchpoints.
3768 This message is printed when you attempt to resume the program, since
3769 only then @value{GDBN} knows exactly how many hardware breakpoints and
3770 watchpoints it needs to insert.
3772 When this message is printed, you need to disable or remove some of the
3773 hardware-assisted breakpoints and watchpoints, and then continue.
3775 @node Breakpoint related warnings
3776 @subsection ``Breakpoint address adjusted...''
3777 @cindex breakpoint address adjusted
3779 Some processor architectures place constraints on the addresses at
3780 which breakpoints may be placed. For architectures thus constrained,
3781 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3782 with the constraints dictated by the architecture.
3784 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3785 a VLIW architecture in which a number of RISC-like instructions may be
3786 bundled together for parallel execution. The FR-V architecture
3787 constrains the location of a breakpoint instruction within such a
3788 bundle to the instruction with the lowest address. @value{GDBN}
3789 honors this constraint by adjusting a breakpoint's address to the
3790 first in the bundle.
3792 It is not uncommon for optimized code to have bundles which contain
3793 instructions from different source statements, thus it may happen that
3794 a breakpoint's address will be adjusted from one source statement to
3795 another. Since this adjustment may significantly alter @value{GDBN}'s
3796 breakpoint related behavior from what the user expects, a warning is
3797 printed when the breakpoint is first set and also when the breakpoint
3800 A warning like the one below is printed when setting a breakpoint
3801 that's been subject to address adjustment:
3804 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3807 Such warnings are printed both for user settable and @value{GDBN}'s
3808 internal breakpoints. If you see one of these warnings, you should
3809 verify that a breakpoint set at the adjusted address will have the
3810 desired affect. If not, the breakpoint in question may be removed and
3811 other breakpoints may be set which will have the desired behavior.
3812 E.g., it may be sufficient to place the breakpoint at a later
3813 instruction. A conditional breakpoint may also be useful in some
3814 cases to prevent the breakpoint from triggering too often.
3816 @value{GDBN} will also issue a warning when stopping at one of these
3817 adjusted breakpoints:
3820 warning: Breakpoint 1 address previously adjusted from 0x00010414
3824 When this warning is encountered, it may be too late to take remedial
3825 action except in cases where the breakpoint is hit earlier or more
3826 frequently than expected.
3828 @node Continuing and Stepping
3829 @section Continuing and stepping
3833 @cindex resuming execution
3834 @dfn{Continuing} means resuming program execution until your program
3835 completes normally. In contrast, @dfn{stepping} means executing just
3836 one more ``step'' of your program, where ``step'' may mean either one
3837 line of source code, or one machine instruction (depending on what
3838 particular command you use). Either when continuing or when stepping,
3839 your program may stop even sooner, due to a breakpoint or a signal. (If
3840 it stops due to a signal, you may want to use @code{handle}, or use
3841 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3845 @kindex c @r{(@code{continue})}
3846 @kindex fg @r{(resume foreground execution)}
3847 @item continue @r{[}@var{ignore-count}@r{]}
3848 @itemx c @r{[}@var{ignore-count}@r{]}
3849 @itemx fg @r{[}@var{ignore-count}@r{]}
3850 Resume program execution, at the address where your program last stopped;
3851 any breakpoints set at that address are bypassed. The optional argument
3852 @var{ignore-count} allows you to specify a further number of times to
3853 ignore a breakpoint at this location; its effect is like that of
3854 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3856 The argument @var{ignore-count} is meaningful only when your program
3857 stopped due to a breakpoint. At other times, the argument to
3858 @code{continue} is ignored.
3860 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3861 debugged program is deemed to be the foreground program) are provided
3862 purely for convenience, and have exactly the same behavior as
3866 To resume execution at a different place, you can use @code{return}
3867 (@pxref{Returning, ,Returning from a function}) to go back to the
3868 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3869 different address}) to go to an arbitrary location in your program.
3871 A typical technique for using stepping is to set a breakpoint
3872 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3873 beginning of the function or the section of your program where a problem
3874 is believed to lie, run your program until it stops at that breakpoint,
3875 and then step through the suspect area, examining the variables that are
3876 interesting, until you see the problem happen.
3880 @kindex s @r{(@code{step})}
3882 Continue running your program until control reaches a different source
3883 line, then stop it and return control to @value{GDBN}. This command is
3884 abbreviated @code{s}.
3887 @c "without debugging information" is imprecise; actually "without line
3888 @c numbers in the debugging information". (gcc -g1 has debugging info but
3889 @c not line numbers). But it seems complex to try to make that
3890 @c distinction here.
3891 @emph{Warning:} If you use the @code{step} command while control is
3892 within a function that was compiled without debugging information,
3893 execution proceeds until control reaches a function that does have
3894 debugging information. Likewise, it will not step into a function which
3895 is compiled without debugging information. To step through functions
3896 without debugging information, use the @code{stepi} command, described
3900 The @code{step} command only stops at the first instruction of a source
3901 line. This prevents the multiple stops that could otherwise occur in
3902 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3903 to stop if a function that has debugging information is called within
3904 the line. In other words, @code{step} @emph{steps inside} any functions
3905 called within the line.
3907 Also, the @code{step} command only enters a function if there is line
3908 number information for the function. Otherwise it acts like the
3909 @code{next} command. This avoids problems when using @code{cc -gl}
3910 on MIPS machines. Previously, @code{step} entered subroutines if there
3911 was any debugging information about the routine.
3913 @item step @var{count}
3914 Continue running as in @code{step}, but do so @var{count} times. If a
3915 breakpoint is reached, or a signal not related to stepping occurs before
3916 @var{count} steps, stepping stops right away.
3919 @kindex n @r{(@code{next})}
3920 @item next @r{[}@var{count}@r{]}
3921 Continue to the next source line in the current (innermost) stack frame.
3922 This is similar to @code{step}, but function calls that appear within
3923 the line of code are executed without stopping. Execution stops when
3924 control reaches a different line of code at the original stack level
3925 that was executing when you gave the @code{next} command. This command
3926 is abbreviated @code{n}.
3928 An argument @var{count} is a repeat count, as for @code{step}.
3931 @c FIX ME!! Do we delete this, or is there a way it fits in with
3932 @c the following paragraph? --- Vctoria
3934 @c @code{next} within a function that lacks debugging information acts like
3935 @c @code{step}, but any function calls appearing within the code of the
3936 @c function are executed without stopping.
3938 The @code{next} command only stops at the first instruction of a
3939 source line. This prevents multiple stops that could otherwise occur in
3940 @code{switch} statements, @code{for} loops, etc.
3942 @kindex set step-mode
3944 @cindex functions without line info, and stepping
3945 @cindex stepping into functions with no line info
3946 @itemx set step-mode on
3947 The @code{set step-mode on} command causes the @code{step} command to
3948 stop at the first instruction of a function which contains no debug line
3949 information rather than stepping over it.
3951 This is useful in cases where you may be interested in inspecting the
3952 machine instructions of a function which has no symbolic info and do not
3953 want @value{GDBN} to automatically skip over this function.
3955 @item set step-mode off
3956 Causes the @code{step} command to step over any functions which contains no
3957 debug information. This is the default.
3959 @item show step-mode
3960 Show whether @value{GDBN} will stop in or step over functions without
3961 source line debug information.
3965 Continue running until just after function in the selected stack frame
3966 returns. Print the returned value (if any).
3968 Contrast this with the @code{return} command (@pxref{Returning,
3969 ,Returning from a function}).
3972 @kindex u @r{(@code{until})}
3973 @cindex run until specified location
3976 Continue running until a source line past the current line, in the
3977 current stack frame, is reached. This command is used to avoid single
3978 stepping through a loop more than once. It is like the @code{next}
3979 command, except that when @code{until} encounters a jump, it
3980 automatically continues execution until the program counter is greater
3981 than the address of the jump.
3983 This means that when you reach the end of a loop after single stepping
3984 though it, @code{until} makes your program continue execution until it
3985 exits the loop. In contrast, a @code{next} command at the end of a loop
3986 simply steps back to the beginning of the loop, which forces you to step
3987 through the next iteration.
3989 @code{until} always stops your program if it attempts to exit the current
3992 @code{until} may produce somewhat counterintuitive results if the order
3993 of machine code does not match the order of the source lines. For
3994 example, in the following excerpt from a debugging session, the @code{f}
3995 (@code{frame}) command shows that execution is stopped at line
3996 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4000 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4002 (@value{GDBP}) until
4003 195 for ( ; argc > 0; NEXTARG) @{
4006 This happened because, for execution efficiency, the compiler had
4007 generated code for the loop closure test at the end, rather than the
4008 start, of the loop---even though the test in a C @code{for}-loop is
4009 written before the body of the loop. The @code{until} command appeared
4010 to step back to the beginning of the loop when it advanced to this
4011 expression; however, it has not really gone to an earlier
4012 statement---not in terms of the actual machine code.
4014 @code{until} with no argument works by means of single
4015 instruction stepping, and hence is slower than @code{until} with an
4018 @item until @var{location}
4019 @itemx u @var{location}
4020 Continue running your program until either the specified location is
4021 reached, or the current stack frame returns. @var{location} is any of
4022 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
4023 ,Setting breakpoints}). This form of the command uses breakpoints, and
4024 hence is quicker than @code{until} without an argument. The specified
4025 location is actually reached only if it is in the current frame. This
4026 implies that @code{until} can be used to skip over recursive function
4027 invocations. For instance in the code below, if the current location is
4028 line @code{96}, issuing @code{until 99} will execute the program up to
4029 line @code{99} in the same invocation of factorial, i.e. after the inner
4030 invocations have returned.
4033 94 int factorial (int value)
4035 96 if (value > 1) @{
4036 97 value *= factorial (value - 1);
4043 @kindex advance @var{location}
4044 @itemx advance @var{location}
4045 Continue running the program up to the given @var{location}. An argument is
4046 required, which should be of the same form as arguments for the @code{break}
4047 command. Execution will also stop upon exit from the current stack
4048 frame. This command is similar to @code{until}, but @code{advance} will
4049 not skip over recursive function calls, and the target location doesn't
4050 have to be in the same frame as the current one.
4054 @kindex si @r{(@code{stepi})}
4056 @itemx stepi @var{arg}
4058 Execute one machine instruction, then stop and return to the debugger.
4060 It is often useful to do @samp{display/i $pc} when stepping by machine
4061 instructions. This makes @value{GDBN} automatically display the next
4062 instruction to be executed, each time your program stops. @xref{Auto
4063 Display,, Automatic display}.
4065 An argument is a repeat count, as in @code{step}.
4069 @kindex ni @r{(@code{nexti})}
4071 @itemx nexti @var{arg}
4073 Execute one machine instruction, but if it is a function call,
4074 proceed until the function returns.
4076 An argument is a repeat count, as in @code{next}.
4083 A signal is an asynchronous event that can happen in a program. The
4084 operating system defines the possible kinds of signals, and gives each
4085 kind a name and a number. For example, in Unix @code{SIGINT} is the
4086 signal a program gets when you type an interrupt character (often @kbd{C-c});
4087 @code{SIGSEGV} is the signal a program gets from referencing a place in
4088 memory far away from all the areas in use; @code{SIGALRM} occurs when
4089 the alarm clock timer goes off (which happens only if your program has
4090 requested an alarm).
4092 @cindex fatal signals
4093 Some signals, including @code{SIGALRM}, are a normal part of the
4094 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4095 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4096 program has not specified in advance some other way to handle the signal.
4097 @code{SIGINT} does not indicate an error in your program, but it is normally
4098 fatal so it can carry out the purpose of the interrupt: to kill the program.
4100 @value{GDBN} has the ability to detect any occurrence of a signal in your
4101 program. You can tell @value{GDBN} in advance what to do for each kind of
4104 @cindex handling signals
4105 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4106 @code{SIGALRM} be silently passed to your program
4107 (so as not to interfere with their role in the program's functioning)
4108 but to stop your program immediately whenever an error signal happens.
4109 You can change these settings with the @code{handle} command.
4112 @kindex info signals
4116 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4117 handle each one. You can use this to see the signal numbers of all
4118 the defined types of signals.
4120 @code{info handle} is an alias for @code{info signals}.
4123 @item handle @var{signal} @var{keywords}@dots{}
4124 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4125 can be the number of a signal or its name (with or without the
4126 @samp{SIG} at the beginning); a list of signal numbers of the form
4127 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4128 known signals. The @var{keywords} say what change to make.
4132 The keywords allowed by the @code{handle} command can be abbreviated.
4133 Their full names are:
4137 @value{GDBN} should not stop your program when this signal happens. It may
4138 still print a message telling you that the signal has come in.
4141 @value{GDBN} should stop your program when this signal happens. This implies
4142 the @code{print} keyword as well.
4145 @value{GDBN} should print a message when this signal happens.
4148 @value{GDBN} should not mention the occurrence of the signal at all. This
4149 implies the @code{nostop} keyword as well.
4153 @value{GDBN} should allow your program to see this signal; your program
4154 can handle the signal, or else it may terminate if the signal is fatal
4155 and not handled. @code{pass} and @code{noignore} are synonyms.
4159 @value{GDBN} should not allow your program to see this signal.
4160 @code{nopass} and @code{ignore} are synonyms.
4164 When a signal stops your program, the signal is not visible to the
4166 continue. Your program sees the signal then, if @code{pass} is in
4167 effect for the signal in question @emph{at that time}. In other words,
4168 after @value{GDBN} reports a signal, you can use the @code{handle}
4169 command with @code{pass} or @code{nopass} to control whether your
4170 program sees that signal when you continue.
4172 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4173 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4174 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4177 You can also use the @code{signal} command to prevent your program from
4178 seeing a signal, or cause it to see a signal it normally would not see,
4179 or to give it any signal at any time. For example, if your program stopped
4180 due to some sort of memory reference error, you might store correct
4181 values into the erroneous variables and continue, hoping to see more
4182 execution; but your program would probably terminate immediately as
4183 a result of the fatal signal once it saw the signal. To prevent this,
4184 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4188 @section Stopping and starting multi-thread programs
4190 When your program has multiple threads (@pxref{Threads,, Debugging
4191 programs with multiple threads}), you can choose whether to set
4192 breakpoints on all threads, or on a particular thread.
4195 @cindex breakpoints and threads
4196 @cindex thread breakpoints
4197 @kindex break @dots{} thread @var{threadno}
4198 @item break @var{linespec} thread @var{threadno}
4199 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4200 @var{linespec} specifies source lines; there are several ways of
4201 writing them, but the effect is always to specify some source line.
4203 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4204 to specify that you only want @value{GDBN} to stop the program when a
4205 particular thread reaches this breakpoint. @var{threadno} is one of the
4206 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4207 column of the @samp{info threads} display.
4209 If you do not specify @samp{thread @var{threadno}} when you set a
4210 breakpoint, the breakpoint applies to @emph{all} threads of your
4213 You can use the @code{thread} qualifier on conditional breakpoints as
4214 well; in this case, place @samp{thread @var{threadno}} before the
4215 breakpoint condition, like this:
4218 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4223 @cindex stopped threads
4224 @cindex threads, stopped
4225 Whenever your program stops under @value{GDBN} for any reason,
4226 @emph{all} threads of execution stop, not just the current thread. This
4227 allows you to examine the overall state of the program, including
4228 switching between threads, without worrying that things may change
4231 @cindex thread breakpoints and system calls
4232 @cindex system calls and thread breakpoints
4233 @cindex premature return from system calls
4234 There is an unfortunate side effect. If one thread stops for a
4235 breakpoint, or for some other reason, and another thread is blocked in a
4236 system call, then the system call may return prematurely. This is a
4237 consequence of the interaction between multiple threads and the signals
4238 that @value{GDBN} uses to implement breakpoints and other events that
4241 To handle this problem, your program should check the return value of
4242 each system call and react appropriately. This is good programming
4245 For example, do not write code like this:
4251 The call to @code{sleep} will return early if a different thread stops
4252 at a breakpoint or for some other reason.
4254 Instead, write this:
4259 unslept = sleep (unslept);
4262 A system call is allowed to return early, so the system is still
4263 conforming to its specification. But @value{GDBN} does cause your
4264 multi-threaded program to behave differently than it would without
4267 Also, @value{GDBN} uses internal breakpoints in the thread library to
4268 monitor certain events such as thread creation and thread destruction.
4269 When such an event happens, a system call in another thread may return
4270 prematurely, even though your program does not appear to stop.
4272 @cindex continuing threads
4273 @cindex threads, continuing
4274 Conversely, whenever you restart the program, @emph{all} threads start
4275 executing. @emph{This is true even when single-stepping} with commands
4276 like @code{step} or @code{next}.
4278 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4279 Since thread scheduling is up to your debugging target's operating
4280 system (not controlled by @value{GDBN}), other threads may
4281 execute more than one statement while the current thread completes a
4282 single step. Moreover, in general other threads stop in the middle of a
4283 statement, rather than at a clean statement boundary, when the program
4286 You might even find your program stopped in another thread after
4287 continuing or even single-stepping. This happens whenever some other
4288 thread runs into a breakpoint, a signal, or an exception before the
4289 first thread completes whatever you requested.
4291 On some OSes, you can lock the OS scheduler and thus allow only a single
4295 @item set scheduler-locking @var{mode}
4296 @cindex scheduler locking mode
4297 @cindex lock scheduler
4298 Set the scheduler locking mode. If it is @code{off}, then there is no
4299 locking and any thread may run at any time. If @code{on}, then only the
4300 current thread may run when the inferior is resumed. The @code{step}
4301 mode optimizes for single-stepping. It stops other threads from
4302 ``seizing the prompt'' by preempting the current thread while you are
4303 stepping. Other threads will only rarely (or never) get a chance to run
4304 when you step. They are more likely to run when you @samp{next} over a
4305 function call, and they are completely free to run when you use commands
4306 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4307 thread hits a breakpoint during its timeslice, they will never steal the
4308 @value{GDBN} prompt away from the thread that you are debugging.
4310 @item show scheduler-locking
4311 Display the current scheduler locking mode.
4316 @chapter Examining the Stack
4318 When your program has stopped, the first thing you need to know is where it
4319 stopped and how it got there.
4322 Each time your program performs a function call, information about the call
4324 That information includes the location of the call in your program,
4325 the arguments of the call,
4326 and the local variables of the function being called.
4327 The information is saved in a block of data called a @dfn{stack frame}.
4328 The stack frames are allocated in a region of memory called the @dfn{call
4331 When your program stops, the @value{GDBN} commands for examining the
4332 stack allow you to see all of this information.
4334 @cindex selected frame
4335 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4336 @value{GDBN} commands refer implicitly to the selected frame. In
4337 particular, whenever you ask @value{GDBN} for the value of a variable in
4338 your program, the value is found in the selected frame. There are
4339 special @value{GDBN} commands to select whichever frame you are
4340 interested in. @xref{Selection, ,Selecting a frame}.
4342 When your program stops, @value{GDBN} automatically selects the
4343 currently executing frame and describes it briefly, similar to the
4344 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
4347 * Frames:: Stack frames
4348 * Backtrace:: Backtraces
4349 * Selection:: Selecting a frame
4350 * Frame Info:: Information on a frame
4355 @section Stack frames
4357 @cindex frame, definition
4359 The call stack is divided up into contiguous pieces called @dfn{stack
4360 frames}, or @dfn{frames} for short; each frame is the data associated
4361 with one call to one function. The frame contains the arguments given
4362 to the function, the function's local variables, and the address at
4363 which the function is executing.
4365 @cindex initial frame
4366 @cindex outermost frame
4367 @cindex innermost frame
4368 When your program is started, the stack has only one frame, that of the
4369 function @code{main}. This is called the @dfn{initial} frame or the
4370 @dfn{outermost} frame. Each time a function is called, a new frame is
4371 made. Each time a function returns, the frame for that function invocation
4372 is eliminated. If a function is recursive, there can be many frames for
4373 the same function. The frame for the function in which execution is
4374 actually occurring is called the @dfn{innermost} frame. This is the most
4375 recently created of all the stack frames that still exist.
4377 @cindex frame pointer
4378 Inside your program, stack frames are identified by their addresses. A
4379 stack frame consists of many bytes, each of which has its own address; each
4380 kind of computer has a convention for choosing one byte whose
4381 address serves as the address of the frame. Usually this address is kept
4382 in a register called the @dfn{frame pointer register}
4383 (@pxref{Registers, $fp}) while execution is going on in that frame.
4385 @cindex frame number
4386 @value{GDBN} assigns numbers to all existing stack frames, starting with
4387 zero for the innermost frame, one for the frame that called it,
4388 and so on upward. These numbers do not really exist in your program;
4389 they are assigned by @value{GDBN} to give you a way of designating stack
4390 frames in @value{GDBN} commands.
4392 @c The -fomit-frame-pointer below perennially causes hbox overflow
4393 @c underflow problems.
4394 @cindex frameless execution
4395 Some compilers provide a way to compile functions so that they operate
4396 without stack frames. (For example, the @value{GCC} option
4398 @samp{-fomit-frame-pointer}
4400 generates functions without a frame.)
4401 This is occasionally done with heavily used library functions to save
4402 the frame setup time. @value{GDBN} has limited facilities for dealing
4403 with these function invocations. If the innermost function invocation
4404 has no stack frame, @value{GDBN} nevertheless regards it as though
4405 it had a separate frame, which is numbered zero as usual, allowing
4406 correct tracing of the function call chain. However, @value{GDBN} has
4407 no provision for frameless functions elsewhere in the stack.
4410 @kindex frame@r{, command}
4411 @cindex current stack frame
4412 @item frame @var{args}
4413 The @code{frame} command allows you to move from one stack frame to another,
4414 and to print the stack frame you select. @var{args} may be either the
4415 address of the frame or the stack frame number. Without an argument,
4416 @code{frame} prints the current stack frame.
4418 @kindex select-frame
4419 @cindex selecting frame silently
4421 The @code{select-frame} command allows you to move from one stack frame
4422 to another without printing the frame. This is the silent version of
4430 @cindex call stack traces
4431 A backtrace is a summary of how your program got where it is. It shows one
4432 line per frame, for many frames, starting with the currently executing
4433 frame (frame zero), followed by its caller (frame one), and on up the
4438 @kindex bt @r{(@code{backtrace})}
4441 Print a backtrace of the entire stack: one line per frame for all
4442 frames in the stack.
4444 You can stop the backtrace at any time by typing the system interrupt
4445 character, normally @kbd{C-c}.
4447 @item backtrace @var{n}
4449 Similar, but print only the innermost @var{n} frames.
4451 @item backtrace -@var{n}
4453 Similar, but print only the outermost @var{n} frames.
4455 @item backtrace full
4456 Print the values of the local variables also.
4462 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4463 are additional aliases for @code{backtrace}.
4465 @cindex multiple threads, backtrace
4466 In a multi-threaded program, @value{GDBN} by default shows the
4467 backtrace only for the current thread. To display the backtrace for
4468 several or all of the threads, use the command @code{thread apply}
4469 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
4470 apply all backtrace}, @value{GDBN} will display the backtrace for all
4471 the threads; this is handy when you debug a core dump of a
4472 multi-threaded program.
4474 Each line in the backtrace shows the frame number and the function name.
4475 The program counter value is also shown---unless you use @code{set
4476 print address off}. The backtrace also shows the source file name and
4477 line number, as well as the arguments to the function. The program
4478 counter value is omitted if it is at the beginning of the code for that
4481 Here is an example of a backtrace. It was made with the command
4482 @samp{bt 3}, so it shows the innermost three frames.
4486 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4488 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4489 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4491 (More stack frames follow...)
4496 The display for frame zero does not begin with a program counter
4497 value, indicating that your program has stopped at the beginning of the
4498 code for line @code{993} of @code{builtin.c}.
4500 @cindex value optimized out, in backtrace
4501 @cindex function call arguments, optimized out
4502 If your program was compiled with optimizations, some compilers will
4503 optimize away arguments passed to functions if those arguments are
4504 never used after the call. Such optimizations generate code that
4505 passes arguments through registers, but doesn't store those arguments
4506 in the stack frame. @value{GDBN} has no way of displaying such
4507 arguments in stack frames other than the innermost one. Here's what
4508 such a backtrace might look like:
4512 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4514 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
4515 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
4517 (More stack frames follow...)
4522 The values of arguments that were not saved in their stack frames are
4523 shown as @samp{<value optimized out>}.
4525 If you need to display the values of such optimized-out arguments,
4526 either deduce that from other variables whose values depend on the one
4527 you are interested in, or recompile without optimizations.
4529 @cindex backtrace beyond @code{main} function
4530 @cindex program entry point
4531 @cindex startup code, and backtrace
4532 Most programs have a standard user entry point---a place where system
4533 libraries and startup code transition into user code. For C this is
4534 @code{main}@footnote{
4535 Note that embedded programs (the so-called ``free-standing''
4536 environment) are not required to have a @code{main} function as the
4537 entry point. They could even have multiple entry points.}.
4538 When @value{GDBN} finds the entry function in a backtrace
4539 it will terminate the backtrace, to avoid tracing into highly
4540 system-specific (and generally uninteresting) code.
4542 If you need to examine the startup code, or limit the number of levels
4543 in a backtrace, you can change this behavior:
4546 @item set backtrace past-main
4547 @itemx set backtrace past-main on
4548 @kindex set backtrace
4549 Backtraces will continue past the user entry point.
4551 @item set backtrace past-main off
4552 Backtraces will stop when they encounter the user entry point. This is the
4555 @item show backtrace past-main
4556 @kindex show backtrace
4557 Display the current user entry point backtrace policy.
4559 @item set backtrace past-entry
4560 @itemx set backtrace past-entry on
4561 Backtraces will continue past the internal entry point of an application.
4562 This entry point is encoded by the linker when the application is built,
4563 and is likely before the user entry point @code{main} (or equivalent) is called.
4565 @item set backtrace past-entry off
4566 Backtraces will stop when they encouter the internal entry point of an
4567 application. This is the default.
4569 @item show backtrace past-entry
4570 Display the current internal entry point backtrace policy.
4572 @item set backtrace limit @var{n}
4573 @itemx set backtrace limit 0
4574 @cindex backtrace limit
4575 Limit the backtrace to @var{n} levels. A value of zero means
4578 @item show backtrace limit
4579 Display the current limit on backtrace levels.
4583 @section Selecting a frame
4585 Most commands for examining the stack and other data in your program work on
4586 whichever stack frame is selected at the moment. Here are the commands for
4587 selecting a stack frame; all of them finish by printing a brief description
4588 of the stack frame just selected.
4591 @kindex frame@r{, selecting}
4592 @kindex f @r{(@code{frame})}
4595 Select frame number @var{n}. Recall that frame zero is the innermost
4596 (currently executing) frame, frame one is the frame that called the
4597 innermost one, and so on. The highest-numbered frame is the one for
4600 @item frame @var{addr}
4602 Select the frame at address @var{addr}. This is useful mainly if the
4603 chaining of stack frames has been damaged by a bug, making it
4604 impossible for @value{GDBN} to assign numbers properly to all frames. In
4605 addition, this can be useful when your program has multiple stacks and
4606 switches between them.
4608 On the SPARC architecture, @code{frame} needs two addresses to
4609 select an arbitrary frame: a frame pointer and a stack pointer.
4611 On the MIPS and Alpha architecture, it needs two addresses: a stack
4612 pointer and a program counter.
4614 On the 29k architecture, it needs three addresses: a register stack
4615 pointer, a program counter, and a memory stack pointer.
4619 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4620 advances toward the outermost frame, to higher frame numbers, to frames
4621 that have existed longer. @var{n} defaults to one.
4624 @kindex do @r{(@code{down})}
4626 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4627 advances toward the innermost frame, to lower frame numbers, to frames
4628 that were created more recently. @var{n} defaults to one. You may
4629 abbreviate @code{down} as @code{do}.
4632 All of these commands end by printing two lines of output describing the
4633 frame. The first line shows the frame number, the function name, the
4634 arguments, and the source file and line number of execution in that
4635 frame. The second line shows the text of that source line.
4643 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4645 10 read_input_file (argv[i]);
4649 After such a printout, the @code{list} command with no arguments
4650 prints ten lines centered on the point of execution in the frame.
4651 You can also edit the program at the point of execution with your favorite
4652 editing program by typing @code{edit}.
4653 @xref{List, ,Printing source lines},
4657 @kindex down-silently
4659 @item up-silently @var{n}
4660 @itemx down-silently @var{n}
4661 These two commands are variants of @code{up} and @code{down},
4662 respectively; they differ in that they do their work silently, without
4663 causing display of the new frame. They are intended primarily for use
4664 in @value{GDBN} command scripts, where the output might be unnecessary and
4669 @section Information about a frame
4671 There are several other commands to print information about the selected
4677 When used without any argument, this command does not change which
4678 frame is selected, but prints a brief description of the currently
4679 selected stack frame. It can be abbreviated @code{f}. With an
4680 argument, this command is used to select a stack frame.
4681 @xref{Selection, ,Selecting a frame}.
4684 @kindex info f @r{(@code{info frame})}
4687 This command prints a verbose description of the selected stack frame,
4692 the address of the frame
4694 the address of the next frame down (called by this frame)
4696 the address of the next frame up (caller of this frame)
4698 the language in which the source code corresponding to this frame is written
4700 the address of the frame's arguments
4702 the address of the frame's local variables
4704 the program counter saved in it (the address of execution in the caller frame)
4706 which registers were saved in the frame
4709 @noindent The verbose description is useful when
4710 something has gone wrong that has made the stack format fail to fit
4711 the usual conventions.
4713 @item info frame @var{addr}
4714 @itemx info f @var{addr}
4715 Print a verbose description of the frame at address @var{addr}, without
4716 selecting that frame. The selected frame remains unchanged by this
4717 command. This requires the same kind of address (more than one for some
4718 architectures) that you specify in the @code{frame} command.
4719 @xref{Selection, ,Selecting a frame}.
4723 Print the arguments of the selected frame, each on a separate line.
4727 Print the local variables of the selected frame, each on a separate
4728 line. These are all variables (declared either static or automatic)
4729 accessible at the point of execution of the selected frame.
4732 @cindex catch exceptions, list active handlers
4733 @cindex exception handlers, how to list
4735 Print a list of all the exception handlers that are active in the
4736 current stack frame at the current point of execution. To see other
4737 exception handlers, visit the associated frame (using the @code{up},
4738 @code{down}, or @code{frame} commands); then type @code{info catch}.
4739 @xref{Set Catchpoints, , Setting catchpoints}.
4745 @chapter Examining Source Files
4747 @value{GDBN} can print parts of your program's source, since the debugging
4748 information recorded in the program tells @value{GDBN} what source files were
4749 used to build it. When your program stops, @value{GDBN} spontaneously prints
4750 the line where it stopped. Likewise, when you select a stack frame
4751 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4752 execution in that frame has stopped. You can print other portions of
4753 source files by explicit command.
4755 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4756 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4757 @value{GDBN} under @sc{gnu} Emacs}.
4760 * List:: Printing source lines
4761 * Edit:: Editing source files
4762 * Search:: Searching source files
4763 * Source Path:: Specifying source directories
4764 * Machine Code:: Source and machine code
4768 @section Printing source lines
4771 @kindex l @r{(@code{list})}
4772 To print lines from a source file, use the @code{list} command
4773 (abbreviated @code{l}). By default, ten lines are printed.
4774 There are several ways to specify what part of the file you want to print.
4776 Here are the forms of the @code{list} command most commonly used:
4779 @item list @var{linenum}
4780 Print lines centered around line number @var{linenum} in the
4781 current source file.
4783 @item list @var{function}
4784 Print lines centered around the beginning of function
4788 Print more lines. If the last lines printed were printed with a
4789 @code{list} command, this prints lines following the last lines
4790 printed; however, if the last line printed was a solitary line printed
4791 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4792 Stack}), this prints lines centered around that line.
4795 Print lines just before the lines last printed.
4798 @cindex @code{list}, how many lines to display
4799 By default, @value{GDBN} prints ten source lines with any of these forms of
4800 the @code{list} command. You can change this using @code{set listsize}:
4803 @kindex set listsize
4804 @item set listsize @var{count}
4805 Make the @code{list} command display @var{count} source lines (unless
4806 the @code{list} argument explicitly specifies some other number).
4808 @kindex show listsize
4810 Display the number of lines that @code{list} prints.
4813 Repeating a @code{list} command with @key{RET} discards the argument,
4814 so it is equivalent to typing just @code{list}. This is more useful
4815 than listing the same lines again. An exception is made for an
4816 argument of @samp{-}; that argument is preserved in repetition so that
4817 each repetition moves up in the source file.
4820 In general, the @code{list} command expects you to supply zero, one or two
4821 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4822 of writing them, but the effect is always to specify some source line.
4823 Here is a complete description of the possible arguments for @code{list}:
4826 @item list @var{linespec}
4827 Print lines centered around the line specified by @var{linespec}.
4829 @item list @var{first},@var{last}
4830 Print lines from @var{first} to @var{last}. Both arguments are
4833 @item list ,@var{last}
4834 Print lines ending with @var{last}.
4836 @item list @var{first},
4837 Print lines starting with @var{first}.
4840 Print lines just after the lines last printed.
4843 Print lines just before the lines last printed.
4846 As described in the preceding table.
4849 Here are the ways of specifying a single source line---all the
4854 Specifies line @var{number} of the current source file.
4855 When a @code{list} command has two linespecs, this refers to
4856 the same source file as the first linespec.
4859 Specifies the line @var{offset} lines after the last line printed.
4860 When used as the second linespec in a @code{list} command that has
4861 two, this specifies the line @var{offset} lines down from the
4865 Specifies the line @var{offset} lines before the last line printed.
4867 @item @var{filename}:@var{number}
4868 Specifies line @var{number} in the source file @var{filename}.
4870 @item @var{function}
4871 Specifies the line that begins the body of the function @var{function}.
4872 For example: in C, this is the line with the open brace.
4874 @item @var{filename}:@var{function}
4875 Specifies the line of the open-brace that begins the body of the
4876 function @var{function} in the file @var{filename}. You only need the
4877 file name with a function name to avoid ambiguity when there are
4878 identically named functions in different source files.
4880 @item *@var{address}
4881 Specifies the line containing the program address @var{address}.
4882 @var{address} may be any expression.
4886 @section Editing source files
4887 @cindex editing source files
4890 @kindex e @r{(@code{edit})}
4891 To edit the lines in a source file, use the @code{edit} command.
4892 The editing program of your choice
4893 is invoked with the current line set to
4894 the active line in the program.
4895 Alternatively, there are several ways to specify what part of the file you
4896 want to print if you want to see other parts of the program.
4898 Here are the forms of the @code{edit} command most commonly used:
4902 Edit the current source file at the active line number in the program.
4904 @item edit @var{number}
4905 Edit the current source file with @var{number} as the active line number.
4907 @item edit @var{function}
4908 Edit the file containing @var{function} at the beginning of its definition.
4910 @item edit @var{filename}:@var{number}
4911 Specifies line @var{number} in the source file @var{filename}.
4913 @item edit @var{filename}:@var{function}
4914 Specifies the line that begins the body of the
4915 function @var{function} in the file @var{filename}. You only need the
4916 file name with a function name to avoid ambiguity when there are
4917 identically named functions in different source files.
4919 @item edit *@var{address}
4920 Specifies the line containing the program address @var{address}.
4921 @var{address} may be any expression.
4924 @subsection Choosing your editor
4925 You can customize @value{GDBN} to use any editor you want
4927 The only restriction is that your editor (say @code{ex}), recognizes the
4928 following command-line syntax:
4930 ex +@var{number} file
4932 The optional numeric value +@var{number} specifies the number of the line in
4933 the file where to start editing.}.
4934 By default, it is @file{@value{EDITOR}}, but you can change this
4935 by setting the environment variable @code{EDITOR} before using
4936 @value{GDBN}. For example, to configure @value{GDBN} to use the
4937 @code{vi} editor, you could use these commands with the @code{sh} shell:
4943 or in the @code{csh} shell,
4945 setenv EDITOR /usr/bin/vi
4950 @section Searching source files
4951 @cindex searching source files
4953 There are two commands for searching through the current source file for a
4958 @kindex forward-search
4959 @item forward-search @var{regexp}
4960 @itemx search @var{regexp}
4961 The command @samp{forward-search @var{regexp}} checks each line,
4962 starting with the one following the last line listed, for a match for
4963 @var{regexp}. It lists the line that is found. You can use the
4964 synonym @samp{search @var{regexp}} or abbreviate the command name as
4967 @kindex reverse-search
4968 @item reverse-search @var{regexp}
4969 The command @samp{reverse-search @var{regexp}} checks each line, starting
4970 with the one before the last line listed and going backward, for a match
4971 for @var{regexp}. It lists the line that is found. You can abbreviate
4972 this command as @code{rev}.
4976 @section Specifying source directories
4979 @cindex directories for source files
4980 Executable programs sometimes do not record the directories of the source
4981 files from which they were compiled, just the names. Even when they do,
4982 the directories could be moved between the compilation and your debugging
4983 session. @value{GDBN} has a list of directories to search for source files;
4984 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
4985 it tries all the directories in the list, in the order they are present
4986 in the list, until it finds a file with the desired name.
4988 For example, suppose an executable references the file
4989 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
4990 @file{/mnt/cross}. The file is first looked up literally; if this
4991 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
4992 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
4993 message is printed. @value{GDBN} does not look up the parts of the
4994 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
4995 Likewise, the subdirectories of the source path are not searched: if
4996 the source path is @file{/mnt/cross}, and the binary refers to
4997 @file{foo.c}, @value{GDBN} would not find it under
4998 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5000 Plain file names, relative file names with leading directories, file
5001 names containing dots, etc.@: are all treated as described above; for
5002 instance, if the source path is @file{/mnt/cross}, and the source file
5003 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5004 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5005 that---@file{/mnt/cross/foo.c}.
5007 Note that the executable search path is @emph{not} used to locate the
5008 source files. Neither is the current working directory, unless it
5009 happens to be in the source path.
5011 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5012 any information it has cached about where source files are found and where
5013 each line is in the file.
5017 When you start @value{GDBN}, its source path includes only @samp{cdir}
5018 and @samp{cwd}, in that order.
5019 To add other directories, use the @code{directory} command.
5022 @item directory @var{dirname} @dots{}
5023 @item dir @var{dirname} @dots{}
5024 Add directory @var{dirname} to the front of the source path. Several
5025 directory names may be given to this command, separated by @samp{:}
5026 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5027 part of absolute file names) or
5028 whitespace. You may specify a directory that is already in the source
5029 path; this moves it forward, so @value{GDBN} searches it sooner.
5033 @vindex $cdir@r{, convenience variable}
5034 @vindex $cwdr@r{, convenience variable}
5035 @cindex compilation directory
5036 @cindex current directory
5037 @cindex working directory
5038 @cindex directory, current
5039 @cindex directory, compilation
5040 You can use the string @samp{$cdir} to refer to the compilation
5041 directory (if one is recorded), and @samp{$cwd} to refer to the current
5042 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5043 tracks the current working directory as it changes during your @value{GDBN}
5044 session, while the latter is immediately expanded to the current
5045 directory at the time you add an entry to the source path.
5048 Reset the source path to empty again. This requires confirmation.
5050 @c RET-repeat for @code{directory} is explicitly disabled, but since
5051 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5053 @item show directories
5054 @kindex show directories
5055 Print the source path: show which directories it contains.
5058 If your source path is cluttered with directories that are no longer of
5059 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
5060 versions of source. You can correct the situation as follows:
5064 Use @code{directory} with no argument to reset the source path to empty.
5067 Use @code{directory} with suitable arguments to reinstall the
5068 directories you want in the source path. You can add all the
5069 directories in one command.
5073 @section Source and machine code
5074 @cindex source line and its code address
5076 You can use the command @code{info line} to map source lines to program
5077 addresses (and vice versa), and the command @code{disassemble} to display
5078 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
5079 mode, the @code{info line} command causes the arrow to point to the
5080 line specified. Also, @code{info line} prints addresses in symbolic form as
5085 @item info line @var{linespec}
5086 Print the starting and ending addresses of the compiled code for
5087 source line @var{linespec}. You can specify source lines in any of
5088 the ways understood by the @code{list} command (@pxref{List, ,Printing
5092 For example, we can use @code{info line} to discover the location of
5093 the object code for the first line of function
5094 @code{m4_changequote}:
5096 @c FIXME: I think this example should also show the addresses in
5097 @c symbolic form, as they usually would be displayed.
5099 (@value{GDBP}) info line m4_changequote
5100 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
5104 @cindex code address and its source line
5105 We can also inquire (using @code{*@var{addr}} as the form for
5106 @var{linespec}) what source line covers a particular address:
5108 (@value{GDBP}) info line *0x63ff
5109 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
5112 @cindex @code{$_} and @code{info line}
5113 @cindex @code{x} command, default address
5114 @kindex x@r{(examine), and} info line
5115 After @code{info line}, the default address for the @code{x} command
5116 is changed to the starting address of the line, so that @samp{x/i} is
5117 sufficient to begin examining the machine code (@pxref{Memory,
5118 ,Examining memory}). Also, this address is saved as the value of the
5119 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
5124 @cindex assembly instructions
5125 @cindex instructions, assembly
5126 @cindex machine instructions
5127 @cindex listing machine instructions
5129 This specialized command dumps a range of memory as machine
5130 instructions. The default memory range is the function surrounding the
5131 program counter of the selected frame. A single argument to this
5132 command is a program counter value; @value{GDBN} dumps the function
5133 surrounding this value. Two arguments specify a range of addresses
5134 (first inclusive, second exclusive) to dump.
5137 The following example shows the disassembly of a range of addresses of
5138 HP PA-RISC 2.0 code:
5141 (@value{GDBP}) disas 0x32c4 0x32e4
5142 Dump of assembler code from 0x32c4 to 0x32e4:
5143 0x32c4 <main+204>: addil 0,dp
5144 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
5145 0x32cc <main+212>: ldil 0x3000,r31
5146 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
5147 0x32d4 <main+220>: ldo 0(r31),rp
5148 0x32d8 <main+224>: addil -0x800,dp
5149 0x32dc <main+228>: ldo 0x588(r1),r26
5150 0x32e0 <main+232>: ldil 0x3000,r31
5151 End of assembler dump.
5154 Some architectures have more than one commonly-used set of instruction
5155 mnemonics or other syntax.
5157 For programs that were dynamically linked and use shared libraries,
5158 instructions that call functions or branch to locations in the shared
5159 libraries might show a seemingly bogus location---it's actually a
5160 location of the relocation table. On some architectures, @value{GDBN}
5161 might be able to resolve these to actual function names.
5164 @kindex set disassembly-flavor
5165 @cindex Intel disassembly flavor
5166 @cindex AT&T disassembly flavor
5167 @item set disassembly-flavor @var{instruction-set}
5168 Select the instruction set to use when disassembling the
5169 program via the @code{disassemble} or @code{x/i} commands.
5171 Currently this command is only defined for the Intel x86 family. You
5172 can set @var{instruction-set} to either @code{intel} or @code{att}.
5173 The default is @code{att}, the AT&T flavor used by default by Unix
5174 assemblers for x86-based targets.
5176 @kindex show disassembly-flavor
5177 @item show disassembly-flavor
5178 Show the current setting of the disassembly flavor.
5183 @chapter Examining Data
5185 @cindex printing data
5186 @cindex examining data
5189 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
5190 @c document because it is nonstandard... Under Epoch it displays in a
5191 @c different window or something like that.
5192 The usual way to examine data in your program is with the @code{print}
5193 command (abbreviated @code{p}), or its synonym @code{inspect}. It
5194 evaluates and prints the value of an expression of the language your
5195 program is written in (@pxref{Languages, ,Using @value{GDBN} with
5196 Different Languages}).
5199 @item print @var{expr}
5200 @itemx print /@var{f} @var{expr}
5201 @var{expr} is an expression (in the source language). By default the
5202 value of @var{expr} is printed in a format appropriate to its data type;
5203 you can choose a different format by specifying @samp{/@var{f}}, where
5204 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
5208 @itemx print /@var{f}
5209 @cindex reprint the last value
5210 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
5211 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
5212 conveniently inspect the same value in an alternative format.
5215 A more low-level way of examining data is with the @code{x} command.
5216 It examines data in memory at a specified address and prints it in a
5217 specified format. @xref{Memory, ,Examining memory}.
5219 If you are interested in information about types, or about how the
5220 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
5221 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
5225 * Expressions:: Expressions
5226 * Variables:: Program variables
5227 * Arrays:: Artificial arrays
5228 * Output Formats:: Output formats
5229 * Memory:: Examining memory
5230 * Auto Display:: Automatic display
5231 * Print Settings:: Print settings
5232 * Value History:: Value history
5233 * Convenience Vars:: Convenience variables
5234 * Registers:: Registers
5235 * Floating Point Hardware:: Floating point hardware
5236 * Vector Unit:: Vector Unit
5237 * OS Information:: Auxiliary data provided by operating system
5238 * Memory Region Attributes:: Memory region attributes
5239 * Dump/Restore Files:: Copy between memory and a file
5240 * Core File Generation:: Cause a program dump its core
5241 * Character Sets:: Debugging programs that use a different
5242 character set than GDB does
5243 * Caching Remote Data:: Data caching for remote targets
5247 @section Expressions
5250 @code{print} and many other @value{GDBN} commands accept an expression and
5251 compute its value. Any kind of constant, variable or operator defined
5252 by the programming language you are using is valid in an expression in
5253 @value{GDBN}. This includes conditional expressions, function calls,
5254 casts, and string constants. It also includes preprocessor macros, if
5255 you compiled your program to include this information; see
5258 @cindex arrays in expressions
5259 @value{GDBN} supports array constants in expressions input by
5260 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
5261 you can use the command @code{print @{1, 2, 3@}} to build up an array in
5262 memory that is @code{malloc}ed in the target program.
5264 Because C is so widespread, most of the expressions shown in examples in
5265 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
5266 Languages}, for information on how to use expressions in other
5269 In this section, we discuss operators that you can use in @value{GDBN}
5270 expressions regardless of your programming language.
5272 @cindex casts, in expressions
5273 Casts are supported in all languages, not just in C, because it is so
5274 useful to cast a number into a pointer in order to examine a structure
5275 at that address in memory.
5276 @c FIXME: casts supported---Mod2 true?
5278 @value{GDBN} supports these operators, in addition to those common
5279 to programming languages:
5283 @samp{@@} is a binary operator for treating parts of memory as arrays.
5284 @xref{Arrays, ,Artificial arrays}, for more information.
5287 @samp{::} allows you to specify a variable in terms of the file or
5288 function where it is defined. @xref{Variables, ,Program variables}.
5290 @cindex @{@var{type}@}
5291 @cindex type casting memory
5292 @cindex memory, viewing as typed object
5293 @cindex casts, to view memory
5294 @item @{@var{type}@} @var{addr}
5295 Refers to an object of type @var{type} stored at address @var{addr} in
5296 memory. @var{addr} may be any expression whose value is an integer or
5297 pointer (but parentheses are required around binary operators, just as in
5298 a cast). This construct is allowed regardless of what kind of data is
5299 normally supposed to reside at @var{addr}.
5303 @section Program variables
5305 The most common kind of expression to use is the name of a variable
5308 Variables in expressions are understood in the selected stack frame
5309 (@pxref{Selection, ,Selecting a frame}); they must be either:
5313 global (or file-static)
5320 visible according to the scope rules of the
5321 programming language from the point of execution in that frame
5324 @noindent This means that in the function
5339 you can examine and use the variable @code{a} whenever your program is
5340 executing within the function @code{foo}, but you can only use or
5341 examine the variable @code{b} while your program is executing inside
5342 the block where @code{b} is declared.
5344 @cindex variable name conflict
5345 There is an exception: you can refer to a variable or function whose
5346 scope is a single source file even if the current execution point is not
5347 in this file. But it is possible to have more than one such variable or
5348 function with the same name (in different source files). If that
5349 happens, referring to that name has unpredictable effects. If you wish,
5350 you can specify a static variable in a particular function or file,
5351 using the colon-colon (@code{::}) notation:
5353 @cindex colon-colon, context for variables/functions
5355 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
5356 @cindex @code{::}, context for variables/functions
5359 @var{file}::@var{variable}
5360 @var{function}::@var{variable}
5364 Here @var{file} or @var{function} is the name of the context for the
5365 static @var{variable}. In the case of file names, you can use quotes to
5366 make sure @value{GDBN} parses the file name as a single word---for example,
5367 to print a global value of @code{x} defined in @file{f2.c}:
5370 (@value{GDBP}) p 'f2.c'::x
5373 @cindex C@t{++} scope resolution
5374 This use of @samp{::} is very rarely in conflict with the very similar
5375 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
5376 scope resolution operator in @value{GDBN} expressions.
5377 @c FIXME: Um, so what happens in one of those rare cases where it's in
5380 @cindex wrong values
5381 @cindex variable values, wrong
5382 @cindex function entry/exit, wrong values of variables
5383 @cindex optimized code, wrong values of variables
5385 @emph{Warning:} Occasionally, a local variable may appear to have the
5386 wrong value at certain points in a function---just after entry to a new
5387 scope, and just before exit.
5389 You may see this problem when you are stepping by machine instructions.
5390 This is because, on most machines, it takes more than one instruction to
5391 set up a stack frame (including local variable definitions); if you are
5392 stepping by machine instructions, variables may appear to have the wrong
5393 values until the stack frame is completely built. On exit, it usually
5394 also takes more than one machine instruction to destroy a stack frame;
5395 after you begin stepping through that group of instructions, local
5396 variable definitions may be gone.
5398 This may also happen when the compiler does significant optimizations.
5399 To be sure of always seeing accurate values, turn off all optimization
5402 @cindex ``No symbol "foo" in current context''
5403 Another possible effect of compiler optimizations is to optimize
5404 unused variables out of existence, or assign variables to registers (as
5405 opposed to memory addresses). Depending on the support for such cases
5406 offered by the debug info format used by the compiler, @value{GDBN}
5407 might not be able to display values for such local variables. If that
5408 happens, @value{GDBN} will print a message like this:
5411 No symbol "foo" in current context.
5414 To solve such problems, either recompile without optimizations, or use a
5415 different debug info format, if the compiler supports several such
5416 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5417 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5418 produces debug info in a format that is superior to formats such as
5419 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5420 an effective form for debug info. @xref{Debugging Options,,Options
5421 for Debugging Your Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}.
5422 @xref{C, , Debugging C++}, for more info about debug info formats
5423 that are best suited to C@t{++} programs.
5425 If you ask to print an object whose contents are unknown to
5426 @value{GDBN}, e.g., because its data type is not completely specified
5427 by the debug information, @value{GDBN} will say @samp{<incomplete
5428 type>}. @xref{Symbols, incomplete type}, for more about this.
5431 @section Artificial arrays
5433 @cindex artificial array
5435 @kindex @@@r{, referencing memory as an array}
5436 It is often useful to print out several successive objects of the
5437 same type in memory; a section of an array, or an array of
5438 dynamically determined size for which only a pointer exists in the
5441 You can do this by referring to a contiguous span of memory as an
5442 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5443 operand of @samp{@@} should be the first element of the desired array
5444 and be an individual object. The right operand should be the desired length
5445 of the array. The result is an array value whose elements are all of
5446 the type of the left argument. The first element is actually the left
5447 argument; the second element comes from bytes of memory immediately
5448 following those that hold the first element, and so on. Here is an
5449 example. If a program says
5452 int *array = (int *) malloc (len * sizeof (int));
5456 you can print the contents of @code{array} with
5462 The left operand of @samp{@@} must reside in memory. Array values made
5463 with @samp{@@} in this way behave just like other arrays in terms of
5464 subscripting, and are coerced to pointers when used in expressions.
5465 Artificial arrays most often appear in expressions via the value history
5466 (@pxref{Value History, ,Value history}), after printing one out.
5468 Another way to create an artificial array is to use a cast.
5469 This re-interprets a value as if it were an array.
5470 The value need not be in memory:
5472 (@value{GDBP}) p/x (short[2])0x12345678
5473 $1 = @{0x1234, 0x5678@}
5476 As a convenience, if you leave the array length out (as in
5477 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5478 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5480 (@value{GDBP}) p/x (short[])0x12345678
5481 $2 = @{0x1234, 0x5678@}
5484 Sometimes the artificial array mechanism is not quite enough; in
5485 moderately complex data structures, the elements of interest may not
5486 actually be adjacent---for example, if you are interested in the values
5487 of pointers in an array. One useful work-around in this situation is
5488 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5489 variables}) as a counter in an expression that prints the first
5490 interesting value, and then repeat that expression via @key{RET}. For
5491 instance, suppose you have an array @code{dtab} of pointers to
5492 structures, and you are interested in the values of a field @code{fv}
5493 in each structure. Here is an example of what you might type:
5503 @node Output Formats
5504 @section Output formats
5506 @cindex formatted output
5507 @cindex output formats
5508 By default, @value{GDBN} prints a value according to its data type. Sometimes
5509 this is not what you want. For example, you might want to print a number
5510 in hex, or a pointer in decimal. Or you might want to view data in memory
5511 at a certain address as a character string or as an instruction. To do
5512 these things, specify an @dfn{output format} when you print a value.
5514 The simplest use of output formats is to say how to print a value
5515 already computed. This is done by starting the arguments of the
5516 @code{print} command with a slash and a format letter. The format
5517 letters supported are:
5521 Regard the bits of the value as an integer, and print the integer in
5525 Print as integer in signed decimal.
5528 Print as integer in unsigned decimal.
5531 Print as integer in octal.
5534 Print as integer in binary. The letter @samp{t} stands for ``two''.
5535 @footnote{@samp{b} cannot be used because these format letters are also
5536 used with the @code{x} command, where @samp{b} stands for ``byte'';
5537 see @ref{Memory,,Examining memory}.}
5540 @cindex unknown address, locating
5541 @cindex locate address
5542 Print as an address, both absolute in hexadecimal and as an offset from
5543 the nearest preceding symbol. You can use this format used to discover
5544 where (in what function) an unknown address is located:
5547 (@value{GDBP}) p/a 0x54320
5548 $3 = 0x54320 <_initialize_vx+396>
5552 The command @code{info symbol 0x54320} yields similar results.
5553 @xref{Symbols, info symbol}.
5556 Regard as an integer and print it as a character constant. This
5557 prints both the numerical value and its character representation. The
5558 character representation is replaced with the octal escape @samp{\nnn}
5559 for characters outside the 7-bit @sc{ascii} range.
5562 Regard the bits of the value as a floating point number and print
5563 using typical floating point syntax.
5566 For example, to print the program counter in hex (@pxref{Registers}), type
5573 Note that no space is required before the slash; this is because command
5574 names in @value{GDBN} cannot contain a slash.
5576 To reprint the last value in the value history with a different format,
5577 you can use the @code{print} command with just a format and no
5578 expression. For example, @samp{p/x} reprints the last value in hex.
5581 @section Examining memory
5583 You can use the command @code{x} (for ``examine'') to examine memory in
5584 any of several formats, independently of your program's data types.
5586 @cindex examining memory
5588 @kindex x @r{(examine memory)}
5589 @item x/@var{nfu} @var{addr}
5592 Use the @code{x} command to examine memory.
5595 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5596 much memory to display and how to format it; @var{addr} is an
5597 expression giving the address where you want to start displaying memory.
5598 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5599 Several commands set convenient defaults for @var{addr}.
5602 @item @var{n}, the repeat count
5603 The repeat count is a decimal integer; the default is 1. It specifies
5604 how much memory (counting by units @var{u}) to display.
5605 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5608 @item @var{f}, the display format
5609 The display format is one of the formats used by @code{print}
5610 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
5611 @samp{f}), and in addition @samp{s} (for null-terminated strings) and
5612 @samp{i} (for machine instructions). The default is @samp{x}
5613 (hexadecimal) initially. The default changes each time you use either
5614 @code{x} or @code{print}.
5616 @item @var{u}, the unit size
5617 The unit size is any of
5623 Halfwords (two bytes).
5625 Words (four bytes). This is the initial default.
5627 Giant words (eight bytes).
5630 Each time you specify a unit size with @code{x}, that size becomes the
5631 default unit the next time you use @code{x}. (For the @samp{s} and
5632 @samp{i} formats, the unit size is ignored and is normally not written.)
5634 @item @var{addr}, starting display address
5635 @var{addr} is the address where you want @value{GDBN} to begin displaying
5636 memory. The expression need not have a pointer value (though it may);
5637 it is always interpreted as an integer address of a byte of memory.
5638 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5639 @var{addr} is usually just after the last address examined---but several
5640 other commands also set the default address: @code{info breakpoints} (to
5641 the address of the last breakpoint listed), @code{info line} (to the
5642 starting address of a line), and @code{print} (if you use it to display
5643 a value from memory).
5646 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5647 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5648 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5649 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5650 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5652 Since the letters indicating unit sizes are all distinct from the
5653 letters specifying output formats, you do not have to remember whether
5654 unit size or format comes first; either order works. The output
5655 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5656 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5658 Even though the unit size @var{u} is ignored for the formats @samp{s}
5659 and @samp{i}, you might still want to use a count @var{n}; for example,
5660 @samp{3i} specifies that you want to see three machine instructions,
5661 including any operands. The command @code{disassemble} gives an
5662 alternative way of inspecting machine instructions; see @ref{Machine
5663 Code,,Source and machine code}.
5665 All the defaults for the arguments to @code{x} are designed to make it
5666 easy to continue scanning memory with minimal specifications each time
5667 you use @code{x}. For example, after you have inspected three machine
5668 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5669 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5670 the repeat count @var{n} is used again; the other arguments default as
5671 for successive uses of @code{x}.
5673 @cindex @code{$_}, @code{$__}, and value history
5674 The addresses and contents printed by the @code{x} command are not saved
5675 in the value history because there is often too much of them and they
5676 would get in the way. Instead, @value{GDBN} makes these values available for
5677 subsequent use in expressions as values of the convenience variables
5678 @code{$_} and @code{$__}. After an @code{x} command, the last address
5679 examined is available for use in expressions in the convenience variable
5680 @code{$_}. The contents of that address, as examined, are available in
5681 the convenience variable @code{$__}.
5683 If the @code{x} command has a repeat count, the address and contents saved
5684 are from the last memory unit printed; this is not the same as the last
5685 address printed if several units were printed on the last line of output.
5687 @cindex remote memory comparison
5688 @cindex verify remote memory image
5689 When you are debugging a program running on a remote target machine
5690 (@pxref{Remote}), you may wish to verify the program's image in the
5691 remote machine's memory against the executable file you downloaded to
5692 the target. The @code{compare-sections} command is provided for such
5696 @kindex compare-sections
5697 @item compare-sections @r{[}@var{section-name}@r{]}
5698 Compare the data of a loadable section @var{section-name} in the
5699 executable file of the program being debugged with the same section in
5700 the remote machine's memory, and report any mismatches. With no
5701 arguments, compares all loadable sections. This command's
5702 availability depends on the target's support for the @code{"qCRC"}
5707 @section Automatic display
5708 @cindex automatic display
5709 @cindex display of expressions
5711 If you find that you want to print the value of an expression frequently
5712 (to see how it changes), you might want to add it to the @dfn{automatic
5713 display list} so that @value{GDBN} prints its value each time your program stops.
5714 Each expression added to the list is given a number to identify it;
5715 to remove an expression from the list, you specify that number.
5716 The automatic display looks like this:
5720 3: bar[5] = (struct hack *) 0x3804
5724 This display shows item numbers, expressions and their current values. As with
5725 displays you request manually using @code{x} or @code{print}, you can
5726 specify the output format you prefer; in fact, @code{display} decides
5727 whether to use @code{print} or @code{x} depending on how elaborate your
5728 format specification is---it uses @code{x} if you specify a unit size,
5729 or one of the two formats (@samp{i} and @samp{s}) that are only
5730 supported by @code{x}; otherwise it uses @code{print}.
5734 @item display @var{expr}
5735 Add the expression @var{expr} to the list of expressions to display
5736 each time your program stops. @xref{Expressions, ,Expressions}.
5738 @code{display} does not repeat if you press @key{RET} again after using it.
5740 @item display/@var{fmt} @var{expr}
5741 For @var{fmt} specifying only a display format and not a size or
5742 count, add the expression @var{expr} to the auto-display list but
5743 arrange to display it each time in the specified format @var{fmt}.
5744 @xref{Output Formats,,Output formats}.
5746 @item display/@var{fmt} @var{addr}
5747 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5748 number of units, add the expression @var{addr} as a memory address to
5749 be examined each time your program stops. Examining means in effect
5750 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5753 For example, @samp{display/i $pc} can be helpful, to see the machine
5754 instruction about to be executed each time execution stops (@samp{$pc}
5755 is a common name for the program counter; @pxref{Registers, ,Registers}).
5758 @kindex delete display
5760 @item undisplay @var{dnums}@dots{}
5761 @itemx delete display @var{dnums}@dots{}
5762 Remove item numbers @var{dnums} from the list of expressions to display.
5764 @code{undisplay} does not repeat if you press @key{RET} after using it.
5765 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5767 @kindex disable display
5768 @item disable display @var{dnums}@dots{}
5769 Disable the display of item numbers @var{dnums}. A disabled display
5770 item is not printed automatically, but is not forgotten. It may be
5771 enabled again later.
5773 @kindex enable display
5774 @item enable display @var{dnums}@dots{}
5775 Enable display of item numbers @var{dnums}. It becomes effective once
5776 again in auto display of its expression, until you specify otherwise.
5779 Display the current values of the expressions on the list, just as is
5780 done when your program stops.
5782 @kindex info display
5784 Print the list of expressions previously set up to display
5785 automatically, each one with its item number, but without showing the
5786 values. This includes disabled expressions, which are marked as such.
5787 It also includes expressions which would not be displayed right now
5788 because they refer to automatic variables not currently available.
5791 @cindex display disabled out of scope
5792 If a display expression refers to local variables, then it does not make
5793 sense outside the lexical context for which it was set up. Such an
5794 expression is disabled when execution enters a context where one of its
5795 variables is not defined. For example, if you give the command
5796 @code{display last_char} while inside a function with an argument
5797 @code{last_char}, @value{GDBN} displays this argument while your program
5798 continues to stop inside that function. When it stops elsewhere---where
5799 there is no variable @code{last_char}---the display is disabled
5800 automatically. The next time your program stops where @code{last_char}
5801 is meaningful, you can enable the display expression once again.
5803 @node Print Settings
5804 @section Print settings
5806 @cindex format options
5807 @cindex print settings
5808 @value{GDBN} provides the following ways to control how arrays, structures,
5809 and symbols are printed.
5812 These settings are useful for debugging programs in any language:
5816 @item set print address
5817 @itemx set print address on
5818 @cindex print/don't print memory addresses
5819 @value{GDBN} prints memory addresses showing the location of stack
5820 traces, structure values, pointer values, breakpoints, and so forth,
5821 even when it also displays the contents of those addresses. The default
5822 is @code{on}. For example, this is what a stack frame display looks like with
5823 @code{set print address on}:
5828 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
5830 530 if (lquote != def_lquote)
5834 @item set print address off
5835 Do not print addresses when displaying their contents. For example,
5836 this is the same stack frame displayed with @code{set print address off}:
5840 (@value{GDBP}) set print addr off
5842 #0 set_quotes (lq="<<", rq=">>") at input.c:530
5843 530 if (lquote != def_lquote)
5847 You can use @samp{set print address off} to eliminate all machine
5848 dependent displays from the @value{GDBN} interface. For example, with
5849 @code{print address off}, you should get the same text for backtraces on
5850 all machines---whether or not they involve pointer arguments.
5853 @item show print address
5854 Show whether or not addresses are to be printed.
5857 When @value{GDBN} prints a symbolic address, it normally prints the
5858 closest earlier symbol plus an offset. If that symbol does not uniquely
5859 identify the address (for example, it is a name whose scope is a single
5860 source file), you may need to clarify. One way to do this is with
5861 @code{info line}, for example @samp{info line *0x4537}. Alternately,
5862 you can set @value{GDBN} to print the source file and line number when
5863 it prints a symbolic address:
5866 @item set print symbol-filename on
5867 @cindex source file and line of a symbol
5868 @cindex symbol, source file and line
5869 Tell @value{GDBN} to print the source file name and line number of a
5870 symbol in the symbolic form of an address.
5872 @item set print symbol-filename off
5873 Do not print source file name and line number of a symbol. This is the
5876 @item show print symbol-filename
5877 Show whether or not @value{GDBN} will print the source file name and
5878 line number of a symbol in the symbolic form of an address.
5881 Another situation where it is helpful to show symbol filenames and line
5882 numbers is when disassembling code; @value{GDBN} shows you the line
5883 number and source file that corresponds to each instruction.
5885 Also, you may wish to see the symbolic form only if the address being
5886 printed is reasonably close to the closest earlier symbol:
5889 @item set print max-symbolic-offset @var{max-offset}
5890 @cindex maximum value for offset of closest symbol
5891 Tell @value{GDBN} to only display the symbolic form of an address if the
5892 offset between the closest earlier symbol and the address is less than
5893 @var{max-offset}. The default is 0, which tells @value{GDBN}
5894 to always print the symbolic form of an address if any symbol precedes it.
5896 @item show print max-symbolic-offset
5897 Ask how large the maximum offset is that @value{GDBN} prints in a
5901 @cindex wild pointer, interpreting
5902 @cindex pointer, finding referent
5903 If you have a pointer and you are not sure where it points, try
5904 @samp{set print symbol-filename on}. Then you can determine the name
5905 and source file location of the variable where it points, using
5906 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
5907 For example, here @value{GDBN} shows that a variable @code{ptt} points
5908 at another variable @code{t}, defined in @file{hi2.c}:
5911 (@value{GDBP}) set print symbol-filename on
5912 (@value{GDBP}) p/a ptt
5913 $4 = 0xe008 <t in hi2.c>
5917 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
5918 does not show the symbol name and filename of the referent, even with
5919 the appropriate @code{set print} options turned on.
5922 Other settings control how different kinds of objects are printed:
5925 @item set print array
5926 @itemx set print array on
5927 @cindex pretty print arrays
5928 Pretty print arrays. This format is more convenient to read,
5929 but uses more space. The default is off.
5931 @item set print array off
5932 Return to compressed format for arrays.
5934 @item show print array
5935 Show whether compressed or pretty format is selected for displaying
5938 @cindex print array indexes
5939 @item set print array-indexes
5940 @itemx set print array-indexes on
5941 Print the index of each element when displaying arrays. May be more
5942 convenient to locate a given element in the array or quickly find the
5943 index of a given element in that printed array. The default is off.
5945 @item set print array-indexes off
5946 Stop printing element indexes when displaying arrays.
5948 @item show print array-indexes
5949 Show whether the index of each element is printed when displaying
5952 @item set print elements @var{number-of-elements}
5953 @cindex number of array elements to print
5954 @cindex limit on number of printed array elements
5955 Set a limit on how many elements of an array @value{GDBN} will print.
5956 If @value{GDBN} is printing a large array, it stops printing after it has
5957 printed the number of elements set by the @code{set print elements} command.
5958 This limit also applies to the display of strings.
5959 When @value{GDBN} starts, this limit is set to 200.
5960 Setting @var{number-of-elements} to zero means that the printing is unlimited.
5962 @item show print elements
5963 Display the number of elements of a large array that @value{GDBN} will print.
5964 If the number is 0, then the printing is unlimited.
5966 @item set print repeats
5967 @cindex repeated array elements
5968 Set the threshold for suppressing display of repeated array
5969 elelments. When the number of consecutive identical elements of an
5970 array exceeds the threshold, @value{GDBN} prints the string
5971 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
5972 identical repetitions, instead of displaying the identical elements
5973 themselves. Setting the threshold to zero will cause all elements to
5974 be individually printed. The default threshold is 10.
5976 @item show print repeats
5977 Display the current threshold for printing repeated identical
5980 @item set print null-stop
5981 @cindex @sc{null} elements in arrays
5982 Cause @value{GDBN} to stop printing the characters of an array when the first
5983 @sc{null} is encountered. This is useful when large arrays actually
5984 contain only short strings.
5987 @item show print null-stop
5988 Show whether @value{GDBN} stops printing an array on the first
5989 @sc{null} character.
5991 @item set print pretty on
5992 @cindex print structures in indented form
5993 @cindex indentation in structure display
5994 Cause @value{GDBN} to print structures in an indented format with one member
5995 per line, like this:
6010 @item set print pretty off
6011 Cause @value{GDBN} to print structures in a compact format, like this:
6015 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
6016 meat = 0x54 "Pork"@}
6021 This is the default format.
6023 @item show print pretty
6024 Show which format @value{GDBN} is using to print structures.
6026 @item set print sevenbit-strings on
6027 @cindex eight-bit characters in strings
6028 @cindex octal escapes in strings
6029 Print using only seven-bit characters; if this option is set,
6030 @value{GDBN} displays any eight-bit characters (in strings or
6031 character values) using the notation @code{\}@var{nnn}. This setting is
6032 best if you are working in English (@sc{ascii}) and you use the
6033 high-order bit of characters as a marker or ``meta'' bit.
6035 @item set print sevenbit-strings off
6036 Print full eight-bit characters. This allows the use of more
6037 international character sets, and is the default.
6039 @item show print sevenbit-strings
6040 Show whether or not @value{GDBN} is printing only seven-bit characters.
6042 @item set print union on
6043 @cindex unions in structures, printing
6044 Tell @value{GDBN} to print unions which are contained in structures
6045 and other unions. This is the default setting.
6047 @item set print union off
6048 Tell @value{GDBN} not to print unions which are contained in
6049 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
6052 @item show print union
6053 Ask @value{GDBN} whether or not it will print unions which are contained in
6054 structures and other unions.
6056 For example, given the declarations
6059 typedef enum @{Tree, Bug@} Species;
6060 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
6061 typedef enum @{Caterpillar, Cocoon, Butterfly@}
6072 struct thing foo = @{Tree, @{Acorn@}@};
6076 with @code{set print union on} in effect @samp{p foo} would print
6079 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
6083 and with @code{set print union off} in effect it would print
6086 $1 = @{it = Tree, form = @{...@}@}
6090 @code{set print union} affects programs written in C-like languages
6096 These settings are of interest when debugging C@t{++} programs:
6099 @cindex demangling C@t{++} names
6100 @item set print demangle
6101 @itemx set print demangle on
6102 Print C@t{++} names in their source form rather than in the encoded
6103 (``mangled'') form passed to the assembler and linker for type-safe
6104 linkage. The default is on.
6106 @item show print demangle
6107 Show whether C@t{++} names are printed in mangled or demangled form.
6109 @item set print asm-demangle
6110 @itemx set print asm-demangle on
6111 Print C@t{++} names in their source form rather than their mangled form, even
6112 in assembler code printouts such as instruction disassemblies.
6115 @item show print asm-demangle
6116 Show whether C@t{++} names in assembly listings are printed in mangled
6119 @cindex C@t{++} symbol decoding style
6120 @cindex symbol decoding style, C@t{++}
6121 @kindex set demangle-style
6122 @item set demangle-style @var{style}
6123 Choose among several encoding schemes used by different compilers to
6124 represent C@t{++} names. The choices for @var{style} are currently:
6128 Allow @value{GDBN} to choose a decoding style by inspecting your program.
6131 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
6132 This is the default.
6135 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
6138 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
6141 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
6142 @strong{Warning:} this setting alone is not sufficient to allow
6143 debugging @code{cfront}-generated executables. @value{GDBN} would
6144 require further enhancement to permit that.
6147 If you omit @var{style}, you will see a list of possible formats.
6149 @item show demangle-style
6150 Display the encoding style currently in use for decoding C@t{++} symbols.
6152 @item set print object
6153 @itemx set print object on
6154 @cindex derived type of an object, printing
6155 @cindex display derived types
6156 When displaying a pointer to an object, identify the @emph{actual}
6157 (derived) type of the object rather than the @emph{declared} type, using
6158 the virtual function table.
6160 @item set print object off
6161 Display only the declared type of objects, without reference to the
6162 virtual function table. This is the default setting.
6164 @item show print object
6165 Show whether actual, or declared, object types are displayed.
6167 @item set print static-members
6168 @itemx set print static-members on
6169 @cindex static members of C@t{++} objects
6170 Print static members when displaying a C@t{++} object. The default is on.
6172 @item set print static-members off
6173 Do not print static members when displaying a C@t{++} object.
6175 @item show print static-members
6176 Show whether C@t{++} static members are printed or not.
6178 @item set print pascal_static-members
6179 @itemx set print pascal_static-members on
6180 @cindex static members of Pacal objects
6181 @cindex Pacal objects, static members display
6182 Print static members when displaying a Pascal object. The default is on.
6184 @item set print pascal_static-members off
6185 Do not print static members when displaying a Pascal object.
6187 @item show print pascal_static-members
6188 Show whether Pascal static members are printed or not.
6190 @c These don't work with HP ANSI C++ yet.
6191 @item set print vtbl
6192 @itemx set print vtbl on
6193 @cindex pretty print C@t{++} virtual function tables
6194 @cindex virtual functions (C@t{++}) display
6195 @cindex VTBL display
6196 Pretty print C@t{++} virtual function tables. The default is off.
6197 (The @code{vtbl} commands do not work on programs compiled with the HP
6198 ANSI C@t{++} compiler (@code{aCC}).)
6200 @item set print vtbl off
6201 Do not pretty print C@t{++} virtual function tables.
6203 @item show print vtbl
6204 Show whether C@t{++} virtual function tables are pretty printed, or not.
6208 @section Value history
6210 @cindex value history
6211 @cindex history of values printed by @value{GDBN}
6212 Values printed by the @code{print} command are saved in the @value{GDBN}
6213 @dfn{value history}. This allows you to refer to them in other expressions.
6214 Values are kept until the symbol table is re-read or discarded
6215 (for example with the @code{file} or @code{symbol-file} commands).
6216 When the symbol table changes, the value history is discarded,
6217 since the values may contain pointers back to the types defined in the
6222 @cindex history number
6223 The values printed are given @dfn{history numbers} by which you can
6224 refer to them. These are successive integers starting with one.
6225 @code{print} shows you the history number assigned to a value by
6226 printing @samp{$@var{num} = } before the value; here @var{num} is the
6229 To refer to any previous value, use @samp{$} followed by the value's
6230 history number. The way @code{print} labels its output is designed to
6231 remind you of this. Just @code{$} refers to the most recent value in
6232 the history, and @code{$$} refers to the value before that.
6233 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
6234 is the value just prior to @code{$$}, @code{$$1} is equivalent to
6235 @code{$$}, and @code{$$0} is equivalent to @code{$}.
6237 For example, suppose you have just printed a pointer to a structure and
6238 want to see the contents of the structure. It suffices to type
6244 If you have a chain of structures where the component @code{next} points
6245 to the next one, you can print the contents of the next one with this:
6252 You can print successive links in the chain by repeating this
6253 command---which you can do by just typing @key{RET}.
6255 Note that the history records values, not expressions. If the value of
6256 @code{x} is 4 and you type these commands:
6264 then the value recorded in the value history by the @code{print} command
6265 remains 4 even though the value of @code{x} has changed.
6270 Print the last ten values in the value history, with their item numbers.
6271 This is like @samp{p@ $$9} repeated ten times, except that @code{show
6272 values} does not change the history.
6274 @item show values @var{n}
6275 Print ten history values centered on history item number @var{n}.
6278 Print ten history values just after the values last printed. If no more
6279 values are available, @code{show values +} produces no display.
6282 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
6283 same effect as @samp{show values +}.
6285 @node Convenience Vars
6286 @section Convenience variables
6288 @cindex convenience variables
6289 @cindex user-defined variables
6290 @value{GDBN} provides @dfn{convenience variables} that you can use within
6291 @value{GDBN} to hold on to a value and refer to it later. These variables
6292 exist entirely within @value{GDBN}; they are not part of your program, and
6293 setting a convenience variable has no direct effect on further execution
6294 of your program. That is why you can use them freely.
6296 Convenience variables are prefixed with @samp{$}. Any name preceded by
6297 @samp{$} can be used for a convenience variable, unless it is one of
6298 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
6299 (Value history references, in contrast, are @emph{numbers} preceded
6300 by @samp{$}. @xref{Value History, ,Value history}.)
6302 You can save a value in a convenience variable with an assignment
6303 expression, just as you would set a variable in your program.
6307 set $foo = *object_ptr
6311 would save in @code{$foo} the value contained in the object pointed to by
6314 Using a convenience variable for the first time creates it, but its
6315 value is @code{void} until you assign a new value. You can alter the
6316 value with another assignment at any time.
6318 Convenience variables have no fixed types. You can assign a convenience
6319 variable any type of value, including structures and arrays, even if
6320 that variable already has a value of a different type. The convenience
6321 variable, when used as an expression, has the type of its current value.
6324 @kindex show convenience
6325 @cindex show all user variables
6326 @item show convenience
6327 Print a list of convenience variables used so far, and their values.
6328 Abbreviated @code{show conv}.
6330 @kindex init-if-undefined
6331 @cindex convenience variables, initializing
6332 @item init-if-undefined $@var{variable} = @var{expression}
6333 Set a convenience variable if it has not already been set. This is useful
6334 for user-defined commands that keep some state. It is similar, in concept,
6335 to using local static variables with initializers in C (except that
6336 convenience variables are global). It can also be used to allow users to
6337 override default values used in a command script.
6339 If the variable is already defined then the expression is not evaluated so
6340 any side-effects do not occur.
6343 One of the ways to use a convenience variable is as a counter to be
6344 incremented or a pointer to be advanced. For example, to print
6345 a field from successive elements of an array of structures:
6349 print bar[$i++]->contents
6353 Repeat that command by typing @key{RET}.
6355 Some convenience variables are created automatically by @value{GDBN} and given
6356 values likely to be useful.
6359 @vindex $_@r{, convenience variable}
6361 The variable @code{$_} is automatically set by the @code{x} command to
6362 the last address examined (@pxref{Memory, ,Examining memory}). Other
6363 commands which provide a default address for @code{x} to examine also
6364 set @code{$_} to that address; these commands include @code{info line}
6365 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
6366 except when set by the @code{x} command, in which case it is a pointer
6367 to the type of @code{$__}.
6369 @vindex $__@r{, convenience variable}
6371 The variable @code{$__} is automatically set by the @code{x} command
6372 to the value found in the last address examined. Its type is chosen
6373 to match the format in which the data was printed.
6376 @vindex $_exitcode@r{, convenience variable}
6377 The variable @code{$_exitcode} is automatically set to the exit code when
6378 the program being debugged terminates.
6381 On HP-UX systems, if you refer to a function or variable name that
6382 begins with a dollar sign, @value{GDBN} searches for a user or system
6383 name first, before it searches for a convenience variable.
6389 You can refer to machine register contents, in expressions, as variables
6390 with names starting with @samp{$}. The names of registers are different
6391 for each machine; use @code{info registers} to see the names used on
6395 @kindex info registers
6396 @item info registers
6397 Print the names and values of all registers except floating-point
6398 and vector registers (in the selected stack frame).
6400 @kindex info all-registers
6401 @cindex floating point registers
6402 @item info all-registers
6403 Print the names and values of all registers, including floating-point
6404 and vector registers (in the selected stack frame).
6406 @item info registers @var{regname} @dots{}
6407 Print the @dfn{relativized} value of each specified register @var{regname}.
6408 As discussed in detail below, register values are normally relative to
6409 the selected stack frame. @var{regname} may be any register name valid on
6410 the machine you are using, with or without the initial @samp{$}.
6413 @cindex stack pointer register
6414 @cindex program counter register
6415 @cindex process status register
6416 @cindex frame pointer register
6417 @cindex standard registers
6418 @value{GDBN} has four ``standard'' register names that are available (in
6419 expressions) on most machines---whenever they do not conflict with an
6420 architecture's canonical mnemonics for registers. The register names
6421 @code{$pc} and @code{$sp} are used for the program counter register and
6422 the stack pointer. @code{$fp} is used for a register that contains a
6423 pointer to the current stack frame, and @code{$ps} is used for a
6424 register that contains the processor status. For example,
6425 you could print the program counter in hex with
6432 or print the instruction to be executed next with
6439 or add four to the stack pointer@footnote{This is a way of removing
6440 one word from the stack, on machines where stacks grow downward in
6441 memory (most machines, nowadays). This assumes that the innermost
6442 stack frame is selected; setting @code{$sp} is not allowed when other
6443 stack frames are selected. To pop entire frames off the stack,
6444 regardless of machine architecture, use @code{return};
6445 see @ref{Returning, ,Returning from a function}.} with
6451 Whenever possible, these four standard register names are available on
6452 your machine even though the machine has different canonical mnemonics,
6453 so long as there is no conflict. The @code{info registers} command
6454 shows the canonical names. For example, on the SPARC, @code{info
6455 registers} displays the processor status register as @code{$psr} but you
6456 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
6457 is an alias for the @sc{eflags} register.
6459 @value{GDBN} always considers the contents of an ordinary register as an
6460 integer when the register is examined in this way. Some machines have
6461 special registers which can hold nothing but floating point; these
6462 registers are considered to have floating point values. There is no way
6463 to refer to the contents of an ordinary register as floating point value
6464 (although you can @emph{print} it as a floating point value with
6465 @samp{print/f $@var{regname}}).
6467 Some registers have distinct ``raw'' and ``virtual'' data formats. This
6468 means that the data format in which the register contents are saved by
6469 the operating system is not the same one that your program normally
6470 sees. For example, the registers of the 68881 floating point
6471 coprocessor are always saved in ``extended'' (raw) format, but all C
6472 programs expect to work with ``double'' (virtual) format. In such
6473 cases, @value{GDBN} normally works with the virtual format only (the format
6474 that makes sense for your program), but the @code{info registers} command
6475 prints the data in both formats.
6477 @cindex SSE registers (x86)
6478 @cindex MMX registers (x86)
6479 Some machines have special registers whose contents can be interpreted
6480 in several different ways. For example, modern x86-based machines
6481 have SSE and MMX registers that can hold several values packed
6482 together in several different formats. @value{GDBN} refers to such
6483 registers in @code{struct} notation:
6486 (@value{GDBP}) print $xmm1
6488 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
6489 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
6490 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
6491 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
6492 v4_int32 = @{0, 20657912, 11, 13@},
6493 v2_int64 = @{88725056443645952, 55834574859@},
6494 uint128 = 0x0000000d0000000b013b36f800000000
6499 To set values of such registers, you need to tell @value{GDBN} which
6500 view of the register you wish to change, as if you were assigning
6501 value to a @code{struct} member:
6504 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
6507 Normally, register values are relative to the selected stack frame
6508 (@pxref{Selection, ,Selecting a frame}). This means that you get the
6509 value that the register would contain if all stack frames farther in
6510 were exited and their saved registers restored. In order to see the
6511 true contents of hardware registers, you must select the innermost
6512 frame (with @samp{frame 0}).
6514 However, @value{GDBN} must deduce where registers are saved, from the machine
6515 code generated by your compiler. If some registers are not saved, or if
6516 @value{GDBN} is unable to locate the saved registers, the selected stack
6517 frame makes no difference.
6519 @node Floating Point Hardware
6520 @section Floating point hardware
6521 @cindex floating point
6523 Depending on the configuration, @value{GDBN} may be able to give
6524 you more information about the status of the floating point hardware.
6529 Display hardware-dependent information about the floating
6530 point unit. The exact contents and layout vary depending on the
6531 floating point chip. Currently, @samp{info float} is supported on
6532 the ARM and x86 machines.
6536 @section Vector Unit
6539 Depending on the configuration, @value{GDBN} may be able to give you
6540 more information about the status of the vector unit.
6545 Display information about the vector unit. The exact contents and
6546 layout vary depending on the hardware.
6549 @node OS Information
6550 @section Operating system auxiliary information
6551 @cindex OS information
6553 @value{GDBN} provides interfaces to useful OS facilities that can help
6554 you debug your program.
6556 @cindex @code{ptrace} system call
6557 @cindex @code{struct user} contents
6558 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
6559 machines), it interfaces with the inferior via the @code{ptrace}
6560 system call. The operating system creates a special sata structure,
6561 called @code{struct user}, for this interface. You can use the
6562 command @code{info udot} to display the contents of this data
6568 Display the contents of the @code{struct user} maintained by the OS
6569 kernel for the program being debugged. @value{GDBN} displays the
6570 contents of @code{struct user} as a list of hex numbers, similar to
6571 the @code{examine} command.
6574 @cindex auxiliary vector
6575 @cindex vector, auxiliary
6576 Some operating systems supply an @dfn{auxiliary vector} to programs at
6577 startup. This is akin to the arguments and environment that you
6578 specify for a program, but contains a system-dependent variety of
6579 binary values that tell system libraries important details about the
6580 hardware, operating system, and process. Each value's purpose is
6581 identified by an integer tag; the meanings are well-known but system-specific.
6582 Depending on the configuration and operating system facilities,
6583 @value{GDBN} may be able to show you this information. For remote
6584 targets, this functionality may further depend on the remote stub's
6585 support of the @samp{qPart:auxv:read} packet, see @ref{Remote
6586 configuration, auxiliary vector}.
6591 Display the auxiliary vector of the inferior, which can be either a
6592 live process or a core dump file. @value{GDBN} prints each tag value
6593 numerically, and also shows names and text descriptions for recognized
6594 tags. Some values in the vector are numbers, some bit masks, and some
6595 pointers to strings or other data. @value{GDBN} displays each value in the
6596 most appropriate form for a recognized tag, and in hexadecimal for
6597 an unrecognized tag.
6601 @node Memory Region Attributes
6602 @section Memory region attributes
6603 @cindex memory region attributes
6605 @dfn{Memory region attributes} allow you to describe special handling
6606 required by regions of your target's memory. @value{GDBN} uses attributes
6607 to determine whether to allow certain types of memory accesses; whether to
6608 use specific width accesses; and whether to cache target memory.
6610 Defined memory regions can be individually enabled and disabled. When a
6611 memory region is disabled, @value{GDBN} uses the default attributes when
6612 accessing memory in that region. Similarly, if no memory regions have
6613 been defined, @value{GDBN} uses the default attributes when accessing
6616 When a memory region is defined, it is given a number to identify it;
6617 to enable, disable, or remove a memory region, you specify that number.
6621 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
6622 Define a memory region bounded by @var{lower} and @var{upper} with
6623 attributes @var{attributes}@dots{}, and add it to the list of regions
6624 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
6625 case: it is treated as the the target's maximum memory address.
6626 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
6629 @item delete mem @var{nums}@dots{}
6630 Remove memory regions @var{nums}@dots{} from the list of regions
6631 monitored by @value{GDBN}.
6634 @item disable mem @var{nums}@dots{}
6635 Disable monitoring of memory regions @var{nums}@dots{}.
6636 A disabled memory region is not forgotten.
6637 It may be enabled again later.
6640 @item enable mem @var{nums}@dots{}
6641 Enable monitoring of memory regions @var{nums}@dots{}.
6645 Print a table of all defined memory regions, with the following columns
6649 @item Memory Region Number
6650 @item Enabled or Disabled.
6651 Enabled memory regions are marked with @samp{y}.
6652 Disabled memory regions are marked with @samp{n}.
6655 The address defining the inclusive lower bound of the memory region.
6658 The address defining the exclusive upper bound of the memory region.
6661 The list of attributes set for this memory region.
6666 @subsection Attributes
6668 @subsubsection Memory Access Mode
6669 The access mode attributes set whether @value{GDBN} may make read or
6670 write accesses to a memory region.
6672 While these attributes prevent @value{GDBN} from performing invalid
6673 memory accesses, they do nothing to prevent the target system, I/O DMA,
6674 etc.@: from accessing memory.
6678 Memory is read only.
6680 Memory is write only.
6682 Memory is read/write. This is the default.
6685 @subsubsection Memory Access Size
6686 The acccess size attributes tells @value{GDBN} to use specific sized
6687 accesses in the memory region. Often memory mapped device registers
6688 require specific sized accesses. If no access size attribute is
6689 specified, @value{GDBN} may use accesses of any size.
6693 Use 8 bit memory accesses.
6695 Use 16 bit memory accesses.
6697 Use 32 bit memory accesses.
6699 Use 64 bit memory accesses.
6702 @c @subsubsection Hardware/Software Breakpoints
6703 @c The hardware/software breakpoint attributes set whether @value{GDBN}
6704 @c will use hardware or software breakpoints for the internal breakpoints
6705 @c used by the step, next, finish, until, etc. commands.
6709 @c Always use hardware breakpoints
6710 @c @item swbreak (default)
6713 @subsubsection Data Cache
6714 The data cache attributes set whether @value{GDBN} will cache target
6715 memory. While this generally improves performance by reducing debug
6716 protocol overhead, it can lead to incorrect results because @value{GDBN}
6717 does not know about volatile variables or memory mapped device
6722 Enable @value{GDBN} to cache target memory.
6724 Disable @value{GDBN} from caching target memory. This is the default.
6727 @c @subsubsection Memory Write Verification
6728 @c The memory write verification attributes set whether @value{GDBN}
6729 @c will re-reads data after each write to verify the write was successful.
6733 @c @item noverify (default)
6736 @node Dump/Restore Files
6737 @section Copy between memory and a file
6738 @cindex dump/restore files
6739 @cindex append data to a file
6740 @cindex dump data to a file
6741 @cindex restore data from a file
6743 You can use the commands @code{dump}, @code{append}, and
6744 @code{restore} to copy data between target memory and a file. The
6745 @code{dump} and @code{append} commands write data to a file, and the
6746 @code{restore} command reads data from a file back into the inferior's
6747 memory. Files may be in binary, Motorola S-record, Intel hex, or
6748 Tektronix Hex format; however, @value{GDBN} can only append to binary
6754 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6755 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
6756 Dump the contents of memory from @var{start_addr} to @var{end_addr},
6757 or the value of @var{expr}, to @var{filename} in the given format.
6759 The @var{format} parameter may be any one of:
6766 Motorola S-record format.
6768 Tektronix Hex format.
6771 @value{GDBN} uses the same definitions of these formats as the
6772 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
6773 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
6777 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6778 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
6779 Append the contents of memory from @var{start_addr} to @var{end_addr},
6780 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
6781 (@value{GDBN} can only append data to files in raw binary form.)
6784 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
6785 Restore the contents of file @var{filename} into memory. The
6786 @code{restore} command can automatically recognize any known @sc{bfd}
6787 file format, except for raw binary. To restore a raw binary file you
6788 must specify the optional keyword @code{binary} after the filename.
6790 If @var{bias} is non-zero, its value will be added to the addresses
6791 contained in the file. Binary files always start at address zero, so
6792 they will be restored at address @var{bias}. Other bfd files have
6793 a built-in location; they will be restored at offset @var{bias}
6796 If @var{start} and/or @var{end} are non-zero, then only data between
6797 file offset @var{start} and file offset @var{end} will be restored.
6798 These offsets are relative to the addresses in the file, before
6799 the @var{bias} argument is applied.
6803 @node Core File Generation
6804 @section How to Produce a Core File from Your Program
6805 @cindex dump core from inferior
6807 A @dfn{core file} or @dfn{core dump} is a file that records the memory
6808 image of a running process and its process status (register values
6809 etc.). Its primary use is post-mortem debugging of a program that
6810 crashed while it ran outside a debugger. A program that crashes
6811 automatically produces a core file, unless this feature is disabled by
6812 the user. @xref{Files}, for information on invoking @value{GDBN} in
6813 the post-mortem debugging mode.
6815 Occasionally, you may wish to produce a core file of the program you
6816 are debugging in order to preserve a snapshot of its state.
6817 @value{GDBN} has a special command for that.
6821 @kindex generate-core-file
6822 @item generate-core-file [@var{file}]
6823 @itemx gcore [@var{file}]
6824 Produce a core dump of the inferior process. The optional argument
6825 @var{file} specifies the file name where to put the core dump. If not
6826 specified, the file name defaults to @file{core.@var{pid}}, where
6827 @var{pid} is the inferior process ID.
6829 Note that this command is implemented only for some systems (as of
6830 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
6833 @node Character Sets
6834 @section Character Sets
6835 @cindex character sets
6837 @cindex translating between character sets
6838 @cindex host character set
6839 @cindex target character set
6841 If the program you are debugging uses a different character set to
6842 represent characters and strings than the one @value{GDBN} uses itself,
6843 @value{GDBN} can automatically translate between the character sets for
6844 you. The character set @value{GDBN} uses we call the @dfn{host
6845 character set}; the one the inferior program uses we call the
6846 @dfn{target character set}.
6848 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
6849 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
6850 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
6851 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
6852 then the host character set is Latin-1, and the target character set is
6853 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
6854 target-charset EBCDIC-US}, then @value{GDBN} translates between
6855 @sc{ebcdic} and Latin 1 as you print character or string values, or use
6856 character and string literals in expressions.
6858 @value{GDBN} has no way to automatically recognize which character set
6859 the inferior program uses; you must tell it, using the @code{set
6860 target-charset} command, described below.
6862 Here are the commands for controlling @value{GDBN}'s character set
6866 @item set target-charset @var{charset}
6867 @kindex set target-charset
6868 Set the current target character set to @var{charset}. We list the
6869 character set names @value{GDBN} recognizes below, but if you type
6870 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6871 list the target character sets it supports.
6875 @item set host-charset @var{charset}
6876 @kindex set host-charset
6877 Set the current host character set to @var{charset}.
6879 By default, @value{GDBN} uses a host character set appropriate to the
6880 system it is running on; you can override that default using the
6881 @code{set host-charset} command.
6883 @value{GDBN} can only use certain character sets as its host character
6884 set. We list the character set names @value{GDBN} recognizes below, and
6885 indicate which can be host character sets, but if you type
6886 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6887 list the host character sets it supports.
6889 @item set charset @var{charset}
6891 Set the current host and target character sets to @var{charset}. As
6892 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
6893 @value{GDBN} will list the name of the character sets that can be used
6894 for both host and target.
6898 @kindex show charset
6899 Show the names of the current host and target charsets.
6901 @itemx show host-charset
6902 @kindex show host-charset
6903 Show the name of the current host charset.
6905 @itemx show target-charset
6906 @kindex show target-charset
6907 Show the name of the current target charset.
6911 @value{GDBN} currently includes support for the following character
6917 @cindex ASCII character set
6918 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
6922 @cindex ISO 8859-1 character set
6923 @cindex ISO Latin 1 character set
6924 The ISO Latin 1 character set. This extends @sc{ascii} with accented
6925 characters needed for French, German, and Spanish. @value{GDBN} can use
6926 this as its host character set.
6930 @cindex EBCDIC character set
6931 @cindex IBM1047 character set
6932 Variants of the @sc{ebcdic} character set, used on some of IBM's
6933 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
6934 @value{GDBN} cannot use these as its host character set.
6938 Note that these are all single-byte character sets. More work inside
6939 GDB is needed to support multi-byte or variable-width character
6940 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
6942 Here is an example of @value{GDBN}'s character set support in action.
6943 Assume that the following source code has been placed in the file
6944 @file{charset-test.c}:
6950 = @{72, 101, 108, 108, 111, 44, 32, 119,
6951 111, 114, 108, 100, 33, 10, 0@};
6952 char ibm1047_hello[]
6953 = @{200, 133, 147, 147, 150, 107, 64, 166,
6954 150, 153, 147, 132, 90, 37, 0@};
6958 printf ("Hello, world!\n");
6962 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
6963 containing the string @samp{Hello, world!} followed by a newline,
6964 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
6966 We compile the program, and invoke the debugger on it:
6969 $ gcc -g charset-test.c -o charset-test
6970 $ gdb -nw charset-test
6971 GNU gdb 2001-12-19-cvs
6972 Copyright 2001 Free Software Foundation, Inc.
6977 We can use the @code{show charset} command to see what character sets
6978 @value{GDBN} is currently using to interpret and display characters and
6982 (@value{GDBP}) show charset
6983 The current host and target character set is `ISO-8859-1'.
6987 For the sake of printing this manual, let's use @sc{ascii} as our
6988 initial character set:
6990 (@value{GDBP}) set charset ASCII
6991 (@value{GDBP}) show charset
6992 The current host and target character set is `ASCII'.
6996 Let's assume that @sc{ascii} is indeed the correct character set for our
6997 host system --- in other words, let's assume that if @value{GDBN} prints
6998 characters using the @sc{ascii} character set, our terminal will display
6999 them properly. Since our current target character set is also
7000 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
7003 (@value{GDBP}) print ascii_hello
7004 $1 = 0x401698 "Hello, world!\n"
7005 (@value{GDBP}) print ascii_hello[0]
7010 @value{GDBN} uses the target character set for character and string
7011 literals you use in expressions:
7014 (@value{GDBP}) print '+'
7019 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
7022 @value{GDBN} relies on the user to tell it which character set the
7023 target program uses. If we print @code{ibm1047_hello} while our target
7024 character set is still @sc{ascii}, we get jibberish:
7027 (@value{GDBP}) print ibm1047_hello
7028 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
7029 (@value{GDBP}) print ibm1047_hello[0]
7034 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
7035 @value{GDBN} tells us the character sets it supports:
7038 (@value{GDBP}) set target-charset
7039 ASCII EBCDIC-US IBM1047 ISO-8859-1
7040 (@value{GDBP}) set target-charset
7043 We can select @sc{ibm1047} as our target character set, and examine the
7044 program's strings again. Now the @sc{ascii} string is wrong, but
7045 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
7046 target character set, @sc{ibm1047}, to the host character set,
7047 @sc{ascii}, and they display correctly:
7050 (@value{GDBP}) set target-charset IBM1047
7051 (@value{GDBP}) show charset
7052 The current host character set is `ASCII'.
7053 The current target character set is `IBM1047'.
7054 (@value{GDBP}) print ascii_hello
7055 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
7056 (@value{GDBP}) print ascii_hello[0]
7058 (@value{GDBP}) print ibm1047_hello
7059 $8 = 0x4016a8 "Hello, world!\n"
7060 (@value{GDBP}) print ibm1047_hello[0]
7065 As above, @value{GDBN} uses the target character set for character and
7066 string literals you use in expressions:
7069 (@value{GDBP}) print '+'
7074 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
7077 @node Caching Remote Data
7078 @section Caching Data of Remote Targets
7079 @cindex caching data of remote targets
7081 @value{GDBN} can cache data exchanged between the debugger and a
7082 remote target (@pxref{Remote}). Such caching generally improves
7083 performance, because it reduces the overhead of the remote protocol by
7084 bundling memory reads and writes into large chunks. Unfortunately,
7085 @value{GDBN} does not currently know anything about volatile
7086 registers, and thus data caching will produce incorrect results when
7087 volatile registers are in use.
7090 @kindex set remotecache
7091 @item set remotecache on
7092 @itemx set remotecache off
7093 Set caching state for remote targets. When @code{ON}, use data
7094 caching. By default, this option is @code{OFF}.
7096 @kindex show remotecache
7097 @item show remotecache
7098 Show the current state of data caching for remote targets.
7102 Print the information about the data cache performance. The
7103 information displayed includes: the dcache width and depth; and for
7104 each cache line, how many times it was referenced, and its data and
7105 state (dirty, bad, ok, etc.). This command is useful for debugging
7106 the data cache operation.
7111 @chapter C Preprocessor Macros
7113 Some languages, such as C and C@t{++}, provide a way to define and invoke
7114 ``preprocessor macros'' which expand into strings of tokens.
7115 @value{GDBN} can evaluate expressions containing macro invocations, show
7116 the result of macro expansion, and show a macro's definition, including
7117 where it was defined.
7119 You may need to compile your program specially to provide @value{GDBN}
7120 with information about preprocessor macros. Most compilers do not
7121 include macros in their debugging information, even when you compile
7122 with the @option{-g} flag. @xref{Compilation}.
7124 A program may define a macro at one point, remove that definition later,
7125 and then provide a different definition after that. Thus, at different
7126 points in the program, a macro may have different definitions, or have
7127 no definition at all. If there is a current stack frame, @value{GDBN}
7128 uses the macros in scope at that frame's source code line. Otherwise,
7129 @value{GDBN} uses the macros in scope at the current listing location;
7132 At the moment, @value{GDBN} does not support the @code{##}
7133 token-splicing operator, the @code{#} stringification operator, or
7134 variable-arity macros.
7136 Whenever @value{GDBN} evaluates an expression, it always expands any
7137 macro invocations present in the expression. @value{GDBN} also provides
7138 the following commands for working with macros explicitly.
7142 @kindex macro expand
7143 @cindex macro expansion, showing the results of preprocessor
7144 @cindex preprocessor macro expansion, showing the results of
7145 @cindex expanding preprocessor macros
7146 @item macro expand @var{expression}
7147 @itemx macro exp @var{expression}
7148 Show the results of expanding all preprocessor macro invocations in
7149 @var{expression}. Since @value{GDBN} simply expands macros, but does
7150 not parse the result, @var{expression} need not be a valid expression;
7151 it can be any string of tokens.
7154 @item macro expand-once @var{expression}
7155 @itemx macro exp1 @var{expression}
7156 @cindex expand macro once
7157 @i{(This command is not yet implemented.)} Show the results of
7158 expanding those preprocessor macro invocations that appear explicitly in
7159 @var{expression}. Macro invocations appearing in that expansion are
7160 left unchanged. This command allows you to see the effect of a
7161 particular macro more clearly, without being confused by further
7162 expansions. Since @value{GDBN} simply expands macros, but does not
7163 parse the result, @var{expression} need not be a valid expression; it
7164 can be any string of tokens.
7167 @cindex macro definition, showing
7168 @cindex definition, showing a macro's
7169 @item info macro @var{macro}
7170 Show the definition of the macro named @var{macro}, and describe the
7171 source location where that definition was established.
7173 @kindex macro define
7174 @cindex user-defined macros
7175 @cindex defining macros interactively
7176 @cindex macros, user-defined
7177 @item macro define @var{macro} @var{replacement-list}
7178 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
7179 @i{(This command is not yet implemented.)} Introduce a definition for a
7180 preprocessor macro named @var{macro}, invocations of which are replaced
7181 by the tokens given in @var{replacement-list}. The first form of this
7182 command defines an ``object-like'' macro, which takes no arguments; the
7183 second form defines a ``function-like'' macro, which takes the arguments
7184 given in @var{arglist}.
7186 A definition introduced by this command is in scope in every expression
7187 evaluated in @value{GDBN}, until it is removed with the @command{macro
7188 undef} command, described below. The definition overrides all
7189 definitions for @var{macro} present in the program being debugged, as
7190 well as any previous user-supplied definition.
7193 @item macro undef @var{macro}
7194 @i{(This command is not yet implemented.)} Remove any user-supplied
7195 definition for the macro named @var{macro}. This command only affects
7196 definitions provided with the @command{macro define} command, described
7197 above; it cannot remove definitions present in the program being
7202 @i{(This command is not yet implemented.)} List all the macros
7203 defined using the @code{macro define} command.
7206 @cindex macros, example of debugging with
7207 Here is a transcript showing the above commands in action. First, we
7208 show our source files:
7216 #define ADD(x) (M + x)
7221 printf ("Hello, world!\n");
7223 printf ("We're so creative.\n");
7225 printf ("Goodbye, world!\n");
7232 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
7233 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
7234 compiler includes information about preprocessor macros in the debugging
7238 $ gcc -gdwarf-2 -g3 sample.c -o sample
7242 Now, we start @value{GDBN} on our sample program:
7246 GNU gdb 2002-05-06-cvs
7247 Copyright 2002 Free Software Foundation, Inc.
7248 GDB is free software, @dots{}
7252 We can expand macros and examine their definitions, even when the
7253 program is not running. @value{GDBN} uses the current listing position
7254 to decide which macro definitions are in scope:
7257 (@value{GDBP}) list main
7260 5 #define ADD(x) (M + x)
7265 10 printf ("Hello, world!\n");
7267 12 printf ("We're so creative.\n");
7268 (@value{GDBP}) info macro ADD
7269 Defined at /home/jimb/gdb/macros/play/sample.c:5
7270 #define ADD(x) (M + x)
7271 (@value{GDBP}) info macro Q
7272 Defined at /home/jimb/gdb/macros/play/sample.h:1
7273 included at /home/jimb/gdb/macros/play/sample.c:2
7275 (@value{GDBP}) macro expand ADD(1)
7276 expands to: (42 + 1)
7277 (@value{GDBP}) macro expand-once ADD(1)
7278 expands to: once (M + 1)
7282 In the example above, note that @command{macro expand-once} expands only
7283 the macro invocation explicit in the original text --- the invocation of
7284 @code{ADD} --- but does not expand the invocation of the macro @code{M},
7285 which was introduced by @code{ADD}.
7287 Once the program is running, GDB uses the macro definitions in force at
7288 the source line of the current stack frame:
7291 (@value{GDBP}) break main
7292 Breakpoint 1 at 0x8048370: file sample.c, line 10.
7294 Starting program: /home/jimb/gdb/macros/play/sample
7296 Breakpoint 1, main () at sample.c:10
7297 10 printf ("Hello, world!\n");
7301 At line 10, the definition of the macro @code{N} at line 9 is in force:
7304 (@value{GDBP}) info macro N
7305 Defined at /home/jimb/gdb/macros/play/sample.c:9
7307 (@value{GDBP}) macro expand N Q M
7309 (@value{GDBP}) print N Q M
7314 As we step over directives that remove @code{N}'s definition, and then
7315 give it a new definition, @value{GDBN} finds the definition (or lack
7316 thereof) in force at each point:
7321 12 printf ("We're so creative.\n");
7322 (@value{GDBP}) info macro N
7323 The symbol `N' has no definition as a C/C++ preprocessor macro
7324 at /home/jimb/gdb/macros/play/sample.c:12
7327 14 printf ("Goodbye, world!\n");
7328 (@value{GDBP}) info macro N
7329 Defined at /home/jimb/gdb/macros/play/sample.c:13
7331 (@value{GDBP}) macro expand N Q M
7332 expands to: 1729 < 42
7333 (@value{GDBP}) print N Q M
7340 @chapter Tracepoints
7341 @c This chapter is based on the documentation written by Michael
7342 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
7345 In some applications, it is not feasible for the debugger to interrupt
7346 the program's execution long enough for the developer to learn
7347 anything helpful about its behavior. If the program's correctness
7348 depends on its real-time behavior, delays introduced by a debugger
7349 might cause the program to change its behavior drastically, or perhaps
7350 fail, even when the code itself is correct. It is useful to be able
7351 to observe the program's behavior without interrupting it.
7353 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
7354 specify locations in the program, called @dfn{tracepoints}, and
7355 arbitrary expressions to evaluate when those tracepoints are reached.
7356 Later, using the @code{tfind} command, you can examine the values
7357 those expressions had when the program hit the tracepoints. The
7358 expressions may also denote objects in memory---structures or arrays,
7359 for example---whose values @value{GDBN} should record; while visiting
7360 a particular tracepoint, you may inspect those objects as if they were
7361 in memory at that moment. However, because @value{GDBN} records these
7362 values without interacting with you, it can do so quickly and
7363 unobtrusively, hopefully not disturbing the program's behavior.
7365 The tracepoint facility is currently available only for remote
7366 targets. @xref{Targets}. In addition, your remote target must know
7367 how to collect trace data. This functionality is implemented in the
7368 remote stub; however, none of the stubs distributed with @value{GDBN}
7369 support tracepoints as of this writing. The format of the remote
7370 packets used to implement tracepoints are described in @ref{Tracepoint
7373 This chapter describes the tracepoint commands and features.
7377 * Analyze Collected Data::
7378 * Tracepoint Variables::
7381 @node Set Tracepoints
7382 @section Commands to Set Tracepoints
7384 Before running such a @dfn{trace experiment}, an arbitrary number of
7385 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
7386 tracepoint has a number assigned to it by @value{GDBN}. Like with
7387 breakpoints, tracepoint numbers are successive integers starting from
7388 one. Many of the commands associated with tracepoints take the
7389 tracepoint number as their argument, to identify which tracepoint to
7392 For each tracepoint, you can specify, in advance, some arbitrary set
7393 of data that you want the target to collect in the trace buffer when
7394 it hits that tracepoint. The collected data can include registers,
7395 local variables, or global data. Later, you can use @value{GDBN}
7396 commands to examine the values these data had at the time the
7399 This section describes commands to set tracepoints and associated
7400 conditions and actions.
7403 * Create and Delete Tracepoints::
7404 * Enable and Disable Tracepoints::
7405 * Tracepoint Passcounts::
7406 * Tracepoint Actions::
7407 * Listing Tracepoints::
7408 * Starting and Stopping Trace Experiment::
7411 @node Create and Delete Tracepoints
7412 @subsection Create and Delete Tracepoints
7415 @cindex set tracepoint
7418 The @code{trace} command is very similar to the @code{break} command.
7419 Its argument can be a source line, a function name, or an address in
7420 the target program. @xref{Set Breaks}. The @code{trace} command
7421 defines a tracepoint, which is a point in the target program where the
7422 debugger will briefly stop, collect some data, and then allow the
7423 program to continue. Setting a tracepoint or changing its commands
7424 doesn't take effect until the next @code{tstart} command; thus, you
7425 cannot change the tracepoint attributes once a trace experiment is
7428 Here are some examples of using the @code{trace} command:
7431 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
7433 (@value{GDBP}) @b{trace +2} // 2 lines forward
7435 (@value{GDBP}) @b{trace my_function} // first source line of function
7437 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
7439 (@value{GDBP}) @b{trace *0x2117c4} // an address
7443 You can abbreviate @code{trace} as @code{tr}.
7446 @cindex last tracepoint number
7447 @cindex recent tracepoint number
7448 @cindex tracepoint number
7449 The convenience variable @code{$tpnum} records the tracepoint number
7450 of the most recently set tracepoint.
7452 @kindex delete tracepoint
7453 @cindex tracepoint deletion
7454 @item delete tracepoint @r{[}@var{num}@r{]}
7455 Permanently delete one or more tracepoints. With no argument, the
7456 default is to delete all tracepoints.
7461 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
7463 (@value{GDBP}) @b{delete trace} // remove all tracepoints
7467 You can abbreviate this command as @code{del tr}.
7470 @node Enable and Disable Tracepoints
7471 @subsection Enable and Disable Tracepoints
7474 @kindex disable tracepoint
7475 @item disable tracepoint @r{[}@var{num}@r{]}
7476 Disable tracepoint @var{num}, or all tracepoints if no argument
7477 @var{num} is given. A disabled tracepoint will have no effect during
7478 the next trace experiment, but it is not forgotten. You can re-enable
7479 a disabled tracepoint using the @code{enable tracepoint} command.
7481 @kindex enable tracepoint
7482 @item enable tracepoint @r{[}@var{num}@r{]}
7483 Enable tracepoint @var{num}, or all tracepoints. The enabled
7484 tracepoints will become effective the next time a trace experiment is
7488 @node Tracepoint Passcounts
7489 @subsection Tracepoint Passcounts
7493 @cindex tracepoint pass count
7494 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
7495 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
7496 automatically stop a trace experiment. If a tracepoint's passcount is
7497 @var{n}, then the trace experiment will be automatically stopped on
7498 the @var{n}'th time that tracepoint is hit. If the tracepoint number
7499 @var{num} is not specified, the @code{passcount} command sets the
7500 passcount of the most recently defined tracepoint. If no passcount is
7501 given, the trace experiment will run until stopped explicitly by the
7507 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
7508 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
7510 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
7511 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
7512 (@value{GDBP}) @b{trace foo}
7513 (@value{GDBP}) @b{pass 3}
7514 (@value{GDBP}) @b{trace bar}
7515 (@value{GDBP}) @b{pass 2}
7516 (@value{GDBP}) @b{trace baz}
7517 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
7518 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
7519 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
7520 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
7524 @node Tracepoint Actions
7525 @subsection Tracepoint Action Lists
7529 @cindex tracepoint actions
7530 @item actions @r{[}@var{num}@r{]}
7531 This command will prompt for a list of actions to be taken when the
7532 tracepoint is hit. If the tracepoint number @var{num} is not
7533 specified, this command sets the actions for the one that was most
7534 recently defined (so that you can define a tracepoint and then say
7535 @code{actions} without bothering about its number). You specify the
7536 actions themselves on the following lines, one action at a time, and
7537 terminate the actions list with a line containing just @code{end}. So
7538 far, the only defined actions are @code{collect} and
7539 @code{while-stepping}.
7541 @cindex remove actions from a tracepoint
7542 To remove all actions from a tracepoint, type @samp{actions @var{num}}
7543 and follow it immediately with @samp{end}.
7546 (@value{GDBP}) @b{collect @var{data}} // collect some data
7548 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
7550 (@value{GDBP}) @b{end} // signals the end of actions.
7553 In the following example, the action list begins with @code{collect}
7554 commands indicating the things to be collected when the tracepoint is
7555 hit. Then, in order to single-step and collect additional data
7556 following the tracepoint, a @code{while-stepping} command is used,
7557 followed by the list of things to be collected while stepping. The
7558 @code{while-stepping} command is terminated by its own separate
7559 @code{end} command. Lastly, the action list is terminated by an
7563 (@value{GDBP}) @b{trace foo}
7564 (@value{GDBP}) @b{actions}
7565 Enter actions for tracepoint 1, one per line:
7574 @kindex collect @r{(tracepoints)}
7575 @item collect @var{expr1}, @var{expr2}, @dots{}
7576 Collect values of the given expressions when the tracepoint is hit.
7577 This command accepts a comma-separated list of any valid expressions.
7578 In addition to global, static, or local variables, the following
7579 special arguments are supported:
7583 collect all registers
7586 collect all function arguments
7589 collect all local variables.
7592 You can give several consecutive @code{collect} commands, each one
7593 with a single argument, or one @code{collect} command with several
7594 arguments separated by commas: the effect is the same.
7596 The command @code{info scope} (@pxref{Symbols, info scope}) is
7597 particularly useful for figuring out what data to collect.
7599 @kindex while-stepping @r{(tracepoints)}
7600 @item while-stepping @var{n}
7601 Perform @var{n} single-step traces after the tracepoint, collecting
7602 new data at each step. The @code{while-stepping} command is
7603 followed by the list of what to collect while stepping (followed by
7604 its own @code{end} command):
7608 > collect $regs, myglobal
7614 You may abbreviate @code{while-stepping} as @code{ws} or
7618 @node Listing Tracepoints
7619 @subsection Listing Tracepoints
7622 @kindex info tracepoints
7624 @cindex information about tracepoints
7625 @item info tracepoints @r{[}@var{num}@r{]}
7626 Display information about the tracepoint @var{num}. If you don't specify
7627 a tracepoint number, displays information about all the tracepoints
7628 defined so far. For each tracepoint, the following information is
7635 whether it is enabled or disabled
7639 its passcount as given by the @code{passcount @var{n}} command
7641 its step count as given by the @code{while-stepping @var{n}} command
7643 where in the source files is the tracepoint set
7645 its action list as given by the @code{actions} command
7649 (@value{GDBP}) @b{info trace}
7650 Num Enb Address PassC StepC What
7651 1 y 0x002117c4 0 0 <gdb_asm>
7652 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
7653 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
7658 This command can be abbreviated @code{info tp}.
7661 @node Starting and Stopping Trace Experiment
7662 @subsection Starting and Stopping Trace Experiment
7666 @cindex start a new trace experiment
7667 @cindex collected data discarded
7669 This command takes no arguments. It starts the trace experiment, and
7670 begins collecting data. This has the side effect of discarding all
7671 the data collected in the trace buffer during the previous trace
7675 @cindex stop a running trace experiment
7677 This command takes no arguments. It ends the trace experiment, and
7678 stops collecting data.
7680 @strong{Note}: a trace experiment and data collection may stop
7681 automatically if any tracepoint's passcount is reached
7682 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
7685 @cindex status of trace data collection
7686 @cindex trace experiment, status of
7688 This command displays the status of the current trace data
7692 Here is an example of the commands we described so far:
7695 (@value{GDBP}) @b{trace gdb_c_test}
7696 (@value{GDBP}) @b{actions}
7697 Enter actions for tracepoint #1, one per line.
7698 > collect $regs,$locals,$args
7703 (@value{GDBP}) @b{tstart}
7704 [time passes @dots{}]
7705 (@value{GDBP}) @b{tstop}
7709 @node Analyze Collected Data
7710 @section Using the collected data
7712 After the tracepoint experiment ends, you use @value{GDBN} commands
7713 for examining the trace data. The basic idea is that each tracepoint
7714 collects a trace @dfn{snapshot} every time it is hit and another
7715 snapshot every time it single-steps. All these snapshots are
7716 consecutively numbered from zero and go into a buffer, and you can
7717 examine them later. The way you examine them is to @dfn{focus} on a
7718 specific trace snapshot. When the remote stub is focused on a trace
7719 snapshot, it will respond to all @value{GDBN} requests for memory and
7720 registers by reading from the buffer which belongs to that snapshot,
7721 rather than from @emph{real} memory or registers of the program being
7722 debugged. This means that @strong{all} @value{GDBN} commands
7723 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
7724 behave as if we were currently debugging the program state as it was
7725 when the tracepoint occurred. Any requests for data that are not in
7726 the buffer will fail.
7729 * tfind:: How to select a trace snapshot
7730 * tdump:: How to display all data for a snapshot
7731 * save-tracepoints:: How to save tracepoints for a future run
7735 @subsection @code{tfind @var{n}}
7738 @cindex select trace snapshot
7739 @cindex find trace snapshot
7740 The basic command for selecting a trace snapshot from the buffer is
7741 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
7742 counting from zero. If no argument @var{n} is given, the next
7743 snapshot is selected.
7745 Here are the various forms of using the @code{tfind} command.
7749 Find the first snapshot in the buffer. This is a synonym for
7750 @code{tfind 0} (since 0 is the number of the first snapshot).
7753 Stop debugging trace snapshots, resume @emph{live} debugging.
7756 Same as @samp{tfind none}.
7759 No argument means find the next trace snapshot.
7762 Find the previous trace snapshot before the current one. This permits
7763 retracing earlier steps.
7765 @item tfind tracepoint @var{num}
7766 Find the next snapshot associated with tracepoint @var{num}. Search
7767 proceeds forward from the last examined trace snapshot. If no
7768 argument @var{num} is given, it means find the next snapshot collected
7769 for the same tracepoint as the current snapshot.
7771 @item tfind pc @var{addr}
7772 Find the next snapshot associated with the value @var{addr} of the
7773 program counter. Search proceeds forward from the last examined trace
7774 snapshot. If no argument @var{addr} is given, it means find the next
7775 snapshot with the same value of PC as the current snapshot.
7777 @item tfind outside @var{addr1}, @var{addr2}
7778 Find the next snapshot whose PC is outside the given range of
7781 @item tfind range @var{addr1}, @var{addr2}
7782 Find the next snapshot whose PC is between @var{addr1} and
7783 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
7785 @item tfind line @r{[}@var{file}:@r{]}@var{n}
7786 Find the next snapshot associated with the source line @var{n}. If
7787 the optional argument @var{file} is given, refer to line @var{n} in
7788 that source file. Search proceeds forward from the last examined
7789 trace snapshot. If no argument @var{n} is given, it means find the
7790 next line other than the one currently being examined; thus saying
7791 @code{tfind line} repeatedly can appear to have the same effect as
7792 stepping from line to line in a @emph{live} debugging session.
7795 The default arguments for the @code{tfind} commands are specifically
7796 designed to make it easy to scan through the trace buffer. For
7797 instance, @code{tfind} with no argument selects the next trace
7798 snapshot, and @code{tfind -} with no argument selects the previous
7799 trace snapshot. So, by giving one @code{tfind} command, and then
7800 simply hitting @key{RET} repeatedly you can examine all the trace
7801 snapshots in order. Or, by saying @code{tfind -} and then hitting
7802 @key{RET} repeatedly you can examine the snapshots in reverse order.
7803 The @code{tfind line} command with no argument selects the snapshot
7804 for the next source line executed. The @code{tfind pc} command with
7805 no argument selects the next snapshot with the same program counter
7806 (PC) as the current frame. The @code{tfind tracepoint} command with
7807 no argument selects the next trace snapshot collected by the same
7808 tracepoint as the current one.
7810 In addition to letting you scan through the trace buffer manually,
7811 these commands make it easy to construct @value{GDBN} scripts that
7812 scan through the trace buffer and print out whatever collected data
7813 you are interested in. Thus, if we want to examine the PC, FP, and SP
7814 registers from each trace frame in the buffer, we can say this:
7817 (@value{GDBP}) @b{tfind start}
7818 (@value{GDBP}) @b{while ($trace_frame != -1)}
7819 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
7820 $trace_frame, $pc, $sp, $fp
7824 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
7825 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
7826 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
7827 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
7828 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
7829 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
7830 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
7831 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
7832 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
7833 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
7834 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
7837 Or, if we want to examine the variable @code{X} at each source line in
7841 (@value{GDBP}) @b{tfind start}
7842 (@value{GDBP}) @b{while ($trace_frame != -1)}
7843 > printf "Frame %d, X == %d\n", $trace_frame, X
7853 @subsection @code{tdump}
7855 @cindex dump all data collected at tracepoint
7856 @cindex tracepoint data, display
7858 This command takes no arguments. It prints all the data collected at
7859 the current trace snapshot.
7862 (@value{GDBP}) @b{trace 444}
7863 (@value{GDBP}) @b{actions}
7864 Enter actions for tracepoint #2, one per line:
7865 > collect $regs, $locals, $args, gdb_long_test
7868 (@value{GDBP}) @b{tstart}
7870 (@value{GDBP}) @b{tfind line 444}
7871 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
7873 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
7875 (@value{GDBP}) @b{tdump}
7876 Data collected at tracepoint 2, trace frame 1:
7877 d0 0xc4aa0085 -995491707
7881 d4 0x71aea3d 119204413
7886 a1 0x3000668 50333288
7889 a4 0x3000698 50333336
7891 fp 0x30bf3c 0x30bf3c
7892 sp 0x30bf34 0x30bf34
7894 pc 0x20b2c8 0x20b2c8
7898 p = 0x20e5b4 "gdb-test"
7905 gdb_long_test = 17 '\021'
7910 @node save-tracepoints
7911 @subsection @code{save-tracepoints @var{filename}}
7912 @kindex save-tracepoints
7913 @cindex save tracepoints for future sessions
7915 This command saves all current tracepoint definitions together with
7916 their actions and passcounts, into a file @file{@var{filename}}
7917 suitable for use in a later debugging session. To read the saved
7918 tracepoint definitions, use the @code{source} command (@pxref{Command
7921 @node Tracepoint Variables
7922 @section Convenience Variables for Tracepoints
7923 @cindex tracepoint variables
7924 @cindex convenience variables for tracepoints
7927 @vindex $trace_frame
7928 @item (int) $trace_frame
7929 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
7930 snapshot is selected.
7933 @item (int) $tracepoint
7934 The tracepoint for the current trace snapshot.
7937 @item (int) $trace_line
7938 The line number for the current trace snapshot.
7941 @item (char []) $trace_file
7942 The source file for the current trace snapshot.
7945 @item (char []) $trace_func
7946 The name of the function containing @code{$tracepoint}.
7949 Note: @code{$trace_file} is not suitable for use in @code{printf},
7950 use @code{output} instead.
7952 Here's a simple example of using these convenience variables for
7953 stepping through all the trace snapshots and printing some of their
7957 (@value{GDBP}) @b{tfind start}
7959 (@value{GDBP}) @b{while $trace_frame != -1}
7960 > output $trace_file
7961 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
7967 @chapter Debugging Programs That Use Overlays
7970 If your program is too large to fit completely in your target system's
7971 memory, you can sometimes use @dfn{overlays} to work around this
7972 problem. @value{GDBN} provides some support for debugging programs that
7976 * How Overlays Work:: A general explanation of overlays.
7977 * Overlay Commands:: Managing overlays in @value{GDBN}.
7978 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
7979 mapped by asking the inferior.
7980 * Overlay Sample Program:: A sample program using overlays.
7983 @node How Overlays Work
7984 @section How Overlays Work
7985 @cindex mapped overlays
7986 @cindex unmapped overlays
7987 @cindex load address, overlay's
7988 @cindex mapped address
7989 @cindex overlay area
7991 Suppose you have a computer whose instruction address space is only 64
7992 kilobytes long, but which has much more memory which can be accessed by
7993 other means: special instructions, segment registers, or memory
7994 management hardware, for example. Suppose further that you want to
7995 adapt a program which is larger than 64 kilobytes to run on this system.
7997 One solution is to identify modules of your program which are relatively
7998 independent, and need not call each other directly; call these modules
7999 @dfn{overlays}. Separate the overlays from the main program, and place
8000 their machine code in the larger memory. Place your main program in
8001 instruction memory, but leave at least enough space there to hold the
8002 largest overlay as well.
8004 Now, to call a function located in an overlay, you must first copy that
8005 overlay's machine code from the large memory into the space set aside
8006 for it in the instruction memory, and then jump to its entry point
8009 @c NB: In the below the mapped area's size is greater or equal to the
8010 @c size of all overlays. This is intentional to remind the developer
8011 @c that overlays don't necessarily need to be the same size.
8015 Data Instruction Larger
8016 Address Space Address Space Address Space
8017 +-----------+ +-----------+ +-----------+
8019 +-----------+ +-----------+ +-----------+<-- overlay 1
8020 | program | | main | .----| overlay 1 | load address
8021 | variables | | program | | +-----------+
8022 | and heap | | | | | |
8023 +-----------+ | | | +-----------+<-- overlay 2
8024 | | +-----------+ | | | load address
8025 +-----------+ | | | .-| overlay 2 |
8027 mapped --->+-----------+ | | +-----------+
8029 | overlay | <-' | | |
8030 | area | <---' +-----------+<-- overlay 3
8031 | | <---. | | load address
8032 +-----------+ `--| overlay 3 |
8039 @anchor{A code overlay}A code overlay
8043 The diagram (@pxref{A code overlay}) shows a system with separate data
8044 and instruction address spaces. To map an overlay, the program copies
8045 its code from the larger address space to the instruction address space.
8046 Since the overlays shown here all use the same mapped address, only one
8047 may be mapped at a time. For a system with a single address space for
8048 data and instructions, the diagram would be similar, except that the
8049 program variables and heap would share an address space with the main
8050 program and the overlay area.
8052 An overlay loaded into instruction memory and ready for use is called a
8053 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
8054 instruction memory. An overlay not present (or only partially present)
8055 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
8056 is its address in the larger memory. The mapped address is also called
8057 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
8058 called the @dfn{load memory address}, or @dfn{LMA}.
8060 Unfortunately, overlays are not a completely transparent way to adapt a
8061 program to limited instruction memory. They introduce a new set of
8062 global constraints you must keep in mind as you design your program:
8067 Before calling or returning to a function in an overlay, your program
8068 must make sure that overlay is actually mapped. Otherwise, the call or
8069 return will transfer control to the right address, but in the wrong
8070 overlay, and your program will probably crash.
8073 If the process of mapping an overlay is expensive on your system, you
8074 will need to choose your overlays carefully to minimize their effect on
8075 your program's performance.
8078 The executable file you load onto your system must contain each
8079 overlay's instructions, appearing at the overlay's load address, not its
8080 mapped address. However, each overlay's instructions must be relocated
8081 and its symbols defined as if the overlay were at its mapped address.
8082 You can use GNU linker scripts to specify different load and relocation
8083 addresses for pieces of your program; see @ref{Overlay Description,,,
8084 ld.info, Using ld: the GNU linker}.
8087 The procedure for loading executable files onto your system must be able
8088 to load their contents into the larger address space as well as the
8089 instruction and data spaces.
8093 The overlay system described above is rather simple, and could be
8094 improved in many ways:
8099 If your system has suitable bank switch registers or memory management
8100 hardware, you could use those facilities to make an overlay's load area
8101 contents simply appear at their mapped address in instruction space.
8102 This would probably be faster than copying the overlay to its mapped
8103 area in the usual way.
8106 If your overlays are small enough, you could set aside more than one
8107 overlay area, and have more than one overlay mapped at a time.
8110 You can use overlays to manage data, as well as instructions. In
8111 general, data overlays are even less transparent to your design than
8112 code overlays: whereas code overlays only require care when you call or
8113 return to functions, data overlays require care every time you access
8114 the data. Also, if you change the contents of a data overlay, you
8115 must copy its contents back out to its load address before you can copy a
8116 different data overlay into the same mapped area.
8121 @node Overlay Commands
8122 @section Overlay Commands
8124 To use @value{GDBN}'s overlay support, each overlay in your program must
8125 correspond to a separate section of the executable file. The section's
8126 virtual memory address and load memory address must be the overlay's
8127 mapped and load addresses. Identifying overlays with sections allows
8128 @value{GDBN} to determine the appropriate address of a function or
8129 variable, depending on whether the overlay is mapped or not.
8131 @value{GDBN}'s overlay commands all start with the word @code{overlay};
8132 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
8137 Disable @value{GDBN}'s overlay support. When overlay support is
8138 disabled, @value{GDBN} assumes that all functions and variables are
8139 always present at their mapped addresses. By default, @value{GDBN}'s
8140 overlay support is disabled.
8142 @item overlay manual
8143 @cindex manual overlay debugging
8144 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
8145 relies on you to tell it which overlays are mapped, and which are not,
8146 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
8147 commands described below.
8149 @item overlay map-overlay @var{overlay}
8150 @itemx overlay map @var{overlay}
8151 @cindex map an overlay
8152 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
8153 be the name of the object file section containing the overlay. When an
8154 overlay is mapped, @value{GDBN} assumes it can find the overlay's
8155 functions and variables at their mapped addresses. @value{GDBN} assumes
8156 that any other overlays whose mapped ranges overlap that of
8157 @var{overlay} are now unmapped.
8159 @item overlay unmap-overlay @var{overlay}
8160 @itemx overlay unmap @var{overlay}
8161 @cindex unmap an overlay
8162 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
8163 must be the name of the object file section containing the overlay.
8164 When an overlay is unmapped, @value{GDBN} assumes it can find the
8165 overlay's functions and variables at their load addresses.
8168 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
8169 consults a data structure the overlay manager maintains in the inferior
8170 to see which overlays are mapped. For details, see @ref{Automatic
8173 @item overlay load-target
8175 @cindex reloading the overlay table
8176 Re-read the overlay table from the inferior. Normally, @value{GDBN}
8177 re-reads the table @value{GDBN} automatically each time the inferior
8178 stops, so this command should only be necessary if you have changed the
8179 overlay mapping yourself using @value{GDBN}. This command is only
8180 useful when using automatic overlay debugging.
8182 @item overlay list-overlays
8184 @cindex listing mapped overlays
8185 Display a list of the overlays currently mapped, along with their mapped
8186 addresses, load addresses, and sizes.
8190 Normally, when @value{GDBN} prints a code address, it includes the name
8191 of the function the address falls in:
8194 (@value{GDBP}) print main
8195 $3 = @{int ()@} 0x11a0 <main>
8198 When overlay debugging is enabled, @value{GDBN} recognizes code in
8199 unmapped overlays, and prints the names of unmapped functions with
8200 asterisks around them. For example, if @code{foo} is a function in an
8201 unmapped overlay, @value{GDBN} prints it this way:
8204 (@value{GDBP}) overlay list
8205 No sections are mapped.
8206 (@value{GDBP}) print foo
8207 $5 = @{int (int)@} 0x100000 <*foo*>
8210 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
8214 (@value{GDBP}) overlay list
8215 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
8216 mapped at 0x1016 - 0x104a
8217 (@value{GDBP}) print foo
8218 $6 = @{int (int)@} 0x1016 <foo>
8221 When overlay debugging is enabled, @value{GDBN} can find the correct
8222 address for functions and variables in an overlay, whether or not the
8223 overlay is mapped. This allows most @value{GDBN} commands, like
8224 @code{break} and @code{disassemble}, to work normally, even on unmapped
8225 code. However, @value{GDBN}'s breakpoint support has some limitations:
8229 @cindex breakpoints in overlays
8230 @cindex overlays, setting breakpoints in
8231 You can set breakpoints in functions in unmapped overlays, as long as
8232 @value{GDBN} can write to the overlay at its load address.
8234 @value{GDBN} can not set hardware or simulator-based breakpoints in
8235 unmapped overlays. However, if you set a breakpoint at the end of your
8236 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
8237 you are using manual overlay management), @value{GDBN} will re-set its
8238 breakpoints properly.
8242 @node Automatic Overlay Debugging
8243 @section Automatic Overlay Debugging
8244 @cindex automatic overlay debugging
8246 @value{GDBN} can automatically track which overlays are mapped and which
8247 are not, given some simple co-operation from the overlay manager in the
8248 inferior. If you enable automatic overlay debugging with the
8249 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
8250 looks in the inferior's memory for certain variables describing the
8251 current state of the overlays.
8253 Here are the variables your overlay manager must define to support
8254 @value{GDBN}'s automatic overlay debugging:
8258 @item @code{_ovly_table}:
8259 This variable must be an array of the following structures:
8264 /* The overlay's mapped address. */
8267 /* The size of the overlay, in bytes. */
8270 /* The overlay's load address. */
8273 /* Non-zero if the overlay is currently mapped;
8275 unsigned long mapped;
8279 @item @code{_novlys}:
8280 This variable must be a four-byte signed integer, holding the total
8281 number of elements in @code{_ovly_table}.
8285 To decide whether a particular overlay is mapped or not, @value{GDBN}
8286 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
8287 @code{lma} members equal the VMA and LMA of the overlay's section in the
8288 executable file. When @value{GDBN} finds a matching entry, it consults
8289 the entry's @code{mapped} member to determine whether the overlay is
8292 In addition, your overlay manager may define a function called
8293 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
8294 will silently set a breakpoint there. If the overlay manager then
8295 calls this function whenever it has changed the overlay table, this
8296 will enable @value{GDBN} to accurately keep track of which overlays
8297 are in program memory, and update any breakpoints that may be set
8298 in overlays. This will allow breakpoints to work even if the
8299 overlays are kept in ROM or other non-writable memory while they
8300 are not being executed.
8302 @node Overlay Sample Program
8303 @section Overlay Sample Program
8304 @cindex overlay example program
8306 When linking a program which uses overlays, you must place the overlays
8307 at their load addresses, while relocating them to run at their mapped
8308 addresses. To do this, you must write a linker script (@pxref{Overlay
8309 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
8310 since linker scripts are specific to a particular host system, target
8311 architecture, and target memory layout, this manual cannot provide
8312 portable sample code demonstrating @value{GDBN}'s overlay support.
8314 However, the @value{GDBN} source distribution does contain an overlaid
8315 program, with linker scripts for a few systems, as part of its test
8316 suite. The program consists of the following files from
8317 @file{gdb/testsuite/gdb.base}:
8321 The main program file.
8323 A simple overlay manager, used by @file{overlays.c}.
8328 Overlay modules, loaded and used by @file{overlays.c}.
8331 Linker scripts for linking the test program on the @code{d10v-elf}
8332 and @code{m32r-elf} targets.
8335 You can build the test program using the @code{d10v-elf} GCC
8336 cross-compiler like this:
8339 $ d10v-elf-gcc -g -c overlays.c
8340 $ d10v-elf-gcc -g -c ovlymgr.c
8341 $ d10v-elf-gcc -g -c foo.c
8342 $ d10v-elf-gcc -g -c bar.c
8343 $ d10v-elf-gcc -g -c baz.c
8344 $ d10v-elf-gcc -g -c grbx.c
8345 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
8346 baz.o grbx.o -Wl,-Td10v.ld -o overlays
8349 The build process is identical for any other architecture, except that
8350 you must substitute the appropriate compiler and linker script for the
8351 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
8355 @chapter Using @value{GDBN} with Different Languages
8358 Although programming languages generally have common aspects, they are
8359 rarely expressed in the same manner. For instance, in ANSI C,
8360 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
8361 Modula-2, it is accomplished by @code{p^}. Values can also be
8362 represented (and displayed) differently. Hex numbers in C appear as
8363 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
8365 @cindex working language
8366 Language-specific information is built into @value{GDBN} for some languages,
8367 allowing you to express operations like the above in your program's
8368 native language, and allowing @value{GDBN} to output values in a manner
8369 consistent with the syntax of your program's native language. The
8370 language you use to build expressions is called the @dfn{working
8374 * Setting:: Switching between source languages
8375 * Show:: Displaying the language
8376 * Checks:: Type and range checks
8377 * Supported languages:: Supported languages
8378 * Unsupported languages:: Unsupported languages
8382 @section Switching between source languages
8384 There are two ways to control the working language---either have @value{GDBN}
8385 set it automatically, or select it manually yourself. You can use the
8386 @code{set language} command for either purpose. On startup, @value{GDBN}
8387 defaults to setting the language automatically. The working language is
8388 used to determine how expressions you type are interpreted, how values
8391 In addition to the working language, every source file that
8392 @value{GDBN} knows about has its own working language. For some object
8393 file formats, the compiler might indicate which language a particular
8394 source file is in. However, most of the time @value{GDBN} infers the
8395 language from the name of the file. The language of a source file
8396 controls whether C@t{++} names are demangled---this way @code{backtrace} can
8397 show each frame appropriately for its own language. There is no way to
8398 set the language of a source file from within @value{GDBN}, but you can
8399 set the language associated with a filename extension. @xref{Show, ,
8400 Displaying the language}.
8402 This is most commonly a problem when you use a program, such
8403 as @code{cfront} or @code{f2c}, that generates C but is written in
8404 another language. In that case, make the
8405 program use @code{#line} directives in its C output; that way
8406 @value{GDBN} will know the correct language of the source code of the original
8407 program, and will display that source code, not the generated C code.
8410 * Filenames:: Filename extensions and languages.
8411 * Manually:: Setting the working language manually
8412 * Automatically:: Having @value{GDBN} infer the source language
8416 @subsection List of filename extensions and languages
8418 If a source file name ends in one of the following extensions, then
8419 @value{GDBN} infers that its language is the one indicated.
8440 Objective-C source file
8447 Modula-2 source file
8451 Assembler source file. This actually behaves almost like C, but
8452 @value{GDBN} does not skip over function prologues when stepping.
8455 In addition, you may set the language associated with a filename
8456 extension. @xref{Show, , Displaying the language}.
8459 @subsection Setting the working language
8461 If you allow @value{GDBN} to set the language automatically,
8462 expressions are interpreted the same way in your debugging session and
8465 @kindex set language
8466 If you wish, you may set the language manually. To do this, issue the
8467 command @samp{set language @var{lang}}, where @var{lang} is the name of
8469 @code{c} or @code{modula-2}.
8470 For a list of the supported languages, type @samp{set language}.
8472 Setting the language manually prevents @value{GDBN} from updating the working
8473 language automatically. This can lead to confusion if you try
8474 to debug a program when the working language is not the same as the
8475 source language, when an expression is acceptable to both
8476 languages---but means different things. For instance, if the current
8477 source file were written in C, and @value{GDBN} was parsing Modula-2, a
8485 might not have the effect you intended. In C, this means to add
8486 @code{b} and @code{c} and place the result in @code{a}. The result
8487 printed would be the value of @code{a}. In Modula-2, this means to compare
8488 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
8491 @subsection Having @value{GDBN} infer the source language
8493 To have @value{GDBN} set the working language automatically, use
8494 @samp{set language local} or @samp{set language auto}. @value{GDBN}
8495 then infers the working language. That is, when your program stops in a
8496 frame (usually by encountering a breakpoint), @value{GDBN} sets the
8497 working language to the language recorded for the function in that
8498 frame. If the language for a frame is unknown (that is, if the function
8499 or block corresponding to the frame was defined in a source file that
8500 does not have a recognized extension), the current working language is
8501 not changed, and @value{GDBN} issues a warning.
8503 This may not seem necessary for most programs, which are written
8504 entirely in one source language. However, program modules and libraries
8505 written in one source language can be used by a main program written in
8506 a different source language. Using @samp{set language auto} in this
8507 case frees you from having to set the working language manually.
8510 @section Displaying the language
8512 The following commands help you find out which language is the
8513 working language, and also what language source files were written in.
8517 @kindex show language
8518 Display the current working language. This is the
8519 language you can use with commands such as @code{print} to
8520 build and compute expressions that may involve variables in your program.
8523 @kindex info frame@r{, show the source language}
8524 Display the source language for this frame. This language becomes the
8525 working language if you use an identifier from this frame.
8526 @xref{Frame Info, ,Information about a frame}, to identify the other
8527 information listed here.
8530 @kindex info source@r{, show the source language}
8531 Display the source language of this source file.
8532 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
8533 information listed here.
8536 In unusual circumstances, you may have source files with extensions
8537 not in the standard list. You can then set the extension associated
8538 with a language explicitly:
8541 @item set extension-language @var{ext} @var{language}
8542 @kindex set extension-language
8543 Tell @value{GDBN} that source files with extension @var{ext} are to be
8544 assumed as written in the source language @var{language}.
8546 @item info extensions
8547 @kindex info extensions
8548 List all the filename extensions and the associated languages.
8552 @section Type and range checking
8555 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
8556 checking are included, but they do not yet have any effect. This
8557 section documents the intended facilities.
8559 @c FIXME remove warning when type/range code added
8561 Some languages are designed to guard you against making seemingly common
8562 errors through a series of compile- and run-time checks. These include
8563 checking the type of arguments to functions and operators, and making
8564 sure mathematical overflows are caught at run time. Checks such as
8565 these help to ensure a program's correctness once it has been compiled
8566 by eliminating type mismatches, and providing active checks for range
8567 errors when your program is running.
8569 @value{GDBN} can check for conditions like the above if you wish.
8570 Although @value{GDBN} does not check the statements in your program,
8571 it can check expressions entered directly into @value{GDBN} for
8572 evaluation via the @code{print} command, for example. As with the
8573 working language, @value{GDBN} can also decide whether or not to check
8574 automatically based on your program's source language.
8575 @xref{Supported languages, ,Supported languages}, for the default
8576 settings of supported languages.
8579 * Type Checking:: An overview of type checking
8580 * Range Checking:: An overview of range checking
8583 @cindex type checking
8584 @cindex checks, type
8586 @subsection An overview of type checking
8588 Some languages, such as Modula-2, are strongly typed, meaning that the
8589 arguments to operators and functions have to be of the correct type,
8590 otherwise an error occurs. These checks prevent type mismatch
8591 errors from ever causing any run-time problems. For example,
8599 The second example fails because the @code{CARDINAL} 1 is not
8600 type-compatible with the @code{REAL} 2.3.
8602 For the expressions you use in @value{GDBN} commands, you can tell the
8603 @value{GDBN} type checker to skip checking;
8604 to treat any mismatches as errors and abandon the expression;
8605 or to only issue warnings when type mismatches occur,
8606 but evaluate the expression anyway. When you choose the last of
8607 these, @value{GDBN} evaluates expressions like the second example above, but
8608 also issues a warning.
8610 Even if you turn type checking off, there may be other reasons
8611 related to type that prevent @value{GDBN} from evaluating an expression.
8612 For instance, @value{GDBN} does not know how to add an @code{int} and
8613 a @code{struct foo}. These particular type errors have nothing to do
8614 with the language in use, and usually arise from expressions, such as
8615 the one described above, which make little sense to evaluate anyway.
8617 Each language defines to what degree it is strict about type. For
8618 instance, both Modula-2 and C require the arguments to arithmetical
8619 operators to be numbers. In C, enumerated types and pointers can be
8620 represented as numbers, so that they are valid arguments to mathematical
8621 operators. @xref{Supported languages, ,Supported languages}, for further
8622 details on specific languages.
8624 @value{GDBN} provides some additional commands for controlling the type checker:
8626 @kindex set check type
8627 @kindex show check type
8629 @item set check type auto
8630 Set type checking on or off based on the current working language.
8631 @xref{Supported languages, ,Supported languages}, for the default settings for
8634 @item set check type on
8635 @itemx set check type off
8636 Set type checking on or off, overriding the default setting for the
8637 current working language. Issue a warning if the setting does not
8638 match the language default. If any type mismatches occur in
8639 evaluating an expression while type checking is on, @value{GDBN} prints a
8640 message and aborts evaluation of the expression.
8642 @item set check type warn
8643 Cause the type checker to issue warnings, but to always attempt to
8644 evaluate the expression. Evaluating the expression may still
8645 be impossible for other reasons. For example, @value{GDBN} cannot add
8646 numbers and structures.
8649 Show the current setting of the type checker, and whether or not @value{GDBN}
8650 is setting it automatically.
8653 @cindex range checking
8654 @cindex checks, range
8655 @node Range Checking
8656 @subsection An overview of range checking
8658 In some languages (such as Modula-2), it is an error to exceed the
8659 bounds of a type; this is enforced with run-time checks. Such range
8660 checking is meant to ensure program correctness by making sure
8661 computations do not overflow, or indices on an array element access do
8662 not exceed the bounds of the array.
8664 For expressions you use in @value{GDBN} commands, you can tell
8665 @value{GDBN} to treat range errors in one of three ways: ignore them,
8666 always treat them as errors and abandon the expression, or issue
8667 warnings but evaluate the expression anyway.
8669 A range error can result from numerical overflow, from exceeding an
8670 array index bound, or when you type a constant that is not a member
8671 of any type. Some languages, however, do not treat overflows as an
8672 error. In many implementations of C, mathematical overflow causes the
8673 result to ``wrap around'' to lower values---for example, if @var{m} is
8674 the largest integer value, and @var{s} is the smallest, then
8677 @var{m} + 1 @result{} @var{s}
8680 This, too, is specific to individual languages, and in some cases
8681 specific to individual compilers or machines. @xref{Supported languages, ,
8682 Supported languages}, for further details on specific languages.
8684 @value{GDBN} provides some additional commands for controlling the range checker:
8686 @kindex set check range
8687 @kindex show check range
8689 @item set check range auto
8690 Set range checking on or off based on the current working language.
8691 @xref{Supported languages, ,Supported languages}, for the default settings for
8694 @item set check range on
8695 @itemx set check range off
8696 Set range checking on or off, overriding the default setting for the
8697 current working language. A warning is issued if the setting does not
8698 match the language default. If a range error occurs and range checking is on,
8699 then a message is printed and evaluation of the expression is aborted.
8701 @item set check range warn
8702 Output messages when the @value{GDBN} range checker detects a range error,
8703 but attempt to evaluate the expression anyway. Evaluating the
8704 expression may still be impossible for other reasons, such as accessing
8705 memory that the process does not own (a typical example from many Unix
8709 Show the current setting of the range checker, and whether or not it is
8710 being set automatically by @value{GDBN}.
8713 @node Supported languages
8714 @section Supported languages
8716 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
8717 assembly, Modula-2, and Ada.
8718 @c This is false ...
8719 Some @value{GDBN} features may be used in expressions regardless of the
8720 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
8721 and the @samp{@{type@}addr} construct (@pxref{Expressions,
8722 ,Expressions}) can be used with the constructs of any supported
8725 The following sections detail to what degree each source language is
8726 supported by @value{GDBN}. These sections are not meant to be language
8727 tutorials or references, but serve only as a reference guide to what the
8728 @value{GDBN} expression parser accepts, and what input and output
8729 formats should look like for different languages. There are many good
8730 books written on each of these languages; please look to these for a
8731 language reference or tutorial.
8735 * Objective-C:: Objective-C
8738 * Modula-2:: Modula-2
8743 @subsection C and C@t{++}
8745 @cindex C and C@t{++}
8746 @cindex expressions in C or C@t{++}
8748 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
8749 to both languages. Whenever this is the case, we discuss those languages
8753 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
8754 @cindex @sc{gnu} C@t{++}
8755 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
8756 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
8757 effectively, you must compile your C@t{++} programs with a supported
8758 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
8759 compiler (@code{aCC}).
8761 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
8762 format; if it doesn't work on your system, try the stabs+ debugging
8763 format. You can select those formats explicitly with the @code{g++}
8764 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
8765 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
8766 CC, gcc.info, Using @sc{gnu} CC}.
8769 * C Operators:: C and C@t{++} operators
8770 * C Constants:: C and C@t{++} constants
8771 * C plus plus expressions:: C@t{++} expressions
8772 * C Defaults:: Default settings for C and C@t{++}
8773 * C Checks:: C and C@t{++} type and range checks
8774 * Debugging C:: @value{GDBN} and C
8775 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
8779 @subsubsection C and C@t{++} operators
8781 @cindex C and C@t{++} operators
8783 Operators must be defined on values of specific types. For instance,
8784 @code{+} is defined on numbers, but not on structures. Operators are
8785 often defined on groups of types.
8787 For the purposes of C and C@t{++}, the following definitions hold:
8792 @emph{Integral types} include @code{int} with any of its storage-class
8793 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
8796 @emph{Floating-point types} include @code{float}, @code{double}, and
8797 @code{long double} (if supported by the target platform).
8800 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
8803 @emph{Scalar types} include all of the above.
8808 The following operators are supported. They are listed here
8809 in order of increasing precedence:
8813 The comma or sequencing operator. Expressions in a comma-separated list
8814 are evaluated from left to right, with the result of the entire
8815 expression being the last expression evaluated.
8818 Assignment. The value of an assignment expression is the value
8819 assigned. Defined on scalar types.
8822 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
8823 and translated to @w{@code{@var{a} = @var{a op b}}}.
8824 @w{@code{@var{op}=}} and @code{=} have the same precedence.
8825 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
8826 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
8829 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
8830 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
8834 Logical @sc{or}. Defined on integral types.
8837 Logical @sc{and}. Defined on integral types.
8840 Bitwise @sc{or}. Defined on integral types.
8843 Bitwise exclusive-@sc{or}. Defined on integral types.
8846 Bitwise @sc{and}. Defined on integral types.
8849 Equality and inequality. Defined on scalar types. The value of these
8850 expressions is 0 for false and non-zero for true.
8852 @item <@r{, }>@r{, }<=@r{, }>=
8853 Less than, greater than, less than or equal, greater than or equal.
8854 Defined on scalar types. The value of these expressions is 0 for false
8855 and non-zero for true.
8858 left shift, and right shift. Defined on integral types.
8861 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8864 Addition and subtraction. Defined on integral types, floating-point types and
8867 @item *@r{, }/@r{, }%
8868 Multiplication, division, and modulus. Multiplication and division are
8869 defined on integral and floating-point types. Modulus is defined on
8873 Increment and decrement. When appearing before a variable, the
8874 operation is performed before the variable is used in an expression;
8875 when appearing after it, the variable's value is used before the
8876 operation takes place.
8879 Pointer dereferencing. Defined on pointer types. Same precedence as
8883 Address operator. Defined on variables. Same precedence as @code{++}.
8885 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
8886 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
8887 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
8888 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
8892 Negative. Defined on integral and floating-point types. Same
8893 precedence as @code{++}.
8896 Logical negation. Defined on integral types. Same precedence as
8900 Bitwise complement operator. Defined on integral types. Same precedence as
8905 Structure member, and pointer-to-structure member. For convenience,
8906 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
8907 pointer based on the stored type information.
8908 Defined on @code{struct} and @code{union} data.
8911 Dereferences of pointers to members.
8914 Array indexing. @code{@var{a}[@var{i}]} is defined as
8915 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
8918 Function parameter list. Same precedence as @code{->}.
8921 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
8922 and @code{class} types.
8925 Doubled colons also represent the @value{GDBN} scope operator
8926 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
8930 If an operator is redefined in the user code, @value{GDBN} usually
8931 attempts to invoke the redefined version instead of using the operator's
8939 @subsubsection C and C@t{++} constants
8941 @cindex C and C@t{++} constants
8943 @value{GDBN} allows you to express the constants of C and C@t{++} in the
8948 Integer constants are a sequence of digits. Octal constants are
8949 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
8950 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
8951 @samp{l}, specifying that the constant should be treated as a
8955 Floating point constants are a sequence of digits, followed by a decimal
8956 point, followed by a sequence of digits, and optionally followed by an
8957 exponent. An exponent is of the form:
8958 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
8959 sequence of digits. The @samp{+} is optional for positive exponents.
8960 A floating-point constant may also end with a letter @samp{f} or
8961 @samp{F}, specifying that the constant should be treated as being of
8962 the @code{float} (as opposed to the default @code{double}) type; or with
8963 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
8967 Enumerated constants consist of enumerated identifiers, or their
8968 integral equivalents.
8971 Character constants are a single character surrounded by single quotes
8972 (@code{'}), or a number---the ordinal value of the corresponding character
8973 (usually its @sc{ascii} value). Within quotes, the single character may
8974 be represented by a letter or by @dfn{escape sequences}, which are of
8975 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
8976 of the character's ordinal value; or of the form @samp{\@var{x}}, where
8977 @samp{@var{x}} is a predefined special character---for example,
8978 @samp{\n} for newline.
8981 String constants are a sequence of character constants surrounded by
8982 double quotes (@code{"}). Any valid character constant (as described
8983 above) may appear. Double quotes within the string must be preceded by
8984 a backslash, so for instance @samp{"a\"b'c"} is a string of five
8988 Pointer constants are an integral value. You can also write pointers
8989 to constants using the C operator @samp{&}.
8992 Array constants are comma-separated lists surrounded by braces @samp{@{}
8993 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
8994 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
8995 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
8999 * C plus plus expressions::
9006 @node C plus plus expressions
9007 @subsubsection C@t{++} expressions
9009 @cindex expressions in C@t{++}
9010 @value{GDBN} expression handling can interpret most C@t{++} expressions.
9012 @cindex debugging C@t{++} programs
9013 @cindex C@t{++} compilers
9014 @cindex debug formats and C@t{++}
9015 @cindex @value{NGCC} and C@t{++}
9017 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
9018 proper compiler and the proper debug format. Currently, @value{GDBN}
9019 works best when debugging C@t{++} code that is compiled with
9020 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
9021 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
9022 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
9023 stabs+ as their default debug format, so you usually don't need to
9024 specify a debug format explicitly. Other compilers and/or debug formats
9025 are likely to work badly or not at all when using @value{GDBN} to debug
9031 @cindex member functions
9033 Member function calls are allowed; you can use expressions like
9036 count = aml->GetOriginal(x, y)
9039 @vindex this@r{, inside C@t{++} member functions}
9040 @cindex namespace in C@t{++}
9042 While a member function is active (in the selected stack frame), your
9043 expressions have the same namespace available as the member function;
9044 that is, @value{GDBN} allows implicit references to the class instance
9045 pointer @code{this} following the same rules as C@t{++}.
9047 @cindex call overloaded functions
9048 @cindex overloaded functions, calling
9049 @cindex type conversions in C@t{++}
9051 You can call overloaded functions; @value{GDBN} resolves the function
9052 call to the right definition, with some restrictions. @value{GDBN} does not
9053 perform overload resolution involving user-defined type conversions,
9054 calls to constructors, or instantiations of templates that do not exist
9055 in the program. It also cannot handle ellipsis argument lists or
9058 It does perform integral conversions and promotions, floating-point
9059 promotions, arithmetic conversions, pointer conversions, conversions of
9060 class objects to base classes, and standard conversions such as those of
9061 functions or arrays to pointers; it requires an exact match on the
9062 number of function arguments.
9064 Overload resolution is always performed, unless you have specified
9065 @code{set overload-resolution off}. @xref{Debugging C plus plus,
9066 ,@value{GDBN} features for C@t{++}}.
9068 You must specify @code{set overload-resolution off} in order to use an
9069 explicit function signature to call an overloaded function, as in
9071 p 'foo(char,int)'('x', 13)
9074 The @value{GDBN} command-completion facility can simplify this;
9075 see @ref{Completion, ,Command completion}.
9077 @cindex reference declarations
9079 @value{GDBN} understands variables declared as C@t{++} references; you can use
9080 them in expressions just as you do in C@t{++} source---they are automatically
9083 In the parameter list shown when @value{GDBN} displays a frame, the values of
9084 reference variables are not displayed (unlike other variables); this
9085 avoids clutter, since references are often used for large structures.
9086 The @emph{address} of a reference variable is always shown, unless
9087 you have specified @samp{set print address off}.
9090 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
9091 expressions can use it just as expressions in your program do. Since
9092 one scope may be defined in another, you can use @code{::} repeatedly if
9093 necessary, for example in an expression like
9094 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
9095 resolving name scope by reference to source files, in both C and C@t{++}
9096 debugging (@pxref{Variables, ,Program variables}).
9099 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
9100 calling virtual functions correctly, printing out virtual bases of
9101 objects, calling functions in a base subobject, casting objects, and
9102 invoking user-defined operators.
9105 @subsubsection C and C@t{++} defaults
9107 @cindex C and C@t{++} defaults
9109 If you allow @value{GDBN} to set type and range checking automatically, they
9110 both default to @code{off} whenever the working language changes to
9111 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
9112 selects the working language.
9114 If you allow @value{GDBN} to set the language automatically, it
9115 recognizes source files whose names end with @file{.c}, @file{.C}, or
9116 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
9117 these files, it sets the working language to C or C@t{++}.
9118 @xref{Automatically, ,Having @value{GDBN} infer the source language},
9119 for further details.
9121 @c Type checking is (a) primarily motivated by Modula-2, and (b)
9122 @c unimplemented. If (b) changes, it might make sense to let this node
9123 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
9126 @subsubsection C and C@t{++} type and range checks
9128 @cindex C and C@t{++} checks
9130 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
9131 is not used. However, if you turn type checking on, @value{GDBN}
9132 considers two variables type equivalent if:
9136 The two variables are structured and have the same structure, union, or
9140 The two variables have the same type name, or types that have been
9141 declared equivalent through @code{typedef}.
9144 @c leaving this out because neither J Gilmore nor R Pesch understand it.
9147 The two @code{struct}, @code{union}, or @code{enum} variables are
9148 declared in the same declaration. (Note: this may not be true for all C
9153 Range checking, if turned on, is done on mathematical operations. Array
9154 indices are not checked, since they are often used to index a pointer
9155 that is not itself an array.
9158 @subsubsection @value{GDBN} and C
9160 The @code{set print union} and @code{show print union} commands apply to
9161 the @code{union} type. When set to @samp{on}, any @code{union} that is
9162 inside a @code{struct} or @code{class} is also printed. Otherwise, it
9163 appears as @samp{@{...@}}.
9165 The @code{@@} operator aids in the debugging of dynamic arrays, formed
9166 with pointers and a memory allocation function. @xref{Expressions,
9170 * Debugging C plus plus::
9173 @node Debugging C plus plus
9174 @subsubsection @value{GDBN} features for C@t{++}
9176 @cindex commands for C@t{++}
9178 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
9179 designed specifically for use with C@t{++}. Here is a summary:
9182 @cindex break in overloaded functions
9183 @item @r{breakpoint menus}
9184 When you want a breakpoint in a function whose name is overloaded,
9185 @value{GDBN} breakpoint menus help you specify which function definition
9186 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
9188 @cindex overloading in C@t{++}
9189 @item rbreak @var{regex}
9190 Setting breakpoints using regular expressions is helpful for setting
9191 breakpoints on overloaded functions that are not members of any special
9193 @xref{Set Breaks, ,Setting breakpoints}.
9195 @cindex C@t{++} exception handling
9198 Debug C@t{++} exception handling using these commands. @xref{Set
9199 Catchpoints, , Setting catchpoints}.
9202 @item ptype @var{typename}
9203 Print inheritance relationships as well as other information for type
9205 @xref{Symbols, ,Examining the Symbol Table}.
9207 @cindex C@t{++} symbol display
9208 @item set print demangle
9209 @itemx show print demangle
9210 @itemx set print asm-demangle
9211 @itemx show print asm-demangle
9212 Control whether C@t{++} symbols display in their source form, both when
9213 displaying code as C@t{++} source and when displaying disassemblies.
9214 @xref{Print Settings, ,Print settings}.
9216 @item set print object
9217 @itemx show print object
9218 Choose whether to print derived (actual) or declared types of objects.
9219 @xref{Print Settings, ,Print settings}.
9221 @item set print vtbl
9222 @itemx show print vtbl
9223 Control the format for printing virtual function tables.
9224 @xref{Print Settings, ,Print settings}.
9225 (The @code{vtbl} commands do not work on programs compiled with the HP
9226 ANSI C@t{++} compiler (@code{aCC}).)
9228 @kindex set overload-resolution
9229 @cindex overloaded functions, overload resolution
9230 @item set overload-resolution on
9231 Enable overload resolution for C@t{++} expression evaluation. The default
9232 is on. For overloaded functions, @value{GDBN} evaluates the arguments
9233 and searches for a function whose signature matches the argument types,
9234 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
9235 expressions}, for details). If it cannot find a match, it emits a
9238 @item set overload-resolution off
9239 Disable overload resolution for C@t{++} expression evaluation. For
9240 overloaded functions that are not class member functions, @value{GDBN}
9241 chooses the first function of the specified name that it finds in the
9242 symbol table, whether or not its arguments are of the correct type. For
9243 overloaded functions that are class member functions, @value{GDBN}
9244 searches for a function whose signature @emph{exactly} matches the
9247 @kindex show overload-resolution
9248 @item show overload-resolution
9249 Show the current setting of overload resolution.
9251 @item @r{Overloaded symbol names}
9252 You can specify a particular definition of an overloaded symbol, using
9253 the same notation that is used to declare such symbols in C@t{++}: type
9254 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
9255 also use the @value{GDBN} command-line word completion facilities to list the
9256 available choices, or to finish the type list for you.
9257 @xref{Completion,, Command completion}, for details on how to do this.
9261 @subsection Objective-C
9264 This section provides information about some commands and command
9265 options that are useful for debugging Objective-C code. See also
9266 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
9267 few more commands specific to Objective-C support.
9270 * Method Names in Commands::
9271 * The Print Command with Objective-C::
9274 @node Method Names in Commands, The Print Command with Objective-C, Objective-C, Objective-C
9275 @subsubsection Method Names in Commands
9277 The following commands have been extended to accept Objective-C method
9278 names as line specifications:
9280 @kindex clear@r{, and Objective-C}
9281 @kindex break@r{, and Objective-C}
9282 @kindex info line@r{, and Objective-C}
9283 @kindex jump@r{, and Objective-C}
9284 @kindex list@r{, and Objective-C}
9288 @item @code{info line}
9293 A fully qualified Objective-C method name is specified as
9296 -[@var{Class} @var{methodName}]
9299 where the minus sign is used to indicate an instance method and a
9300 plus sign (not shown) is used to indicate a class method. The class
9301 name @var{Class} and method name @var{methodName} are enclosed in
9302 brackets, similar to the way messages are specified in Objective-C
9303 source code. For example, to set a breakpoint at the @code{create}
9304 instance method of class @code{Fruit} in the program currently being
9308 break -[Fruit create]
9311 To list ten program lines around the @code{initialize} class method,
9315 list +[NSText initialize]
9318 In the current version of @value{GDBN}, the plus or minus sign is
9319 required. In future versions of @value{GDBN}, the plus or minus
9320 sign will be optional, but you can use it to narrow the search. It
9321 is also possible to specify just a method name:
9327 You must specify the complete method name, including any colons. If
9328 your program's source files contain more than one @code{create} method,
9329 you'll be presented with a numbered list of classes that implement that
9330 method. Indicate your choice by number, or type @samp{0} to exit if
9333 As another example, to clear a breakpoint established at the
9334 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
9337 clear -[NSWindow makeKeyAndOrderFront:]
9340 @node The Print Command with Objective-C
9341 @subsubsection The Print Command With Objective-C
9342 @cindex Objective-C, print objects
9343 @kindex print-object
9344 @kindex po @r{(@code{print-object})}
9346 The print command has also been extended to accept methods. For example:
9349 print -[@var{object} hash]
9352 @cindex print an Objective-C object description
9353 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
9355 will tell @value{GDBN} to send the @code{hash} message to @var{object}
9356 and print the result. Also, an additional command has been added,
9357 @code{print-object} or @code{po} for short, which is meant to print
9358 the description of an object. However, this command may only work
9359 with certain Objective-C libraries that have a particular hook
9360 function, @code{_NSPrintForDebugger}, defined.
9364 @cindex Fortran-specific support in @value{GDBN}
9366 @value{GDBN} can be used to debug programs written in Fortran, but it
9367 currently supports only the features of Fortran 77 language.
9369 @cindex trailing underscore, in Fortran symbols
9370 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
9371 among them) append an underscore to the names of variables and
9372 functions. When you debug programs compiled by those compilers, you
9373 will need to refer to variables and functions with a trailing
9377 * Fortran Operators:: Fortran operators and expressions
9378 * Fortran Defaults:: Default settings for Fortran
9379 * Special Fortran commands:: Special @value{GDBN} commands for Fortran
9382 @node Fortran Operators
9383 @subsubsection Fortran operators and expressions
9385 @cindex Fortran operators and expressions
9387 Operators must be defined on values of specific types. For instance,
9388 @code{+} is defined on numbers, but not on characters or other non-
9389 arithmetic types. Operators are often defined on groups of types.
9393 The exponentiation operator. It raises the first operand to the power
9397 The range operator. Normally used in the form of array(low:high) to
9398 represent a section of array.
9401 @node Fortran Defaults
9402 @subsubsection Fortran Defaults
9404 @cindex Fortran Defaults
9406 Fortran symbols are usually case-insensitive, so @value{GDBN} by
9407 default uses case-insensitive matches for Fortran symbols. You can
9408 change that with the @samp{set case-insensitive} command, see
9409 @ref{Symbols}, for the details.
9411 @node Special Fortran commands
9412 @subsubsection Special Fortran commands
9414 @cindex Special Fortran commands
9416 @value{GDBN} had some commands to support Fortran specific feature,
9417 such as common block displaying.
9420 @cindex @code{COMMON} blocks, Fortran
9422 @item info common @r{[}@var{common-name}@r{]}
9423 This command prints the values contained in the Fortran @code{COMMON}
9424 block whose name is @var{common-name}. With no argument, the names of
9425 all @code{COMMON} blocks visible at current program location are
9432 @cindex Pascal support in @value{GDBN}, limitations
9433 Debugging Pascal programs which use sets, subranges, file variables, or
9434 nested functions does not currently work. @value{GDBN} does not support
9435 entering expressions, printing values, or similar features using Pascal
9438 The Pascal-specific command @code{set print pascal_static-members}
9439 controls whether static members of Pascal objects are displayed.
9440 @xref{Print Settings, pascal_static-members}.
9443 @subsection Modula-2
9445 @cindex Modula-2, @value{GDBN} support
9447 The extensions made to @value{GDBN} to support Modula-2 only support
9448 output from the @sc{gnu} Modula-2 compiler (which is currently being
9449 developed). Other Modula-2 compilers are not currently supported, and
9450 attempting to debug executables produced by them is most likely
9451 to give an error as @value{GDBN} reads in the executable's symbol
9454 @cindex expressions in Modula-2
9456 * M2 Operators:: Built-in operators
9457 * Built-In Func/Proc:: Built-in functions and procedures
9458 * M2 Constants:: Modula-2 constants
9459 * M2 Defaults:: Default settings for Modula-2
9460 * Deviations:: Deviations from standard Modula-2
9461 * M2 Checks:: Modula-2 type and range checks
9462 * M2 Scope:: The scope operators @code{::} and @code{.}
9463 * GDB/M2:: @value{GDBN} and Modula-2
9467 @subsubsection Operators
9468 @cindex Modula-2 operators
9470 Operators must be defined on values of specific types. For instance,
9471 @code{+} is defined on numbers, but not on structures. Operators are
9472 often defined on groups of types. For the purposes of Modula-2, the
9473 following definitions hold:
9478 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
9482 @emph{Character types} consist of @code{CHAR} and its subranges.
9485 @emph{Floating-point types} consist of @code{REAL}.
9488 @emph{Pointer types} consist of anything declared as @code{POINTER TO
9492 @emph{Scalar types} consist of all of the above.
9495 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
9498 @emph{Boolean types} consist of @code{BOOLEAN}.
9502 The following operators are supported, and appear in order of
9503 increasing precedence:
9507 Function argument or array index separator.
9510 Assignment. The value of @var{var} @code{:=} @var{value} is
9514 Less than, greater than on integral, floating-point, or enumerated
9518 Less than or equal to, greater than or equal to
9519 on integral, floating-point and enumerated types, or set inclusion on
9520 set types. Same precedence as @code{<}.
9522 @item =@r{, }<>@r{, }#
9523 Equality and two ways of expressing inequality, valid on scalar types.
9524 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
9525 available for inequality, since @code{#} conflicts with the script
9529 Set membership. Defined on set types and the types of their members.
9530 Same precedence as @code{<}.
9533 Boolean disjunction. Defined on boolean types.
9536 Boolean conjunction. Defined on boolean types.
9539 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9542 Addition and subtraction on integral and floating-point types, or union
9543 and difference on set types.
9546 Multiplication on integral and floating-point types, or set intersection
9550 Division on floating-point types, or symmetric set difference on set
9551 types. Same precedence as @code{*}.
9554 Integer division and remainder. Defined on integral types. Same
9555 precedence as @code{*}.
9558 Negative. Defined on @code{INTEGER} and @code{REAL} data.
9561 Pointer dereferencing. Defined on pointer types.
9564 Boolean negation. Defined on boolean types. Same precedence as
9568 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
9569 precedence as @code{^}.
9572 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
9575 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
9579 @value{GDBN} and Modula-2 scope operators.
9583 @emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
9584 treats the use of the operator @code{IN}, or the use of operators
9585 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
9586 @code{<=}, and @code{>=} on sets as an error.
9590 @node Built-In Func/Proc
9591 @subsubsection Built-in functions and procedures
9592 @cindex Modula-2 built-ins
9594 Modula-2 also makes available several built-in procedures and functions.
9595 In describing these, the following metavariables are used:
9600 represents an @code{ARRAY} variable.
9603 represents a @code{CHAR} constant or variable.
9606 represents a variable or constant of integral type.
9609 represents an identifier that belongs to a set. Generally used in the
9610 same function with the metavariable @var{s}. The type of @var{s} should
9611 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
9614 represents a variable or constant of integral or floating-point type.
9617 represents a variable or constant of floating-point type.
9623 represents a variable.
9626 represents a variable or constant of one of many types. See the
9627 explanation of the function for details.
9630 All Modula-2 built-in procedures also return a result, described below.
9634 Returns the absolute value of @var{n}.
9637 If @var{c} is a lower case letter, it returns its upper case
9638 equivalent, otherwise it returns its argument.
9641 Returns the character whose ordinal value is @var{i}.
9644 Decrements the value in the variable @var{v} by one. Returns the new value.
9646 @item DEC(@var{v},@var{i})
9647 Decrements the value in the variable @var{v} by @var{i}. Returns the
9650 @item EXCL(@var{m},@var{s})
9651 Removes the element @var{m} from the set @var{s}. Returns the new
9654 @item FLOAT(@var{i})
9655 Returns the floating point equivalent of the integer @var{i}.
9658 Returns the index of the last member of @var{a}.
9661 Increments the value in the variable @var{v} by one. Returns the new value.
9663 @item INC(@var{v},@var{i})
9664 Increments the value in the variable @var{v} by @var{i}. Returns the
9667 @item INCL(@var{m},@var{s})
9668 Adds the element @var{m} to the set @var{s} if it is not already
9669 there. Returns the new set.
9672 Returns the maximum value of the type @var{t}.
9675 Returns the minimum value of the type @var{t}.
9678 Returns boolean TRUE if @var{i} is an odd number.
9681 Returns the ordinal value of its argument. For example, the ordinal
9682 value of a character is its @sc{ascii} value (on machines supporting the
9683 @sc{ascii} character set). @var{x} must be of an ordered type, which include
9684 integral, character and enumerated types.
9687 Returns the size of its argument. @var{x} can be a variable or a type.
9689 @item TRUNC(@var{r})
9690 Returns the integral part of @var{r}.
9692 @item VAL(@var{t},@var{i})
9693 Returns the member of the type @var{t} whose ordinal value is @var{i}.
9697 @emph{Warning:} Sets and their operations are not yet supported, so
9698 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
9702 @cindex Modula-2 constants
9704 @subsubsection Constants
9706 @value{GDBN} allows you to express the constants of Modula-2 in the following
9712 Integer constants are simply a sequence of digits. When used in an
9713 expression, a constant is interpreted to be type-compatible with the
9714 rest of the expression. Hexadecimal integers are specified by a
9715 trailing @samp{H}, and octal integers by a trailing @samp{B}.
9718 Floating point constants appear as a sequence of digits, followed by a
9719 decimal point and another sequence of digits. An optional exponent can
9720 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
9721 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
9722 digits of the floating point constant must be valid decimal (base 10)
9726 Character constants consist of a single character enclosed by a pair of
9727 like quotes, either single (@code{'}) or double (@code{"}). They may
9728 also be expressed by their ordinal value (their @sc{ascii} value, usually)
9729 followed by a @samp{C}.
9732 String constants consist of a sequence of characters enclosed by a
9733 pair of like quotes, either single (@code{'}) or double (@code{"}).
9734 Escape sequences in the style of C are also allowed. @xref{C
9735 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
9739 Enumerated constants consist of an enumerated identifier.
9742 Boolean constants consist of the identifiers @code{TRUE} and
9746 Pointer constants consist of integral values only.
9749 Set constants are not yet supported.
9753 @subsubsection Modula-2 defaults
9754 @cindex Modula-2 defaults
9756 If type and range checking are set automatically by @value{GDBN}, they
9757 both default to @code{on} whenever the working language changes to
9758 Modula-2. This happens regardless of whether you or @value{GDBN}
9759 selected the working language.
9761 If you allow @value{GDBN} to set the language automatically, then entering
9762 code compiled from a file whose name ends with @file{.mod} sets the
9763 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
9764 the language automatically}, for further details.
9767 @subsubsection Deviations from standard Modula-2
9768 @cindex Modula-2, deviations from
9770 A few changes have been made to make Modula-2 programs easier to debug.
9771 This is done primarily via loosening its type strictness:
9775 Unlike in standard Modula-2, pointer constants can be formed by
9776 integers. This allows you to modify pointer variables during
9777 debugging. (In standard Modula-2, the actual address contained in a
9778 pointer variable is hidden from you; it can only be modified
9779 through direct assignment to another pointer variable or expression that
9780 returned a pointer.)
9783 C escape sequences can be used in strings and characters to represent
9784 non-printable characters. @value{GDBN} prints out strings with these
9785 escape sequences embedded. Single non-printable characters are
9786 printed using the @samp{CHR(@var{nnn})} format.
9789 The assignment operator (@code{:=}) returns the value of its right-hand
9793 All built-in procedures both modify @emph{and} return their argument.
9797 @subsubsection Modula-2 type and range checks
9798 @cindex Modula-2 checks
9801 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
9804 @c FIXME remove warning when type/range checks added
9806 @value{GDBN} considers two Modula-2 variables type equivalent if:
9810 They are of types that have been declared equivalent via a @code{TYPE
9811 @var{t1} = @var{t2}} statement
9814 They have been declared on the same line. (Note: This is true of the
9815 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
9818 As long as type checking is enabled, any attempt to combine variables
9819 whose types are not equivalent is an error.
9821 Range checking is done on all mathematical operations, assignment, array
9822 index bounds, and all built-in functions and procedures.
9825 @subsubsection The scope operators @code{::} and @code{.}
9827 @cindex @code{.}, Modula-2 scope operator
9828 @cindex colon, doubled as scope operator
9830 @vindex colon-colon@r{, in Modula-2}
9831 @c Info cannot handle :: but TeX can.
9834 @vindex ::@r{, in Modula-2}
9837 There are a few subtle differences between the Modula-2 scope operator
9838 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
9843 @var{module} . @var{id}
9844 @var{scope} :: @var{id}
9848 where @var{scope} is the name of a module or a procedure,
9849 @var{module} the name of a module, and @var{id} is any declared
9850 identifier within your program, except another module.
9852 Using the @code{::} operator makes @value{GDBN} search the scope
9853 specified by @var{scope} for the identifier @var{id}. If it is not
9854 found in the specified scope, then @value{GDBN} searches all scopes
9855 enclosing the one specified by @var{scope}.
9857 Using the @code{.} operator makes @value{GDBN} search the current scope for
9858 the identifier specified by @var{id} that was imported from the
9859 definition module specified by @var{module}. With this operator, it is
9860 an error if the identifier @var{id} was not imported from definition
9861 module @var{module}, or if @var{id} is not an identifier in
9865 @subsubsection @value{GDBN} and Modula-2
9867 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
9868 Five subcommands of @code{set print} and @code{show print} apply
9869 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
9870 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
9871 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
9872 analogue in Modula-2.
9874 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
9875 with any language, is not useful with Modula-2. Its
9876 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
9877 created in Modula-2 as they can in C or C@t{++}. However, because an
9878 address can be specified by an integral constant, the construct
9879 @samp{@{@var{type}@}@var{adrexp}} is still useful.
9881 @cindex @code{#} in Modula-2
9882 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
9883 interpreted as the beginning of a comment. Use @code{<>} instead.
9889 The extensions made to @value{GDBN} for Ada only support
9890 output from the @sc{gnu} Ada (GNAT) compiler.
9891 Other Ada compilers are not currently supported, and
9892 attempting to debug executables produced by them is most likely
9896 @cindex expressions in Ada
9898 * Ada Mode Intro:: General remarks on the Ada syntax
9899 and semantics supported by Ada mode
9901 * Omissions from Ada:: Restrictions on the Ada expression syntax.
9902 * Additions to Ada:: Extensions of the Ada expression syntax.
9903 * Stopping Before Main Program:: Debugging the program during elaboration.
9904 * Ada Glitches:: Known peculiarities of Ada mode.
9907 @node Ada Mode Intro
9908 @subsubsection Introduction
9909 @cindex Ada mode, general
9911 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
9912 syntax, with some extensions.
9913 The philosophy behind the design of this subset is
9917 That @value{GDBN} should provide basic literals and access to operations for
9918 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
9919 leaving more sophisticated computations to subprograms written into the
9920 program (which therefore may be called from @value{GDBN}).
9923 That type safety and strict adherence to Ada language restrictions
9924 are not particularly important to the @value{GDBN} user.
9927 That brevity is important to the @value{GDBN} user.
9930 Thus, for brevity, the debugger acts as if there were
9931 implicit @code{with} and @code{use} clauses in effect for all user-written
9932 packages, making it unnecessary to fully qualify most names with
9933 their packages, regardless of context. Where this causes ambiguity,
9934 @value{GDBN} asks the user's intent.
9936 The debugger will start in Ada mode if it detects an Ada main program.
9937 As for other languages, it will enter Ada mode when stopped in a program that
9938 was translated from an Ada source file.
9940 While in Ada mode, you may use `@t{--}' for comments. This is useful
9941 mostly for documenting command files. The standard @value{GDBN} comment
9942 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
9943 middle (to allow based literals).
9945 The debugger supports limited overloading. Given a subprogram call in which
9946 the function symbol has multiple definitions, it will use the number of
9947 actual parameters and some information about their types to attempt to narrow
9948 the set of definitions. It also makes very limited use of context, preferring
9949 procedures to functions in the context of the @code{call} command, and
9950 functions to procedures elsewhere.
9952 @node Omissions from Ada
9953 @subsubsection Omissions from Ada
9954 @cindex Ada, omissions from
9956 Here are the notable omissions from the subset:
9960 Only a subset of the attributes are supported:
9964 @t{'First}, @t{'Last}, and @t{'Length}
9965 on array objects (not on types and subtypes).
9968 @t{'Min} and @t{'Max}.
9971 @t{'Pos} and @t{'Val}.
9977 @t{'Range} on array objects (not subtypes), but only as the right
9978 operand of the membership (@code{in}) operator.
9981 @t{'Access}, @t{'Unchecked_Access}, and
9982 @t{'Unrestricted_Access} (a GNAT extension).
9990 @code{Characters.Latin_1} are not available and
9991 concatenation is not implemented. Thus, escape characters in strings are
9992 not currently available.
9995 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
9996 equality of representations. They will generally work correctly
9997 for strings and arrays whose elements have integer or enumeration types.
9998 They may not work correctly for arrays whose element
9999 types have user-defined equality, for arrays of real values
10000 (in particular, IEEE-conformant floating point, because of negative
10001 zeroes and NaNs), and for arrays whose elements contain unused bits with
10002 indeterminate values.
10005 The other component-by-component array operations (@code{and}, @code{or},
10006 @code{xor}, @code{not}, and relational tests other than equality)
10007 are not implemented.
10010 @cindex array aggregates (Ada)
10011 @cindex record aggregates (Ada)
10012 @cindex aggregates (Ada)
10013 There is limited support for array and record aggregates. They are
10014 permitted only on the right sides of assignments, as in these examples:
10017 set An_Array := (1, 2, 3, 4, 5, 6)
10018 set An_Array := (1, others => 0)
10019 set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
10020 set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
10021 set A_Record := (1, "Peter", True);
10022 set A_Record := (Name => "Peter", Id => 1, Alive => True)
10026 discriminant's value by assigning an aggregate has an
10027 undefined effect if that discriminant is used within the record.
10028 However, you can first modify discriminants by directly assigning to
10029 them (which normally would not be allowed in Ada), and then performing an
10030 aggregate assignment. For example, given a variable @code{A_Rec}
10031 declared to have a type such as:
10034 type Rec (Len : Small_Integer := 0) is record
10036 Vals : IntArray (1 .. Len);
10040 you can assign a value with a different size of @code{Vals} with two
10045 set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
10048 As this example also illustrates, @value{GDBN} is very loose about the usual
10049 rules concerning aggregates. You may leave out some of the
10050 components of an array or record aggregate (such as the @code{Len}
10051 component in the assignment to @code{A_Rec} above); they will retain their
10052 original values upon assignment. You may freely use dynamic values as
10053 indices in component associations. You may even use overlapping or
10054 redundant component associations, although which component values are
10055 assigned in such cases is not defined.
10058 Calls to dispatching subprograms are not implemented.
10061 The overloading algorithm is much more limited (i.e., less selective)
10062 than that of real Ada. It makes only limited use of the context in which a subexpression
10063 appears to resolve its meaning, and it is much looser in its rules for allowing
10064 type matches. As a result, some function calls will be ambiguous, and the user
10065 will be asked to choose the proper resolution.
10068 The @code{new} operator is not implemented.
10071 Entry calls are not implemented.
10074 Aside from printing, arithmetic operations on the native VAX floating-point
10075 formats are not supported.
10078 It is not possible to slice a packed array.
10081 @node Additions to Ada
10082 @subsubsection Additions to Ada
10083 @cindex Ada, deviations from
10085 As it does for other languages, @value{GDBN} makes certain generic
10086 extensions to Ada (@pxref{Expressions}):
10090 If the expression @var{E} is a variable residing in memory
10091 (typically a local variable or array element) and @var{N} is
10092 a positive integer, then @code{@var{E}@@@var{N}} displays the values of
10093 @var{E} and the @var{N}-1 adjacent variables following it in memory as an array.
10094 In Ada, this operator is generally not necessary, since its prime use
10095 is in displaying parts of an array, and slicing will usually do this in Ada.
10096 However, there are occasional uses when debugging programs
10097 in which certain debugging information has been optimized away.
10100 @code{@var{B}::@var{var}} means ``the variable named @var{var} that appears
10101 in function or file @var{B}.'' When @var{B} is a file name, you must typically
10102 surround it in single quotes.
10105 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
10106 @var{type} that appears at address @var{addr}.''
10109 A name starting with @samp{$} is a convenience variable
10110 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
10113 In addition, @value{GDBN} provides a few other shortcuts and outright additions specific
10118 The assignment statement is allowed as an expression, returning
10119 its right-hand operand as its value. Thus, you may enter
10123 print A(tmp := y + 1)
10127 The semicolon is allowed as an ``operator,'' returning as its value
10128 the value of its right-hand operand.
10129 This allows, for example,
10130 complex conditional breaks:
10134 condition 1 (report(i); k += 1; A(k) > 100)
10138 Rather than use catenation and symbolic character names to introduce special
10139 characters into strings, one may instead use a special bracket notation,
10140 which is also used to print strings. A sequence of characters of the form
10141 @samp{["@var{XX}"]} within a string or character literal denotes the
10142 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
10143 sequence of characters @samp{["""]} also denotes a single quotation mark
10144 in strings. For example,
10146 "One line.["0a"]Next line.["0a"]"
10149 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF}) after each
10153 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
10154 @t{'Max} is optional (and is ignored in any case). For example, it is valid
10162 When printing arrays, @value{GDBN} uses positional notation when the
10163 array has a lower bound of 1, and uses a modified named notation otherwise.
10164 For example, a one-dimensional array of three integers with a lower bound of 3 might print as
10171 That is, in contrast to valid Ada, only the first component has a @code{=>}
10175 You may abbreviate attributes in expressions with any unique,
10176 multi-character subsequence of
10177 their names (an exact match gets preference).
10178 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
10179 in place of @t{a'length}.
10182 @cindex quoting Ada internal identifiers
10183 Since Ada is case-insensitive, the debugger normally maps identifiers you type
10184 to lower case. The GNAT compiler uses upper-case characters for
10185 some of its internal identifiers, which are normally of no interest to users.
10186 For the rare occasions when you actually have to look at them,
10187 enclose them in angle brackets to avoid the lower-case mapping.
10190 @value{GDBP} print <JMPBUF_SAVE>[0]
10194 Printing an object of class-wide type or dereferencing an
10195 access-to-class-wide value will display all the components of the object's
10196 specific type (as indicated by its run-time tag). Likewise, component
10197 selection on such a value will operate on the specific type of the
10202 @node Stopping Before Main Program
10203 @subsubsection Stopping at the Very Beginning
10205 @cindex breakpointing Ada elaboration code
10206 It is sometimes necessary to debug the program during elaboration, and
10207 before reaching the main procedure.
10208 As defined in the Ada Reference
10209 Manual, the elaboration code is invoked from a procedure called
10210 @code{adainit}. To run your program up to the beginning of
10211 elaboration, simply use the following two commands:
10212 @code{tbreak adainit} and @code{run}.
10215 @subsubsection Known Peculiarities of Ada Mode
10216 @cindex Ada, problems
10218 Besides the omissions listed previously (@pxref{Omissions from Ada}),
10219 we know of several problems with and limitations of Ada mode in
10221 some of which will be fixed with planned future releases of the debugger
10222 and the GNU Ada compiler.
10226 Currently, the debugger
10227 has insufficient information to determine whether certain pointers represent
10228 pointers to objects or the objects themselves.
10229 Thus, the user may have to tack an extra @code{.all} after an expression
10230 to get it printed properly.
10233 Static constants that the compiler chooses not to materialize as objects in
10234 storage are invisible to the debugger.
10237 Named parameter associations in function argument lists are ignored (the
10238 argument lists are treated as positional).
10241 Many useful library packages are currently invisible to the debugger.
10244 Fixed-point arithmetic, conversions, input, and output is carried out using
10245 floating-point arithmetic, and may give results that only approximate those on
10249 The type of the @t{'Address} attribute may not be @code{System.Address}.
10252 The GNAT compiler never generates the prefix @code{Standard} for any of
10253 the standard symbols defined by the Ada language. @value{GDBN} knows about
10254 this: it will strip the prefix from names when you use it, and will never
10255 look for a name you have so qualified among local symbols, nor match against
10256 symbols in other packages or subprograms. If you have
10257 defined entities anywhere in your program other than parameters and
10258 local variables whose simple names match names in @code{Standard},
10259 GNAT's lack of qualification here can cause confusion. When this happens,
10260 you can usually resolve the confusion
10261 by qualifying the problematic names with package
10262 @code{Standard} explicitly.
10265 @node Unsupported languages
10266 @section Unsupported languages
10268 @cindex unsupported languages
10269 @cindex minimal language
10270 In addition to the other fully-supported programming languages,
10271 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
10272 It does not represent a real programming language, but provides a set
10273 of capabilities close to what the C or assembly languages provide.
10274 This should allow most simple operations to be performed while debugging
10275 an application that uses a language currently not supported by @value{GDBN}.
10277 If the language is set to @code{auto}, @value{GDBN} will automatically
10278 select this language if the current frame corresponds to an unsupported
10282 @chapter Examining the Symbol Table
10284 The commands described in this chapter allow you to inquire about the
10285 symbols (names of variables, functions and types) defined in your
10286 program. This information is inherent in the text of your program and
10287 does not change as your program executes. @value{GDBN} finds it in your
10288 program's symbol table, in the file indicated when you started @value{GDBN}
10289 (@pxref{File Options, ,Choosing files}), or by one of the
10290 file-management commands (@pxref{Files, ,Commands to specify files}).
10292 @cindex symbol names
10293 @cindex names of symbols
10294 @cindex quoting names
10295 Occasionally, you may need to refer to symbols that contain unusual
10296 characters, which @value{GDBN} ordinarily treats as word delimiters. The
10297 most frequent case is in referring to static variables in other
10298 source files (@pxref{Variables,,Program variables}). File names
10299 are recorded in object files as debugging symbols, but @value{GDBN} would
10300 ordinarily parse a typical file name, like @file{foo.c}, as the three words
10301 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
10302 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
10309 looks up the value of @code{x} in the scope of the file @file{foo.c}.
10312 @cindex case-insensitive symbol names
10313 @cindex case sensitivity in symbol names
10314 @kindex set case-sensitive
10315 @item set case-sensitive on
10316 @itemx set case-sensitive off
10317 @itemx set case-sensitive auto
10318 Normally, when @value{GDBN} looks up symbols, it matches their names
10319 with case sensitivity determined by the current source language.
10320 Occasionally, you may wish to control that. The command @code{set
10321 case-sensitive} lets you do that by specifying @code{on} for
10322 case-sensitive matches or @code{off} for case-insensitive ones. If
10323 you specify @code{auto}, case sensitivity is reset to the default
10324 suitable for the source language. The default is case-sensitive
10325 matches for all languages except for Fortran, for which the default is
10326 case-insensitive matches.
10328 @kindex show case-sensitive
10329 @item show case-sensitive
10330 This command shows the current setting of case sensitivity for symbols
10333 @kindex info address
10334 @cindex address of a symbol
10335 @item info address @var{symbol}
10336 Describe where the data for @var{symbol} is stored. For a register
10337 variable, this says which register it is kept in. For a non-register
10338 local variable, this prints the stack-frame offset at which the variable
10341 Note the contrast with @samp{print &@var{symbol}}, which does not work
10342 at all for a register variable, and for a stack local variable prints
10343 the exact address of the current instantiation of the variable.
10345 @kindex info symbol
10346 @cindex symbol from address
10347 @cindex closest symbol and offset for an address
10348 @item info symbol @var{addr}
10349 Print the name of a symbol which is stored at the address @var{addr}.
10350 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
10351 nearest symbol and an offset from it:
10354 (@value{GDBP}) info symbol 0x54320
10355 _initialize_vx + 396 in section .text
10359 This is the opposite of the @code{info address} command. You can use
10360 it to find out the name of a variable or a function given its address.
10363 @item whatis @var{expr}
10364 Print the data type of expression @var{expr}. @var{expr} is not
10365 actually evaluated, and any side-effecting operations (such as
10366 assignments or function calls) inside it do not take place.
10367 @xref{Expressions, ,Expressions}.
10370 Print the data type of @code{$}, the last value in the value history.
10373 @item ptype @var{typename}
10374 Print a description of data type @var{typename}. @var{typename} may be
10375 the name of a type, or for C code it may have the form @samp{class
10376 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
10377 @var{union-tag}} or @samp{enum @var{enum-tag}}.
10379 @item ptype @var{expr}
10381 Print a description of the type of expression @var{expr}. @code{ptype}
10382 differs from @code{whatis} by printing a detailed description, instead
10383 of just the name of the type.
10385 For example, for this variable declaration:
10388 struct complex @{double real; double imag;@} v;
10392 the two commands give this output:
10396 (@value{GDBP}) whatis v
10397 type = struct complex
10398 (@value{GDBP}) ptype v
10399 type = struct complex @{
10407 As with @code{whatis}, using @code{ptype} without an argument refers to
10408 the type of @code{$}, the last value in the value history.
10410 @cindex incomplete type
10411 Sometimes, programs use opaque data types or incomplete specifications
10412 of complex data structure. If the debug information included in the
10413 program does not allow @value{GDBN} to display a full declaration of
10414 the data type, it will say @samp{<incomplete type>}. For example,
10415 given these declarations:
10419 struct foo *fooptr;
10423 but no definition for @code{struct foo} itself, @value{GDBN} will say:
10427 $1 = <incomplete type>
10431 ``Incomplete type'' is C terminology for data types that are not
10432 completely specified.
10435 @item info types @var{regexp}
10437 Print a brief description of all types whose names match the regular
10438 expression @var{regexp} (or all types in your program, if you supply
10439 no argument). Each complete typename is matched as though it were a
10440 complete line; thus, @samp{i type value} gives information on all
10441 types in your program whose names include the string @code{value}, but
10442 @samp{i type ^value$} gives information only on types whose complete
10443 name is @code{value}.
10445 This command differs from @code{ptype} in two ways: first, like
10446 @code{whatis}, it does not print a detailed description; second, it
10447 lists all source files where a type is defined.
10450 @cindex local variables
10451 @item info scope @var{location}
10452 List all the variables local to a particular scope. This command
10453 accepts a @var{location} argument---a function name, a source line, or
10454 an address preceded by a @samp{*}, and prints all the variables local
10455 to the scope defined by that location. For example:
10458 (@value{GDBP}) @b{info scope command_line_handler}
10459 Scope for command_line_handler:
10460 Symbol rl is an argument at stack/frame offset 8, length 4.
10461 Symbol linebuffer is in static storage at address 0x150a18, length 4.
10462 Symbol linelength is in static storage at address 0x150a1c, length 4.
10463 Symbol p is a local variable in register $esi, length 4.
10464 Symbol p1 is a local variable in register $ebx, length 4.
10465 Symbol nline is a local variable in register $edx, length 4.
10466 Symbol repeat is a local variable at frame offset -8, length 4.
10470 This command is especially useful for determining what data to collect
10471 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
10474 @kindex info source
10476 Show information about the current source file---that is, the source file for
10477 the function containing the current point of execution:
10480 the name of the source file, and the directory containing it,
10482 the directory it was compiled in,
10484 its length, in lines,
10486 which programming language it is written in,
10488 whether the executable includes debugging information for that file, and
10489 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
10491 whether the debugging information includes information about
10492 preprocessor macros.
10496 @kindex info sources
10498 Print the names of all source files in your program for which there is
10499 debugging information, organized into two lists: files whose symbols
10500 have already been read, and files whose symbols will be read when needed.
10502 @kindex info functions
10503 @item info functions
10504 Print the names and data types of all defined functions.
10506 @item info functions @var{regexp}
10507 Print the names and data types of all defined functions
10508 whose names contain a match for regular expression @var{regexp}.
10509 Thus, @samp{info fun step} finds all functions whose names
10510 include @code{step}; @samp{info fun ^step} finds those whose names
10511 start with @code{step}. If a function name contains characters
10512 that conflict with the regular expression language (e.g.@:
10513 @samp{operator*()}), they may be quoted with a backslash.
10515 @kindex info variables
10516 @item info variables
10517 Print the names and data types of all variables that are declared
10518 outside of functions (i.e.@: excluding local variables).
10520 @item info variables @var{regexp}
10521 Print the names and data types of all variables (except for local
10522 variables) whose names contain a match for regular expression
10525 @kindex info classes
10526 @cindex Objective-C, classes and selectors
10528 @itemx info classes @var{regexp}
10529 Display all Objective-C classes in your program, or
10530 (with the @var{regexp} argument) all those matching a particular regular
10533 @kindex info selectors
10534 @item info selectors
10535 @itemx info selectors @var{regexp}
10536 Display all Objective-C selectors in your program, or
10537 (with the @var{regexp} argument) all those matching a particular regular
10541 This was never implemented.
10542 @kindex info methods
10544 @itemx info methods @var{regexp}
10545 The @code{info methods} command permits the user to examine all defined
10546 methods within C@t{++} program, or (with the @var{regexp} argument) a
10547 specific set of methods found in the various C@t{++} classes. Many
10548 C@t{++} classes provide a large number of methods. Thus, the output
10549 from the @code{ptype} command can be overwhelming and hard to use. The
10550 @code{info-methods} command filters the methods, printing only those
10551 which match the regular-expression @var{regexp}.
10554 @cindex reloading symbols
10555 Some systems allow individual object files that make up your program to
10556 be replaced without stopping and restarting your program. For example,
10557 in VxWorks you can simply recompile a defective object file and keep on
10558 running. If you are running on one of these systems, you can allow
10559 @value{GDBN} to reload the symbols for automatically relinked modules:
10562 @kindex set symbol-reloading
10563 @item set symbol-reloading on
10564 Replace symbol definitions for the corresponding source file when an
10565 object file with a particular name is seen again.
10567 @item set symbol-reloading off
10568 Do not replace symbol definitions when encountering object files of the
10569 same name more than once. This is the default state; if you are not
10570 running on a system that permits automatic relinking of modules, you
10571 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
10572 may discard symbols when linking large programs, that may contain
10573 several modules (from different directories or libraries) with the same
10576 @kindex show symbol-reloading
10577 @item show symbol-reloading
10578 Show the current @code{on} or @code{off} setting.
10581 @cindex opaque data types
10582 @kindex set opaque-type-resolution
10583 @item set opaque-type-resolution on
10584 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
10585 declared as a pointer to a @code{struct}, @code{class}, or
10586 @code{union}---for example, @code{struct MyType *}---that is used in one
10587 source file although the full declaration of @code{struct MyType} is in
10588 another source file. The default is on.
10590 A change in the setting of this subcommand will not take effect until
10591 the next time symbols for a file are loaded.
10593 @item set opaque-type-resolution off
10594 Tell @value{GDBN} not to resolve opaque types. In this case, the type
10595 is printed as follows:
10597 @{<no data fields>@}
10600 @kindex show opaque-type-resolution
10601 @item show opaque-type-resolution
10602 Show whether opaque types are resolved or not.
10604 @kindex maint print symbols
10605 @cindex symbol dump
10606 @kindex maint print psymbols
10607 @cindex partial symbol dump
10608 @item maint print symbols @var{filename}
10609 @itemx maint print psymbols @var{filename}
10610 @itemx maint print msymbols @var{filename}
10611 Write a dump of debugging symbol data into the file @var{filename}.
10612 These commands are used to debug the @value{GDBN} symbol-reading code. Only
10613 symbols with debugging data are included. If you use @samp{maint print
10614 symbols}, @value{GDBN} includes all the symbols for which it has already
10615 collected full details: that is, @var{filename} reflects symbols for
10616 only those files whose symbols @value{GDBN} has read. You can use the
10617 command @code{info sources} to find out which files these are. If you
10618 use @samp{maint print psymbols} instead, the dump shows information about
10619 symbols that @value{GDBN} only knows partially---that is, symbols defined in
10620 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
10621 @samp{maint print msymbols} dumps just the minimal symbol information
10622 required for each object file from which @value{GDBN} has read some symbols.
10623 @xref{Files, ,Commands to specify files}, for a discussion of how
10624 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
10626 @kindex maint info symtabs
10627 @kindex maint info psymtabs
10628 @cindex listing @value{GDBN}'s internal symbol tables
10629 @cindex symbol tables, listing @value{GDBN}'s internal
10630 @cindex full symbol tables, listing @value{GDBN}'s internal
10631 @cindex partial symbol tables, listing @value{GDBN}'s internal
10632 @item maint info symtabs @r{[} @var{regexp} @r{]}
10633 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
10635 List the @code{struct symtab} or @code{struct partial_symtab}
10636 structures whose names match @var{regexp}. If @var{regexp} is not
10637 given, list them all. The output includes expressions which you can
10638 copy into a @value{GDBN} debugging this one to examine a particular
10639 structure in more detail. For example:
10642 (@value{GDBP}) maint info psymtabs dwarf2read
10643 @{ objfile /home/gnu/build/gdb/gdb
10644 ((struct objfile *) 0x82e69d0)
10645 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
10646 ((struct partial_symtab *) 0x8474b10)
10649 text addresses 0x814d3c8 -- 0x8158074
10650 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
10651 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
10652 dependencies (none)
10655 (@value{GDBP}) maint info symtabs
10659 We see that there is one partial symbol table whose filename contains
10660 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
10661 and we see that @value{GDBN} has not read in any symtabs yet at all.
10662 If we set a breakpoint on a function, that will cause @value{GDBN} to
10663 read the symtab for the compilation unit containing that function:
10666 (@value{GDBP}) break dwarf2_psymtab_to_symtab
10667 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
10669 (@value{GDBP}) maint info symtabs
10670 @{ objfile /home/gnu/build/gdb/gdb
10671 ((struct objfile *) 0x82e69d0)
10672 @{ symtab /home/gnu/src/gdb/dwarf2read.c
10673 ((struct symtab *) 0x86c1f38)
10676 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
10677 debugformat DWARF 2
10686 @chapter Altering Execution
10688 Once you think you have found an error in your program, you might want to
10689 find out for certain whether correcting the apparent error would lead to
10690 correct results in the rest of the run. You can find the answer by
10691 experiment, using the @value{GDBN} features for altering execution of the
10694 For example, you can store new values into variables or memory
10695 locations, give your program a signal, restart it at a different
10696 address, or even return prematurely from a function.
10699 * Assignment:: Assignment to variables
10700 * Jumping:: Continuing at a different address
10701 * Signaling:: Giving your program a signal
10702 * Returning:: Returning from a function
10703 * Calling:: Calling your program's functions
10704 * Patching:: Patching your program
10708 @section Assignment to variables
10711 @cindex setting variables
10712 To alter the value of a variable, evaluate an assignment expression.
10713 @xref{Expressions, ,Expressions}. For example,
10720 stores the value 4 into the variable @code{x}, and then prints the
10721 value of the assignment expression (which is 4).
10722 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
10723 information on operators in supported languages.
10725 @kindex set variable
10726 @cindex variables, setting
10727 If you are not interested in seeing the value of the assignment, use the
10728 @code{set} command instead of the @code{print} command. @code{set} is
10729 really the same as @code{print} except that the expression's value is
10730 not printed and is not put in the value history (@pxref{Value History,
10731 ,Value history}). The expression is evaluated only for its effects.
10733 If the beginning of the argument string of the @code{set} command
10734 appears identical to a @code{set} subcommand, use the @code{set
10735 variable} command instead of just @code{set}. This command is identical
10736 to @code{set} except for its lack of subcommands. For example, if your
10737 program has a variable @code{width}, you get an error if you try to set
10738 a new value with just @samp{set width=13}, because @value{GDBN} has the
10739 command @code{set width}:
10742 (@value{GDBP}) whatis width
10744 (@value{GDBP}) p width
10746 (@value{GDBP}) set width=47
10747 Invalid syntax in expression.
10751 The invalid expression, of course, is @samp{=47}. In
10752 order to actually set the program's variable @code{width}, use
10755 (@value{GDBP}) set var width=47
10758 Because the @code{set} command has many subcommands that can conflict
10759 with the names of program variables, it is a good idea to use the
10760 @code{set variable} command instead of just @code{set}. For example, if
10761 your program has a variable @code{g}, you run into problems if you try
10762 to set a new value with just @samp{set g=4}, because @value{GDBN} has
10763 the command @code{set gnutarget}, abbreviated @code{set g}:
10767 (@value{GDBP}) whatis g
10771 (@value{GDBP}) set g=4
10775 The program being debugged has been started already.
10776 Start it from the beginning? (y or n) y
10777 Starting program: /home/smith/cc_progs/a.out
10778 "/home/smith/cc_progs/a.out": can't open to read symbols:
10779 Invalid bfd target.
10780 (@value{GDBP}) show g
10781 The current BFD target is "=4".
10786 The program variable @code{g} did not change, and you silently set the
10787 @code{gnutarget} to an invalid value. In order to set the variable
10791 (@value{GDBP}) set var g=4
10794 @value{GDBN} allows more implicit conversions in assignments than C; you can
10795 freely store an integer value into a pointer variable or vice versa,
10796 and you can convert any structure to any other structure that is the
10797 same length or shorter.
10798 @comment FIXME: how do structs align/pad in these conversions?
10799 @comment /doc@cygnus.com 18dec1990
10801 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
10802 construct to generate a value of specified type at a specified address
10803 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
10804 to memory location @code{0x83040} as an integer (which implies a certain size
10805 and representation in memory), and
10808 set @{int@}0x83040 = 4
10812 stores the value 4 into that memory location.
10815 @section Continuing at a different address
10817 Ordinarily, when you continue your program, you do so at the place where
10818 it stopped, with the @code{continue} command. You can instead continue at
10819 an address of your own choosing, with the following commands:
10823 @item jump @var{linespec}
10824 Resume execution at line @var{linespec}. Execution stops again
10825 immediately if there is a breakpoint there. @xref{List, ,Printing
10826 source lines}, for a description of the different forms of
10827 @var{linespec}. It is common practice to use the @code{tbreak} command
10828 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
10831 The @code{jump} command does not change the current stack frame, or
10832 the stack pointer, or the contents of any memory location or any
10833 register other than the program counter. If line @var{linespec} is in
10834 a different function from the one currently executing, the results may
10835 be bizarre if the two functions expect different patterns of arguments or
10836 of local variables. For this reason, the @code{jump} command requests
10837 confirmation if the specified line is not in the function currently
10838 executing. However, even bizarre results are predictable if you are
10839 well acquainted with the machine-language code of your program.
10841 @item jump *@var{address}
10842 Resume execution at the instruction at address @var{address}.
10845 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
10846 On many systems, you can get much the same effect as the @code{jump}
10847 command by storing a new value into the register @code{$pc}. The
10848 difference is that this does not start your program running; it only
10849 changes the address of where it @emph{will} run when you continue. For
10857 makes the next @code{continue} command or stepping command execute at
10858 address @code{0x485}, rather than at the address where your program stopped.
10859 @xref{Continuing and Stepping, ,Continuing and stepping}.
10861 The most common occasion to use the @code{jump} command is to back
10862 up---perhaps with more breakpoints set---over a portion of a program
10863 that has already executed, in order to examine its execution in more
10868 @section Giving your program a signal
10869 @cindex deliver a signal to a program
10873 @item signal @var{signal}
10874 Resume execution where your program stopped, but immediately give it the
10875 signal @var{signal}. @var{signal} can be the name or the number of a
10876 signal. For example, on many systems @code{signal 2} and @code{signal
10877 SIGINT} are both ways of sending an interrupt signal.
10879 Alternatively, if @var{signal} is zero, continue execution without
10880 giving a signal. This is useful when your program stopped on account of
10881 a signal and would ordinary see the signal when resumed with the
10882 @code{continue} command; @samp{signal 0} causes it to resume without a
10885 @code{signal} does not repeat when you press @key{RET} a second time
10886 after executing the command.
10890 Invoking the @code{signal} command is not the same as invoking the
10891 @code{kill} utility from the shell. Sending a signal with @code{kill}
10892 causes @value{GDBN} to decide what to do with the signal depending on
10893 the signal handling tables (@pxref{Signals}). The @code{signal} command
10894 passes the signal directly to your program.
10898 @section Returning from a function
10901 @cindex returning from a function
10904 @itemx return @var{expression}
10905 You can cancel execution of a function call with the @code{return}
10906 command. If you give an
10907 @var{expression} argument, its value is used as the function's return
10911 When you use @code{return}, @value{GDBN} discards the selected stack frame
10912 (and all frames within it). You can think of this as making the
10913 discarded frame return prematurely. If you wish to specify a value to
10914 be returned, give that value as the argument to @code{return}.
10916 This pops the selected stack frame (@pxref{Selection, ,Selecting a
10917 frame}), and any other frames inside of it, leaving its caller as the
10918 innermost remaining frame. That frame becomes selected. The
10919 specified value is stored in the registers used for returning values
10922 The @code{return} command does not resume execution; it leaves the
10923 program stopped in the state that would exist if the function had just
10924 returned. In contrast, the @code{finish} command (@pxref{Continuing
10925 and Stepping, ,Continuing and stepping}) resumes execution until the
10926 selected stack frame returns naturally.
10929 @section Calling program functions
10932 @cindex calling functions
10933 @cindex inferior functions, calling
10934 @item print @var{expr}
10935 Evaluate the expression @var{expr} and display the resuling value.
10936 @var{expr} may include calls to functions in the program being
10940 @item call @var{expr}
10941 Evaluate the expression @var{expr} without displaying @code{void}
10944 You can use this variant of the @code{print} command if you want to
10945 execute a function from your program that does not return anything
10946 (a.k.a.@: @dfn{a void function}), but without cluttering the output
10947 with @code{void} returned values that @value{GDBN} will otherwise
10948 print. If the result is not void, it is printed and saved in the
10952 It is possible for the function you call via the @code{print} or
10953 @code{call} command to generate a signal (e.g., if there's a bug in
10954 the function, or if you passed it incorrect arguments). What happens
10955 in that case is controlled by the @code{set unwindonsignal} command.
10958 @item set unwindonsignal
10959 @kindex set unwindonsignal
10960 @cindex unwind stack in called functions
10961 @cindex call dummy stack unwinding
10962 Set unwinding of the stack if a signal is received while in a function
10963 that @value{GDBN} called in the program being debugged. If set to on,
10964 @value{GDBN} unwinds the stack it created for the call and restores
10965 the context to what it was before the call. If set to off (the
10966 default), @value{GDBN} stops in the frame where the signal was
10969 @item show unwindonsignal
10970 @kindex show unwindonsignal
10971 Show the current setting of stack unwinding in the functions called by
10975 @cindex weak alias functions
10976 Sometimes, a function you wish to call is actually a @dfn{weak alias}
10977 for another function. In such case, @value{GDBN} might not pick up
10978 the type information, including the types of the function arguments,
10979 which causes @value{GDBN} to call the inferior function incorrectly.
10980 As a result, the called function will function erroneously and may
10981 even crash. A solution to that is to use the name of the aliased
10985 @section Patching programs
10987 @cindex patching binaries
10988 @cindex writing into executables
10989 @cindex writing into corefiles
10991 By default, @value{GDBN} opens the file containing your program's
10992 executable code (or the corefile) read-only. This prevents accidental
10993 alterations to machine code; but it also prevents you from intentionally
10994 patching your program's binary.
10996 If you'd like to be able to patch the binary, you can specify that
10997 explicitly with the @code{set write} command. For example, you might
10998 want to turn on internal debugging flags, or even to make emergency
11004 @itemx set write off
11005 If you specify @samp{set write on}, @value{GDBN} opens executable and
11006 core files for both reading and writing; if you specify @samp{set write
11007 off} (the default), @value{GDBN} opens them read-only.
11009 If you have already loaded a file, you must load it again (using the
11010 @code{exec-file} or @code{core-file} command) after changing @code{set
11011 write}, for your new setting to take effect.
11015 Display whether executable files and core files are opened for writing
11016 as well as reading.
11020 @chapter @value{GDBN} Files
11022 @value{GDBN} needs to know the file name of the program to be debugged,
11023 both in order to read its symbol table and in order to start your
11024 program. To debug a core dump of a previous run, you must also tell
11025 @value{GDBN} the name of the core dump file.
11028 * Files:: Commands to specify files
11029 * Separate Debug Files:: Debugging information in separate files
11030 * Symbol Errors:: Errors reading symbol files
11034 @section Commands to specify files
11036 @cindex symbol table
11037 @cindex core dump file
11039 You may want to specify executable and core dump file names. The usual
11040 way to do this is at start-up time, using the arguments to
11041 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
11042 Out of @value{GDBN}}).
11044 Occasionally it is necessary to change to a different file during a
11045 @value{GDBN} session. Or you may run @value{GDBN} and forget to
11046 specify a file you want to use. Or you are debugging a remote target
11047 via @code{gdbserver} (@pxref{Server, file}). In these situations the
11048 @value{GDBN} commands to specify new files are useful.
11051 @cindex executable file
11053 @item file @var{filename}
11054 Use @var{filename} as the program to be debugged. It is read for its
11055 symbols and for the contents of pure memory. It is also the program
11056 executed when you use the @code{run} command. If you do not specify a
11057 directory and the file is not found in the @value{GDBN} working directory,
11058 @value{GDBN} uses the environment variable @code{PATH} as a list of
11059 directories to search, just as the shell does when looking for a program
11060 to run. You can change the value of this variable, for both @value{GDBN}
11061 and your program, using the @code{path} command.
11063 @cindex unlinked object files
11064 @cindex patching object files
11065 You can load unlinked object @file{.o} files into @value{GDBN} using
11066 the @code{file} command. You will not be able to ``run'' an object
11067 file, but you can disassemble functions and inspect variables. Also,
11068 if the underlying BFD functionality supports it, you could use
11069 @kbd{gdb -write} to patch object files using this technique. Note
11070 that @value{GDBN} can neither interpret nor modify relocations in this
11071 case, so branches and some initialized variables will appear to go to
11072 the wrong place. But this feature is still handy from time to time.
11075 @code{file} with no argument makes @value{GDBN} discard any information it
11076 has on both executable file and the symbol table.
11079 @item exec-file @r{[} @var{filename} @r{]}
11080 Specify that the program to be run (but not the symbol table) is found
11081 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
11082 if necessary to locate your program. Omitting @var{filename} means to
11083 discard information on the executable file.
11085 @kindex symbol-file
11086 @item symbol-file @r{[} @var{filename} @r{]}
11087 Read symbol table information from file @var{filename}. @code{PATH} is
11088 searched when necessary. Use the @code{file} command to get both symbol
11089 table and program to run from the same file.
11091 @code{symbol-file} with no argument clears out @value{GDBN} information on your
11092 program's symbol table.
11094 The @code{symbol-file} command causes @value{GDBN} to forget the contents
11095 of its convenience variables, the value history, and all breakpoints and
11096 auto-display expressions. This is because they may contain pointers to
11097 the internal data recording symbols and data types, which are part of
11098 the old symbol table data being discarded inside @value{GDBN}.
11100 @code{symbol-file} does not repeat if you press @key{RET} again after
11103 When @value{GDBN} is configured for a particular environment, it
11104 understands debugging information in whatever format is the standard
11105 generated for that environment; you may use either a @sc{gnu} compiler, or
11106 other compilers that adhere to the local conventions.
11107 Best results are usually obtained from @sc{gnu} compilers; for example,
11108 using @code{@value{GCC}} you can generate debugging information for
11111 For most kinds of object files, with the exception of old SVR3 systems
11112 using COFF, the @code{symbol-file} command does not normally read the
11113 symbol table in full right away. Instead, it scans the symbol table
11114 quickly to find which source files and which symbols are present. The
11115 details are read later, one source file at a time, as they are needed.
11117 The purpose of this two-stage reading strategy is to make @value{GDBN}
11118 start up faster. For the most part, it is invisible except for
11119 occasional pauses while the symbol table details for a particular source
11120 file are being read. (The @code{set verbose} command can turn these
11121 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
11122 warnings and messages}.)
11124 We have not implemented the two-stage strategy for COFF yet. When the
11125 symbol table is stored in COFF format, @code{symbol-file} reads the
11126 symbol table data in full right away. Note that ``stabs-in-COFF''
11127 still does the two-stage strategy, since the debug info is actually
11131 @cindex reading symbols immediately
11132 @cindex symbols, reading immediately
11133 @item symbol-file @var{filename} @r{[} -readnow @r{]}
11134 @itemx file @var{filename} @r{[} -readnow @r{]}
11135 You can override the @value{GDBN} two-stage strategy for reading symbol
11136 tables by using the @samp{-readnow} option with any of the commands that
11137 load symbol table information, if you want to be sure @value{GDBN} has the
11138 entire symbol table available.
11140 @c FIXME: for now no mention of directories, since this seems to be in
11141 @c flux. 13mar1992 status is that in theory GDB would look either in
11142 @c current dir or in same dir as myprog; but issues like competing
11143 @c GDB's, or clutter in system dirs, mean that in practice right now
11144 @c only current dir is used. FFish says maybe a special GDB hierarchy
11145 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
11149 @item core-file @r{[}@var{filename}@r{]}
11151 Specify the whereabouts of a core dump file to be used as the ``contents
11152 of memory''. Traditionally, core files contain only some parts of the
11153 address space of the process that generated them; @value{GDBN} can access the
11154 executable file itself for other parts.
11156 @code{core-file} with no argument specifies that no core file is
11159 Note that the core file is ignored when your program is actually running
11160 under @value{GDBN}. So, if you have been running your program and you
11161 wish to debug a core file instead, you must kill the subprocess in which
11162 the program is running. To do this, use the @code{kill} command
11163 (@pxref{Kill Process, ,Killing the child process}).
11165 @kindex add-symbol-file
11166 @cindex dynamic linking
11167 @item add-symbol-file @var{filename} @var{address}
11168 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
11169 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
11170 The @code{add-symbol-file} command reads additional symbol table
11171 information from the file @var{filename}. You would use this command
11172 when @var{filename} has been dynamically loaded (by some other means)
11173 into the program that is running. @var{address} should be the memory
11174 address at which the file has been loaded; @value{GDBN} cannot figure
11175 this out for itself. You can additionally specify an arbitrary number
11176 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
11177 section name and base address for that section. You can specify any
11178 @var{address} as an expression.
11180 The symbol table of the file @var{filename} is added to the symbol table
11181 originally read with the @code{symbol-file} command. You can use the
11182 @code{add-symbol-file} command any number of times; the new symbol data
11183 thus read keeps adding to the old. To discard all old symbol data
11184 instead, use the @code{symbol-file} command without any arguments.
11186 @cindex relocatable object files, reading symbols from
11187 @cindex object files, relocatable, reading symbols from
11188 @cindex reading symbols from relocatable object files
11189 @cindex symbols, reading from relocatable object files
11190 @cindex @file{.o} files, reading symbols from
11191 Although @var{filename} is typically a shared library file, an
11192 executable file, or some other object file which has been fully
11193 relocated for loading into a process, you can also load symbolic
11194 information from relocatable @file{.o} files, as long as:
11198 the file's symbolic information refers only to linker symbols defined in
11199 that file, not to symbols defined by other object files,
11201 every section the file's symbolic information refers to has actually
11202 been loaded into the inferior, as it appears in the file, and
11204 you can determine the address at which every section was loaded, and
11205 provide these to the @code{add-symbol-file} command.
11209 Some embedded operating systems, like Sun Chorus and VxWorks, can load
11210 relocatable files into an already running program; such systems
11211 typically make the requirements above easy to meet. However, it's
11212 important to recognize that many native systems use complex link
11213 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
11214 assembly, for example) that make the requirements difficult to meet. In
11215 general, one cannot assume that using @code{add-symbol-file} to read a
11216 relocatable object file's symbolic information will have the same effect
11217 as linking the relocatable object file into the program in the normal
11220 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
11222 @kindex add-symbol-file-from-memory
11223 @cindex @code{syscall DSO}
11224 @cindex load symbols from memory
11225 @item add-symbol-file-from-memory @var{address}
11226 Load symbols from the given @var{address} in a dynamically loaded
11227 object file whose image is mapped directly into the inferior's memory.
11228 For example, the Linux kernel maps a @code{syscall DSO} into each
11229 process's address space; this DSO provides kernel-specific code for
11230 some system calls. The argument can be any expression whose
11231 evaluation yields the address of the file's shared object file header.
11232 For this command to work, you must have used @code{symbol-file} or
11233 @code{exec-file} commands in advance.
11235 @kindex add-shared-symbol-files
11237 @item add-shared-symbol-files @var{library-file}
11238 @itemx assf @var{library-file}
11239 The @code{add-shared-symbol-files} command can currently be used only
11240 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
11241 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
11242 @value{GDBN} automatically looks for shared libraries, however if
11243 @value{GDBN} does not find yours, you can invoke
11244 @code{add-shared-symbol-files}. It takes one argument: the shared
11245 library's file name. @code{assf} is a shorthand alias for
11246 @code{add-shared-symbol-files}.
11249 @item section @var{section} @var{addr}
11250 The @code{section} command changes the base address of the named
11251 @var{section} of the exec file to @var{addr}. This can be used if the
11252 exec file does not contain section addresses, (such as in the
11253 @code{a.out} format), or when the addresses specified in the file
11254 itself are wrong. Each section must be changed separately. The
11255 @code{info files} command, described below, lists all the sections and
11259 @kindex info target
11262 @code{info files} and @code{info target} are synonymous; both print the
11263 current target (@pxref{Targets, ,Specifying a Debugging Target}),
11264 including the names of the executable and core dump files currently in
11265 use by @value{GDBN}, and the files from which symbols were loaded. The
11266 command @code{help target} lists all possible targets rather than
11269 @kindex maint info sections
11270 @item maint info sections
11271 Another command that can give you extra information about program sections
11272 is @code{maint info sections}. In addition to the section information
11273 displayed by @code{info files}, this command displays the flags and file
11274 offset of each section in the executable and core dump files. In addition,
11275 @code{maint info sections} provides the following command options (which
11276 may be arbitrarily combined):
11280 Display sections for all loaded object files, including shared libraries.
11281 @item @var{sections}
11282 Display info only for named @var{sections}.
11283 @item @var{section-flags}
11284 Display info only for sections for which @var{section-flags} are true.
11285 The section flags that @value{GDBN} currently knows about are:
11288 Section will have space allocated in the process when loaded.
11289 Set for all sections except those containing debug information.
11291 Section will be loaded from the file into the child process memory.
11292 Set for pre-initialized code and data, clear for @code{.bss} sections.
11294 Section needs to be relocated before loading.
11296 Section cannot be modified by the child process.
11298 Section contains executable code only.
11300 Section contains data only (no executable code).
11302 Section will reside in ROM.
11304 Section contains data for constructor/destructor lists.
11306 Section is not empty.
11308 An instruction to the linker to not output the section.
11309 @item COFF_SHARED_LIBRARY
11310 A notification to the linker that the section contains
11311 COFF shared library information.
11313 Section contains common symbols.
11316 @kindex set trust-readonly-sections
11317 @cindex read-only sections
11318 @item set trust-readonly-sections on
11319 Tell @value{GDBN} that readonly sections in your object file
11320 really are read-only (i.e.@: that their contents will not change).
11321 In that case, @value{GDBN} can fetch values from these sections
11322 out of the object file, rather than from the target program.
11323 For some targets (notably embedded ones), this can be a significant
11324 enhancement to debugging performance.
11326 The default is off.
11328 @item set trust-readonly-sections off
11329 Tell @value{GDBN} not to trust readonly sections. This means that
11330 the contents of the section might change while the program is running,
11331 and must therefore be fetched from the target when needed.
11333 @item show trust-readonly-sections
11334 Show the current setting of trusting readonly sections.
11337 All file-specifying commands allow both absolute and relative file names
11338 as arguments. @value{GDBN} always converts the file name to an absolute file
11339 name and remembers it that way.
11341 @cindex shared libraries
11342 @value{GDBN} supports GNU/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
11343 and IBM RS/6000 AIX shared libraries.
11345 @value{GDBN} automatically loads symbol definitions from shared libraries
11346 when you use the @code{run} command, or when you examine a core file.
11347 (Before you issue the @code{run} command, @value{GDBN} does not understand
11348 references to a function in a shared library, however---unless you are
11349 debugging a core file).
11351 On HP-UX, if the program loads a library explicitly, @value{GDBN}
11352 automatically loads the symbols at the time of the @code{shl_load} call.
11354 @c FIXME: some @value{GDBN} release may permit some refs to undef
11355 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
11356 @c FIXME...lib; check this from time to time when updating manual
11358 There are times, however, when you may wish to not automatically load
11359 symbol definitions from shared libraries, such as when they are
11360 particularly large or there are many of them.
11362 To control the automatic loading of shared library symbols, use the
11366 @kindex set auto-solib-add
11367 @item set auto-solib-add @var{mode}
11368 If @var{mode} is @code{on}, symbols from all shared object libraries
11369 will be loaded automatically when the inferior begins execution, you
11370 attach to an independently started inferior, or when the dynamic linker
11371 informs @value{GDBN} that a new library has been loaded. If @var{mode}
11372 is @code{off}, symbols must be loaded manually, using the
11373 @code{sharedlibrary} command. The default value is @code{on}.
11375 @cindex memory used for symbol tables
11376 If your program uses lots of shared libraries with debug info that
11377 takes large amounts of memory, you can decrease the @value{GDBN}
11378 memory footprint by preventing it from automatically loading the
11379 symbols from shared libraries. To that end, type @kbd{set
11380 auto-solib-add off} before running the inferior, then load each
11381 library whose debug symbols you do need with @kbd{sharedlibrary
11382 @var{regexp}}, where @var{regexp} is a regular expresion that matches
11383 the libraries whose symbols you want to be loaded.
11385 @kindex show auto-solib-add
11386 @item show auto-solib-add
11387 Display the current autoloading mode.
11390 @cindex load shared library
11391 To explicitly load shared library symbols, use the @code{sharedlibrary}
11395 @kindex info sharedlibrary
11398 @itemx info sharedlibrary
11399 Print the names of the shared libraries which are currently loaded.
11401 @kindex sharedlibrary
11403 @item sharedlibrary @var{regex}
11404 @itemx share @var{regex}
11405 Load shared object library symbols for files matching a
11406 Unix regular expression.
11407 As with files loaded automatically, it only loads shared libraries
11408 required by your program for a core file or after typing @code{run}. If
11409 @var{regex} is omitted all shared libraries required by your program are
11412 @item nosharedlibrary
11413 @kindex nosharedlibrary
11414 @cindex unload symbols from shared libraries
11415 Unload all shared object library symbols. This discards all symbols
11416 that have been loaded from all shared libraries. Symbols from shared
11417 libraries that were loaded by explicit user requests are not
11421 Sometimes you may wish that @value{GDBN} stops and gives you control
11422 when any of shared library events happen. Use the @code{set
11423 stop-on-solib-events} command for this:
11426 @item set stop-on-solib-events
11427 @kindex set stop-on-solib-events
11428 This command controls whether @value{GDBN} should give you control
11429 when the dynamic linker notifies it about some shared library event.
11430 The most common event of interest is loading or unloading of a new
11433 @item show stop-on-solib-events
11434 @kindex show stop-on-solib-events
11435 Show whether @value{GDBN} stops and gives you control when shared
11436 library events happen.
11439 Shared libraries are also supported in many cross or remote debugging
11440 configurations. A copy of the target's libraries need to be present on the
11441 host system; they need to be the same as the target libraries, although the
11442 copies on the target can be stripped as long as the copies on the host are
11445 @cindex where to look for shared libraries
11446 For remote debugging, you need to tell @value{GDBN} where the target
11447 libraries are, so that it can load the correct copies---otherwise, it
11448 may try to load the host's libraries. @value{GDBN} has two variables
11449 to specify the search directories for target libraries.
11452 @cindex prefix for shared library file names
11453 @kindex set solib-absolute-prefix
11454 @item set solib-absolute-prefix @var{path}
11455 If this variable is set, @var{path} will be used as a prefix for any
11456 absolute shared library paths; many runtime loaders store the absolute
11457 paths to the shared library in the target program's memory. If you use
11458 @samp{solib-absolute-prefix} to find shared libraries, they need to be laid
11459 out in the same way that they are on the target, with e.g.@: a
11460 @file{/usr/lib} hierarchy under @var{path}.
11462 @cindex default value of @samp{solib-absolute-prefix}
11463 @cindex @samp{--with-sysroot}
11464 You can set the default value of @samp{solib-absolute-prefix} by using the
11465 configure-time @samp{--with-sysroot} option.
11467 @kindex show solib-absolute-prefix
11468 @item show solib-absolute-prefix
11469 Display the current shared library prefix.
11471 @kindex set solib-search-path
11472 @item set solib-search-path @var{path}
11473 If this variable is set, @var{path} is a colon-separated list of directories
11474 to search for shared libraries. @samp{solib-search-path} is used after
11475 @samp{solib-absolute-prefix} fails to locate the library, or if the path to
11476 the library is relative instead of absolute. If you want to use
11477 @samp{solib-search-path} instead of @samp{solib-absolute-prefix}, be sure to
11478 set @samp{solib-absolute-prefix} to a nonexistant directory to prevent
11479 @value{GDBN} from finding your host's libraries.
11481 @kindex show solib-search-path
11482 @item show solib-search-path
11483 Display the current shared library search path.
11487 @node Separate Debug Files
11488 @section Debugging Information in Separate Files
11489 @cindex separate debugging information files
11490 @cindex debugging information in separate files
11491 @cindex @file{.debug} subdirectories
11492 @cindex debugging information directory, global
11493 @cindex global debugging information directory
11495 @value{GDBN} allows you to put a program's debugging information in a
11496 file separate from the executable itself, in a way that allows
11497 @value{GDBN} to find and load the debugging information automatically.
11498 Since debugging information can be very large --- sometimes larger
11499 than the executable code itself --- some systems distribute debugging
11500 information for their executables in separate files, which users can
11501 install only when they need to debug a problem.
11503 If an executable's debugging information has been extracted to a
11504 separate file, the executable should contain a @dfn{debug link} giving
11505 the name of the debugging information file (with no directory
11506 components), and a checksum of its contents. (The exact form of a
11507 debug link is described below.) If the full name of the directory
11508 containing the executable is @var{execdir}, and the executable has a
11509 debug link that specifies the name @var{debugfile}, then @value{GDBN}
11510 will automatically search for the debugging information file in three
11515 the directory containing the executable file (that is, it will look
11516 for a file named @file{@var{execdir}/@var{debugfile}},
11518 a subdirectory of that directory named @file{.debug} (that is, the
11519 file @file{@var{execdir}/.debug/@var{debugfile}}, and
11521 a subdirectory of the global debug file directory that includes the
11522 executable's full path, and the name from the link (that is, the file
11523 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
11524 @var{globaldebugdir} is the global debug file directory, and
11525 @var{execdir} has been turned into a relative path).
11528 @value{GDBN} checks under each of these names for a debugging
11529 information file whose checksum matches that given in the link, and
11530 reads the debugging information from the first one it finds.
11532 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
11533 which has a link containing the name @file{ls.debug}, and the global
11534 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
11535 for debug information in @file{/usr/bin/ls.debug},
11536 @file{/usr/bin/.debug/ls.debug}, and
11537 @file{/usr/lib/debug/usr/bin/ls.debug}.
11539 You can set the global debugging info directory's name, and view the
11540 name @value{GDBN} is currently using.
11544 @kindex set debug-file-directory
11545 @item set debug-file-directory @var{directory}
11546 Set the directory which @value{GDBN} searches for separate debugging
11547 information files to @var{directory}.
11549 @kindex show debug-file-directory
11550 @item show debug-file-directory
11551 Show the directory @value{GDBN} searches for separate debugging
11556 @cindex @code{.gnu_debuglink} sections
11557 @cindex debug links
11558 A debug link is a special section of the executable file named
11559 @code{.gnu_debuglink}. The section must contain:
11563 A filename, with any leading directory components removed, followed by
11566 zero to three bytes of padding, as needed to reach the next four-byte
11567 boundary within the section, and
11569 a four-byte CRC checksum, stored in the same endianness used for the
11570 executable file itself. The checksum is computed on the debugging
11571 information file's full contents by the function given below, passing
11572 zero as the @var{crc} argument.
11575 Any executable file format can carry a debug link, as long as it can
11576 contain a section named @code{.gnu_debuglink} with the contents
11579 The debugging information file itself should be an ordinary
11580 executable, containing a full set of linker symbols, sections, and
11581 debugging information. The sections of the debugging information file
11582 should have the same names, addresses and sizes as the original file,
11583 but they need not contain any data --- much like a @code{.bss} section
11584 in an ordinary executable.
11586 As of December 2002, there is no standard GNU utility to produce
11587 separated executable / debugging information file pairs. Ulrich
11588 Drepper's @file{elfutils} package, starting with version 0.53,
11589 contains a version of the @code{strip} command such that the command
11590 @kbd{strip foo -f foo.debug} removes the debugging information from
11591 the executable file @file{foo}, places it in the file
11592 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
11594 Since there are many different ways to compute CRC's (different
11595 polynomials, reversals, byte ordering, etc.), the simplest way to
11596 describe the CRC used in @code{.gnu_debuglink} sections is to give the
11597 complete code for a function that computes it:
11599 @kindex gnu_debuglink_crc32
11602 gnu_debuglink_crc32 (unsigned long crc,
11603 unsigned char *buf, size_t len)
11605 static const unsigned long crc32_table[256] =
11607 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
11608 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
11609 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
11610 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
11611 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
11612 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
11613 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
11614 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
11615 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
11616 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
11617 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
11618 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
11619 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
11620 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
11621 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
11622 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
11623 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
11624 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
11625 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
11626 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
11627 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
11628 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
11629 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
11630 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
11631 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
11632 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
11633 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
11634 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
11635 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
11636 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
11637 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
11638 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
11639 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
11640 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
11641 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
11642 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
11643 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
11644 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
11645 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
11646 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
11647 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
11648 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
11649 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
11650 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
11651 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
11652 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
11653 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
11654 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
11655 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
11656 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
11657 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
11660 unsigned char *end;
11662 crc = ~crc & 0xffffffff;
11663 for (end = buf + len; buf < end; ++buf)
11664 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
11665 return ~crc & 0xffffffff;
11670 @node Symbol Errors
11671 @section Errors reading symbol files
11673 While reading a symbol file, @value{GDBN} occasionally encounters problems,
11674 such as symbol types it does not recognize, or known bugs in compiler
11675 output. By default, @value{GDBN} does not notify you of such problems, since
11676 they are relatively common and primarily of interest to people
11677 debugging compilers. If you are interested in seeing information
11678 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
11679 only one message about each such type of problem, no matter how many
11680 times the problem occurs; or you can ask @value{GDBN} to print more messages,
11681 to see how many times the problems occur, with the @code{set
11682 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
11685 The messages currently printed, and their meanings, include:
11688 @item inner block not inside outer block in @var{symbol}
11690 The symbol information shows where symbol scopes begin and end
11691 (such as at the start of a function or a block of statements). This
11692 error indicates that an inner scope block is not fully contained
11693 in its outer scope blocks.
11695 @value{GDBN} circumvents the problem by treating the inner block as if it had
11696 the same scope as the outer block. In the error message, @var{symbol}
11697 may be shown as ``@code{(don't know)}'' if the outer block is not a
11700 @item block at @var{address} out of order
11702 The symbol information for symbol scope blocks should occur in
11703 order of increasing addresses. This error indicates that it does not
11706 @value{GDBN} does not circumvent this problem, and has trouble
11707 locating symbols in the source file whose symbols it is reading. (You
11708 can often determine what source file is affected by specifying
11709 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
11712 @item bad block start address patched
11714 The symbol information for a symbol scope block has a start address
11715 smaller than the address of the preceding source line. This is known
11716 to occur in the SunOS 4.1.1 (and earlier) C compiler.
11718 @value{GDBN} circumvents the problem by treating the symbol scope block as
11719 starting on the previous source line.
11721 @item bad string table offset in symbol @var{n}
11724 Symbol number @var{n} contains a pointer into the string table which is
11725 larger than the size of the string table.
11727 @value{GDBN} circumvents the problem by considering the symbol to have the
11728 name @code{foo}, which may cause other problems if many symbols end up
11731 @item unknown symbol type @code{0x@var{nn}}
11733 The symbol information contains new data types that @value{GDBN} does
11734 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
11735 uncomprehended information, in hexadecimal.
11737 @value{GDBN} circumvents the error by ignoring this symbol information.
11738 This usually allows you to debug your program, though certain symbols
11739 are not accessible. If you encounter such a problem and feel like
11740 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
11741 on @code{complain}, then go up to the function @code{read_dbx_symtab}
11742 and examine @code{*bufp} to see the symbol.
11744 @item stub type has NULL name
11746 @value{GDBN} could not find the full definition for a struct or class.
11748 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
11749 The symbol information for a C@t{++} member function is missing some
11750 information that recent versions of the compiler should have output for
11753 @item info mismatch between compiler and debugger
11755 @value{GDBN} could not parse a type specification output by the compiler.
11760 @chapter Specifying a Debugging Target
11762 @cindex debugging target
11763 A @dfn{target} is the execution environment occupied by your program.
11765 Often, @value{GDBN} runs in the same host environment as your program;
11766 in that case, the debugging target is specified as a side effect when
11767 you use the @code{file} or @code{core} commands. When you need more
11768 flexibility---for example, running @value{GDBN} on a physically separate
11769 host, or controlling a standalone system over a serial port or a
11770 realtime system over a TCP/IP connection---you can use the @code{target}
11771 command to specify one of the target types configured for @value{GDBN}
11772 (@pxref{Target Commands, ,Commands for managing targets}).
11774 @cindex target architecture
11775 It is possible to build @value{GDBN} for several different @dfn{target
11776 architectures}. When @value{GDBN} is built like that, you can choose
11777 one of the available architectures with the @kbd{set architecture}
11781 @kindex set architecture
11782 @kindex show architecture
11783 @item set architecture @var{arch}
11784 This command sets the current target architecture to @var{arch}. The
11785 value of @var{arch} can be @code{"auto"}, in addition to one of the
11786 supported architectures.
11788 @item show architecture
11789 Show the current target architecture.
11791 @item set processor
11793 @kindex set processor
11794 @kindex show processor
11795 These are alias commands for, respectively, @code{set architecture}
11796 and @code{show architecture}.
11800 * Active Targets:: Active targets
11801 * Target Commands:: Commands for managing targets
11802 * Byte Order:: Choosing target byte order
11803 * Remote:: Remote debugging
11804 * KOD:: Kernel Object Display
11808 @node Active Targets
11809 @section Active targets
11811 @cindex stacking targets
11812 @cindex active targets
11813 @cindex multiple targets
11815 There are three classes of targets: processes, core files, and
11816 executable files. @value{GDBN} can work concurrently on up to three
11817 active targets, one in each class. This allows you to (for example)
11818 start a process and inspect its activity without abandoning your work on
11821 For example, if you execute @samp{gdb a.out}, then the executable file
11822 @code{a.out} is the only active target. If you designate a core file as
11823 well---presumably from a prior run that crashed and coredumped---then
11824 @value{GDBN} has two active targets and uses them in tandem, looking
11825 first in the corefile target, then in the executable file, to satisfy
11826 requests for memory addresses. (Typically, these two classes of target
11827 are complementary, since core files contain only a program's
11828 read-write memory---variables and so on---plus machine status, while
11829 executable files contain only the program text and initialized data.)
11831 When you type @code{run}, your executable file becomes an active process
11832 target as well. When a process target is active, all @value{GDBN}
11833 commands requesting memory addresses refer to that target; addresses in
11834 an active core file or executable file target are obscured while the
11835 process target is active.
11837 Use the @code{core-file} and @code{exec-file} commands to select a new
11838 core file or executable target (@pxref{Files, ,Commands to specify
11839 files}). To specify as a target a process that is already running, use
11840 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
11843 @node Target Commands
11844 @section Commands for managing targets
11847 @item target @var{type} @var{parameters}
11848 Connects the @value{GDBN} host environment to a target machine or
11849 process. A target is typically a protocol for talking to debugging
11850 facilities. You use the argument @var{type} to specify the type or
11851 protocol of the target machine.
11853 Further @var{parameters} are interpreted by the target protocol, but
11854 typically include things like device names or host names to connect
11855 with, process numbers, and baud rates.
11857 The @code{target} command does not repeat if you press @key{RET} again
11858 after executing the command.
11860 @kindex help target
11862 Displays the names of all targets available. To display targets
11863 currently selected, use either @code{info target} or @code{info files}
11864 (@pxref{Files, ,Commands to specify files}).
11866 @item help target @var{name}
11867 Describe a particular target, including any parameters necessary to
11870 @kindex set gnutarget
11871 @item set gnutarget @var{args}
11872 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
11873 knows whether it is reading an @dfn{executable},
11874 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
11875 with the @code{set gnutarget} command. Unlike most @code{target} commands,
11876 with @code{gnutarget} the @code{target} refers to a program, not a machine.
11879 @emph{Warning:} To specify a file format with @code{set gnutarget},
11880 you must know the actual BFD name.
11884 @xref{Files, , Commands to specify files}.
11886 @kindex show gnutarget
11887 @item show gnutarget
11888 Use the @code{show gnutarget} command to display what file format
11889 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
11890 @value{GDBN} will determine the file format for each file automatically,
11891 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
11894 @cindex common targets
11895 Here are some common targets (available, or not, depending on the GDB
11900 @item target exec @var{program}
11901 @cindex executable file target
11902 An executable file. @samp{target exec @var{program}} is the same as
11903 @samp{exec-file @var{program}}.
11905 @item target core @var{filename}
11906 @cindex core dump file target
11907 A core dump file. @samp{target core @var{filename}} is the same as
11908 @samp{core-file @var{filename}}.
11910 @item target remote @var{dev}
11911 @cindex remote target
11912 Remote serial target in GDB-specific protocol. The argument @var{dev}
11913 specifies what serial device to use for the connection (e.g.@:
11914 @file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote}
11915 supports the @code{load} command. This is only useful if you have
11916 some other way of getting the stub to the target system, and you can put
11917 it somewhere in memory where it won't get clobbered by the download.
11920 @cindex built-in simulator target
11921 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
11929 works; however, you cannot assume that a specific memory map, device
11930 drivers, or even basic I/O is available, although some simulators do
11931 provide these. For info about any processor-specific simulator details,
11932 see the appropriate section in @ref{Embedded Processors, ,Embedded
11937 Some configurations may include these targets as well:
11941 @item target nrom @var{dev}
11942 @cindex NetROM ROM emulator target
11943 NetROM ROM emulator. This target only supports downloading.
11947 Different targets are available on different configurations of @value{GDBN};
11948 your configuration may have more or fewer targets.
11950 Many remote targets require you to download the executable's code once
11951 you've successfully established a connection. You may wish to control
11952 various aspects of this process, such as the size of the data chunks
11953 used by @value{GDBN} to download program parts to the remote target.
11956 @kindex set download-write-size
11957 @item set download-write-size @var{size}
11958 Set the write size used when downloading a program. Only used when
11959 downloading a program onto a remote target. Specify zero or a
11960 negative value to disable blocked writes. The actual size of each
11961 transfer is also limited by the size of the target packet and the
11964 @kindex show download-write-size
11965 @item show download-write-size
11966 @kindex show download-write-size
11967 Show the current value of the write size.
11970 @kindex set hash@r{, for remote monitors}
11971 @cindex hash mark while downloading
11972 This command controls whether a hash mark @samp{#} is displayed while
11973 downloading a file to the remote monitor. If on, a hash mark is
11974 displayed after each S-record is successfully downloaded to the
11978 @kindex show hash@r{, for remote monitors}
11979 Show the current status of displaying the hash mark.
11981 @item set debug monitor
11982 @kindex set debug monitor
11983 @cindex display remote monitor communications
11984 Enable or disable display of communications messages between
11985 @value{GDBN} and the remote monitor.
11987 @item show debug monitor
11988 @kindex show debug monitor
11989 Show the current status of displaying communications between
11990 @value{GDBN} and the remote monitor.
11995 @kindex load @var{filename}
11996 @item load @var{filename}
11997 Depending on what remote debugging facilities are configured into
11998 @value{GDBN}, the @code{load} command may be available. Where it exists, it
11999 is meant to make @var{filename} (an executable) available for debugging
12000 on the remote system---by downloading, or dynamic linking, for example.
12001 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
12002 the @code{add-symbol-file} command.
12004 If your @value{GDBN} does not have a @code{load} command, attempting to
12005 execute it gets the error message ``@code{You can't do that when your
12006 target is @dots{}}''
12008 The file is loaded at whatever address is specified in the executable.
12009 For some object file formats, you can specify the load address when you
12010 link the program; for other formats, like a.out, the object file format
12011 specifies a fixed address.
12012 @c FIXME! This would be a good place for an xref to the GNU linker doc.
12014 @code{load} does not repeat if you press @key{RET} again after using it.
12018 @section Choosing target byte order
12020 @cindex choosing target byte order
12021 @cindex target byte order
12023 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
12024 offer the ability to run either big-endian or little-endian byte
12025 orders. Usually the executable or symbol will include a bit to
12026 designate the endian-ness, and you will not need to worry about
12027 which to use. However, you may still find it useful to adjust
12028 @value{GDBN}'s idea of processor endian-ness manually.
12032 @item set endian big
12033 Instruct @value{GDBN} to assume the target is big-endian.
12035 @item set endian little
12036 Instruct @value{GDBN} to assume the target is little-endian.
12038 @item set endian auto
12039 Instruct @value{GDBN} to use the byte order associated with the
12043 Display @value{GDBN}'s current idea of the target byte order.
12047 Note that these commands merely adjust interpretation of symbolic
12048 data on the host, and that they have absolutely no effect on the
12052 @section Remote debugging
12053 @cindex remote debugging
12055 If you are trying to debug a program running on a machine that cannot run
12056 @value{GDBN} in the usual way, it is often useful to use remote debugging.
12057 For example, you might use remote debugging on an operating system kernel,
12058 or on a small system which does not have a general purpose operating system
12059 powerful enough to run a full-featured debugger.
12061 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
12062 to make this work with particular debugging targets. In addition,
12063 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
12064 but not specific to any particular target system) which you can use if you
12065 write the remote stubs---the code that runs on the remote system to
12066 communicate with @value{GDBN}.
12068 Other remote targets may be available in your
12069 configuration of @value{GDBN}; use @code{help target} to list them.
12071 Once you've connected to the remote target, @value{GDBN} allows you to
12072 send arbitrary commands to the remote monitor:
12075 @item remote @var{command}
12076 @kindex remote@r{, a command}
12077 @cindex send command to remote monitor
12078 Send an arbitrary @var{command} string to the remote monitor.
12083 @section Kernel Object Display
12084 @cindex kernel object display
12087 Some targets support kernel object display. Using this facility,
12088 @value{GDBN} communicates specially with the underlying operating system
12089 and can display information about operating system-level objects such as
12090 mutexes and other synchronization objects. Exactly which objects can be
12091 displayed is determined on a per-OS basis.
12094 Use the @code{set os} command to set the operating system. This tells
12095 @value{GDBN} which kernel object display module to initialize:
12098 (@value{GDBP}) set os cisco
12102 The associated command @code{show os} displays the operating system
12103 set with the @code{set os} command; if no operating system has been
12104 set, @code{show os} will display an empty string @samp{""}.
12106 If @code{set os} succeeds, @value{GDBN} will display some information
12107 about the operating system, and will create a new @code{info} command
12108 which can be used to query the target. The @code{info} command is named
12109 after the operating system:
12113 (@value{GDBP}) info cisco
12114 List of Cisco Kernel Objects
12116 any Any and all objects
12119 Further subcommands can be used to query about particular objects known
12122 There is currently no way to determine whether a given operating
12123 system is supported other than to try setting it with @kbd{set os
12124 @var{name}}, where @var{name} is the name of the operating system you
12128 @node Remote Debugging
12129 @chapter Debugging remote programs
12132 * Connecting:: Connecting to a remote target
12133 * Server:: Using the gdbserver program
12134 * NetWare:: Using the gdbserve.nlm program
12135 * Remote configuration:: Remote configuration
12136 * remote stub:: Implementing a remote stub
12140 @section Connecting to a remote target
12142 On the @value{GDBN} host machine, you will need an unstripped copy of
12143 your program, since @value{GDBN} needs symobl and debugging information.
12144 Start up @value{GDBN} as usual, using the name of the local copy of your
12145 program as the first argument.
12147 @cindex serial line, @code{target remote}
12148 If you're using a serial line, you may want to give @value{GDBN} the
12149 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
12150 (@pxref{Remote configuration, set remotebaud}) before the
12151 @code{target} command.
12153 After that, use @code{target remote} to establish communications with
12154 the target machine. Its argument specifies how to communicate---either
12155 via a devicename attached to a direct serial line, or a TCP or UDP port
12156 (possibly to a terminal server which in turn has a serial line to the
12157 target). For example, to use a serial line connected to the device
12158 named @file{/dev/ttyb}:
12161 target remote /dev/ttyb
12164 @cindex TCP port, @code{target remote}
12165 To use a TCP connection, use an argument of the form
12166 @code{@var{host}:@var{port}} or @code{tcp:@var{host}:@var{port}}.
12167 For example, to connect to port 2828 on a
12168 terminal server named @code{manyfarms}:
12171 target remote manyfarms:2828
12174 If your remote target is actually running on the same machine as
12175 your debugger session (e.g.@: a simulator of your target running on
12176 the same host), you can omit the hostname. For example, to connect
12177 to port 1234 on your local machine:
12180 target remote :1234
12184 Note that the colon is still required here.
12186 @cindex UDP port, @code{target remote}
12187 To use a UDP connection, use an argument of the form
12188 @code{udp:@var{host}:@var{port}}. For example, to connect to UDP port 2828
12189 on a terminal server named @code{manyfarms}:
12192 target remote udp:manyfarms:2828
12195 When using a UDP connection for remote debugging, you should keep in mind
12196 that the `U' stands for ``Unreliable''. UDP can silently drop packets on
12197 busy or unreliable networks, which will cause havoc with your debugging
12200 Now you can use all the usual commands to examine and change data and to
12201 step and continue the remote program.
12203 @cindex interrupting remote programs
12204 @cindex remote programs, interrupting
12205 Whenever @value{GDBN} is waiting for the remote program, if you type the
12206 interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
12207 program. This may or may not succeed, depending in part on the hardware
12208 and the serial drivers the remote system uses. If you type the
12209 interrupt character once again, @value{GDBN} displays this prompt:
12212 Interrupted while waiting for the program.
12213 Give up (and stop debugging it)? (y or n)
12216 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
12217 (If you decide you want to try again later, you can use @samp{target
12218 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
12219 goes back to waiting.
12222 @kindex detach (remote)
12224 When you have finished debugging the remote program, you can use the
12225 @code{detach} command to release it from @value{GDBN} control.
12226 Detaching from the target normally resumes its execution, but the results
12227 will depend on your particular remote stub. After the @code{detach}
12228 command, @value{GDBN} is free to connect to another target.
12232 The @code{disconnect} command behaves like @code{detach}, except that
12233 the target is generally not resumed. It will wait for @value{GDBN}
12234 (this instance or another one) to connect and continue debugging. After
12235 the @code{disconnect} command, @value{GDBN} is again free to connect to
12238 @cindex send command to remote monitor
12239 @cindex extend @value{GDBN} for remote targets
12240 @cindex add new commands for external monitor
12242 @item monitor @var{cmd}
12243 This command allows you to send arbitrary commands directly to the
12244 remote monitor. Since @value{GDBN} doesn't care about the commands it
12245 sends like this, this command is the way to extend @value{GDBN}---you
12246 can add new commands that only the external monitor will understand
12251 @section Using the @code{gdbserver} program
12254 @cindex remote connection without stubs
12255 @code{gdbserver} is a control program for Unix-like systems, which
12256 allows you to connect your program with a remote @value{GDBN} via
12257 @code{target remote}---but without linking in the usual debugging stub.
12259 @code{gdbserver} is not a complete replacement for the debugging stubs,
12260 because it requires essentially the same operating-system facilities
12261 that @value{GDBN} itself does. In fact, a system that can run
12262 @code{gdbserver} to connect to a remote @value{GDBN} could also run
12263 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
12264 because it is a much smaller program than @value{GDBN} itself. It is
12265 also easier to port than all of @value{GDBN}, so you may be able to get
12266 started more quickly on a new system by using @code{gdbserver}.
12267 Finally, if you develop code for real-time systems, you may find that
12268 the tradeoffs involved in real-time operation make it more convenient to
12269 do as much development work as possible on another system, for example
12270 by cross-compiling. You can use @code{gdbserver} to make a similar
12271 choice for debugging.
12273 @value{GDBN} and @code{gdbserver} communicate via either a serial line
12274 or a TCP connection, using the standard @value{GDBN} remote serial
12278 @item On the target machine,
12279 you need to have a copy of the program you want to debug.
12280 @code{gdbserver} does not need your program's symbol table, so you can
12281 strip the program if necessary to save space. @value{GDBN} on the host
12282 system does all the symbol handling.
12284 To use the server, you must tell it how to communicate with @value{GDBN};
12285 the name of your program; and the arguments for your program. The usual
12289 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
12292 @var{comm} is either a device name (to use a serial line) or a TCP
12293 hostname and portnumber. For example, to debug Emacs with the argument
12294 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
12298 target> gdbserver /dev/com1 emacs foo.txt
12301 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
12304 To use a TCP connection instead of a serial line:
12307 target> gdbserver host:2345 emacs foo.txt
12310 The only difference from the previous example is the first argument,
12311 specifying that you are communicating with the host @value{GDBN} via
12312 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
12313 expect a TCP connection from machine @samp{host} to local TCP port 2345.
12314 (Currently, the @samp{host} part is ignored.) You can choose any number
12315 you want for the port number as long as it does not conflict with any
12316 TCP ports already in use on the target system (for example, @code{23} is
12317 reserved for @code{telnet}).@footnote{If you choose a port number that
12318 conflicts with another service, @code{gdbserver} prints an error message
12319 and exits.} You must use the same port number with the host @value{GDBN}
12320 @code{target remote} command.
12322 On some targets, @code{gdbserver} can also attach to running programs.
12323 This is accomplished via the @code{--attach} argument. The syntax is:
12326 target> gdbserver @var{comm} --attach @var{pid}
12329 @var{pid} is the process ID of a currently running process. It isn't necessary
12330 to point @code{gdbserver} at a binary for the running process.
12333 @cindex attach to a program by name
12334 You can debug processes by name instead of process ID if your target has the
12335 @code{pidof} utility:
12338 target> gdbserver @var{comm} --attach `pidof @var{PROGRAM}`
12341 In case more than one copy of @var{PROGRAM} is running, or @var{PROGRAM}
12342 has multiple threads, most versions of @code{pidof} support the
12343 @code{-s} option to only return the first process ID.
12345 @item On the host machine,
12346 connect to your target (@pxref{Connecting,,Connecting to a remote target}).
12347 For TCP connections, you must start up @code{gdbserver} prior to using
12348 the @code{target remote} command. Otherwise you may get an error whose
12349 text depends on the host system, but which usually looks something like
12350 @samp{Connection refused}. You don't need to use the @code{load}
12351 command in @value{GDBN} when using @code{gdbserver}, since the program is
12352 already on the target. However, if you want to load the symbols (as
12353 you normally would), do that with the @code{file} command, and issue
12354 it @emph{before} connecting to the server; otherwise, you will get an
12355 error message saying @code{"Program is already running"}, since the
12356 program is considered running after the connection.
12361 @section Using the @code{gdbserve.nlm} program
12363 @kindex gdbserve.nlm
12364 @code{gdbserve.nlm} is a control program for NetWare systems, which
12365 allows you to connect your program with a remote @value{GDBN} via
12366 @code{target remote}.
12368 @value{GDBN} and @code{gdbserve.nlm} communicate via a serial line,
12369 using the standard @value{GDBN} remote serial protocol.
12372 @item On the target machine,
12373 you need to have a copy of the program you want to debug.
12374 @code{gdbserve.nlm} does not need your program's symbol table, so you
12375 can strip the program if necessary to save space. @value{GDBN} on the
12376 host system does all the symbol handling.
12378 To use the server, you must tell it how to communicate with
12379 @value{GDBN}; the name of your program; and the arguments for your
12380 program. The syntax is:
12383 load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ]
12384 [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ]
12387 @var{board} and @var{port} specify the serial line; @var{baud} specifies
12388 the baud rate used by the connection. @var{port} and @var{node} default
12389 to 0, @var{baud} defaults to 9600@dmn{bps}.
12391 For example, to debug Emacs with the argument @samp{foo.txt}and
12392 communicate with @value{GDBN} over serial port number 2 or board 1
12393 using a 19200@dmn{bps} connection:
12396 load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
12400 On the @value{GDBN} host machine, connect to your target (@pxref{Connecting,,
12401 Connecting to a remote target}).
12405 @node Remote configuration
12406 @section Remote configuration
12409 @kindex show remote
12410 This section documents the configuration options available when
12411 debugging remote programs. For the options related to the File I/O
12412 extensions of the remote protocol, see @ref{The system call,
12413 system-call-allowed}.
12416 @item set remoteaddresssize @var{bits}
12417 @cindex adress size for remote targets
12418 @cindex bits in remote address
12419 Set the maximum size of address in a memory packet to the specified
12420 number of bits. @value{GDBN} will mask off the address bits above
12421 that number, when it passes addresses to the remote target. The
12422 default value is the number of bits in the target's address.
12424 @item show remoteaddresssize
12425 Show the current value of remote address size in bits.
12427 @item set remotebaud @var{n}
12428 @cindex baud rate for remote targets
12429 Set the baud rate for the remote serial I/O to @var{n} baud. The
12430 value is used to set the speed of the serial port used for debugging
12433 @item show remotebaud
12434 Show the current speed of the remote connection.
12436 @item set remotebreak
12437 @cindex interrupt remote programs
12438 @cindex BREAK signal instead of Ctrl-C
12439 @anchor{set remotebreak}
12440 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
12441 when you press the @key{Ctrl-C} key to interrupt the program running
12442 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
12443 character instead. The default is off, since most remote systems
12444 expect to see @samp{Ctrl-C} as the interrupt signal.
12446 @item show remotebreak
12447 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
12448 interrupt the remote program.
12450 @item set remotedebug
12451 @cindex debug remote protocol
12452 @cindex remote protocol debugging
12453 @cindex display remote packets
12454 Control the debugging of the remote protocol. When enabled, each
12455 packet sent to or received from the remote target is displayed. The
12458 @item show remotedebug
12459 Show the current setting of the remote protocol debugging.
12461 @item set remotedevice @var{device}
12462 @cindex serial port name
12463 Set the name of the serial port through which to communicate to the
12464 remote target to @var{device}. This is the device used by
12465 @value{GDBN} to open the serial communications line to the remote
12466 target. There's no default, so you must set a valid port name for the
12467 remote serial communications to work. (Some varieties of the
12468 @code{target} command accept the port name as part of their
12471 @item show remotedevice
12472 Show the current name of the serial port.
12474 @item set remotelogbase @var{base}
12475 Set the base (a.k.a.@: radix) of logging serial protocol
12476 communications to @var{base}. Supported values of @var{base} are:
12477 @code{ascii}, @code{octal}, and @code{hex}. The default is
12480 @item show remotelogbase
12481 Show the current setting of the radix for logging remote serial
12484 @item set remotelogfile @var{file}
12485 @cindex record serial communications on file
12486 Record remote serial communications on the named @var{file}. The
12487 default is not to record at all.
12489 @item show remotelogfile.
12490 Show the current setting of the file name on which to record the
12491 serial communications.
12493 @item set remotetimeout @var{num}
12494 @cindex timeout for serial communications
12495 @cindex remote timeout
12496 Set the timeout limit to wait for the remote target to respond to
12497 @var{num} seconds. The default is 2 seconds.
12499 @item show remotetimeout
12500 Show the current number of seconds to wait for the remote target
12503 @cindex limit hardware breakpoints and watchpoints
12504 @cindex remote target, limit break- and watchpoints
12505 @anchor{set remote hardware-watchpoint-limit}
12506 @anchor{set remote hardware-breakpoint-limit}
12507 @item set remote hardware-watchpoint-limit @var{limit}
12508 @itemx set remote hardware-breakpoint-limit @var{limit}
12509 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
12510 watchpoints. A limit of -1, the default, is treated as unlimited.
12512 @item set remote fetch-register-packet
12513 @itemx set remote set-register-packet
12514 @itemx set remote P-packet
12515 @itemx set remote p-packet
12517 @cindex fetch registers from remote targets
12518 @cindex set registers in remote targets
12519 Determine whether @value{GDBN} can set and fetch registers from the
12520 remote target using the @samp{P} packets. The default depends on the
12521 remote stub's support of the @samp{P} packets (@value{GDBN} queries
12522 the stub when this packet is first required).
12524 @item show remote fetch-register-packet
12525 @itemx show remote set-register-packet
12526 @itemx show remote P-packet
12527 @itemx show remote p-packet
12528 Show the current setting of using the @samp{P} packets for setting and
12529 fetching registers from the remote target.
12531 @cindex binary downloads
12533 @item set remote binary-download-packet
12534 @itemx set remote X-packet
12535 Determine whether @value{GDBN} sends downloads in binary mode using
12536 the @samp{X} packets. The default is on.
12538 @item show remote binary-download-packet
12539 @itemx show remote X-packet
12540 Show the current setting of using the @samp{X} packets for binary
12543 @item set remote read-aux-vector-packet
12544 @cindex auxiliary vector of remote target
12545 @cindex @code{auxv}, and remote targets
12546 Set the use of the remote protocol's @samp{qPart:auxv:read} (target
12547 auxiliary vector read) request. This request is used to fetch the
12548 remote target's @dfn{auxiliary vector}, see @ref{OS Information,
12549 Auxiliary Vector}. The default setting depends on the remote stub's
12550 support of this request (@value{GDBN} queries the stub when this
12551 request is first required). @xref{General Query Packets, qPart}, for
12552 more information about this request.
12554 @item show remote read-aux-vector-packet
12555 Show the current setting of use of the @samp{qPart:auxv:read} request.
12557 @item set remote symbol-lookup-packet
12558 @cindex remote symbol lookup request
12559 Set the use of the remote protocol's @samp{qSymbol} (target symbol
12560 lookup) request. This request is used to communicate symbol
12561 information to the remote target, e.g., whenever a new shared library
12562 is loaded by the remote (@pxref{Files, shared libraries}). The
12563 default setting depends on the remote stub's support of this request
12564 (@value{GDBN} queries the stub when this request is first required).
12565 @xref{General Query Packets, qSymbol}, for more information about this
12568 @item show remote symbol-lookup-packet
12569 Show the current setting of use of the @samp{qSymbol} request.
12571 @item set remote verbose-resume-packet
12572 @cindex resume remote target
12573 @cindex signal thread, and remote targets
12574 @cindex single-step thread, and remote targets
12575 @cindex thread-specific operations on remote targets
12576 Set the use of the remote protocol's @samp{vCont} (descriptive resume)
12577 request. This request is used to resume specific threads in the
12578 remote target, and to single-step or signal them. The default setting
12579 depends on the remote stub's support of this request (@value{GDBN}
12580 queries the stub when this request is first required). This setting
12581 affects debugging of multithreaded programs: if @samp{vCont} cannot be
12582 used, @value{GDBN} might be unable to single-step a specific thread,
12583 especially under @code{set scheduler-locking off}; it is also
12584 impossible to pause a specific thread. @xref{Packets, vCont}, for
12587 @item show remote verbose-resume-packet
12588 Show the current setting of use of the @samp{vCont} request
12590 @item set remote software-breakpoint-packet
12591 @itemx set remote hardware-breakpoint-packet
12592 @itemx set remote write-watchpoint-packet
12593 @itemx set remote read-watchpoint-packet
12594 @itemx set remote access-watchpoint-packet
12595 @itemx set remote Z-packet
12597 @cindex remote hardware breakpoints and watchpoints
12598 These commands enable or disable the use of @samp{Z} packets for
12599 setting breakpoints and watchpoints in the remote target. The default
12600 depends on the remote stub's support of the @samp{Z} packets
12601 (@value{GDBN} queries the stub when each packet is first required).
12602 The command @code{set remote Z-packet}, kept for back-compatibility,
12603 turns on or off all the features that require the use of @samp{Z}
12606 @item show remote software-breakpoint-packet
12607 @itemx show remote hardware-breakpoint-packet
12608 @itemx show remote write-watchpoint-packet
12609 @itemx show remote read-watchpoint-packet
12610 @itemx show remote access-watchpoint-packet
12611 @itemx show remote Z-packet
12612 Show the current setting of @samp{Z} packets usage.
12614 @item set remote get-thread-local-storage-address
12615 @kindex set remote get-thread-local-storage-address
12616 @cindex thread local storage of remote targets
12617 This command enables or disables the use of the @samp{qGetTLSAddr}
12618 (Get Thread Local Storage Address) request packet. The default
12619 depends on whether the remote stub supports this request.
12620 @xref{General Query Packets, qGetTLSAddr}, for more details about this
12623 @item show remote get-thread-local-storage-address
12624 @kindex show remote get-thread-local-storage-address
12625 Show the current setting of @samp{qGetTLSAddr} packet usage.
12629 @section Implementing a remote stub
12631 @cindex debugging stub, example
12632 @cindex remote stub, example
12633 @cindex stub example, remote debugging
12634 The stub files provided with @value{GDBN} implement the target side of the
12635 communication protocol, and the @value{GDBN} side is implemented in the
12636 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
12637 these subroutines to communicate, and ignore the details. (If you're
12638 implementing your own stub file, you can still ignore the details: start
12639 with one of the existing stub files. @file{sparc-stub.c} is the best
12640 organized, and therefore the easiest to read.)
12642 @cindex remote serial debugging, overview
12643 To debug a program running on another machine (the debugging
12644 @dfn{target} machine), you must first arrange for all the usual
12645 prerequisites for the program to run by itself. For example, for a C
12650 A startup routine to set up the C runtime environment; these usually
12651 have a name like @file{crt0}. The startup routine may be supplied by
12652 your hardware supplier, or you may have to write your own.
12655 A C subroutine library to support your program's
12656 subroutine calls, notably managing input and output.
12659 A way of getting your program to the other machine---for example, a
12660 download program. These are often supplied by the hardware
12661 manufacturer, but you may have to write your own from hardware
12665 The next step is to arrange for your program to use a serial port to
12666 communicate with the machine where @value{GDBN} is running (the @dfn{host}
12667 machine). In general terms, the scheme looks like this:
12671 @value{GDBN} already understands how to use this protocol; when everything
12672 else is set up, you can simply use the @samp{target remote} command
12673 (@pxref{Targets,,Specifying a Debugging Target}).
12675 @item On the target,
12676 you must link with your program a few special-purpose subroutines that
12677 implement the @value{GDBN} remote serial protocol. The file containing these
12678 subroutines is called a @dfn{debugging stub}.
12680 On certain remote targets, you can use an auxiliary program
12681 @code{gdbserver} instead of linking a stub into your program.
12682 @xref{Server,,Using the @code{gdbserver} program}, for details.
12685 The debugging stub is specific to the architecture of the remote
12686 machine; for example, use @file{sparc-stub.c} to debug programs on
12689 @cindex remote serial stub list
12690 These working remote stubs are distributed with @value{GDBN}:
12695 @cindex @file{i386-stub.c}
12698 For Intel 386 and compatible architectures.
12701 @cindex @file{m68k-stub.c}
12702 @cindex Motorola 680x0
12704 For Motorola 680x0 architectures.
12707 @cindex @file{sh-stub.c}
12710 For Renesas SH architectures.
12713 @cindex @file{sparc-stub.c}
12715 For @sc{sparc} architectures.
12717 @item sparcl-stub.c
12718 @cindex @file{sparcl-stub.c}
12721 For Fujitsu @sc{sparclite} architectures.
12725 The @file{README} file in the @value{GDBN} distribution may list other
12726 recently added stubs.
12729 * Stub Contents:: What the stub can do for you
12730 * Bootstrapping:: What you must do for the stub
12731 * Debug Session:: Putting it all together
12734 @node Stub Contents
12735 @subsection What the stub can do for you
12737 @cindex remote serial stub
12738 The debugging stub for your architecture supplies these three
12742 @item set_debug_traps
12743 @findex set_debug_traps
12744 @cindex remote serial stub, initialization
12745 This routine arranges for @code{handle_exception} to run when your
12746 program stops. You must call this subroutine explicitly near the
12747 beginning of your program.
12749 @item handle_exception
12750 @findex handle_exception
12751 @cindex remote serial stub, main routine
12752 This is the central workhorse, but your program never calls it
12753 explicitly---the setup code arranges for @code{handle_exception} to
12754 run when a trap is triggered.
12756 @code{handle_exception} takes control when your program stops during
12757 execution (for example, on a breakpoint), and mediates communications
12758 with @value{GDBN} on the host machine. This is where the communications
12759 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
12760 representative on the target machine. It begins by sending summary
12761 information on the state of your program, then continues to execute,
12762 retrieving and transmitting any information @value{GDBN} needs, until you
12763 execute a @value{GDBN} command that makes your program resume; at that point,
12764 @code{handle_exception} returns control to your own code on the target
12768 @cindex @code{breakpoint} subroutine, remote
12769 Use this auxiliary subroutine to make your program contain a
12770 breakpoint. Depending on the particular situation, this may be the only
12771 way for @value{GDBN} to get control. For instance, if your target
12772 machine has some sort of interrupt button, you won't need to call this;
12773 pressing the interrupt button transfers control to
12774 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
12775 simply receiving characters on the serial port may also trigger a trap;
12776 again, in that situation, you don't need to call @code{breakpoint} from
12777 your own program---simply running @samp{target remote} from the host
12778 @value{GDBN} session gets control.
12780 Call @code{breakpoint} if none of these is true, or if you simply want
12781 to make certain your program stops at a predetermined point for the
12782 start of your debugging session.
12785 @node Bootstrapping
12786 @subsection What you must do for the stub
12788 @cindex remote stub, support routines
12789 The debugging stubs that come with @value{GDBN} are set up for a particular
12790 chip architecture, but they have no information about the rest of your
12791 debugging target machine.
12793 First of all you need to tell the stub how to communicate with the
12797 @item int getDebugChar()
12798 @findex getDebugChar
12799 Write this subroutine to read a single character from the serial port.
12800 It may be identical to @code{getchar} for your target system; a
12801 different name is used to allow you to distinguish the two if you wish.
12803 @item void putDebugChar(int)
12804 @findex putDebugChar
12805 Write this subroutine to write a single character to the serial port.
12806 It may be identical to @code{putchar} for your target system; a
12807 different name is used to allow you to distinguish the two if you wish.
12810 @cindex control C, and remote debugging
12811 @cindex interrupting remote targets
12812 If you want @value{GDBN} to be able to stop your program while it is
12813 running, you need to use an interrupt-driven serial driver, and arrange
12814 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
12815 character). That is the character which @value{GDBN} uses to tell the
12816 remote system to stop.
12818 Getting the debugging target to return the proper status to @value{GDBN}
12819 probably requires changes to the standard stub; one quick and dirty way
12820 is to just execute a breakpoint instruction (the ``dirty'' part is that
12821 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
12823 Other routines you need to supply are:
12826 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
12827 @findex exceptionHandler
12828 Write this function to install @var{exception_address} in the exception
12829 handling tables. You need to do this because the stub does not have any
12830 way of knowing what the exception handling tables on your target system
12831 are like (for example, the processor's table might be in @sc{rom},
12832 containing entries which point to a table in @sc{ram}).
12833 @var{exception_number} is the exception number which should be changed;
12834 its meaning is architecture-dependent (for example, different numbers
12835 might represent divide by zero, misaligned access, etc). When this
12836 exception occurs, control should be transferred directly to
12837 @var{exception_address}, and the processor state (stack, registers,
12838 and so on) should be just as it is when a processor exception occurs. So if
12839 you want to use a jump instruction to reach @var{exception_address}, it
12840 should be a simple jump, not a jump to subroutine.
12842 For the 386, @var{exception_address} should be installed as an interrupt
12843 gate so that interrupts are masked while the handler runs. The gate
12844 should be at privilege level 0 (the most privileged level). The
12845 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
12846 help from @code{exceptionHandler}.
12848 @item void flush_i_cache()
12849 @findex flush_i_cache
12850 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
12851 instruction cache, if any, on your target machine. If there is no
12852 instruction cache, this subroutine may be a no-op.
12854 On target machines that have instruction caches, @value{GDBN} requires this
12855 function to make certain that the state of your program is stable.
12859 You must also make sure this library routine is available:
12862 @item void *memset(void *, int, int)
12864 This is the standard library function @code{memset} that sets an area of
12865 memory to a known value. If you have one of the free versions of
12866 @code{libc.a}, @code{memset} can be found there; otherwise, you must
12867 either obtain it from your hardware manufacturer, or write your own.
12870 If you do not use the GNU C compiler, you may need other standard
12871 library subroutines as well; this varies from one stub to another,
12872 but in general the stubs are likely to use any of the common library
12873 subroutines which @code{@value{GCC}} generates as inline code.
12876 @node Debug Session
12877 @subsection Putting it all together
12879 @cindex remote serial debugging summary
12880 In summary, when your program is ready to debug, you must follow these
12885 Make sure you have defined the supporting low-level routines
12886 (@pxref{Bootstrapping,,What you must do for the stub}):
12888 @code{getDebugChar}, @code{putDebugChar},
12889 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
12893 Insert these lines near the top of your program:
12901 For the 680x0 stub only, you need to provide a variable called
12902 @code{exceptionHook}. Normally you just use:
12905 void (*exceptionHook)() = 0;
12909 but if before calling @code{set_debug_traps}, you set it to point to a
12910 function in your program, that function is called when
12911 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
12912 error). The function indicated by @code{exceptionHook} is called with
12913 one parameter: an @code{int} which is the exception number.
12916 Compile and link together: your program, the @value{GDBN} debugging stub for
12917 your target architecture, and the supporting subroutines.
12920 Make sure you have a serial connection between your target machine and
12921 the @value{GDBN} host, and identify the serial port on the host.
12924 @c The "remote" target now provides a `load' command, so we should
12925 @c document that. FIXME.
12926 Download your program to your target machine (or get it there by
12927 whatever means the manufacturer provides), and start it.
12930 Start @value{GDBN} on the host, and connect to the target
12931 (@pxref{Connecting,,Connecting to a remote target}).
12935 @node Configurations
12936 @chapter Configuration-Specific Information
12938 While nearly all @value{GDBN} commands are available for all native and
12939 cross versions of the debugger, there are some exceptions. This chapter
12940 describes things that are only available in certain configurations.
12942 There are three major categories of configurations: native
12943 configurations, where the host and target are the same, embedded
12944 operating system configurations, which are usually the same for several
12945 different processor architectures, and bare embedded processors, which
12946 are quite different from each other.
12951 * Embedded Processors::
12958 This section describes details specific to particular native
12963 * BSD libkvm Interface:: Debugging BSD kernel memory images
12964 * SVR4 Process Information:: SVR4 process information
12965 * DJGPP Native:: Features specific to the DJGPP port
12966 * Cygwin Native:: Features specific to the Cygwin port
12967 * Hurd Native:: Features specific to @sc{gnu} Hurd
12968 * Neutrino:: Features specific to QNX Neutrino
12974 On HP-UX systems, if you refer to a function or variable name that
12975 begins with a dollar sign, @value{GDBN} searches for a user or system
12976 name first, before it searches for a convenience variable.
12979 @node BSD libkvm Interface
12980 @subsection BSD libkvm Interface
12983 @cindex kernel memory image
12984 @cindex kernel crash dump
12986 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
12987 interface that provides a uniform interface for accessing kernel virtual
12988 memory images, including live systems and crash dumps. @value{GDBN}
12989 uses this interface to allow you to debug live kernels and kernel crash
12990 dumps on many native BSD configurations. This is implemented as a
12991 special @code{kvm} debugging target. For debugging a live system, load
12992 the currently running kernel into @value{GDBN} and connect to the
12996 (@value{GDBP}) @b{target kvm}
12999 For debugging crash dumps, provide the file name of the crash dump as an
13003 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
13006 Once connected to the @code{kvm} target, the following commands are
13012 Set current context from the @dfn{Process Control Block} (PCB) address.
13015 Set current context from proc address. This command isn't available on
13016 modern FreeBSD systems.
13019 @node SVR4 Process Information
13020 @subsection SVR4 process information
13022 @cindex examine process image
13023 @cindex process info via @file{/proc}
13025 Many versions of SVR4 and compatible systems provide a facility called
13026 @samp{/proc} that can be used to examine the image of a running
13027 process using file-system subroutines. If @value{GDBN} is configured
13028 for an operating system with this facility, the command @code{info
13029 proc} is available to report information about the process running
13030 your program, or about any process running on your system. @code{info
13031 proc} works only on SVR4 systems that include the @code{procfs} code.
13032 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
13033 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
13039 @itemx info proc @var{process-id}
13040 Summarize available information about any running process. If a
13041 process ID is specified by @var{process-id}, display information about
13042 that process; otherwise display information about the program being
13043 debugged. The summary includes the debugged process ID, the command
13044 line used to invoke it, its current working directory, and its
13045 executable file's absolute file name.
13047 On some systems, @var{process-id} can be of the form
13048 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
13049 within a process. If the optional @var{pid} part is missing, it means
13050 a thread from the process being debugged (the leading @samp{/} still
13051 needs to be present, or else @value{GDBN} will interpret the number as
13052 a process ID rather than a thread ID).
13054 @item info proc mappings
13055 @cindex memory address space mappings
13056 Report the memory address space ranges accessible in the program, with
13057 information on whether the process has read, write, or execute access
13058 rights to each range. On @sc{gnu}/Linux systems, each memory range
13059 includes the object file which is mapped to that range, instead of the
13060 memory access rights to that range.
13062 @item info proc stat
13063 @itemx info proc status
13064 @cindex process detailed status information
13065 These subcommands are specific to @sc{gnu}/Linux systems. They show
13066 the process-related information, including the user ID and group ID;
13067 how many threads are there in the process; its virtual memory usage;
13068 the signals that are pending, blocked, and ignored; its TTY; its
13069 consumption of system and user time; its stack size; its @samp{nice}
13070 value; etc. For more information, see the @samp{proc} man page
13071 (type @kbd{man 5 proc} from your shell prompt).
13073 @item info proc all
13074 Show all the information about the process described under all of the
13075 above @code{info proc} subcommands.
13078 @comment These sub-options of 'info proc' were not included when
13079 @comment procfs.c was re-written. Keep their descriptions around
13080 @comment against the day when someone finds the time to put them back in.
13081 @kindex info proc times
13082 @item info proc times
13083 Starting time, user CPU time, and system CPU time for your program and
13086 @kindex info proc id
13088 Report on the process IDs related to your program: its own process ID,
13089 the ID of its parent, the process group ID, and the session ID.
13092 @item set procfs-trace
13093 @kindex set procfs-trace
13094 @cindex @code{procfs} API calls
13095 This command enables and disables tracing of @code{procfs} API calls.
13097 @item show procfs-trace
13098 @kindex show procfs-trace
13099 Show the current state of @code{procfs} API call tracing.
13101 @item set procfs-file @var{file}
13102 @kindex set procfs-file
13103 Tell @value{GDBN} to write @code{procfs} API trace to the named
13104 @var{file}. @value{GDBN} appends the trace info to the previous
13105 contents of the file. The default is to display the trace on the
13108 @item show procfs-file
13109 @kindex show procfs-file
13110 Show the file to which @code{procfs} API trace is written.
13112 @item proc-trace-entry
13113 @itemx proc-trace-exit
13114 @itemx proc-untrace-entry
13115 @itemx proc-untrace-exit
13116 @kindex proc-trace-entry
13117 @kindex proc-trace-exit
13118 @kindex proc-untrace-entry
13119 @kindex proc-untrace-exit
13120 These commands enable and disable tracing of entries into and exits
13121 from the @code{syscall} interface.
13124 @kindex info pidlist
13125 @cindex process list, QNX Neutrino
13126 For QNX Neutrino only, this command displays the list of all the
13127 processes and all the threads within each process.
13130 @kindex info meminfo
13131 @cindex mapinfo list, QNX Neutrino
13132 For QNX Neutrino only, this command displays the list of all mapinfos.
13136 @subsection Features for Debugging @sc{djgpp} Programs
13137 @cindex @sc{djgpp} debugging
13138 @cindex native @sc{djgpp} debugging
13139 @cindex MS-DOS-specific commands
13142 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
13143 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
13144 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
13145 top of real-mode DOS systems and their emulations.
13147 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
13148 defines a few commands specific to the @sc{djgpp} port. This
13149 subsection describes those commands.
13154 This is a prefix of @sc{djgpp}-specific commands which print
13155 information about the target system and important OS structures.
13158 @cindex MS-DOS system info
13159 @cindex free memory information (MS-DOS)
13160 @item info dos sysinfo
13161 This command displays assorted information about the underlying
13162 platform: the CPU type and features, the OS version and flavor, the
13163 DPMI version, and the available conventional and DPMI memory.
13168 @cindex segment descriptor tables
13169 @cindex descriptor tables display
13171 @itemx info dos ldt
13172 @itemx info dos idt
13173 These 3 commands display entries from, respectively, Global, Local,
13174 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
13175 tables are data structures which store a descriptor for each segment
13176 that is currently in use. The segment's selector is an index into a
13177 descriptor table; the table entry for that index holds the
13178 descriptor's base address and limit, and its attributes and access
13181 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
13182 segment (used for both data and the stack), and a DOS segment (which
13183 allows access to DOS/BIOS data structures and absolute addresses in
13184 conventional memory). However, the DPMI host will usually define
13185 additional segments in order to support the DPMI environment.
13187 @cindex garbled pointers
13188 These commands allow to display entries from the descriptor tables.
13189 Without an argument, all entries from the specified table are
13190 displayed. An argument, which should be an integer expression, means
13191 display a single entry whose index is given by the argument. For
13192 example, here's a convenient way to display information about the
13193 debugged program's data segment:
13196 @exdent @code{(@value{GDBP}) info dos ldt $ds}
13197 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
13201 This comes in handy when you want to see whether a pointer is outside
13202 the data segment's limit (i.e.@: @dfn{garbled}).
13204 @cindex page tables display (MS-DOS)
13206 @itemx info dos pte
13207 These two commands display entries from, respectively, the Page
13208 Directory and the Page Tables. Page Directories and Page Tables are
13209 data structures which control how virtual memory addresses are mapped
13210 into physical addresses. A Page Table includes an entry for every
13211 page of memory that is mapped into the program's address space; there
13212 may be several Page Tables, each one holding up to 4096 entries. A
13213 Page Directory has up to 4096 entries, one each for every Page Table
13214 that is currently in use.
13216 Without an argument, @kbd{info dos pde} displays the entire Page
13217 Directory, and @kbd{info dos pte} displays all the entries in all of
13218 the Page Tables. An argument, an integer expression, given to the
13219 @kbd{info dos pde} command means display only that entry from the Page
13220 Directory table. An argument given to the @kbd{info dos pte} command
13221 means display entries from a single Page Table, the one pointed to by
13222 the specified entry in the Page Directory.
13224 @cindex direct memory access (DMA) on MS-DOS
13225 These commands are useful when your program uses @dfn{DMA} (Direct
13226 Memory Access), which needs physical addresses to program the DMA
13229 These commands are supported only with some DPMI servers.
13231 @cindex physical address from linear address
13232 @item info dos address-pte @var{addr}
13233 This command displays the Page Table entry for a specified linear
13234 address. The argument @var{addr} is a linear address which should
13235 already have the appropriate segment's base address added to it,
13236 because this command accepts addresses which may belong to @emph{any}
13237 segment. For example, here's how to display the Page Table entry for
13238 the page where a variable @code{i} is stored:
13241 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
13242 @exdent @code{Page Table entry for address 0x11a00d30:}
13243 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
13247 This says that @code{i} is stored at offset @code{0xd30} from the page
13248 whose physical base address is @code{0x02698000}, and shows all the
13249 attributes of that page.
13251 Note that you must cast the addresses of variables to a @code{char *},
13252 since otherwise the value of @code{__djgpp_base_address}, the base
13253 address of all variables and functions in a @sc{djgpp} program, will
13254 be added using the rules of C pointer arithmetics: if @code{i} is
13255 declared an @code{int}, @value{GDBN} will add 4 times the value of
13256 @code{__djgpp_base_address} to the address of @code{i}.
13258 Here's another example, it displays the Page Table entry for the
13262 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
13263 @exdent @code{Page Table entry for address 0x29110:}
13264 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
13268 (The @code{+ 3} offset is because the transfer buffer's address is the
13269 3rd member of the @code{_go32_info_block} structure.) The output
13270 clearly shows that this DPMI server maps the addresses in conventional
13271 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
13272 linear (@code{0x29110}) addresses are identical.
13274 This command is supported only with some DPMI servers.
13277 @cindex DOS serial data link, remote debugging
13278 In addition to native debugging, the DJGPP port supports remote
13279 debugging via a serial data link. The following commands are specific
13280 to remote serial debugging in the DJGPP port of @value{GDBN}.
13283 @kindex set com1base
13284 @kindex set com1irq
13285 @kindex set com2base
13286 @kindex set com2irq
13287 @kindex set com3base
13288 @kindex set com3irq
13289 @kindex set com4base
13290 @kindex set com4irq
13291 @item set com1base @var{addr}
13292 This command sets the base I/O port address of the @file{COM1} serial
13295 @item set com1irq @var{irq}
13296 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
13297 for the @file{COM1} serial port.
13299 There are similar commands @samp{set com2base}, @samp{set com3irq},
13300 etc.@: for setting the port address and the @code{IRQ} lines for the
13303 @kindex show com1base
13304 @kindex show com1irq
13305 @kindex show com2base
13306 @kindex show com2irq
13307 @kindex show com3base
13308 @kindex show com3irq
13309 @kindex show com4base
13310 @kindex show com4irq
13311 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
13312 display the current settings of the base address and the @code{IRQ}
13313 lines used by the COM ports.
13316 @kindex info serial
13317 @cindex DOS serial port status
13318 This command prints the status of the 4 DOS serial ports. For each
13319 port, it prints whether it's active or not, its I/O base address and
13320 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
13321 counts of various errors encountered so far.
13325 @node Cygwin Native
13326 @subsection Features for Debugging MS Windows PE executables
13327 @cindex MS Windows debugging
13328 @cindex native Cygwin debugging
13329 @cindex Cygwin-specific commands
13331 @value{GDBN} supports native debugging of MS Windows programs, including
13332 DLLs with and without symbolic debugging information. There are various
13333 additional Cygwin-specific commands, described in this subsection. The
13334 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
13335 that have no debugging symbols.
13341 This is a prefix of MS Windows specific commands which print
13342 information about the target system and important OS structures.
13344 @item info w32 selector
13345 This command displays information returned by
13346 the Win32 API @code{GetThreadSelectorEntry} function.
13347 It takes an optional argument that is evaluated to
13348 a long value to give the information about this given selector.
13349 Without argument, this command displays information
13350 about the the six segment registers.
13354 This is a Cygwin specific alias of info shared.
13356 @kindex dll-symbols
13358 This command loads symbols from a dll similarly to
13359 add-sym command but without the need to specify a base address.
13361 @kindex set new-console
13362 @item set new-console @var{mode}
13363 If @var{mode} is @code{on} the debuggee will
13364 be started in a new console on next start.
13365 If @var{mode} is @code{off}i, the debuggee will
13366 be started in the same console as the debugger.
13368 @kindex show new-console
13369 @item show new-console
13370 Displays whether a new console is used
13371 when the debuggee is started.
13373 @kindex set new-group
13374 @item set new-group @var{mode}
13375 This boolean value controls whether the debuggee should
13376 start a new group or stay in the same group as the debugger.
13377 This affects the way the Windows OS handles
13380 @kindex show new-group
13381 @item show new-group
13382 Displays current value of new-group boolean.
13384 @kindex set debugevents
13385 @item set debugevents
13386 This boolean value adds debug output concerning events seen by the debugger.
13388 @kindex set debugexec
13389 @item set debugexec
13390 This boolean value adds debug output concerning execute events
13391 seen by the debugger.
13393 @kindex set debugexceptions
13394 @item set debugexceptions
13395 This boolean value adds debug ouptut concerning exception events
13396 seen by the debugger.
13398 @kindex set debugmemory
13399 @item set debugmemory
13400 This boolean value adds debug ouptut concerning memory events
13401 seen by the debugger.
13405 This boolean values specifies whether the debuggee is called
13406 via a shell or directly (default value is on).
13410 Displays if the debuggee will be started with a shell.
13415 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
13418 @node Non-debug DLL symbols
13419 @subsubsection Support for DLLs without debugging symbols
13420 @cindex DLLs with no debugging symbols
13421 @cindex Minimal symbols and DLLs
13423 Very often on windows, some of the DLLs that your program relies on do
13424 not include symbolic debugging information (for example,
13425 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
13426 symbols in a DLL, it relies on the minimal amount of symbolic
13427 information contained in the DLL's export table. This subsubsection
13428 describes working with such symbols, known internally to @value{GDBN} as
13429 ``minimal symbols''.
13431 Note that before the debugged program has started execution, no DLLs
13432 will have been loaded. The easiest way around this problem is simply to
13433 start the program --- either by setting a breakpoint or letting the
13434 program run once to completion. It is also possible to force
13435 @value{GDBN} to load a particular DLL before starting the executable ---
13436 see the shared library information in @pxref{Files} or the
13437 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
13438 explicitly loading symbols from a DLL with no debugging information will
13439 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
13440 which may adversely affect symbol lookup performance.
13442 @subsubsection DLL name prefixes
13444 In keeping with the naming conventions used by the Microsoft debugging
13445 tools, DLL export symbols are made available with a prefix based on the
13446 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
13447 also entered into the symbol table, so @code{CreateFileA} is often
13448 sufficient. In some cases there will be name clashes within a program
13449 (particularly if the executable itself includes full debugging symbols)
13450 necessitating the use of the fully qualified name when referring to the
13451 contents of the DLL. Use single-quotes around the name to avoid the
13452 exclamation mark (``!'') being interpreted as a language operator.
13454 Note that the internal name of the DLL may be all upper-case, even
13455 though the file name of the DLL is lower-case, or vice-versa. Since
13456 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
13457 some confusion. If in doubt, try the @code{info functions} and
13458 @code{info variables} commands or even @code{maint print msymbols} (see
13459 @pxref{Symbols}). Here's an example:
13462 (@value{GDBP}) info function CreateFileA
13463 All functions matching regular expression "CreateFileA":
13465 Non-debugging symbols:
13466 0x77e885f4 CreateFileA
13467 0x77e885f4 KERNEL32!CreateFileA
13471 (@value{GDBP}) info function !
13472 All functions matching regular expression "!":
13474 Non-debugging symbols:
13475 0x6100114c cygwin1!__assert
13476 0x61004034 cygwin1!_dll_crt0@@0
13477 0x61004240 cygwin1!dll_crt0(per_process *)
13481 @subsubsection Working with minimal symbols
13483 Symbols extracted from a DLL's export table do not contain very much
13484 type information. All that @value{GDBN} can do is guess whether a symbol
13485 refers to a function or variable depending on the linker section that
13486 contains the symbol. Also note that the actual contents of the memory
13487 contained in a DLL are not available unless the program is running. This
13488 means that you cannot examine the contents of a variable or disassemble
13489 a function within a DLL without a running program.
13491 Variables are generally treated as pointers and dereferenced
13492 automatically. For this reason, it is often necessary to prefix a
13493 variable name with the address-of operator (``&'') and provide explicit
13494 type information in the command. Here's an example of the type of
13498 (@value{GDBP}) print 'cygwin1!__argv'
13503 (@value{GDBP}) x 'cygwin1!__argv'
13504 0x10021610: "\230y\""
13507 And two possible solutions:
13510 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
13511 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
13515 (@value{GDBP}) x/2x &'cygwin1!__argv'
13516 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
13517 (@value{GDBP}) x/x 0x10021608
13518 0x10021608: 0x0022fd98
13519 (@value{GDBP}) x/s 0x0022fd98
13520 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
13523 Setting a break point within a DLL is possible even before the program
13524 starts execution. However, under these circumstances, @value{GDBN} can't
13525 examine the initial instructions of the function in order to skip the
13526 function's frame set-up code. You can work around this by using ``*&''
13527 to set the breakpoint at a raw memory address:
13530 (@value{GDBP}) break *&'python22!PyOS_Readline'
13531 Breakpoint 1 at 0x1e04eff0
13534 The author of these extensions is not entirely convinced that setting a
13535 break point within a shared DLL like @file{kernel32.dll} is completely
13539 @subsection Commands specific to @sc{gnu} Hurd systems
13540 @cindex @sc{gnu} Hurd debugging
13542 This subsection describes @value{GDBN} commands specific to the
13543 @sc{gnu} Hurd native debugging.
13548 @kindex set signals@r{, Hurd command}
13549 @kindex set sigs@r{, Hurd command}
13550 This command toggles the state of inferior signal interception by
13551 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
13552 affected by this command. @code{sigs} is a shorthand alias for
13557 @kindex show signals@r{, Hurd command}
13558 @kindex show sigs@r{, Hurd command}
13559 Show the current state of intercepting inferior's signals.
13561 @item set signal-thread
13562 @itemx set sigthread
13563 @kindex set signal-thread
13564 @kindex set sigthread
13565 This command tells @value{GDBN} which thread is the @code{libc} signal
13566 thread. That thread is run when a signal is delivered to a running
13567 process. @code{set sigthread} is the shorthand alias of @code{set
13570 @item show signal-thread
13571 @itemx show sigthread
13572 @kindex show signal-thread
13573 @kindex show sigthread
13574 These two commands show which thread will run when the inferior is
13575 delivered a signal.
13578 @kindex set stopped@r{, Hurd command}
13579 This commands tells @value{GDBN} that the inferior process is stopped,
13580 as with the @code{SIGSTOP} signal. The stopped process can be
13581 continued by delivering a signal to it.
13584 @kindex show stopped@r{, Hurd command}
13585 This command shows whether @value{GDBN} thinks the debuggee is
13588 @item set exceptions
13589 @kindex set exceptions@r{, Hurd command}
13590 Use this command to turn off trapping of exceptions in the inferior.
13591 When exception trapping is off, neither breakpoints nor
13592 single-stepping will work. To restore the default, set exception
13595 @item show exceptions
13596 @kindex show exceptions@r{, Hurd command}
13597 Show the current state of trapping exceptions in the inferior.
13599 @item set task pause
13600 @kindex set task@r{, Hurd commands}
13601 @cindex task attributes (@sc{gnu} Hurd)
13602 @cindex pause current task (@sc{gnu} Hurd)
13603 This command toggles task suspension when @value{GDBN} has control.
13604 Setting it to on takes effect immediately, and the task is suspended
13605 whenever @value{GDBN} gets control. Setting it to off will take
13606 effect the next time the inferior is continued. If this option is set
13607 to off, you can use @code{set thread default pause on} or @code{set
13608 thread pause on} (see below) to pause individual threads.
13610 @item show task pause
13611 @kindex show task@r{, Hurd commands}
13612 Show the current state of task suspension.
13614 @item set task detach-suspend-count
13615 @cindex task suspend count
13616 @cindex detach from task, @sc{gnu} Hurd
13617 This command sets the suspend count the task will be left with when
13618 @value{GDBN} detaches from it.
13620 @item show task detach-suspend-count
13621 Show the suspend count the task will be left with when detaching.
13623 @item set task exception-port
13624 @itemx set task excp
13625 @cindex task exception port, @sc{gnu} Hurd
13626 This command sets the task exception port to which @value{GDBN} will
13627 forward exceptions. The argument should be the value of the @dfn{send
13628 rights} of the task. @code{set task excp} is a shorthand alias.
13630 @item set noninvasive
13631 @cindex noninvasive task options
13632 This command switches @value{GDBN} to a mode that is the least
13633 invasive as far as interfering with the inferior is concerned. This
13634 is the same as using @code{set task pause}, @code{set exceptions}, and
13635 @code{set signals} to values opposite to the defaults.
13637 @item info send-rights
13638 @itemx info receive-rights
13639 @itemx info port-rights
13640 @itemx info port-sets
13641 @itemx info dead-names
13644 @cindex send rights, @sc{gnu} Hurd
13645 @cindex receive rights, @sc{gnu} Hurd
13646 @cindex port rights, @sc{gnu} Hurd
13647 @cindex port sets, @sc{gnu} Hurd
13648 @cindex dead names, @sc{gnu} Hurd
13649 These commands display information about, respectively, send rights,
13650 receive rights, port rights, port sets, and dead names of a task.
13651 There are also shorthand aliases: @code{info ports} for @code{info
13652 port-rights} and @code{info psets} for @code{info port-sets}.
13654 @item set thread pause
13655 @kindex set thread@r{, Hurd command}
13656 @cindex thread properties, @sc{gnu} Hurd
13657 @cindex pause current thread (@sc{gnu} Hurd)
13658 This command toggles current thread suspension when @value{GDBN} has
13659 control. Setting it to on takes effect immediately, and the current
13660 thread is suspended whenever @value{GDBN} gets control. Setting it to
13661 off will take effect the next time the inferior is continued.
13662 Normally, this command has no effect, since when @value{GDBN} has
13663 control, the whole task is suspended. However, if you used @code{set
13664 task pause off} (see above), this command comes in handy to suspend
13665 only the current thread.
13667 @item show thread pause
13668 @kindex show thread@r{, Hurd command}
13669 This command shows the state of current thread suspension.
13671 @item set thread run
13672 This comamnd sets whether the current thread is allowed to run.
13674 @item show thread run
13675 Show whether the current thread is allowed to run.
13677 @item set thread detach-suspend-count
13678 @cindex thread suspend count, @sc{gnu} Hurd
13679 @cindex detach from thread, @sc{gnu} Hurd
13680 This command sets the suspend count @value{GDBN} will leave on a
13681 thread when detaching. This number is relative to the suspend count
13682 found by @value{GDBN} when it notices the thread; use @code{set thread
13683 takeover-suspend-count} to force it to an absolute value.
13685 @item show thread detach-suspend-count
13686 Show the suspend count @value{GDBN} will leave on the thread when
13689 @item set thread exception-port
13690 @itemx set thread excp
13691 Set the thread exception port to which to forward exceptions. This
13692 overrides the port set by @code{set task exception-port} (see above).
13693 @code{set thread excp} is the shorthand alias.
13695 @item set thread takeover-suspend-count
13696 Normally, @value{GDBN}'s thread suspend counts are relative to the
13697 value @value{GDBN} finds when it notices each thread. This command
13698 changes the suspend counts to be absolute instead.
13700 @item set thread default
13701 @itemx show thread default
13702 @cindex thread default settings, @sc{gnu} Hurd
13703 Each of the above @code{set thread} commands has a @code{set thread
13704 default} counterpart (e.g., @code{set thread default pause}, @code{set
13705 thread default exception-port}, etc.). The @code{thread default}
13706 variety of commands sets the default thread properties for all
13707 threads; you can then change the properties of individual threads with
13708 the non-default commands.
13713 @subsection QNX Neutrino
13714 @cindex QNX Neutrino
13716 @value{GDBN} provides the following commands specific to the QNX
13720 @item set debug nto-debug
13721 @kindex set debug nto-debug
13722 When set to on, enables debugging messages specific to the QNX
13725 @item show debug nto-debug
13726 @kindex show debug nto-debug
13727 Show the current state of QNX Neutrino messages.
13732 @section Embedded Operating Systems
13734 This section describes configurations involving the debugging of
13735 embedded operating systems that are available for several different
13739 * VxWorks:: Using @value{GDBN} with VxWorks
13742 @value{GDBN} includes the ability to debug programs running on
13743 various real-time operating systems.
13746 @subsection Using @value{GDBN} with VxWorks
13752 @kindex target vxworks
13753 @item target vxworks @var{machinename}
13754 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
13755 is the target system's machine name or IP address.
13759 On VxWorks, @code{load} links @var{filename} dynamically on the
13760 current target system as well as adding its symbols in @value{GDBN}.
13762 @value{GDBN} enables developers to spawn and debug tasks running on networked
13763 VxWorks targets from a Unix host. Already-running tasks spawned from
13764 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
13765 both the Unix host and on the VxWorks target. The program
13766 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
13767 installed with the name @code{vxgdb}, to distinguish it from a
13768 @value{GDBN} for debugging programs on the host itself.)
13771 @item VxWorks-timeout @var{args}
13772 @kindex vxworks-timeout
13773 All VxWorks-based targets now support the option @code{vxworks-timeout}.
13774 This option is set by the user, and @var{args} represents the number of
13775 seconds @value{GDBN} waits for responses to rpc's. You might use this if
13776 your VxWorks target is a slow software simulator or is on the far side
13777 of a thin network line.
13780 The following information on connecting to VxWorks was current when
13781 this manual was produced; newer releases of VxWorks may use revised
13784 @findex INCLUDE_RDB
13785 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
13786 to include the remote debugging interface routines in the VxWorks
13787 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
13788 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
13789 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
13790 source debugging task @code{tRdbTask} when VxWorks is booted. For more
13791 information on configuring and remaking VxWorks, see the manufacturer's
13793 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
13795 Once you have included @file{rdb.a} in your VxWorks system image and set
13796 your Unix execution search path to find @value{GDBN}, you are ready to
13797 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
13798 @code{vxgdb}, depending on your installation).
13800 @value{GDBN} comes up showing the prompt:
13807 * VxWorks Connection:: Connecting to VxWorks
13808 * VxWorks Download:: VxWorks download
13809 * VxWorks Attach:: Running tasks
13812 @node VxWorks Connection
13813 @subsubsection Connecting to VxWorks
13815 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
13816 network. To connect to a target whose host name is ``@code{tt}'', type:
13819 (vxgdb) target vxworks tt
13823 @value{GDBN} displays messages like these:
13826 Attaching remote machine across net...
13831 @value{GDBN} then attempts to read the symbol tables of any object modules
13832 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
13833 these files by searching the directories listed in the command search
13834 path (@pxref{Environment, ,Your program's environment}); if it fails
13835 to find an object file, it displays a message such as:
13838 prog.o: No such file or directory.
13841 When this happens, add the appropriate directory to the search path with
13842 the @value{GDBN} command @code{path}, and execute the @code{target}
13845 @node VxWorks Download
13846 @subsubsection VxWorks download
13848 @cindex download to VxWorks
13849 If you have connected to the VxWorks target and you want to debug an
13850 object that has not yet been loaded, you can use the @value{GDBN}
13851 @code{load} command to download a file from Unix to VxWorks
13852 incrementally. The object file given as an argument to the @code{load}
13853 command is actually opened twice: first by the VxWorks target in order
13854 to download the code, then by @value{GDBN} in order to read the symbol
13855 table. This can lead to problems if the current working directories on
13856 the two systems differ. If both systems have NFS mounted the same
13857 filesystems, you can avoid these problems by using absolute paths.
13858 Otherwise, it is simplest to set the working directory on both systems
13859 to the directory in which the object file resides, and then to reference
13860 the file by its name, without any path. For instance, a program
13861 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
13862 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
13863 program, type this on VxWorks:
13866 -> cd "@var{vxpath}/vw/demo/rdb"
13870 Then, in @value{GDBN}, type:
13873 (vxgdb) cd @var{hostpath}/vw/demo/rdb
13874 (vxgdb) load prog.o
13877 @value{GDBN} displays a response similar to this:
13880 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
13883 You can also use the @code{load} command to reload an object module
13884 after editing and recompiling the corresponding source file. Note that
13885 this makes @value{GDBN} delete all currently-defined breakpoints,
13886 auto-displays, and convenience variables, and to clear the value
13887 history. (This is necessary in order to preserve the integrity of
13888 debugger's data structures that reference the target system's symbol
13891 @node VxWorks Attach
13892 @subsubsection Running tasks
13894 @cindex running VxWorks tasks
13895 You can also attach to an existing task using the @code{attach} command as
13899 (vxgdb) attach @var{task}
13903 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
13904 or suspended when you attach to it. Running tasks are suspended at
13905 the time of attachment.
13907 @node Embedded Processors
13908 @section Embedded Processors
13910 This section goes into details specific to particular embedded
13913 @cindex send command to simulator
13914 Whenever a specific embedded processor has a simulator, @value{GDBN}
13915 allows to send an arbitrary command to the simulator.
13918 @item sim @var{command}
13919 @kindex sim@r{, a command}
13920 Send an arbitrary @var{command} string to the simulator. Consult the
13921 documentation for the specific simulator in use for information about
13922 acceptable commands.
13928 * H8/300:: Renesas H8/300
13929 * H8/500:: Renesas H8/500
13930 * M32R/D:: Renesas M32R/D
13931 * M68K:: Motorola M68K
13932 * MIPS Embedded:: MIPS Embedded
13933 * OpenRISC 1000:: OpenRisc 1000
13934 * PA:: HP PA Embedded
13937 * Sparclet:: Tsqware Sparclet
13938 * Sparclite:: Fujitsu Sparclite
13939 * ST2000:: Tandem ST2000
13940 * Z8000:: Zilog Z8000
13943 * Super-H:: Renesas Super-H
13944 * WinCE:: Windows CE child processes
13953 @item target rdi @var{dev}
13954 ARM Angel monitor, via RDI library interface to ADP protocol. You may
13955 use this target to communicate with both boards running the Angel
13956 monitor, or with the EmbeddedICE JTAG debug device.
13959 @item target rdp @var{dev}
13964 @value{GDBN} provides the following ARM-specific commands:
13967 @item set arm disassembler
13969 This commands selects from a list of disassembly styles. The
13970 @code{"std"} style is the standard style.
13972 @item show arm disassembler
13974 Show the current disassembly style.
13976 @item set arm apcs32
13977 @cindex ARM 32-bit mode
13978 This command toggles ARM operation mode between 32-bit and 26-bit.
13980 @item show arm apcs32
13981 Display the current usage of the ARM 32-bit mode.
13983 @item set arm fpu @var{fputype}
13984 This command sets the ARM floating-point unit (FPU) type. The
13985 argument @var{fputype} can be one of these:
13989 Determine the FPU type by querying the OS ABI.
13991 Software FPU, with mixed-endian doubles on little-endian ARM
13994 GCC-compiled FPA co-processor.
13996 Software FPU with pure-endian doubles.
14002 Show the current type of the FPU.
14005 This command forces @value{GDBN} to use the specified ABI.
14008 Show the currently used ABI.
14010 @item set debug arm
14011 Toggle whether to display ARM-specific debugging messages from the ARM
14012 target support subsystem.
14014 @item show debug arm
14015 Show whether ARM-specific debugging messages are enabled.
14018 The following commands are available when an ARM target is debugged
14019 using the RDI interface:
14022 @item rdilogfile @r{[}@var{file}@r{]}
14024 @cindex ADP (Angel Debugger Protocol) logging
14025 Set the filename for the ADP (Angel Debugger Protocol) packet log.
14026 With an argument, sets the log file to the specified @var{file}. With
14027 no argument, show the current log file name. The default log file is
14030 @item rdilogenable @r{[}@var{arg}@r{]}
14031 @kindex rdilogenable
14032 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
14033 enables logging, with an argument 0 or @code{"no"} disables it. With
14034 no arguments displays the current setting. When logging is enabled,
14035 ADP packets exchanged between @value{GDBN} and the RDI target device
14036 are logged to a file.
14038 @item set rdiromatzero
14039 @kindex set rdiromatzero
14040 @cindex ROM at zero address, RDI
14041 Tell @value{GDBN} whether the target has ROM at address 0. If on,
14042 vector catching is disabled, so that zero address can be used. If off
14043 (the default), vector catching is enabled. For this command to take
14044 effect, it needs to be invoked prior to the @code{target rdi} command.
14046 @item show rdiromatzero
14047 @kindex show rdiromatzero
14048 Show the current setting of ROM at zero address.
14050 @item set rdiheartbeat
14051 @kindex set rdiheartbeat
14052 @cindex RDI heartbeat
14053 Enable or disable RDI heartbeat packets. It is not recommended to
14054 turn on this option, since it confuses ARM and EPI JTAG interface, as
14055 well as the Angel monitor.
14057 @item show rdiheartbeat
14058 @kindex show rdiheartbeat
14059 Show the setting of RDI heartbeat packets.
14064 @subsection Renesas H8/300
14068 @kindex target hms@r{, with H8/300}
14069 @item target hms @var{dev}
14070 A Renesas SH, H8/300, or H8/500 board, attached via serial line to your host.
14071 Use special commands @code{device} and @code{speed} to control the serial
14072 line and the communications speed used.
14074 @kindex target e7000@r{, with H8/300}
14075 @item target e7000 @var{dev}
14076 E7000 emulator for Renesas H8 and SH.
14078 @kindex target sh3@r{, with H8/300}
14079 @kindex target sh3e@r{, with H8/300}
14080 @item target sh3 @var{dev}
14081 @itemx target sh3e @var{dev}
14082 Renesas SH-3 and SH-3E target systems.
14086 @cindex download to H8/300 or H8/500
14087 @cindex H8/300 or H8/500 download
14088 @cindex download to Renesas SH
14089 @cindex Renesas SH download
14090 When you select remote debugging to a Renesas SH, H8/300, or H8/500
14091 board, the @code{load} command downloads your program to the Renesas
14092 board and also opens it as the current executable target for
14093 @value{GDBN} on your host (like the @code{file} command).
14095 @value{GDBN} needs to know these things to talk to your
14096 Renesas SH, H8/300, or H8/500:
14100 that you want to use @samp{target hms}, the remote debugging interface
14101 for Renesas microprocessors, or @samp{target e7000}, the in-circuit
14102 emulator for the Renesas SH and the Renesas 300H. (@samp{target hms} is
14103 the default when @value{GDBN} is configured specifically for the Renesas SH,
14104 H8/300, or H8/500.)
14107 what serial device connects your host to your Renesas board (the first
14108 serial device available on your host is the default).
14111 what speed to use over the serial device.
14115 * Renesas Boards:: Connecting to Renesas boards.
14116 * Renesas ICE:: Using the E7000 In-Circuit Emulator.
14117 * Renesas Special:: Special @value{GDBN} commands for Renesas micros.
14120 @node Renesas Boards
14121 @subsubsection Connecting to Renesas boards
14123 @c only for Unix hosts
14125 @cindex serial device, Renesas micros
14126 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
14127 need to explicitly set the serial device. The default @var{port} is the
14128 first available port on your host. This is only necessary on Unix
14129 hosts, where it is typically something like @file{/dev/ttya}.
14132 @cindex serial line speed, Renesas micros
14133 @code{@value{GDBN}} has another special command to set the communications
14134 speed: @samp{speed @var{bps}}. This command also is only used from Unix
14135 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
14136 the DOS @code{mode} command (for instance,
14137 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
14139 The @samp{device} and @samp{speed} commands are available only when you
14140 use a Unix host to debug your Renesas microprocessor programs. If you
14142 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
14143 called @code{asynctsr} to communicate with the development board
14144 through a PC serial port. You must also use the DOS @code{mode} command
14145 to set up the serial port on the DOS side.
14147 The following sample session illustrates the steps needed to start a
14148 program under @value{GDBN} control on an H8/300. The example uses a
14149 sample H8/300 program called @file{t.x}. The procedure is the same for
14150 the Renesas SH and the H8/500.
14152 First hook up your development board. In this example, we use a
14153 board attached to serial port @code{COM2}; if you use a different serial
14154 port, substitute its name in the argument of the @code{mode} command.
14155 When you call @code{asynctsr}, the auxiliary comms program used by the
14156 debugger, you give it just the numeric part of the serial port's name;
14157 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
14161 C:\H8300\TEST> asynctsr 2
14162 C:\H8300\TEST> mode com2:9600,n,8,1,p
14164 Resident portion of MODE loaded
14166 COM2: 9600, n, 8, 1, p
14171 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
14172 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
14173 disable it, or even boot without it, to use @code{asynctsr} to control
14174 your development board.
14177 @kindex target hms@r{, and serial protocol}
14178 Now that serial communications are set up, and the development board is
14179 connected, you can start up @value{GDBN}. Call @code{@value{GDBN}} with
14180 the name of your program as the argument. @code{@value{GDBN}} prompts
14181 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
14182 commands to begin your debugging session: @samp{target hms} to specify
14183 cross-debugging to the Renesas board, and the @code{load} command to
14184 download your program to the board. @code{load} displays the names of
14185 the program's sections, and a @samp{*} for each 2K of data downloaded.
14186 (If you want to refresh @value{GDBN} data on symbols or on the
14187 executable file without downloading, use the @value{GDBN} commands
14188 @code{file} or @code{symbol-file}. These commands, and @code{load}
14189 itself, are described in @ref{Files,,Commands to specify files}.)
14192 (eg-C:\H8300\TEST) @value{GDBP} t.x
14193 @value{GDBN} is free software and you are welcome to distribute copies
14194 of it under certain conditions; type "show copying" to see
14196 There is absolutely no warranty for @value{GDBN}; type "show warranty"
14198 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
14199 (@value{GDBP}) target hms
14200 Connected to remote H8/300 HMS system.
14201 (@value{GDBP}) load t.x
14202 .text : 0x8000 .. 0xabde ***********
14203 .data : 0xabde .. 0xad30 *
14204 .stack : 0xf000 .. 0xf014 *
14207 At this point, you're ready to run or debug your program. From here on,
14208 you can use all the usual @value{GDBN} commands. The @code{break} command
14209 sets breakpoints; the @code{run} command starts your program;
14210 @code{print} or @code{x} display data; the @code{continue} command
14211 resumes execution after stopping at a breakpoint. You can use the
14212 @code{help} command at any time to find out more about @value{GDBN} commands.
14214 Remember, however, that @emph{operating system} facilities aren't
14215 available on your development board; for example, if your program hangs,
14216 you can't send an interrupt---but you can press the @sc{reset} switch!
14218 Use the @sc{reset} button on the development board
14221 to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
14222 no way to pass an interrupt signal to the development board); and
14225 to return to the @value{GDBN} command prompt after your program finishes
14226 normally. The communications protocol provides no other way for @value{GDBN}
14227 to detect program completion.
14230 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
14231 development board as a ``normal exit'' of your program.
14234 @subsubsection Using the E7000 in-circuit emulator
14236 @kindex target e7000@r{, with Renesas ICE}
14237 You can use the E7000 in-circuit emulator to develop code for either the
14238 Renesas SH or the H8/300H. Use one of these forms of the @samp{target
14239 e7000} command to connect @value{GDBN} to your E7000:
14242 @item target e7000 @var{port} @var{speed}
14243 Use this form if your E7000 is connected to a serial port. The
14244 @var{port} argument identifies what serial port to use (for example,
14245 @samp{com2}). The third argument is the line speed in bits per second
14246 (for example, @samp{9600}).
14248 @item target e7000 @var{hostname}
14249 If your E7000 is installed as a host on a TCP/IP network, you can just
14250 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
14253 The following special commands are available when debugging with the
14257 @item e7000 @var{command}
14259 @cindex send command to E7000 monitor
14260 This sends the specified @var{command} to the E7000 monitor.
14262 @item ftplogin @var{machine} @var{username} @var{password} @var{dir}
14263 @kindex ftplogin@r{, E7000}
14264 This command records information for subsequent interface with the
14265 E7000 monitor via the FTP protocol: @value{GDBN} will log into the
14266 named @var{machine} using specified @var{username} and @var{password},
14267 and then chdir to the named directory @var{dir}.
14269 @item ftpload @var{file}
14270 @kindex ftpload@r{, E7000}
14271 This command uses credentials recorded by @code{ftplogin} to fetch and
14272 load the named @var{file} from the E7000 monitor.
14275 @kindex drain@r{, E7000}
14276 This command drains any pending text buffers stored on the E7000.
14278 @item set usehardbreakpoints
14279 @itemx show usehardbreakpoints
14280 @kindex set usehardbreakpoints@r{, E7000}
14281 @kindex show usehardbreakpoints@r{, E7000}
14282 @cindex hardware breakpoints, and E7000
14283 These commands set and show the use of hardware breakpoints for all
14284 breakpoints. @xref{Set Breaks, hardware-assisted breakpoint}, for
14285 more information about using hardware breakpoints selectively.
14288 @node Renesas Special
14289 @subsubsection Special @value{GDBN} commands for Renesas micros
14291 Some @value{GDBN} commands are available only for the H8/300:
14295 @kindex set machine
14296 @kindex show machine
14297 @item set machine h8300
14298 @itemx set machine h8300h
14299 Condition @value{GDBN} for one of the two variants of the H8/300
14300 architecture with @samp{set machine}. You can use @samp{show machine}
14301 to check which variant is currently in effect.
14310 @kindex set memory @var{mod}
14311 @cindex memory models, H8/500
14312 @item set memory @var{mod}
14314 Specify which H8/500 memory model (@var{mod}) you are using with
14315 @samp{set memory}; check which memory model is in effect with @samp{show
14316 memory}. The accepted values for @var{mod} are @code{small},
14317 @code{big}, @code{medium}, and @code{compact}.
14322 @subsection Renesas M32R/D and M32R/SDI
14325 @kindex target m32r
14326 @item target m32r @var{dev}
14327 Renesas M32R/D ROM monitor.
14329 @kindex target m32rsdi
14330 @item target m32rsdi @var{dev}
14331 Renesas M32R SDI server, connected via parallel port to the board.
14334 The following @value{GDBN} commands are specific to the M32R monitor:
14337 @item set download-path @var{path}
14338 @kindex set download-path
14339 @cindex find downloadable @sc{srec} files (M32R)
14340 Set the default path for finding donwloadable @sc{srec} files.
14342 @item show download-path
14343 @kindex show download-path
14344 Show the default path for downloadable @sc{srec} files.
14346 @item set board-address @var{addr}
14347 @kindex set board-address
14348 @cindex M32-EVA target board address
14349 Set the IP address for the M32R-EVA target board.
14351 @item show board-address
14352 @kindex show board-address
14353 Show the current IP address of the target board.
14355 @item set server-address @var{addr}
14356 @kindex set server-address
14357 @cindex download server address (M32R)
14358 Set the IP address for the download server, which is the @value{GDBN}'s
14361 @item show server-address
14362 @kindex show server-address
14363 Display the IP address of the download server.
14365 @item upload @r{[}@var{file}@r{]}
14366 @kindex upload@r{, M32R}
14367 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
14368 upload capability. If no @var{file} argument is given, the current
14369 executable file is uploaded.
14371 @item tload @r{[}@var{file}@r{]}
14372 @kindex tload@r{, M32R}
14373 Test the @code{upload} command.
14376 The following commands are available for M32R/SDI:
14381 @cindex reset SDI connection, M32R
14382 This command resets the SDI connection.
14386 This command shows the SDI connection status.
14389 @kindex debug_chaos
14390 @cindex M32R/Chaos debugging
14391 Instructs the remote that M32R/Chaos debugging is to be used.
14393 @item use_debug_dma
14394 @kindex use_debug_dma
14395 Instructs the remote to use the DEBUG_DMA method of accessing memory.
14398 @kindex use_mon_code
14399 Instructs the remote to use the MON_CODE method of accessing memory.
14402 @kindex use_ib_break
14403 Instructs the remote to set breakpoints by IB break.
14405 @item use_dbt_break
14406 @kindex use_dbt_break
14407 Instructs the remote to set breakpoints by DBT.
14413 The Motorola m68k configuration includes ColdFire support, and
14414 target command for the following ROM monitors.
14418 @kindex target abug
14419 @item target abug @var{dev}
14420 ABug ROM monitor for M68K.
14422 @kindex target cpu32bug
14423 @item target cpu32bug @var{dev}
14424 CPU32BUG monitor, running on a CPU32 (M68K) board.
14426 @kindex target dbug
14427 @item target dbug @var{dev}
14428 dBUG ROM monitor for Motorola ColdFire.
14431 @item target est @var{dev}
14432 EST-300 ICE monitor, running on a CPU32 (M68K) board.
14434 @kindex target rom68k
14435 @item target rom68k @var{dev}
14436 ROM 68K monitor, running on an M68K IDP board.
14442 @kindex target rombug
14443 @item target rombug @var{dev}
14444 ROMBUG ROM monitor for OS/9000.
14448 @node MIPS Embedded
14449 @subsection MIPS Embedded
14451 @cindex MIPS boards
14452 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
14453 MIPS board attached to a serial line. This is available when
14454 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
14457 Use these @value{GDBN} commands to specify the connection to your target board:
14460 @item target mips @var{port}
14461 @kindex target mips @var{port}
14462 To run a program on the board, start up @code{@value{GDBP}} with the
14463 name of your program as the argument. To connect to the board, use the
14464 command @samp{target mips @var{port}}, where @var{port} is the name of
14465 the serial port connected to the board. If the program has not already
14466 been downloaded to the board, you may use the @code{load} command to
14467 download it. You can then use all the usual @value{GDBN} commands.
14469 For example, this sequence connects to the target board through a serial
14470 port, and loads and runs a program called @var{prog} through the
14474 host$ @value{GDBP} @var{prog}
14475 @value{GDBN} is free software and @dots{}
14476 (@value{GDBP}) target mips /dev/ttyb
14477 (@value{GDBP}) load @var{prog}
14481 @item target mips @var{hostname}:@var{portnumber}
14482 On some @value{GDBN} host configurations, you can specify a TCP
14483 connection (for instance, to a serial line managed by a terminal
14484 concentrator) instead of a serial port, using the syntax
14485 @samp{@var{hostname}:@var{portnumber}}.
14487 @item target pmon @var{port}
14488 @kindex target pmon @var{port}
14491 @item target ddb @var{port}
14492 @kindex target ddb @var{port}
14493 NEC's DDB variant of PMON for Vr4300.
14495 @item target lsi @var{port}
14496 @kindex target lsi @var{port}
14497 LSI variant of PMON.
14499 @kindex target r3900
14500 @item target r3900 @var{dev}
14501 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
14503 @kindex target array
14504 @item target array @var{dev}
14505 Array Tech LSI33K RAID controller board.
14511 @value{GDBN} also supports these special commands for MIPS targets:
14514 @item set mipsfpu double
14515 @itemx set mipsfpu single
14516 @itemx set mipsfpu none
14517 @itemx set mipsfpu auto
14518 @itemx show mipsfpu
14519 @kindex set mipsfpu
14520 @kindex show mipsfpu
14521 @cindex MIPS remote floating point
14522 @cindex floating point, MIPS remote
14523 If your target board does not support the MIPS floating point
14524 coprocessor, you should use the command @samp{set mipsfpu none} (if you
14525 need this, you may wish to put the command in your @value{GDBN} init
14526 file). This tells @value{GDBN} how to find the return value of
14527 functions which return floating point values. It also allows
14528 @value{GDBN} to avoid saving the floating point registers when calling
14529 functions on the board. If you are using a floating point coprocessor
14530 with only single precision floating point support, as on the @sc{r4650}
14531 processor, use the command @samp{set mipsfpu single}. The default
14532 double precision floating point coprocessor may be selected using
14533 @samp{set mipsfpu double}.
14535 In previous versions the only choices were double precision or no
14536 floating point, so @samp{set mipsfpu on} will select double precision
14537 and @samp{set mipsfpu off} will select no floating point.
14539 As usual, you can inquire about the @code{mipsfpu} variable with
14540 @samp{show mipsfpu}.
14542 @item set timeout @var{seconds}
14543 @itemx set retransmit-timeout @var{seconds}
14544 @itemx show timeout
14545 @itemx show retransmit-timeout
14546 @cindex @code{timeout}, MIPS protocol
14547 @cindex @code{retransmit-timeout}, MIPS protocol
14548 @kindex set timeout
14549 @kindex show timeout
14550 @kindex set retransmit-timeout
14551 @kindex show retransmit-timeout
14552 You can control the timeout used while waiting for a packet, in the MIPS
14553 remote protocol, with the @code{set timeout @var{seconds}} command. The
14554 default is 5 seconds. Similarly, you can control the timeout used while
14555 waiting for an acknowledgement of a packet with the @code{set
14556 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
14557 You can inspect both values with @code{show timeout} and @code{show
14558 retransmit-timeout}. (These commands are @emph{only} available when
14559 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
14561 The timeout set by @code{set timeout} does not apply when @value{GDBN}
14562 is waiting for your program to stop. In that case, @value{GDBN} waits
14563 forever because it has no way of knowing how long the program is going
14564 to run before stopping.
14566 @item set syn-garbage-limit @var{num}
14567 @kindex set syn-garbage-limit@r{, MIPS remote}
14568 @cindex synchronize with remote MIPS target
14569 Limit the maximum number of characters @value{GDBN} should ignore when
14570 it tries to synchronize with the remote target. The default is 10
14571 characters. Setting the limit to -1 means there's no limit.
14573 @item show syn-garbage-limit
14574 @kindex show syn-garbage-limit@r{, MIPS remote}
14575 Show the current limit on the number of characters to ignore when
14576 trying to synchronize with the remote system.
14578 @item set monitor-prompt @var{prompt}
14579 @kindex set monitor-prompt@r{, MIPS remote}
14580 @cindex remote monitor prompt
14581 Tell @value{GDBN} to expect the specified @var{prompt} string from the
14582 remote monitor. The default depends on the target:
14592 @item show monitor-prompt
14593 @kindex show monitor-prompt@r{, MIPS remote}
14594 Show the current strings @value{GDBN} expects as the prompt from the
14597 @item set monitor-warnings
14598 @kindex set monitor-warnings@r{, MIPS remote}
14599 Enable or disable monitor warnings about hardware breakpoints. This
14600 has effect only for the @code{lsi} target. When on, @value{GDBN} will
14601 display warning messages whose codes are returned by the @code{lsi}
14602 PMON monitor for breakpoint commands.
14604 @item show monitor-warnings
14605 @kindex show monitor-warnings@r{, MIPS remote}
14606 Show the current setting of printing monitor warnings.
14608 @item pmon @var{command}
14609 @kindex pmon@r{, MIPS remote}
14610 @cindex send PMON command
14611 This command allows sending an arbitrary @var{command} string to the
14612 monitor. The monitor must be in debug mode for this to work.
14615 @node OpenRISC 1000
14616 @subsection OpenRISC 1000
14617 @cindex OpenRISC 1000
14619 @cindex or1k boards
14620 See OR1k Architecture document (@uref{www.opencores.org}) for more information
14621 about platform and commands.
14625 @kindex target jtag
14626 @item target jtag jtag://@var{host}:@var{port}
14628 Connects to remote JTAG server.
14629 JTAG remote server can be either an or1ksim or JTAG server,
14630 connected via parallel port to the board.
14632 Example: @code{target jtag jtag://localhost:9999}
14635 @item or1ksim @var{command}
14636 If connected to @code{or1ksim} OpenRISC 1000 Architectural
14637 Simulator, proprietary commands can be executed.
14639 @kindex info or1k spr
14640 @item info or1k spr
14641 Displays spr groups.
14643 @item info or1k spr @var{group}
14644 @itemx info or1k spr @var{groupno}
14645 Displays register names in selected group.
14647 @item info or1k spr @var{group} @var{register}
14648 @itemx info or1k spr @var{register}
14649 @itemx info or1k spr @var{groupno} @var{registerno}
14650 @itemx info or1k spr @var{registerno}
14651 Shows information about specified spr register.
14654 @item spr @var{group} @var{register} @var{value}
14655 @itemx spr @var{register @var{value}}
14656 @itemx spr @var{groupno} @var{registerno @var{value}}
14657 @itemx spr @var{registerno @var{value}}
14658 Writes @var{value} to specified spr register.
14661 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
14662 It is very similar to @value{GDBN} trace, except it does not interfere with normal
14663 program execution and is thus much faster. Hardware breakpoints/watchpoint
14664 triggers can be set using:
14667 Load effective address/data
14669 Store effective address/data
14671 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
14676 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
14677 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
14679 @code{htrace} commands:
14680 @cindex OpenRISC 1000 htrace
14683 @item hwatch @var{conditional}
14684 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
14685 or Data. For example:
14687 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14689 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14693 Display information about current HW trace configuration.
14695 @item htrace trigger @var{conditional}
14696 Set starting criteria for HW trace.
14698 @item htrace qualifier @var{conditional}
14699 Set acquisition qualifier for HW trace.
14701 @item htrace stop @var{conditional}
14702 Set HW trace stopping criteria.
14704 @item htrace record [@var{data}]*
14705 Selects the data to be recorded, when qualifier is met and HW trace was
14708 @item htrace enable
14709 @itemx htrace disable
14710 Enables/disables the HW trace.
14712 @item htrace rewind [@var{filename}]
14713 Clears currently recorded trace data.
14715 If filename is specified, new trace file is made and any newly collected data
14716 will be written there.
14718 @item htrace print [@var{start} [@var{len}]]
14719 Prints trace buffer, using current record configuration.
14721 @item htrace mode continuous
14722 Set continuous trace mode.
14724 @item htrace mode suspend
14725 Set suspend trace mode.
14730 @subsection PowerPC
14733 @kindex target dink32
14734 @item target dink32 @var{dev}
14735 DINK32 ROM monitor.
14737 @kindex target ppcbug
14738 @item target ppcbug @var{dev}
14739 @kindex target ppcbug1
14740 @item target ppcbug1 @var{dev}
14741 PPCBUG ROM monitor for PowerPC.
14744 @item target sds @var{dev}
14745 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
14748 @cindex SDS protocol
14749 The following commands specifi to the SDS protocol are supported
14753 @item set sdstimeout @var{nsec}
14754 @kindex set sdstimeout
14755 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
14756 default is 2 seconds.
14758 @item show sdstimeout
14759 @kindex show sdstimeout
14760 Show the current value of the SDS timeout.
14762 @item sds @var{command}
14763 @kindex sds@r{, a command}
14764 Send the specified @var{command} string to the SDS monitor.
14769 @subsection HP PA Embedded
14773 @kindex target op50n
14774 @item target op50n @var{dev}
14775 OP50N monitor, running on an OKI HPPA board.
14777 @kindex target w89k
14778 @item target w89k @var{dev}
14779 W89K monitor, running on a Winbond HPPA board.
14784 @subsection Renesas SH
14788 @kindex target hms@r{, with Renesas SH}
14789 @item target hms @var{dev}
14790 A Renesas SH board attached via serial line to your host. Use special
14791 commands @code{device} and @code{speed} to control the serial line and
14792 the communications speed used.
14794 @kindex target e7000@r{, with Renesas SH}
14795 @item target e7000 @var{dev}
14796 E7000 emulator for Renesas SH.
14798 @kindex target sh3@r{, with SH}
14799 @kindex target sh3e@r{, with SH}
14800 @item target sh3 @var{dev}
14801 @item target sh3e @var{dev}
14802 Renesas SH-3 and SH-3E target systems.
14807 @subsection Tsqware Sparclet
14811 @value{GDBN} enables developers to debug tasks running on
14812 Sparclet targets from a Unix host.
14813 @value{GDBN} uses code that runs on
14814 both the Unix host and on the Sparclet target. The program
14815 @code{@value{GDBP}} is installed and executed on the Unix host.
14818 @item remotetimeout @var{args}
14819 @kindex remotetimeout
14820 @value{GDBN} supports the option @code{remotetimeout}.
14821 This option is set by the user, and @var{args} represents the number of
14822 seconds @value{GDBN} waits for responses.
14825 @cindex compiling, on Sparclet
14826 When compiling for debugging, include the options @samp{-g} to get debug
14827 information and @samp{-Ttext} to relocate the program to where you wish to
14828 load it on the target. You may also want to add the options @samp{-n} or
14829 @samp{-N} in order to reduce the size of the sections. Example:
14832 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
14835 You can use @code{objdump} to verify that the addresses are what you intended:
14838 sparclet-aout-objdump --headers --syms prog
14841 @cindex running, on Sparclet
14843 your Unix execution search path to find @value{GDBN}, you are ready to
14844 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
14845 (or @code{sparclet-aout-gdb}, depending on your installation).
14847 @value{GDBN} comes up showing the prompt:
14854 * Sparclet File:: Setting the file to debug
14855 * Sparclet Connection:: Connecting to Sparclet
14856 * Sparclet Download:: Sparclet download
14857 * Sparclet Execution:: Running and debugging
14860 @node Sparclet File
14861 @subsubsection Setting file to debug
14863 The @value{GDBN} command @code{file} lets you choose with program to debug.
14866 (gdbslet) file prog
14870 @value{GDBN} then attempts to read the symbol table of @file{prog}.
14871 @value{GDBN} locates
14872 the file by searching the directories listed in the command search
14874 If the file was compiled with debug information (option "-g"), source
14875 files will be searched as well.
14876 @value{GDBN} locates
14877 the source files by searching the directories listed in the directory search
14878 path (@pxref{Environment, ,Your program's environment}).
14880 to find a file, it displays a message such as:
14883 prog: No such file or directory.
14886 When this happens, add the appropriate directories to the search paths with
14887 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
14888 @code{target} command again.
14890 @node Sparclet Connection
14891 @subsubsection Connecting to Sparclet
14893 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
14894 To connect to a target on serial port ``@code{ttya}'', type:
14897 (gdbslet) target sparclet /dev/ttya
14898 Remote target sparclet connected to /dev/ttya
14899 main () at ../prog.c:3
14903 @value{GDBN} displays messages like these:
14909 @node Sparclet Download
14910 @subsubsection Sparclet download
14912 @cindex download to Sparclet
14913 Once connected to the Sparclet target,
14914 you can use the @value{GDBN}
14915 @code{load} command to download the file from the host to the target.
14916 The file name and load offset should be given as arguments to the @code{load}
14918 Since the file format is aout, the program must be loaded to the starting
14919 address. You can use @code{objdump} to find out what this value is. The load
14920 offset is an offset which is added to the VMA (virtual memory address)
14921 of each of the file's sections.
14922 For instance, if the program
14923 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
14924 and bss at 0x12010170, in @value{GDBN}, type:
14927 (gdbslet) load prog 0x12010000
14928 Loading section .text, size 0xdb0 vma 0x12010000
14931 If the code is loaded at a different address then what the program was linked
14932 to, you may need to use the @code{section} and @code{add-symbol-file} commands
14933 to tell @value{GDBN} where to map the symbol table.
14935 @node Sparclet Execution
14936 @subsubsection Running and debugging
14938 @cindex running and debugging Sparclet programs
14939 You can now begin debugging the task using @value{GDBN}'s execution control
14940 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
14941 manual for the list of commands.
14945 Breakpoint 1 at 0x12010000: file prog.c, line 3.
14947 Starting program: prog
14948 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
14949 3 char *symarg = 0;
14951 4 char *execarg = "hello!";
14956 @subsection Fujitsu Sparclite
14960 @kindex target sparclite
14961 @item target sparclite @var{dev}
14962 Fujitsu sparclite boards, used only for the purpose of loading.
14963 You must use an additional command to debug the program.
14964 For example: target remote @var{dev} using @value{GDBN} standard
14970 @subsection Tandem ST2000
14972 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
14975 To connect your ST2000 to the host system, see the manufacturer's
14976 manual. Once the ST2000 is physically attached, you can run:
14979 target st2000 @var{dev} @var{speed}
14983 to establish it as your debugging environment. @var{dev} is normally
14984 the name of a serial device, such as @file{/dev/ttya}, connected to the
14985 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
14986 connection (for example, to a serial line attached via a terminal
14987 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
14989 The @code{load} and @code{attach} commands are @emph{not} defined for
14990 this target; you must load your program into the ST2000 as you normally
14991 would for standalone operation. @value{GDBN} reads debugging information
14992 (such as symbols) from a separate, debugging version of the program
14993 available on your host computer.
14994 @c FIXME!! This is terribly vague; what little content is here is
14995 @c basically hearsay.
14997 @cindex ST2000 auxiliary commands
14998 These auxiliary @value{GDBN} commands are available to help you with the ST2000
15002 @item st2000 @var{command}
15003 @kindex st2000 @var{cmd}
15004 @cindex STDBUG commands (ST2000)
15005 @cindex commands to STDBUG (ST2000)
15006 Send a @var{command} to the STDBUG monitor. See the manufacturer's
15007 manual for available commands.
15010 @cindex connect (to STDBUG)
15011 Connect the controlling terminal to the STDBUG command monitor. When
15012 you are done interacting with STDBUG, typing either of two character
15013 sequences gets you back to the @value{GDBN} command prompt:
15014 @kbd{@key{RET}~.} (Return, followed by tilde and period) or
15015 @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
15019 @subsection Zilog Z8000
15022 @cindex simulator, Z8000
15023 @cindex Zilog Z8000 simulator
15025 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
15028 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
15029 unsegmented variant of the Z8000 architecture) or the Z8001 (the
15030 segmented variant). The simulator recognizes which architecture is
15031 appropriate by inspecting the object code.
15034 @item target sim @var{args}
15036 @kindex target sim@r{, with Z8000}
15037 Debug programs on a simulated CPU. If the simulator supports setup
15038 options, specify them via @var{args}.
15042 After specifying this target, you can debug programs for the simulated
15043 CPU in the same style as programs for your host computer; use the
15044 @code{file} command to load a new program image, the @code{run} command
15045 to run your program, and so on.
15047 As well as making available all the usual machine registers
15048 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
15049 additional items of information as specially named registers:
15054 Counts clock-ticks in the simulator.
15057 Counts instructions run in the simulator.
15060 Execution time in 60ths of a second.
15064 You can refer to these values in @value{GDBN} expressions with the usual
15065 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
15066 conditional breakpoint that suspends only after at least 5000
15067 simulated clock ticks.
15070 @subsection Atmel AVR
15073 When configured for debugging the Atmel AVR, @value{GDBN} supports the
15074 following AVR-specific commands:
15077 @item info io_registers
15078 @kindex info io_registers@r{, AVR}
15079 @cindex I/O registers (Atmel AVR)
15080 This command displays information about the AVR I/O registers. For
15081 each register, @value{GDBN} prints its number and value.
15088 When configured for debugging CRIS, @value{GDBN} provides the
15089 following CRIS-specific commands:
15092 @item set cris-version @var{ver}
15093 @cindex CRIS version
15094 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
15095 The CRIS version affects register names and sizes. This command is useful in
15096 case autodetection of the CRIS version fails.
15098 @item show cris-version
15099 Show the current CRIS version.
15101 @item set cris-dwarf2-cfi
15102 @cindex DWARF-2 CFI and CRIS
15103 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
15104 Change to @samp{off} when using @code{gcc-cris} whose version is below
15107 @item show cris-dwarf2-cfi
15108 Show the current state of using DWARF-2 CFI.
15110 @item set cris-mode @var{mode}
15112 Set the current CRIS mode to @var{mode}. It should only be changed when
15113 debugging in guru mode, in which case it should be set to
15114 @samp{guru} (the default is @samp{normal}).
15116 @item show cris-mode
15117 Show the current CRIS mode.
15121 @subsection Renesas Super-H
15124 For the Renesas Super-H processor, @value{GDBN} provides these
15129 @kindex regs@r{, Super-H}
15130 Show the values of all Super-H registers.
15134 @subsection Windows CE
15137 The following commands are available for Windows CE:
15140 @item set remotedirectory @var{dir}
15141 @kindex set remotedirectory
15142 Tell @value{GDBN} to upload files from the named directory @var{dir}.
15143 The default is @file{/gdb}, i.e.@: the root directory on the current
15146 @item show remotedirectory
15147 @kindex show remotedirectory
15148 Show the current value of the upload directory.
15150 @item set remoteupload @var{method}
15151 @kindex set remoteupload
15152 Set the method used to upload files to remote device. Valid values
15153 for @var{method} are @samp{always}, @samp{newer}, and @samp{never}.
15154 The default is @samp{newer}.
15156 @item show remoteupload
15157 @kindex show remoteupload
15158 Show the current setting of the upload method.
15160 @item set remoteaddhost
15161 @kindex set remoteaddhost
15162 Tell @value{GDBN} whether to add this host to the remote stub's
15163 arguments when you debug over a network.
15165 @item show remoteaddhost
15166 @kindex show remoteaddhost
15167 Show whether to add this host to remote stub's arguments when
15168 debugging over a network.
15172 @node Architectures
15173 @section Architectures
15175 This section describes characteristics of architectures that affect
15176 all uses of @value{GDBN} with the architecture, both native and cross.
15183 * HPPA:: HP PA architecture
15187 @subsection x86 Architecture-specific issues.
15190 @item set struct-convention @var{mode}
15191 @kindex set struct-convention
15192 @cindex struct return convention
15193 @cindex struct/union returned in registers
15194 Set the convention used by the inferior to return @code{struct}s and
15195 @code{union}s from functions to @var{mode}. Possible values of
15196 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
15197 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
15198 are returned on the stack, while @code{"reg"} means that a
15199 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
15200 be returned in a register.
15202 @item show struct-convention
15203 @kindex show struct-convention
15204 Show the current setting of the convention to return @code{struct}s
15213 @kindex set rstack_high_address
15214 @cindex AMD 29K register stack
15215 @cindex register stack, AMD29K
15216 @item set rstack_high_address @var{address}
15217 On AMD 29000 family processors, registers are saved in a separate
15218 @dfn{register stack}. There is no way for @value{GDBN} to determine the
15219 extent of this stack. Normally, @value{GDBN} just assumes that the
15220 stack is ``large enough''. This may result in @value{GDBN} referencing
15221 memory locations that do not exist. If necessary, you can get around
15222 this problem by specifying the ending address of the register stack with
15223 the @code{set rstack_high_address} command. The argument should be an
15224 address, which you probably want to precede with @samp{0x} to specify in
15227 @kindex show rstack_high_address
15228 @item show rstack_high_address
15229 Display the current limit of the register stack, on AMD 29000 family
15237 See the following section.
15242 @cindex stack on Alpha
15243 @cindex stack on MIPS
15244 @cindex Alpha stack
15246 Alpha- and MIPS-based computers use an unusual stack frame, which
15247 sometimes requires @value{GDBN} to search backward in the object code to
15248 find the beginning of a function.
15250 @cindex response time, MIPS debugging
15251 To improve response time (especially for embedded applications, where
15252 @value{GDBN} may be restricted to a slow serial line for this search)
15253 you may want to limit the size of this search, using one of these
15257 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
15258 @item set heuristic-fence-post @var{limit}
15259 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
15260 search for the beginning of a function. A value of @var{0} (the
15261 default) means there is no limit. However, except for @var{0}, the
15262 larger the limit the more bytes @code{heuristic-fence-post} must search
15263 and therefore the longer it takes to run. You should only need to use
15264 this command when debugging a stripped executable.
15266 @item show heuristic-fence-post
15267 Display the current limit.
15271 These commands are available @emph{only} when @value{GDBN} is configured
15272 for debugging programs on Alpha or MIPS processors.
15274 Several MIPS-specific commands are available when debugging MIPS
15278 @item set mips saved-gpreg-size @var{size}
15279 @kindex set mips saved-gpreg-size
15280 @cindex MIPS GP register size on stack
15281 Set the size of MIPS general-purpose registers saved on the stack.
15282 The argument @var{size} can be one of the following:
15286 32-bit GP registers
15288 64-bit GP registers
15290 Use the target's default setting or autodetect the saved size from the
15291 information contained in the executable. This is the default
15294 @item show mips saved-gpreg-size
15295 @kindex show mips saved-gpreg-size
15296 Show the current size of MIPS GP registers on the stack.
15298 @item set mips stack-arg-size @var{size}
15299 @kindex set mips stack-arg-size
15300 @cindex MIPS stack space for arguments
15301 Set the amount of stack space reserved for arguments to functions.
15302 The argument can be one of @code{"32"}, @code{"64"} or @code{"auto"}
15305 @item set mips abi @var{arg}
15306 @kindex set mips abi
15307 @cindex set ABI for MIPS
15308 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
15309 values of @var{arg} are:
15313 The default ABI associated with the current binary (this is the
15324 @item show mips abi
15325 @kindex show mips abi
15326 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
15329 @itemx show mipsfpu
15330 @xref{MIPS Embedded, set mipsfpu}.
15332 @item set mips mask-address @var{arg}
15333 @kindex set mips mask-address
15334 @cindex MIPS addresses, masking
15335 This command determines whether the most-significant 32 bits of 64-bit
15336 MIPS addresses are masked off. The argument @var{arg} can be
15337 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
15338 setting, which lets @value{GDBN} determine the correct value.
15340 @item show mips mask-address
15341 @kindex show mips mask-address
15342 Show whether the upper 32 bits of MIPS addresses are masked off or
15345 @item set remote-mips64-transfers-32bit-regs
15346 @kindex set remote-mips64-transfers-32bit-regs
15347 This command controls compatibility with 64-bit MIPS targets that
15348 transfer data in 32-bit quantities. If you have an old MIPS 64 target
15349 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
15350 and 64 bits for other registers, set this option to @samp{on}.
15352 @item show remote-mips64-transfers-32bit-regs
15353 @kindex show remote-mips64-transfers-32bit-regs
15354 Show the current setting of compatibility with older MIPS 64 targets.
15356 @item set debug mips
15357 @kindex set debug mips
15358 This command turns on and off debugging messages for the MIPS-specific
15359 target code in @value{GDBN}.
15361 @item show debug mips
15362 @kindex show debug mips
15363 Show the current setting of MIPS debugging messages.
15369 @cindex HPPA support
15371 When @value{GDBN} is debugging te HP PA architecture, it provides the
15372 following special commands:
15375 @item set debug hppa
15376 @kindex set debug hppa
15377 THis command determines whether HPPA architecture specific debugging
15378 messages are to be displayed.
15380 @item show debug hppa
15381 Show whether HPPA debugging messages are displayed.
15383 @item maint print unwind @var{address}
15384 @kindex maint print unwind@r{, HPPA}
15385 This command displays the contents of the unwind table entry at the
15386 given @var{address}.
15391 @node Controlling GDB
15392 @chapter Controlling @value{GDBN}
15394 You can alter the way @value{GDBN} interacts with you by using the
15395 @code{set} command. For commands controlling how @value{GDBN} displays
15396 data, see @ref{Print Settings, ,Print settings}. Other settings are
15401 * Editing:: Command editing
15402 * Command History:: Command history
15403 * Screen Size:: Screen size
15404 * Numbers:: Numbers
15405 * ABI:: Configuring the current ABI
15406 * Messages/Warnings:: Optional warnings and messages
15407 * Debugging Output:: Optional messages about internal happenings
15415 @value{GDBN} indicates its readiness to read a command by printing a string
15416 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
15417 can change the prompt string with the @code{set prompt} command. For
15418 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
15419 the prompt in one of the @value{GDBN} sessions so that you can always tell
15420 which one you are talking to.
15422 @emph{Note:} @code{set prompt} does not add a space for you after the
15423 prompt you set. This allows you to set a prompt which ends in a space
15424 or a prompt that does not.
15428 @item set prompt @var{newprompt}
15429 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
15431 @kindex show prompt
15433 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
15437 @section Command editing
15439 @cindex command line editing
15441 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
15442 @sc{gnu} library provides consistent behavior for programs which provide a
15443 command line interface to the user. Advantages are @sc{gnu} Emacs-style
15444 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
15445 substitution, and a storage and recall of command history across
15446 debugging sessions.
15448 You may control the behavior of command line editing in @value{GDBN} with the
15449 command @code{set}.
15452 @kindex set editing
15455 @itemx set editing on
15456 Enable command line editing (enabled by default).
15458 @item set editing off
15459 Disable command line editing.
15461 @kindex show editing
15463 Show whether command line editing is enabled.
15466 @xref{Command Line Editing}, for more details about the Readline
15467 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
15468 encouraged to read that chapter.
15470 @node Command History
15471 @section Command history
15472 @cindex command history
15474 @value{GDBN} can keep track of the commands you type during your
15475 debugging sessions, so that you can be certain of precisely what
15476 happened. Use these commands to manage the @value{GDBN} command
15479 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
15480 package, to provide the history facility. @xref{Using History
15481 Interactively}, for the detailed description of the History library.
15483 To issue a command to @value{GDBN} without affecting certain aspects of
15484 the state which is seen by users, prefix it with @samp{server }. This
15485 means that this command will not affect the command history, nor will it
15486 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
15487 pressed on a line by itself.
15489 @cindex @code{server}, command prefix
15490 The server prefix does not affect the recording of values into the value
15491 history; to print a value without recording it into the value history,
15492 use the @code{output} command instead of the @code{print} command.
15494 Here is the description of @value{GDBN} commands related to command
15498 @cindex history substitution
15499 @cindex history file
15500 @kindex set history filename
15501 @cindex @env{GDBHISTFILE}, environment variable
15502 @item set history filename @var{fname}
15503 Set the name of the @value{GDBN} command history file to @var{fname}.
15504 This is the file where @value{GDBN} reads an initial command history
15505 list, and where it writes the command history from this session when it
15506 exits. You can access this list through history expansion or through
15507 the history command editing characters listed below. This file defaults
15508 to the value of the environment variable @code{GDBHISTFILE}, or to
15509 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
15512 @cindex save command history
15513 @kindex set history save
15514 @item set history save
15515 @itemx set history save on
15516 Record command history in a file, whose name may be specified with the
15517 @code{set history filename} command. By default, this option is disabled.
15519 @item set history save off
15520 Stop recording command history in a file.
15522 @cindex history size
15523 @kindex set history size
15524 @cindex @env{HISTSIZE}, environment variable
15525 @item set history size @var{size}
15526 Set the number of commands which @value{GDBN} keeps in its history list.
15527 This defaults to the value of the environment variable
15528 @code{HISTSIZE}, or to 256 if this variable is not set.
15531 History expansion assigns special meaning to the character @kbd{!}.
15532 @xref{Event Designators}, for more details.
15534 @cindex history expansion, turn on/off
15535 Since @kbd{!} is also the logical not operator in C, history expansion
15536 is off by default. If you decide to enable history expansion with the
15537 @code{set history expansion on} command, you may sometimes need to
15538 follow @kbd{!} (when it is used as logical not, in an expression) with
15539 a space or a tab to prevent it from being expanded. The readline
15540 history facilities do not attempt substitution on the strings
15541 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
15543 The commands to control history expansion are:
15546 @item set history expansion on
15547 @itemx set history expansion
15548 @kindex set history expansion
15549 Enable history expansion. History expansion is off by default.
15551 @item set history expansion off
15552 Disable history expansion.
15555 @kindex show history
15557 @itemx show history filename
15558 @itemx show history save
15559 @itemx show history size
15560 @itemx show history expansion
15561 These commands display the state of the @value{GDBN} history parameters.
15562 @code{show history} by itself displays all four states.
15567 @kindex show commands
15568 @cindex show last commands
15569 @cindex display command history
15570 @item show commands
15571 Display the last ten commands in the command history.
15573 @item show commands @var{n}
15574 Print ten commands centered on command number @var{n}.
15576 @item show commands +
15577 Print ten commands just after the commands last printed.
15581 @section Screen size
15582 @cindex size of screen
15583 @cindex pauses in output
15585 Certain commands to @value{GDBN} may produce large amounts of
15586 information output to the screen. To help you read all of it,
15587 @value{GDBN} pauses and asks you for input at the end of each page of
15588 output. Type @key{RET} when you want to continue the output, or @kbd{q}
15589 to discard the remaining output. Also, the screen width setting
15590 determines when to wrap lines of output. Depending on what is being
15591 printed, @value{GDBN} tries to break the line at a readable place,
15592 rather than simply letting it overflow onto the following line.
15594 Normally @value{GDBN} knows the size of the screen from the terminal
15595 driver software. For example, on Unix @value{GDBN} uses the termcap data base
15596 together with the value of the @code{TERM} environment variable and the
15597 @code{stty rows} and @code{stty cols} settings. If this is not correct,
15598 you can override it with the @code{set height} and @code{set
15605 @kindex show height
15606 @item set height @var{lpp}
15608 @itemx set width @var{cpl}
15610 These @code{set} commands specify a screen height of @var{lpp} lines and
15611 a screen width of @var{cpl} characters. The associated @code{show}
15612 commands display the current settings.
15614 If you specify a height of zero lines, @value{GDBN} does not pause during
15615 output no matter how long the output is. This is useful if output is to a
15616 file or to an editor buffer.
15618 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
15619 from wrapping its output.
15621 @item set pagination on
15622 @itemx set pagination off
15623 @kindex set pagination
15624 Turn the output pagination on or off; the default is on. Turning
15625 pagination off is the alternative to @code{set height 0}.
15627 @item show pagination
15628 @kindex show pagination
15629 Show the current pagination mode.
15634 @cindex number representation
15635 @cindex entering numbers
15637 You can always enter numbers in octal, decimal, or hexadecimal in
15638 @value{GDBN} by the usual conventions: octal numbers begin with
15639 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
15640 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
15641 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
15642 10; likewise, the default display for numbers---when no particular
15643 format is specified---is base 10. You can change the default base for
15644 both input and output with the commands described below.
15647 @kindex set input-radix
15648 @item set input-radix @var{base}
15649 Set the default base for numeric input. Supported choices
15650 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15651 specified either unambiguously or using the current input radix; for
15655 set input-radix 012
15656 set input-radix 10.
15657 set input-radix 0xa
15661 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
15662 leaves the input radix unchanged, no matter what it was, since
15663 @samp{10}, being without any leading or trailing signs of its base, is
15664 interpreted in the current radix. Thus, if the current radix is 16,
15665 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
15668 @kindex set output-radix
15669 @item set output-radix @var{base}
15670 Set the default base for numeric display. Supported choices
15671 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15672 specified either unambiguously or using the current input radix.
15674 @kindex show input-radix
15675 @item show input-radix
15676 Display the current default base for numeric input.
15678 @kindex show output-radix
15679 @item show output-radix
15680 Display the current default base for numeric display.
15682 @item set radix @r{[}@var{base}@r{]}
15686 These commands set and show the default base for both input and output
15687 of numbers. @code{set radix} sets the radix of input and output to
15688 the same base; without an argument, it resets the radix back to its
15689 default value of 10.
15694 @section Configuring the current ABI
15696 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
15697 application automatically. However, sometimes you need to override its
15698 conclusions. Use these commands to manage @value{GDBN}'s view of the
15705 One @value{GDBN} configuration can debug binaries for multiple operating
15706 system targets, either via remote debugging or native emulation.
15707 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
15708 but you can override its conclusion using the @code{set osabi} command.
15709 One example where this is useful is in debugging of binaries which use
15710 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
15711 not have the same identifying marks that the standard C library for your
15716 Show the OS ABI currently in use.
15719 With no argument, show the list of registered available OS ABI's.
15721 @item set osabi @var{abi}
15722 Set the current OS ABI to @var{abi}.
15725 @cindex float promotion
15727 Generally, the way that an argument of type @code{float} is passed to a
15728 function depends on whether the function is prototyped. For a prototyped
15729 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
15730 according to the architecture's convention for @code{float}. For unprototyped
15731 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
15732 @code{double} and then passed.
15734 Unfortunately, some forms of debug information do not reliably indicate whether
15735 a function is prototyped. If @value{GDBN} calls a function that is not marked
15736 as prototyped, it consults @kbd{set coerce-float-to-double}.
15739 @kindex set coerce-float-to-double
15740 @item set coerce-float-to-double
15741 @itemx set coerce-float-to-double on
15742 Arguments of type @code{float} will be promoted to @code{double} when passed
15743 to an unprototyped function. This is the default setting.
15745 @item set coerce-float-to-double off
15746 Arguments of type @code{float} will be passed directly to unprototyped
15749 @kindex show coerce-float-to-double
15750 @item show coerce-float-to-double
15751 Show the current setting of promoting @code{float} to @code{double}.
15755 @kindex show cp-abi
15756 @value{GDBN} needs to know the ABI used for your program's C@t{++}
15757 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
15758 used to build your application. @value{GDBN} only fully supports
15759 programs with a single C@t{++} ABI; if your program contains code using
15760 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
15761 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
15762 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
15763 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
15764 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
15765 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
15770 Show the C@t{++} ABI currently in use.
15773 With no argument, show the list of supported C@t{++} ABI's.
15775 @item set cp-abi @var{abi}
15776 @itemx set cp-abi auto
15777 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
15780 @node Messages/Warnings
15781 @section Optional warnings and messages
15783 @cindex verbose operation
15784 @cindex optional warnings
15785 By default, @value{GDBN} is silent about its inner workings. If you are
15786 running on a slow machine, you may want to use the @code{set verbose}
15787 command. This makes @value{GDBN} tell you when it does a lengthy
15788 internal operation, so you will not think it has crashed.
15790 Currently, the messages controlled by @code{set verbose} are those
15791 which announce that the symbol table for a source file is being read;
15792 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
15795 @kindex set verbose
15796 @item set verbose on
15797 Enables @value{GDBN} output of certain informational messages.
15799 @item set verbose off
15800 Disables @value{GDBN} output of certain informational messages.
15802 @kindex show verbose
15804 Displays whether @code{set verbose} is on or off.
15807 By default, if @value{GDBN} encounters bugs in the symbol table of an
15808 object file, it is silent; but if you are debugging a compiler, you may
15809 find this information useful (@pxref{Symbol Errors, ,Errors reading
15814 @kindex set complaints
15815 @item set complaints @var{limit}
15816 Permits @value{GDBN} to output @var{limit} complaints about each type of
15817 unusual symbols before becoming silent about the problem. Set
15818 @var{limit} to zero to suppress all complaints; set it to a large number
15819 to prevent complaints from being suppressed.
15821 @kindex show complaints
15822 @item show complaints
15823 Displays how many symbol complaints @value{GDBN} is permitted to produce.
15827 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
15828 lot of stupid questions to confirm certain commands. For example, if
15829 you try to run a program which is already running:
15833 The program being debugged has been started already.
15834 Start it from the beginning? (y or n)
15837 If you are willing to unflinchingly face the consequences of your own
15838 commands, you can disable this ``feature'':
15842 @kindex set confirm
15844 @cindex confirmation
15845 @cindex stupid questions
15846 @item set confirm off
15847 Disables confirmation requests.
15849 @item set confirm on
15850 Enables confirmation requests (the default).
15852 @kindex show confirm
15854 Displays state of confirmation requests.
15858 @node Debugging Output
15859 @section Optional messages about internal happenings
15860 @cindex optional debugging messages
15862 @value{GDBN} has commands that enable optional debugging messages from
15863 various @value{GDBN} subsystems; normally these commands are of
15864 interest to @value{GDBN} maintainers, or when reporting a bug. This
15865 section documents those commands.
15868 @kindex set exec-done-display
15869 @item set exec-done-display
15870 Turns on or off the notification of asynchronous commands'
15871 completion. When on, @value{GDBN} will print a message when an
15872 asynchronous command finishes its execution. The default is off.
15873 @kindex show exec-done-display
15874 @item show exec-done-display
15875 Displays the current setting of asynchronous command completion
15878 @cindex gdbarch debugging info
15879 @cindex architecture debugging info
15880 @item set debug arch
15881 Turns on or off display of gdbarch debugging info. The default is off
15883 @item show debug arch
15884 Displays the current state of displaying gdbarch debugging info.
15885 @item set debug aix-thread
15886 @cindex AIX threads
15887 Display debugging messages about inner workings of the AIX thread
15889 @item show debug aix-thread
15890 Show the current state of AIX thread debugging info display.
15891 @item set debug event
15892 @cindex event debugging info
15893 Turns on or off display of @value{GDBN} event debugging info. The
15895 @item show debug event
15896 Displays the current state of displaying @value{GDBN} event debugging
15898 @item set debug expression
15899 @cindex expression debugging info
15900 Turns on or off display of debugging info about @value{GDBN}
15901 expression parsing. The default is off.
15902 @item show debug expression
15903 Displays the current state of displaying debugging info about
15904 @value{GDBN} expression parsing.
15905 @item set debug frame
15906 @cindex frame debugging info
15907 Turns on or off display of @value{GDBN} frame debugging info. The
15909 @item show debug frame
15910 Displays the current state of displaying @value{GDBN} frame debugging
15912 @item set debug infrun
15913 @cindex inferior debugging info
15914 Turns on or off display of @value{GDBN} debugging info for running the inferior.
15915 The default is off. @file{infrun.c} contains GDB's runtime state machine used
15916 for implementing operations such as single-stepping the inferior.
15917 @item show debug infrun
15918 Displays the current state of @value{GDBN} inferior debugging.
15919 @item set debug lin-lwp
15920 @cindex @sc{gnu}/Linux LWP debug messages
15921 @cindex Linux lightweight processes
15922 Turns on or off debugging messages from the Linux LWP debug support.
15923 @item show debug lin-lwp
15924 Show the current state of Linux LWP debugging messages.
15925 @item set debug observer
15926 @cindex observer debugging info
15927 Turns on or off display of @value{GDBN} observer debugging. This
15928 includes info such as the notification of observable events.
15929 @item show debug observer
15930 Displays the current state of observer debugging.
15931 @item set debug overload
15932 @cindex C@t{++} overload debugging info
15933 Turns on or off display of @value{GDBN} C@t{++} overload debugging
15934 info. This includes info such as ranking of functions, etc. The default
15936 @item show debug overload
15937 Displays the current state of displaying @value{GDBN} C@t{++} overload
15939 @cindex packets, reporting on stdout
15940 @cindex serial connections, debugging
15941 @item set debug remote
15942 Turns on or off display of reports on all packets sent back and forth across
15943 the serial line to the remote machine. The info is printed on the
15944 @value{GDBN} standard output stream. The default is off.
15945 @item show debug remote
15946 Displays the state of display of remote packets.
15947 @item set debug serial
15948 Turns on or off display of @value{GDBN} serial debugging info. The
15950 @item show debug serial
15951 Displays the current state of displaying @value{GDBN} serial debugging
15953 @item set debug solib-frv
15954 @cindex FR-V shared-library debugging
15955 Turns on or off debugging messages for FR-V shared-library code.
15956 @item show debug solib-frv
15957 Display the current state of FR-V shared-library code debugging
15959 @item set debug target
15960 @cindex target debugging info
15961 Turns on or off display of @value{GDBN} target debugging info. This info
15962 includes what is going on at the target level of GDB, as it happens. The
15963 default is 0. Set it to 1 to track events, and to 2 to also track the
15964 value of large memory transfers. Changes to this flag do not take effect
15965 until the next time you connect to a target or use the @code{run} command.
15966 @item show debug target
15967 Displays the current state of displaying @value{GDBN} target debugging
15969 @item set debugvarobj
15970 @cindex variable object debugging info
15971 Turns on or off display of @value{GDBN} variable object debugging
15972 info. The default is off.
15973 @item show debugvarobj
15974 Displays the current state of displaying @value{GDBN} variable object
15979 @chapter Canned Sequences of Commands
15981 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
15982 command lists}), @value{GDBN} provides two ways to store sequences of
15983 commands for execution as a unit: user-defined commands and command
15987 * Define:: How to define your own commands
15988 * Hooks:: Hooks for user-defined commands
15989 * Command Files:: How to write scripts of commands to be stored in a file
15990 * Output:: Commands for controlled output
15994 @section User-defined commands
15996 @cindex user-defined command
15997 @cindex arguments, to user-defined commands
15998 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
15999 which you assign a new name as a command. This is done with the
16000 @code{define} command. User commands may accept up to 10 arguments
16001 separated by whitespace. Arguments are accessed within the user command
16002 via @code{$arg0@dots{}$arg9}. A trivial example:
16006 print $arg0 + $arg1 + $arg2
16011 To execute the command use:
16018 This defines the command @code{adder}, which prints the sum of
16019 its three arguments. Note the arguments are text substitutions, so they may
16020 reference variables, use complex expressions, or even perform inferior
16023 @cindex argument count in user-defined commands
16024 @cindex how many arguments (user-defined commands)
16025 In addition, @code{$argc} may be used to find out how many arguments have
16026 been passed. This expands to a number in the range 0@dots{}10.
16031 print $arg0 + $arg1
16034 print $arg0 + $arg1 + $arg2
16042 @item define @var{commandname}
16043 Define a command named @var{commandname}. If there is already a command
16044 by that name, you are asked to confirm that you want to redefine it.
16046 The definition of the command is made up of other @value{GDBN} command lines,
16047 which are given following the @code{define} command. The end of these
16048 commands is marked by a line containing @code{end}.
16051 @kindex end@r{ (user-defined commands)}
16052 @item document @var{commandname}
16053 Document the user-defined command @var{commandname}, so that it can be
16054 accessed by @code{help}. The command @var{commandname} must already be
16055 defined. This command reads lines of documentation just as @code{define}
16056 reads the lines of the command definition, ending with @code{end}.
16057 After the @code{document} command is finished, @code{help} on command
16058 @var{commandname} displays the documentation you have written.
16060 You may use the @code{document} command again to change the
16061 documentation of a command. Redefining the command with @code{define}
16062 does not change the documentation.
16064 @kindex dont-repeat
16065 @cindex don't repeat command
16067 Used inside a user-defined command, this tells @value{GDBN} that this
16068 command should not be repeated when the user hits @key{RET}
16069 (@pxref{Command Syntax, repeat last command}).
16071 @kindex help user-defined
16072 @item help user-defined
16073 List all user-defined commands, with the first line of the documentation
16078 @itemx show user @var{commandname}
16079 Display the @value{GDBN} commands used to define @var{commandname} (but
16080 not its documentation). If no @var{commandname} is given, display the
16081 definitions for all user-defined commands.
16083 @cindex infinite recursion in user-defined commands
16084 @kindex show max-user-call-depth
16085 @kindex set max-user-call-depth
16086 @item show max-user-call-depth
16087 @itemx set max-user-call-depth
16088 The value of @code{max-user-call-depth} controls how many recursion
16089 levels are allowed in user-defined commands before GDB suspects an
16090 infinite recursion and aborts the command.
16093 In addition to the above commands, user-defined commands frequently
16094 use control flow commands, described in @ref{Command Files}.
16096 When user-defined commands are executed, the
16097 commands of the definition are not printed. An error in any command
16098 stops execution of the user-defined command.
16100 If used interactively, commands that would ask for confirmation proceed
16101 without asking when used inside a user-defined command. Many @value{GDBN}
16102 commands that normally print messages to say what they are doing omit the
16103 messages when used in a user-defined command.
16106 @section User-defined command hooks
16107 @cindex command hooks
16108 @cindex hooks, for commands
16109 @cindex hooks, pre-command
16112 You may define @dfn{hooks}, which are a special kind of user-defined
16113 command. Whenever you run the command @samp{foo}, if the user-defined
16114 command @samp{hook-foo} exists, it is executed (with no arguments)
16115 before that command.
16117 @cindex hooks, post-command
16119 A hook may also be defined which is run after the command you executed.
16120 Whenever you run the command @samp{foo}, if the user-defined command
16121 @samp{hookpost-foo} exists, it is executed (with no arguments) after
16122 that command. Post-execution hooks may exist simultaneously with
16123 pre-execution hooks, for the same command.
16125 It is valid for a hook to call the command which it hooks. If this
16126 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
16128 @c It would be nice if hookpost could be passed a parameter indicating
16129 @c if the command it hooks executed properly or not. FIXME!
16131 @kindex stop@r{, a pseudo-command}
16132 In addition, a pseudo-command, @samp{stop} exists. Defining
16133 (@samp{hook-stop}) makes the associated commands execute every time
16134 execution stops in your program: before breakpoint commands are run,
16135 displays are printed, or the stack frame is printed.
16137 For example, to ignore @code{SIGALRM} signals while
16138 single-stepping, but treat them normally during normal execution,
16143 handle SIGALRM nopass
16147 handle SIGALRM pass
16150 define hook-continue
16151 handle SIGLARM pass
16155 As a further example, to hook at the begining and end of the @code{echo}
16156 command, and to add extra text to the beginning and end of the message,
16164 define hookpost-echo
16168 (@value{GDBP}) echo Hello World
16169 <<<---Hello World--->>>
16174 You can define a hook for any single-word command in @value{GDBN}, but
16175 not for command aliases; you should define a hook for the basic command
16176 name, e.g.@: @code{backtrace} rather than @code{bt}.
16177 @c FIXME! So how does Joe User discover whether a command is an alias
16179 If an error occurs during the execution of your hook, execution of
16180 @value{GDBN} commands stops and @value{GDBN} issues a prompt
16181 (before the command that you actually typed had a chance to run).
16183 If you try to define a hook which does not match any known command, you
16184 get a warning from the @code{define} command.
16186 @node Command Files
16187 @section Command files
16189 @cindex command files
16190 @cindex scripting commands
16191 A command file for @value{GDBN} is a text file made of lines that are
16192 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
16193 also be included. An empty line in a command file does nothing; it
16194 does not mean to repeat the last command, as it would from the
16197 You can request the execution of a command file with the @code{source}
16202 @cindex execute commands from a file
16203 @item source @var{filename}
16204 Execute the command file @var{filename}.
16207 The lines in a command file are generally executed sequentially,
16208 unless the order of execution is changed by one of the
16209 @emph{flow-control commands} described below. The commands are not
16210 printed as they are executed. An error in any command terminates
16211 execution of the command file and control is returned to the console.
16213 Commands that would ask for confirmation if used interactively proceed
16214 without asking when used in a command file. Many @value{GDBN} commands that
16215 normally print messages to say what they are doing omit the messages
16216 when called from command files.
16218 @value{GDBN} also accepts command input from standard input. In this
16219 mode, normal output goes to standard output and error output goes to
16220 standard error. Errors in a command file supplied on standard input do
16221 not terminate execution of the command file---execution continues with
16225 gdb < cmds > log 2>&1
16228 (The syntax above will vary depending on the shell used.) This example
16229 will execute commands from the file @file{cmds}. All output and errors
16230 would be directed to @file{log}.
16232 Since commands stored on command files tend to be more general than
16233 commands typed interactively, they frequently need to deal with
16234 complicated situations, such as different or unexpected values of
16235 variables and symbols, changes in how the program being debugged is
16236 built, etc. @value{GDBN} provides a set of flow-control commands to
16237 deal with these complexities. Using these commands, you can write
16238 complex scripts that loop over data structures, execute commands
16239 conditionally, etc.
16246 This command allows to include in your script conditionally executed
16247 commands. The @code{if} command takes a single argument, which is an
16248 expression to evaluate. It is followed by a series of commands that
16249 are executed only if the expression is true (its value is nonzero).
16250 There can then optionally be an @code{else} line, followed by a series
16251 of commands that are only executed if the expression was false. The
16252 end of the list is marked by a line containing @code{end}.
16256 This command allows to write loops. Its syntax is similar to
16257 @code{if}: the command takes a single argument, which is an expression
16258 to evaluate, and must be followed by the commands to execute, one per
16259 line, terminated by an @code{end}. These commands are called the
16260 @dfn{body} of the loop. The commands in the body of @code{while} are
16261 executed repeatedly as long as the expression evaluates to true.
16265 This command exits the @code{while} loop in whose body it is included.
16266 Execution of the script continues after that @code{while}s @code{end}
16269 @kindex loop_continue
16270 @item loop_continue
16271 This command skips the execution of the rest of the body of commands
16272 in the @code{while} loop in whose body it is included. Execution
16273 branches to the beginning of the @code{while} loop, where it evaluates
16274 the controlling expression.
16276 @kindex end@r{ (if/else/while commands)}
16278 Terminate the block of commands that are the body of @code{if},
16279 @code{else}, or @code{while} flow-control commands.
16284 @section Commands for controlled output
16286 During the execution of a command file or a user-defined command, normal
16287 @value{GDBN} output is suppressed; the only output that appears is what is
16288 explicitly printed by the commands in the definition. This section
16289 describes three commands useful for generating exactly the output you
16294 @item echo @var{text}
16295 @c I do not consider backslash-space a standard C escape sequence
16296 @c because it is not in ANSI.
16297 Print @var{text}. Nonprinting characters can be included in
16298 @var{text} using C escape sequences, such as @samp{\n} to print a
16299 newline. @strong{No newline is printed unless you specify one.}
16300 In addition to the standard C escape sequences, a backslash followed
16301 by a space stands for a space. This is useful for displaying a
16302 string with spaces at the beginning or the end, since leading and
16303 trailing spaces are otherwise trimmed from all arguments.
16304 To print @samp{@w{ }and foo =@w{ }}, use the command
16305 @samp{echo \@w{ }and foo = \@w{ }}.
16307 A backslash at the end of @var{text} can be used, as in C, to continue
16308 the command onto subsequent lines. For example,
16311 echo This is some text\n\
16312 which is continued\n\
16313 onto several lines.\n
16316 produces the same output as
16319 echo This is some text\n
16320 echo which is continued\n
16321 echo onto several lines.\n
16325 @item output @var{expression}
16326 Print the value of @var{expression} and nothing but that value: no
16327 newlines, no @samp{$@var{nn} = }. The value is not entered in the
16328 value history either. @xref{Expressions, ,Expressions}, for more information
16331 @item output/@var{fmt} @var{expression}
16332 Print the value of @var{expression} in format @var{fmt}. You can use
16333 the same formats as for @code{print}. @xref{Output Formats,,Output
16334 formats}, for more information.
16337 @item printf @var{string}, @var{expressions}@dots{}
16338 Print the values of the @var{expressions} under the control of
16339 @var{string}. The @var{expressions} are separated by commas and may be
16340 either numbers or pointers. Their values are printed as specified by
16341 @var{string}, exactly as if your program were to execute the C
16343 @c FIXME: the above implies that at least all ANSI C formats are
16344 @c supported, but it isn't true: %E and %G don't work (or so it seems).
16345 @c Either this is a bug, or the manual should document what formats are
16349 printf (@var{string}, @var{expressions}@dots{});
16352 For example, you can print two values in hex like this:
16355 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
16358 The only backslash-escape sequences that you can use in the format
16359 string are the simple ones that consist of backslash followed by a
16364 @chapter Command Interpreters
16365 @cindex command interpreters
16367 @value{GDBN} supports multiple command interpreters, and some command
16368 infrastructure to allow users or user interface writers to switch
16369 between interpreters or run commands in other interpreters.
16371 @value{GDBN} currently supports two command interpreters, the console
16372 interpreter (sometimes called the command-line interpreter or @sc{cli})
16373 and the machine interface interpreter (or @sc{gdb/mi}). This manual
16374 describes both of these interfaces in great detail.
16376 By default, @value{GDBN} will start with the console interpreter.
16377 However, the user may choose to start @value{GDBN} with another
16378 interpreter by specifying the @option{-i} or @option{--interpreter}
16379 startup options. Defined interpreters include:
16383 @cindex console interpreter
16384 The traditional console or command-line interpreter. This is the most often
16385 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
16386 @value{GDBN} will use this interpreter.
16389 @cindex mi interpreter
16390 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
16391 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
16392 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
16396 @cindex mi2 interpreter
16397 The current @sc{gdb/mi} interface.
16400 @cindex mi1 interpreter
16401 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
16405 @cindex invoke another interpreter
16406 The interpreter being used by @value{GDBN} may not be dynamically
16407 switched at runtime. Although possible, this could lead to a very
16408 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
16409 enters the command "interpreter-set console" in a console view,
16410 @value{GDBN} would switch to using the console interpreter, rendering
16411 the IDE inoperable!
16413 @kindex interpreter-exec
16414 Although you may only choose a single interpreter at startup, you may execute
16415 commands in any interpreter from the current interpreter using the appropriate
16416 command. If you are running the console interpreter, simply use the
16417 @code{interpreter-exec} command:
16420 interpreter-exec mi "-data-list-register-names"
16423 @sc{gdb/mi} has a similar command, although it is only available in versions of
16424 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
16427 @chapter @value{GDBN} Text User Interface
16429 @cindex Text User Interface
16432 * TUI Overview:: TUI overview
16433 * TUI Keys:: TUI key bindings
16434 * TUI Single Key Mode:: TUI single key mode
16435 * TUI Commands:: TUI specific commands
16436 * TUI Configuration:: TUI configuration variables
16439 The @value{GDBN} Text User Interface, TUI in short, is a terminal
16440 interface which uses the @code{curses} library to show the source
16441 file, the assembly output, the program registers and @value{GDBN}
16442 commands in separate text windows.
16444 The TUI is enabled by invoking @value{GDBN} using either
16446 @samp{gdbtui} or @samp{gdb -tui}.
16449 @section TUI overview
16451 The TUI has two display modes that can be switched while
16456 A curses (or TUI) mode in which it displays several text
16457 windows on the terminal.
16460 A standard mode which corresponds to the @value{GDBN} configured without
16464 In the TUI mode, @value{GDBN} can display several text window
16469 This window is the @value{GDBN} command window with the @value{GDBN}
16470 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
16471 managed using readline but through the TUI. The @emph{command}
16472 window is always visible.
16475 The source window shows the source file of the program. The current
16476 line as well as active breakpoints are displayed in this window.
16479 The assembly window shows the disassembly output of the program.
16482 This window shows the processor registers. It detects when
16483 a register is changed and when this is the case, registers that have
16484 changed are highlighted.
16488 The source and assembly windows show the current program position
16489 by highlighting the current line and marking them with the @samp{>} marker.
16490 Breakpoints are also indicated with two markers. A first one
16491 indicates the breakpoint type:
16495 Breakpoint which was hit at least once.
16498 Breakpoint which was never hit.
16501 Hardware breakpoint which was hit at least once.
16504 Hardware breakpoint which was never hit.
16508 The second marker indicates whether the breakpoint is enabled or not:
16512 Breakpoint is enabled.
16515 Breakpoint is disabled.
16519 The source, assembly and register windows are attached to the thread
16520 and the frame position. They are updated when the current thread
16521 changes, when the frame changes or when the program counter changes.
16522 These three windows are arranged by the TUI according to several
16523 layouts. The layout defines which of these three windows are visible.
16524 The following layouts are available:
16534 source and assembly
16537 source and registers
16540 assembly and registers
16544 On top of the command window a status line gives various information
16545 concerning the current process begin debugged. The status line is
16546 updated when the information it shows changes. The following fields
16551 Indicates the current gdb target
16552 (@pxref{Targets, ,Specifying a Debugging Target}).
16555 Gives information about the current process or thread number.
16556 When no process is being debugged, this field is set to @code{No process}.
16559 Gives the current function name for the selected frame.
16560 The name is demangled if demangling is turned on (@pxref{Print Settings}).
16561 When there is no symbol corresponding to the current program counter
16562 the string @code{??} is displayed.
16565 Indicates the current line number for the selected frame.
16566 When the current line number is not known the string @code{??} is displayed.
16569 Indicates the current program counter address.
16574 @section TUI Key Bindings
16575 @cindex TUI key bindings
16577 The TUI installs several key bindings in the readline keymaps
16578 (@pxref{Command Line Editing}).
16579 They allow to leave or enter in the TUI mode or they operate
16580 directly on the TUI layout and windows. The TUI also provides
16581 a @emph{SingleKey} keymap which binds several keys directly to
16582 @value{GDBN} commands. The following key bindings
16583 are installed for both TUI mode and the @value{GDBN} standard mode.
16592 Enter or leave the TUI mode. When the TUI mode is left,
16593 the curses window management is left and @value{GDBN} operates using
16594 its standard mode writing on the terminal directly. When the TUI
16595 mode is entered, the control is given back to the curses windows.
16596 The screen is then refreshed.
16600 Use a TUI layout with only one window. The layout will
16601 either be @samp{source} or @samp{assembly}. When the TUI mode
16602 is not active, it will switch to the TUI mode.
16604 Think of this key binding as the Emacs @kbd{C-x 1} binding.
16608 Use a TUI layout with at least two windows. When the current
16609 layout shows already two windows, a next layout with two windows is used.
16610 When a new layout is chosen, one window will always be common to the
16611 previous layout and the new one.
16613 Think of it as the Emacs @kbd{C-x 2} binding.
16617 Change the active window. The TUI associates several key bindings
16618 (like scrolling and arrow keys) to the active window. This command
16619 gives the focus to the next TUI window.
16621 Think of it as the Emacs @kbd{C-x o} binding.
16625 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
16626 (@pxref{TUI Single Key Mode}).
16630 The following key bindings are handled only by the TUI mode:
16635 Scroll the active window one page up.
16639 Scroll the active window one page down.
16643 Scroll the active window one line up.
16647 Scroll the active window one line down.
16651 Scroll the active window one column left.
16655 Scroll the active window one column right.
16659 Refresh the screen.
16663 In the TUI mode, the arrow keys are used by the active window
16664 for scrolling. This means they are available for readline when the
16665 active window is the command window. When the command window
16666 does not have the focus, it is necessary to use other readline
16667 key bindings such as @key{C-p}, @key{C-n}, @key{C-b} and @key{C-f}.
16669 @node TUI Single Key Mode
16670 @section TUI Single Key Mode
16671 @cindex TUI single key mode
16673 The TUI provides a @emph{SingleKey} mode in which it installs a particular
16674 key binding in the readline keymaps to connect single keys to
16678 @kindex c @r{(SingleKey TUI key)}
16682 @kindex d @r{(SingleKey TUI key)}
16686 @kindex f @r{(SingleKey TUI key)}
16690 @kindex n @r{(SingleKey TUI key)}
16694 @kindex q @r{(SingleKey TUI key)}
16696 exit the @emph{SingleKey} mode.
16698 @kindex r @r{(SingleKey TUI key)}
16702 @kindex s @r{(SingleKey TUI key)}
16706 @kindex u @r{(SingleKey TUI key)}
16710 @kindex v @r{(SingleKey TUI key)}
16714 @kindex w @r{(SingleKey TUI key)}
16720 Other keys temporarily switch to the @value{GDBN} command prompt.
16721 The key that was pressed is inserted in the editing buffer so that
16722 it is possible to type most @value{GDBN} commands without interaction
16723 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
16724 @emph{SingleKey} mode is restored. The only way to permanently leave
16725 this mode is by hitting @key{q} or @samp{@key{C-x} @key{s}}.
16729 @section TUI specific commands
16730 @cindex TUI commands
16732 The TUI has specific commands to control the text windows.
16733 These commands are always available, that is they do not depend on
16734 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
16735 is in the standard mode, using these commands will automatically switch
16741 List and give the size of all displayed windows.
16745 Display the next layout.
16748 Display the previous layout.
16751 Display the source window only.
16754 Display the assembly window only.
16757 Display the source and assembly window.
16760 Display the register window together with the source or assembly window.
16762 @item focus next | prev | src | asm | regs | split
16764 Set the focus to the named window.
16765 This command allows to change the active window so that scrolling keys
16766 can be affected to another window.
16770 Refresh the screen. This is similar to using @key{C-L} key.
16772 @item tui reg float
16774 Show the floating point registers in the register window.
16776 @item tui reg general
16777 Show the general registers in the register window.
16780 Show the next register group. The list of register groups as well as
16781 their order is target specific. The predefined register groups are the
16782 following: @code{general}, @code{float}, @code{system}, @code{vector},
16783 @code{all}, @code{save}, @code{restore}.
16785 @item tui reg system
16786 Show the system registers in the register window.
16790 Update the source window and the current execution point.
16792 @item winheight @var{name} +@var{count}
16793 @itemx winheight @var{name} -@var{count}
16795 Change the height of the window @var{name} by @var{count}
16796 lines. Positive counts increase the height, while negative counts
16800 @kindex tabset @var{nchars}
16801 Set the width of tab stops to be @var{nchars} characters.
16805 @node TUI Configuration
16806 @section TUI configuration variables
16807 @cindex TUI configuration variables
16809 The TUI has several configuration variables that control the
16810 appearance of windows on the terminal.
16813 @item set tui border-kind @var{kind}
16814 @kindex set tui border-kind
16815 Select the border appearance for the source, assembly and register windows.
16816 The possible values are the following:
16819 Use a space character to draw the border.
16822 Use ascii characters + - and | to draw the border.
16825 Use the Alternate Character Set to draw the border. The border is
16826 drawn using character line graphics if the terminal supports them.
16830 @item set tui active-border-mode @var{mode}
16831 @kindex set tui active-border-mode
16832 Select the attributes to display the border of the active window.
16833 The possible values are @code{normal}, @code{standout}, @code{reverse},
16834 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
16836 @item set tui border-mode @var{mode}
16837 @kindex set tui border-mode
16838 Select the attributes to display the border of other windows.
16839 The @var{mode} can be one of the following:
16842 Use normal attributes to display the border.
16848 Use reverse video mode.
16851 Use half bright mode.
16853 @item half-standout
16854 Use half bright and standout mode.
16857 Use extra bright or bold mode.
16859 @item bold-standout
16860 Use extra bright or bold and standout mode.
16867 @chapter Using @value{GDBN} under @sc{gnu} Emacs
16870 @cindex @sc{gnu} Emacs
16871 A special interface allows you to use @sc{gnu} Emacs to view (and
16872 edit) the source files for the program you are debugging with
16875 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
16876 executable file you want to debug as an argument. This command starts
16877 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
16878 created Emacs buffer.
16879 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
16881 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
16886 All ``terminal'' input and output goes through the Emacs buffer.
16889 This applies both to @value{GDBN} commands and their output, and to the input
16890 and output done by the program you are debugging.
16892 This is useful because it means that you can copy the text of previous
16893 commands and input them again; you can even use parts of the output
16896 All the facilities of Emacs' Shell mode are available for interacting
16897 with your program. In particular, you can send signals the usual
16898 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
16903 @value{GDBN} displays source code through Emacs.
16906 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
16907 source file for that frame and puts an arrow (@samp{=>}) at the
16908 left margin of the current line. Emacs uses a separate buffer for
16909 source display, and splits the screen to show both your @value{GDBN} session
16912 Explicit @value{GDBN} @code{list} or search commands still produce output as
16913 usual, but you probably have no reason to use them from Emacs.
16915 If you specify an absolute file name when prompted for the @kbd{M-x
16916 gdb} argument, then Emacs sets your current working directory to where
16917 your program resides. If you only specify the file name, then Emacs
16918 sets your current working directory to to the directory associated
16919 with the previous buffer. In this case, @value{GDBN} may find your
16920 program by searching your environment's @code{PATH} variable, but on
16921 some operating systems it might not find the source. So, although the
16922 @value{GDBN} input and output session proceeds normally, the auxiliary
16923 buffer does not display the current source and line of execution.
16925 The initial working directory of @value{GDBN} is printed on the top
16926 line of the @value{GDBN} I/O buffer and this serves as a default for
16927 the commands that specify files for @value{GDBN} to operate
16928 on. @xref{Files, ,Commands to specify files}.
16930 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
16931 need to call @value{GDBN} by a different name (for example, if you
16932 keep several configurations around, with different names) you can
16933 customize the Emacs variable @code{gud-gdb-command-name} to run the
16936 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
16937 addition to the standard Shell mode commands:
16941 Describe the features of Emacs' @value{GDBN} Mode.
16944 Execute to another source line, like the @value{GDBN} @code{step} command; also
16945 update the display window to show the current file and location.
16948 Execute to next source line in this function, skipping all function
16949 calls, like the @value{GDBN} @code{next} command. Then update the display window
16950 to show the current file and location.
16953 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
16954 display window accordingly.
16957 Execute until exit from the selected stack frame, like the @value{GDBN}
16958 @code{finish} command.
16961 Continue execution of your program, like the @value{GDBN} @code{continue}
16965 Go up the number of frames indicated by the numeric argument
16966 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
16967 like the @value{GDBN} @code{up} command.
16970 Go down the number of frames indicated by the numeric argument, like the
16971 @value{GDBN} @code{down} command.
16974 In any source file, the Emacs command @kbd{C-x SPC} (@code{gud-break})
16975 tells @value{GDBN} to set a breakpoint on the source line point is on.
16977 If you type @kbd{M-x speedbar}, then Emacs displays a separate frame which
16978 shows a backtrace when the @value{GDBN} I/O buffer is current. Move
16979 point to any frame in the stack and type @key{RET} to make it become the
16980 current frame and display the associated source in the source buffer.
16981 Alternatively, click @kbd{Mouse-2} to make the selected frame become the
16984 If you accidentally delete the source-display buffer, an easy way to get
16985 it back is to type the command @code{f} in the @value{GDBN} buffer, to
16986 request a frame display; when you run under Emacs, this recreates
16987 the source buffer if necessary to show you the context of the current
16990 The source files displayed in Emacs are in ordinary Emacs buffers
16991 which are visiting the source files in the usual way. You can edit
16992 the files with these buffers if you wish; but keep in mind that @value{GDBN}
16993 communicates with Emacs in terms of line numbers. If you add or
16994 delete lines from the text, the line numbers that @value{GDBN} knows cease
16995 to correspond properly with the code.
16997 The description given here is for GNU Emacs version 21.3 and a more
16998 detailed description of its interaction with @value{GDBN} is given in
16999 the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu} Emacs Manual}).
17001 @c The following dropped because Epoch is nonstandard. Reactivate
17002 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
17004 @kindex Emacs Epoch environment
17008 Version 18 of @sc{gnu} Emacs has a built-in window system
17009 called the @code{epoch}
17010 environment. Users of this environment can use a new command,
17011 @code{inspect} which performs identically to @code{print} except that
17012 each value is printed in its own window.
17017 @chapter The @sc{gdb/mi} Interface
17019 @unnumberedsec Function and Purpose
17021 @cindex @sc{gdb/mi}, its purpose
17022 @sc{gdb/mi} is a line based machine oriented text interface to
17023 @value{GDBN} and is activated by specifying using the
17024 @option{--interpreter} command line option (@pxref{Mode Options}). It
17025 is specifically intended to support the development of systems which
17026 use the debugger as just one small component of a larger system.
17028 This chapter is a specification of the @sc{gdb/mi} interface. It is written
17029 in the form of a reference manual.
17031 Note that @sc{gdb/mi} is still under construction, so some of the
17032 features described below are incomplete and subject to change.
17034 @unnumberedsec Notation and Terminology
17036 @cindex notational conventions, for @sc{gdb/mi}
17037 This chapter uses the following notation:
17041 @code{|} separates two alternatives.
17044 @code{[ @var{something} ]} indicates that @var{something} is optional:
17045 it may or may not be given.
17048 @code{( @var{group} )*} means that @var{group} inside the parentheses
17049 may repeat zero or more times.
17052 @code{( @var{group} )+} means that @var{group} inside the parentheses
17053 may repeat one or more times.
17056 @code{"@var{string}"} means a literal @var{string}.
17060 @heading Dependencies
17063 @heading Acknowledgments
17065 In alphabetic order: Andrew Cagney, Fernando Nasser, Stan Shebs and
17069 * GDB/MI Command Syntax::
17070 * GDB/MI Compatibility with CLI::
17071 * GDB/MI Output Records::
17072 * GDB/MI Command Description Format::
17073 * GDB/MI Breakpoint Table Commands::
17074 * GDB/MI Data Manipulation::
17075 * GDB/MI Program Control::
17076 * GDB/MI Miscellaneous Commands::
17078 * GDB/MI Kod Commands::
17079 * GDB/MI Memory Overlay Commands::
17080 * GDB/MI Signal Handling Commands::
17082 * GDB/MI Stack Manipulation::
17083 * GDB/MI Symbol Query::
17084 * GDB/MI Target Manipulation::
17085 * GDB/MI Thread Commands::
17086 * GDB/MI Tracepoint Commands::
17087 * GDB/MI Variable Objects::
17090 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17091 @node GDB/MI Command Syntax
17092 @section @sc{gdb/mi} Command Syntax
17095 * GDB/MI Input Syntax::
17096 * GDB/MI Output Syntax::
17097 * GDB/MI Simple Examples::
17100 @node GDB/MI Input Syntax
17101 @subsection @sc{gdb/mi} Input Syntax
17103 @cindex input syntax for @sc{gdb/mi}
17104 @cindex @sc{gdb/mi}, input syntax
17106 @item @var{command} @expansion{}
17107 @code{@var{cli-command} | @var{mi-command}}
17109 @item @var{cli-command} @expansion{}
17110 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
17111 @var{cli-command} is any existing @value{GDBN} CLI command.
17113 @item @var{mi-command} @expansion{}
17114 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
17115 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
17117 @item @var{token} @expansion{}
17118 "any sequence of digits"
17120 @item @var{option} @expansion{}
17121 @code{"-" @var{parameter} [ " " @var{parameter} ]}
17123 @item @var{parameter} @expansion{}
17124 @code{@var{non-blank-sequence} | @var{c-string}}
17126 @item @var{operation} @expansion{}
17127 @emph{any of the operations described in this chapter}
17129 @item @var{non-blank-sequence} @expansion{}
17130 @emph{anything, provided it doesn't contain special characters such as
17131 "-", @var{nl}, """ and of course " "}
17133 @item @var{c-string} @expansion{}
17134 @code{""" @var{seven-bit-iso-c-string-content} """}
17136 @item @var{nl} @expansion{}
17145 The CLI commands are still handled by the @sc{mi} interpreter; their
17146 output is described below.
17149 The @code{@var{token}}, when present, is passed back when the command
17153 Some @sc{mi} commands accept optional arguments as part of the parameter
17154 list. Each option is identified by a leading @samp{-} (dash) and may be
17155 followed by an optional argument parameter. Options occur first in the
17156 parameter list and can be delimited from normal parameters using
17157 @samp{--} (this is useful when some parameters begin with a dash).
17164 We want easy access to the existing CLI syntax (for debugging).
17167 We want it to be easy to spot a @sc{mi} operation.
17170 @node GDB/MI Output Syntax
17171 @subsection @sc{gdb/mi} Output Syntax
17173 @cindex output syntax of @sc{gdb/mi}
17174 @cindex @sc{gdb/mi}, output syntax
17175 The output from @sc{gdb/mi} consists of zero or more out-of-band records
17176 followed, optionally, by a single result record. This result record
17177 is for the most recent command. The sequence of output records is
17178 terminated by @samp{(@value{GDBP})}.
17180 If an input command was prefixed with a @code{@var{token}} then the
17181 corresponding output for that command will also be prefixed by that same
17185 @item @var{output} @expansion{}
17186 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(@value{GDBP})" @var{nl}}
17188 @item @var{result-record} @expansion{}
17189 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
17191 @item @var{out-of-band-record} @expansion{}
17192 @code{@var{async-record} | @var{stream-record}}
17194 @item @var{async-record} @expansion{}
17195 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
17197 @item @var{exec-async-output} @expansion{}
17198 @code{[ @var{token} ] "*" @var{async-output}}
17200 @item @var{status-async-output} @expansion{}
17201 @code{[ @var{token} ] "+" @var{async-output}}
17203 @item @var{notify-async-output} @expansion{}
17204 @code{[ @var{token} ] "=" @var{async-output}}
17206 @item @var{async-output} @expansion{}
17207 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
17209 @item @var{result-class} @expansion{}
17210 @code{"done" | "running" | "connected" | "error" | "exit"}
17212 @item @var{async-class} @expansion{}
17213 @code{"stopped" | @var{others}} (where @var{others} will be added
17214 depending on the needs---this is still in development).
17216 @item @var{result} @expansion{}
17217 @code{ @var{variable} "=" @var{value}}
17219 @item @var{variable} @expansion{}
17220 @code{ @var{string} }
17222 @item @var{value} @expansion{}
17223 @code{ @var{const} | @var{tuple} | @var{list} }
17225 @item @var{const} @expansion{}
17226 @code{@var{c-string}}
17228 @item @var{tuple} @expansion{}
17229 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
17231 @item @var{list} @expansion{}
17232 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
17233 @var{result} ( "," @var{result} )* "]" }
17235 @item @var{stream-record} @expansion{}
17236 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
17238 @item @var{console-stream-output} @expansion{}
17239 @code{"~" @var{c-string}}
17241 @item @var{target-stream-output} @expansion{}
17242 @code{"@@" @var{c-string}}
17244 @item @var{log-stream-output} @expansion{}
17245 @code{"&" @var{c-string}}
17247 @item @var{nl} @expansion{}
17250 @item @var{token} @expansion{}
17251 @emph{any sequence of digits}.
17259 All output sequences end in a single line containing a period.
17262 The @code{@var{token}} is from the corresponding request. If an execution
17263 command is interrupted by the @samp{-exec-interrupt} command, the
17264 @var{token} associated with the @samp{*stopped} message is the one of the
17265 original execution command, not the one of the interrupt command.
17268 @cindex status output in @sc{gdb/mi}
17269 @var{status-async-output} contains on-going status information about the
17270 progress of a slow operation. It can be discarded. All status output is
17271 prefixed by @samp{+}.
17274 @cindex async output in @sc{gdb/mi}
17275 @var{exec-async-output} contains asynchronous state change on the target
17276 (stopped, started, disappeared). All async output is prefixed by
17280 @cindex notify output in @sc{gdb/mi}
17281 @var{notify-async-output} contains supplementary information that the
17282 client should handle (e.g., a new breakpoint information). All notify
17283 output is prefixed by @samp{=}.
17286 @cindex console output in @sc{gdb/mi}
17287 @var{console-stream-output} is output that should be displayed as is in the
17288 console. It is the textual response to a CLI command. All the console
17289 output is prefixed by @samp{~}.
17292 @cindex target output in @sc{gdb/mi}
17293 @var{target-stream-output} is the output produced by the target program.
17294 All the target output is prefixed by @samp{@@}.
17297 @cindex log output in @sc{gdb/mi}
17298 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
17299 instance messages that should be displayed as part of an error log. All
17300 the log output is prefixed by @samp{&}.
17303 @cindex list output in @sc{gdb/mi}
17304 New @sc{gdb/mi} commands should only output @var{lists} containing
17310 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
17311 details about the various output records.
17313 @node GDB/MI Simple Examples
17314 @subsection Simple Examples of @sc{gdb/mi} Interaction
17315 @cindex @sc{gdb/mi}, simple examples
17317 This subsection presents several simple examples of interaction using
17318 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
17319 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
17320 the output received from @sc{gdb/mi}.
17322 @subsubheading Target Stop
17323 @c Ummm... There is no "-stop" command. This assumes async, no?
17324 Here's an example of stopping the inferior process:
17335 <- *stop,reason="stop",address="0x123",source="a.c:123"
17339 @subsubheading Simple CLI Command
17341 Here's an example of a simple CLI command being passed through
17342 @sc{gdb/mi} and on to the CLI.
17352 @subsubheading Command With Side Effects
17355 -> -symbol-file xyz.exe
17356 <- *breakpoint,nr="3",address="0x123",source="a.c:123"
17360 @subsubheading A Bad Command
17362 Here's what happens if you pass a non-existent command:
17366 <- ^error,msg="Undefined MI command: rubbish"
17370 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17371 @node GDB/MI Compatibility with CLI
17372 @section @sc{gdb/mi} Compatibility with CLI
17374 @cindex compatibility, @sc{gdb/mi} and CLI
17375 @cindex @sc{gdb/mi}, compatibility with CLI
17376 To help users familiar with @value{GDBN}'s existing CLI interface, @sc{gdb/mi}
17377 accepts existing CLI commands. As specified by the syntax, such
17378 commands can be directly entered into the @sc{gdb/mi} interface and @value{GDBN} will
17381 This mechanism is provided as an aid to developers of @sc{gdb/mi}
17382 clients and not as a reliable interface into the CLI. Since the command
17383 is being interpreteted in an environment that assumes @sc{gdb/mi}
17384 behaviour, the exact output of such commands is likely to end up being
17385 an un-supported hybrid of @sc{gdb/mi} and CLI output.
17387 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17388 @node GDB/MI Output Records
17389 @section @sc{gdb/mi} Output Records
17392 * GDB/MI Result Records::
17393 * GDB/MI Stream Records::
17394 * GDB/MI Out-of-band Records::
17397 @node GDB/MI Result Records
17398 @subsection @sc{gdb/mi} Result Records
17400 @cindex result records in @sc{gdb/mi}
17401 @cindex @sc{gdb/mi}, result records
17402 In addition to a number of out-of-band notifications, the response to a
17403 @sc{gdb/mi} command includes one of the following result indications:
17407 @item "^done" [ "," @var{results} ]
17408 The synchronous operation was successful, @code{@var{results}} are the return
17413 @c Is this one correct? Should it be an out-of-band notification?
17414 The asynchronous operation was successfully started. The target is
17417 @item "^error" "," @var{c-string}
17419 The operation failed. The @code{@var{c-string}} contains the corresponding
17423 @node GDB/MI Stream Records
17424 @subsection @sc{gdb/mi} Stream Records
17426 @cindex @sc{gdb/mi}, stream records
17427 @cindex stream records in @sc{gdb/mi}
17428 @value{GDBN} internally maintains a number of output streams: the console, the
17429 target, and the log. The output intended for each of these streams is
17430 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
17432 Each stream record begins with a unique @dfn{prefix character} which
17433 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
17434 Syntax}). In addition to the prefix, each stream record contains a
17435 @code{@var{string-output}}. This is either raw text (with an implicit new
17436 line) or a quoted C string (which does not contain an implicit newline).
17439 @item "~" @var{string-output}
17440 The console output stream contains text that should be displayed in the
17441 CLI console window. It contains the textual responses to CLI commands.
17443 @item "@@" @var{string-output}
17444 The target output stream contains any textual output from the running
17447 @item "&" @var{string-output}
17448 The log stream contains debugging messages being produced by @value{GDBN}'s
17452 @node GDB/MI Out-of-band Records
17453 @subsection @sc{gdb/mi} Out-of-band Records
17455 @cindex out-of-band records in @sc{gdb/mi}
17456 @cindex @sc{gdb/mi}, out-of-band records
17457 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
17458 additional changes that have occurred. Those changes can either be a
17459 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
17460 target activity (e.g., target stopped).
17462 The following is a preliminary list of possible out-of-band records.
17463 In particular, the @var{exec-async-output} records.
17466 @item *stopped,reason="@var{reason}"
17469 @var{reason} can be one of the following:
17472 @item breakpoint-hit
17473 A breakpoint was reached.
17474 @item watchpoint-trigger
17475 A watchpoint was triggered.
17476 @item read-watchpoint-trigger
17477 A read watchpoint was triggered.
17478 @item access-watchpoint-trigger
17479 An access watchpoint was triggered.
17480 @item function-finished
17481 An -exec-finish or similar CLI command was accomplished.
17482 @item location-reached
17483 An -exec-until or similar CLI command was accomplished.
17484 @item watchpoint-scope
17485 A watchpoint has gone out of scope.
17486 @item end-stepping-range
17487 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
17488 similar CLI command was accomplished.
17489 @item exited-signalled
17490 The inferior exited because of a signal.
17492 The inferior exited.
17493 @item exited-normally
17494 The inferior exited normally.
17495 @item signal-received
17496 A signal was received by the inferior.
17500 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17501 @node GDB/MI Command Description Format
17502 @section @sc{gdb/mi} Command Description Format
17504 The remaining sections describe blocks of commands. Each block of
17505 commands is laid out in a fashion similar to this section.
17507 Note the the line breaks shown in the examples are here only for
17508 readability. They don't appear in the real output.
17509 Also note that the commands with a non-available example (N.A.@:) are
17510 not yet implemented.
17512 @subheading Motivation
17514 The motivation for this collection of commands.
17516 @subheading Introduction
17518 A brief introduction to this collection of commands as a whole.
17520 @subheading Commands
17522 For each command in the block, the following is described:
17524 @subsubheading Synopsis
17527 -command @var{args}@dots{}
17530 @subsubheading Result
17532 @subsubheading @value{GDBN} Command
17534 The corresponding @value{GDBN} CLI command(s), if any.
17536 @subsubheading Example
17538 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17539 @node GDB/MI Breakpoint Table Commands
17540 @section @sc{gdb/mi} Breakpoint table commands
17542 @cindex breakpoint commands for @sc{gdb/mi}
17543 @cindex @sc{gdb/mi}, breakpoint commands
17544 This section documents @sc{gdb/mi} commands for manipulating
17547 @subheading The @code{-break-after} Command
17548 @findex -break-after
17550 @subsubheading Synopsis
17553 -break-after @var{number} @var{count}
17556 The breakpoint number @var{number} is not in effect until it has been
17557 hit @var{count} times. To see how this is reflected in the output of
17558 the @samp{-break-list} command, see the description of the
17559 @samp{-break-list} command below.
17561 @subsubheading @value{GDBN} Command
17563 The corresponding @value{GDBN} command is @samp{ignore}.
17565 @subsubheading Example
17570 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",line="5"@}
17577 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17578 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17579 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17580 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17581 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17582 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17583 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17584 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17585 addr="0x000100d0",func="main",file="hello.c",line="5",times="0",
17591 @subheading The @code{-break-catch} Command
17592 @findex -break-catch
17594 @subheading The @code{-break-commands} Command
17595 @findex -break-commands
17599 @subheading The @code{-break-condition} Command
17600 @findex -break-condition
17602 @subsubheading Synopsis
17605 -break-condition @var{number} @var{expr}
17608 Breakpoint @var{number} will stop the program only if the condition in
17609 @var{expr} is true. The condition becomes part of the
17610 @samp{-break-list} output (see the description of the @samp{-break-list}
17613 @subsubheading @value{GDBN} Command
17615 The corresponding @value{GDBN} command is @samp{condition}.
17617 @subsubheading Example
17621 -break-condition 1 1
17625 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17626 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17627 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17628 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17629 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17630 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17631 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17632 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17633 addr="0x000100d0",func="main",file="hello.c",line="5",cond="1",
17634 times="0",ignore="3"@}]@}
17638 @subheading The @code{-break-delete} Command
17639 @findex -break-delete
17641 @subsubheading Synopsis
17644 -break-delete ( @var{breakpoint} )+
17647 Delete the breakpoint(s) whose number(s) are specified in the argument
17648 list. This is obviously reflected in the breakpoint list.
17650 @subsubheading @value{GDBN} command
17652 The corresponding @value{GDBN} command is @samp{delete}.
17654 @subsubheading Example
17662 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
17663 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17664 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17665 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17666 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17667 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17668 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17673 @subheading The @code{-break-disable} Command
17674 @findex -break-disable
17676 @subsubheading Synopsis
17679 -break-disable ( @var{breakpoint} )+
17682 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
17683 break list is now set to @samp{n} for the named @var{breakpoint}(s).
17685 @subsubheading @value{GDBN} Command
17687 The corresponding @value{GDBN} command is @samp{disable}.
17689 @subsubheading Example
17697 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17698 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17699 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17700 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17701 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17702 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17703 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17704 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
17705 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
17709 @subheading The @code{-break-enable} Command
17710 @findex -break-enable
17712 @subsubheading Synopsis
17715 -break-enable ( @var{breakpoint} )+
17718 Enable (previously disabled) @var{breakpoint}(s).
17720 @subsubheading @value{GDBN} Command
17722 The corresponding @value{GDBN} command is @samp{enable}.
17724 @subsubheading Example
17732 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17733 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17734 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17735 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17736 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17737 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17738 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17739 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
17740 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
17744 @subheading The @code{-break-info} Command
17745 @findex -break-info
17747 @subsubheading Synopsis
17750 -break-info @var{breakpoint}
17754 Get information about a single breakpoint.
17756 @subsubheading @value{GDBN} command
17758 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
17760 @subsubheading Example
17763 @subheading The @code{-break-insert} Command
17764 @findex -break-insert
17766 @subsubheading Synopsis
17769 -break-insert [ -t ] [ -h ] [ -r ]
17770 [ -c @var{condition} ] [ -i @var{ignore-count} ]
17771 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
17775 If specified, @var{line}, can be one of:
17782 @item filename:linenum
17783 @item filename:function
17787 The possible optional parameters of this command are:
17791 Insert a tempoary breakpoint.
17793 Insert a hardware breakpoint.
17794 @item -c @var{condition}
17795 Make the breakpoint conditional on @var{condition}.
17796 @item -i @var{ignore-count}
17797 Initialize the @var{ignore-count}.
17799 Insert a regular breakpoint in all the functions whose names match the
17800 given regular expression. Other flags are not applicable to regular
17804 @subsubheading Result
17806 The result is in the form:
17809 ^done,bkptno="@var{number}",func="@var{funcname}",
17810 file="@var{filename}",line="@var{lineno}"
17814 where @var{number} is the @value{GDBN} number for this breakpoint, @var{funcname}
17815 is the name of the function where the breakpoint was inserted,
17816 @var{filename} is the name of the source file which contains this
17817 function, and @var{lineno} is the source line number within that file.
17819 Note: this format is open to change.
17820 @c An out-of-band breakpoint instead of part of the result?
17822 @subsubheading @value{GDBN} Command
17824 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
17825 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
17827 @subsubheading Example
17832 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
17834 -break-insert -t foo
17835 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",line="11"@}
17838 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17839 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17840 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17841 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17842 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17843 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17844 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17845 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17846 addr="0x0001072c", func="main",file="recursive2.c",line="4",times="0"@},
17847 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
17848 addr="0x00010774",func="foo",file="recursive2.c",line="11",times="0"@}]@}
17850 -break-insert -r foo.*
17851 ~int foo(int, int);
17852 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c",line="11"@}
17856 @subheading The @code{-break-list} Command
17857 @findex -break-list
17859 @subsubheading Synopsis
17865 Displays the list of inserted breakpoints, showing the following fields:
17869 number of the breakpoint
17871 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
17873 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
17876 is the breakpoint enabled or no: @samp{y} or @samp{n}
17878 memory location at which the breakpoint is set
17880 logical location of the breakpoint, expressed by function name, file
17883 number of times the breakpoint has been hit
17886 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
17887 @code{body} field is an empty list.
17889 @subsubheading @value{GDBN} Command
17891 The corresponding @value{GDBN} command is @samp{info break}.
17893 @subsubheading Example
17898 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17899 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17900 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17901 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17902 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17903 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17904 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17905 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17906 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
17907 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
17908 addr="0x00010114",func="foo",file="hello.c",line="13",times="0"@}]@}
17912 Here's an example of the result when there are no breakpoints:
17917 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
17918 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17919 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17920 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17921 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17922 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17923 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17928 @subheading The @code{-break-watch} Command
17929 @findex -break-watch
17931 @subsubheading Synopsis
17934 -break-watch [ -a | -r ]
17937 Create a watchpoint. With the @samp{-a} option it will create an
17938 @dfn{access} watchpoint, i.e. a watchpoint that triggers either on a
17939 read from or on a write to the memory location. With the @samp{-r}
17940 option, the watchpoint created is a @dfn{read} watchpoint, i.e. it will
17941 trigger only when the memory location is accessed for reading. Without
17942 either of the options, the watchpoint created is a regular watchpoint,
17943 i.e. it will trigger when the memory location is accessed for writing.
17944 @xref{Set Watchpoints, , Setting watchpoints}.
17946 Note that @samp{-break-list} will report a single list of watchpoints and
17947 breakpoints inserted.
17949 @subsubheading @value{GDBN} Command
17951 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
17954 @subsubheading Example
17956 Setting a watchpoint on a variable in the @code{main} function:
17961 ^done,wpt=@{number="2",exp="x"@}
17965 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
17966 value=@{old="-268439212",new="55"@},
17967 frame=@{func="main",args=[],file="recursive2.c",
17968 fullname="/home/foo/bar/devo/myproject/recursive2.c",line="5"@}
17972 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
17973 the program execution twice: first for the variable changing value, then
17974 for the watchpoint going out of scope.
17979 ^done,wpt=@{number="5",exp="C"@}
17983 ^done,reason="watchpoint-trigger",
17984 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
17985 frame=@{func="callee4",args=[],
17986 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
17987 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
17991 ^done,reason="watchpoint-scope",wpnum="5",
17992 frame=@{func="callee3",args=[@{name="strarg",
17993 value="0x11940 \"A string argument.\""@}],
17994 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
17995 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
17999 Listing breakpoints and watchpoints, at different points in the program
18000 execution. Note that once the watchpoint goes out of scope, it is
18006 ^done,wpt=@{number="2",exp="C"@}
18009 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18010 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18011 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18012 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18013 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18014 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18015 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18016 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18017 addr="0x00010734",func="callee4",
18018 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
18019 bkpt=@{number="2",type="watchpoint",disp="keep",
18020 enabled="y",addr="",what="C",times="0"@}]@}
18024 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
18025 value=@{old="-276895068",new="3"@},
18026 frame=@{func="callee4",args=[],
18027 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18028 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18031 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18032 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18033 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18034 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18035 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18036 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18037 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18038 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18039 addr="0x00010734",func="callee4",
18040 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
18041 bkpt=@{number="2",type="watchpoint",disp="keep",
18042 enabled="y",addr="",what="C",times="-5"@}]@}
18046 ^done,reason="watchpoint-scope",wpnum="2",
18047 frame=@{func="callee3",args=[@{name="strarg",
18048 value="0x11940 \"A string argument.\""@}],
18049 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18050 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18053 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18054 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18055 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18056 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18057 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18058 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18059 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18060 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18061 addr="0x00010734",func="callee4",
18062 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@}]@}
18066 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18067 @node GDB/MI Data Manipulation
18068 @section @sc{gdb/mi} Data Manipulation
18070 @cindex data manipulation, in @sc{gdb/mi}
18071 @cindex @sc{gdb/mi}, data manipulation
18072 This section describes the @sc{gdb/mi} commands that manipulate data:
18073 examine memory and registers, evaluate expressions, etc.
18075 @c REMOVED FROM THE INTERFACE.
18076 @c @subheading -data-assign
18077 @c Change the value of a program variable. Plenty of side effects.
18078 @c @subsubheading GDB command
18080 @c @subsubheading Example
18083 @subheading The @code{-data-disassemble} Command
18084 @findex -data-disassemble
18086 @subsubheading Synopsis
18090 [ -s @var{start-addr} -e @var{end-addr} ]
18091 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
18099 @item @var{start-addr}
18100 is the beginning address (or @code{$pc})
18101 @item @var{end-addr}
18103 @item @var{filename}
18104 is the name of the file to disassemble
18105 @item @var{linenum}
18106 is the line number to disassemble around
18108 is the the number of disassembly lines to be produced. If it is -1,
18109 the whole function will be disassembled, in case no @var{end-addr} is
18110 specified. If @var{end-addr} is specified as a non-zero value, and
18111 @var{lines} is lower than the number of disassembly lines between
18112 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
18113 displayed; if @var{lines} is higher than the number of lines between
18114 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
18117 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
18121 @subsubheading Result
18123 The output for each instruction is composed of four fields:
18132 Note that whatever included in the instruction field, is not manipulated
18133 directely by @sc{gdb/mi}, i.e. it is not possible to adjust its format.
18135 @subsubheading @value{GDBN} Command
18137 There's no direct mapping from this command to the CLI.
18139 @subsubheading Example
18141 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
18145 -data-disassemble -s $pc -e "$pc + 20" -- 0
18148 @{address="0x000107c0",func-name="main",offset="4",
18149 inst="mov 2, %o0"@},
18150 @{address="0x000107c4",func-name="main",offset="8",
18151 inst="sethi %hi(0x11800), %o2"@},
18152 @{address="0x000107c8",func-name="main",offset="12",
18153 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
18154 @{address="0x000107cc",func-name="main",offset="16",
18155 inst="sethi %hi(0x11800), %o2"@},
18156 @{address="0x000107d0",func-name="main",offset="20",
18157 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
18161 Disassemble the whole @code{main} function. Line 32 is part of
18165 -data-disassemble -f basics.c -l 32 -- 0
18167 @{address="0x000107bc",func-name="main",offset="0",
18168 inst="save %sp, -112, %sp"@},
18169 @{address="0x000107c0",func-name="main",offset="4",
18170 inst="mov 2, %o0"@},
18171 @{address="0x000107c4",func-name="main",offset="8",
18172 inst="sethi %hi(0x11800), %o2"@},
18174 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
18175 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
18179 Disassemble 3 instructions from the start of @code{main}:
18183 -data-disassemble -f basics.c -l 32 -n 3 -- 0
18185 @{address="0x000107bc",func-name="main",offset="0",
18186 inst="save %sp, -112, %sp"@},
18187 @{address="0x000107c0",func-name="main",offset="4",
18188 inst="mov 2, %o0"@},
18189 @{address="0x000107c4",func-name="main",offset="8",
18190 inst="sethi %hi(0x11800), %o2"@}]
18194 Disassemble 3 instructions from the start of @code{main} in mixed mode:
18198 -data-disassemble -f basics.c -l 32 -n 3 -- 1
18200 src_and_asm_line=@{line="31",
18201 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
18202 testsuite/gdb.mi/basics.c",line_asm_insn=[
18203 @{address="0x000107bc",func-name="main",offset="0",
18204 inst="save %sp, -112, %sp"@}]@},
18205 src_and_asm_line=@{line="32",
18206 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
18207 testsuite/gdb.mi/basics.c",line_asm_insn=[
18208 @{address="0x000107c0",func-name="main",offset="4",
18209 inst="mov 2, %o0"@},
18210 @{address="0x000107c4",func-name="main",offset="8",
18211 inst="sethi %hi(0x11800), %o2"@}]@}]
18216 @subheading The @code{-data-evaluate-expression} Command
18217 @findex -data-evaluate-expression
18219 @subsubheading Synopsis
18222 -data-evaluate-expression @var{expr}
18225 Evaluate @var{expr} as an expression. The expression could contain an
18226 inferior function call. The function call will execute synchronously.
18227 If the expression contains spaces, it must be enclosed in double quotes.
18229 @subsubheading @value{GDBN} Command
18231 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
18232 @samp{call}. In @code{gdbtk} only, there's a corresponding
18233 @samp{gdb_eval} command.
18235 @subsubheading Example
18237 In the following example, the numbers that precede the commands are the
18238 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
18239 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
18243 211-data-evaluate-expression A
18246 311-data-evaluate-expression &A
18247 311^done,value="0xefffeb7c"
18249 411-data-evaluate-expression A+3
18252 511-data-evaluate-expression "A + 3"
18258 @subheading The @code{-data-list-changed-registers} Command
18259 @findex -data-list-changed-registers
18261 @subsubheading Synopsis
18264 -data-list-changed-registers
18267 Display a list of the registers that have changed.
18269 @subsubheading @value{GDBN} Command
18271 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
18272 has the corresponding command @samp{gdb_changed_register_list}.
18274 @subsubheading Example
18276 On a PPC MBX board:
18284 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
18285 args=[],file="try.c",fullname="/home/foo/bar/devo/myproject/try.c",line="5"@}
18287 -data-list-changed-registers
18288 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
18289 "10","11","13","14","15","16","17","18","19","20","21","22","23",
18290 "24","25","26","27","28","30","31","64","65","66","67","69"]
18295 @subheading The @code{-data-list-register-names} Command
18296 @findex -data-list-register-names
18298 @subsubheading Synopsis
18301 -data-list-register-names [ ( @var{regno} )+ ]
18304 Show a list of register names for the current target. If no arguments
18305 are given, it shows a list of the names of all the registers. If
18306 integer numbers are given as arguments, it will print a list of the
18307 names of the registers corresponding to the arguments. To ensure
18308 consistency between a register name and its number, the output list may
18309 include empty register names.
18311 @subsubheading @value{GDBN} Command
18313 @value{GDBN} does not have a command which corresponds to
18314 @samp{-data-list-register-names}. In @code{gdbtk} there is a
18315 corresponding command @samp{gdb_regnames}.
18317 @subsubheading Example
18319 For the PPC MBX board:
18322 -data-list-register-names
18323 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
18324 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
18325 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
18326 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
18327 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
18328 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
18329 "", "pc","ps","cr","lr","ctr","xer"]
18331 -data-list-register-names 1 2 3
18332 ^done,register-names=["r1","r2","r3"]
18336 @subheading The @code{-data-list-register-values} Command
18337 @findex -data-list-register-values
18339 @subsubheading Synopsis
18342 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
18345 Display the registers' contents. @var{fmt} is the format according to
18346 which the registers' contents are to be returned, followed by an optional
18347 list of numbers specifying the registers to display. A missing list of
18348 numbers indicates that the contents of all the registers must be returned.
18350 Allowed formats for @var{fmt} are:
18367 @subsubheading @value{GDBN} Command
18369 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
18370 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
18372 @subsubheading Example
18374 For a PPC MBX board (note: line breaks are for readability only, they
18375 don't appear in the actual output):
18379 -data-list-register-values r 64 65
18380 ^done,register-values=[@{number="64",value="0xfe00a300"@},
18381 @{number="65",value="0x00029002"@}]
18383 -data-list-register-values x
18384 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
18385 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
18386 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
18387 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
18388 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
18389 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
18390 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
18391 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
18392 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
18393 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
18394 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
18395 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
18396 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
18397 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
18398 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
18399 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
18400 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
18401 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
18402 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
18403 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
18404 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
18405 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
18406 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
18407 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
18408 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
18409 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
18410 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
18411 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
18412 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
18413 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
18414 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
18415 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
18416 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
18417 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
18418 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
18419 @{number="69",value="0x20002b03"@}]
18424 @subheading The @code{-data-read-memory} Command
18425 @findex -data-read-memory
18427 @subsubheading Synopsis
18430 -data-read-memory [ -o @var{byte-offset} ]
18431 @var{address} @var{word-format} @var{word-size}
18432 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
18439 @item @var{address}
18440 An expression specifying the address of the first memory word to be
18441 read. Complex expressions containing embedded white space should be
18442 quoted using the C convention.
18444 @item @var{word-format}
18445 The format to be used to print the memory words. The notation is the
18446 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
18449 @item @var{word-size}
18450 The size of each memory word in bytes.
18452 @item @var{nr-rows}
18453 The number of rows in the output table.
18455 @item @var{nr-cols}
18456 The number of columns in the output table.
18459 If present, indicates that each row should include an @sc{ascii} dump. The
18460 value of @var{aschar} is used as a padding character when a byte is not a
18461 member of the printable @sc{ascii} character set (printable @sc{ascii}
18462 characters are those whose code is between 32 and 126, inclusively).
18464 @item @var{byte-offset}
18465 An offset to add to the @var{address} before fetching memory.
18468 This command displays memory contents as a table of @var{nr-rows} by
18469 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
18470 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
18471 (returned as @samp{total-bytes}). Should less than the requested number
18472 of bytes be returned by the target, the missing words are identified
18473 using @samp{N/A}. The number of bytes read from the target is returned
18474 in @samp{nr-bytes} and the starting address used to read memory in
18477 The address of the next/previous row or page is available in
18478 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
18481 @subsubheading @value{GDBN} Command
18483 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
18484 @samp{gdb_get_mem} memory read command.
18486 @subsubheading Example
18488 Read six bytes of memory starting at @code{bytes+6} but then offset by
18489 @code{-6} bytes. Format as three rows of two columns. One byte per
18490 word. Display each word in hex.
18494 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
18495 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
18496 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
18497 prev-page="0x0000138a",memory=[
18498 @{addr="0x00001390",data=["0x00","0x01"]@},
18499 @{addr="0x00001392",data=["0x02","0x03"]@},
18500 @{addr="0x00001394",data=["0x04","0x05"]@}]
18504 Read two bytes of memory starting at address @code{shorts + 64} and
18505 display as a single word formatted in decimal.
18509 5-data-read-memory shorts+64 d 2 1 1
18510 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
18511 next-row="0x00001512",prev-row="0x0000150e",
18512 next-page="0x00001512",prev-page="0x0000150e",memory=[
18513 @{addr="0x00001510",data=["128"]@}]
18517 Read thirty two bytes of memory starting at @code{bytes+16} and format
18518 as eight rows of four columns. Include a string encoding with @samp{x}
18519 used as the non-printable character.
18523 4-data-read-memory bytes+16 x 1 8 4 x
18524 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
18525 next-row="0x000013c0",prev-row="0x0000139c",
18526 next-page="0x000013c0",prev-page="0x00001380",memory=[
18527 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
18528 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
18529 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
18530 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
18531 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
18532 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
18533 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
18534 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
18538 @subheading The @code{-display-delete} Command
18539 @findex -display-delete
18541 @subsubheading Synopsis
18544 -display-delete @var{number}
18547 Delete the display @var{number}.
18549 @subsubheading @value{GDBN} Command
18551 The corresponding @value{GDBN} command is @samp{delete display}.
18553 @subsubheading Example
18557 @subheading The @code{-display-disable} Command
18558 @findex -display-disable
18560 @subsubheading Synopsis
18563 -display-disable @var{number}
18566 Disable display @var{number}.
18568 @subsubheading @value{GDBN} Command
18570 The corresponding @value{GDBN} command is @samp{disable display}.
18572 @subsubheading Example
18576 @subheading The @code{-display-enable} Command
18577 @findex -display-enable
18579 @subsubheading Synopsis
18582 -display-enable @var{number}
18585 Enable display @var{number}.
18587 @subsubheading @value{GDBN} Command
18589 The corresponding @value{GDBN} command is @samp{enable display}.
18591 @subsubheading Example
18595 @subheading The @code{-display-insert} Command
18596 @findex -display-insert
18598 @subsubheading Synopsis
18601 -display-insert @var{expression}
18604 Display @var{expression} every time the program stops.
18606 @subsubheading @value{GDBN} Command
18608 The corresponding @value{GDBN} command is @samp{display}.
18610 @subsubheading Example
18614 @subheading The @code{-display-list} Command
18615 @findex -display-list
18617 @subsubheading Synopsis
18623 List the displays. Do not show the current values.
18625 @subsubheading @value{GDBN} Command
18627 The corresponding @value{GDBN} command is @samp{info display}.
18629 @subsubheading Example
18633 @subheading The @code{-environment-cd} Command
18634 @findex -environment-cd
18636 @subsubheading Synopsis
18639 -environment-cd @var{pathdir}
18642 Set @value{GDBN}'s working directory.
18644 @subsubheading @value{GDBN} Command
18646 The corresponding @value{GDBN} command is @samp{cd}.
18648 @subsubheading Example
18652 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18658 @subheading The @code{-environment-directory} Command
18659 @findex -environment-directory
18661 @subsubheading Synopsis
18664 -environment-directory [ -r ] [ @var{pathdir} ]+
18667 Add directories @var{pathdir} to beginning of search path for source files.
18668 If the @samp{-r} option is used, the search path is reset to the default
18669 search path. If directories @var{pathdir} are supplied in addition to the
18670 @samp{-r} option, the search path is first reset and then addition
18672 Multiple directories may be specified, separated by blanks. Specifying
18673 multiple directories in a single command
18674 results in the directories added to the beginning of the
18675 search path in the same order they were presented in the command.
18676 If blanks are needed as
18677 part of a directory name, double-quotes should be used around
18678 the name. In the command output, the path will show up separated
18679 by the system directory-separator character. The directory-seperator
18680 character must not be used
18681 in any directory name.
18682 If no directories are specified, the current search path is displayed.
18684 @subsubheading @value{GDBN} Command
18686 The corresponding @value{GDBN} command is @samp{dir}.
18688 @subsubheading Example
18692 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18693 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18695 -environment-directory ""
18696 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18698 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
18699 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
18701 -environment-directory -r
18702 ^done,source-path="$cdir:$cwd"
18707 @subheading The @code{-environment-path} Command
18708 @findex -environment-path
18710 @subsubheading Synopsis
18713 -environment-path [ -r ] [ @var{pathdir} ]+
18716 Add directories @var{pathdir} to beginning of search path for object files.
18717 If the @samp{-r} option is used, the search path is reset to the original
18718 search path that existed at gdb start-up. If directories @var{pathdir} are
18719 supplied in addition to the
18720 @samp{-r} option, the search path is first reset and then addition
18722 Multiple directories may be specified, separated by blanks. Specifying
18723 multiple directories in a single command
18724 results in the directories added to the beginning of the
18725 search path in the same order they were presented in the command.
18726 If blanks are needed as
18727 part of a directory name, double-quotes should be used around
18728 the name. In the command output, the path will show up separated
18729 by the system directory-separator character. The directory-seperator
18730 character must not be used
18731 in any directory name.
18732 If no directories are specified, the current path is displayed.
18735 @subsubheading @value{GDBN} Command
18737 The corresponding @value{GDBN} command is @samp{path}.
18739 @subsubheading Example
18744 ^done,path="/usr/bin"
18746 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
18747 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
18749 -environment-path -r /usr/local/bin
18750 ^done,path="/usr/local/bin:/usr/bin"
18755 @subheading The @code{-environment-pwd} Command
18756 @findex -environment-pwd
18758 @subsubheading Synopsis
18764 Show the current working directory.
18766 @subsubheading @value{GDBN} command
18768 The corresponding @value{GDBN} command is @samp{pwd}.
18770 @subsubheading Example
18775 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
18779 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18780 @node GDB/MI Program Control
18781 @section @sc{gdb/mi} Program control
18783 @subsubheading Program termination
18785 As a result of execution, the inferior program can run to completion, if
18786 it doesn't encounter any breakpoints. In this case the output will
18787 include an exit code, if the program has exited exceptionally.
18789 @subsubheading Examples
18792 Program exited normally:
18800 *stopped,reason="exited-normally"
18805 Program exited exceptionally:
18813 *stopped,reason="exited",exit-code="01"
18817 Another way the program can terminate is if it receives a signal such as
18818 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
18822 *stopped,reason="exited-signalled",signal-name="SIGINT",
18823 signal-meaning="Interrupt"
18827 @subheading The @code{-exec-abort} Command
18828 @findex -exec-abort
18830 @subsubheading Synopsis
18836 Kill the inferior running program.
18838 @subsubheading @value{GDBN} Command
18840 The corresponding @value{GDBN} command is @samp{kill}.
18842 @subsubheading Example
18846 @subheading The @code{-exec-arguments} Command
18847 @findex -exec-arguments
18849 @subsubheading Synopsis
18852 -exec-arguments @var{args}
18855 Set the inferior program arguments, to be used in the next
18858 @subsubheading @value{GDBN} Command
18860 The corresponding @value{GDBN} command is @samp{set args}.
18862 @subsubheading Example
18865 Don't have one around.
18868 @subheading The @code{-exec-continue} Command
18869 @findex -exec-continue
18871 @subsubheading Synopsis
18877 Asynchronous command. Resumes the execution of the inferior program
18878 until a breakpoint is encountered, or until the inferior exits.
18880 @subsubheading @value{GDBN} Command
18882 The corresponding @value{GDBN} corresponding is @samp{continue}.
18884 @subsubheading Example
18891 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
18892 file="hello.c",fullname="/home/foo/bar/devo/myproject/hello.c",line="13"@}
18897 @subheading The @code{-exec-finish} Command
18898 @findex -exec-finish
18900 @subsubheading Synopsis
18906 Asynchronous command. Resumes the execution of the inferior program
18907 until the current function is exited. Displays the results returned by
18910 @subsubheading @value{GDBN} Command
18912 The corresponding @value{GDBN} command is @samp{finish}.
18914 @subsubheading Example
18916 Function returning @code{void}.
18923 *stopped,reason="function-finished",frame=@{func="main",args=[],
18924 file="hello.c",fullname="/home/foo/bar/devo/myproject/hello.c",line="7"@}
18928 Function returning other than @code{void}. The name of the internal
18929 @value{GDBN} variable storing the result is printed, together with the
18936 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
18937 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
18938 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
18939 gdb-result-var="$1",return-value="0"
18944 @subheading The @code{-exec-interrupt} Command
18945 @findex -exec-interrupt
18947 @subsubheading Synopsis
18953 Asynchronous command. Interrupts the background execution of the target.
18954 Note how the token associated with the stop message is the one for the
18955 execution command that has been interrupted. The token for the interrupt
18956 itself only appears in the @samp{^done} output. If the user is trying to
18957 interrupt a non-running program, an error message will be printed.
18959 @subsubheading @value{GDBN} Command
18961 The corresponding @value{GDBN} command is @samp{interrupt}.
18963 @subsubheading Example
18974 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
18975 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
18976 fullname="/home/foo/bar/devo/myproject/try.c",line="13"@}
18981 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
18986 @subheading The @code{-exec-next} Command
18989 @subsubheading Synopsis
18995 Asynchronous command. Resumes execution of the inferior program, stopping
18996 when the beginning of the next source line is reached.
18998 @subsubheading @value{GDBN} Command
19000 The corresponding @value{GDBN} command is @samp{next}.
19002 @subsubheading Example
19008 *stopped,reason="end-stepping-range",line="8",file="hello.c"
19013 @subheading The @code{-exec-next-instruction} Command
19014 @findex -exec-next-instruction
19016 @subsubheading Synopsis
19019 -exec-next-instruction
19022 Asynchronous command. Executes one machine instruction. If the
19023 instruction is a function call continues until the function returns. If
19024 the program stops at an instruction in the middle of a source line, the
19025 address will be printed as well.
19027 @subsubheading @value{GDBN} Command
19029 The corresponding @value{GDBN} command is @samp{nexti}.
19031 @subsubheading Example
19035 -exec-next-instruction
19039 *stopped,reason="end-stepping-range",
19040 addr="0x000100d4",line="5",file="hello.c"
19045 @subheading The @code{-exec-return} Command
19046 @findex -exec-return
19048 @subsubheading Synopsis
19054 Makes current function return immediately. Doesn't execute the inferior.
19055 Displays the new current frame.
19057 @subsubheading @value{GDBN} Command
19059 The corresponding @value{GDBN} command is @samp{return}.
19061 @subsubheading Example
19065 200-break-insert callee4
19066 200^done,bkpt=@{number="1",addr="0x00010734",
19067 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
19072 000*stopped,reason="breakpoint-hit",bkptno="1",
19073 frame=@{func="callee4",args=[],
19074 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19075 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
19081 111^done,frame=@{level="0",func="callee3",
19082 args=[@{name="strarg",
19083 value="0x11940 \"A string argument.\""@}],
19084 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19085 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
19090 @subheading The @code{-exec-run} Command
19093 @subsubheading Synopsis
19099 Asynchronous command. Starts execution of the inferior from the
19100 beginning. The inferior executes until either a breakpoint is
19101 encountered or the program exits.
19103 @subsubheading @value{GDBN} Command
19105 The corresponding @value{GDBN} command is @samp{run}.
19107 @subsubheading Example
19112 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
19117 *stopped,reason="breakpoint-hit",bkptno="1",
19118 frame=@{func="main",args=[],file="recursive2.c",
19119 fullname="/home/foo/bar/devo/myproject/recursive2.c",line="4"@}
19124 @subheading The @code{-exec-show-arguments} Command
19125 @findex -exec-show-arguments
19127 @subsubheading Synopsis
19130 -exec-show-arguments
19133 Print the arguments of the program.
19135 @subsubheading @value{GDBN} Command
19137 The corresponding @value{GDBN} command is @samp{show args}.
19139 @subsubheading Example
19142 @c @subheading -exec-signal
19144 @subheading The @code{-exec-step} Command
19147 @subsubheading Synopsis
19153 Asynchronous command. Resumes execution of the inferior program, stopping
19154 when the beginning of the next source line is reached, if the next
19155 source line is not a function call. If it is, stop at the first
19156 instruction of the called function.
19158 @subsubheading @value{GDBN} Command
19160 The corresponding @value{GDBN} command is @samp{step}.
19162 @subsubheading Example
19164 Stepping into a function:
19170 *stopped,reason="end-stepping-range",
19171 frame=@{func="foo",args=[@{name="a",value="10"@},
19172 @{name="b",value="0"@}],file="recursive2.c",
19173 fullname="/home/foo/bar/devo/myproject/recursive2.c",line="11"@}
19183 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
19188 @subheading The @code{-exec-step-instruction} Command
19189 @findex -exec-step-instruction
19191 @subsubheading Synopsis
19194 -exec-step-instruction
19197 Asynchronous command. Resumes the inferior which executes one machine
19198 instruction. The output, once @value{GDBN} has stopped, will vary depending on
19199 whether we have stopped in the middle of a source line or not. In the
19200 former case, the address at which the program stopped will be printed as
19203 @subsubheading @value{GDBN} Command
19205 The corresponding @value{GDBN} command is @samp{stepi}.
19207 @subsubheading Example
19211 -exec-step-instruction
19215 *stopped,reason="end-stepping-range",
19216 frame=@{func="foo",args=[],file="try.c",
19217 fullname="/home/foo/bar/devo/myproject/try.c",line="10"@}
19219 -exec-step-instruction
19223 *stopped,reason="end-stepping-range",
19224 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
19225 fullname="/home/foo/bar/devo/myproject/try.c",line="10"@}
19230 @subheading The @code{-exec-until} Command
19231 @findex -exec-until
19233 @subsubheading Synopsis
19236 -exec-until [ @var{location} ]
19239 Asynchronous command. Executes the inferior until the @var{location}
19240 specified in the argument is reached. If there is no argument, the inferior
19241 executes until a source line greater than the current one is reached.
19242 The reason for stopping in this case will be @samp{location-reached}.
19244 @subsubheading @value{GDBN} Command
19246 The corresponding @value{GDBN} command is @samp{until}.
19248 @subsubheading Example
19252 -exec-until recursive2.c:6
19256 *stopped,reason="location-reached",frame=@{func="main",args=[],
19257 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="6"@}
19262 @subheading -file-clear
19263 Is this going away????
19267 @subheading The @code{-file-exec-and-symbols} Command
19268 @findex -file-exec-and-symbols
19270 @subsubheading Synopsis
19273 -file-exec-and-symbols @var{file}
19276 Specify the executable file to be debugged. This file is the one from
19277 which the symbol table is also read. If no file is specified, the
19278 command clears the executable and symbol information. If breakpoints
19279 are set when using this command with no arguments, @value{GDBN} will produce
19280 error messages. Otherwise, no output is produced, except a completion
19283 @subsubheading @value{GDBN} Command
19285 The corresponding @value{GDBN} command is @samp{file}.
19287 @subsubheading Example
19291 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
19297 @subheading The @code{-file-exec-file} Command
19298 @findex -file-exec-file
19300 @subsubheading Synopsis
19303 -file-exec-file @var{file}
19306 Specify the executable file to be debugged. Unlike
19307 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
19308 from this file. If used without argument, @value{GDBN} clears the information
19309 about the executable file. No output is produced, except a completion
19312 @subsubheading @value{GDBN} Command
19314 The corresponding @value{GDBN} command is @samp{exec-file}.
19316 @subsubheading Example
19320 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
19326 @subheading The @code{-file-list-exec-sections} Command
19327 @findex -file-list-exec-sections
19329 @subsubheading Synopsis
19332 -file-list-exec-sections
19335 List the sections of the current executable file.
19337 @subsubheading @value{GDBN} Command
19339 The @value{GDBN} command @samp{info file} shows, among the rest, the same
19340 information as this command. @code{gdbtk} has a corresponding command
19341 @samp{gdb_load_info}.
19343 @subsubheading Example
19347 @subheading The @code{-file-list-exec-source-file} Command
19348 @findex -file-list-exec-source-file
19350 @subsubheading Synopsis
19353 -file-list-exec-source-file
19356 List the line number, the current source file, and the absolute path
19357 to the current source file for the current executable.
19359 @subsubheading @value{GDBN} Command
19361 There's no @value{GDBN} command which directly corresponds to this one.
19363 @subsubheading Example
19367 123-file-list-exec-source-file
19368 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
19373 @subheading The @code{-file-list-exec-source-files} Command
19374 @findex -file-list-exec-source-files
19376 @subsubheading Synopsis
19379 -file-list-exec-source-files
19382 List the source files for the current executable.
19384 It will always output the filename, but only when GDB can find the absolute
19385 file name of a source file, will it output the fullname.
19387 @subsubheading @value{GDBN} Command
19389 There's no @value{GDBN} command which directly corresponds to this one.
19390 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
19392 @subsubheading Example
19395 -file-list-exec-source-files
19397 @{file=foo.c,fullname=/home/foo.c@},
19398 @{file=/home/bar.c,fullname=/home/bar.c@},
19399 @{file=gdb_could_not_find_fullpath.c@}]
19403 @subheading The @code{-file-list-shared-libraries} Command
19404 @findex -file-list-shared-libraries
19406 @subsubheading Synopsis
19409 -file-list-shared-libraries
19412 List the shared libraries in the program.
19414 @subsubheading @value{GDBN} Command
19416 The corresponding @value{GDBN} command is @samp{info shared}.
19418 @subsubheading Example
19422 @subheading The @code{-file-list-symbol-files} Command
19423 @findex -file-list-symbol-files
19425 @subsubheading Synopsis
19428 -file-list-symbol-files
19433 @subsubheading @value{GDBN} Command
19435 The corresponding @value{GDBN} command is @samp{info file} (part of it).
19437 @subsubheading Example
19441 @subheading The @code{-file-symbol-file} Command
19442 @findex -file-symbol-file
19444 @subsubheading Synopsis
19447 -file-symbol-file @var{file}
19450 Read symbol table info from the specified @var{file} argument. When
19451 used without arguments, clears @value{GDBN}'s symbol table info. No output is
19452 produced, except for a completion notification.
19454 @subsubheading @value{GDBN} Command
19456 The corresponding @value{GDBN} command is @samp{symbol-file}.
19458 @subsubheading Example
19462 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
19467 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19468 @node GDB/MI Miscellaneous Commands
19469 @section Miscellaneous @value{GDBN} commands in @sc{gdb/mi}
19471 @c @subheading -gdb-complete
19473 @subheading The @code{-gdb-exit} Command
19476 @subsubheading Synopsis
19482 Exit @value{GDBN} immediately.
19484 @subsubheading @value{GDBN} Command
19486 Approximately corresponds to @samp{quit}.
19488 @subsubheading Example
19495 @subheading The @code{-gdb-set} Command
19498 @subsubheading Synopsis
19504 Set an internal @value{GDBN} variable.
19505 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
19507 @subsubheading @value{GDBN} Command
19509 The corresponding @value{GDBN} command is @samp{set}.
19511 @subsubheading Example
19521 @subheading The @code{-gdb-show} Command
19524 @subsubheading Synopsis
19530 Show the current value of a @value{GDBN} variable.
19532 @subsubheading @value{GDBN} command
19534 The corresponding @value{GDBN} command is @samp{show}.
19536 @subsubheading Example
19545 @c @subheading -gdb-source
19548 @subheading The @code{-gdb-version} Command
19549 @findex -gdb-version
19551 @subsubheading Synopsis
19557 Show version information for @value{GDBN}. Used mostly in testing.
19559 @subsubheading @value{GDBN} Command
19561 There's no equivalent @value{GDBN} command. @value{GDBN} by default shows this
19562 information when you start an interactive session.
19564 @subsubheading Example
19566 @c This example modifies the actual output from GDB to avoid overfull
19572 ~Copyright 2000 Free Software Foundation, Inc.
19573 ~GDB is free software, covered by the GNU General Public License, and
19574 ~you are welcome to change it and/or distribute copies of it under
19575 ~ certain conditions.
19576 ~Type "show copying" to see the conditions.
19577 ~There is absolutely no warranty for GDB. Type "show warranty" for
19579 ~This GDB was configured as
19580 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
19585 @subheading The @code{-interpreter-exec} Command
19586 @findex -interpreter-exec
19588 @subheading Synopsis
19591 -interpreter-exec @var{interpreter} @var{command}
19594 Execute the specified @var{command} in the given @var{interpreter}.
19596 @subheading @value{GDBN} Command
19598 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
19600 @subheading Example
19604 -interpreter-exec console "break main"
19605 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
19606 &"During symbol reading, bad structure-type format.\n"
19607 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
19612 @subheading The @code{-inferior-tty-set} Command
19613 @findex -inferior-tty-set
19615 @subheading Synopsis
19618 -inferior-tty-set /dev/pts/1
19621 Set terminal for future runs of the program being debugged.
19623 @subheading @value{GDBN} Command
19625 The corresponding @value{GDBN} command is @samp{set inferior-tty /dev/pts/1}.
19627 @subheading Example
19631 -inferior-tty-set /dev/pts/1
19636 @subheading The @code{-inferior-tty-show} Command
19637 @findex -inferior-tty-show
19639 @subheading Synopsis
19645 Show terminal for future runs of program being debugged.
19647 @subheading @value{GDBN} Command
19649 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
19651 @subheading Example
19655 -inferior-tty-set /dev/pts/1
19659 ^done,inferior_tty_terminal="/dev/pts/1"
19664 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19665 @node GDB/MI Kod Commands
19666 @section @sc{gdb/mi} Kod Commands
19668 The Kod commands are not implemented.
19670 @c @subheading -kod-info
19672 @c @subheading -kod-list
19674 @c @subheading -kod-list-object-types
19676 @c @subheading -kod-show
19678 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19679 @node GDB/MI Memory Overlay Commands
19680 @section @sc{gdb/mi} Memory Overlay Commands
19682 The memory overlay commands are not implemented.
19684 @c @subheading -overlay-auto
19686 @c @subheading -overlay-list-mapping-state
19688 @c @subheading -overlay-list-overlays
19690 @c @subheading -overlay-map
19692 @c @subheading -overlay-off
19694 @c @subheading -overlay-on
19696 @c @subheading -overlay-unmap
19698 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19699 @node GDB/MI Signal Handling Commands
19700 @section @sc{gdb/mi} Signal Handling Commands
19702 Signal handling commands are not implemented.
19704 @c @subheading -signal-handle
19706 @c @subheading -signal-list-handle-actions
19708 @c @subheading -signal-list-signal-types
19712 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19713 @node GDB/MI Stack Manipulation
19714 @section @sc{gdb/mi} Stack Manipulation Commands
19717 @subheading The @code{-stack-info-frame} Command
19718 @findex -stack-info-frame
19720 @subsubheading Synopsis
19726 Get info on the selected frame.
19728 @subsubheading @value{GDBN} Command
19730 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
19731 (without arguments).
19733 @subsubheading Example
19738 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
19739 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19740 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
19744 @subheading The @code{-stack-info-depth} Command
19745 @findex -stack-info-depth
19747 @subsubheading Synopsis
19750 -stack-info-depth [ @var{max-depth} ]
19753 Return the depth of the stack. If the integer argument @var{max-depth}
19754 is specified, do not count beyond @var{max-depth} frames.
19756 @subsubheading @value{GDBN} Command
19758 There's no equivalent @value{GDBN} command.
19760 @subsubheading Example
19762 For a stack with frame levels 0 through 11:
19769 -stack-info-depth 4
19772 -stack-info-depth 12
19775 -stack-info-depth 11
19778 -stack-info-depth 13
19783 @subheading The @code{-stack-list-arguments} Command
19784 @findex -stack-list-arguments
19786 @subsubheading Synopsis
19789 -stack-list-arguments @var{show-values}
19790 [ @var{low-frame} @var{high-frame} ]
19793 Display a list of the arguments for the frames between @var{low-frame}
19794 and @var{high-frame} (inclusive). If @var{low-frame} and
19795 @var{high-frame} are not provided, list the arguments for the whole call
19798 The @var{show-values} argument must have a value of 0 or 1. A value of
19799 0 means that only the names of the arguments are listed, a value of 1
19800 means that both names and values of the arguments are printed.
19802 @subsubheading @value{GDBN} Command
19804 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
19805 @samp{gdb_get_args} command which partially overlaps with the
19806 functionality of @samp{-stack-list-arguments}.
19808 @subsubheading Example
19815 frame=@{level="0",addr="0x00010734",func="callee4",
19816 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19817 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
19818 frame=@{level="1",addr="0x0001076c",func="callee3",
19819 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19820 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
19821 frame=@{level="2",addr="0x0001078c",func="callee2",
19822 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19823 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
19824 frame=@{level="3",addr="0x000107b4",func="callee1",
19825 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19826 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
19827 frame=@{level="4",addr="0x000107e0",func="main",
19828 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19829 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
19831 -stack-list-arguments 0
19834 frame=@{level="0",args=[]@},
19835 frame=@{level="1",args=[name="strarg"]@},
19836 frame=@{level="2",args=[name="intarg",name="strarg"]@},
19837 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
19838 frame=@{level="4",args=[]@}]
19840 -stack-list-arguments 1
19843 frame=@{level="0",args=[]@},
19845 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19846 frame=@{level="2",args=[
19847 @{name="intarg",value="2"@},
19848 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19849 @{frame=@{level="3",args=[
19850 @{name="intarg",value="2"@},
19851 @{name="strarg",value="0x11940 \"A string argument.\""@},
19852 @{name="fltarg",value="3.5"@}]@},
19853 frame=@{level="4",args=[]@}]
19855 -stack-list-arguments 0 2 2
19856 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
19858 -stack-list-arguments 1 2 2
19859 ^done,stack-args=[frame=@{level="2",
19860 args=[@{name="intarg",value="2"@},
19861 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
19865 @c @subheading -stack-list-exception-handlers
19868 @subheading The @code{-stack-list-frames} Command
19869 @findex -stack-list-frames
19871 @subsubheading Synopsis
19874 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
19877 List the frames currently on the stack. For each frame it displays the
19882 The frame number, 0 being the topmost frame, i.e. the innermost function.
19884 The @code{$pc} value for that frame.
19888 File name of the source file where the function lives.
19890 Line number corresponding to the @code{$pc}.
19893 If invoked without arguments, this command prints a backtrace for the
19894 whole stack. If given two integer arguments, it shows the frames whose
19895 levels are between the two arguments (inclusive). If the two arguments
19896 are equal, it shows the single frame at the corresponding level.
19898 @subsubheading @value{GDBN} Command
19900 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
19902 @subsubheading Example
19904 Full stack backtrace:
19910 [frame=@{level="0",addr="0x0001076c",func="foo",
19911 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="11"@},
19912 frame=@{level="1",addr="0x000107a4",func="foo",
19913 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19914 frame=@{level="2",addr="0x000107a4",func="foo",
19915 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19916 frame=@{level="3",addr="0x000107a4",func="foo",
19917 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19918 frame=@{level="4",addr="0x000107a4",func="foo",
19919 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19920 frame=@{level="5",addr="0x000107a4",func="foo",
19921 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19922 frame=@{level="6",addr="0x000107a4",func="foo",
19923 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19924 frame=@{level="7",addr="0x000107a4",func="foo",
19925 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19926 frame=@{level="8",addr="0x000107a4",func="foo",
19927 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19928 frame=@{level="9",addr="0x000107a4",func="foo",
19929 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19930 frame=@{level="10",addr="0x000107a4",func="foo",
19931 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19932 frame=@{level="11",addr="0x00010738",func="main",
19933 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="4"@}]
19937 Show frames between @var{low_frame} and @var{high_frame}:
19941 -stack-list-frames 3 5
19943 [frame=@{level="3",addr="0x000107a4",func="foo",
19944 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19945 frame=@{level="4",addr="0x000107a4",func="foo",
19946 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19947 frame=@{level="5",addr="0x000107a4",func="foo",
19948 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@}]
19952 Show a single frame:
19956 -stack-list-frames 3 3
19958 [frame=@{level="3",addr="0x000107a4",func="foo",
19959 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@}]
19964 @subheading The @code{-stack-list-locals} Command
19965 @findex -stack-list-locals
19967 @subsubheading Synopsis
19970 -stack-list-locals @var{print-values}
19973 Display the local variable names for the selected frame. If
19974 @var{print-values} is 0 or @code{--no-values}, print only the names of
19975 the variables; if it is 1 or @code{--all-values}, print also their
19976 values; and if it is 2 or @code{--simple-values}, print the name,
19977 type and value for simple data types and the name and type for arrays,
19978 structures and unions. In this last case, a frontend can immediately
19979 display the value of simple data types and create variable objects for
19980 other data types when the the user wishes to explore their values in
19983 @subsubheading @value{GDBN} Command
19985 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
19987 @subsubheading Example
19991 -stack-list-locals 0
19992 ^done,locals=[name="A",name="B",name="C"]
19994 -stack-list-locals --all-values
19995 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
19996 @{name="C",value="@{1, 2, 3@}"@}]
19997 -stack-list-locals --simple-values
19998 ^done,locals=[@{name="A",type="int",value="1"@},
19999 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
20004 @subheading The @code{-stack-select-frame} Command
20005 @findex -stack-select-frame
20007 @subsubheading Synopsis
20010 -stack-select-frame @var{framenum}
20013 Change the selected frame. Select a different frame @var{framenum} on
20016 @subsubheading @value{GDBN} Command
20018 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
20019 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
20021 @subsubheading Example
20025 -stack-select-frame 2
20030 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20031 @node GDB/MI Symbol Query
20032 @section @sc{gdb/mi} Symbol Query Commands
20035 @subheading The @code{-symbol-info-address} Command
20036 @findex -symbol-info-address
20038 @subsubheading Synopsis
20041 -symbol-info-address @var{symbol}
20044 Describe where @var{symbol} is stored.
20046 @subsubheading @value{GDBN} Command
20048 The corresponding @value{GDBN} command is @samp{info address}.
20050 @subsubheading Example
20054 @subheading The @code{-symbol-info-file} Command
20055 @findex -symbol-info-file
20057 @subsubheading Synopsis
20063 Show the file for the symbol.
20065 @subsubheading @value{GDBN} Command
20067 There's no equivalent @value{GDBN} command. @code{gdbtk} has
20068 @samp{gdb_find_file}.
20070 @subsubheading Example
20074 @subheading The @code{-symbol-info-function} Command
20075 @findex -symbol-info-function
20077 @subsubheading Synopsis
20080 -symbol-info-function
20083 Show which function the symbol lives in.
20085 @subsubheading @value{GDBN} Command
20087 @samp{gdb_get_function} in @code{gdbtk}.
20089 @subsubheading Example
20093 @subheading The @code{-symbol-info-line} Command
20094 @findex -symbol-info-line
20096 @subsubheading Synopsis
20102 Show the core addresses of the code for a source line.
20104 @subsubheading @value{GDBN} Command
20106 The corresponding @value{GDBN} command is @samp{info line}.
20107 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
20109 @subsubheading Example
20113 @subheading The @code{-symbol-info-symbol} Command
20114 @findex -symbol-info-symbol
20116 @subsubheading Synopsis
20119 -symbol-info-symbol @var{addr}
20122 Describe what symbol is at location @var{addr}.
20124 @subsubheading @value{GDBN} Command
20126 The corresponding @value{GDBN} command is @samp{info symbol}.
20128 @subsubheading Example
20132 @subheading The @code{-symbol-list-functions} Command
20133 @findex -symbol-list-functions
20135 @subsubheading Synopsis
20138 -symbol-list-functions
20141 List the functions in the executable.
20143 @subsubheading @value{GDBN} Command
20145 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
20146 @samp{gdb_search} in @code{gdbtk}.
20148 @subsubheading Example
20152 @subheading The @code{-symbol-list-lines} Command
20153 @findex -symbol-list-lines
20155 @subsubheading Synopsis
20158 -symbol-list-lines @var{filename}
20161 Print the list of lines that contain code and their associated program
20162 addresses for the given source filename. The entries are sorted in
20163 ascending PC order.
20165 @subsubheading @value{GDBN} Command
20167 There is no corresponding @value{GDBN} command.
20169 @subsubheading Example
20172 -symbol-list-lines basics.c
20173 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
20178 @subheading The @code{-symbol-list-types} Command
20179 @findex -symbol-list-types
20181 @subsubheading Synopsis
20187 List all the type names.
20189 @subsubheading @value{GDBN} Command
20191 The corresponding commands are @samp{info types} in @value{GDBN},
20192 @samp{gdb_search} in @code{gdbtk}.
20194 @subsubheading Example
20198 @subheading The @code{-symbol-list-variables} Command
20199 @findex -symbol-list-variables
20201 @subsubheading Synopsis
20204 -symbol-list-variables
20207 List all the global and static variable names.
20209 @subsubheading @value{GDBN} Command
20211 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
20213 @subsubheading Example
20217 @subheading The @code{-symbol-locate} Command
20218 @findex -symbol-locate
20220 @subsubheading Synopsis
20226 @subsubheading @value{GDBN} Command
20228 @samp{gdb_loc} in @code{gdbtk}.
20230 @subsubheading Example
20234 @subheading The @code{-symbol-type} Command
20235 @findex -symbol-type
20237 @subsubheading Synopsis
20240 -symbol-type @var{variable}
20243 Show type of @var{variable}.
20245 @subsubheading @value{GDBN} Command
20247 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
20248 @samp{gdb_obj_variable}.
20250 @subsubheading Example
20254 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20255 @node GDB/MI Target Manipulation
20256 @section @sc{gdb/mi} Target Manipulation Commands
20259 @subheading The @code{-target-attach} Command
20260 @findex -target-attach
20262 @subsubheading Synopsis
20265 -target-attach @var{pid} | @var{file}
20268 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
20270 @subsubheading @value{GDBN} command
20272 The corresponding @value{GDBN} command is @samp{attach}.
20274 @subsubheading Example
20278 @subheading The @code{-target-compare-sections} Command
20279 @findex -target-compare-sections
20281 @subsubheading Synopsis
20284 -target-compare-sections [ @var{section} ]
20287 Compare data of section @var{section} on target to the exec file.
20288 Without the argument, all sections are compared.
20290 @subsubheading @value{GDBN} Command
20292 The @value{GDBN} equivalent is @samp{compare-sections}.
20294 @subsubheading Example
20298 @subheading The @code{-target-detach} Command
20299 @findex -target-detach
20301 @subsubheading Synopsis
20307 Disconnect from the remote target. There's no output.
20309 @subsubheading @value{GDBN} command
20311 The corresponding @value{GDBN} command is @samp{detach}.
20313 @subsubheading Example
20323 @subheading The @code{-target-disconnect} Command
20324 @findex -target-disconnect
20326 @subsubheading Synopsis
20332 Disconnect from the remote target. There's no output.
20334 @subsubheading @value{GDBN} command
20336 The corresponding @value{GDBN} command is @samp{disconnect}.
20338 @subsubheading Example
20348 @subheading The @code{-target-download} Command
20349 @findex -target-download
20351 @subsubheading Synopsis
20357 Loads the executable onto the remote target.
20358 It prints out an update message every half second, which includes the fields:
20362 The name of the section.
20364 The size of what has been sent so far for that section.
20366 The size of the section.
20368 The total size of what was sent so far (the current and the previous sections).
20370 The size of the overall executable to download.
20374 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
20375 @sc{gdb/mi} Output Syntax}).
20377 In addition, it prints the name and size of the sections, as they are
20378 downloaded. These messages include the following fields:
20382 The name of the section.
20384 The size of the section.
20386 The size of the overall executable to download.
20390 At the end, a summary is printed.
20392 @subsubheading @value{GDBN} Command
20394 The corresponding @value{GDBN} command is @samp{load}.
20396 @subsubheading Example
20398 Note: each status message appears on a single line. Here the messages
20399 have been broken down so that they can fit onto a page.
20404 +download,@{section=".text",section-size="6668",total-size="9880"@}
20405 +download,@{section=".text",section-sent="512",section-size="6668",
20406 total-sent="512",total-size="9880"@}
20407 +download,@{section=".text",section-sent="1024",section-size="6668",
20408 total-sent="1024",total-size="9880"@}
20409 +download,@{section=".text",section-sent="1536",section-size="6668",
20410 total-sent="1536",total-size="9880"@}
20411 +download,@{section=".text",section-sent="2048",section-size="6668",
20412 total-sent="2048",total-size="9880"@}
20413 +download,@{section=".text",section-sent="2560",section-size="6668",
20414 total-sent="2560",total-size="9880"@}
20415 +download,@{section=".text",section-sent="3072",section-size="6668",
20416 total-sent="3072",total-size="9880"@}
20417 +download,@{section=".text",section-sent="3584",section-size="6668",
20418 total-sent="3584",total-size="9880"@}
20419 +download,@{section=".text",section-sent="4096",section-size="6668",
20420 total-sent="4096",total-size="9880"@}
20421 +download,@{section=".text",section-sent="4608",section-size="6668",
20422 total-sent="4608",total-size="9880"@}
20423 +download,@{section=".text",section-sent="5120",section-size="6668",
20424 total-sent="5120",total-size="9880"@}
20425 +download,@{section=".text",section-sent="5632",section-size="6668",
20426 total-sent="5632",total-size="9880"@}
20427 +download,@{section=".text",section-sent="6144",section-size="6668",
20428 total-sent="6144",total-size="9880"@}
20429 +download,@{section=".text",section-sent="6656",section-size="6668",
20430 total-sent="6656",total-size="9880"@}
20431 +download,@{section=".init",section-size="28",total-size="9880"@}
20432 +download,@{section=".fini",section-size="28",total-size="9880"@}
20433 +download,@{section=".data",section-size="3156",total-size="9880"@}
20434 +download,@{section=".data",section-sent="512",section-size="3156",
20435 total-sent="7236",total-size="9880"@}
20436 +download,@{section=".data",section-sent="1024",section-size="3156",
20437 total-sent="7748",total-size="9880"@}
20438 +download,@{section=".data",section-sent="1536",section-size="3156",
20439 total-sent="8260",total-size="9880"@}
20440 +download,@{section=".data",section-sent="2048",section-size="3156",
20441 total-sent="8772",total-size="9880"@}
20442 +download,@{section=".data",section-sent="2560",section-size="3156",
20443 total-sent="9284",total-size="9880"@}
20444 +download,@{section=".data",section-sent="3072",section-size="3156",
20445 total-sent="9796",total-size="9880"@}
20446 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
20452 @subheading The @code{-target-exec-status} Command
20453 @findex -target-exec-status
20455 @subsubheading Synopsis
20458 -target-exec-status
20461 Provide information on the state of the target (whether it is running or
20462 not, for instance).
20464 @subsubheading @value{GDBN} Command
20466 There's no equivalent @value{GDBN} command.
20468 @subsubheading Example
20472 @subheading The @code{-target-list-available-targets} Command
20473 @findex -target-list-available-targets
20475 @subsubheading Synopsis
20478 -target-list-available-targets
20481 List the possible targets to connect to.
20483 @subsubheading @value{GDBN} Command
20485 The corresponding @value{GDBN} command is @samp{help target}.
20487 @subsubheading Example
20491 @subheading The @code{-target-list-current-targets} Command
20492 @findex -target-list-current-targets
20494 @subsubheading Synopsis
20497 -target-list-current-targets
20500 Describe the current target.
20502 @subsubheading @value{GDBN} Command
20504 The corresponding information is printed by @samp{info file} (among
20507 @subsubheading Example
20511 @subheading The @code{-target-list-parameters} Command
20512 @findex -target-list-parameters
20514 @subsubheading Synopsis
20517 -target-list-parameters
20522 @subsubheading @value{GDBN} Command
20526 @subsubheading Example
20530 @subheading The @code{-target-select} Command
20531 @findex -target-select
20533 @subsubheading Synopsis
20536 -target-select @var{type} @var{parameters @dots{}}
20539 Connect @value{GDBN} to the remote target. This command takes two args:
20543 The type of target, for instance @samp{async}, @samp{remote}, etc.
20544 @item @var{parameters}
20545 Device names, host names and the like. @xref{Target Commands, ,
20546 Commands for managing targets}, for more details.
20549 The output is a connection notification, followed by the address at
20550 which the target program is, in the following form:
20553 ^connected,addr="@var{address}",func="@var{function name}",
20554 args=[@var{arg list}]
20557 @subsubheading @value{GDBN} Command
20559 The corresponding @value{GDBN} command is @samp{target}.
20561 @subsubheading Example
20565 -target-select async /dev/ttya
20566 ^connected,addr="0xfe00a300",func="??",args=[]
20570 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20571 @node GDB/MI Thread Commands
20572 @section @sc{gdb/mi} Thread Commands
20575 @subheading The @code{-thread-info} Command
20576 @findex -thread-info
20578 @subsubheading Synopsis
20584 @subsubheading @value{GDBN} command
20588 @subsubheading Example
20592 @subheading The @code{-thread-list-all-threads} Command
20593 @findex -thread-list-all-threads
20595 @subsubheading Synopsis
20598 -thread-list-all-threads
20601 @subsubheading @value{GDBN} Command
20603 The equivalent @value{GDBN} command is @samp{info threads}.
20605 @subsubheading Example
20609 @subheading The @code{-thread-list-ids} Command
20610 @findex -thread-list-ids
20612 @subsubheading Synopsis
20618 Produces a list of the currently known @value{GDBN} thread ids. At the
20619 end of the list it also prints the total number of such threads.
20621 @subsubheading @value{GDBN} Command
20623 Part of @samp{info threads} supplies the same information.
20625 @subsubheading Example
20627 No threads present, besides the main process:
20632 ^done,thread-ids=@{@},number-of-threads="0"
20642 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20643 number-of-threads="3"
20648 @subheading The @code{-thread-select} Command
20649 @findex -thread-select
20651 @subsubheading Synopsis
20654 -thread-select @var{threadnum}
20657 Make @var{threadnum} the current thread. It prints the number of the new
20658 current thread, and the topmost frame for that thread.
20660 @subsubheading @value{GDBN} Command
20662 The corresponding @value{GDBN} command is @samp{thread}.
20664 @subsubheading Example
20671 *stopped,reason="end-stepping-range",thread-id="2",line="187",
20672 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
20676 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20677 number-of-threads="3"
20680 ^done,new-thread-id="3",
20681 frame=@{level="0",func="vprintf",
20682 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
20683 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
20687 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20688 @node GDB/MI Tracepoint Commands
20689 @section @sc{gdb/mi} Tracepoint Commands
20691 The tracepoint commands are not yet implemented.
20693 @c @subheading -trace-actions
20695 @c @subheading -trace-delete
20697 @c @subheading -trace-disable
20699 @c @subheading -trace-dump
20701 @c @subheading -trace-enable
20703 @c @subheading -trace-exists
20705 @c @subheading -trace-find
20707 @c @subheading -trace-frame-number
20709 @c @subheading -trace-info
20711 @c @subheading -trace-insert
20713 @c @subheading -trace-list
20715 @c @subheading -trace-pass-count
20717 @c @subheading -trace-save
20719 @c @subheading -trace-start
20721 @c @subheading -trace-stop
20724 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20725 @node GDB/MI Variable Objects
20726 @section @sc{gdb/mi} Variable Objects
20729 @subheading Motivation for Variable Objects in @sc{gdb/mi}
20731 For the implementation of a variable debugger window (locals, watched
20732 expressions, etc.), we are proposing the adaptation of the existing code
20733 used by @code{Insight}.
20735 The two main reasons for that are:
20739 It has been proven in practice (it is already on its second generation).
20742 It will shorten development time (needless to say how important it is
20746 The original interface was designed to be used by Tcl code, so it was
20747 slightly changed so it could be used through @sc{gdb/mi}. This section
20748 describes the @sc{gdb/mi} operations that will be available and gives some
20749 hints about their use.
20751 @emph{Note}: In addition to the set of operations described here, we
20752 expect the @sc{gui} implementation of a variable window to require, at
20753 least, the following operations:
20756 @item @code{-gdb-show} @code{output-radix}
20757 @item @code{-stack-list-arguments}
20758 @item @code{-stack-list-locals}
20759 @item @code{-stack-select-frame}
20762 @subheading Introduction to Variable Objects in @sc{gdb/mi}
20764 @cindex variable objects in @sc{gdb/mi}
20765 The basic idea behind variable objects is the creation of a named object
20766 to represent a variable, an expression, a memory location or even a CPU
20767 register. For each object created, a set of operations is available for
20768 examining or changing its properties.
20770 Furthermore, complex data types, such as C structures, are represented
20771 in a tree format. For instance, the @code{struct} type variable is the
20772 root and the children will represent the struct members. If a child
20773 is itself of a complex type, it will also have children of its own.
20774 Appropriate language differences are handled for C, C@t{++} and Java.
20776 When returning the actual values of the objects, this facility allows
20777 for the individual selection of the display format used in the result
20778 creation. It can be chosen among: binary, decimal, hexadecimal, octal
20779 and natural. Natural refers to a default format automatically
20780 chosen based on the variable type (like decimal for an @code{int}, hex
20781 for pointers, etc.).
20783 The following is the complete set of @sc{gdb/mi} operations defined to
20784 access this functionality:
20786 @multitable @columnfractions .4 .6
20787 @item @strong{Operation}
20788 @tab @strong{Description}
20790 @item @code{-var-create}
20791 @tab create a variable object
20792 @item @code{-var-delete}
20793 @tab delete the variable object and its children
20794 @item @code{-var-set-format}
20795 @tab set the display format of this variable
20796 @item @code{-var-show-format}
20797 @tab show the display format of this variable
20798 @item @code{-var-info-num-children}
20799 @tab tells how many children this object has
20800 @item @code{-var-list-children}
20801 @tab return a list of the object's children
20802 @item @code{-var-info-type}
20803 @tab show the type of this variable object
20804 @item @code{-var-info-expression}
20805 @tab print what this variable object represents
20806 @item @code{-var-show-attributes}
20807 @tab is this variable editable? does it exist here?
20808 @item @code{-var-evaluate-expression}
20809 @tab get the value of this variable
20810 @item @code{-var-assign}
20811 @tab set the value of this variable
20812 @item @code{-var-update}
20813 @tab update the variable and its children
20816 In the next subsection we describe each operation in detail and suggest
20817 how it can be used.
20819 @subheading Description And Use of Operations on Variable Objects
20821 @subheading The @code{-var-create} Command
20822 @findex -var-create
20824 @subsubheading Synopsis
20827 -var-create @{@var{name} | "-"@}
20828 @{@var{frame-addr} | "*"@} @var{expression}
20831 This operation creates a variable object, which allows the monitoring of
20832 a variable, the result of an expression, a memory cell or a CPU
20835 The @var{name} parameter is the string by which the object can be
20836 referenced. It must be unique. If @samp{-} is specified, the varobj
20837 system will generate a string ``varNNNNNN'' automatically. It will be
20838 unique provided that one does not specify @var{name} on that format.
20839 The command fails if a duplicate name is found.
20841 The frame under which the expression should be evaluated can be
20842 specified by @var{frame-addr}. A @samp{*} indicates that the current
20843 frame should be used.
20845 @var{expression} is any expression valid on the current language set (must not
20846 begin with a @samp{*}), or one of the following:
20850 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
20853 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
20856 @samp{$@var{regname}} --- a CPU register name
20859 @subsubheading Result
20861 This operation returns the name, number of children and the type of the
20862 object created. Type is returned as a string as the ones generated by
20863 the @value{GDBN} CLI:
20866 name="@var{name}",numchild="N",type="@var{type}"
20870 @subheading The @code{-var-delete} Command
20871 @findex -var-delete
20873 @subsubheading Synopsis
20876 -var-delete @var{name}
20879 Deletes a previously created variable object and all of its children.
20881 Returns an error if the object @var{name} is not found.
20884 @subheading The @code{-var-set-format} Command
20885 @findex -var-set-format
20887 @subsubheading Synopsis
20890 -var-set-format @var{name} @var{format-spec}
20893 Sets the output format for the value of the object @var{name} to be
20896 The syntax for the @var{format-spec} is as follows:
20899 @var{format-spec} @expansion{}
20900 @{binary | decimal | hexadecimal | octal | natural@}
20904 @subheading The @code{-var-show-format} Command
20905 @findex -var-show-format
20907 @subsubheading Synopsis
20910 -var-show-format @var{name}
20913 Returns the format used to display the value of the object @var{name}.
20916 @var{format} @expansion{}
20921 @subheading The @code{-var-info-num-children} Command
20922 @findex -var-info-num-children
20924 @subsubheading Synopsis
20927 -var-info-num-children @var{name}
20930 Returns the number of children of a variable object @var{name}:
20937 @subheading The @code{-var-list-children} Command
20938 @findex -var-list-children
20940 @subsubheading Synopsis
20943 -var-list-children [@var{print-values}] @var{name}
20945 @anchor{-var-list-children}
20947 Return a list of the children of the specified variable object and
20948 create variable objects for them, if they do not already exist. With
20949 a single argument or if @var{print-values} has a value for of 0 or
20950 @code{--no-values}, print only the names of the variables; if
20951 @var{print-values} is 1 or @code{--all-values}, also print their
20952 values; and if it is 2 or @code{--simple-values} print the name and
20953 value for simple data types and just the name for arrays, structures
20956 @subsubheading Example
20960 -var-list-children n
20961 ^done,numchild=@var{n},children=[@{name=@var{name},
20962 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
20964 -var-list-children --all-values n
20965 ^done,numchild=@var{n},children=[@{name=@var{name},
20966 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
20970 @subheading The @code{-var-info-type} Command
20971 @findex -var-info-type
20973 @subsubheading Synopsis
20976 -var-info-type @var{name}
20979 Returns the type of the specified variable @var{name}. The type is
20980 returned as a string in the same format as it is output by the
20984 type=@var{typename}
20988 @subheading The @code{-var-info-expression} Command
20989 @findex -var-info-expression
20991 @subsubheading Synopsis
20994 -var-info-expression @var{name}
20997 Returns what is represented by the variable object @var{name}:
21000 lang=@var{lang-spec},exp=@var{expression}
21004 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
21006 @subheading The @code{-var-show-attributes} Command
21007 @findex -var-show-attributes
21009 @subsubheading Synopsis
21012 -var-show-attributes @var{name}
21015 List attributes of the specified variable object @var{name}:
21018 status=@var{attr} [ ( ,@var{attr} )* ]
21022 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
21024 @subheading The @code{-var-evaluate-expression} Command
21025 @findex -var-evaluate-expression
21027 @subsubheading Synopsis
21030 -var-evaluate-expression @var{name}
21033 Evaluates the expression that is represented by the specified variable
21034 object and returns its value as a string in the current format specified
21041 Note that one must invoke @code{-var-list-children} for a variable
21042 before the value of a child variable can be evaluated.
21044 @subheading The @code{-var-assign} Command
21045 @findex -var-assign
21047 @subsubheading Synopsis
21050 -var-assign @var{name} @var{expression}
21053 Assigns the value of @var{expression} to the variable object specified
21054 by @var{name}. The object must be @samp{editable}. If the variable's
21055 value is altered by the assign, the variable will show up in any
21056 subsequent @code{-var-update} list.
21058 @subsubheading Example
21066 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
21070 @subheading The @code{-var-update} Command
21071 @findex -var-update
21073 @subsubheading Synopsis
21076 -var-update [@var{print-values}] @{@var{name} | "*"@}
21079 Update the value of the variable object @var{name} by evaluating its
21080 expression after fetching all the new values from memory or registers.
21081 A @samp{*} causes all existing variable objects to be updated. The
21082 option @var{print-values} determines whether names both and values, or
21083 just names are printed in the manner described for
21084 @code{-var-list-children} (@pxref{-var-list-children}).
21086 @subsubheading Example
21093 -var-update --all-values var1
21094 ^done,changelist=[@{name="var1",value="3",in_scope="true",
21095 type_changed="false"@}]
21100 @chapter @value{GDBN} Annotations
21102 This chapter describes annotations in @value{GDBN}. Annotations were
21103 designed to interface @value{GDBN} to graphical user interfaces or other
21104 similar programs which want to interact with @value{GDBN} at a
21105 relatively high level.
21107 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
21111 This is Edition @value{EDITION}, @value{DATE}.
21115 * Annotations Overview:: What annotations are; the general syntax.
21116 * Prompting:: Annotations marking @value{GDBN}'s need for input.
21117 * Errors:: Annotations for error messages.
21118 * Invalidation:: Some annotations describe things now invalid.
21119 * Annotations for Running::
21120 Whether the program is running, how it stopped, etc.
21121 * Source Annotations:: Annotations describing source code.
21124 @node Annotations Overview
21125 @section What is an Annotation?
21126 @cindex annotations
21128 Annotations start with a newline character, two @samp{control-z}
21129 characters, and the name of the annotation. If there is no additional
21130 information associated with this annotation, the name of the annotation
21131 is followed immediately by a newline. If there is additional
21132 information, the name of the annotation is followed by a space, the
21133 additional information, and a newline. The additional information
21134 cannot contain newline characters.
21136 Any output not beginning with a newline and two @samp{control-z}
21137 characters denotes literal output from @value{GDBN}. Currently there is
21138 no need for @value{GDBN} to output a newline followed by two
21139 @samp{control-z} characters, but if there was such a need, the
21140 annotations could be extended with an @samp{escape} annotation which
21141 means those three characters as output.
21143 The annotation @var{level}, which is specified using the
21144 @option{--annotate} command line option (@pxref{Mode Options}), controls
21145 how much information @value{GDBN} prints together with its prompt,
21146 values of expressions, source lines, and other types of output. Level 0
21147 is for no anntations, level 1 is for use when @value{GDBN} is run as a
21148 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
21149 for programs that control @value{GDBN}, and level 2 annotations have
21150 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
21151 Interface, annotate, GDB's Obsolete Annotations}).
21154 @kindex set annotate
21155 @item set annotate @var{level}
21156 The @value{GDBN} command @code{set annotate} sets the level of
21157 annotations to the specified @var{level}.
21159 @item show annotate
21160 @kindex show annotate
21161 Show the current annotation level.
21164 This chapter describes level 3 annotations.
21166 A simple example of starting up @value{GDBN} with annotations is:
21169 $ @kbd{gdb --annotate=3}
21171 Copyright 2003 Free Software Foundation, Inc.
21172 GDB is free software, covered by the GNU General Public License,
21173 and you are welcome to change it and/or distribute copies of it
21174 under certain conditions.
21175 Type "show copying" to see the conditions.
21176 There is absolutely no warranty for GDB. Type "show warranty"
21178 This GDB was configured as "i386-pc-linux-gnu"
21189 Here @samp{quit} is input to @value{GDBN}; the rest is output from
21190 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
21191 denotes a @samp{control-z} character) are annotations; the rest is
21192 output from @value{GDBN}.
21195 @section Annotation for @value{GDBN} Input
21197 @cindex annotations for prompts
21198 When @value{GDBN} prompts for input, it annotates this fact so it is possible
21199 to know when to send output, when the output from a given command is
21202 Different kinds of input each have a different @dfn{input type}. Each
21203 input type has three annotations: a @code{pre-} annotation, which
21204 denotes the beginning of any prompt which is being output, a plain
21205 annotation, which denotes the end of the prompt, and then a @code{post-}
21206 annotation which denotes the end of any echo which may (or may not) be
21207 associated with the input. For example, the @code{prompt} input type
21208 features the following annotations:
21216 The input types are
21221 @findex post-prompt
21223 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
21225 @findex pre-commands
21227 @findex post-commands
21229 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
21230 command. The annotations are repeated for each command which is input.
21232 @findex pre-overload-choice
21233 @findex overload-choice
21234 @findex post-overload-choice
21235 @item overload-choice
21236 When @value{GDBN} wants the user to select between various overloaded functions.
21242 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
21244 @findex pre-prompt-for-continue
21245 @findex prompt-for-continue
21246 @findex post-prompt-for-continue
21247 @item prompt-for-continue
21248 When @value{GDBN} is asking the user to press return to continue. Note: Don't
21249 expect this to work well; instead use @code{set height 0} to disable
21250 prompting. This is because the counting of lines is buggy in the
21251 presence of annotations.
21256 @cindex annotations for errors, warnings and interrupts
21263 This annotation occurs right before @value{GDBN} responds to an interrupt.
21270 This annotation occurs right before @value{GDBN} responds to an error.
21272 Quit and error annotations indicate that any annotations which @value{GDBN} was
21273 in the middle of may end abruptly. For example, if a
21274 @code{value-history-begin} annotation is followed by a @code{error}, one
21275 cannot expect to receive the matching @code{value-history-end}. One
21276 cannot expect not to receive it either, however; an error annotation
21277 does not necessarily mean that @value{GDBN} is immediately returning all the way
21280 @findex error-begin
21281 A quit or error annotation may be preceded by
21287 Any output between that and the quit or error annotation is the error
21290 Warning messages are not yet annotated.
21291 @c If we want to change that, need to fix warning(), type_error(),
21292 @c range_error(), and possibly other places.
21295 @section Invalidation Notices
21297 @cindex annotations for invalidation messages
21298 The following annotations say that certain pieces of state may have
21302 @findex frames-invalid
21303 @item ^Z^Zframes-invalid
21305 The frames (for example, output from the @code{backtrace} command) may
21308 @findex breakpoints-invalid
21309 @item ^Z^Zbreakpoints-invalid
21311 The breakpoints may have changed. For example, the user just added or
21312 deleted a breakpoint.
21315 @node Annotations for Running
21316 @section Running the Program
21317 @cindex annotations for running programs
21321 When the program starts executing due to a @value{GDBN} command such as
21322 @code{step} or @code{continue},
21328 is output. When the program stops,
21334 is output. Before the @code{stopped} annotation, a variety of
21335 annotations describe how the program stopped.
21339 @item ^Z^Zexited @var{exit-status}
21340 The program exited, and @var{exit-status} is the exit status (zero for
21341 successful exit, otherwise nonzero).
21344 @findex signal-name
21345 @findex signal-name-end
21346 @findex signal-string
21347 @findex signal-string-end
21348 @item ^Z^Zsignalled
21349 The program exited with a signal. After the @code{^Z^Zsignalled}, the
21350 annotation continues:
21356 ^Z^Zsignal-name-end
21360 ^Z^Zsignal-string-end
21365 where @var{name} is the name of the signal, such as @code{SIGILL} or
21366 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
21367 as @code{Illegal Instruction} or @code{Segmentation fault}.
21368 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
21369 user's benefit and have no particular format.
21373 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
21374 just saying that the program received the signal, not that it was
21375 terminated with it.
21378 @item ^Z^Zbreakpoint @var{number}
21379 The program hit breakpoint number @var{number}.
21382 @item ^Z^Zwatchpoint @var{number}
21383 The program hit watchpoint number @var{number}.
21386 @node Source Annotations
21387 @section Displaying Source
21388 @cindex annotations for source display
21391 The following annotation is used instead of displaying source code:
21394 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
21397 where @var{filename} is an absolute file name indicating which source
21398 file, @var{line} is the line number within that file (where 1 is the
21399 first line in the file), @var{character} is the character position
21400 within the file (where 0 is the first character in the file) (for most
21401 debug formats this will necessarily point to the beginning of a line),
21402 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
21403 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
21404 @var{addr} is the address in the target program associated with the
21405 source which is being displayed. @var{addr} is in the form @samp{0x}
21406 followed by one or more lowercase hex digits (note that this does not
21407 depend on the language).
21410 @chapter Reporting Bugs in @value{GDBN}
21411 @cindex bugs in @value{GDBN}
21412 @cindex reporting bugs in @value{GDBN}
21414 Your bug reports play an essential role in making @value{GDBN} reliable.
21416 Reporting a bug may help you by bringing a solution to your problem, or it
21417 may not. But in any case the principal function of a bug report is to help
21418 the entire community by making the next version of @value{GDBN} work better. Bug
21419 reports are your contribution to the maintenance of @value{GDBN}.
21421 In order for a bug report to serve its purpose, you must include the
21422 information that enables us to fix the bug.
21425 * Bug Criteria:: Have you found a bug?
21426 * Bug Reporting:: How to report bugs
21430 @section Have you found a bug?
21431 @cindex bug criteria
21433 If you are not sure whether you have found a bug, here are some guidelines:
21436 @cindex fatal signal
21437 @cindex debugger crash
21438 @cindex crash of debugger
21440 If the debugger gets a fatal signal, for any input whatever, that is a
21441 @value{GDBN} bug. Reliable debuggers never crash.
21443 @cindex error on valid input
21445 If @value{GDBN} produces an error message for valid input, that is a
21446 bug. (Note that if you're cross debugging, the problem may also be
21447 somewhere in the connection to the target.)
21449 @cindex invalid input
21451 If @value{GDBN} does not produce an error message for invalid input,
21452 that is a bug. However, you should note that your idea of
21453 ``invalid input'' might be our idea of ``an extension'' or ``support
21454 for traditional practice''.
21457 If you are an experienced user of debugging tools, your suggestions
21458 for improvement of @value{GDBN} are welcome in any case.
21461 @node Bug Reporting
21462 @section How to report bugs
21463 @cindex bug reports
21464 @cindex @value{GDBN} bugs, reporting
21466 A number of companies and individuals offer support for @sc{gnu} products.
21467 If you obtained @value{GDBN} from a support organization, we recommend you
21468 contact that organization first.
21470 You can find contact information for many support companies and
21471 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
21473 @c should add a web page ref...
21475 In any event, we also recommend that you submit bug reports for
21476 @value{GDBN}. The prefered method is to submit them directly using
21477 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
21478 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
21481 @strong{Do not send bug reports to @samp{info-gdb}, or to
21482 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
21483 not want to receive bug reports. Those that do have arranged to receive
21486 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
21487 serves as a repeater. The mailing list and the newsgroup carry exactly
21488 the same messages. Often people think of posting bug reports to the
21489 newsgroup instead of mailing them. This appears to work, but it has one
21490 problem which can be crucial: a newsgroup posting often lacks a mail
21491 path back to the sender. Thus, if we need to ask for more information,
21492 we may be unable to reach you. For this reason, it is better to send
21493 bug reports to the mailing list.
21495 The fundamental principle of reporting bugs usefully is this:
21496 @strong{report all the facts}. If you are not sure whether to state a
21497 fact or leave it out, state it!
21499 Often people omit facts because they think they know what causes the
21500 problem and assume that some details do not matter. Thus, you might
21501 assume that the name of the variable you use in an example does not matter.
21502 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
21503 stray memory reference which happens to fetch from the location where that
21504 name is stored in memory; perhaps, if the name were different, the contents
21505 of that location would fool the debugger into doing the right thing despite
21506 the bug. Play it safe and give a specific, complete example. That is the
21507 easiest thing for you to do, and the most helpful.
21509 Keep in mind that the purpose of a bug report is to enable us to fix the
21510 bug. It may be that the bug has been reported previously, but neither
21511 you nor we can know that unless your bug report is complete and
21514 Sometimes people give a few sketchy facts and ask, ``Does this ring a
21515 bell?'' Those bug reports are useless, and we urge everyone to
21516 @emph{refuse to respond to them} except to chide the sender to report
21519 To enable us to fix the bug, you should include all these things:
21523 The version of @value{GDBN}. @value{GDBN} announces it if you start
21524 with no arguments; you can also print it at any time using @code{show
21527 Without this, we will not know whether there is any point in looking for
21528 the bug in the current version of @value{GDBN}.
21531 The type of machine you are using, and the operating system name and
21535 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
21536 ``@value{GCC}--2.8.1''.
21539 What compiler (and its version) was used to compile the program you are
21540 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
21541 C Compiler''. For GCC, you can say @code{gcc --version} to get this
21542 information; for other compilers, see the documentation for those
21546 The command arguments you gave the compiler to compile your example and
21547 observe the bug. For example, did you use @samp{-O}? To guarantee
21548 you will not omit something important, list them all. A copy of the
21549 Makefile (or the output from make) is sufficient.
21551 If we were to try to guess the arguments, we would probably guess wrong
21552 and then we might not encounter the bug.
21555 A complete input script, and all necessary source files, that will
21559 A description of what behavior you observe that you believe is
21560 incorrect. For example, ``It gets a fatal signal.''
21562 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
21563 will certainly notice it. But if the bug is incorrect output, we might
21564 not notice unless it is glaringly wrong. You might as well not give us
21565 a chance to make a mistake.
21567 Even if the problem you experience is a fatal signal, you should still
21568 say so explicitly. Suppose something strange is going on, such as, your
21569 copy of @value{GDBN} is out of synch, or you have encountered a bug in
21570 the C library on your system. (This has happened!) Your copy might
21571 crash and ours would not. If you told us to expect a crash, then when
21572 ours fails to crash, we would know that the bug was not happening for
21573 us. If you had not told us to expect a crash, then we would not be able
21574 to draw any conclusion from our observations.
21577 @cindex recording a session script
21578 To collect all this information, you can use a session recording program
21579 such as @command{script}, which is available on many Unix systems.
21580 Just run your @value{GDBN} session inside @command{script} and then
21581 include the @file{typescript} file with your bug report.
21583 Another way to record a @value{GDBN} session is to run @value{GDBN}
21584 inside Emacs and then save the entire buffer to a file.
21587 If you wish to suggest changes to the @value{GDBN} source, send us context
21588 diffs. If you even discuss something in the @value{GDBN} source, refer to
21589 it by context, not by line number.
21591 The line numbers in our development sources will not match those in your
21592 sources. Your line numbers would convey no useful information to us.
21596 Here are some things that are not necessary:
21600 A description of the envelope of the bug.
21602 Often people who encounter a bug spend a lot of time investigating
21603 which changes to the input file will make the bug go away and which
21604 changes will not affect it.
21606 This is often time consuming and not very useful, because the way we
21607 will find the bug is by running a single example under the debugger
21608 with breakpoints, not by pure deduction from a series of examples.
21609 We recommend that you save your time for something else.
21611 Of course, if you can find a simpler example to report @emph{instead}
21612 of the original one, that is a convenience for us. Errors in the
21613 output will be easier to spot, running under the debugger will take
21614 less time, and so on.
21616 However, simplification is not vital; if you do not want to do this,
21617 report the bug anyway and send us the entire test case you used.
21620 A patch for the bug.
21622 A patch for the bug does help us if it is a good one. But do not omit
21623 the necessary information, such as the test case, on the assumption that
21624 a patch is all we need. We might see problems with your patch and decide
21625 to fix the problem another way, or we might not understand it at all.
21627 Sometimes with a program as complicated as @value{GDBN} it is very hard to
21628 construct an example that will make the program follow a certain path
21629 through the code. If you do not send us the example, we will not be able
21630 to construct one, so we will not be able to verify that the bug is fixed.
21632 And if we cannot understand what bug you are trying to fix, or why your
21633 patch should be an improvement, we will not install it. A test case will
21634 help us to understand.
21637 A guess about what the bug is or what it depends on.
21639 Such guesses are usually wrong. Even we cannot guess right about such
21640 things without first using the debugger to find the facts.
21643 @c The readline documentation is distributed with the readline code
21644 @c and consists of the two following files:
21646 @c inc-hist.texinfo
21647 @c Use -I with makeinfo to point to the appropriate directory,
21648 @c environment var TEXINPUTS with TeX.
21649 @include rluser.texinfo
21650 @include inc-hist.texinfo
21653 @node Formatting Documentation
21654 @appendix Formatting Documentation
21656 @cindex @value{GDBN} reference card
21657 @cindex reference card
21658 The @value{GDBN} 4 release includes an already-formatted reference card, ready
21659 for printing with PostScript or Ghostscript, in the @file{gdb}
21660 subdirectory of the main source directory@footnote{In
21661 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
21662 release.}. If you can use PostScript or Ghostscript with your printer,
21663 you can print the reference card immediately with @file{refcard.ps}.
21665 The release also includes the source for the reference card. You
21666 can format it, using @TeX{}, by typing:
21672 The @value{GDBN} reference card is designed to print in @dfn{landscape}
21673 mode on US ``letter'' size paper;
21674 that is, on a sheet 11 inches wide by 8.5 inches
21675 high. You will need to specify this form of printing as an option to
21676 your @sc{dvi} output program.
21678 @cindex documentation
21680 All the documentation for @value{GDBN} comes as part of the machine-readable
21681 distribution. The documentation is written in Texinfo format, which is
21682 a documentation system that uses a single source file to produce both
21683 on-line information and a printed manual. You can use one of the Info
21684 formatting commands to create the on-line version of the documentation
21685 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
21687 @value{GDBN} includes an already formatted copy of the on-line Info
21688 version of this manual in the @file{gdb} subdirectory. The main Info
21689 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
21690 subordinate files matching @samp{gdb.info*} in the same directory. If
21691 necessary, you can print out these files, or read them with any editor;
21692 but they are easier to read using the @code{info} subsystem in @sc{gnu}
21693 Emacs or the standalone @code{info} program, available as part of the
21694 @sc{gnu} Texinfo distribution.
21696 If you want to format these Info files yourself, you need one of the
21697 Info formatting programs, such as @code{texinfo-format-buffer} or
21700 If you have @code{makeinfo} installed, and are in the top level
21701 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
21702 version @value{GDBVN}), you can make the Info file by typing:
21709 If you want to typeset and print copies of this manual, you need @TeX{},
21710 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
21711 Texinfo definitions file.
21713 @TeX{} is a typesetting program; it does not print files directly, but
21714 produces output files called @sc{dvi} files. To print a typeset
21715 document, you need a program to print @sc{dvi} files. If your system
21716 has @TeX{} installed, chances are it has such a program. The precise
21717 command to use depends on your system; @kbd{lpr -d} is common; another
21718 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
21719 require a file name without any extension or a @samp{.dvi} extension.
21721 @TeX{} also requires a macro definitions file called
21722 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
21723 written in Texinfo format. On its own, @TeX{} cannot either read or
21724 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
21725 and is located in the @file{gdb-@var{version-number}/texinfo}
21728 If you have @TeX{} and a @sc{dvi} printer program installed, you can
21729 typeset and print this manual. First switch to the the @file{gdb}
21730 subdirectory of the main source directory (for example, to
21731 @file{gdb-@value{GDBVN}/gdb}) and type:
21737 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
21739 @node Installing GDB
21740 @appendix Installing @value{GDBN}
21741 @cindex configuring @value{GDBN}
21742 @cindex installation
21743 @cindex configuring @value{GDBN}, and source tree subdirectories
21745 @value{GDBN} comes with a @code{configure} script that automates the process
21746 of preparing @value{GDBN} for installation; you can then use @code{make} to
21747 build the @code{gdb} program.
21749 @c irrelevant in info file; it's as current as the code it lives with.
21750 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
21751 look at the @file{README} file in the sources; we may have improved the
21752 installation procedures since publishing this manual.}
21755 The @value{GDBN} distribution includes all the source code you need for
21756 @value{GDBN} in a single directory, whose name is usually composed by
21757 appending the version number to @samp{gdb}.
21759 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
21760 @file{gdb-@value{GDBVN}} directory. That directory contains:
21763 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
21764 script for configuring @value{GDBN} and all its supporting libraries
21766 @item gdb-@value{GDBVN}/gdb
21767 the source specific to @value{GDBN} itself
21769 @item gdb-@value{GDBVN}/bfd
21770 source for the Binary File Descriptor library
21772 @item gdb-@value{GDBVN}/include
21773 @sc{gnu} include files
21775 @item gdb-@value{GDBVN}/libiberty
21776 source for the @samp{-liberty} free software library
21778 @item gdb-@value{GDBVN}/opcodes
21779 source for the library of opcode tables and disassemblers
21781 @item gdb-@value{GDBVN}/readline
21782 source for the @sc{gnu} command-line interface
21784 @item gdb-@value{GDBVN}/glob
21785 source for the @sc{gnu} filename pattern-matching subroutine
21787 @item gdb-@value{GDBVN}/mmalloc
21788 source for the @sc{gnu} memory-mapped malloc package
21791 The simplest way to configure and build @value{GDBN} is to run @code{configure}
21792 from the @file{gdb-@var{version-number}} source directory, which in
21793 this example is the @file{gdb-@value{GDBVN}} directory.
21795 First switch to the @file{gdb-@var{version-number}} source directory
21796 if you are not already in it; then run @code{configure}. Pass the
21797 identifier for the platform on which @value{GDBN} will run as an
21803 cd gdb-@value{GDBVN}
21804 ./configure @var{host}
21809 where @var{host} is an identifier such as @samp{sun4} or
21810 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
21811 (You can often leave off @var{host}; @code{configure} tries to guess the
21812 correct value by examining your system.)
21814 Running @samp{configure @var{host}} and then running @code{make} builds the
21815 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
21816 libraries, then @code{gdb} itself. The configured source files, and the
21817 binaries, are left in the corresponding source directories.
21820 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
21821 system does not recognize this automatically when you run a different
21822 shell, you may need to run @code{sh} on it explicitly:
21825 sh configure @var{host}
21828 If you run @code{configure} from a directory that contains source
21829 directories for multiple libraries or programs, such as the
21830 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
21831 creates configuration files for every directory level underneath (unless
21832 you tell it not to, with the @samp{--norecursion} option).
21834 You should run the @code{configure} script from the top directory in the
21835 source tree, the @file{gdb-@var{version-number}} directory. If you run
21836 @code{configure} from one of the subdirectories, you will configure only
21837 that subdirectory. That is usually not what you want. In particular,
21838 if you run the first @code{configure} from the @file{gdb} subdirectory
21839 of the @file{gdb-@var{version-number}} directory, you will omit the
21840 configuration of @file{bfd}, @file{readline}, and other sibling
21841 directories of the @file{gdb} subdirectory. This leads to build errors
21842 about missing include files such as @file{bfd/bfd.h}.
21844 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
21845 However, you should make sure that the shell on your path (named by
21846 the @samp{SHELL} environment variable) is publicly readable. Remember
21847 that @value{GDBN} uses the shell to start your program---some systems refuse to
21848 let @value{GDBN} debug child processes whose programs are not readable.
21851 * Separate Objdir:: Compiling @value{GDBN} in another directory
21852 * Config Names:: Specifying names for hosts and targets
21853 * Configure Options:: Summary of options for configure
21856 @node Separate Objdir
21857 @section Compiling @value{GDBN} in another directory
21859 If you want to run @value{GDBN} versions for several host or target machines,
21860 you need a different @code{gdb} compiled for each combination of
21861 host and target. @code{configure} is designed to make this easy by
21862 allowing you to generate each configuration in a separate subdirectory,
21863 rather than in the source directory. If your @code{make} program
21864 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
21865 @code{make} in each of these directories builds the @code{gdb}
21866 program specified there.
21868 To build @code{gdb} in a separate directory, run @code{configure}
21869 with the @samp{--srcdir} option to specify where to find the source.
21870 (You also need to specify a path to find @code{configure}
21871 itself from your working directory. If the path to @code{configure}
21872 would be the same as the argument to @samp{--srcdir}, you can leave out
21873 the @samp{--srcdir} option; it is assumed.)
21875 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
21876 separate directory for a Sun 4 like this:
21880 cd gdb-@value{GDBVN}
21883 ../gdb-@value{GDBVN}/configure sun4
21888 When @code{configure} builds a configuration using a remote source
21889 directory, it creates a tree for the binaries with the same structure
21890 (and using the same names) as the tree under the source directory. In
21891 the example, you'd find the Sun 4 library @file{libiberty.a} in the
21892 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
21893 @file{gdb-sun4/gdb}.
21895 Make sure that your path to the @file{configure} script has just one
21896 instance of @file{gdb} in it. If your path to @file{configure} looks
21897 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
21898 one subdirectory of @value{GDBN}, not the whole package. This leads to
21899 build errors about missing include files such as @file{bfd/bfd.h}.
21901 One popular reason to build several @value{GDBN} configurations in separate
21902 directories is to configure @value{GDBN} for cross-compiling (where
21903 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
21904 programs that run on another machine---the @dfn{target}).
21905 You specify a cross-debugging target by
21906 giving the @samp{--target=@var{target}} option to @code{configure}.
21908 When you run @code{make} to build a program or library, you must run
21909 it in a configured directory---whatever directory you were in when you
21910 called @code{configure} (or one of its subdirectories).
21912 The @code{Makefile} that @code{configure} generates in each source
21913 directory also runs recursively. If you type @code{make} in a source
21914 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
21915 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
21916 will build all the required libraries, and then build GDB.
21918 When you have multiple hosts or targets configured in separate
21919 directories, you can run @code{make} on them in parallel (for example,
21920 if they are NFS-mounted on each of the hosts); they will not interfere
21924 @section Specifying names for hosts and targets
21926 The specifications used for hosts and targets in the @code{configure}
21927 script are based on a three-part naming scheme, but some short predefined
21928 aliases are also supported. The full naming scheme encodes three pieces
21929 of information in the following pattern:
21932 @var{architecture}-@var{vendor}-@var{os}
21935 For example, you can use the alias @code{sun4} as a @var{host} argument,
21936 or as the value for @var{target} in a @code{--target=@var{target}}
21937 option. The equivalent full name is @samp{sparc-sun-sunos4}.
21939 The @code{configure} script accompanying @value{GDBN} does not provide
21940 any query facility to list all supported host and target names or
21941 aliases. @code{configure} calls the Bourne shell script
21942 @code{config.sub} to map abbreviations to full names; you can read the
21943 script, if you wish, or you can use it to test your guesses on
21944 abbreviations---for example:
21947 % sh config.sub i386-linux
21949 % sh config.sub alpha-linux
21950 alpha-unknown-linux-gnu
21951 % sh config.sub hp9k700
21953 % sh config.sub sun4
21954 sparc-sun-sunos4.1.1
21955 % sh config.sub sun3
21956 m68k-sun-sunos4.1.1
21957 % sh config.sub i986v
21958 Invalid configuration `i986v': machine `i986v' not recognized
21962 @code{config.sub} is also distributed in the @value{GDBN} source
21963 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
21965 @node Configure Options
21966 @section @code{configure} options
21968 Here is a summary of the @code{configure} options and arguments that
21969 are most often useful for building @value{GDBN}. @code{configure} also has
21970 several other options not listed here. @inforef{What Configure
21971 Does,,configure.info}, for a full explanation of @code{configure}.
21974 configure @r{[}--help@r{]}
21975 @r{[}--prefix=@var{dir}@r{]}
21976 @r{[}--exec-prefix=@var{dir}@r{]}
21977 @r{[}--srcdir=@var{dirname}@r{]}
21978 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
21979 @r{[}--target=@var{target}@r{]}
21984 You may introduce options with a single @samp{-} rather than
21985 @samp{--} if you prefer; but you may abbreviate option names if you use
21990 Display a quick summary of how to invoke @code{configure}.
21992 @item --prefix=@var{dir}
21993 Configure the source to install programs and files under directory
21996 @item --exec-prefix=@var{dir}
21997 Configure the source to install programs under directory
22000 @c avoid splitting the warning from the explanation:
22002 @item --srcdir=@var{dirname}
22003 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
22004 @code{make} that implements the @code{VPATH} feature.}@*
22005 Use this option to make configurations in directories separate from the
22006 @value{GDBN} source directories. Among other things, you can use this to
22007 build (or maintain) several configurations simultaneously, in separate
22008 directories. @code{configure} writes configuration specific files in
22009 the current directory, but arranges for them to use the source in the
22010 directory @var{dirname}. @code{configure} creates directories under
22011 the working directory in parallel to the source directories below
22014 @item --norecursion
22015 Configure only the directory level where @code{configure} is executed; do not
22016 propagate configuration to subdirectories.
22018 @item --target=@var{target}
22019 Configure @value{GDBN} for cross-debugging programs running on the specified
22020 @var{target}. Without this option, @value{GDBN} is configured to debug
22021 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
22023 There is no convenient way to generate a list of all available targets.
22025 @item @var{host} @dots{}
22026 Configure @value{GDBN} to run on the specified @var{host}.
22028 There is no convenient way to generate a list of all available hosts.
22031 There are many other options available as well, but they are generally
22032 needed for special purposes only.
22034 @node Maintenance Commands
22035 @appendix Maintenance Commands
22036 @cindex maintenance commands
22037 @cindex internal commands
22039 In addition to commands intended for @value{GDBN} users, @value{GDBN}
22040 includes a number of commands intended for @value{GDBN} developers,
22041 that are not documented elsewhere in this manual. These commands are
22042 provided here for reference. (For commands that turn on debugging
22043 messages, see @ref{Debugging Output}.)
22046 @kindex maint agent
22047 @item maint agent @var{expression}
22048 Translate the given @var{expression} into remote agent bytecodes.
22049 This command is useful for debugging the Agent Expression mechanism
22050 (@pxref{Agent Expressions}).
22052 @kindex maint info breakpoints
22053 @item @anchor{maint info breakpoints}maint info breakpoints
22054 Using the same format as @samp{info breakpoints}, display both the
22055 breakpoints you've set explicitly, and those @value{GDBN} is using for
22056 internal purposes. Internal breakpoints are shown with negative
22057 breakpoint numbers. The type column identifies what kind of breakpoint
22062 Normal, explicitly set breakpoint.
22065 Normal, explicitly set watchpoint.
22068 Internal breakpoint, used to handle correctly stepping through
22069 @code{longjmp} calls.
22071 @item longjmp resume
22072 Internal breakpoint at the target of a @code{longjmp}.
22075 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
22078 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
22081 Shared library events.
22085 @kindex maint check-symtabs
22086 @item maint check-symtabs
22087 Check the consistency of psymtabs and symtabs.
22089 @kindex maint cplus first_component
22090 @item maint cplus first_component @var{name}
22091 Print the first C@t{++} class/namespace component of @var{name}.
22093 @kindex maint cplus namespace
22094 @item maint cplus namespace
22095 Print the list of possible C@t{++} namespaces.
22097 @kindex maint demangle
22098 @item maint demangle @var{name}
22099 Demangle a C@t{++} or Objective-C manled @var{name}.
22101 @kindex maint deprecate
22102 @kindex maint undeprecate
22103 @cindex deprecated commands
22104 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
22105 @itemx maint undeprecate @var{command}
22106 Deprecate or undeprecate the named @var{command}. Deprecated commands
22107 cause @value{GDBN} to issue a warning when you use them. The optional
22108 argument @var{replacement} says which newer command should be used in
22109 favor of the deprecated one; if it is given, @value{GDBN} will mention
22110 the replacement as part of the warning.
22112 @kindex maint dump-me
22113 @item maint dump-me
22114 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
22115 Cause a fatal signal in the debugger and force it to dump its core.
22116 This is supported only on systems which support aborting a program
22117 with the @code{SIGQUIT} signal.
22119 @kindex maint internal-error
22120 @kindex maint internal-warning
22121 @item maint internal-error @r{[}@var{message-text}@r{]}
22122 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
22123 Cause @value{GDBN} to call the internal function @code{internal_error}
22124 or @code{internal_warning} and hence behave as though an internal error
22125 or internal warning has been detected. In addition to reporting the
22126 internal problem, these functions give the user the opportunity to
22127 either quit @value{GDBN} or create a core file of the current
22128 @value{GDBN} session.
22130 These commands take an optional parameter @var{message-text} that is
22131 used as the text of the error or warning message.
22133 Here's an example of using @code{indernal-error}:
22136 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
22137 @dots{}/maint.c:121: internal-error: testing, 1, 2
22138 A problem internal to GDB has been detected. Further
22139 debugging may prove unreliable.
22140 Quit this debugging session? (y or n) @kbd{n}
22141 Create a core file? (y or n) @kbd{n}
22145 @kindex maint packet
22146 @item maint packet @var{text}
22147 If @value{GDBN} is talking to an inferior via the serial protocol,
22148 then this command sends the string @var{text} to the inferior, and
22149 displays the response packet. @value{GDBN} supplies the initial
22150 @samp{$} character, the terminating @samp{#} character, and the
22153 @kindex maint print architecture
22154 @item maint print architecture @r{[}@var{file}@r{]}
22155 Print the entire architecture configuration. The optional argument
22156 @var{file} names the file where the output goes.
22158 @kindex maint print dummy-frames
22159 @item maint print dummy-frames
22160 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
22163 (@value{GDBP}) @kbd{b add}
22165 (@value{GDBP}) @kbd{print add(2,3)}
22166 Breakpoint 2, add (a=2, b=3) at @dots{}
22168 The program being debugged stopped while in a function called from GDB.
22170 (@value{GDBP}) @kbd{maint print dummy-frames}
22171 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
22172 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
22173 call_lo=0x01014000 call_hi=0x01014001
22177 Takes an optional file parameter.
22179 @kindex maint print registers
22180 @kindex maint print raw-registers
22181 @kindex maint print cooked-registers
22182 @kindex maint print register-groups
22183 @item maint print registers @r{[}@var{file}@r{]}
22184 @itemx maint print raw-registers @r{[}@var{file}@r{]}
22185 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
22186 @itemx maint print register-groups @r{[}@var{file}@r{]}
22187 Print @value{GDBN}'s internal register data structures.
22189 The command @code{maint print raw-registers} includes the contents of
22190 the raw register cache; the command @code{maint print cooked-registers}
22191 includes the (cooked) value of all registers; and the command
22192 @code{maint print register-groups} includes the groups that each
22193 register is a member of. @xref{Registers,, Registers, gdbint,
22194 @value{GDBN} Internals}.
22196 These commands take an optional parameter, a file name to which to
22197 write the information.
22199 @kindex maint print reggroups
22200 @item maint print reggroups @r{[}@var{file}@r{]}
22201 Print @value{GDBN}'s internal register group data structures. The
22202 optional argument @var{file} tells to what file to write the
22205 The register groups info looks like this:
22208 (@value{GDBP}) @kbd{maint print reggroups}
22221 This command forces @value{GDBN} to flush its internal register cache.
22223 @kindex maint print objfiles
22224 @cindex info for known object files
22225 @item maint print objfiles
22226 Print a dump of all known object files. For each object file, this
22227 command prints its name, address in memory, and all of its psymtabs
22230 @kindex maint print statistics
22231 @cindex bcache statistics
22232 @item maint print statistics
22233 This command prints, for each object file in the program, various data
22234 about that object file followed by the byte cache (@dfn{bcache})
22235 statistics for the object file. The objfile data includes the number
22236 of minimal, partical, full, and stabs symbols, the number of types
22237 defined by the objfile, the number of as yet unexpanded psym tables,
22238 the number of line tables and string tables, and the amount of memory
22239 used by the various tables. The bcache statistics include the counts,
22240 sizes, and counts of duplicates of all and unique objects, max,
22241 average, and median entry size, total memory used and its overhead and
22242 savings, and various measures of the hash table size and chain
22245 @kindex maint print type
22246 @cindex type chain of a data type
22247 @item maint print type @var{expr}
22248 Print the type chain for a type specified by @var{expr}. The argument
22249 can be either a type name or a symbol. If it is a symbol, the type of
22250 that symbol is described. The type chain produced by this command is
22251 a recursive definition of the data type as stored in @value{GDBN}'s
22252 data structures, including its flags and contained types.
22254 @kindex maint set dwarf2 max-cache-age
22255 @kindex maint show dwarf2 max-cache-age
22256 @item maint set dwarf2 max-cache-age
22257 @itemx maint show dwarf2 max-cache-age
22258 Control the DWARF 2 compilation unit cache.
22260 @cindex DWARF 2 compilation units cache
22261 In object files with inter-compilation-unit references, such as those
22262 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
22263 reader needs to frequently refer to previously read compilation units.
22264 This setting controls how long a compilation unit will remain in the
22265 cache if it is not referenced. A higher limit means that cached
22266 compilation units will be stored in memory longer, and more total
22267 memory will be used. Setting it to zero disables caching, which will
22268 slow down @value{GDBN} startup, but reduce memory consumption.
22270 @kindex maint set profile
22271 @kindex maint show profile
22272 @cindex profiling GDB
22273 @item maint set profile
22274 @itemx maint show profile
22275 Control profiling of @value{GDBN}.
22277 Profiling will be disabled until you use the @samp{maint set profile}
22278 command to enable it. When you enable profiling, the system will begin
22279 collecting timing and execution count data; when you disable profiling or
22280 exit @value{GDBN}, the results will be written to a log file. Remember that
22281 if you use profiling, @value{GDBN} will overwrite the profiling log file
22282 (often called @file{gmon.out}). If you have a record of important profiling
22283 data in a @file{gmon.out} file, be sure to move it to a safe location.
22285 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
22286 compiled with the @samp{-pg} compiler option.
22288 @kindex maint show-debug-regs
22289 @cindex x86 hardware debug registers
22290 @item maint show-debug-regs
22291 Control whether to show variables that mirror the x86 hardware debug
22292 registers. Use @code{ON} to enable, @code{OFF} to disable. If
22293 enabled, the debug registers values are shown when GDB inserts or
22294 removes a hardware breakpoint or watchpoint, and when the inferior
22295 triggers a hardware-assisted breakpoint or watchpoint.
22297 @kindex maint space
22298 @cindex memory used by commands
22300 Control whether to display memory usage for each command. If set to a
22301 nonzero value, @value{GDBN} will display how much memory each command
22302 took, following the command's own output. This can also be requested
22303 by invoking @value{GDBN} with the @option{--statistics} command-line
22304 switch (@pxref{Mode Options}).
22307 @cindex time of command execution
22309 Control whether to display the execution time for each command. If
22310 set to a nonzero value, @value{GDBN} will display how much time it
22311 took to execute each command, following the command's own output.
22312 This can also be requested by invoking @value{GDBN} with the
22313 @option{--statistics} command-line switch (@pxref{Mode Options}).
22315 @kindex maint translate-address
22316 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
22317 Find the symbol stored at the location specified by the address
22318 @var{addr} and an optional section name @var{section}. If found,
22319 @value{GDBN} prints the name of the closest symbol and an offset from
22320 the symbol's location to the specified address. This is similar to
22321 the @code{info address} command (@pxref{Symbols}), except that this
22322 command also allows to find symbols in other sections.
22326 The following command is useful for non-interactive invocations of
22327 @value{GDBN}, such as in the test suite.
22330 @item set watchdog @var{nsec}
22331 @kindex set watchdog
22332 @cindex watchdog timer
22333 @cindex timeout for commands
22334 Set the maximum number of seconds @value{GDBN} will wait for the
22335 target operation to finish. If this time expires, @value{GDBN}
22336 reports and error and the command is aborted.
22338 @item show watchdog
22339 Show the current setting of the target wait timeout.
22342 @node Remote Protocol
22343 @appendix @value{GDBN} Remote Serial Protocol
22348 * Stop Reply Packets::
22349 * General Query Packets::
22350 * Register Packet Format::
22351 * Tracepoint Packets::
22354 * File-I/O remote protocol extension::
22360 There may be occasions when you need to know something about the
22361 protocol---for example, if there is only one serial port to your target
22362 machine, you might want your program to do something special if it
22363 recognizes a packet meant for @value{GDBN}.
22365 In the examples below, @samp{->} and @samp{<-} are used to indicate
22366 transmitted and received data respectfully.
22368 @cindex protocol, @value{GDBN} remote serial
22369 @cindex serial protocol, @value{GDBN} remote
22370 @cindex remote serial protocol
22371 All @value{GDBN} commands and responses (other than acknowledgments) are
22372 sent as a @var{packet}. A @var{packet} is introduced with the character
22373 @samp{$}, the actual @var{packet-data}, and the terminating character
22374 @samp{#} followed by a two-digit @var{checksum}:
22377 @code{$}@var{packet-data}@code{#}@var{checksum}
22381 @cindex checksum, for @value{GDBN} remote
22383 The two-digit @var{checksum} is computed as the modulo 256 sum of all
22384 characters between the leading @samp{$} and the trailing @samp{#} (an
22385 eight bit unsigned checksum).
22387 Implementors should note that prior to @value{GDBN} 5.0 the protocol
22388 specification also included an optional two-digit @var{sequence-id}:
22391 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
22394 @cindex sequence-id, for @value{GDBN} remote
22396 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
22397 has never output @var{sequence-id}s. Stubs that handle packets added
22398 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
22400 @cindex acknowledgment, for @value{GDBN} remote
22401 When either the host or the target machine receives a packet, the first
22402 response expected is an acknowledgment: either @samp{+} (to indicate
22403 the package was received correctly) or @samp{-} (to request
22407 -> @code{$}@var{packet-data}@code{#}@var{checksum}
22412 The host (@value{GDBN}) sends @var{command}s, and the target (the
22413 debugging stub incorporated in your program) sends a @var{response}. In
22414 the case of step and continue @var{command}s, the response is only sent
22415 when the operation has completed (the target has again stopped).
22417 @var{packet-data} consists of a sequence of characters with the
22418 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
22421 Fields within the packet should be separated using @samp{,} @samp{;} or
22422 @cindex remote protocol, field separator
22423 @samp{:}. Except where otherwise noted all numbers are represented in
22424 @sc{hex} with leading zeros suppressed.
22426 Implementors should note that prior to @value{GDBN} 5.0, the character
22427 @samp{:} could not appear as the third character in a packet (as it
22428 would potentially conflict with the @var{sequence-id}).
22430 Response @var{data} can be run-length encoded to save space. A @samp{*}
22431 means that the next character is an @sc{ascii} encoding giving a repeat count
22432 which stands for that many repetitions of the character preceding the
22433 @samp{*}. The encoding is @code{n+29}, yielding a printable character
22434 where @code{n >=3} (which is where rle starts to win). The printable
22435 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
22436 value greater than 126 should not be used.
22443 means the same as "0000".
22445 The error response returned for some packets includes a two character
22446 error number. That number is not well defined.
22448 For any @var{command} not supported by the stub, an empty response
22449 (@samp{$#00}) should be returned. That way it is possible to extend the
22450 protocol. A newer @value{GDBN} can tell if a packet is supported based
22453 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
22454 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
22460 The following table provides a complete list of all currently defined
22461 @var{command}s and their corresponding response @var{data}.
22462 @xref{File-I/O remote protocol extension}, for details about the File
22463 I/O extension of the remote protocol.
22465 Each packet's description has a template showing the packet's overall
22466 syntax, followed by an explanation of the packet's meaning. We
22467 include spaces in some of the templates for clarity; these are not
22468 part of the packet's syntax. No @value{GDBN} packet uses spaces to
22469 separate its components. For example, a template like @samp{foo
22470 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
22471 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
22472 @var{baz}. GDB does not transmit a space character between the
22473 @samp{foo} and the @var{bar}, or between the @var{bar} and the
22476 Note that all packet forms beginning with an upper- or lower-case
22477 letter, other than those described here, are reserved for future use.
22479 Here are the packet descriptions.
22484 @cindex @samp{!} packet
22485 Enable extended mode. In extended mode, the remote server is made
22486 persistent. The @samp{R} packet is used to restart the program being
22492 The remote target both supports and has enabled extended mode.
22496 @cindex @samp{?} packet
22497 Indicate the reason the target halted. The reply is the same as for
22501 @xref{Stop Reply Packets}, for the reply specifications.
22503 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
22504 @cindex @samp{A} packet
22505 Initialized @code{argv[]} array passed into program. @var{arglen}
22506 specifies the number of bytes in the hex encoded byte stream
22507 @var{arg}. See @code{gdbserver} for more details.
22512 The arguments were set.
22518 @cindex @samp{b} packet
22519 (Don't use this packet; its behavior is not well-defined.)
22520 Change the serial line speed to @var{baud}.
22522 JTC: @emph{When does the transport layer state change? When it's
22523 received, or after the ACK is transmitted. In either case, there are
22524 problems if the command or the acknowledgment packet is dropped.}
22526 Stan: @emph{If people really wanted to add something like this, and get
22527 it working for the first time, they ought to modify ser-unix.c to send
22528 some kind of out-of-band message to a specially-setup stub and have the
22529 switch happen "in between" packets, so that from remote protocol's point
22530 of view, nothing actually happened.}
22532 @item B @var{addr},@var{mode}
22533 @cindex @samp{B} packet
22534 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
22535 breakpoint at @var{addr}.
22537 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
22538 (@pxref{insert breakpoint or watchpoint packet}).
22541 @cindex @samp{c} packet
22542 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
22543 resume at current address.
22546 @xref{Stop Reply Packets}, for the reply specifications.
22548 @item C @var{sig};@var{addr}
22549 @cindex @samp{C} packet
22550 Continue with signal @var{sig} (hex signal number). If
22551 @samp{;@var{addr}} is omitted, resume at same address.
22554 @xref{Stop Reply Packets}, for the reply specifications.
22557 @cindex @samp{d} packet
22560 Don't use this packet; instead, define a general set packet
22561 (@pxref{General Query Packets}).
22564 @cindex @samp{D} packet
22565 Detach @value{GDBN} from the remote system. Sent to the remote target
22566 before @value{GDBN} disconnects via the @code{detach} command.
22576 @item F @var{RC},@var{EE},@var{CF};@var{XX}
22577 @cindex @samp{F} packet
22578 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
22579 This is part of the File-I/O protocol extension. @xref{File-I/O
22580 remote protocol extension}, for the specification.
22583 @anchor{read registers packet}
22584 @cindex @samp{g} packet
22585 Read general registers.
22589 @item @var{XX@dots{}}
22590 Each byte of register data is described by two hex digits. The bytes
22591 with the register are transmitted in target byte order. The size of
22592 each register and their position within the @samp{g} packet are
22593 determined by the @value{GDBN} internal macros
22594 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{REGISTER_NAME} macros. The
22595 specification of several standard @samp{g} packets is specified below.
22600 @item G @var{XX@dots{}}
22601 @cindex @samp{G} packet
22602 Write general registers. @xref{read registers packet}, for a
22603 description of the @var{XX@dots{}} data.
22613 @item H @var{c} @var{t}
22614 @cindex @samp{H} packet
22615 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
22616 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
22617 should be @samp{c} for step and continue operations, @samp{g} for other
22618 operations. The thread designator @var{t} may be @samp{-1}, meaning all
22619 the threads, a thread number, or @samp{0} which means pick any thread.
22630 @c 'H': How restrictive (or permissive) is the thread model. If a
22631 @c thread is selected and stopped, are other threads allowed
22632 @c to continue to execute? As I mentioned above, I think the
22633 @c semantics of each command when a thread is selected must be
22634 @c described. For example:
22636 @c 'g': If the stub supports threads and a specific thread is
22637 @c selected, returns the register block from that thread;
22638 @c otherwise returns current registers.
22640 @c 'G' If the stub supports threads and a specific thread is
22641 @c selected, sets the registers of the register block of
22642 @c that thread; otherwise sets current registers.
22644 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
22645 @anchor{cycle step packet}
22646 @cindex @samp{i} packet
22647 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
22648 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
22649 step starting at that address.
22652 @cindex @samp{I} packet
22653 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
22657 @cindex @samp{k} packet
22660 FIXME: @emph{There is no description of how to operate when a specific
22661 thread context has been selected (i.e.@: does 'k' kill only that
22664 @item m @var{addr},@var{length}
22665 @cindex @samp{m} packet
22666 Read @var{length} bytes of memory starting at address @var{addr}.
22667 Note that @var{addr} may not be aligned to any particular boundary.
22669 The stub need not use any particular size or alignment when gathering
22670 data from memory for the response; even if @var{addr} is word-aligned
22671 and @var{length} is a multiple of the word size, the stub is free to
22672 use byte accesses, or not. For this reason, this packet may not be
22673 suitable for accessing memory-mapped I/O devices.
22674 @cindex alignment of remote memory accesses
22675 @cindex size of remote memory accesses
22676 @cindex memory, alignment and size of remote accesses
22680 @item @var{XX@dots{}}
22681 Memory contents; each byte is transmitted as a two-digit hexidecimal
22682 number. The reply may contain fewer bytes than requested if the
22683 server was able to read only part of the region of memory.
22688 @item M @var{addr},@var{length}:@var{XX@dots{}}
22689 @cindex @samp{M} packet
22690 Write @var{length} bytes of memory starting at address @var{addr}.
22691 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
22692 hexidecimal number.
22699 for an error (this includes the case where only part of the data was
22704 @cindex @samp{p} packet
22705 Read the value of register @var{n}; @var{n} is in hex.
22706 @xref{read registers packet}, for a description of how the returned
22707 register value is encoded.
22711 @item @var{XX@dots{}}
22712 the register's value
22716 Indicating an unrecognized @var{query}.
22719 @item P @var{n@dots{}}=@var{r@dots{}}
22720 @anchor{write register packet}
22721 @cindex @samp{P} packet
22722 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
22723 number @var{n} is in hexidecimal, and @var{r@dots{}} contains two hex
22724 digits for each byte in the register (target byte order).
22734 @item q @var{name} @var{params}@dots{}
22735 @itemx Q @var{name} @var{params}@dots{}
22736 @cindex @samp{q} packet
22737 @cindex @samp{Q} packet
22738 General query (@samp{q}) and set (@samp{Q}). These packets are
22739 described fully in @ref{General Query Packets}.
22742 @cindex @samp{r} packet
22743 Reset the entire system.
22745 Don't use this packet; use the @samp{R} packet instead.
22748 @cindex @samp{R} packet
22749 Restart the program being debugged. @var{XX}, while needed, is ignored.
22750 This packet is only available in extended mode.
22752 The @samp{R} packet has no reply.
22755 @cindex @samp{s} packet
22756 Single step. @var{addr} is the address at which to resume. If
22757 @var{addr} is omitted, resume at same address.
22760 @xref{Stop Reply Packets}, for the reply specifications.
22762 @item S @var{sig};@var{addr}
22763 @anchor{step with signal packet}
22764 @cindex @samp{S} packet
22765 Step with signal. This is analogous to the @samp{C} packet, but
22766 requests a single-step, rather than a normal resumption of execution.
22769 @xref{Stop Reply Packets}, for the reply specifications.
22771 @item t @var{addr}:@var{PP},@var{MM}
22772 @cindex @samp{t} packet
22773 Search backwards starting at address @var{addr} for a match with pattern
22774 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
22775 @var{addr} must be at least 3 digits.
22778 @cindex @samp{T} packet
22779 Find out if the thread XX is alive.
22784 thread is still alive
22790 Packets starting with @samp{v} are identified by a multi-letter name,
22791 up to the first @samp{;} or @samp{?} (or the end of the packet).
22793 @item vCont@r{[};@var{action}@r{[}:@var{tid}@r{]]}@dots{}
22794 @cindex @samp{vCont} packet
22795 Resume the inferior, specifying different actions for each thread.
22796 If an action is specified with no @var{tid}, then it is applied to any
22797 threads that don't have a specific action specified; if no default action is
22798 specified then other threads should remain stopped. Specifying multiple
22799 default actions is an error; specifying no actions is also an error.
22800 Thread IDs are specified in hexadecimal. Currently supported actions are:
22806 Continue with signal @var{sig}. @var{sig} should be two hex digits.
22810 Step with signal @var{sig}. @var{sig} should be two hex digits.
22813 The optional @var{addr} argument normally associated with these packets is
22814 not supported in @samp{vCont}.
22817 @xref{Stop Reply Packets}, for the reply specifications.
22820 @cindex @samp{vCont?} packet
22821 Request a list of actions supporetd by the @samp{vCont} packet.
22825 @item vCont@r{[};@var{action}@dots{}@r{]}
22826 The @samp{vCont} packet is supported. Each @var{action} is a supported
22827 command in the @samp{vCont} packet.
22829 The @samp{vCont} packet is not supported.
22832 @item X @var{addr},@var{length}:@var{XX@dots{}}
22834 @cindex @samp{X} packet
22835 Write data to memory, where the data is transmitted in binary.
22836 @var{addr} is address, @var{length} is number of bytes,
22837 @samp{@var{XX}@dots{}} is binary data. The bytes @code{0x23}
22838 (@sc{ascii} @samp{#}), @code{0x24} (@sc{ascii} @samp{$}), and
22839 @code{0x7d} (@sc{ascii} @samp{@}}) are escaped using @code{0x7d}
22840 (@sc{ascii} @samp{@}}), and then XORed with @code{0x20}. For example,
22841 the byte @code{0x7d} would be transmitted as the two bytes @code{0x7d
22852 @item z @var{type},@var{addr},@var{length}
22853 @itemx Z @var{type},@var{addr},@var{length}
22854 @anchor{insert breakpoint or watchpoint packet}
22855 @cindex @samp{z} packet
22856 @cindex @samp{Z} packets
22857 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
22858 watchpoint starting at address @var{address} and covering the next
22859 @var{length} bytes.
22861 Each breakpoint and watchpoint packet @var{type} is documented
22864 @emph{Implementation notes: A remote target shall return an empty string
22865 for an unrecognized breakpoint or watchpoint packet @var{type}. A
22866 remote target shall support either both or neither of a given
22867 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
22868 avoid potential problems with duplicate packets, the operations should
22869 be implemented in an idempotent way.}
22871 @item z0,@var{addr},@var{length}
22872 @itemx Z0,@var{addr},@var{length}
22873 @cindex @samp{z0} packet
22874 @cindex @samp{Z0} packet
22875 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
22876 @var{addr} of size @var{length}.
22878 A memory breakpoint is implemented by replacing the instruction at
22879 @var{addr} with a software breakpoint or trap instruction. The
22880 @var{length} is used by targets that indicates the size of the
22881 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
22882 @sc{mips} can insert either a 2 or 4 byte breakpoint).
22884 @emph{Implementation note: It is possible for a target to copy or move
22885 code that contains memory breakpoints (e.g., when implementing
22886 overlays). The behavior of this packet, in the presence of such a
22887 target, is not defined.}
22899 @item z1,@var{addr},@var{length}
22900 @itemx Z1,@var{addr},@var{length}
22901 @cindex @samp{z1} packet
22902 @cindex @samp{Z1} packet
22903 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
22904 address @var{addr} of size @var{length}.
22906 A hardware breakpoint is implemented using a mechanism that is not
22907 dependant on being able to modify the target's memory.
22909 @emph{Implementation note: A hardware breakpoint is not affected by code
22922 @item z2,@var{addr},@var{length}
22923 @itemx Z2,@var{addr},@var{length}
22924 @cindex @samp{z2} packet
22925 @cindex @samp{Z2} packet
22926 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
22938 @item z3,@var{addr},@var{length}
22939 @itemx Z3,@var{addr},@var{length}
22940 @cindex @samp{z3} packet
22941 @cindex @samp{Z3} packet
22942 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
22954 @item z4,@var{addr},@var{length}
22955 @itemx Z4,@var{addr},@var{length}
22956 @cindex @samp{z4} packet
22957 @cindex @samp{Z4} packet
22958 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
22972 @node Stop Reply Packets
22973 @section Stop Reply Packets
22974 @cindex stop reply packets
22976 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
22977 receive any of the below as a reply. In the case of the @samp{C},
22978 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
22979 when the target halts. In the below the exact meaning of @dfn{signal
22980 number} is poorly defined. In general one of the UNIX signal
22981 numbering conventions is used.
22983 As in the description of request packets, we include spaces in the
22984 reply templates for clarity; these are not part of the reply packet's
22985 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
22991 The program received signal number @var{AA} (a two-digit hexidecimal
22994 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
22995 @cindex @samp{T} packet reply
22996 The program received signal number @var{AA} (a two-digit hexidecimal
22997 number). Single-step and breakpoint traps are reported this way. The
22998 @samp{@var{n}:@var{r}} pairs give the values of important registers or
23002 If @var{n} is a hexidecimal number, it is a register number, and the
23003 corresponding @var{r} gives that register's value. @var{r} is a
23004 series of bytes in target byte order, with each byte given by a
23005 two-digit hex number.
23007 If @var{n} is @samp{thread}, then @var{r} is the thread process ID, in
23010 If @var{n} is @samp{watch}, @samp{rwatch}, or @samp{awatch}, then the
23011 packet indicates a watchpoint hit, and @var{r} is the data address, in
23014 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
23015 and go on to the next; this allows us to extend the protocol in the
23020 The process exited, and @var{AA} is the exit status. This is only
23021 applicable to certain targets.
23024 The process terminated with signal @var{AA}.
23026 @item O @var{XX}@dots{}
23027 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
23028 written as the program's console output. This can happen at any time
23029 while the program is running and the debugger should continue to wait
23030 for @samp{W}, @samp{T}, etc.
23032 @item F @var{call-id},@var{parameter}@dots{}
23033 @var{call-id} is the identifier which says which host system call should
23034 be called. This is just the name of the function. Translation into the
23035 correct system call is only applicable as it's defined in @value{GDBN}.
23036 @xref{File-I/O remote protocol extension}, for a list of implemented
23039 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
23040 this very system call.
23042 The target replies with this packet when it expects @value{GDBN} to
23043 call a host system call on behalf of the target. @value{GDBN} replies
23044 with an appropriate @samp{F} packet and keeps up waiting for the next
23045 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
23046 or @samp{s} action is expected to be continued. @xref{File-I/O remote
23047 protocol extension}, for more details.
23051 @node General Query Packets
23052 @section General Query Packets
23053 @cindex remote query requests
23055 Packets starting with @samp{q} are @dfn{general query packets};
23056 packets starting with @samp{Q} are @dfn{general set packets}. General
23057 query and set packets are a semi-unified form for retrieving and
23058 sending information to and from the stub.
23060 The initial letter of a query or set packet is followed by a name
23061 indicating what sort of thing the packet applies to. For example,
23062 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
23063 definitions with the stub. These packet names follow some
23068 The name must not contain commas, colons or semicolons.
23070 Most @value{GDBN} query and set packets have a leading upper case
23073 The names of custom vendor packets should use a company prefix, in
23074 lower case, followed by a period. For example, packets designed at
23075 the Acme Corporation might begin with @samp{qacme.foo} (for querying
23076 foos) or @samp{Qacme.bar} (for setting bars).
23079 A query or set packet may optionally be followed by a @samp{,} or
23080 @samp{;} separated list. Stubs must be careful to match the full
23081 packet name, in case packet names have common prefixes.
23083 Like the descriptions of the other packets, each description here
23084 has a template showing the packet's overall syntax, followed by an
23085 explanation of the packet's meaning. We include spaces in some of the
23086 templates for clarity; these are not part of the packet's syntax. No
23087 @value{GDBN} packet uses spaces to separate its components.
23089 Here are the currently defined query and set packets:
23094 @cindex current thread, remote request
23095 @cindex @samp{qC} packet
23096 Return the current thread id.
23101 Where @var{pid} is an unsigned hexidecimal process id.
23102 @item @r{(anything else)}
23103 Any other reply implies the old pid.
23106 @item qCRC:@var{addr},@var{length}
23107 @cindex CRC of memory block, remote request
23108 @cindex @samp{qCRC} packet
23109 Compute the CRC checksum of a block of memory.
23113 An error (such as memory fault)
23114 @item C @var{crc32}
23115 The specified memory region's checksum is @var{crc32}.
23119 @itemx qsThreadInfo
23120 @cindex list active threads, remote request
23121 @cindex @samp{qfThreadInfo} packet
23122 @cindex @samp{qsThreadInfo} packet
23123 Obtain a list of all active thread ids from the target (OS). Since there
23124 may be too many active threads to fit into one reply packet, this query
23125 works iteratively: it may require more than one query/reply sequence to
23126 obtain the entire list of threads. The first query of the sequence will
23127 be the @samp{qfThreadInfo} query; subsequent queries in the
23128 sequence will be the @samp{qsThreadInfo} query.
23130 NOTE: This packet replaces the @samp{qL} query (see below).
23136 @item m @var{id},@var{id}@dots{}
23137 a comma-separated list of thread ids
23139 (lower case letter @samp{L}) denotes end of list.
23142 In response to each query, the target will reply with a list of one or
23143 more thread ids, in big-endian unsigned hex, separated by commas.
23144 @value{GDBN} will respond to each reply with a request for more thread
23145 ids (using the @samp{qs} form of the query), until the target responds
23146 with @samp{l} (lower-case el, for @dfn{last}).
23148 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
23149 @cindex get thread-local storage address, remote request
23150 @cindex @samp{qGetTLSAddr} packet
23151 Fetch the address associated with thread local storage specified
23152 by @var{thread-id}, @var{offset}, and @var{lm}.
23154 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
23155 thread for which to fetch the TLS address.
23157 @var{offset} is the (big endian, hex encoded) offset associated with the
23158 thread local variable. (This offset is obtained from the debug
23159 information associated with the variable.)
23161 @var{lm} is the (big endian, hex encoded) OS/ABI specific encoding of the
23162 the load module associated with the thread local storage. For example,
23163 a @sc{gnu}/Linux system will pass the link map address of the shared
23164 object associated with the thread local storage under consideration.
23165 Other operating environments may choose to represent the load module
23166 differently, so the precise meaning of this parameter will vary.
23170 @item @var{XX}@dots{}
23171 Hex encoded (big endian) bytes representing the address of the thread
23172 local storage requested.
23175 An error occurred. @var{nn} are hex digits.
23178 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
23181 Use of this request packet is controlled by the @code{set remote
23182 get-thread-local-storage-address} command (@pxref{Remote
23183 configuration, set remote get-thread-local-storage-address}).
23185 @item qL @var{startflag} @var{threadcount} @var{nextthread}
23186 Obtain thread information from RTOS. Where: @var{startflag} (one hex
23187 digit) is one to indicate the first query and zero to indicate a
23188 subsequent query; @var{threadcount} (two hex digits) is the maximum
23189 number of threads the response packet can contain; and @var{nextthread}
23190 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
23191 returned in the response as @var{argthread}.
23193 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
23197 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
23198 Where: @var{count} (two hex digits) is the number of threads being
23199 returned; @var{done} (one hex digit) is zero to indicate more threads
23200 and one indicates no further threads; @var{argthreadid} (eight hex
23201 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
23202 is a sequence of thread IDs from the target. @var{threadid} (eight hex
23203 digits). See @code{remote.c:parse_threadlist_response()}.
23207 @cindex section offsets, remote request
23208 @cindex @samp{qOffsets} packet
23209 Get section offsets that the target used when re-locating the downloaded
23210 image. @emph{Note: while a @code{Bss} offset is included in the
23211 response, @value{GDBN} ignores this and instead applies the @code{Data}
23212 offset to the @code{Bss} section.}
23216 @item Text=@var{xxx};Data=@var{yyy};Bss=@var{zzz}
23219 @item qP @var{mode} @var{threadid}
23220 @cindex thread information, remote request
23221 @cindex @samp{qP} packet
23222 Returns information on @var{threadid}. Where: @var{mode} is a hex
23223 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
23225 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
23227 @item qPart:@var{object}:read:@var{annex}:@var{offset},@var{length}
23228 @cindex read special object, remote request
23229 @cindex @samp{qPart} packet
23230 Read uninterpreted bytes from the target's special data area
23231 identified by the keyword @var{object}. Request @var{length} bytes
23232 starting at @var{offset} bytes into the data. The content and
23233 encoding of @var{annex} is specific to the object; it can supply
23234 additional details about what data to access.
23236 Here are the specific requests of this form defined so far. All
23237 @samp{qPart:@var{object}:read:@dots{}} requests use the same reply
23238 formats, listed below.
23241 @item qPart:auxv:read::@var{offset},@var{length}
23242 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
23243 auxiliary vector}, and see @ref{Remote configuration,
23244 read-aux-vector-packet}. Note @var{annex} must be empty.
23250 The @var{offset} in the request is at the end of the data.
23251 There is no more data to be read.
23253 @item @var{XX}@dots{}
23254 Hex encoded data bytes read.
23255 This may be fewer bytes than the @var{length} in the request.
23258 The request was malformed, or @var{annex} was invalid.
23261 The offset was invalid, or there was an error encountered reading the data.
23262 @var{nn} is a hex-encoded @code{errno} value.
23265 An empty reply indicates the @var{object} or @var{annex} string was not
23266 recognized by the stub.
23269 @item qPart:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
23270 @cindex write data into object, remote request
23271 Write uninterpreted bytes into the target's special data area
23272 identified by the keyword @var{object}, starting at @var{offset} bytes
23273 into the data. @samp{@var{data}@dots{}} is the hex-encoded data to be
23274 written. The content and encoding of @var{annex} is specific to the
23275 object; it can supply additional details about what data to access.
23277 No requests of this form are presently in use. This specification
23278 serves as a placeholder to document the common format that new
23279 specific request specifications ought to use.
23284 @var{nn} (hex encoded) is the number of bytes written.
23285 This may be fewer bytes than supplied in the request.
23288 The request was malformed, or @var{annex} was invalid.
23291 The offset was invalid, or there was an error encountered writing the data.
23292 @var{nn} is a hex-encoded @code{errno} value.
23295 An empty reply indicates the @var{object} or @var{annex} string was not
23296 recognized by the stub, or that the object does not support writing.
23299 @item qPart:@var{object}:@var{operation}:@dots{}
23300 Requests of this form may be added in the future. When a stub does
23301 not recognize the @var{object} keyword, or its support for
23302 @var{object} does not recognize the @var{operation} keyword, the stub
23303 must respond with an empty packet.
23305 @item qRcmd,@var{command}
23306 @cindex execute remote command, remote request
23307 @cindex @samp{qRcmd} packet
23308 @var{command} (hex encoded) is passed to the local interpreter for
23309 execution. Invalid commands should be reported using the output
23310 string. Before the final result packet, the target may also respond
23311 with a number of intermediate @samp{O@var{output}} console output
23312 packets. @emph{Implementors should note that providing access to a
23313 stubs's interpreter may have security implications}.
23318 A command response with no output.
23320 A command response with the hex encoded output string @var{OUTPUT}.
23322 Indicate a badly formed request.
23324 An empty reply indicates that @samp{qRcmd} is not recognized.
23328 @cindex symbol lookup, remote request
23329 @cindex @samp{qSymbol} packet
23330 Notify the target that @value{GDBN} is prepared to serve symbol lookup
23331 requests. Accept requests from the target for the values of symbols.
23336 The target does not need to look up any (more) symbols.
23337 @item qSymbol:@var{sym_name}
23338 The target requests the value of symbol @var{sym_name} (hex encoded).
23339 @value{GDBN} may provide the value by using the
23340 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
23344 @item qSymbol:@var{sym_value}:@var{sym_name}
23345 Set the value of @var{sym_name} to @var{sym_value}.
23347 @var{sym_name} (hex encoded) is the name of a symbol whose value the
23348 target has previously requested.
23350 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
23351 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
23357 The target does not need to look up any (more) symbols.
23358 @item qSymbol:@var{sym_name}
23359 The target requests the value of a new symbol @var{sym_name} (hex
23360 encoded). @value{GDBN} will continue to supply the values of symbols
23361 (if available), until the target ceases to request them.
23366 @xref{Tracepoint Packets}.
23368 @item qThreadExtraInfo,@var{id}
23369 @cindex thread attributes info, remote request
23370 @cindex @samp{qThreadExtraInfo} packet
23371 Obtain a printable string description of a thread's attributes from
23372 the target OS. @var{id} is a thread-id in big-endian hex. This
23373 string may contain anything that the target OS thinks is interesting
23374 for @value{GDBN} to tell the user about the thread. The string is
23375 displayed in @value{GDBN}'s @code{info threads} display. Some
23376 examples of possible thread extra info strings are @samp{Runnable}, or
23377 @samp{Blocked on Mutex}.
23381 @item @var{XX}@dots{}
23382 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
23383 comprising the printable string containing the extra information about
23384 the thread's attributes.
23392 @xref{Tracepoint Packets}.
23396 @node Register Packet Format
23397 @section Register Packet Format
23399 The following @code{g}/@code{G} packets have previously been defined.
23400 In the below, some thirty-two bit registers are transferred as
23401 sixty-four bits. Those registers should be zero/sign extended (which?)
23402 to fill the space allocated. Register bytes are transfered in target
23403 byte order. The two nibbles within a register byte are transfered
23404 most-significant - least-significant.
23410 All registers are transfered as thirty-two bit quantities in the order:
23411 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
23412 registers; fsr; fir; fp.
23416 All registers are transfered as sixty-four bit quantities (including
23417 thirty-two bit registers such as @code{sr}). The ordering is the same
23422 @node Tracepoint Packets
23423 @section Tracepoint Packets
23424 @cindex tracepoint packets
23425 @cindex packets, tracepoint
23427 Here we describe the packets @value{GDBN} uses to implement
23428 tracepoints (@pxref{Tracepoints}).
23432 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
23433 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
23434 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
23435 the tracepoint is disabled. @var{step} is the tracepoint's step
23436 count, and @var{pass} is its pass count. If the trailing @samp{-} is
23437 present, further @samp{QTDP} packets will follow to specify this
23438 tracepoint's actions.
23443 The packet was understood and carried out.
23445 The packet was not recognized.
23448 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
23449 Define actions to be taken when a tracepoint is hit. @var{n} and
23450 @var{addr} must be the same as in the initial @samp{QTDP} packet for
23451 this tracepoint. This packet may only be sent immediately after
23452 another @samp{QTDP} packet that ended with a @samp{-}. If the
23453 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
23454 specifying more actions for this tracepoint.
23456 In the series of action packets for a given tracepoint, at most one
23457 can have an @samp{S} before its first @var{action}. If such a packet
23458 is sent, it and the following packets define ``while-stepping''
23459 actions. Any prior packets define ordinary actions --- that is, those
23460 taken when the tracepoint is first hit. If no action packet has an
23461 @samp{S}, then all the packets in the series specify ordinary
23462 tracepoint actions.
23464 The @samp{@var{action}@dots{}} portion of the packet is a series of
23465 actions, concatenated without separators. Each action has one of the
23471 Collect the registers whose bits are set in @var{mask}. @var{mask} is
23472 a hexidecimal number whose @var{i}'th bit is set if register number
23473 @var{i} should be collected. (The least significant bit is numbered
23474 zero.) Note that @var{mask} may be any number of digits long; it may
23475 not fit in a 32-bit word.
23477 @item M @var{basereg},@var{offset},@var{len}
23478 Collect @var{len} bytes of memory starting at the address in register
23479 number @var{basereg}, plus @var{offset}. If @var{basereg} is
23480 @samp{-1}, then the range has a fixed address: @var{offset} is the
23481 address of the lowest byte to collect. The @var{basereg},
23482 @var{offset}, and @var{len} parameters are all unsigned hexidecimal
23483 values (the @samp{-1} value for @var{basereg} is a special case).
23485 @item X @var{len},@var{expr}
23486 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
23487 it directs. @var{expr} is an agent expression, as described in
23488 @ref{Agent Expressions}. Each byte of the expression is encoded as a
23489 two-digit hex number in the packet; @var{len} is the number of bytes
23490 in the expression (and thus one-half the number of hex digits in the
23495 Any number of actions may be packed together in a single @samp{QTDP}
23496 packet, as long as the packet does not exceed the maximum packet
23497 length (400 bytes, for many stubs). There may be only one @samp{R}
23498 action per tracepoint, and it must precede any @samp{M} or @samp{X}
23499 actions. Any registers referred to by @samp{M} and @samp{X} actions
23500 must be collected by a preceding @samp{R} action. (The
23501 ``while-stepping'' actions are treated as if they were attached to a
23502 separate tracepoint, as far as these restrictions are concerned.)
23507 The packet was understood and carried out.
23509 The packet was not recognized.
23512 @item QTFrame:@var{n}
23513 Select the @var{n}'th tracepoint frame from the buffer, and use the
23514 register and memory contents recorded there to answer subsequent
23515 request packets from @value{GDBN}.
23517 A successful reply from the stub indicates that the stub has found the
23518 requested frame. The response is a series of parts, concatenated
23519 without separators, describing the frame we selected. Each part has
23520 one of the following forms:
23524 The selected frame is number @var{n} in the trace frame buffer;
23525 @var{f} is a hexidecimal number. If @var{f} is @samp{-1}, then there
23526 was no frame matching the criteria in the request packet.
23529 The selected trace frame records a hit of tracepoint number @var{t};
23530 @var{t} is a hexidecimal number.
23534 @item QTFrame:pc:@var{addr}
23535 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
23536 currently selected frame whose PC is @var{addr};
23537 @var{addr} is a hexidecimal number.
23539 @item QTFrame:tdp:@var{t}
23540 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
23541 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
23542 is a hexidecimal number.
23544 @item QTFrame:range:@var{start}:@var{end}
23545 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
23546 currently selected frame whose PC is between @var{start} (inclusive)
23547 and @var{end} (exclusive); @var{start} and @var{end} are hexidecimal
23550 @item QTFrame:outside:@var{start}:@var{end}
23551 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
23552 frame @emph{outside} the given range of addresses.
23555 Begin the tracepoint experiment. Begin collecting data from tracepoint
23556 hits in the trace frame buffer.
23559 End the tracepoint experiment. Stop collecting trace frames.
23562 Clear the table of tracepoints, and empty the trace frame buffer.
23564 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
23565 Establish the given ranges of memory as ``transparent''. The stub
23566 will answer requests for these ranges from memory's current contents,
23567 if they were not collected as part of the tracepoint hit.
23569 @value{GDBN} uses this to mark read-only regions of memory, like those
23570 containing program code. Since these areas never change, they should
23571 still have the same contents they did when the tracepoint was hit, so
23572 there's no reason for the stub to refuse to provide their contents.
23575 Ask the stub if there is a trace experiment running right now.
23580 There is no trace experiment running.
23582 There is a trace experiment running.
23589 @section Interrupts
23590 @cindex interrupts (remote protocol)
23592 When a program on the remote target is running, @value{GDBN} may
23593 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
23594 control of which is specified via @value{GDBN}'s @samp{remotebreak}
23595 setting (@pxref{set remotebreak}).
23597 The precise meaning of @code{BREAK} is defined by the transport
23598 mechanism and may, in fact, be undefined. @value{GDBN} does
23599 not currently define a @code{BREAK} mechanism for any of the network
23602 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
23603 transport mechanisms. It is represented by sending the single byte
23604 @code{0x03} without any of the usual packet overhead described in
23605 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
23606 transmitted as part of a packet, it is considered to be packet data
23607 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
23608 (@pxref{X packet}, used for binary downloads, may include an unescaped
23609 @code{0x03} as part of its packet.
23611 Stubs are not required to recognize these interrupt mechanisms and the
23612 precise meaning associated with receipt of the interrupt is
23613 implementation defined. If the stub is successful at interrupting the
23614 running program, it is expected that it will send one of the Stop
23615 Reply Packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
23616 of successfully stopping the program. Interrupts received while the
23617 program is stopped will be discarded.
23622 Example sequence of a target being re-started. Notice how the restart
23623 does not get any direct output:
23628 @emph{target restarts}
23631 <- @code{T001:1234123412341234}
23635 Example sequence of a target being stepped by a single instruction:
23638 -> @code{G1445@dots{}}
23643 <- @code{T001:1234123412341234}
23647 <- @code{1455@dots{}}
23651 @node File-I/O remote protocol extension
23652 @section File-I/O remote protocol extension
23653 @cindex File-I/O remote protocol extension
23656 * File-I/O Overview::
23657 * Protocol basics::
23658 * The F request packet::
23659 * The F reply packet::
23660 * Memory transfer::
23661 * The Ctrl-C message::
23663 * The isatty call::
23664 * The system call::
23665 * List of supported calls::
23666 * Protocol specific representation of datatypes::
23668 * File-I/O Examples::
23671 @node File-I/O Overview
23672 @subsection File-I/O Overview
23673 @cindex file-i/o overview
23675 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
23676 target to use the host's file system and console I/O when calling various
23677 system calls. System calls on the target system are translated into a
23678 remote protocol packet to the host system which then performs the needed
23679 actions and returns with an adequate response packet to the target system.
23680 This simulates file system operations even on targets that lack file systems.
23682 The protocol is defined host- and target-system independent. It uses
23683 its own independent representation of datatypes and values. Both,
23684 @value{GDBN} and the target's @value{GDBN} stub are responsible for
23685 translating the system dependent values into the unified protocol values
23686 when data is transmitted.
23688 The communication is synchronous. A system call is possible only
23689 when GDB is waiting for the @samp{C}, @samp{c}, @samp{S} or @samp{s}
23690 packets. While @value{GDBN} handles the request for a system call,
23691 the target is stopped to allow deterministic access to the target's
23692 memory. Therefore File-I/O is not interuptible by target signals. It
23693 is possible to interrupt File-I/O by a user interrupt (Ctrl-C), though.
23695 The target's request to perform a host system call does not finish
23696 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
23697 after finishing the system call, the target returns to continuing the
23698 previous activity (continue, step). No additional continue or step
23699 request from @value{GDBN} is required.
23702 (@value{GDBP}) continue
23703 <- target requests 'system call X'
23704 target is stopped, @value{GDBN} executes system call
23705 -> GDB returns result
23706 ... target continues, GDB returns to wait for the target
23707 <- target hits breakpoint and sends a Txx packet
23710 The protocol is only used for files on the host file system and
23711 for I/O on the console. Character or block special devices, pipes,
23712 named pipes or sockets or any other communication method on the host
23713 system are not supported by this protocol.
23715 @node Protocol basics
23716 @subsection Protocol basics
23717 @cindex protocol basics, file-i/o
23719 The File-I/O protocol uses the @code{F} packet, as request as well
23720 as as reply packet. Since a File-I/O system call can only occur when
23721 @value{GDBN} is waiting for the continuing or stepping target, the
23722 File-I/O request is a reply that @value{GDBN} has to expect as a result
23723 of a former @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
23724 This @code{F} packet contains all information needed to allow @value{GDBN}
23725 to call the appropriate host system call:
23729 A unique identifier for the requested system call.
23732 All parameters to the system call. Pointers are given as addresses
23733 in the target memory address space. Pointers to strings are given as
23734 pointer/length pair. Numerical values are given as they are.
23735 Numerical control values are given in a protocol specific representation.
23739 At that point @value{GDBN} has to perform the following actions.
23743 If parameter pointer values are given, which point to data needed as input
23744 to a system call, @value{GDBN} requests this data from the target with a
23745 standard @code{m} packet request. This additional communication has to be
23746 expected by the target implementation and is handled as any other @code{m}
23750 @value{GDBN} translates all value from protocol representation to host
23751 representation as needed. Datatypes are coerced into the host types.
23754 @value{GDBN} calls the system call
23757 It then coerces datatypes back to protocol representation.
23760 If pointer parameters in the request packet point to buffer space in which
23761 a system call is expected to copy data to, the data is transmitted to the
23762 target using a @code{M} or @code{X} packet. This packet has to be expected
23763 by the target implementation and is handled as any other @code{M} or @code{X}
23768 Eventually @value{GDBN} replies with another @code{F} packet which contains all
23769 necessary information for the target to continue. This at least contains
23776 @code{errno}, if has been changed by the system call.
23783 After having done the needed type and value coercion, the target continues
23784 the latest continue or step action.
23786 @node The F request packet
23787 @subsection The @code{F} request packet
23788 @cindex file-i/o request packet
23789 @cindex @code{F} request packet
23791 The @code{F} request packet has the following format:
23796 @code{F}@var{call-id}@code{,}@var{parameter@dots{}}
23799 @var{call-id} is the identifier to indicate the host system call to be called.
23800 This is just the name of the function.
23802 @var{parameter@dots{}} are the parameters to the system call.
23806 Parameters are hexadecimal integer values, either the real values in case
23807 of scalar datatypes, as pointers to target buffer space in case of compound
23808 datatypes and unspecified memory areas or as pointer/length pairs in case
23809 of string parameters. These are appended to the call-id, each separated
23810 from its predecessor by a comma. All values are transmitted in ASCII
23811 string representation, pointer/length pairs separated by a slash.
23813 @node The F reply packet
23814 @subsection The @code{F} reply packet
23815 @cindex file-i/o reply packet
23816 @cindex @code{F} reply packet
23818 The @code{F} reply packet has the following format:
23823 @code{F}@var{retcode}@code{,}@var{errno}@code{,}@var{Ctrl-C flag}@code{;}@var{call specific attachment}
23826 @var{retcode} is the return code of the system call as hexadecimal value.
23828 @var{errno} is the errno set by the call, in protocol specific representation.
23829 This parameter can be omitted if the call was successful.
23831 @var{Ctrl-C flag} is only send if the user requested a break. In this
23832 case, @var{errno} must be send as well, even if the call was successful.
23833 The @var{Ctrl-C flag} itself consists of the character 'C':
23840 or, if the call was interupted before the host call has been performed:
23847 assuming 4 is the protocol specific representation of @code{EINTR}.
23851 @node Memory transfer
23852 @subsection Memory transfer
23853 @cindex memory transfer, in file-i/o protocol
23855 Structured data which is transferred using a memory read or write as e.g.@:
23856 a @code{struct stat} is expected to be in a protocol specific format with
23857 all scalar multibyte datatypes being big endian. This should be done by
23858 the target before the @code{F} packet is sent resp.@: by @value{GDBN} before
23859 it transfers memory to the target. Transferred pointers to structured
23860 data should point to the already coerced data at any time.
23862 @node The Ctrl-C message
23863 @subsection The Ctrl-C message
23864 @cindex ctrl-c message, in file-i/o protocol
23866 A special case is, if the @var{Ctrl-C flag} is set in the @value{GDBN}
23867 reply packet. In this case the target should behave, as if it had
23868 gotten a break message. The meaning for the target is ``system call
23869 interupted by @code{SIGINT}''. Consequentially, the target should actually stop
23870 (as with a break message) and return to @value{GDBN} with a @code{T02}
23871 packet. In this case, it's important for the target to know, in which
23872 state the system call was interrupted. Since this action is by design
23873 not an atomic operation, we have to differ between two cases:
23877 The system call hasn't been performed on the host yet.
23880 The system call on the host has been finished.
23884 These two states can be distinguished by the target by the value of the
23885 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
23886 call hasn't been performed. This is equivalent to the @code{EINTR} handling
23887 on POSIX systems. In any other case, the target may presume that the
23888 system call has been finished --- successful or not --- and should behave
23889 as if the break message arrived right after the system call.
23891 @value{GDBN} must behave reliable. If the system call has not been called
23892 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
23893 @code{errno} in the packet. If the system call on the host has been finished
23894 before the user requests a break, the full action must be finshed by
23895 @value{GDBN}. This requires sending @code{M} or @code{X} packets as they fit.
23896 The @code{F} packet may only be send when either nothing has happened
23897 or the full action has been completed.
23900 @subsection Console I/O
23901 @cindex console i/o as part of file-i/o
23903 By default and if not explicitely closed by the target system, the file
23904 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
23905 on the @value{GDBN} console is handled as any other file output operation
23906 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
23907 by @value{GDBN} so that after the target read request from file descriptor
23908 0 all following typing is buffered until either one of the following
23913 The user presses @kbd{Ctrl-C}. The behaviour is as explained above, the
23915 system call is treated as finished.
23918 The user presses @kbd{Enter}. This is treated as end of input with a trailing
23922 The user presses @kbd{Ctrl-D}. This is treated as end of input. No trailing
23923 character, especially no Ctrl-D is appended to the input.
23927 If the user has typed more characters as fit in the buffer given to
23928 the read call, the trailing characters are buffered in @value{GDBN} until
23929 either another @code{read(0, @dots{})} is requested by the target or debugging
23930 is stopped on users request.
23932 @node The isatty call
23933 @subsection The @samp{isatty} function call
23934 @cindex isatty call, file-i/o protocol
23936 A special case in this protocol is the library call @code{isatty} which
23937 is implemented as its own call inside of this protocol. It returns
23938 1 to the target if the file descriptor given as parameter is attached
23939 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
23940 would require implementing @code{ioctl} and would be more complex than
23943 @node The system call
23944 @subsection The @samp{system} function call
23945 @cindex system call, file-i/o protocol
23947 The other special case in this protocol is the @code{system} call which
23948 is implemented as its own call, too. @value{GDBN} is taking over the full
23949 task of calling the necessary host calls to perform the @code{system}
23950 call. The return value of @code{system} is simplified before it's returned
23951 to the target. Basically, the only signal transmitted back is @code{EINTR}
23952 in case the user pressed @kbd{Ctrl-C}. Otherwise the return value consists
23953 entirely of the exit status of the called command.
23955 Due to security concerns, the @code{system} call is by default refused
23956 by @value{GDBN}. The user has to allow this call explicitly with the
23957 @kbd{set remote system-call-allowed 1} command.
23960 @item set remote system-call-allowed
23961 @kindex set remote system-call-allowed
23962 Control whether to allow the @code{system} calls in the File I/O
23963 protocol for the remote target. The default is zero (disabled).
23965 @item show remote system-call-allowed
23966 @kindex show remote system-call-allowed
23967 Show the current setting of system calls for the remote File I/O
23971 @node List of supported calls
23972 @subsection List of supported calls
23973 @cindex list of supported file-i/o calls
23990 @unnumberedsubsubsec open
23991 @cindex open, file-i/o system call
23995 int open(const char *pathname, int flags);
23996 int open(const char *pathname, int flags, mode_t mode);
23999 Fopen,pathptr/len,flags,mode
24003 @code{flags} is the bitwise or of the following values:
24007 If the file does not exist it will be created. The host
24008 rules apply as far as file ownership and time stamps
24012 When used with O_CREAT, if the file already exists it is
24013 an error and open() fails.
24016 If the file already exists and the open mode allows
24017 writing (O_RDWR or O_WRONLY is given) it will be
24018 truncated to length 0.
24021 The file is opened in append mode.
24024 The file is opened for reading only.
24027 The file is opened for writing only.
24030 The file is opened for reading and writing.
24033 Each other bit is silently ignored.
24038 @code{mode} is the bitwise or of the following values:
24042 User has read permission.
24045 User has write permission.
24048 Group has read permission.
24051 Group has write permission.
24054 Others have read permission.
24057 Others have write permission.
24060 Each other bit is silently ignored.
24065 @exdent Return value:
24066 open returns the new file descriptor or -1 if an error
24074 pathname already exists and O_CREAT and O_EXCL were used.
24077 pathname refers to a directory.
24080 The requested access is not allowed.
24083 pathname was too long.
24086 A directory component in pathname does not exist.
24089 pathname refers to a device, pipe, named pipe or socket.
24092 pathname refers to a file on a read-only filesystem and
24093 write access was requested.
24096 pathname is an invalid pointer value.
24099 No space on device to create the file.
24102 The process already has the maximum number of files open.
24105 The limit on the total number of files open on the system
24109 The call was interrupted by the user.
24113 @unnumberedsubsubsec close
24114 @cindex close, file-i/o system call
24123 @exdent Return value:
24124 close returns zero on success, or -1 if an error occurred.
24131 fd isn't a valid open file descriptor.
24134 The call was interrupted by the user.
24138 @unnumberedsubsubsec read
24139 @cindex read, file-i/o system call
24143 int read(int fd, void *buf, unsigned int count);
24146 Fread,fd,bufptr,count
24148 @exdent Return value:
24149 On success, the number of bytes read is returned.
24150 Zero indicates end of file. If count is zero, read
24151 returns zero as well. On error, -1 is returned.
24158 fd is not a valid file descriptor or is not open for
24162 buf is an invalid pointer value.
24165 The call was interrupted by the user.
24169 @unnumberedsubsubsec write
24170 @cindex write, file-i/o system call
24174 int write(int fd, const void *buf, unsigned int count);
24177 Fwrite,fd,bufptr,count
24179 @exdent Return value:
24180 On success, the number of bytes written are returned.
24181 Zero indicates nothing was written. On error, -1
24189 fd is not a valid file descriptor or is not open for
24193 buf is an invalid pointer value.
24196 An attempt was made to write a file that exceeds the
24197 host specific maximum file size allowed.
24200 No space on device to write the data.
24203 The call was interrupted by the user.
24207 @unnumberedsubsubsec lseek
24208 @cindex lseek, file-i/o system call
24212 long lseek (int fd, long offset, int flag);
24215 Flseek,fd,offset,flag
24218 @code{flag} is one of:
24222 The offset is set to offset bytes.
24225 The offset is set to its current location plus offset
24229 The offset is set to the size of the file plus offset
24234 @exdent Return value:
24235 On success, the resulting unsigned offset in bytes from
24236 the beginning of the file is returned. Otherwise, a
24237 value of -1 is returned.
24244 fd is not a valid open file descriptor.
24247 fd is associated with the @value{GDBN} console.
24250 flag is not a proper value.
24253 The call was interrupted by the user.
24257 @unnumberedsubsubsec rename
24258 @cindex rename, file-i/o system call
24262 int rename(const char *oldpath, const char *newpath);
24265 Frename,oldpathptr/len,newpathptr/len
24267 @exdent Return value:
24268 On success, zero is returned. On error, -1 is returned.
24275 newpath is an existing directory, but oldpath is not a
24279 newpath is a non-empty directory.
24282 oldpath or newpath is a directory that is in use by some
24286 An attempt was made to make a directory a subdirectory
24290 A component used as a directory in oldpath or new
24291 path is not a directory. Or oldpath is a directory
24292 and newpath exists but is not a directory.
24295 oldpathptr or newpathptr are invalid pointer values.
24298 No access to the file or the path of the file.
24302 oldpath or newpath was too long.
24305 A directory component in oldpath or newpath does not exist.
24308 The file is on a read-only filesystem.
24311 The device containing the file has no room for the new
24315 The call was interrupted by the user.
24319 @unnumberedsubsubsec unlink
24320 @cindex unlink, file-i/o system call
24324 int unlink(const char *pathname);
24327 Funlink,pathnameptr/len
24329 @exdent Return value:
24330 On success, zero is returned. On error, -1 is returned.
24337 No access to the file or the path of the file.
24340 The system does not allow unlinking of directories.
24343 The file pathname cannot be unlinked because it's
24344 being used by another process.
24347 pathnameptr is an invalid pointer value.
24350 pathname was too long.
24353 A directory component in pathname does not exist.
24356 A component of the path is not a directory.
24359 The file is on a read-only filesystem.
24362 The call was interrupted by the user.
24366 @unnumberedsubsubsec stat/fstat
24367 @cindex fstat, file-i/o system call
24368 @cindex stat, file-i/o system call
24372 int stat(const char *pathname, struct stat *buf);
24373 int fstat(int fd, struct stat *buf);
24376 Fstat,pathnameptr/len,bufptr
24379 @exdent Return value:
24380 On success, zero is returned. On error, -1 is returned.
24387 fd is not a valid open file.
24390 A directory component in pathname does not exist or the
24391 path is an empty string.
24394 A component of the path is not a directory.
24397 pathnameptr is an invalid pointer value.
24400 No access to the file or the path of the file.
24403 pathname was too long.
24406 The call was interrupted by the user.
24410 @unnumberedsubsubsec gettimeofday
24411 @cindex gettimeofday, file-i/o system call
24415 int gettimeofday(struct timeval *tv, void *tz);
24418 Fgettimeofday,tvptr,tzptr
24420 @exdent Return value:
24421 On success, 0 is returned, -1 otherwise.
24428 tz is a non-NULL pointer.
24431 tvptr and/or tzptr is an invalid pointer value.
24435 @unnumberedsubsubsec isatty
24436 @cindex isatty, file-i/o system call
24440 int isatty(int fd);
24445 @exdent Return value:
24446 Returns 1 if fd refers to the @value{GDBN} console, 0 otherwise.
24453 The call was interrupted by the user.
24457 @unnumberedsubsubsec system
24458 @cindex system, file-i/o system call
24462 int system(const char *command);
24465 Fsystem,commandptr/len
24467 @exdent Return value:
24468 The value returned is -1 on error and the return status
24469 of the command otherwise. Only the exit status of the
24470 command is returned, which is extracted from the hosts
24471 system return value by calling WEXITSTATUS(retval).
24472 In case /bin/sh could not be executed, 127 is returned.
24479 The call was interrupted by the user.
24482 @node Protocol specific representation of datatypes
24483 @subsection Protocol specific representation of datatypes
24484 @cindex protocol specific representation of datatypes, in file-i/o protocol
24487 * Integral datatypes::
24493 @node Integral datatypes
24494 @unnumberedsubsubsec Integral datatypes
24495 @cindex integral datatypes, in file-i/o protocol
24497 The integral datatypes used in the system calls are
24500 int@r{,} unsigned int@r{,} long@r{,} unsigned long@r{,} mode_t @r{and} time_t
24503 @code{Int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
24504 implemented as 32 bit values in this protocol.
24506 @code{Long} and @code{unsigned long} are implemented as 64 bit types.
24508 @xref{Limits}, for corresponding MIN and MAX values (similar to those
24509 in @file{limits.h}) to allow range checking on host and target.
24511 @code{time_t} datatypes are defined as seconds since the Epoch.
24513 All integral datatypes transferred as part of a memory read or write of a
24514 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
24517 @node Pointer values
24518 @unnumberedsubsubsec Pointer values
24519 @cindex pointer values, in file-i/o protocol
24521 Pointers to target data are transmitted as they are. An exception
24522 is made for pointers to buffers for which the length isn't
24523 transmitted as part of the function call, namely strings. Strings
24524 are transmitted as a pointer/length pair, both as hex values, e.g.@:
24531 which is a pointer to data of length 18 bytes at position 0x1aaf.
24532 The length is defined as the full string length in bytes, including
24533 the trailing null byte. Example:
24536 ``hello, world'' at address 0x123456
24547 @unnumberedsubsubsec struct stat
24548 @cindex struct stat, in file-i/o protocol
24550 The buffer of type struct stat used by the target and @value{GDBN} is defined
24555 unsigned int st_dev; /* device */
24556 unsigned int st_ino; /* inode */
24557 mode_t st_mode; /* protection */
24558 unsigned int st_nlink; /* number of hard links */
24559 unsigned int st_uid; /* user ID of owner */
24560 unsigned int st_gid; /* group ID of owner */
24561 unsigned int st_rdev; /* device type (if inode device) */
24562 unsigned long st_size; /* total size, in bytes */
24563 unsigned long st_blksize; /* blocksize for filesystem I/O */
24564 unsigned long st_blocks; /* number of blocks allocated */
24565 time_t st_atime; /* time of last access */
24566 time_t st_mtime; /* time of last modification */
24567 time_t st_ctime; /* time of last change */
24571 The integral datatypes are conforming to the definitions given in the
24572 approriate section (see @ref{Integral datatypes}, for details) so this
24573 structure is of size 64 bytes.
24575 The values of several fields have a restricted meaning and/or
24582 st_ino: No valid meaning for the target. Transmitted unchanged.
24584 st_mode: Valid mode bits are described in Appendix C. Any other
24585 bits have currently no meaning for the target.
24587 st_uid: No valid meaning for the target. Transmitted unchanged.
24589 st_gid: No valid meaning for the target. Transmitted unchanged.
24591 st_rdev: No valid meaning for the target. Transmitted unchanged.
24593 st_atime, st_mtime, st_ctime:
24594 These values have a host and file system dependent
24595 accuracy. Especially on Windows hosts the file systems
24596 don't support exact timing values.
24599 The target gets a struct stat of the above representation and is
24600 responsible to coerce it to the target representation before
24603 Note that due to size differences between the host and target
24604 representation of stat members, these members could eventually
24605 get truncated on the target.
24607 @node struct timeval
24608 @unnumberedsubsubsec struct timeval
24609 @cindex struct timeval, in file-i/o protocol
24611 The buffer of type struct timeval used by the target and @value{GDBN}
24612 is defined as follows:
24616 time_t tv_sec; /* second */
24617 long tv_usec; /* microsecond */
24621 The integral datatypes are conforming to the definitions given in the
24622 approriate section (see @ref{Integral datatypes}, for details) so this
24623 structure is of size 8 bytes.
24626 @subsection Constants
24627 @cindex constants, in file-i/o protocol
24629 The following values are used for the constants inside of the
24630 protocol. @value{GDBN} and target are resposible to translate these
24631 values before and after the call as needed.
24642 @unnumberedsubsubsec Open flags
24643 @cindex open flags, in file-i/o protocol
24645 All values are given in hexadecimal representation.
24657 @node mode_t values
24658 @unnumberedsubsubsec mode_t values
24659 @cindex mode_t values, in file-i/o protocol
24661 All values are given in octal representation.
24678 @unnumberedsubsubsec Errno values
24679 @cindex errno values, in file-i/o protocol
24681 All values are given in decimal representation.
24706 EUNKNOWN is used as a fallback error value if a host system returns
24707 any error value not in the list of supported error numbers.
24710 @unnumberedsubsubsec Lseek flags
24711 @cindex lseek flags, in file-i/o protocol
24720 @unnumberedsubsubsec Limits
24721 @cindex limits, in file-i/o protocol
24723 All values are given in decimal representation.
24726 INT_MIN -2147483648
24728 UINT_MAX 4294967295
24729 LONG_MIN -9223372036854775808
24730 LONG_MAX 9223372036854775807
24731 ULONG_MAX 18446744073709551615
24734 @node File-I/O Examples
24735 @subsection File-I/O Examples
24736 @cindex file-i/o examples
24738 Example sequence of a write call, file descriptor 3, buffer is at target
24739 address 0x1234, 6 bytes should be written:
24742 <- @code{Fwrite,3,1234,6}
24743 @emph{request memory read from target}
24746 @emph{return "6 bytes written"}
24750 Example sequence of a read call, file descriptor 3, buffer is at target
24751 address 0x1234, 6 bytes should be read:
24754 <- @code{Fread,3,1234,6}
24755 @emph{request memory write to target}
24756 -> @code{X1234,6:XXXXXX}
24757 @emph{return "6 bytes read"}
24761 Example sequence of a read call, call fails on the host due to invalid
24762 file descriptor (EBADF):
24765 <- @code{Fread,3,1234,6}
24769 Example sequence of a read call, user presses Ctrl-C before syscall on
24773 <- @code{Fread,3,1234,6}
24778 Example sequence of a read call, user presses Ctrl-C after syscall on
24782 <- @code{Fread,3,1234,6}
24783 -> @code{X1234,6:XXXXXX}
24787 @include agentexpr.texi
24801 % I think something like @colophon should be in texinfo. In the
24803 \long\def\colophon{\hbox to0pt{}\vfill
24804 \centerline{The body of this manual is set in}
24805 \centerline{\fontname\tenrm,}
24806 \centerline{with headings in {\bf\fontname\tenbf}}
24807 \centerline{and examples in {\tt\fontname\tentt}.}
24808 \centerline{{\it\fontname\tenit\/},}
24809 \centerline{{\bf\fontname\tenbf}, and}
24810 \centerline{{\sl\fontname\tensl\/}}
24811 \centerline{are used for emphasis.}\vfill}
24813 % Blame: doc@cygnus.com, 1991.