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
1746 @section Compiling for debugging
1748 In order to debug a program effectively, you need to generate
1749 debugging information when you compile it. This debugging information
1750 is stored in the object file; it describes the data type of each
1751 variable or function and the correspondence between source line numbers
1752 and addresses in the executable code.
1754 To request debugging information, specify the @samp{-g} option when you run
1757 Programs that are to be shipped to your customers are compiled with
1758 optimizations, using the @samp{-O} compiler option. However, many
1759 compilers are unable to handle the @samp{-g} and @samp{-O} options
1760 together. Using those compilers, you cannot generate optimized
1761 executables containing debugging information.
1763 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1764 without @samp{-O}, making it possible to debug optimized code. We
1765 recommend that you @emph{always} use @samp{-g} whenever you compile a
1766 program. You may think your program is correct, but there is no sense
1767 in pushing your luck.
1769 @cindex optimized code, debugging
1770 @cindex debugging optimized code
1771 When you debug a program compiled with @samp{-g -O}, remember that the
1772 optimizer is rearranging your code; the debugger shows you what is
1773 really there. Do not be too surprised when the execution path does not
1774 exactly match your source file! An extreme example: if you define a
1775 variable, but never use it, @value{GDBN} never sees that
1776 variable---because the compiler optimizes it out of existence.
1778 Some things do not work as well with @samp{-g -O} as with just
1779 @samp{-g}, particularly on machines with instruction scheduling. If in
1780 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1781 please report it to us as a bug (including a test case!).
1782 @xref{Variables}, for more information about debugging optimized code.
1784 Older versions of the @sc{gnu} C compiler permitted a variant option
1785 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1786 format; if your @sc{gnu} C compiler has this option, do not use it.
1788 @value{GDBN} knows about preprocessor macros and can show you their
1789 expansion (@pxref{Macros}). Most compilers do not include information
1790 about preprocessor macros in the debugging information if you specify
1791 the @option{-g} flag alone, because this information is rather large.
1792 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1793 provides macro information if you specify the options
1794 @option{-gdwarf-2} and @option{-g3}; the former option requests
1795 debugging information in the Dwarf 2 format, and the latter requests
1796 ``extra information''. In the future, we hope to find more compact
1797 ways to represent macro information, so that it can be included with
1802 @section Starting your program
1808 @kindex r @r{(@code{run})}
1811 Use the @code{run} command to start your program under @value{GDBN}.
1812 You must first specify the program name (except on VxWorks) with an
1813 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1814 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1815 (@pxref{Files, ,Commands to specify files}).
1819 If you are running your program in an execution environment that
1820 supports processes, @code{run} creates an inferior process and makes
1821 that process run your program. (In environments without processes,
1822 @code{run} jumps to the start of your program.)
1824 The execution of a program is affected by certain information it
1825 receives from its superior. @value{GDBN} provides ways to specify this
1826 information, which you must do @emph{before} starting your program. (You
1827 can change it after starting your program, but such changes only affect
1828 your program the next time you start it.) This information may be
1829 divided into four categories:
1832 @item The @emph{arguments.}
1833 Specify the arguments to give your program as the arguments of the
1834 @code{run} command. If a shell is available on your target, the shell
1835 is used to pass the arguments, so that you may use normal conventions
1836 (such as wildcard expansion or variable substitution) in describing
1838 In Unix systems, you can control which shell is used with the
1839 @code{SHELL} environment variable.
1840 @xref{Arguments, ,Your program's arguments}.
1842 @item The @emph{environment.}
1843 Your program normally inherits its environment from @value{GDBN}, but you can
1844 use the @value{GDBN} commands @code{set environment} and @code{unset
1845 environment} to change parts of the environment that affect
1846 your program. @xref{Environment, ,Your program's environment}.
1848 @item The @emph{working directory.}
1849 Your program inherits its working directory from @value{GDBN}. You can set
1850 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1851 @xref{Working Directory, ,Your program's working directory}.
1853 @item The @emph{standard input and output.}
1854 Your program normally uses the same device for standard input and
1855 standard output as @value{GDBN} is using. You can redirect input and output
1856 in the @code{run} command line, or you can use the @code{tty} command to
1857 set a different device for your program.
1858 @xref{Input/Output, ,Your program's input and output}.
1861 @emph{Warning:} While input and output redirection work, you cannot use
1862 pipes to pass the output of the program you are debugging to another
1863 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1867 When you issue the @code{run} command, your program begins to execute
1868 immediately. @xref{Stopping, ,Stopping and continuing}, for discussion
1869 of how to arrange for your program to stop. Once your program has
1870 stopped, you may call functions in your program, using the @code{print}
1871 or @code{call} commands. @xref{Data, ,Examining Data}.
1873 If the modification time of your symbol file has changed since the last
1874 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1875 table, and reads it again. When it does this, @value{GDBN} tries to retain
1876 your current breakpoints.
1881 @cindex run to main procedure
1882 The name of the main procedure can vary from language to language.
1883 With C or C@t{++}, the main procedure name is always @code{main}, but
1884 other languages such as Ada do not require a specific name for their
1885 main procedure. The debugger provides a convenient way to start the
1886 execution of the program and to stop at the beginning of the main
1887 procedure, depending on the language used.
1889 The @samp{start} command does the equivalent of setting a temporary
1890 breakpoint at the beginning of the main procedure and then invoking
1891 the @samp{run} command.
1893 @cindex elaboration phase
1894 Some programs contain an @dfn{elaboration} phase where some startup code is
1895 executed before the main procedure is called. This depends on the
1896 languages used to write your program. In C@t{++}, for instance,
1897 constructors for static and global objects are executed before
1898 @code{main} is called. It is therefore possible that the debugger stops
1899 before reaching the main procedure. However, the temporary breakpoint
1900 will remain to halt execution.
1902 Specify the arguments to give to your program as arguments to the
1903 @samp{start} command. These arguments will be given verbatim to the
1904 underlying @samp{run} command. Note that the same arguments will be
1905 reused if no argument is provided during subsequent calls to
1906 @samp{start} or @samp{run}.
1908 It is sometimes necessary to debug the program during elaboration. In
1909 these cases, using the @code{start} command would stop the execution of
1910 your program too late, as the program would have already completed the
1911 elaboration phase. Under these circumstances, insert breakpoints in your
1912 elaboration code before running your program.
1916 @section Your program's arguments
1918 @cindex arguments (to your program)
1919 The arguments to your program can be specified by the arguments of the
1921 They are passed to a shell, which expands wildcard characters and
1922 performs redirection of I/O, and thence to your program. Your
1923 @code{SHELL} environment variable (if it exists) specifies what shell
1924 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1925 the default shell (@file{/bin/sh} on Unix).
1927 On non-Unix systems, the program is usually invoked directly by
1928 @value{GDBN}, which emulates I/O redirection via the appropriate system
1929 calls, and the wildcard characters are expanded by the startup code of
1930 the program, not by the shell.
1932 @code{run} with no arguments uses the same arguments used by the previous
1933 @code{run}, or those set by the @code{set args} command.
1938 Specify the arguments to be used the next time your program is run. If
1939 @code{set args} has no arguments, @code{run} executes your program
1940 with no arguments. Once you have run your program with arguments,
1941 using @code{set args} before the next @code{run} is the only way to run
1942 it again without arguments.
1946 Show the arguments to give your program when it is started.
1950 @section Your program's environment
1952 @cindex environment (of your program)
1953 The @dfn{environment} consists of a set of environment variables and
1954 their values. Environment variables conventionally record such things as
1955 your user name, your home directory, your terminal type, and your search
1956 path for programs to run. Usually you set up environment variables with
1957 the shell and they are inherited by all the other programs you run. When
1958 debugging, it can be useful to try running your program with a modified
1959 environment without having to start @value{GDBN} over again.
1963 @item path @var{directory}
1964 Add @var{directory} to the front of the @code{PATH} environment variable
1965 (the search path for executables) that will be passed to your program.
1966 The value of @code{PATH} used by @value{GDBN} does not change.
1967 You may specify several directory names, separated by whitespace or by a
1968 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1969 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1970 is moved to the front, so it is searched sooner.
1972 You can use the string @samp{$cwd} to refer to whatever is the current
1973 working directory at the time @value{GDBN} searches the path. If you
1974 use @samp{.} instead, it refers to the directory where you executed the
1975 @code{path} command. @value{GDBN} replaces @samp{.} in the
1976 @var{directory} argument (with the current path) before adding
1977 @var{directory} to the search path.
1978 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1979 @c document that, since repeating it would be a no-op.
1983 Display the list of search paths for executables (the @code{PATH}
1984 environment variable).
1986 @kindex show environment
1987 @item show environment @r{[}@var{varname}@r{]}
1988 Print the value of environment variable @var{varname} to be given to
1989 your program when it starts. If you do not supply @var{varname},
1990 print the names and values of all environment variables to be given to
1991 your program. You can abbreviate @code{environment} as @code{env}.
1993 @kindex set environment
1994 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1995 Set environment variable @var{varname} to @var{value}. The value
1996 changes for your program only, not for @value{GDBN} itself. @var{value} may
1997 be any string; the values of environment variables are just strings, and
1998 any interpretation is supplied by your program itself. The @var{value}
1999 parameter is optional; if it is eliminated, the variable is set to a
2001 @c "any string" here does not include leading, trailing
2002 @c blanks. Gnu asks: does anyone care?
2004 For example, this command:
2011 tells the debugged program, when subsequently run, that its user is named
2012 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2013 are not actually required.)
2015 @kindex unset environment
2016 @item unset environment @var{varname}
2017 Remove variable @var{varname} from the environment to be passed to your
2018 program. This is different from @samp{set env @var{varname} =};
2019 @code{unset environment} removes the variable from the environment,
2020 rather than assigning it an empty value.
2023 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2025 by your @code{SHELL} environment variable if it exists (or
2026 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2027 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2028 @file{.bashrc} for BASH---any variables you set in that file affect
2029 your program. You may wish to move setting of environment variables to
2030 files that are only run when you sign on, such as @file{.login} or
2033 @node Working Directory
2034 @section Your program's working directory
2036 @cindex working directory (of your program)
2037 Each time you start your program with @code{run}, it inherits its
2038 working directory from the current working directory of @value{GDBN}.
2039 The @value{GDBN} working directory is initially whatever it inherited
2040 from its parent process (typically the shell), but you can specify a new
2041 working directory in @value{GDBN} with the @code{cd} command.
2043 The @value{GDBN} working directory also serves as a default for the commands
2044 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2049 @cindex change working directory
2050 @item cd @var{directory}
2051 Set the @value{GDBN} working directory to @var{directory}.
2055 Print the @value{GDBN} working directory.
2058 It is generally impossible to find the current working directory of
2059 the process being debugged (since a program can change its directory
2060 during its run). If you work on a system where @value{GDBN} is
2061 configured with the @file{/proc} support, you can use the @code{info
2062 proc} command (@pxref{SVR4 Process Information}) to find out the
2063 current working directory of the debuggee.
2066 @section Your program's input and output
2071 By default, the program you run under @value{GDBN} does input and output to
2072 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2073 to its own terminal modes to interact with you, but it records the terminal
2074 modes your program was using and switches back to them when you continue
2075 running your program.
2078 @kindex info terminal
2080 Displays information recorded by @value{GDBN} about the terminal modes your
2084 You can redirect your program's input and/or output using shell
2085 redirection with the @code{run} command. For example,
2092 starts your program, diverting its output to the file @file{outfile}.
2095 @cindex controlling terminal
2096 Another way to specify where your program should do input and output is
2097 with the @code{tty} command. This command accepts a file name as
2098 argument, and causes this file to be the default for future @code{run}
2099 commands. It also resets the controlling terminal for the child
2100 process, for future @code{run} commands. For example,
2107 directs that processes started with subsequent @code{run} commands
2108 default to do input and output on the terminal @file{/dev/ttyb} and have
2109 that as their controlling terminal.
2111 An explicit redirection in @code{run} overrides the @code{tty} command's
2112 effect on the input/output device, but not its effect on the controlling
2115 When you use the @code{tty} command or redirect input in the @code{run}
2116 command, only the input @emph{for your program} is affected. The input
2117 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2118 for @code{set inferior-tty}.
2120 @cindex inferior tty
2121 @cindex set inferior controlling terminal
2122 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2123 display the name of the terminal that will be used for future runs of your
2127 @item set inferior-tty /dev/ttyb
2128 @kindex set inferior-tty
2129 Set the tty for the program being debugged to /dev/ttyb.
2131 @item show inferior-tty
2132 @kindex show inferior-tty
2133 Show the current tty for the program being debugged.
2137 @section Debugging an already-running process
2142 @item attach @var{process-id}
2143 This command attaches to a running process---one that was started
2144 outside @value{GDBN}. (@code{info files} shows your active
2145 targets.) The command takes as argument a process ID. The usual way to
2146 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2147 or with the @samp{jobs -l} shell command.
2149 @code{attach} does not repeat if you press @key{RET} a second time after
2150 executing the command.
2153 To use @code{attach}, your program must be running in an environment
2154 which supports processes; for example, @code{attach} does not work for
2155 programs on bare-board targets that lack an operating system. You must
2156 also have permission to send the process a signal.
2158 When you use @code{attach}, the debugger finds the program running in
2159 the process first by looking in the current working directory, then (if
2160 the program is not found) by using the source file search path
2161 (@pxref{Source Path, ,Specifying source directories}). You can also use
2162 the @code{file} command to load the program. @xref{Files, ,Commands to
2165 The first thing @value{GDBN} does after arranging to debug the specified
2166 process is to stop it. You can examine and modify an attached process
2167 with all the @value{GDBN} commands that are ordinarily available when
2168 you start processes with @code{run}. You can insert breakpoints; you
2169 can step and continue; you can modify storage. If you would rather the
2170 process continue running, you may use the @code{continue} command after
2171 attaching @value{GDBN} to the process.
2176 When you have finished debugging the attached process, you can use the
2177 @code{detach} command to release it from @value{GDBN} control. Detaching
2178 the process continues its execution. After the @code{detach} command,
2179 that process and @value{GDBN} become completely independent once more, and you
2180 are ready to @code{attach} another process or start one with @code{run}.
2181 @code{detach} does not repeat if you press @key{RET} again after
2182 executing the command.
2185 If you exit @value{GDBN} or use the @code{run} command while you have an
2186 attached process, you kill that process. By default, @value{GDBN} asks
2187 for confirmation if you try to do either of these things; you can
2188 control whether or not you need to confirm by using the @code{set
2189 confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
2193 @section Killing the child process
2198 Kill the child process in which your program is running under @value{GDBN}.
2201 This command is useful if you wish to debug a core dump instead of a
2202 running process. @value{GDBN} ignores any core dump file while your program
2205 On some operating systems, a program cannot be executed outside @value{GDBN}
2206 while you have breakpoints set on it inside @value{GDBN}. You can use the
2207 @code{kill} command in this situation to permit running your program
2208 outside the debugger.
2210 The @code{kill} command is also useful if you wish to recompile and
2211 relink your program, since on many systems it is impossible to modify an
2212 executable file while it is running in a process. In this case, when you
2213 next type @code{run}, @value{GDBN} notices that the file has changed, and
2214 reads the symbol table again (while trying to preserve your current
2215 breakpoint settings).
2218 @section Debugging programs with multiple threads
2220 @cindex threads of execution
2221 @cindex multiple threads
2222 @cindex switching threads
2223 In some operating systems, such as HP-UX and Solaris, a single program
2224 may have more than one @dfn{thread} of execution. The precise semantics
2225 of threads differ from one operating system to another, but in general
2226 the threads of a single program are akin to multiple processes---except
2227 that they share one address space (that is, they can all examine and
2228 modify the same variables). On the other hand, each thread has its own
2229 registers and execution stack, and perhaps private memory.
2231 @value{GDBN} provides these facilities for debugging multi-thread
2235 @item automatic notification of new threads
2236 @item @samp{thread @var{threadno}}, a command to switch among threads
2237 @item @samp{info threads}, a command to inquire about existing threads
2238 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2239 a command to apply a command to a list of threads
2240 @item thread-specific breakpoints
2244 @emph{Warning:} These facilities are not yet available on every
2245 @value{GDBN} configuration where the operating system supports threads.
2246 If your @value{GDBN} does not support threads, these commands have no
2247 effect. For example, a system without thread support shows no output
2248 from @samp{info threads}, and always rejects the @code{thread} command,
2252 (@value{GDBP}) info threads
2253 (@value{GDBP}) thread 1
2254 Thread ID 1 not known. Use the "info threads" command to
2255 see the IDs of currently known threads.
2257 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2258 @c doesn't support threads"?
2261 @cindex focus of debugging
2262 @cindex current thread
2263 The @value{GDBN} thread debugging facility allows you to observe all
2264 threads while your program runs---but whenever @value{GDBN} takes
2265 control, one thread in particular is always the focus of debugging.
2266 This thread is called the @dfn{current thread}. Debugging commands show
2267 program information from the perspective of the current thread.
2269 @cindex @code{New} @var{systag} message
2270 @cindex thread identifier (system)
2271 @c FIXME-implementors!! It would be more helpful if the [New...] message
2272 @c included GDB's numeric thread handle, so you could just go to that
2273 @c thread without first checking `info threads'.
2274 Whenever @value{GDBN} detects a new thread in your program, it displays
2275 the target system's identification for the thread with a message in the
2276 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2277 whose form varies depending on the particular system. For example, on
2278 LynxOS, you might see
2281 [New process 35 thread 27]
2285 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2286 the @var{systag} is simply something like @samp{process 368}, with no
2289 @c FIXME!! (1) Does the [New...] message appear even for the very first
2290 @c thread of a program, or does it only appear for the
2291 @c second---i.e.@: when it becomes obvious we have a multithread
2293 @c (2) *Is* there necessarily a first thread always? Or do some
2294 @c multithread systems permit starting a program with multiple
2295 @c threads ab initio?
2297 @cindex thread number
2298 @cindex thread identifier (GDB)
2299 For debugging purposes, @value{GDBN} associates its own thread
2300 number---always a single integer---with each thread in your program.
2303 @kindex info threads
2305 Display a summary of all threads currently in your
2306 program. @value{GDBN} displays for each thread (in this order):
2310 the thread number assigned by @value{GDBN}
2313 the target system's thread identifier (@var{systag})
2316 the current stack frame summary for that thread
2320 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2321 indicates the current thread.
2325 @c end table here to get a little more width for example
2328 (@value{GDBP}) info threads
2329 3 process 35 thread 27 0x34e5 in sigpause ()
2330 2 process 35 thread 23 0x34e5 in sigpause ()
2331 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2337 @cindex debugging multithreaded programs (on HP-UX)
2338 @cindex thread identifier (GDB), on HP-UX
2339 For debugging purposes, @value{GDBN} associates its own thread
2340 number---a small integer assigned in thread-creation order---with each
2341 thread in your program.
2343 @cindex @code{New} @var{systag} message, on HP-UX
2344 @cindex thread identifier (system), on HP-UX
2345 @c FIXME-implementors!! It would be more helpful if the [New...] message
2346 @c included GDB's numeric thread handle, so you could just go to that
2347 @c thread without first checking `info threads'.
2348 Whenever @value{GDBN} detects a new thread in your program, it displays
2349 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2350 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2351 whose form varies depending on the particular system. For example, on
2355 [New thread 2 (system thread 26594)]
2359 when @value{GDBN} notices a new thread.
2362 @kindex info threads (HP-UX)
2364 Display a summary of all threads currently in your
2365 program. @value{GDBN} displays for each thread (in this order):
2368 @item the thread number assigned by @value{GDBN}
2370 @item the target system's thread identifier (@var{systag})
2372 @item the current stack frame summary for that thread
2376 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2377 indicates the current thread.
2381 @c end table here to get a little more width for example
2384 (@value{GDBP}) info threads
2385 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2387 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2388 from /usr/lib/libc.2
2389 1 system thread 27905 0x7b003498 in _brk () \@*
2390 from /usr/lib/libc.2
2393 On Solaris, you can display more information about user threads with a
2394 Solaris-specific command:
2397 @item maint info sol-threads
2398 @kindex maint info sol-threads
2399 @cindex thread info (Solaris)
2400 Display info on Solaris user threads.
2404 @kindex thread @var{threadno}
2405 @item thread @var{threadno}
2406 Make thread number @var{threadno} the current thread. The command
2407 argument @var{threadno} is the internal @value{GDBN} thread number, as
2408 shown in the first field of the @samp{info threads} display.
2409 @value{GDBN} responds by displaying the system identifier of the thread
2410 you selected, and its current stack frame summary:
2413 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2414 (@value{GDBP}) thread 2
2415 [Switching to process 35 thread 23]
2416 0x34e5 in sigpause ()
2420 As with the @samp{[New @dots{}]} message, the form of the text after
2421 @samp{Switching to} depends on your system's conventions for identifying
2424 @kindex thread apply
2425 @cindex apply command to several threads
2426 @item thread apply [@var{threadno}] [@var{all}] @var{args}
2427 The @code{thread apply} command allows you to apply a command to one or
2428 more threads. Specify the numbers of the threads that you want affected
2429 with the command argument @var{threadno}. @var{threadno} is the internal
2430 @value{GDBN} thread number, as shown in the first field of the @samp{info
2431 threads} display. To apply a command to all threads, use
2432 @code{thread apply all} @var{args}.
2435 @cindex automatic thread selection
2436 @cindex switching threads automatically
2437 @cindex threads, automatic switching
2438 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2439 signal, it automatically selects the thread where that breakpoint or
2440 signal happened. @value{GDBN} alerts you to the context switch with a
2441 message of the form @samp{[Switching to @var{systag}]} to identify the
2444 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2445 more information about how @value{GDBN} behaves when you stop and start
2446 programs with multiple threads.
2448 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2449 watchpoints in programs with multiple threads.
2452 @section Debugging programs with multiple processes
2454 @cindex fork, debugging programs which call
2455 @cindex multiple processes
2456 @cindex processes, multiple
2457 On most systems, @value{GDBN} has no special support for debugging
2458 programs which create additional processes using the @code{fork}
2459 function. When a program forks, @value{GDBN} will continue to debug the
2460 parent process and the child process will run unimpeded. If you have
2461 set a breakpoint in any code which the child then executes, the child
2462 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2463 will cause it to terminate.
2465 However, if you want to debug the child process there is a workaround
2466 which isn't too painful. Put a call to @code{sleep} in the code which
2467 the child process executes after the fork. It may be useful to sleep
2468 only if a certain environment variable is set, or a certain file exists,
2469 so that the delay need not occur when you don't want to run @value{GDBN}
2470 on the child. While the child is sleeping, use the @code{ps} program to
2471 get its process ID. Then tell @value{GDBN} (a new invocation of
2472 @value{GDBN} if you are also debugging the parent process) to attach to
2473 the child process (@pxref{Attach}). From that point on you can debug
2474 the child process just like any other process which you attached to.
2476 On some systems, @value{GDBN} provides support for debugging programs that
2477 create additional processes using the @code{fork} or @code{vfork} functions.
2478 Currently, the only platforms with this feature are HP-UX (11.x and later
2479 only?) and GNU/Linux (kernel version 2.5.60 and later).
2481 By default, when a program forks, @value{GDBN} will continue to debug
2482 the parent process and the child process will run unimpeded.
2484 If you want to follow the child process instead of the parent process,
2485 use the command @w{@code{set follow-fork-mode}}.
2488 @kindex set follow-fork-mode
2489 @item set follow-fork-mode @var{mode}
2490 Set the debugger response to a program call of @code{fork} or
2491 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2492 process. The @var{mode} argument can be:
2496 The original process is debugged after a fork. The child process runs
2497 unimpeded. This is the default.
2500 The new process is debugged after a fork. The parent process runs
2505 @kindex show follow-fork-mode
2506 @item show follow-fork-mode
2507 Display the current debugger response to a @code{fork} or @code{vfork} call.
2510 If you ask to debug a child process and a @code{vfork} is followed by an
2511 @code{exec}, @value{GDBN} executes the new target up to the first
2512 breakpoint in the new target. If you have a breakpoint set on
2513 @code{main} in your original program, the breakpoint will also be set on
2514 the child process's @code{main}.
2516 When a child process is spawned by @code{vfork}, you cannot debug the
2517 child or parent until an @code{exec} call completes.
2519 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2520 call executes, the new target restarts. To restart the parent process,
2521 use the @code{file} command with the parent executable name as its
2524 You can use the @code{catch} command to make @value{GDBN} stop whenever
2525 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2526 Catchpoints, ,Setting catchpoints}.
2529 @chapter Stopping and Continuing
2531 The principal purposes of using a debugger are so that you can stop your
2532 program before it terminates; or so that, if your program runs into
2533 trouble, you can investigate and find out why.
2535 Inside @value{GDBN}, your program may stop for any of several reasons,
2536 such as a signal, a breakpoint, or reaching a new line after a
2537 @value{GDBN} command such as @code{step}. You may then examine and
2538 change variables, set new breakpoints or remove old ones, and then
2539 continue execution. Usually, the messages shown by @value{GDBN} provide
2540 ample explanation of the status of your program---but you can also
2541 explicitly request this information at any time.
2544 @kindex info program
2546 Display information about the status of your program: whether it is
2547 running or not, what process it is, and why it stopped.
2551 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2552 * Continuing and Stepping:: Resuming execution
2554 * Thread Stops:: Stopping and starting multi-thread programs
2558 @section Breakpoints, watchpoints, and catchpoints
2561 A @dfn{breakpoint} makes your program stop whenever a certain point in
2562 the program is reached. For each breakpoint, you can add conditions to
2563 control in finer detail whether your program stops. You can set
2564 breakpoints with the @code{break} command and its variants (@pxref{Set
2565 Breaks, ,Setting breakpoints}), to specify the place where your program
2566 should stop by line number, function name or exact address in the
2569 On some systems, you can set breakpoints in shared libraries before
2570 the executable is run. There is a minor limitation on HP-UX systems:
2571 you must wait until the executable is run in order to set breakpoints
2572 in shared library routines that are not called directly by the program
2573 (for example, routines that are arguments in a @code{pthread_create}
2577 @cindex memory tracing
2578 @cindex breakpoint on memory address
2579 @cindex breakpoint on variable modification
2580 A @dfn{watchpoint} is a special breakpoint that stops your program
2581 when the value of an expression changes. You must use a different
2582 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
2583 watchpoints}), but aside from that, you can manage a watchpoint like
2584 any other breakpoint: you enable, disable, and delete both breakpoints
2585 and watchpoints using the same commands.
2587 You can arrange to have values from your program displayed automatically
2588 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2592 @cindex breakpoint on events
2593 A @dfn{catchpoint} is another special breakpoint that stops your program
2594 when a certain kind of event occurs, such as the throwing of a C@t{++}
2595 exception or the loading of a library. As with watchpoints, you use a
2596 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2597 catchpoints}), but aside from that, you can manage a catchpoint like any
2598 other breakpoint. (To stop when your program receives a signal, use the
2599 @code{handle} command; see @ref{Signals, ,Signals}.)
2601 @cindex breakpoint numbers
2602 @cindex numbers for breakpoints
2603 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2604 catchpoint when you create it; these numbers are successive integers
2605 starting with one. In many of the commands for controlling various
2606 features of breakpoints you use the breakpoint number to say which
2607 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2608 @dfn{disabled}; if disabled, it has no effect on your program until you
2611 @cindex breakpoint ranges
2612 @cindex ranges of breakpoints
2613 Some @value{GDBN} commands accept a range of breakpoints on which to
2614 operate. A breakpoint range is either a single breakpoint number, like
2615 @samp{5}, or two such numbers, in increasing order, separated by a
2616 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2617 all breakpoint in that range are operated on.
2620 * Set Breaks:: Setting breakpoints
2621 * Set Watchpoints:: Setting watchpoints
2622 * Set Catchpoints:: Setting catchpoints
2623 * Delete Breaks:: Deleting breakpoints
2624 * Disabling:: Disabling breakpoints
2625 * Conditions:: Break conditions
2626 * Break Commands:: Breakpoint command lists
2627 * Breakpoint Menus:: Breakpoint menus
2628 * Error in Breakpoints:: ``Cannot insert breakpoints''
2629 * Breakpoint related warnings:: ``Breakpoint address adjusted...''
2633 @subsection Setting breakpoints
2635 @c FIXME LMB what does GDB do if no code on line of breakpt?
2636 @c consider in particular declaration with/without initialization.
2638 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2641 @kindex b @r{(@code{break})}
2642 @vindex $bpnum@r{, convenience variable}
2643 @cindex latest breakpoint
2644 Breakpoints are set with the @code{break} command (abbreviated
2645 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2646 number of the breakpoint you've set most recently; see @ref{Convenience
2647 Vars,, Convenience variables}, for a discussion of what you can do with
2648 convenience variables.
2650 You have several ways to say where the breakpoint should go.
2653 @item break @var{function}
2654 Set a breakpoint at entry to function @var{function}.
2655 When using source languages that permit overloading of symbols, such as
2656 C@t{++}, @var{function} may refer to more than one possible place to break.
2657 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2659 @item break +@var{offset}
2660 @itemx break -@var{offset}
2661 Set a breakpoint some number of lines forward or back from the position
2662 at which execution stopped in the currently selected @dfn{stack frame}.
2663 (@xref{Frames, ,Frames}, for a description of stack frames.)
2665 @item break @var{linenum}
2666 Set a breakpoint at line @var{linenum} in the current source file.
2667 The current source file is the last file whose source text was printed.
2668 The breakpoint will stop your program just before it executes any of the
2671 @item break @var{filename}:@var{linenum}
2672 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2674 @item break @var{filename}:@var{function}
2675 Set a breakpoint at entry to function @var{function} found in file
2676 @var{filename}. Specifying a file name as well as a function name is
2677 superfluous except when multiple files contain similarly named
2680 @item break *@var{address}
2681 Set a breakpoint at address @var{address}. You can use this to set
2682 breakpoints in parts of your program which do not have debugging
2683 information or source files.
2686 When called without any arguments, @code{break} sets a breakpoint at
2687 the next instruction to be executed in the selected stack frame
2688 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2689 innermost, this makes your program stop as soon as control
2690 returns to that frame. This is similar to the effect of a
2691 @code{finish} command in the frame inside the selected frame---except
2692 that @code{finish} does not leave an active breakpoint. If you use
2693 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2694 the next time it reaches the current location; this may be useful
2697 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2698 least one instruction has been executed. If it did not do this, you
2699 would be unable to proceed past a breakpoint without first disabling the
2700 breakpoint. This rule applies whether or not the breakpoint already
2701 existed when your program stopped.
2703 @item break @dots{} if @var{cond}
2704 Set a breakpoint with condition @var{cond}; evaluate the expression
2705 @var{cond} each time the breakpoint is reached, and stop only if the
2706 value is nonzero---that is, if @var{cond} evaluates as true.
2707 @samp{@dots{}} stands for one of the possible arguments described
2708 above (or no argument) specifying where to break. @xref{Conditions,
2709 ,Break conditions}, for more information on breakpoint conditions.
2712 @item tbreak @var{args}
2713 Set a breakpoint enabled only for one stop. @var{args} are the
2714 same as for the @code{break} command, and the breakpoint is set in the same
2715 way, but the breakpoint is automatically deleted after the first time your
2716 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2719 @cindex hardware breakpoints
2720 @item hbreak @var{args}
2721 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2722 @code{break} command and the breakpoint is set in the same way, but the
2723 breakpoint requires hardware support and some target hardware may not
2724 have this support. The main purpose of this is EPROM/ROM code
2725 debugging, so you can set a breakpoint at an instruction without
2726 changing the instruction. This can be used with the new trap-generation
2727 provided by SPARClite DSU and most x86-based targets. These targets
2728 will generate traps when a program accesses some data or instruction
2729 address that is assigned to the debug registers. However the hardware
2730 breakpoint registers can take a limited number of breakpoints. For
2731 example, on the DSU, only two data breakpoints can be set at a time, and
2732 @value{GDBN} will reject this command if more than two are used. Delete
2733 or disable unused hardware breakpoints before setting new ones
2734 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2735 For remote targets, you can restrict the number of hardware
2736 breakpoints @value{GDBN} will use, see @ref{set remote
2737 hardware-breakpoint-limit}.
2741 @item thbreak @var{args}
2742 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2743 are the same as for the @code{hbreak} command and the breakpoint is set in
2744 the same way. However, like the @code{tbreak} command,
2745 the breakpoint is automatically deleted after the
2746 first time your program stops there. Also, like the @code{hbreak}
2747 command, the breakpoint requires hardware support and some target hardware
2748 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2749 See also @ref{Conditions, ,Break conditions}.
2752 @cindex regular expression
2753 @cindex breakpoints in functions matching a regexp
2754 @cindex set breakpoints in many functions
2755 @item rbreak @var{regex}
2756 Set breakpoints on all functions matching the regular expression
2757 @var{regex}. This command sets an unconditional breakpoint on all
2758 matches, printing a list of all breakpoints it set. Once these
2759 breakpoints are set, they are treated just like the breakpoints set with
2760 the @code{break} command. You can delete them, disable them, or make
2761 them conditional the same way as any other breakpoint.
2763 The syntax of the regular expression is the standard one used with tools
2764 like @file{grep}. Note that this is different from the syntax used by
2765 shells, so for instance @code{foo*} matches all functions that include
2766 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2767 @code{.*} leading and trailing the regular expression you supply, so to
2768 match only functions that begin with @code{foo}, use @code{^foo}.
2770 @cindex non-member C@t{++} functions, set breakpoint in
2771 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2772 breakpoints on overloaded functions that are not members of any special
2775 @cindex set breakpoints on all functions
2776 The @code{rbreak} command can be used to set breakpoints in
2777 @strong{all} the functions in a program, like this:
2780 (@value{GDBP}) rbreak .
2783 @kindex info breakpoints
2784 @cindex @code{$_} and @code{info breakpoints}
2785 @item info breakpoints @r{[}@var{n}@r{]}
2786 @itemx info break @r{[}@var{n}@r{]}
2787 @itemx info watchpoints @r{[}@var{n}@r{]}
2788 Print a table of all breakpoints, watchpoints, and catchpoints set and
2789 not deleted, with the following columns for each breakpoint:
2792 @item Breakpoint Numbers
2794 Breakpoint, watchpoint, or catchpoint.
2796 Whether the breakpoint is marked to be disabled or deleted when hit.
2797 @item Enabled or Disabled
2798 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2799 that are not enabled.
2801 Where the breakpoint is in your program, as a memory address. If the
2802 breakpoint is pending (see below for details) on a future load of a shared library, the address
2803 will be listed as @samp{<PENDING>}.
2805 Where the breakpoint is in the source for your program, as a file and
2806 line number. For a pending breakpoint, the original string passed to
2807 the breakpoint command will be listed as it cannot be resolved until
2808 the appropriate shared library is loaded in the future.
2812 If a breakpoint is conditional, @code{info break} shows the condition on
2813 the line following the affected breakpoint; breakpoint commands, if any,
2814 are listed after that. A pending breakpoint is allowed to have a condition
2815 specified for it. The condition is not parsed for validity until a shared
2816 library is loaded that allows the pending breakpoint to resolve to a
2820 @code{info break} with a breakpoint
2821 number @var{n} as argument lists only that breakpoint. The
2822 convenience variable @code{$_} and the default examining-address for
2823 the @code{x} command are set to the address of the last breakpoint
2824 listed (@pxref{Memory, ,Examining memory}).
2827 @code{info break} displays a count of the number of times the breakpoint
2828 has been hit. This is especially useful in conjunction with the
2829 @code{ignore} command. You can ignore a large number of breakpoint
2830 hits, look at the breakpoint info to see how many times the breakpoint
2831 was hit, and then run again, ignoring one less than that number. This
2832 will get you quickly to the last hit of that breakpoint.
2835 @value{GDBN} allows you to set any number of breakpoints at the same place in
2836 your program. There is nothing silly or meaningless about this. When
2837 the breakpoints are conditional, this is even useful
2838 (@pxref{Conditions, ,Break conditions}).
2840 @cindex pending breakpoints
2841 If a specified breakpoint location cannot be found, it may be due to the fact
2842 that the location is in a shared library that is yet to be loaded. In such
2843 a case, you may want @value{GDBN} to create a special breakpoint (known as
2844 a @dfn{pending breakpoint}) that
2845 attempts to resolve itself in the future when an appropriate shared library
2848 Pending breakpoints are useful to set at the start of your
2849 @value{GDBN} session for locations that you know will be dynamically loaded
2850 later by the program being debugged. When shared libraries are loaded,
2851 a check is made to see if the load resolves any pending breakpoint locations.
2852 If a pending breakpoint location gets resolved,
2853 a regular breakpoint is created and the original pending breakpoint is removed.
2855 @value{GDBN} provides some additional commands for controlling pending
2858 @kindex set breakpoint pending
2859 @kindex show breakpoint pending
2861 @item set breakpoint pending auto
2862 This is the default behavior. When @value{GDBN} cannot find the breakpoint
2863 location, it queries you whether a pending breakpoint should be created.
2865 @item set breakpoint pending on
2866 This indicates that an unrecognized breakpoint location should automatically
2867 result in a pending breakpoint being created.
2869 @item set breakpoint pending off
2870 This indicates that pending breakpoints are not to be created. Any
2871 unrecognized breakpoint location results in an error. This setting does
2872 not affect any pending breakpoints previously created.
2874 @item show breakpoint pending
2875 Show the current behavior setting for creating pending breakpoints.
2878 @cindex operations allowed on pending breakpoints
2879 Normal breakpoint operations apply to pending breakpoints as well. You may
2880 specify a condition for a pending breakpoint and/or commands to run when the
2881 breakpoint is reached. You can also enable or disable
2882 the pending breakpoint. When you specify a condition for a pending breakpoint,
2883 the parsing of the condition will be deferred until the point where the
2884 pending breakpoint location is resolved. Disabling a pending breakpoint
2885 tells @value{GDBN} to not attempt to resolve the breakpoint on any subsequent
2886 shared library load. When a pending breakpoint is re-enabled,
2887 @value{GDBN} checks to see if the location is already resolved.
2888 This is done because any number of shared library loads could have
2889 occurred since the time the breakpoint was disabled and one or more
2890 of these loads could resolve the location.
2892 @cindex negative breakpoint numbers
2893 @cindex internal @value{GDBN} breakpoints
2894 @value{GDBN} itself sometimes sets breakpoints in your program for
2895 special purposes, such as proper handling of @code{longjmp} (in C
2896 programs). These internal breakpoints are assigned negative numbers,
2897 starting with @code{-1}; @samp{info breakpoints} does not display them.
2898 You can see these breakpoints with the @value{GDBN} maintenance command
2899 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
2902 @node Set Watchpoints
2903 @subsection Setting watchpoints
2905 @cindex setting watchpoints
2906 You can use a watchpoint to stop execution whenever the value of an
2907 expression changes, without having to predict a particular place where
2910 @cindex software watchpoints
2911 @cindex hardware watchpoints
2912 Depending on your system, watchpoints may be implemented in software or
2913 hardware. @value{GDBN} does software watchpointing by single-stepping your
2914 program and testing the variable's value each time, which is hundreds of
2915 times slower than normal execution. (But this may still be worth it, to
2916 catch errors where you have no clue what part of your program is the
2919 On some systems, such as HP-UX, @sc{gnu}/Linux and most other
2920 x86-based targets, @value{GDBN} includes support for hardware
2921 watchpoints, which do not slow down the running of your program.
2925 @item watch @var{expr}
2926 Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
2927 is written into by the program and its value changes.
2930 @item rwatch @var{expr}
2931 Set a watchpoint that will break when the value of @var{expr} is read
2935 @item awatch @var{expr}
2936 Set a watchpoint that will break when @var{expr} is either read from
2937 or written into by the program.
2939 @kindex info watchpoints
2940 @item info watchpoints
2941 This command prints a list of watchpoints, breakpoints, and catchpoints;
2942 it is the same as @code{info break} (@pxref{Set Breaks}).
2945 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
2946 watchpoints execute very quickly, and the debugger reports a change in
2947 value at the exact instruction where the change occurs. If @value{GDBN}
2948 cannot set a hardware watchpoint, it sets a software watchpoint, which
2949 executes more slowly and reports the change in value at the next
2950 @emph{statement}, not the instruction, after the change occurs.
2952 @cindex use only software watchpoints
2953 You can force @value{GDBN} to use only software watchpoints with the
2954 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
2955 zero, @value{GDBN} will never try to use hardware watchpoints, even if
2956 the underlying system supports them. (Note that hardware-assisted
2957 watchpoints that were set @emph{before} setting
2958 @code{can-use-hw-watchpoints} to zero will still use the hardware
2959 mechanism of watching expressiion values.)
2962 @item set can-use-hw-watchpoints
2963 @kindex set can-use-hw-watchpoints
2964 Set whether or not to use hardware watchpoints.
2966 @item show can-use-hw-watchpoints
2967 @kindex show can-use-hw-watchpoints
2968 Show the current mode of using hardware watchpoints.
2971 For remote targets, you can restrict the number of hardware
2972 watchpoints @value{GDBN} will use, see @ref{set remote
2973 hardware-breakpoint-limit}.
2975 When you issue the @code{watch} command, @value{GDBN} reports
2978 Hardware watchpoint @var{num}: @var{expr}
2982 if it was able to set a hardware watchpoint.
2984 Currently, the @code{awatch} and @code{rwatch} commands can only set
2985 hardware watchpoints, because accesses to data that don't change the
2986 value of the watched expression cannot be detected without examining
2987 every instruction as it is being executed, and @value{GDBN} does not do
2988 that currently. If @value{GDBN} finds that it is unable to set a
2989 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
2990 will print a message like this:
2993 Expression cannot be implemented with read/access watchpoint.
2996 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
2997 data type of the watched expression is wider than what a hardware
2998 watchpoint on the target machine can handle. For example, some systems
2999 can only watch regions that are up to 4 bytes wide; on such systems you
3000 cannot set hardware watchpoints for an expression that yields a
3001 double-precision floating-point number (which is typically 8 bytes
3002 wide). As a work-around, it might be possible to break the large region
3003 into a series of smaller ones and watch them with separate watchpoints.
3005 If you set too many hardware watchpoints, @value{GDBN} might be unable
3006 to insert all of them when you resume the execution of your program.
3007 Since the precise number of active watchpoints is unknown until such
3008 time as the program is about to be resumed, @value{GDBN} might not be
3009 able to warn you about this when you set the watchpoints, and the
3010 warning will be printed only when the program is resumed:
3013 Hardware watchpoint @var{num}: Could not insert watchpoint
3017 If this happens, delete or disable some of the watchpoints.
3019 The SPARClite DSU will generate traps when a program accesses some data
3020 or instruction address that is assigned to the debug registers. For the
3021 data addresses, DSU facilitates the @code{watch} command. However the
3022 hardware breakpoint registers can only take two data watchpoints, and
3023 both watchpoints must be the same kind. For example, you can set two
3024 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
3025 @strong{or} two with @code{awatch} commands, but you cannot set one
3026 watchpoint with one command and the other with a different command.
3027 @value{GDBN} will reject the command if you try to mix watchpoints.
3028 Delete or disable unused watchpoint commands before setting new ones.
3030 If you call a function interactively using @code{print} or @code{call},
3031 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3032 kind of breakpoint or the call completes.
3034 @value{GDBN} automatically deletes watchpoints that watch local
3035 (automatic) variables, or expressions that involve such variables, when
3036 they go out of scope, that is, when the execution leaves the block in
3037 which these variables were defined. In particular, when the program
3038 being debugged terminates, @emph{all} local variables go out of scope,
3039 and so only watchpoints that watch global variables remain set. If you
3040 rerun the program, you will need to set all such watchpoints again. One
3041 way of doing that would be to set a code breakpoint at the entry to the
3042 @code{main} function and when it breaks, set all the watchpoints.
3045 @cindex watchpoints and threads
3046 @cindex threads and watchpoints
3047 @emph{Warning:} In multi-thread programs, watchpoints have only limited
3048 usefulness. With the current watchpoint implementation, @value{GDBN}
3049 can only watch the value of an expression @emph{in a single thread}. If
3050 you are confident that the expression can only change due to the current
3051 thread's activity (and if you are also confident that no other thread
3052 can become current), then you can use watchpoints as usual. However,
3053 @value{GDBN} may not notice when a non-current thread's activity changes
3056 @c FIXME: this is almost identical to the previous paragraph.
3057 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
3058 have only limited usefulness. If @value{GDBN} creates a software
3059 watchpoint, it can only watch the value of an expression @emph{in a
3060 single thread}. If you are confident that the expression can only
3061 change due to the current thread's activity (and if you are also
3062 confident that no other thread can become current), then you can use
3063 software watchpoints as usual. However, @value{GDBN} may not notice
3064 when a non-current thread's activity changes the expression. (Hardware
3065 watchpoints, in contrast, watch an expression in all threads.)
3068 @xref{set remote hardware-watchpoint-limit}.
3070 @node Set Catchpoints
3071 @subsection Setting catchpoints
3072 @cindex catchpoints, setting
3073 @cindex exception handlers
3074 @cindex event handling
3076 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3077 kinds of program events, such as C@t{++} exceptions or the loading of a
3078 shared library. Use the @code{catch} command to set a catchpoint.
3082 @item catch @var{event}
3083 Stop when @var{event} occurs. @var{event} can be any of the following:
3086 @cindex stop on C@t{++} exceptions
3087 The throwing of a C@t{++} exception.
3090 The catching of a C@t{++} exception.
3093 @cindex break on fork/exec
3094 A call to @code{exec}. This is currently only available for HP-UX.
3097 A call to @code{fork}. This is currently only available for HP-UX.
3100 A call to @code{vfork}. This is currently only available for HP-UX.
3103 @itemx load @var{libname}
3104 @cindex break on load/unload of shared library
3105 The dynamic loading of any shared library, or the loading of the library
3106 @var{libname}. This is currently only available for HP-UX.
3109 @itemx unload @var{libname}
3110 The unloading of any dynamically loaded shared library, or the unloading
3111 of the library @var{libname}. This is currently only available for HP-UX.
3114 @item tcatch @var{event}
3115 Set a catchpoint that is enabled only for one stop. The catchpoint is
3116 automatically deleted after the first time the event is caught.
3120 Use the @code{info break} command to list the current catchpoints.
3122 There are currently some limitations to C@t{++} exception handling
3123 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3127 If you call a function interactively, @value{GDBN} normally returns
3128 control to you when the function has finished executing. If the call
3129 raises an exception, however, the call may bypass the mechanism that
3130 returns control to you and cause your program either to abort or to
3131 simply continue running until it hits a breakpoint, catches a signal
3132 that @value{GDBN} is listening for, or exits. This is the case even if
3133 you set a catchpoint for the exception; catchpoints on exceptions are
3134 disabled within interactive calls.
3137 You cannot raise an exception interactively.
3140 You cannot install an exception handler interactively.
3143 @cindex raise exceptions
3144 Sometimes @code{catch} is not the best way to debug exception handling:
3145 if you need to know exactly where an exception is raised, it is better to
3146 stop @emph{before} the exception handler is called, since that way you
3147 can see the stack before any unwinding takes place. If you set a
3148 breakpoint in an exception handler instead, it may not be easy to find
3149 out where the exception was raised.
3151 To stop just before an exception handler is called, you need some
3152 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3153 raised by calling a library function named @code{__raise_exception}
3154 which has the following ANSI C interface:
3157 /* @var{addr} is where the exception identifier is stored.
3158 @var{id} is the exception identifier. */
3159 void __raise_exception (void **addr, void *id);
3163 To make the debugger catch all exceptions before any stack
3164 unwinding takes place, set a breakpoint on @code{__raise_exception}
3165 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
3167 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
3168 that depends on the value of @var{id}, you can stop your program when
3169 a specific exception is raised. You can use multiple conditional
3170 breakpoints to stop your program when any of a number of exceptions are
3175 @subsection Deleting breakpoints
3177 @cindex clearing breakpoints, watchpoints, catchpoints
3178 @cindex deleting breakpoints, watchpoints, catchpoints
3179 It is often necessary to eliminate a breakpoint, watchpoint, or
3180 catchpoint once it has done its job and you no longer want your program
3181 to stop there. This is called @dfn{deleting} the breakpoint. A
3182 breakpoint that has been deleted no longer exists; it is forgotten.
3184 With the @code{clear} command you can delete breakpoints according to
3185 where they are in your program. With the @code{delete} command you can
3186 delete individual breakpoints, watchpoints, or catchpoints by specifying
3187 their breakpoint numbers.
3189 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3190 automatically ignores breakpoints on the first instruction to be executed
3191 when you continue execution without changing the execution address.
3196 Delete any breakpoints at the next instruction to be executed in the
3197 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
3198 the innermost frame is selected, this is a good way to delete a
3199 breakpoint where your program just stopped.
3201 @item clear @var{function}
3202 @itemx clear @var{filename}:@var{function}
3203 Delete any breakpoints set at entry to the named @var{function}.
3205 @item clear @var{linenum}
3206 @itemx clear @var{filename}:@var{linenum}
3207 Delete any breakpoints set at or within the code of the specified
3208 @var{linenum} of the specified @var{filename}.
3210 @cindex delete breakpoints
3212 @kindex d @r{(@code{delete})}
3213 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3214 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3215 ranges specified as arguments. If no argument is specified, delete all
3216 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3217 confirm off}). You can abbreviate this command as @code{d}.
3221 @subsection Disabling breakpoints
3223 @cindex enable/disable a breakpoint
3224 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3225 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3226 it had been deleted, but remembers the information on the breakpoint so
3227 that you can @dfn{enable} it again later.
3229 You disable and enable breakpoints, watchpoints, and catchpoints with
3230 the @code{enable} and @code{disable} commands, optionally specifying one
3231 or more breakpoint numbers as arguments. Use @code{info break} or
3232 @code{info watch} to print a list of breakpoints, watchpoints, and
3233 catchpoints if you do not know which numbers to use.
3235 A breakpoint, watchpoint, or catchpoint can have any of four different
3236 states of enablement:
3240 Enabled. The breakpoint stops your program. A breakpoint set
3241 with the @code{break} command starts out in this state.
3243 Disabled. The breakpoint has no effect on your program.
3245 Enabled once. The breakpoint stops your program, but then becomes
3248 Enabled for deletion. The breakpoint stops your program, but
3249 immediately after it does so it is deleted permanently. A breakpoint
3250 set with the @code{tbreak} command starts out in this state.
3253 You can use the following commands to enable or disable breakpoints,
3254 watchpoints, and catchpoints:
3258 @kindex dis @r{(@code{disable})}
3259 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3260 Disable the specified breakpoints---or all breakpoints, if none are
3261 listed. A disabled breakpoint has no effect but is not forgotten. All
3262 options such as ignore-counts, conditions and commands are remembered in
3263 case the breakpoint is enabled again later. You may abbreviate
3264 @code{disable} as @code{dis}.
3267 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3268 Enable the specified breakpoints (or all defined breakpoints). They
3269 become effective once again in stopping your program.
3271 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3272 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3273 of these breakpoints immediately after stopping your program.
3275 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3276 Enable the specified breakpoints to work once, then die. @value{GDBN}
3277 deletes any of these breakpoints as soon as your program stops there.
3278 Breakpoints set by the @code{tbreak} command start out in this state.
3281 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3282 @c confusing: tbreak is also initially enabled.
3283 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3284 ,Setting breakpoints}), breakpoints that you set are initially enabled;
3285 subsequently, they become disabled or enabled only when you use one of
3286 the commands above. (The command @code{until} can set and delete a
3287 breakpoint of its own, but it does not change the state of your other
3288 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3292 @subsection Break conditions
3293 @cindex conditional breakpoints
3294 @cindex breakpoint conditions
3296 @c FIXME what is scope of break condition expr? Context where wanted?
3297 @c in particular for a watchpoint?
3298 The simplest sort of breakpoint breaks every time your program reaches a
3299 specified place. You can also specify a @dfn{condition} for a
3300 breakpoint. A condition is just a Boolean expression in your
3301 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3302 a condition evaluates the expression each time your program reaches it,
3303 and your program stops only if the condition is @emph{true}.
3305 This is the converse of using assertions for program validation; in that
3306 situation, you want to stop when the assertion is violated---that is,
3307 when the condition is false. In C, if you want to test an assertion expressed
3308 by the condition @var{assert}, you should set the condition
3309 @samp{! @var{assert}} on the appropriate breakpoint.
3311 Conditions are also accepted for watchpoints; you may not need them,
3312 since a watchpoint is inspecting the value of an expression anyhow---but
3313 it might be simpler, say, to just set a watchpoint on a variable name,
3314 and specify a condition that tests whether the new value is an interesting
3317 Break conditions can have side effects, and may even call functions in
3318 your program. This can be useful, for example, to activate functions
3319 that log program progress, or to use your own print functions to
3320 format special data structures. The effects are completely predictable
3321 unless there is another enabled breakpoint at the same address. (In
3322 that case, @value{GDBN} might see the other breakpoint first and stop your
3323 program without checking the condition of this one.) Note that
3324 breakpoint commands are usually more convenient and flexible than break
3326 purpose of performing side effects when a breakpoint is reached
3327 (@pxref{Break Commands, ,Breakpoint command lists}).
3329 Break conditions can be specified when a breakpoint is set, by using
3330 @samp{if} in the arguments to the @code{break} command. @xref{Set
3331 Breaks, ,Setting breakpoints}. They can also be changed at any time
3332 with the @code{condition} command.
3334 You can also use the @code{if} keyword with the @code{watch} command.
3335 The @code{catch} command does not recognize the @code{if} keyword;
3336 @code{condition} is the only way to impose a further condition on a
3341 @item condition @var{bnum} @var{expression}
3342 Specify @var{expression} as the break condition for breakpoint,
3343 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3344 breakpoint @var{bnum} stops your program only if the value of
3345 @var{expression} is true (nonzero, in C). When you use
3346 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3347 syntactic correctness, and to determine whether symbols in it have
3348 referents in the context of your breakpoint. If @var{expression} uses
3349 symbols not referenced in the context of the breakpoint, @value{GDBN}
3350 prints an error message:
3353 No symbol "foo" in current context.
3358 not actually evaluate @var{expression} at the time the @code{condition}
3359 command (or a command that sets a breakpoint with a condition, like
3360 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3362 @item condition @var{bnum}
3363 Remove the condition from breakpoint number @var{bnum}. It becomes
3364 an ordinary unconditional breakpoint.
3367 @cindex ignore count (of breakpoint)
3368 A special case of a breakpoint condition is to stop only when the
3369 breakpoint has been reached a certain number of times. This is so
3370 useful that there is a special way to do it, using the @dfn{ignore
3371 count} of the breakpoint. Every breakpoint has an ignore count, which
3372 is an integer. Most of the time, the ignore count is zero, and
3373 therefore has no effect. But if your program reaches a breakpoint whose
3374 ignore count is positive, then instead of stopping, it just decrements
3375 the ignore count by one and continues. As a result, if the ignore count
3376 value is @var{n}, the breakpoint does not stop the next @var{n} times
3377 your program reaches it.
3381 @item ignore @var{bnum} @var{count}
3382 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3383 The next @var{count} times the breakpoint is reached, your program's
3384 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3387 To make the breakpoint stop the next time it is reached, specify
3390 When you use @code{continue} to resume execution of your program from a
3391 breakpoint, you can specify an ignore count directly as an argument to
3392 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3393 Stepping,,Continuing and stepping}.
3395 If a breakpoint has a positive ignore count and a condition, the
3396 condition is not checked. Once the ignore count reaches zero,
3397 @value{GDBN} resumes checking the condition.
3399 You could achieve the effect of the ignore count with a condition such
3400 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3401 is decremented each time. @xref{Convenience Vars, ,Convenience
3405 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3408 @node Break Commands
3409 @subsection Breakpoint command lists
3411 @cindex breakpoint commands
3412 You can give any breakpoint (or watchpoint or catchpoint) a series of
3413 commands to execute when your program stops due to that breakpoint. For
3414 example, you might want to print the values of certain expressions, or
3415 enable other breakpoints.
3420 @item commands @r{[}@var{bnum}@r{]}
3421 @itemx @dots{} @var{command-list} @dots{}
3423 Specify a list of commands for breakpoint number @var{bnum}. The commands
3424 themselves appear on the following lines. Type a line containing just
3425 @code{end} to terminate the commands.
3427 To remove all commands from a breakpoint, type @code{commands} and
3428 follow it immediately with @code{end}; that is, give no commands.
3430 With no @var{bnum} argument, @code{commands} refers to the last
3431 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3432 recently encountered).
3435 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3436 disabled within a @var{command-list}.
3438 You can use breakpoint commands to start your program up again. Simply
3439 use the @code{continue} command, or @code{step}, or any other command
3440 that resumes execution.
3442 Any other commands in the command list, after a command that resumes
3443 execution, are ignored. This is because any time you resume execution
3444 (even with a simple @code{next} or @code{step}), you may encounter
3445 another breakpoint---which could have its own command list, leading to
3446 ambiguities about which list to execute.
3449 If the first command you specify in a command list is @code{silent}, the
3450 usual message about stopping at a breakpoint is not printed. This may
3451 be desirable for breakpoints that are to print a specific message and
3452 then continue. If none of the remaining commands print anything, you
3453 see no sign that the breakpoint was reached. @code{silent} is
3454 meaningful only at the beginning of a breakpoint command list.
3456 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3457 print precisely controlled output, and are often useful in silent
3458 breakpoints. @xref{Output, ,Commands for controlled output}.
3460 For example, here is how you could use breakpoint commands to print the
3461 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3467 printf "x is %d\n",x
3472 One application for breakpoint commands is to compensate for one bug so
3473 you can test for another. Put a breakpoint just after the erroneous line
3474 of code, give it a condition to detect the case in which something
3475 erroneous has been done, and give it commands to assign correct values
3476 to any variables that need them. End with the @code{continue} command
3477 so that your program does not stop, and start with the @code{silent}
3478 command so that no output is produced. Here is an example:
3489 @node Breakpoint Menus
3490 @subsection Breakpoint menus
3492 @cindex symbol overloading
3494 Some programming languages (notably C@t{++} and Objective-C) permit a
3495 single function name
3496 to be defined several times, for application in different contexts.
3497 This is called @dfn{overloading}. When a function name is overloaded,
3498 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3499 a breakpoint. If you realize this is a problem, you can use
3500 something like @samp{break @var{function}(@var{types})} to specify which
3501 particular version of the function you want. Otherwise, @value{GDBN} offers
3502 you a menu of numbered choices for different possible breakpoints, and
3503 waits for your selection with the prompt @samp{>}. The first two
3504 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3505 sets a breakpoint at each definition of @var{function}, and typing
3506 @kbd{0} aborts the @code{break} command without setting any new
3509 For example, the following session excerpt shows an attempt to set a
3510 breakpoint at the overloaded symbol @code{String::after}.
3511 We choose three particular definitions of that function name:
3513 @c FIXME! This is likely to change to show arg type lists, at least
3516 (@value{GDBP}) b String::after
3519 [2] file:String.cc; line number:867
3520 [3] file:String.cc; line number:860
3521 [4] file:String.cc; line number:875
3522 [5] file:String.cc; line number:853
3523 [6] file:String.cc; line number:846
3524 [7] file:String.cc; line number:735
3526 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3527 Breakpoint 2 at 0xb344: file String.cc, line 875.
3528 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3529 Multiple breakpoints were set.
3530 Use the "delete" command to delete unwanted
3536 @c @ifclear BARETARGET
3537 @node Error in Breakpoints
3538 @subsection ``Cannot insert breakpoints''
3540 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3542 Under some operating systems, breakpoints cannot be used in a program if
3543 any other process is running that program. In this situation,
3544 attempting to run or continue a program with a breakpoint causes
3545 @value{GDBN} to print an error message:
3548 Cannot insert breakpoints.
3549 The same program may be running in another process.
3552 When this happens, you have three ways to proceed:
3556 Remove or disable the breakpoints, then continue.
3559 Suspend @value{GDBN}, and copy the file containing your program to a new
3560 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3561 that @value{GDBN} should run your program under that name.
3562 Then start your program again.
3565 Relink your program so that the text segment is nonsharable, using the
3566 linker option @samp{-N}. The operating system limitation may not apply
3567 to nonsharable executables.
3571 A similar message can be printed if you request too many active
3572 hardware-assisted breakpoints and watchpoints:
3574 @c FIXME: the precise wording of this message may change; the relevant
3575 @c source change is not committed yet (Sep 3, 1999).
3577 Stopped; cannot insert breakpoints.
3578 You may have requested too many hardware breakpoints and watchpoints.
3582 This message is printed when you attempt to resume the program, since
3583 only then @value{GDBN} knows exactly how many hardware breakpoints and
3584 watchpoints it needs to insert.
3586 When this message is printed, you need to disable or remove some of the
3587 hardware-assisted breakpoints and watchpoints, and then continue.
3589 @node Breakpoint related warnings
3590 @subsection ``Breakpoint address adjusted...''
3591 @cindex breakpoint address adjusted
3593 Some processor architectures place constraints on the addresses at
3594 which breakpoints may be placed. For architectures thus constrained,
3595 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3596 with the constraints dictated by the architecture.
3598 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3599 a VLIW architecture in which a number of RISC-like instructions may be
3600 bundled together for parallel execution. The FR-V architecture
3601 constrains the location of a breakpoint instruction within such a
3602 bundle to the instruction with the lowest address. @value{GDBN}
3603 honors this constraint by adjusting a breakpoint's address to the
3604 first in the bundle.
3606 It is not uncommon for optimized code to have bundles which contain
3607 instructions from different source statements, thus it may happen that
3608 a breakpoint's address will be adjusted from one source statement to
3609 another. Since this adjustment may significantly alter @value{GDBN}'s
3610 breakpoint related behavior from what the user expects, a warning is
3611 printed when the breakpoint is first set and also when the breakpoint
3614 A warning like the one below is printed when setting a breakpoint
3615 that's been subject to address adjustment:
3618 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3621 Such warnings are printed both for user settable and @value{GDBN}'s
3622 internal breakpoints. If you see one of these warnings, you should
3623 verify that a breakpoint set at the adjusted address will have the
3624 desired affect. If not, the breakpoint in question may be removed and
3625 other breakpoints may be set which will have the desired behavior.
3626 E.g., it may be sufficient to place the breakpoint at a later
3627 instruction. A conditional breakpoint may also be useful in some
3628 cases to prevent the breakpoint from triggering too often.
3630 @value{GDBN} will also issue a warning when stopping at one of these
3631 adjusted breakpoints:
3634 warning: Breakpoint 1 address previously adjusted from 0x00010414
3638 When this warning is encountered, it may be too late to take remedial
3639 action except in cases where the breakpoint is hit earlier or more
3640 frequently than expected.
3642 @node Continuing and Stepping
3643 @section Continuing and stepping
3647 @cindex resuming execution
3648 @dfn{Continuing} means resuming program execution until your program
3649 completes normally. In contrast, @dfn{stepping} means executing just
3650 one more ``step'' of your program, where ``step'' may mean either one
3651 line of source code, or one machine instruction (depending on what
3652 particular command you use). Either when continuing or when stepping,
3653 your program may stop even sooner, due to a breakpoint or a signal. (If
3654 it stops due to a signal, you may want to use @code{handle}, or use
3655 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3659 @kindex c @r{(@code{continue})}
3660 @kindex fg @r{(resume foreground execution)}
3661 @item continue @r{[}@var{ignore-count}@r{]}
3662 @itemx c @r{[}@var{ignore-count}@r{]}
3663 @itemx fg @r{[}@var{ignore-count}@r{]}
3664 Resume program execution, at the address where your program last stopped;
3665 any breakpoints set at that address are bypassed. The optional argument
3666 @var{ignore-count} allows you to specify a further number of times to
3667 ignore a breakpoint at this location; its effect is like that of
3668 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3670 The argument @var{ignore-count} is meaningful only when your program
3671 stopped due to a breakpoint. At other times, the argument to
3672 @code{continue} is ignored.
3674 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3675 debugged program is deemed to be the foreground program) are provided
3676 purely for convenience, and have exactly the same behavior as
3680 To resume execution at a different place, you can use @code{return}
3681 (@pxref{Returning, ,Returning from a function}) to go back to the
3682 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3683 different address}) to go to an arbitrary location in your program.
3685 A typical technique for using stepping is to set a breakpoint
3686 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3687 beginning of the function or the section of your program where a problem
3688 is believed to lie, run your program until it stops at that breakpoint,
3689 and then step through the suspect area, examining the variables that are
3690 interesting, until you see the problem happen.
3694 @kindex s @r{(@code{step})}
3696 Continue running your program until control reaches a different source
3697 line, then stop it and return control to @value{GDBN}. This command is
3698 abbreviated @code{s}.
3701 @c "without debugging information" is imprecise; actually "without line
3702 @c numbers in the debugging information". (gcc -g1 has debugging info but
3703 @c not line numbers). But it seems complex to try to make that
3704 @c distinction here.
3705 @emph{Warning:} If you use the @code{step} command while control is
3706 within a function that was compiled without debugging information,
3707 execution proceeds until control reaches a function that does have
3708 debugging information. Likewise, it will not step into a function which
3709 is compiled without debugging information. To step through functions
3710 without debugging information, use the @code{stepi} command, described
3714 The @code{step} command only stops at the first instruction of a source
3715 line. This prevents the multiple stops that could otherwise occur in
3716 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3717 to stop if a function that has debugging information is called within
3718 the line. In other words, @code{step} @emph{steps inside} any functions
3719 called within the line.
3721 Also, the @code{step} command only enters a function if there is line
3722 number information for the function. Otherwise it acts like the
3723 @code{next} command. This avoids problems when using @code{cc -gl}
3724 on MIPS machines. Previously, @code{step} entered subroutines if there
3725 was any debugging information about the routine.
3727 @item step @var{count}
3728 Continue running as in @code{step}, but do so @var{count} times. If a
3729 breakpoint is reached, or a signal not related to stepping occurs before
3730 @var{count} steps, stepping stops right away.
3733 @kindex n @r{(@code{next})}
3734 @item next @r{[}@var{count}@r{]}
3735 Continue to the next source line in the current (innermost) stack frame.
3736 This is similar to @code{step}, but function calls that appear within
3737 the line of code are executed without stopping. Execution stops when
3738 control reaches a different line of code at the original stack level
3739 that was executing when you gave the @code{next} command. This command
3740 is abbreviated @code{n}.
3742 An argument @var{count} is a repeat count, as for @code{step}.
3745 @c FIX ME!! Do we delete this, or is there a way it fits in with
3746 @c the following paragraph? --- Vctoria
3748 @c @code{next} within a function that lacks debugging information acts like
3749 @c @code{step}, but any function calls appearing within the code of the
3750 @c function are executed without stopping.
3752 The @code{next} command only stops at the first instruction of a
3753 source line. This prevents multiple stops that could otherwise occur in
3754 @code{switch} statements, @code{for} loops, etc.
3756 @kindex set step-mode
3758 @cindex functions without line info, and stepping
3759 @cindex stepping into functions with no line info
3760 @itemx set step-mode on
3761 The @code{set step-mode on} command causes the @code{step} command to
3762 stop at the first instruction of a function which contains no debug line
3763 information rather than stepping over it.
3765 This is useful in cases where you may be interested in inspecting the
3766 machine instructions of a function which has no symbolic info and do not
3767 want @value{GDBN} to automatically skip over this function.
3769 @item set step-mode off
3770 Causes the @code{step} command to step over any functions which contains no
3771 debug information. This is the default.
3773 @item show step-mode
3774 Show whether @value{GDBN} will stop in or step over functions without
3775 source line debug information.
3779 Continue running until just after function in the selected stack frame
3780 returns. Print the returned value (if any).
3782 Contrast this with the @code{return} command (@pxref{Returning,
3783 ,Returning from a function}).
3786 @kindex u @r{(@code{until})}
3787 @cindex run until specified location
3790 Continue running until a source line past the current line, in the
3791 current stack frame, is reached. This command is used to avoid single
3792 stepping through a loop more than once. It is like the @code{next}
3793 command, except that when @code{until} encounters a jump, it
3794 automatically continues execution until the program counter is greater
3795 than the address of the jump.
3797 This means that when you reach the end of a loop after single stepping
3798 though it, @code{until} makes your program continue execution until it
3799 exits the loop. In contrast, a @code{next} command at the end of a loop
3800 simply steps back to the beginning of the loop, which forces you to step
3801 through the next iteration.
3803 @code{until} always stops your program if it attempts to exit the current
3806 @code{until} may produce somewhat counterintuitive results if the order
3807 of machine code does not match the order of the source lines. For
3808 example, in the following excerpt from a debugging session, the @code{f}
3809 (@code{frame}) command shows that execution is stopped at line
3810 @code{206}; yet when we use @code{until}, we get to line @code{195}:
3814 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
3816 (@value{GDBP}) until
3817 195 for ( ; argc > 0; NEXTARG) @{
3820 This happened because, for execution efficiency, the compiler had
3821 generated code for the loop closure test at the end, rather than the
3822 start, of the loop---even though the test in a C @code{for}-loop is
3823 written before the body of the loop. The @code{until} command appeared
3824 to step back to the beginning of the loop when it advanced to this
3825 expression; however, it has not really gone to an earlier
3826 statement---not in terms of the actual machine code.
3828 @code{until} with no argument works by means of single
3829 instruction stepping, and hence is slower than @code{until} with an
3832 @item until @var{location}
3833 @itemx u @var{location}
3834 Continue running your program until either the specified location is
3835 reached, or the current stack frame returns. @var{location} is any of
3836 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
3837 ,Setting breakpoints}). This form of the command uses breakpoints, and
3838 hence is quicker than @code{until} without an argument. The specified
3839 location is actually reached only if it is in the current frame. This
3840 implies that @code{until} can be used to skip over recursive function
3841 invocations. For instance in the code below, if the current location is
3842 line @code{96}, issuing @code{until 99} will execute the program up to
3843 line @code{99} in the same invocation of factorial, i.e. after the inner
3844 invocations have returned.
3847 94 int factorial (int value)
3849 96 if (value > 1) @{
3850 97 value *= factorial (value - 1);
3857 @kindex advance @var{location}
3858 @itemx advance @var{location}
3859 Continue running the program up to the given @var{location}. An argument is
3860 required, which should be of the same form as arguments for the @code{break}
3861 command. Execution will also stop upon exit from the current stack
3862 frame. This command is similar to @code{until}, but @code{advance} will
3863 not skip over recursive function calls, and the target location doesn't
3864 have to be in the same frame as the current one.
3868 @kindex si @r{(@code{stepi})}
3870 @itemx stepi @var{arg}
3872 Execute one machine instruction, then stop and return to the debugger.
3874 It is often useful to do @samp{display/i $pc} when stepping by machine
3875 instructions. This makes @value{GDBN} automatically display the next
3876 instruction to be executed, each time your program stops. @xref{Auto
3877 Display,, Automatic display}.
3879 An argument is a repeat count, as in @code{step}.
3883 @kindex ni @r{(@code{nexti})}
3885 @itemx nexti @var{arg}
3887 Execute one machine instruction, but if it is a function call,
3888 proceed until the function returns.
3890 An argument is a repeat count, as in @code{next}.
3897 A signal is an asynchronous event that can happen in a program. The
3898 operating system defines the possible kinds of signals, and gives each
3899 kind a name and a number. For example, in Unix @code{SIGINT} is the
3900 signal a program gets when you type an interrupt character (often @kbd{C-c});
3901 @code{SIGSEGV} is the signal a program gets from referencing a place in
3902 memory far away from all the areas in use; @code{SIGALRM} occurs when
3903 the alarm clock timer goes off (which happens only if your program has
3904 requested an alarm).
3906 @cindex fatal signals
3907 Some signals, including @code{SIGALRM}, are a normal part of the
3908 functioning of your program. Others, such as @code{SIGSEGV}, indicate
3909 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
3910 program has not specified in advance some other way to handle the signal.
3911 @code{SIGINT} does not indicate an error in your program, but it is normally
3912 fatal so it can carry out the purpose of the interrupt: to kill the program.
3914 @value{GDBN} has the ability to detect any occurrence of a signal in your
3915 program. You can tell @value{GDBN} in advance what to do for each kind of
3918 @cindex handling signals
3919 Normally, @value{GDBN} is set up to let the non-erroneous signals like
3920 @code{SIGALRM} be silently passed to your program
3921 (so as not to interfere with their role in the program's functioning)
3922 but to stop your program immediately whenever an error signal happens.
3923 You can change these settings with the @code{handle} command.
3926 @kindex info signals
3930 Print a table of all the kinds of signals and how @value{GDBN} has been told to
3931 handle each one. You can use this to see the signal numbers of all
3932 the defined types of signals.
3934 @code{info handle} is an alias for @code{info signals}.
3937 @item handle @var{signal} @var{keywords}@dots{}
3938 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
3939 can be the number of a signal or its name (with or without the
3940 @samp{SIG} at the beginning); a list of signal numbers of the form
3941 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
3942 known signals. The @var{keywords} say what change to make.
3946 The keywords allowed by the @code{handle} command can be abbreviated.
3947 Their full names are:
3951 @value{GDBN} should not stop your program when this signal happens. It may
3952 still print a message telling you that the signal has come in.
3955 @value{GDBN} should stop your program when this signal happens. This implies
3956 the @code{print} keyword as well.
3959 @value{GDBN} should print a message when this signal happens.
3962 @value{GDBN} should not mention the occurrence of the signal at all. This
3963 implies the @code{nostop} keyword as well.
3967 @value{GDBN} should allow your program to see this signal; your program
3968 can handle the signal, or else it may terminate if the signal is fatal
3969 and not handled. @code{pass} and @code{noignore} are synonyms.
3973 @value{GDBN} should not allow your program to see this signal.
3974 @code{nopass} and @code{ignore} are synonyms.
3978 When a signal stops your program, the signal is not visible to the
3980 continue. Your program sees the signal then, if @code{pass} is in
3981 effect for the signal in question @emph{at that time}. In other words,
3982 after @value{GDBN} reports a signal, you can use the @code{handle}
3983 command with @code{pass} or @code{nopass} to control whether your
3984 program sees that signal when you continue.
3986 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
3987 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
3988 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
3991 You can also use the @code{signal} command to prevent your program from
3992 seeing a signal, or cause it to see a signal it normally would not see,
3993 or to give it any signal at any time. For example, if your program stopped
3994 due to some sort of memory reference error, you might store correct
3995 values into the erroneous variables and continue, hoping to see more
3996 execution; but your program would probably terminate immediately as
3997 a result of the fatal signal once it saw the signal. To prevent this,
3998 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4002 @section Stopping and starting multi-thread programs
4004 When your program has multiple threads (@pxref{Threads,, Debugging
4005 programs with multiple threads}), you can choose whether to set
4006 breakpoints on all threads, or on a particular thread.
4009 @cindex breakpoints and threads
4010 @cindex thread breakpoints
4011 @kindex break @dots{} thread @var{threadno}
4012 @item break @var{linespec} thread @var{threadno}
4013 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4014 @var{linespec} specifies source lines; there are several ways of
4015 writing them, but the effect is always to specify some source line.
4017 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4018 to specify that you only want @value{GDBN} to stop the program when a
4019 particular thread reaches this breakpoint. @var{threadno} is one of the
4020 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4021 column of the @samp{info threads} display.
4023 If you do not specify @samp{thread @var{threadno}} when you set a
4024 breakpoint, the breakpoint applies to @emph{all} threads of your
4027 You can use the @code{thread} qualifier on conditional breakpoints as
4028 well; in this case, place @samp{thread @var{threadno}} before the
4029 breakpoint condition, like this:
4032 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4037 @cindex stopped threads
4038 @cindex threads, stopped
4039 Whenever your program stops under @value{GDBN} for any reason,
4040 @emph{all} threads of execution stop, not just the current thread. This
4041 allows you to examine the overall state of the program, including
4042 switching between threads, without worrying that things may change
4045 @cindex thread breakpoints and system calls
4046 @cindex system calls and thread breakpoints
4047 @cindex premature return from system calls
4048 There is an unfortunate side effect. If one thread stops for a
4049 breakpoint, or for some other reason, and another thread is blocked in a
4050 system call, then the system call may return prematurely. This is a
4051 consequence of the interaction between multiple threads and the signals
4052 that @value{GDBN} uses to implement breakpoints and other events that
4055 To handle this problem, your program should check the return value of
4056 each system call and react appropriately. This is good programming
4059 For example, do not write code like this:
4065 The call to @code{sleep} will return early if a different thread stops
4066 at a breakpoint or for some other reason.
4068 Instead, write this:
4073 unslept = sleep (unslept);
4076 A system call is allowed to return early, so the system is still
4077 conforming to its specification. But @value{GDBN} does cause your
4078 multi-threaded program to behave differently than it would without
4081 Also, @value{GDBN} uses internal breakpoints in the thread library to
4082 monitor certain events such as thread creation and thread destruction.
4083 When such an event happens, a system call in another thread may return
4084 prematurely, even though your program does not appear to stop.
4086 @cindex continuing threads
4087 @cindex threads, continuing
4088 Conversely, whenever you restart the program, @emph{all} threads start
4089 executing. @emph{This is true even when single-stepping} with commands
4090 like @code{step} or @code{next}.
4092 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4093 Since thread scheduling is up to your debugging target's operating
4094 system (not controlled by @value{GDBN}), other threads may
4095 execute more than one statement while the current thread completes a
4096 single step. Moreover, in general other threads stop in the middle of a
4097 statement, rather than at a clean statement boundary, when the program
4100 You might even find your program stopped in another thread after
4101 continuing or even single-stepping. This happens whenever some other
4102 thread runs into a breakpoint, a signal, or an exception before the
4103 first thread completes whatever you requested.
4105 On some OSes, you can lock the OS scheduler and thus allow only a single
4109 @item set scheduler-locking @var{mode}
4110 @cindex scheduler locking mode
4111 @cindex lock scheduler
4112 Set the scheduler locking mode. If it is @code{off}, then there is no
4113 locking and any thread may run at any time. If @code{on}, then only the
4114 current thread may run when the inferior is resumed. The @code{step}
4115 mode optimizes for single-stepping. It stops other threads from
4116 ``seizing the prompt'' by preempting the current thread while you are
4117 stepping. Other threads will only rarely (or never) get a chance to run
4118 when you step. They are more likely to run when you @samp{next} over a
4119 function call, and they are completely free to run when you use commands
4120 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4121 thread hits a breakpoint during its timeslice, they will never steal the
4122 @value{GDBN} prompt away from the thread that you are debugging.
4124 @item show scheduler-locking
4125 Display the current scheduler locking mode.
4130 @chapter Examining the Stack
4132 When your program has stopped, the first thing you need to know is where it
4133 stopped and how it got there.
4136 Each time your program performs a function call, information about the call
4138 That information includes the location of the call in your program,
4139 the arguments of the call,
4140 and the local variables of the function being called.
4141 The information is saved in a block of data called a @dfn{stack frame}.
4142 The stack frames are allocated in a region of memory called the @dfn{call
4145 When your program stops, the @value{GDBN} commands for examining the
4146 stack allow you to see all of this information.
4148 @cindex selected frame
4149 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4150 @value{GDBN} commands refer implicitly to the selected frame. In
4151 particular, whenever you ask @value{GDBN} for the value of a variable in
4152 your program, the value is found in the selected frame. There are
4153 special @value{GDBN} commands to select whichever frame you are
4154 interested in. @xref{Selection, ,Selecting a frame}.
4156 When your program stops, @value{GDBN} automatically selects the
4157 currently executing frame and describes it briefly, similar to the
4158 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
4161 * Frames:: Stack frames
4162 * Backtrace:: Backtraces
4163 * Selection:: Selecting a frame
4164 * Frame Info:: Information on a frame
4169 @section Stack frames
4171 @cindex frame, definition
4173 The call stack is divided up into contiguous pieces called @dfn{stack
4174 frames}, or @dfn{frames} for short; each frame is the data associated
4175 with one call to one function. The frame contains the arguments given
4176 to the function, the function's local variables, and the address at
4177 which the function is executing.
4179 @cindex initial frame
4180 @cindex outermost frame
4181 @cindex innermost frame
4182 When your program is started, the stack has only one frame, that of the
4183 function @code{main}. This is called the @dfn{initial} frame or the
4184 @dfn{outermost} frame. Each time a function is called, a new frame is
4185 made. Each time a function returns, the frame for that function invocation
4186 is eliminated. If a function is recursive, there can be many frames for
4187 the same function. The frame for the function in which execution is
4188 actually occurring is called the @dfn{innermost} frame. This is the most
4189 recently created of all the stack frames that still exist.
4191 @cindex frame pointer
4192 Inside your program, stack frames are identified by their addresses. A
4193 stack frame consists of many bytes, each of which has its own address; each
4194 kind of computer has a convention for choosing one byte whose
4195 address serves as the address of the frame. Usually this address is kept
4196 in a register called the @dfn{frame pointer register}
4197 (@pxref{Registers, $fp}) while execution is going on in that frame.
4199 @cindex frame number
4200 @value{GDBN} assigns numbers to all existing stack frames, starting with
4201 zero for the innermost frame, one for the frame that called it,
4202 and so on upward. These numbers do not really exist in your program;
4203 they are assigned by @value{GDBN} to give you a way of designating stack
4204 frames in @value{GDBN} commands.
4206 @c The -fomit-frame-pointer below perennially causes hbox overflow
4207 @c underflow problems.
4208 @cindex frameless execution
4209 Some compilers provide a way to compile functions so that they operate
4210 without stack frames. (For example, the @value{GCC} option
4212 @samp{-fomit-frame-pointer}
4214 generates functions without a frame.)
4215 This is occasionally done with heavily used library functions to save
4216 the frame setup time. @value{GDBN} has limited facilities for dealing
4217 with these function invocations. If the innermost function invocation
4218 has no stack frame, @value{GDBN} nevertheless regards it as though
4219 it had a separate frame, which is numbered zero as usual, allowing
4220 correct tracing of the function call chain. However, @value{GDBN} has
4221 no provision for frameless functions elsewhere in the stack.
4224 @kindex frame@r{, command}
4225 @cindex current stack frame
4226 @item frame @var{args}
4227 The @code{frame} command allows you to move from one stack frame to another,
4228 and to print the stack frame you select. @var{args} may be either the
4229 address of the frame or the stack frame number. Without an argument,
4230 @code{frame} prints the current stack frame.
4232 @kindex select-frame
4233 @cindex selecting frame silently
4235 The @code{select-frame} command allows you to move from one stack frame
4236 to another without printing the frame. This is the silent version of
4244 @cindex call stack traces
4245 A backtrace is a summary of how your program got where it is. It shows one
4246 line per frame, for many frames, starting with the currently executing
4247 frame (frame zero), followed by its caller (frame one), and on up the
4252 @kindex bt @r{(@code{backtrace})}
4255 Print a backtrace of the entire stack: one line per frame for all
4256 frames in the stack.
4258 You can stop the backtrace at any time by typing the system interrupt
4259 character, normally @kbd{C-c}.
4261 @item backtrace @var{n}
4263 Similar, but print only the innermost @var{n} frames.
4265 @item backtrace -@var{n}
4267 Similar, but print only the outermost @var{n} frames.
4269 @item backtrace full
4270 Print the values of the local variables also.
4276 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4277 are additional aliases for @code{backtrace}.
4279 Each line in the backtrace shows the frame number and the function name.
4280 The program counter value is also shown---unless you use @code{set
4281 print address off}. The backtrace also shows the source file name and
4282 line number, as well as the arguments to the function. The program
4283 counter value is omitted if it is at the beginning of the code for that
4286 Here is an example of a backtrace. It was made with the command
4287 @samp{bt 3}, so it shows the innermost three frames.
4291 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4293 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4294 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4296 (More stack frames follow...)
4301 The display for frame zero does not begin with a program counter
4302 value, indicating that your program has stopped at the beginning of the
4303 code for line @code{993} of @code{builtin.c}.
4305 @cindex value optimized out, in backtrace
4306 @cindex function call arguments, optimized out
4307 If your program was compiled with optimizations, some compilers will
4308 optimize away arguments passed to functions if those arguments are
4309 never used after the call. Such optimizations generate code that
4310 passes arguments through registers, but doesn't store those arguments
4311 in the stack frame. @value{GDBN} has no way of displaying such
4312 arguments in stack frames other than the innermost one. Here's what
4313 such a backtrace might look like:
4317 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4319 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
4320 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
4322 (More stack frames follow...)
4327 The values of arguments that were not saved in their stack frames are
4328 shown as @samp{<value optimized out>}.
4330 If you need to display the values of such optimized-out arguments,
4331 either deduce that from other variables whose values depend on the one
4332 you are interested in, or recompile without optimizations.
4334 @cindex backtrace beyond @code{main} function
4335 @cindex program entry point
4336 @cindex startup code, and backtrace
4337 Most programs have a standard user entry point---a place where system
4338 libraries and startup code transition into user code. For C this is
4339 @code{main}@footnote{
4340 Note that embedded programs (the so-called ``free-standing''
4341 environment) are not required to have a @code{main} function as the
4342 entry point. They could even have multiple entry points.}.
4343 When @value{GDBN} finds the entry function in a backtrace
4344 it will terminate the backtrace, to avoid tracing into highly
4345 system-specific (and generally uninteresting) code.
4347 If you need to examine the startup code, or limit the number of levels
4348 in a backtrace, you can change this behavior:
4351 @item set backtrace past-main
4352 @itemx set backtrace past-main on
4353 @kindex set backtrace
4354 Backtraces will continue past the user entry point.
4356 @item set backtrace past-main off
4357 Backtraces will stop when they encounter the user entry point. This is the
4360 @item show backtrace past-main
4361 @kindex show backtrace
4362 Display the current user entry point backtrace policy.
4364 @item set backtrace past-entry
4365 @itemx set backtrace past-entry on
4366 Backtraces will continue past the internal entry point of an application.
4367 This entry point is encoded by the linker when the application is built,
4368 and is likely before the user entry point @code{main} (or equivalent) is called.
4370 @item set backtrace past-entry off
4371 Backtraces will stop when they encouter the internal entry point of an
4372 application. This is the default.
4374 @item show backtrace past-entry
4375 Display the current internal entry point backtrace policy.
4377 @item set backtrace limit @var{n}
4378 @itemx set backtrace limit 0
4379 @cindex backtrace limit
4380 Limit the backtrace to @var{n} levels. A value of zero means
4383 @item show backtrace limit
4384 Display the current limit on backtrace levels.
4388 @section Selecting a frame
4390 Most commands for examining the stack and other data in your program work on
4391 whichever stack frame is selected at the moment. Here are the commands for
4392 selecting a stack frame; all of them finish by printing a brief description
4393 of the stack frame just selected.
4396 @kindex frame@r{, selecting}
4397 @kindex f @r{(@code{frame})}
4400 Select frame number @var{n}. Recall that frame zero is the innermost
4401 (currently executing) frame, frame one is the frame that called the
4402 innermost one, and so on. The highest-numbered frame is the one for
4405 @item frame @var{addr}
4407 Select the frame at address @var{addr}. This is useful mainly if the
4408 chaining of stack frames has been damaged by a bug, making it
4409 impossible for @value{GDBN} to assign numbers properly to all frames. In
4410 addition, this can be useful when your program has multiple stacks and
4411 switches between them.
4413 On the SPARC architecture, @code{frame} needs two addresses to
4414 select an arbitrary frame: a frame pointer and a stack pointer.
4416 On the MIPS and Alpha architecture, it needs two addresses: a stack
4417 pointer and a program counter.
4419 On the 29k architecture, it needs three addresses: a register stack
4420 pointer, a program counter, and a memory stack pointer.
4424 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4425 advances toward the outermost frame, to higher frame numbers, to frames
4426 that have existed longer. @var{n} defaults to one.
4429 @kindex do @r{(@code{down})}
4431 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4432 advances toward the innermost frame, to lower frame numbers, to frames
4433 that were created more recently. @var{n} defaults to one. You may
4434 abbreviate @code{down} as @code{do}.
4437 All of these commands end by printing two lines of output describing the
4438 frame. The first line shows the frame number, the function name, the
4439 arguments, and the source file and line number of execution in that
4440 frame. The second line shows the text of that source line.
4448 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4450 10 read_input_file (argv[i]);
4454 After such a printout, the @code{list} command with no arguments
4455 prints ten lines centered on the point of execution in the frame.
4456 You can also edit the program at the point of execution with your favorite
4457 editing program by typing @code{edit}.
4458 @xref{List, ,Printing source lines},
4462 @kindex down-silently
4464 @item up-silently @var{n}
4465 @itemx down-silently @var{n}
4466 These two commands are variants of @code{up} and @code{down},
4467 respectively; they differ in that they do their work silently, without
4468 causing display of the new frame. They are intended primarily for use
4469 in @value{GDBN} command scripts, where the output might be unnecessary and
4474 @section Information about a frame
4476 There are several other commands to print information about the selected
4482 When used without any argument, this command does not change which
4483 frame is selected, but prints a brief description of the currently
4484 selected stack frame. It can be abbreviated @code{f}. With an
4485 argument, this command is used to select a stack frame.
4486 @xref{Selection, ,Selecting a frame}.
4489 @kindex info f @r{(@code{info frame})}
4492 This command prints a verbose description of the selected stack frame,
4497 the address of the frame
4499 the address of the next frame down (called by this frame)
4501 the address of the next frame up (caller of this frame)
4503 the language in which the source code corresponding to this frame is written
4505 the address of the frame's arguments
4507 the address of the frame's local variables
4509 the program counter saved in it (the address of execution in the caller frame)
4511 which registers were saved in the frame
4514 @noindent The verbose description is useful when
4515 something has gone wrong that has made the stack format fail to fit
4516 the usual conventions.
4518 @item info frame @var{addr}
4519 @itemx info f @var{addr}
4520 Print a verbose description of the frame at address @var{addr}, without
4521 selecting that frame. The selected frame remains unchanged by this
4522 command. This requires the same kind of address (more than one for some
4523 architectures) that you specify in the @code{frame} command.
4524 @xref{Selection, ,Selecting a frame}.
4528 Print the arguments of the selected frame, each on a separate line.
4532 Print the local variables of the selected frame, each on a separate
4533 line. These are all variables (declared either static or automatic)
4534 accessible at the point of execution of the selected frame.
4537 @cindex catch exceptions, list active handlers
4538 @cindex exception handlers, how to list
4540 Print a list of all the exception handlers that are active in the
4541 current stack frame at the current point of execution. To see other
4542 exception handlers, visit the associated frame (using the @code{up},
4543 @code{down}, or @code{frame} commands); then type @code{info catch}.
4544 @xref{Set Catchpoints, , Setting catchpoints}.
4550 @chapter Examining Source Files
4552 @value{GDBN} can print parts of your program's source, since the debugging
4553 information recorded in the program tells @value{GDBN} what source files were
4554 used to build it. When your program stops, @value{GDBN} spontaneously prints
4555 the line where it stopped. Likewise, when you select a stack frame
4556 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4557 execution in that frame has stopped. You can print other portions of
4558 source files by explicit command.
4560 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4561 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4562 @value{GDBN} under @sc{gnu} Emacs}.
4565 * List:: Printing source lines
4566 * Edit:: Editing source files
4567 * Search:: Searching source files
4568 * Source Path:: Specifying source directories
4569 * Machine Code:: Source and machine code
4573 @section Printing source lines
4576 @kindex l @r{(@code{list})}
4577 To print lines from a source file, use the @code{list} command
4578 (abbreviated @code{l}). By default, ten lines are printed.
4579 There are several ways to specify what part of the file you want to print.
4581 Here are the forms of the @code{list} command most commonly used:
4584 @item list @var{linenum}
4585 Print lines centered around line number @var{linenum} in the
4586 current source file.
4588 @item list @var{function}
4589 Print lines centered around the beginning of function
4593 Print more lines. If the last lines printed were printed with a
4594 @code{list} command, this prints lines following the last lines
4595 printed; however, if the last line printed was a solitary line printed
4596 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4597 Stack}), this prints lines centered around that line.
4600 Print lines just before the lines last printed.
4603 @cindex @code{list}, how many lines to display
4604 By default, @value{GDBN} prints ten source lines with any of these forms of
4605 the @code{list} command. You can change this using @code{set listsize}:
4608 @kindex set listsize
4609 @item set listsize @var{count}
4610 Make the @code{list} command display @var{count} source lines (unless
4611 the @code{list} argument explicitly specifies some other number).
4613 @kindex show listsize
4615 Display the number of lines that @code{list} prints.
4618 Repeating a @code{list} command with @key{RET} discards the argument,
4619 so it is equivalent to typing just @code{list}. This is more useful
4620 than listing the same lines again. An exception is made for an
4621 argument of @samp{-}; that argument is preserved in repetition so that
4622 each repetition moves up in the source file.
4625 In general, the @code{list} command expects you to supply zero, one or two
4626 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4627 of writing them, but the effect is always to specify some source line.
4628 Here is a complete description of the possible arguments for @code{list}:
4631 @item list @var{linespec}
4632 Print lines centered around the line specified by @var{linespec}.
4634 @item list @var{first},@var{last}
4635 Print lines from @var{first} to @var{last}. Both arguments are
4638 @item list ,@var{last}
4639 Print lines ending with @var{last}.
4641 @item list @var{first},
4642 Print lines starting with @var{first}.
4645 Print lines just after the lines last printed.
4648 Print lines just before the lines last printed.
4651 As described in the preceding table.
4654 Here are the ways of specifying a single source line---all the
4659 Specifies line @var{number} of the current source file.
4660 When a @code{list} command has two linespecs, this refers to
4661 the same source file as the first linespec.
4664 Specifies the line @var{offset} lines after the last line printed.
4665 When used as the second linespec in a @code{list} command that has
4666 two, this specifies the line @var{offset} lines down from the
4670 Specifies the line @var{offset} lines before the last line printed.
4672 @item @var{filename}:@var{number}
4673 Specifies line @var{number} in the source file @var{filename}.
4675 @item @var{function}
4676 Specifies the line that begins the body of the function @var{function}.
4677 For example: in C, this is the line with the open brace.
4679 @item @var{filename}:@var{function}
4680 Specifies the line of the open-brace that begins the body of the
4681 function @var{function} in the file @var{filename}. You only need the
4682 file name with a function name to avoid ambiguity when there are
4683 identically named functions in different source files.
4685 @item *@var{address}
4686 Specifies the line containing the program address @var{address}.
4687 @var{address} may be any expression.
4691 @section Editing source files
4692 @cindex editing source files
4695 @kindex e @r{(@code{edit})}
4696 To edit the lines in a source file, use the @code{edit} command.
4697 The editing program of your choice
4698 is invoked with the current line set to
4699 the active line in the program.
4700 Alternatively, there are several ways to specify what part of the file you
4701 want to print if you want to see other parts of the program.
4703 Here are the forms of the @code{edit} command most commonly used:
4707 Edit the current source file at the active line number in the program.
4709 @item edit @var{number}
4710 Edit the current source file with @var{number} as the active line number.
4712 @item edit @var{function}
4713 Edit the file containing @var{function} at the beginning of its definition.
4715 @item edit @var{filename}:@var{number}
4716 Specifies line @var{number} in the source file @var{filename}.
4718 @item edit @var{filename}:@var{function}
4719 Specifies the line that begins the body of the
4720 function @var{function} in the file @var{filename}. You only need the
4721 file name with a function name to avoid ambiguity when there are
4722 identically named functions in different source files.
4724 @item edit *@var{address}
4725 Specifies the line containing the program address @var{address}.
4726 @var{address} may be any expression.
4729 @subsection Choosing your editor
4730 You can customize @value{GDBN} to use any editor you want
4732 The only restriction is that your editor (say @code{ex}), recognizes the
4733 following command-line syntax:
4735 ex +@var{number} file
4737 The optional numeric value +@var{number} specifies the number of the line in
4738 the file where to start editing.}.
4739 By default, it is @file{@value{EDITOR}}, but you can change this
4740 by setting the environment variable @code{EDITOR} before using
4741 @value{GDBN}. For example, to configure @value{GDBN} to use the
4742 @code{vi} editor, you could use these commands with the @code{sh} shell:
4748 or in the @code{csh} shell,
4750 setenv EDITOR /usr/bin/vi
4755 @section Searching source files
4756 @cindex searching source files
4758 There are two commands for searching through the current source file for a
4763 @kindex forward-search
4764 @item forward-search @var{regexp}
4765 @itemx search @var{regexp}
4766 The command @samp{forward-search @var{regexp}} checks each line,
4767 starting with the one following the last line listed, for a match for
4768 @var{regexp}. It lists the line that is found. You can use the
4769 synonym @samp{search @var{regexp}} or abbreviate the command name as
4772 @kindex reverse-search
4773 @item reverse-search @var{regexp}
4774 The command @samp{reverse-search @var{regexp}} checks each line, starting
4775 with the one before the last line listed and going backward, for a match
4776 for @var{regexp}. It lists the line that is found. You can abbreviate
4777 this command as @code{rev}.
4781 @section Specifying source directories
4784 @cindex directories for source files
4785 Executable programs sometimes do not record the directories of the source
4786 files from which they were compiled, just the names. Even when they do,
4787 the directories could be moved between the compilation and your debugging
4788 session. @value{GDBN} has a list of directories to search for source files;
4789 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
4790 it tries all the directories in the list, in the order they are present
4791 in the list, until it finds a file with the desired name.
4793 For example, suppose an executable references the file
4794 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
4795 @file{/mnt/cross}. The file is first looked up literally; if this
4796 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
4797 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
4798 message is printed. @value{GDBN} does not look up the parts of the
4799 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
4800 Likewise, the subdirectories of the source path are not searched: if
4801 the source path is @file{/mnt/cross}, and the binary refers to
4802 @file{foo.c}, @value{GDBN} would not find it under
4803 @file{/mnt/cross/usr/src/foo-1.0/lib}.
4805 Plain file names, relative file names with leading directories, file
4806 names containing dots, etc.@: are all treated as described above; for
4807 instance, if the source path is @file{/mnt/cross}, and the source file
4808 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
4809 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
4810 that---@file{/mnt/cross/foo.c}.
4812 Note that the executable search path is @emph{not} used to locate the
4813 source files. Neither is the current working directory, unless it
4814 happens to be in the source path.
4816 Whenever you reset or rearrange the source path, @value{GDBN} clears out
4817 any information it has cached about where source files are found and where
4818 each line is in the file.
4822 When you start @value{GDBN}, its source path includes only @samp{cdir}
4823 and @samp{cwd}, in that order.
4824 To add other directories, use the @code{directory} command.
4827 @item directory @var{dirname} @dots{}
4828 @item dir @var{dirname} @dots{}
4829 Add directory @var{dirname} to the front of the source path. Several
4830 directory names may be given to this command, separated by @samp{:}
4831 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
4832 part of absolute file names) or
4833 whitespace. You may specify a directory that is already in the source
4834 path; this moves it forward, so @value{GDBN} searches it sooner.
4838 @vindex $cdir@r{, convenience variable}
4839 @vindex $cwdr@r{, convenience variable}
4840 @cindex compilation directory
4841 @cindex current directory
4842 @cindex working directory
4843 @cindex directory, current
4844 @cindex directory, compilation
4845 You can use the string @samp{$cdir} to refer to the compilation
4846 directory (if one is recorded), and @samp{$cwd} to refer to the current
4847 working directory. @samp{$cwd} is not the same as @samp{.}---the former
4848 tracks the current working directory as it changes during your @value{GDBN}
4849 session, while the latter is immediately expanded to the current
4850 directory at the time you add an entry to the source path.
4853 Reset the source path to empty again. This requires confirmation.
4855 @c RET-repeat for @code{directory} is explicitly disabled, but since
4856 @c repeating it would be a no-op we do not say that. (thanks to RMS)
4858 @item show directories
4859 @kindex show directories
4860 Print the source path: show which directories it contains.
4863 If your source path is cluttered with directories that are no longer of
4864 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
4865 versions of source. You can correct the situation as follows:
4869 Use @code{directory} with no argument to reset the source path to empty.
4872 Use @code{directory} with suitable arguments to reinstall the
4873 directories you want in the source path. You can add all the
4874 directories in one command.
4878 @section Source and machine code
4879 @cindex source line and its code address
4881 You can use the command @code{info line} to map source lines to program
4882 addresses (and vice versa), and the command @code{disassemble} to display
4883 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
4884 mode, the @code{info line} command causes the arrow to point to the
4885 line specified. Also, @code{info line} prints addresses in symbolic form as
4890 @item info line @var{linespec}
4891 Print the starting and ending addresses of the compiled code for
4892 source line @var{linespec}. You can specify source lines in any of
4893 the ways understood by the @code{list} command (@pxref{List, ,Printing
4897 For example, we can use @code{info line} to discover the location of
4898 the object code for the first line of function
4899 @code{m4_changequote}:
4901 @c FIXME: I think this example should also show the addresses in
4902 @c symbolic form, as they usually would be displayed.
4904 (@value{GDBP}) info line m4_changequote
4905 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
4909 @cindex code address and its source line
4910 We can also inquire (using @code{*@var{addr}} as the form for
4911 @var{linespec}) what source line covers a particular address:
4913 (@value{GDBP}) info line *0x63ff
4914 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
4917 @cindex @code{$_} and @code{info line}
4918 @cindex @code{x} command, default address
4919 @kindex x@r{(examine), and} info line
4920 After @code{info line}, the default address for the @code{x} command
4921 is changed to the starting address of the line, so that @samp{x/i} is
4922 sufficient to begin examining the machine code (@pxref{Memory,
4923 ,Examining memory}). Also, this address is saved as the value of the
4924 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
4929 @cindex assembly instructions
4930 @cindex instructions, assembly
4931 @cindex machine instructions
4932 @cindex listing machine instructions
4934 This specialized command dumps a range of memory as machine
4935 instructions. The default memory range is the function surrounding the
4936 program counter of the selected frame. A single argument to this
4937 command is a program counter value; @value{GDBN} dumps the function
4938 surrounding this value. Two arguments specify a range of addresses
4939 (first inclusive, second exclusive) to dump.
4942 The following example shows the disassembly of a range of addresses of
4943 HP PA-RISC 2.0 code:
4946 (@value{GDBP}) disas 0x32c4 0x32e4
4947 Dump of assembler code from 0x32c4 to 0x32e4:
4948 0x32c4 <main+204>: addil 0,dp
4949 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
4950 0x32cc <main+212>: ldil 0x3000,r31
4951 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
4952 0x32d4 <main+220>: ldo 0(r31),rp
4953 0x32d8 <main+224>: addil -0x800,dp
4954 0x32dc <main+228>: ldo 0x588(r1),r26
4955 0x32e0 <main+232>: ldil 0x3000,r31
4956 End of assembler dump.
4959 Some architectures have more than one commonly-used set of instruction
4960 mnemonics or other syntax.
4962 For programs that were dynamically linked and use shared libraries,
4963 instructions that call functions or branch to locations in the shared
4964 libraries might show a seemingly bogus location---it's actually a
4965 location of the relocation table. On some architectures, @value{GDBN}
4966 might be able to resolve these to actual function names.
4969 @kindex set disassembly-flavor
4970 @cindex Intel disassembly flavor
4971 @cindex AT&T disassembly flavor
4972 @item set disassembly-flavor @var{instruction-set}
4973 Select the instruction set to use when disassembling the
4974 program via the @code{disassemble} or @code{x/i} commands.
4976 Currently this command is only defined for the Intel x86 family. You
4977 can set @var{instruction-set} to either @code{intel} or @code{att}.
4978 The default is @code{att}, the AT&T flavor used by default by Unix
4979 assemblers for x86-based targets.
4981 @kindex show disassembly-flavor
4982 @item show disassembly-flavor
4983 Show the current setting of the disassembly flavor.
4988 @chapter Examining Data
4990 @cindex printing data
4991 @cindex examining data
4994 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
4995 @c document because it is nonstandard... Under Epoch it displays in a
4996 @c different window or something like that.
4997 The usual way to examine data in your program is with the @code{print}
4998 command (abbreviated @code{p}), or its synonym @code{inspect}. It
4999 evaluates and prints the value of an expression of the language your
5000 program is written in (@pxref{Languages, ,Using @value{GDBN} with
5001 Different Languages}).
5004 @item print @var{expr}
5005 @itemx print /@var{f} @var{expr}
5006 @var{expr} is an expression (in the source language). By default the
5007 value of @var{expr} is printed in a format appropriate to its data type;
5008 you can choose a different format by specifying @samp{/@var{f}}, where
5009 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
5013 @itemx print /@var{f}
5014 @cindex reprint the last value
5015 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
5016 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
5017 conveniently inspect the same value in an alternative format.
5020 A more low-level way of examining data is with the @code{x} command.
5021 It examines data in memory at a specified address and prints it in a
5022 specified format. @xref{Memory, ,Examining memory}.
5024 If you are interested in information about types, or about how the
5025 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
5026 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
5030 * Expressions:: Expressions
5031 * Variables:: Program variables
5032 * Arrays:: Artificial arrays
5033 * Output Formats:: Output formats
5034 * Memory:: Examining memory
5035 * Auto Display:: Automatic display
5036 * Print Settings:: Print settings
5037 * Value History:: Value history
5038 * Convenience Vars:: Convenience variables
5039 * Registers:: Registers
5040 * Floating Point Hardware:: Floating point hardware
5041 * Vector Unit:: Vector Unit
5042 * OS Information:: Auxiliary data provided by operating system
5043 * Memory Region Attributes:: Memory region attributes
5044 * Dump/Restore Files:: Copy between memory and a file
5045 * Core File Generation:: Cause a program dump its core
5046 * Character Sets:: Debugging programs that use a different
5047 character set than GDB does
5048 * Caching Remote Data:: Data caching for remote targets
5052 @section Expressions
5055 @code{print} and many other @value{GDBN} commands accept an expression and
5056 compute its value. Any kind of constant, variable or operator defined
5057 by the programming language you are using is valid in an expression in
5058 @value{GDBN}. This includes conditional expressions, function calls,
5059 casts, and string constants. It also includes preprocessor macros, if
5060 you compiled your program to include this information; see
5063 @cindex arrays in expressions
5064 @value{GDBN} supports array constants in expressions input by
5065 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
5066 you can use the command @code{print @{1, 2, 3@}} to build up an array in
5067 memory that is @code{malloc}ed in the target program.
5069 Because C is so widespread, most of the expressions shown in examples in
5070 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
5071 Languages}, for information on how to use expressions in other
5074 In this section, we discuss operators that you can use in @value{GDBN}
5075 expressions regardless of your programming language.
5077 @cindex casts, in expressions
5078 Casts are supported in all languages, not just in C, because it is so
5079 useful to cast a number into a pointer in order to examine a structure
5080 at that address in memory.
5081 @c FIXME: casts supported---Mod2 true?
5083 @value{GDBN} supports these operators, in addition to those common
5084 to programming languages:
5088 @samp{@@} is a binary operator for treating parts of memory as arrays.
5089 @xref{Arrays, ,Artificial arrays}, for more information.
5092 @samp{::} allows you to specify a variable in terms of the file or
5093 function where it is defined. @xref{Variables, ,Program variables}.
5095 @cindex @{@var{type}@}
5096 @cindex type casting memory
5097 @cindex memory, viewing as typed object
5098 @cindex casts, to view memory
5099 @item @{@var{type}@} @var{addr}
5100 Refers to an object of type @var{type} stored at address @var{addr} in
5101 memory. @var{addr} may be any expression whose value is an integer or
5102 pointer (but parentheses are required around binary operators, just as in
5103 a cast). This construct is allowed regardless of what kind of data is
5104 normally supposed to reside at @var{addr}.
5108 @section Program variables
5110 The most common kind of expression to use is the name of a variable
5113 Variables in expressions are understood in the selected stack frame
5114 (@pxref{Selection, ,Selecting a frame}); they must be either:
5118 global (or file-static)
5125 visible according to the scope rules of the
5126 programming language from the point of execution in that frame
5129 @noindent This means that in the function
5144 you can examine and use the variable @code{a} whenever your program is
5145 executing within the function @code{foo}, but you can only use or
5146 examine the variable @code{b} while your program is executing inside
5147 the block where @code{b} is declared.
5149 @cindex variable name conflict
5150 There is an exception: you can refer to a variable or function whose
5151 scope is a single source file even if the current execution point is not
5152 in this file. But it is possible to have more than one such variable or
5153 function with the same name (in different source files). If that
5154 happens, referring to that name has unpredictable effects. If you wish,
5155 you can specify a static variable in a particular function or file,
5156 using the colon-colon (@code{::}) notation:
5158 @cindex colon-colon, context for variables/functions
5160 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
5161 @cindex @code{::}, context for variables/functions
5164 @var{file}::@var{variable}
5165 @var{function}::@var{variable}
5169 Here @var{file} or @var{function} is the name of the context for the
5170 static @var{variable}. In the case of file names, you can use quotes to
5171 make sure @value{GDBN} parses the file name as a single word---for example,
5172 to print a global value of @code{x} defined in @file{f2.c}:
5175 (@value{GDBP}) p 'f2.c'::x
5178 @cindex C@t{++} scope resolution
5179 This use of @samp{::} is very rarely in conflict with the very similar
5180 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
5181 scope resolution operator in @value{GDBN} expressions.
5182 @c FIXME: Um, so what happens in one of those rare cases where it's in
5185 @cindex wrong values
5186 @cindex variable values, wrong
5187 @cindex function entry/exit, wrong values of variables
5188 @cindex optimized code, wrong values of variables
5190 @emph{Warning:} Occasionally, a local variable may appear to have the
5191 wrong value at certain points in a function---just after entry to a new
5192 scope, and just before exit.
5194 You may see this problem when you are stepping by machine instructions.
5195 This is because, on most machines, it takes more than one instruction to
5196 set up a stack frame (including local variable definitions); if you are
5197 stepping by machine instructions, variables may appear to have the wrong
5198 values until the stack frame is completely built. On exit, it usually
5199 also takes more than one machine instruction to destroy a stack frame;
5200 after you begin stepping through that group of instructions, local
5201 variable definitions may be gone.
5203 This may also happen when the compiler does significant optimizations.
5204 To be sure of always seeing accurate values, turn off all optimization
5207 @cindex ``No symbol "foo" in current context''
5208 Another possible effect of compiler optimizations is to optimize
5209 unused variables out of existence, or assign variables to registers (as
5210 opposed to memory addresses). Depending on the support for such cases
5211 offered by the debug info format used by the compiler, @value{GDBN}
5212 might not be able to display values for such local variables. If that
5213 happens, @value{GDBN} will print a message like this:
5216 No symbol "foo" in current context.
5219 To solve such problems, either recompile without optimizations, or use a
5220 different debug info format, if the compiler supports several such
5221 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5222 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5223 produces debug info in a format that is superior to formats such as
5224 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5225 an effective form for debug info. @xref{Debugging Options,,Options
5226 for Debugging Your Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}.
5227 @xref{C, , Debugging C++}, for more info about debug info formats
5228 that are best suited to C@t{++} programs.
5230 If you ask to print an object whose contents are unknown to
5231 @value{GDBN}, e.g., because its data type is not completely specified
5232 by the debug information, @value{GDBN} will say @samp{<incomplete
5233 type>}. @xref{Symbols, incomplete type}, for more about this.
5236 @section Artificial arrays
5238 @cindex artificial array
5240 @kindex @@@r{, referencing memory as an array}
5241 It is often useful to print out several successive objects of the
5242 same type in memory; a section of an array, or an array of
5243 dynamically determined size for which only a pointer exists in the
5246 You can do this by referring to a contiguous span of memory as an
5247 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5248 operand of @samp{@@} should be the first element of the desired array
5249 and be an individual object. The right operand should be the desired length
5250 of the array. The result is an array value whose elements are all of
5251 the type of the left argument. The first element is actually the left
5252 argument; the second element comes from bytes of memory immediately
5253 following those that hold the first element, and so on. Here is an
5254 example. If a program says
5257 int *array = (int *) malloc (len * sizeof (int));
5261 you can print the contents of @code{array} with
5267 The left operand of @samp{@@} must reside in memory. Array values made
5268 with @samp{@@} in this way behave just like other arrays in terms of
5269 subscripting, and are coerced to pointers when used in expressions.
5270 Artificial arrays most often appear in expressions via the value history
5271 (@pxref{Value History, ,Value history}), after printing one out.
5273 Another way to create an artificial array is to use a cast.
5274 This re-interprets a value as if it were an array.
5275 The value need not be in memory:
5277 (@value{GDBP}) p/x (short[2])0x12345678
5278 $1 = @{0x1234, 0x5678@}
5281 As a convenience, if you leave the array length out (as in
5282 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5283 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5285 (@value{GDBP}) p/x (short[])0x12345678
5286 $2 = @{0x1234, 0x5678@}
5289 Sometimes the artificial array mechanism is not quite enough; in
5290 moderately complex data structures, the elements of interest may not
5291 actually be adjacent---for example, if you are interested in the values
5292 of pointers in an array. One useful work-around in this situation is
5293 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5294 variables}) as a counter in an expression that prints the first
5295 interesting value, and then repeat that expression via @key{RET}. For
5296 instance, suppose you have an array @code{dtab} of pointers to
5297 structures, and you are interested in the values of a field @code{fv}
5298 in each structure. Here is an example of what you might type:
5308 @node Output Formats
5309 @section Output formats
5311 @cindex formatted output
5312 @cindex output formats
5313 By default, @value{GDBN} prints a value according to its data type. Sometimes
5314 this is not what you want. For example, you might want to print a number
5315 in hex, or a pointer in decimal. Or you might want to view data in memory
5316 at a certain address as a character string or as an instruction. To do
5317 these things, specify an @dfn{output format} when you print a value.
5319 The simplest use of output formats is to say how to print a value
5320 already computed. This is done by starting the arguments of the
5321 @code{print} command with a slash and a format letter. The format
5322 letters supported are:
5326 Regard the bits of the value as an integer, and print the integer in
5330 Print as integer in signed decimal.
5333 Print as integer in unsigned decimal.
5336 Print as integer in octal.
5339 Print as integer in binary. The letter @samp{t} stands for ``two''.
5340 @footnote{@samp{b} cannot be used because these format letters are also
5341 used with the @code{x} command, where @samp{b} stands for ``byte'';
5342 see @ref{Memory,,Examining memory}.}
5345 @cindex unknown address, locating
5346 @cindex locate address
5347 Print as an address, both absolute in hexadecimal and as an offset from
5348 the nearest preceding symbol. You can use this format used to discover
5349 where (in what function) an unknown address is located:
5352 (@value{GDBP}) p/a 0x54320
5353 $3 = 0x54320 <_initialize_vx+396>
5357 The command @code{info symbol 0x54320} yields similar results.
5358 @xref{Symbols, info symbol}.
5361 Regard as an integer and print it as a character constant. This
5362 prints both the numerical value and its character representation. The
5363 character representation is replaced with the octal escape @samp{\nnn}
5364 for characters outside the 7-bit @sc{ascii} range.
5367 Regard the bits of the value as a floating point number and print
5368 using typical floating point syntax.
5371 For example, to print the program counter in hex (@pxref{Registers}), type
5378 Note that no space is required before the slash; this is because command
5379 names in @value{GDBN} cannot contain a slash.
5381 To reprint the last value in the value history with a different format,
5382 you can use the @code{print} command with just a format and no
5383 expression. For example, @samp{p/x} reprints the last value in hex.
5386 @section Examining memory
5388 You can use the command @code{x} (for ``examine'') to examine memory in
5389 any of several formats, independently of your program's data types.
5391 @cindex examining memory
5393 @kindex x @r{(examine memory)}
5394 @item x/@var{nfu} @var{addr}
5397 Use the @code{x} command to examine memory.
5400 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5401 much memory to display and how to format it; @var{addr} is an
5402 expression giving the address where you want to start displaying memory.
5403 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5404 Several commands set convenient defaults for @var{addr}.
5407 @item @var{n}, the repeat count
5408 The repeat count is a decimal integer; the default is 1. It specifies
5409 how much memory (counting by units @var{u}) to display.
5410 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5413 @item @var{f}, the display format
5414 The display format is one of the formats used by @code{print}
5415 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
5416 @samp{f}), and in addition @samp{s} (for null-terminated strings) and
5417 @samp{i} (for machine instructions). The default is @samp{x}
5418 (hexadecimal) initially. The default changes each time you use either
5419 @code{x} or @code{print}.
5421 @item @var{u}, the unit size
5422 The unit size is any of
5428 Halfwords (two bytes).
5430 Words (four bytes). This is the initial default.
5432 Giant words (eight bytes).
5435 Each time you specify a unit size with @code{x}, that size becomes the
5436 default unit the next time you use @code{x}. (For the @samp{s} and
5437 @samp{i} formats, the unit size is ignored and is normally not written.)
5439 @item @var{addr}, starting display address
5440 @var{addr} is the address where you want @value{GDBN} to begin displaying
5441 memory. The expression need not have a pointer value (though it may);
5442 it is always interpreted as an integer address of a byte of memory.
5443 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5444 @var{addr} is usually just after the last address examined---but several
5445 other commands also set the default address: @code{info breakpoints} (to
5446 the address of the last breakpoint listed), @code{info line} (to the
5447 starting address of a line), and @code{print} (if you use it to display
5448 a value from memory).
5451 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5452 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5453 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5454 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5455 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5457 Since the letters indicating unit sizes are all distinct from the
5458 letters specifying output formats, you do not have to remember whether
5459 unit size or format comes first; either order works. The output
5460 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5461 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5463 Even though the unit size @var{u} is ignored for the formats @samp{s}
5464 and @samp{i}, you might still want to use a count @var{n}; for example,
5465 @samp{3i} specifies that you want to see three machine instructions,
5466 including any operands. The command @code{disassemble} gives an
5467 alternative way of inspecting machine instructions; see @ref{Machine
5468 Code,,Source and machine code}.
5470 All the defaults for the arguments to @code{x} are designed to make it
5471 easy to continue scanning memory with minimal specifications each time
5472 you use @code{x}. For example, after you have inspected three machine
5473 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5474 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5475 the repeat count @var{n} is used again; the other arguments default as
5476 for successive uses of @code{x}.
5478 @cindex @code{$_}, @code{$__}, and value history
5479 The addresses and contents printed by the @code{x} command are not saved
5480 in the value history because there is often too much of them and they
5481 would get in the way. Instead, @value{GDBN} makes these values available for
5482 subsequent use in expressions as values of the convenience variables
5483 @code{$_} and @code{$__}. After an @code{x} command, the last address
5484 examined is available for use in expressions in the convenience variable
5485 @code{$_}. The contents of that address, as examined, are available in
5486 the convenience variable @code{$__}.
5488 If the @code{x} command has a repeat count, the address and contents saved
5489 are from the last memory unit printed; this is not the same as the last
5490 address printed if several units were printed on the last line of output.
5492 @cindex remote memory comparison
5493 @cindex verify remote memory image
5494 When you are debugging a program running on a remote target machine
5495 (@pxref{Remote}), you may wish to verify the program's image in the
5496 remote machine's memory against the executable file you downloaded to
5497 the target. The @code{compare-sections} command is provided for such
5501 @kindex compare-sections
5502 @item compare-sections @r{[}@var{section-name}@r{]}
5503 Compare the data of a loadable section @var{section-name} in the
5504 executable file of the program being debugged with the same section in
5505 the remote machine's memory, and report any mismatches. With no
5506 arguments, compares all loadable sections. This command's
5507 availability depends on the target's support for the @code{"qCRC"}
5512 @section Automatic display
5513 @cindex automatic display
5514 @cindex display of expressions
5516 If you find that you want to print the value of an expression frequently
5517 (to see how it changes), you might want to add it to the @dfn{automatic
5518 display list} so that @value{GDBN} prints its value each time your program stops.
5519 Each expression added to the list is given a number to identify it;
5520 to remove an expression from the list, you specify that number.
5521 The automatic display looks like this:
5525 3: bar[5] = (struct hack *) 0x3804
5529 This display shows item numbers, expressions and their current values. As with
5530 displays you request manually using @code{x} or @code{print}, you can
5531 specify the output format you prefer; in fact, @code{display} decides
5532 whether to use @code{print} or @code{x} depending on how elaborate your
5533 format specification is---it uses @code{x} if you specify a unit size,
5534 or one of the two formats (@samp{i} and @samp{s}) that are only
5535 supported by @code{x}; otherwise it uses @code{print}.
5539 @item display @var{expr}
5540 Add the expression @var{expr} to the list of expressions to display
5541 each time your program stops. @xref{Expressions, ,Expressions}.
5543 @code{display} does not repeat if you press @key{RET} again after using it.
5545 @item display/@var{fmt} @var{expr}
5546 For @var{fmt} specifying only a display format and not a size or
5547 count, add the expression @var{expr} to the auto-display list but
5548 arrange to display it each time in the specified format @var{fmt}.
5549 @xref{Output Formats,,Output formats}.
5551 @item display/@var{fmt} @var{addr}
5552 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5553 number of units, add the expression @var{addr} as a memory address to
5554 be examined each time your program stops. Examining means in effect
5555 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5558 For example, @samp{display/i $pc} can be helpful, to see the machine
5559 instruction about to be executed each time execution stops (@samp{$pc}
5560 is a common name for the program counter; @pxref{Registers, ,Registers}).
5563 @kindex delete display
5565 @item undisplay @var{dnums}@dots{}
5566 @itemx delete display @var{dnums}@dots{}
5567 Remove item numbers @var{dnums} from the list of expressions to display.
5569 @code{undisplay} does not repeat if you press @key{RET} after using it.
5570 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5572 @kindex disable display
5573 @item disable display @var{dnums}@dots{}
5574 Disable the display of item numbers @var{dnums}. A disabled display
5575 item is not printed automatically, but is not forgotten. It may be
5576 enabled again later.
5578 @kindex enable display
5579 @item enable display @var{dnums}@dots{}
5580 Enable display of item numbers @var{dnums}. It becomes effective once
5581 again in auto display of its expression, until you specify otherwise.
5584 Display the current values of the expressions on the list, just as is
5585 done when your program stops.
5587 @kindex info display
5589 Print the list of expressions previously set up to display
5590 automatically, each one with its item number, but without showing the
5591 values. This includes disabled expressions, which are marked as such.
5592 It also includes expressions which would not be displayed right now
5593 because they refer to automatic variables not currently available.
5596 @cindex display disabled out of scope
5597 If a display expression refers to local variables, then it does not make
5598 sense outside the lexical context for which it was set up. Such an
5599 expression is disabled when execution enters a context where one of its
5600 variables is not defined. For example, if you give the command
5601 @code{display last_char} while inside a function with an argument
5602 @code{last_char}, @value{GDBN} displays this argument while your program
5603 continues to stop inside that function. When it stops elsewhere---where
5604 there is no variable @code{last_char}---the display is disabled
5605 automatically. The next time your program stops where @code{last_char}
5606 is meaningful, you can enable the display expression once again.
5608 @node Print Settings
5609 @section Print settings
5611 @cindex format options
5612 @cindex print settings
5613 @value{GDBN} provides the following ways to control how arrays, structures,
5614 and symbols are printed.
5617 These settings are useful for debugging programs in any language:
5621 @item set print address
5622 @itemx set print address on
5623 @cindex print/don't print memory addresses
5624 @value{GDBN} prints memory addresses showing the location of stack
5625 traces, structure values, pointer values, breakpoints, and so forth,
5626 even when it also displays the contents of those addresses. The default
5627 is @code{on}. For example, this is what a stack frame display looks like with
5628 @code{set print address on}:
5633 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
5635 530 if (lquote != def_lquote)
5639 @item set print address off
5640 Do not print addresses when displaying their contents. For example,
5641 this is the same stack frame displayed with @code{set print address off}:
5645 (@value{GDBP}) set print addr off
5647 #0 set_quotes (lq="<<", rq=">>") at input.c:530
5648 530 if (lquote != def_lquote)
5652 You can use @samp{set print address off} to eliminate all machine
5653 dependent displays from the @value{GDBN} interface. For example, with
5654 @code{print address off}, you should get the same text for backtraces on
5655 all machines---whether or not they involve pointer arguments.
5658 @item show print address
5659 Show whether or not addresses are to be printed.
5662 When @value{GDBN} prints a symbolic address, it normally prints the
5663 closest earlier symbol plus an offset. If that symbol does not uniquely
5664 identify the address (for example, it is a name whose scope is a single
5665 source file), you may need to clarify. One way to do this is with
5666 @code{info line}, for example @samp{info line *0x4537}. Alternately,
5667 you can set @value{GDBN} to print the source file and line number when
5668 it prints a symbolic address:
5671 @item set print symbol-filename on
5672 @cindex source file and line of a symbol
5673 @cindex symbol, source file and line
5674 Tell @value{GDBN} to print the source file name and line number of a
5675 symbol in the symbolic form of an address.
5677 @item set print symbol-filename off
5678 Do not print source file name and line number of a symbol. This is the
5681 @item show print symbol-filename
5682 Show whether or not @value{GDBN} will print the source file name and
5683 line number of a symbol in the symbolic form of an address.
5686 Another situation where it is helpful to show symbol filenames and line
5687 numbers is when disassembling code; @value{GDBN} shows you the line
5688 number and source file that corresponds to each instruction.
5690 Also, you may wish to see the symbolic form only if the address being
5691 printed is reasonably close to the closest earlier symbol:
5694 @item set print max-symbolic-offset @var{max-offset}
5695 @cindex maximum value for offset of closest symbol
5696 Tell @value{GDBN} to only display the symbolic form of an address if the
5697 offset between the closest earlier symbol and the address is less than
5698 @var{max-offset}. The default is 0, which tells @value{GDBN}
5699 to always print the symbolic form of an address if any symbol precedes it.
5701 @item show print max-symbolic-offset
5702 Ask how large the maximum offset is that @value{GDBN} prints in a
5706 @cindex wild pointer, interpreting
5707 @cindex pointer, finding referent
5708 If you have a pointer and you are not sure where it points, try
5709 @samp{set print symbol-filename on}. Then you can determine the name
5710 and source file location of the variable where it points, using
5711 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
5712 For example, here @value{GDBN} shows that a variable @code{ptt} points
5713 at another variable @code{t}, defined in @file{hi2.c}:
5716 (@value{GDBP}) set print symbol-filename on
5717 (@value{GDBP}) p/a ptt
5718 $4 = 0xe008 <t in hi2.c>
5722 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
5723 does not show the symbol name and filename of the referent, even with
5724 the appropriate @code{set print} options turned on.
5727 Other settings control how different kinds of objects are printed:
5730 @item set print array
5731 @itemx set print array on
5732 @cindex pretty print arrays
5733 Pretty print arrays. This format is more convenient to read,
5734 but uses more space. The default is off.
5736 @item set print array off
5737 Return to compressed format for arrays.
5739 @item show print array
5740 Show whether compressed or pretty format is selected for displaying
5743 @cindex print array indexes
5744 @item set print array-indexes
5745 @itemx set print array-indexes on
5746 Print the index of each element when displaying arrays. May be more
5747 convenient to locate a given element in the array or quickly find the
5748 index of a given element in that printed array. The default is off.
5750 @item set print array-indexes off
5751 Stop printing element indexes when displaying arrays.
5753 @item show print array-indexes
5754 Show whether the index of each element is printed when displaying
5757 @item set print elements @var{number-of-elements}
5758 @cindex number of array elements to print
5759 @cindex limit on number of printed array elements
5760 Set a limit on how many elements of an array @value{GDBN} will print.
5761 If @value{GDBN} is printing a large array, it stops printing after it has
5762 printed the number of elements set by the @code{set print elements} command.
5763 This limit also applies to the display of strings.
5764 When @value{GDBN} starts, this limit is set to 200.
5765 Setting @var{number-of-elements} to zero means that the printing is unlimited.
5767 @item show print elements
5768 Display the number of elements of a large array that @value{GDBN} will print.
5769 If the number is 0, then the printing is unlimited.
5771 @item set print repeats
5772 @cindex repeated array elements
5773 Set the threshold for suppressing display of repeated array
5774 elelments. When the number of consecutive identical elements of an
5775 array exceeds the threshold, @value{GDBN} prints the string
5776 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
5777 identical repetitions, instead of displaying the identical elements
5778 themselves. Setting the threshold to zero will cause all elements to
5779 be individually printed. The default threshold is 10.
5781 @item show print repeats
5782 Display the current threshold for printing repeated identical
5785 @item set print null-stop
5786 @cindex @sc{null} elements in arrays
5787 Cause @value{GDBN} to stop printing the characters of an array when the first
5788 @sc{null} is encountered. This is useful when large arrays actually
5789 contain only short strings.
5792 @item show print null-stop
5793 Show whether @value{GDBN} stops printing an array on the first
5794 @sc{null} character.
5796 @item set print pretty on
5797 @cindex print structures in indented form
5798 @cindex indentation in structure display
5799 Cause @value{GDBN} to print structures in an indented format with one member
5800 per line, like this:
5815 @item set print pretty off
5816 Cause @value{GDBN} to print structures in a compact format, like this:
5820 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
5821 meat = 0x54 "Pork"@}
5826 This is the default format.
5828 @item show print pretty
5829 Show which format @value{GDBN} is using to print structures.
5831 @item set print sevenbit-strings on
5832 @cindex eight-bit characters in strings
5833 @cindex octal escapes in strings
5834 Print using only seven-bit characters; if this option is set,
5835 @value{GDBN} displays any eight-bit characters (in strings or
5836 character values) using the notation @code{\}@var{nnn}. This setting is
5837 best if you are working in English (@sc{ascii}) and you use the
5838 high-order bit of characters as a marker or ``meta'' bit.
5840 @item set print sevenbit-strings off
5841 Print full eight-bit characters. This allows the use of more
5842 international character sets, and is the default.
5844 @item show print sevenbit-strings
5845 Show whether or not @value{GDBN} is printing only seven-bit characters.
5847 @item set print union on
5848 @cindex unions in structures, printing
5849 Tell @value{GDBN} to print unions which are contained in structures
5850 and other unions. This is the default setting.
5852 @item set print union off
5853 Tell @value{GDBN} not to print unions which are contained in
5854 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
5857 @item show print union
5858 Ask @value{GDBN} whether or not it will print unions which are contained in
5859 structures and other unions.
5861 For example, given the declarations
5864 typedef enum @{Tree, Bug@} Species;
5865 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
5866 typedef enum @{Caterpillar, Cocoon, Butterfly@}
5877 struct thing foo = @{Tree, @{Acorn@}@};
5881 with @code{set print union on} in effect @samp{p foo} would print
5884 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
5888 and with @code{set print union off} in effect it would print
5891 $1 = @{it = Tree, form = @{...@}@}
5895 @code{set print union} affects programs written in C-like languages
5901 These settings are of interest when debugging C@t{++} programs:
5904 @cindex demangling C@t{++} names
5905 @item set print demangle
5906 @itemx set print demangle on
5907 Print C@t{++} names in their source form rather than in the encoded
5908 (``mangled'') form passed to the assembler and linker for type-safe
5909 linkage. The default is on.
5911 @item show print demangle
5912 Show whether C@t{++} names are printed in mangled or demangled form.
5914 @item set print asm-demangle
5915 @itemx set print asm-demangle on
5916 Print C@t{++} names in their source form rather than their mangled form, even
5917 in assembler code printouts such as instruction disassemblies.
5920 @item show print asm-demangle
5921 Show whether C@t{++} names in assembly listings are printed in mangled
5924 @cindex C@t{++} symbol decoding style
5925 @cindex symbol decoding style, C@t{++}
5926 @kindex set demangle-style
5927 @item set demangle-style @var{style}
5928 Choose among several encoding schemes used by different compilers to
5929 represent C@t{++} names. The choices for @var{style} are currently:
5933 Allow @value{GDBN} to choose a decoding style by inspecting your program.
5936 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
5937 This is the default.
5940 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
5943 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
5946 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
5947 @strong{Warning:} this setting alone is not sufficient to allow
5948 debugging @code{cfront}-generated executables. @value{GDBN} would
5949 require further enhancement to permit that.
5952 If you omit @var{style}, you will see a list of possible formats.
5954 @item show demangle-style
5955 Display the encoding style currently in use for decoding C@t{++} symbols.
5957 @item set print object
5958 @itemx set print object on
5959 @cindex derived type of an object, printing
5960 @cindex display derived types
5961 When displaying a pointer to an object, identify the @emph{actual}
5962 (derived) type of the object rather than the @emph{declared} type, using
5963 the virtual function table.
5965 @item set print object off
5966 Display only the declared type of objects, without reference to the
5967 virtual function table. This is the default setting.
5969 @item show print object
5970 Show whether actual, or declared, object types are displayed.
5972 @item set print static-members
5973 @itemx set print static-members on
5974 @cindex static members of C@t{++} objects
5975 Print static members when displaying a C@t{++} object. The default is on.
5977 @item set print static-members off
5978 Do not print static members when displaying a C@t{++} object.
5980 @item show print static-members
5981 Show whether C@t{++} static members are printed or not.
5983 @item set print pascal_static-members
5984 @itemx set print pascal_static-members on
5985 @cindex static members of Pacal objects
5986 @cindex Pacal objects, static members display
5987 Print static members when displaying a Pascal object. The default is on.
5989 @item set print pascal_static-members off
5990 Do not print static members when displaying a Pascal object.
5992 @item show print pascal_static-members
5993 Show whether Pascal static members are printed or not.
5995 @c These don't work with HP ANSI C++ yet.
5996 @item set print vtbl
5997 @itemx set print vtbl on
5998 @cindex pretty print C@t{++} virtual function tables
5999 @cindex virtual functions (C@t{++}) display
6000 @cindex VTBL display
6001 Pretty print C@t{++} virtual function tables. The default is off.
6002 (The @code{vtbl} commands do not work on programs compiled with the HP
6003 ANSI C@t{++} compiler (@code{aCC}).)
6005 @item set print vtbl off
6006 Do not pretty print C@t{++} virtual function tables.
6008 @item show print vtbl
6009 Show whether C@t{++} virtual function tables are pretty printed, or not.
6013 @section Value history
6015 @cindex value history
6016 @cindex history of values printed by @value{GDBN}
6017 Values printed by the @code{print} command are saved in the @value{GDBN}
6018 @dfn{value history}. This allows you to refer to them in other expressions.
6019 Values are kept until the symbol table is re-read or discarded
6020 (for example with the @code{file} or @code{symbol-file} commands).
6021 When the symbol table changes, the value history is discarded,
6022 since the values may contain pointers back to the types defined in the
6027 @cindex history number
6028 The values printed are given @dfn{history numbers} by which you can
6029 refer to them. These are successive integers starting with one.
6030 @code{print} shows you the history number assigned to a value by
6031 printing @samp{$@var{num} = } before the value; here @var{num} is the
6034 To refer to any previous value, use @samp{$} followed by the value's
6035 history number. The way @code{print} labels its output is designed to
6036 remind you of this. Just @code{$} refers to the most recent value in
6037 the history, and @code{$$} refers to the value before that.
6038 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
6039 is the value just prior to @code{$$}, @code{$$1} is equivalent to
6040 @code{$$}, and @code{$$0} is equivalent to @code{$}.
6042 For example, suppose you have just printed a pointer to a structure and
6043 want to see the contents of the structure. It suffices to type
6049 If you have a chain of structures where the component @code{next} points
6050 to the next one, you can print the contents of the next one with this:
6057 You can print successive links in the chain by repeating this
6058 command---which you can do by just typing @key{RET}.
6060 Note that the history records values, not expressions. If the value of
6061 @code{x} is 4 and you type these commands:
6069 then the value recorded in the value history by the @code{print} command
6070 remains 4 even though the value of @code{x} has changed.
6075 Print the last ten values in the value history, with their item numbers.
6076 This is like @samp{p@ $$9} repeated ten times, except that @code{show
6077 values} does not change the history.
6079 @item show values @var{n}
6080 Print ten history values centered on history item number @var{n}.
6083 Print ten history values just after the values last printed. If no more
6084 values are available, @code{show values +} produces no display.
6087 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
6088 same effect as @samp{show values +}.
6090 @node Convenience Vars
6091 @section Convenience variables
6093 @cindex convenience variables
6094 @cindex user-defined variables
6095 @value{GDBN} provides @dfn{convenience variables} that you can use within
6096 @value{GDBN} to hold on to a value and refer to it later. These variables
6097 exist entirely within @value{GDBN}; they are not part of your program, and
6098 setting a convenience variable has no direct effect on further execution
6099 of your program. That is why you can use them freely.
6101 Convenience variables are prefixed with @samp{$}. Any name preceded by
6102 @samp{$} can be used for a convenience variable, unless it is one of
6103 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
6104 (Value history references, in contrast, are @emph{numbers} preceded
6105 by @samp{$}. @xref{Value History, ,Value history}.)
6107 You can save a value in a convenience variable with an assignment
6108 expression, just as you would set a variable in your program.
6112 set $foo = *object_ptr
6116 would save in @code{$foo} the value contained in the object pointed to by
6119 Using a convenience variable for the first time creates it, but its
6120 value is @code{void} until you assign a new value. You can alter the
6121 value with another assignment at any time.
6123 Convenience variables have no fixed types. You can assign a convenience
6124 variable any type of value, including structures and arrays, even if
6125 that variable already has a value of a different type. The convenience
6126 variable, when used as an expression, has the type of its current value.
6129 @kindex show convenience
6130 @cindex show all user variables
6131 @item show convenience
6132 Print a list of convenience variables used so far, and their values.
6133 Abbreviated @code{show conv}.
6135 @kindex init-if-undefined
6136 @cindex convenience variables, initializing
6137 @item init-if-undefined $@var{variable} = @var{expression}
6138 Set a convenience variable if it has not already been set. This is useful
6139 for user-defined commands that keep some state. It is similar, in concept,
6140 to using local static variables with initializers in C (except that
6141 convenience variables are global). It can also be used to allow users to
6142 override default values used in a command script.
6144 If the variable is already defined then the expression is not evaluated so
6145 any side-effects do not occur.
6148 One of the ways to use a convenience variable is as a counter to be
6149 incremented or a pointer to be advanced. For example, to print
6150 a field from successive elements of an array of structures:
6154 print bar[$i++]->contents
6158 Repeat that command by typing @key{RET}.
6160 Some convenience variables are created automatically by @value{GDBN} and given
6161 values likely to be useful.
6164 @vindex $_@r{, convenience variable}
6166 The variable @code{$_} is automatically set by the @code{x} command to
6167 the last address examined (@pxref{Memory, ,Examining memory}). Other
6168 commands which provide a default address for @code{x} to examine also
6169 set @code{$_} to that address; these commands include @code{info line}
6170 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
6171 except when set by the @code{x} command, in which case it is a pointer
6172 to the type of @code{$__}.
6174 @vindex $__@r{, convenience variable}
6176 The variable @code{$__} is automatically set by the @code{x} command
6177 to the value found in the last address examined. Its type is chosen
6178 to match the format in which the data was printed.
6181 @vindex $_exitcode@r{, convenience variable}
6182 The variable @code{$_exitcode} is automatically set to the exit code when
6183 the program being debugged terminates.
6186 On HP-UX systems, if you refer to a function or variable name that
6187 begins with a dollar sign, @value{GDBN} searches for a user or system
6188 name first, before it searches for a convenience variable.
6194 You can refer to machine register contents, in expressions, as variables
6195 with names starting with @samp{$}. The names of registers are different
6196 for each machine; use @code{info registers} to see the names used on
6200 @kindex info registers
6201 @item info registers
6202 Print the names and values of all registers except floating-point
6203 and vector registers (in the selected stack frame).
6205 @kindex info all-registers
6206 @cindex floating point registers
6207 @item info all-registers
6208 Print the names and values of all registers, including floating-point
6209 and vector registers (in the selected stack frame).
6211 @item info registers @var{regname} @dots{}
6212 Print the @dfn{relativized} value of each specified register @var{regname}.
6213 As discussed in detail below, register values are normally relative to
6214 the selected stack frame. @var{regname} may be any register name valid on
6215 the machine you are using, with or without the initial @samp{$}.
6218 @cindex stack pointer register
6219 @cindex program counter register
6220 @cindex process status register
6221 @cindex frame pointer register
6222 @cindex standard registers
6223 @value{GDBN} has four ``standard'' register names that are available (in
6224 expressions) on most machines---whenever they do not conflict with an
6225 architecture's canonical mnemonics for registers. The register names
6226 @code{$pc} and @code{$sp} are used for the program counter register and
6227 the stack pointer. @code{$fp} is used for a register that contains a
6228 pointer to the current stack frame, and @code{$ps} is used for a
6229 register that contains the processor status. For example,
6230 you could print the program counter in hex with
6237 or print the instruction to be executed next with
6244 or add four to the stack pointer@footnote{This is a way of removing
6245 one word from the stack, on machines where stacks grow downward in
6246 memory (most machines, nowadays). This assumes that the innermost
6247 stack frame is selected; setting @code{$sp} is not allowed when other
6248 stack frames are selected. To pop entire frames off the stack,
6249 regardless of machine architecture, use @code{return};
6250 see @ref{Returning, ,Returning from a function}.} with
6256 Whenever possible, these four standard register names are available on
6257 your machine even though the machine has different canonical mnemonics,
6258 so long as there is no conflict. The @code{info registers} command
6259 shows the canonical names. For example, on the SPARC, @code{info
6260 registers} displays the processor status register as @code{$psr} but you
6261 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
6262 is an alias for the @sc{eflags} register.
6264 @value{GDBN} always considers the contents of an ordinary register as an
6265 integer when the register is examined in this way. Some machines have
6266 special registers which can hold nothing but floating point; these
6267 registers are considered to have floating point values. There is no way
6268 to refer to the contents of an ordinary register as floating point value
6269 (although you can @emph{print} it as a floating point value with
6270 @samp{print/f $@var{regname}}).
6272 Some registers have distinct ``raw'' and ``virtual'' data formats. This
6273 means that the data format in which the register contents are saved by
6274 the operating system is not the same one that your program normally
6275 sees. For example, the registers of the 68881 floating point
6276 coprocessor are always saved in ``extended'' (raw) format, but all C
6277 programs expect to work with ``double'' (virtual) format. In such
6278 cases, @value{GDBN} normally works with the virtual format only (the format
6279 that makes sense for your program), but the @code{info registers} command
6280 prints the data in both formats.
6282 Normally, register values are relative to the selected stack frame
6283 (@pxref{Selection, ,Selecting a frame}). This means that you get the
6284 value that the register would contain if all stack frames farther in
6285 were exited and their saved registers restored. In order to see the
6286 true contents of hardware registers, you must select the innermost
6287 frame (with @samp{frame 0}).
6289 However, @value{GDBN} must deduce where registers are saved, from the machine
6290 code generated by your compiler. If some registers are not saved, or if
6291 @value{GDBN} is unable to locate the saved registers, the selected stack
6292 frame makes no difference.
6294 @node Floating Point Hardware
6295 @section Floating point hardware
6296 @cindex floating point
6298 Depending on the configuration, @value{GDBN} may be able to give
6299 you more information about the status of the floating point hardware.
6304 Display hardware-dependent information about the floating
6305 point unit. The exact contents and layout vary depending on the
6306 floating point chip. Currently, @samp{info float} is supported on
6307 the ARM and x86 machines.
6311 @section Vector Unit
6314 Depending on the configuration, @value{GDBN} may be able to give you
6315 more information about the status of the vector unit.
6320 Display information about the vector unit. The exact contents and
6321 layout vary depending on the hardware.
6324 @node OS Information
6325 @section Operating system auxiliary information
6326 @cindex OS information
6328 @value{GDBN} provides interfaces to useful OS facilities that can help
6329 you debug your program.
6331 @cindex @code{ptrace} system call
6332 @cindex @code{struct user} contents
6333 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
6334 machines), it interfaces with the inferior via the @code{ptrace}
6335 system call. The operating system creates a special sata structure,
6336 called @code{struct user}, for this interface. You can use the
6337 command @code{info udot} to display the contents of this data
6343 Display the contents of the @code{struct user} maintained by the OS
6344 kernel for the program being debugged. @value{GDBN} displays the
6345 contents of @code{struct user} as a list of hex numbers, similar to
6346 the @code{examine} command.
6349 @cindex auxiliary vector
6350 @cindex vector, auxiliary
6351 Some operating systems supply an @dfn{auxiliary vector} to programs at
6352 startup. This is akin to the arguments and environment that you
6353 specify for a program, but contains a system-dependent variety of
6354 binary values that tell system libraries important details about the
6355 hardware, operating system, and process. Each value's purpose is
6356 identified by an integer tag; the meanings are well-known but system-specific.
6357 Depending on the configuration and operating system facilities,
6358 @value{GDBN} may be able to show you this information. For remote
6359 targets, this functionality may further depend on the remote stub's
6360 support of the @samp{qPart:auxv:read} packet, see @ref{Remote
6361 configuration, auxiliary vector}.
6366 Display the auxiliary vector of the inferior, which can be either a
6367 live process or a core dump file. @value{GDBN} prints each tag value
6368 numerically, and also shows names and text descriptions for recognized
6369 tags. Some values in the vector are numbers, some bit masks, and some
6370 pointers to strings or other data. @value{GDBN} displays each value in the
6371 most appropriate form for a recognized tag, and in hexadecimal for
6372 an unrecognized tag.
6376 @node Memory Region Attributes
6377 @section Memory region attributes
6378 @cindex memory region attributes
6380 @dfn{Memory region attributes} allow you to describe special handling
6381 required by regions of your target's memory. @value{GDBN} uses attributes
6382 to determine whether to allow certain types of memory accesses; whether to
6383 use specific width accesses; and whether to cache target memory.
6385 Defined memory regions can be individually enabled and disabled. When a
6386 memory region is disabled, @value{GDBN} uses the default attributes when
6387 accessing memory in that region. Similarly, if no memory regions have
6388 been defined, @value{GDBN} uses the default attributes when accessing
6391 When a memory region is defined, it is given a number to identify it;
6392 to enable, disable, or remove a memory region, you specify that number.
6396 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
6397 Define a memory region bounded by @var{lower} and @var{upper} with
6398 attributes @var{attributes}@dots{}, and add it to the list of regions
6399 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
6400 case: it is treated as the the target's maximum memory address.
6401 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
6404 @item delete mem @var{nums}@dots{}
6405 Remove memory regions @var{nums}@dots{} from the list of regions
6406 monitored by @value{GDBN}.
6409 @item disable mem @var{nums}@dots{}
6410 Disable monitoring of memory regions @var{nums}@dots{}.
6411 A disabled memory region is not forgotten.
6412 It may be enabled again later.
6415 @item enable mem @var{nums}@dots{}
6416 Enable monitoring of memory regions @var{nums}@dots{}.
6420 Print a table of all defined memory regions, with the following columns
6424 @item Memory Region Number
6425 @item Enabled or Disabled.
6426 Enabled memory regions are marked with @samp{y}.
6427 Disabled memory regions are marked with @samp{n}.
6430 The address defining the inclusive lower bound of the memory region.
6433 The address defining the exclusive upper bound of the memory region.
6436 The list of attributes set for this memory region.
6441 @subsection Attributes
6443 @subsubsection Memory Access Mode
6444 The access mode attributes set whether @value{GDBN} may make read or
6445 write accesses to a memory region.
6447 While these attributes prevent @value{GDBN} from performing invalid
6448 memory accesses, they do nothing to prevent the target system, I/O DMA,
6449 etc.@: from accessing memory.
6453 Memory is read only.
6455 Memory is write only.
6457 Memory is read/write. This is the default.
6460 @subsubsection Memory Access Size
6461 The acccess size attributes tells @value{GDBN} to use specific sized
6462 accesses in the memory region. Often memory mapped device registers
6463 require specific sized accesses. If no access size attribute is
6464 specified, @value{GDBN} may use accesses of any size.
6468 Use 8 bit memory accesses.
6470 Use 16 bit memory accesses.
6472 Use 32 bit memory accesses.
6474 Use 64 bit memory accesses.
6477 @c @subsubsection Hardware/Software Breakpoints
6478 @c The hardware/software breakpoint attributes set whether @value{GDBN}
6479 @c will use hardware or software breakpoints for the internal breakpoints
6480 @c used by the step, next, finish, until, etc. commands.
6484 @c Always use hardware breakpoints
6485 @c @item swbreak (default)
6488 @subsubsection Data Cache
6489 The data cache attributes set whether @value{GDBN} will cache target
6490 memory. While this generally improves performance by reducing debug
6491 protocol overhead, it can lead to incorrect results because @value{GDBN}
6492 does not know about volatile variables or memory mapped device
6497 Enable @value{GDBN} to cache target memory.
6499 Disable @value{GDBN} from caching target memory. This is the default.
6502 @c @subsubsection Memory Write Verification
6503 @c The memory write verification attributes set whether @value{GDBN}
6504 @c will re-reads data after each write to verify the write was successful.
6508 @c @item noverify (default)
6511 @node Dump/Restore Files
6512 @section Copy between memory and a file
6513 @cindex dump/restore files
6514 @cindex append data to a file
6515 @cindex dump data to a file
6516 @cindex restore data from a file
6518 You can use the commands @code{dump}, @code{append}, and
6519 @code{restore} to copy data between target memory and a file. The
6520 @code{dump} and @code{append} commands write data to a file, and the
6521 @code{restore} command reads data from a file back into the inferior's
6522 memory. Files may be in binary, Motorola S-record, Intel hex, or
6523 Tektronix Hex format; however, @value{GDBN} can only append to binary
6529 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6530 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
6531 Dump the contents of memory from @var{start_addr} to @var{end_addr},
6532 or the value of @var{expr}, to @var{filename} in the given format.
6534 The @var{format} parameter may be any one of:
6541 Motorola S-record format.
6543 Tektronix Hex format.
6546 @value{GDBN} uses the same definitions of these formats as the
6547 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
6548 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
6552 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6553 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
6554 Append the contents of memory from @var{start_addr} to @var{end_addr},
6555 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
6556 (@value{GDBN} can only append data to files in raw binary form.)
6559 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
6560 Restore the contents of file @var{filename} into memory. The
6561 @code{restore} command can automatically recognize any known @sc{bfd}
6562 file format, except for raw binary. To restore a raw binary file you
6563 must specify the optional keyword @code{binary} after the filename.
6565 If @var{bias} is non-zero, its value will be added to the addresses
6566 contained in the file. Binary files always start at address zero, so
6567 they will be restored at address @var{bias}. Other bfd files have
6568 a built-in location; they will be restored at offset @var{bias}
6571 If @var{start} and/or @var{end} are non-zero, then only data between
6572 file offset @var{start} and file offset @var{end} will be restored.
6573 These offsets are relative to the addresses in the file, before
6574 the @var{bias} argument is applied.
6578 @node Core File Generation
6579 @section How to Produce a Core File from Your Program
6580 @cindex dump core from inferior
6582 A @dfn{core file} or @dfn{core dump} is a file that records the memory
6583 image of a running process and its process status (register values
6584 etc.). Its primary use is post-mortem debugging of a program that
6585 crashed while it ran outside a debugger. A program that crashes
6586 automatically produces a core file, unless this feature is disabled by
6587 the user. @xref{Files}, for information on invoking @value{GDBN} in
6588 the post-mortem debugging mode.
6590 Occasionally, you may wish to produce a core file of the program you
6591 are debugging in order to preserve a snapshot of its state.
6592 @value{GDBN} has a special command for that.
6596 @kindex generate-core-file
6597 @item generate-core-file [@var{file}]
6598 @itemx gcore [@var{file}]
6599 Produce a core dump of the inferior process. The optional argument
6600 @var{file} specifies the file name where to put the core dump. If not
6601 specified, the file name defaults to @file{core.@var{pid}}, where
6602 @var{pid} is the inferior process ID.
6604 Note that this command is implemented only for some systems (as of
6605 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
6608 @node Character Sets
6609 @section Character Sets
6610 @cindex character sets
6612 @cindex translating between character sets
6613 @cindex host character set
6614 @cindex target character set
6616 If the program you are debugging uses a different character set to
6617 represent characters and strings than the one @value{GDBN} uses itself,
6618 @value{GDBN} can automatically translate between the character sets for
6619 you. The character set @value{GDBN} uses we call the @dfn{host
6620 character set}; the one the inferior program uses we call the
6621 @dfn{target character set}.
6623 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
6624 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
6625 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
6626 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
6627 then the host character set is Latin-1, and the target character set is
6628 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
6629 target-charset EBCDIC-US}, then @value{GDBN} translates between
6630 @sc{ebcdic} and Latin 1 as you print character or string values, or use
6631 character and string literals in expressions.
6633 @value{GDBN} has no way to automatically recognize which character set
6634 the inferior program uses; you must tell it, using the @code{set
6635 target-charset} command, described below.
6637 Here are the commands for controlling @value{GDBN}'s character set
6641 @item set target-charset @var{charset}
6642 @kindex set target-charset
6643 Set the current target character set to @var{charset}. We list the
6644 character set names @value{GDBN} recognizes below, but if you type
6645 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6646 list the target character sets it supports.
6650 @item set host-charset @var{charset}
6651 @kindex set host-charset
6652 Set the current host character set to @var{charset}.
6654 By default, @value{GDBN} uses a host character set appropriate to the
6655 system it is running on; you can override that default using the
6656 @code{set host-charset} command.
6658 @value{GDBN} can only use certain character sets as its host character
6659 set. We list the character set names @value{GDBN} recognizes below, and
6660 indicate which can be host character sets, but if you type
6661 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6662 list the host character sets it supports.
6664 @item set charset @var{charset}
6666 Set the current host and target character sets to @var{charset}. As
6667 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
6668 @value{GDBN} will list the name of the character sets that can be used
6669 for both host and target.
6673 @kindex show charset
6674 Show the names of the current host and target charsets.
6676 @itemx show host-charset
6677 @kindex show host-charset
6678 Show the name of the current host charset.
6680 @itemx show target-charset
6681 @kindex show target-charset
6682 Show the name of the current target charset.
6686 @value{GDBN} currently includes support for the following character
6692 @cindex ASCII character set
6693 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
6697 @cindex ISO 8859-1 character set
6698 @cindex ISO Latin 1 character set
6699 The ISO Latin 1 character set. This extends @sc{ascii} with accented
6700 characters needed for French, German, and Spanish. @value{GDBN} can use
6701 this as its host character set.
6705 @cindex EBCDIC character set
6706 @cindex IBM1047 character set
6707 Variants of the @sc{ebcdic} character set, used on some of IBM's
6708 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
6709 @value{GDBN} cannot use these as its host character set.
6713 Note that these are all single-byte character sets. More work inside
6714 GDB is needed to support multi-byte or variable-width character
6715 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
6717 Here is an example of @value{GDBN}'s character set support in action.
6718 Assume that the following source code has been placed in the file
6719 @file{charset-test.c}:
6725 = @{72, 101, 108, 108, 111, 44, 32, 119,
6726 111, 114, 108, 100, 33, 10, 0@};
6727 char ibm1047_hello[]
6728 = @{200, 133, 147, 147, 150, 107, 64, 166,
6729 150, 153, 147, 132, 90, 37, 0@};
6733 printf ("Hello, world!\n");
6737 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
6738 containing the string @samp{Hello, world!} followed by a newline,
6739 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
6741 We compile the program, and invoke the debugger on it:
6744 $ gcc -g charset-test.c -o charset-test
6745 $ gdb -nw charset-test
6746 GNU gdb 2001-12-19-cvs
6747 Copyright 2001 Free Software Foundation, Inc.
6752 We can use the @code{show charset} command to see what character sets
6753 @value{GDBN} is currently using to interpret and display characters and
6757 (@value{GDBP}) show charset
6758 The current host and target character set is `ISO-8859-1'.
6762 For the sake of printing this manual, let's use @sc{ascii} as our
6763 initial character set:
6765 (@value{GDBP}) set charset ASCII
6766 (@value{GDBP}) show charset
6767 The current host and target character set is `ASCII'.
6771 Let's assume that @sc{ascii} is indeed the correct character set for our
6772 host system --- in other words, let's assume that if @value{GDBN} prints
6773 characters using the @sc{ascii} character set, our terminal will display
6774 them properly. Since our current target character set is also
6775 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
6778 (@value{GDBP}) print ascii_hello
6779 $1 = 0x401698 "Hello, world!\n"
6780 (@value{GDBP}) print ascii_hello[0]
6785 @value{GDBN} uses the target character set for character and string
6786 literals you use in expressions:
6789 (@value{GDBP}) print '+'
6794 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
6797 @value{GDBN} relies on the user to tell it which character set the
6798 target program uses. If we print @code{ibm1047_hello} while our target
6799 character set is still @sc{ascii}, we get jibberish:
6802 (@value{GDBP}) print ibm1047_hello
6803 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
6804 (@value{GDBP}) print ibm1047_hello[0]
6809 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
6810 @value{GDBN} tells us the character sets it supports:
6813 (@value{GDBP}) set target-charset
6814 ASCII EBCDIC-US IBM1047 ISO-8859-1
6815 (@value{GDBP}) set target-charset
6818 We can select @sc{ibm1047} as our target character set, and examine the
6819 program's strings again. Now the @sc{ascii} string is wrong, but
6820 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
6821 target character set, @sc{ibm1047}, to the host character set,
6822 @sc{ascii}, and they display correctly:
6825 (@value{GDBP}) set target-charset IBM1047
6826 (@value{GDBP}) show charset
6827 The current host character set is `ASCII'.
6828 The current target character set is `IBM1047'.
6829 (@value{GDBP}) print ascii_hello
6830 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
6831 (@value{GDBP}) print ascii_hello[0]
6833 (@value{GDBP}) print ibm1047_hello
6834 $8 = 0x4016a8 "Hello, world!\n"
6835 (@value{GDBP}) print ibm1047_hello[0]
6840 As above, @value{GDBN} uses the target character set for character and
6841 string literals you use in expressions:
6844 (@value{GDBP}) print '+'
6849 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
6852 @node Caching Remote Data
6853 @section Caching Data of Remote Targets
6854 @cindex caching data of remote targets
6856 @value{GDBN} can cache data exchanged between the debugger and a
6857 remote target (@pxref{Remote}). Such caching generally improves
6858 performance, because it reduces the overhead of the remote protocol by
6859 bundling memory reads and writes into large chunks. Unfortunately,
6860 @value{GDBN} does not currently know anything about volatile
6861 registers, and thus data caching will produce incorrect results when
6862 volatile registers are in use.
6865 @kindex set remotecache
6866 @item set remotecache on
6867 @itemx set remotecache off
6868 Set caching state for remote targets. When @code{ON}, use data
6869 caching. By default, this option is @code{OFF}.
6871 @kindex show remotecache
6872 @item show remotecache
6873 Show the current state of data caching for remote targets.
6877 Print the information about the data cache performance. The
6878 information displayed includes: the dcache width and depth; and for
6879 each cache line, how many times it was referenced, and its data and
6880 state (dirty, bad, ok, etc.). This command is useful for debugging
6881 the data cache operation.
6886 @chapter C Preprocessor Macros
6888 Some languages, such as C and C@t{++}, provide a way to define and invoke
6889 ``preprocessor macros'' which expand into strings of tokens.
6890 @value{GDBN} can evaluate expressions containing macro invocations, show
6891 the result of macro expansion, and show a macro's definition, including
6892 where it was defined.
6894 You may need to compile your program specially to provide @value{GDBN}
6895 with information about preprocessor macros. Most compilers do not
6896 include macros in their debugging information, even when you compile
6897 with the @option{-g} flag. @xref{Compilation}.
6899 A program may define a macro at one point, remove that definition later,
6900 and then provide a different definition after that. Thus, at different
6901 points in the program, a macro may have different definitions, or have
6902 no definition at all. If there is a current stack frame, @value{GDBN}
6903 uses the macros in scope at that frame's source code line. Otherwise,
6904 @value{GDBN} uses the macros in scope at the current listing location;
6907 At the moment, @value{GDBN} does not support the @code{##}
6908 token-splicing operator, the @code{#} stringification operator, or
6909 variable-arity macros.
6911 Whenever @value{GDBN} evaluates an expression, it always expands any
6912 macro invocations present in the expression. @value{GDBN} also provides
6913 the following commands for working with macros explicitly.
6917 @kindex macro expand
6918 @cindex macro expansion, showing the results of preprocessor
6919 @cindex preprocessor macro expansion, showing the results of
6920 @cindex expanding preprocessor macros
6921 @item macro expand @var{expression}
6922 @itemx macro exp @var{expression}
6923 Show the results of expanding all preprocessor macro invocations in
6924 @var{expression}. Since @value{GDBN} simply expands macros, but does
6925 not parse the result, @var{expression} need not be a valid expression;
6926 it can be any string of tokens.
6929 @item macro expand-once @var{expression}
6930 @itemx macro exp1 @var{expression}
6931 @cindex expand macro once
6932 @i{(This command is not yet implemented.)} Show the results of
6933 expanding those preprocessor macro invocations that appear explicitly in
6934 @var{expression}. Macro invocations appearing in that expansion are
6935 left unchanged. This command allows you to see the effect of a
6936 particular macro more clearly, without being confused by further
6937 expansions. Since @value{GDBN} simply expands macros, but does not
6938 parse the result, @var{expression} need not be a valid expression; it
6939 can be any string of tokens.
6942 @cindex macro definition, showing
6943 @cindex definition, showing a macro's
6944 @item info macro @var{macro}
6945 Show the definition of the macro named @var{macro}, and describe the
6946 source location where that definition was established.
6948 @kindex macro define
6949 @cindex user-defined macros
6950 @cindex defining macros interactively
6951 @cindex macros, user-defined
6952 @item macro define @var{macro} @var{replacement-list}
6953 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
6954 @i{(This command is not yet implemented.)} Introduce a definition for a
6955 preprocessor macro named @var{macro}, invocations of which are replaced
6956 by the tokens given in @var{replacement-list}. The first form of this
6957 command defines an ``object-like'' macro, which takes no arguments; the
6958 second form defines a ``function-like'' macro, which takes the arguments
6959 given in @var{arglist}.
6961 A definition introduced by this command is in scope in every expression
6962 evaluated in @value{GDBN}, until it is removed with the @command{macro
6963 undef} command, described below. The definition overrides all
6964 definitions for @var{macro} present in the program being debugged, as
6965 well as any previous user-supplied definition.
6968 @item macro undef @var{macro}
6969 @i{(This command is not yet implemented.)} Remove any user-supplied
6970 definition for the macro named @var{macro}. This command only affects
6971 definitions provided with the @command{macro define} command, described
6972 above; it cannot remove definitions present in the program being
6977 @i{(This command is not yet implemented.)} List all the macros
6978 defined using the @code{macro define} command.
6981 @cindex macros, example of debugging with
6982 Here is a transcript showing the above commands in action. First, we
6983 show our source files:
6991 #define ADD(x) (M + x)
6996 printf ("Hello, world!\n");
6998 printf ("We're so creative.\n");
7000 printf ("Goodbye, world!\n");
7007 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
7008 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
7009 compiler includes information about preprocessor macros in the debugging
7013 $ gcc -gdwarf-2 -g3 sample.c -o sample
7017 Now, we start @value{GDBN} on our sample program:
7021 GNU gdb 2002-05-06-cvs
7022 Copyright 2002 Free Software Foundation, Inc.
7023 GDB is free software, @dots{}
7027 We can expand macros and examine their definitions, even when the
7028 program is not running. @value{GDBN} uses the current listing position
7029 to decide which macro definitions are in scope:
7032 (@value{GDBP}) list main
7035 5 #define ADD(x) (M + x)
7040 10 printf ("Hello, world!\n");
7042 12 printf ("We're so creative.\n");
7043 (@value{GDBP}) info macro ADD
7044 Defined at /home/jimb/gdb/macros/play/sample.c:5
7045 #define ADD(x) (M + x)
7046 (@value{GDBP}) info macro Q
7047 Defined at /home/jimb/gdb/macros/play/sample.h:1
7048 included at /home/jimb/gdb/macros/play/sample.c:2
7050 (@value{GDBP}) macro expand ADD(1)
7051 expands to: (42 + 1)
7052 (@value{GDBP}) macro expand-once ADD(1)
7053 expands to: once (M + 1)
7057 In the example above, note that @command{macro expand-once} expands only
7058 the macro invocation explicit in the original text --- the invocation of
7059 @code{ADD} --- but does not expand the invocation of the macro @code{M},
7060 which was introduced by @code{ADD}.
7062 Once the program is running, GDB uses the macro definitions in force at
7063 the source line of the current stack frame:
7066 (@value{GDBP}) break main
7067 Breakpoint 1 at 0x8048370: file sample.c, line 10.
7069 Starting program: /home/jimb/gdb/macros/play/sample
7071 Breakpoint 1, main () at sample.c:10
7072 10 printf ("Hello, world!\n");
7076 At line 10, the definition of the macro @code{N} at line 9 is in force:
7079 (@value{GDBP}) info macro N
7080 Defined at /home/jimb/gdb/macros/play/sample.c:9
7082 (@value{GDBP}) macro expand N Q M
7084 (@value{GDBP}) print N Q M
7089 As we step over directives that remove @code{N}'s definition, and then
7090 give it a new definition, @value{GDBN} finds the definition (or lack
7091 thereof) in force at each point:
7096 12 printf ("We're so creative.\n");
7097 (@value{GDBP}) info macro N
7098 The symbol `N' has no definition as a C/C++ preprocessor macro
7099 at /home/jimb/gdb/macros/play/sample.c:12
7102 14 printf ("Goodbye, world!\n");
7103 (@value{GDBP}) info macro N
7104 Defined at /home/jimb/gdb/macros/play/sample.c:13
7106 (@value{GDBP}) macro expand N Q M
7107 expands to: 1729 < 42
7108 (@value{GDBP}) print N Q M
7115 @chapter Tracepoints
7116 @c This chapter is based on the documentation written by Michael
7117 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
7120 In some applications, it is not feasible for the debugger to interrupt
7121 the program's execution long enough for the developer to learn
7122 anything helpful about its behavior. If the program's correctness
7123 depends on its real-time behavior, delays introduced by a debugger
7124 might cause the program to change its behavior drastically, or perhaps
7125 fail, even when the code itself is correct. It is useful to be able
7126 to observe the program's behavior without interrupting it.
7128 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
7129 specify locations in the program, called @dfn{tracepoints}, and
7130 arbitrary expressions to evaluate when those tracepoints are reached.
7131 Later, using the @code{tfind} command, you can examine the values
7132 those expressions had when the program hit the tracepoints. The
7133 expressions may also denote objects in memory---structures or arrays,
7134 for example---whose values @value{GDBN} should record; while visiting
7135 a particular tracepoint, you may inspect those objects as if they were
7136 in memory at that moment. However, because @value{GDBN} records these
7137 values without interacting with you, it can do so quickly and
7138 unobtrusively, hopefully not disturbing the program's behavior.
7140 The tracepoint facility is currently available only for remote
7141 targets. @xref{Targets}. In addition, your remote target must know
7142 how to collect trace data. This functionality is implemented in the
7143 remote stub; however, none of the stubs distributed with @value{GDBN}
7144 support tracepoints as of this writing. The format of the remote
7145 packets used to implement tracepoints are described in @ref{Tracepoint
7148 This chapter describes the tracepoint commands and features.
7152 * Analyze Collected Data::
7153 * Tracepoint Variables::
7156 @node Set Tracepoints
7157 @section Commands to Set Tracepoints
7159 Before running such a @dfn{trace experiment}, an arbitrary number of
7160 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
7161 tracepoint has a number assigned to it by @value{GDBN}. Like with
7162 breakpoints, tracepoint numbers are successive integers starting from
7163 one. Many of the commands associated with tracepoints take the
7164 tracepoint number as their argument, to identify which tracepoint to
7167 For each tracepoint, you can specify, in advance, some arbitrary set
7168 of data that you want the target to collect in the trace buffer when
7169 it hits that tracepoint. The collected data can include registers,
7170 local variables, or global data. Later, you can use @value{GDBN}
7171 commands to examine the values these data had at the time the
7174 This section describes commands to set tracepoints and associated
7175 conditions and actions.
7178 * Create and Delete Tracepoints::
7179 * Enable and Disable Tracepoints::
7180 * Tracepoint Passcounts::
7181 * Tracepoint Actions::
7182 * Listing Tracepoints::
7183 * Starting and Stopping Trace Experiment::
7186 @node Create and Delete Tracepoints
7187 @subsection Create and Delete Tracepoints
7190 @cindex set tracepoint
7193 The @code{trace} command is very similar to the @code{break} command.
7194 Its argument can be a source line, a function name, or an address in
7195 the target program. @xref{Set Breaks}. The @code{trace} command
7196 defines a tracepoint, which is a point in the target program where the
7197 debugger will briefly stop, collect some data, and then allow the
7198 program to continue. Setting a tracepoint or changing its commands
7199 doesn't take effect until the next @code{tstart} command; thus, you
7200 cannot change the tracepoint attributes once a trace experiment is
7203 Here are some examples of using the @code{trace} command:
7206 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
7208 (@value{GDBP}) @b{trace +2} // 2 lines forward
7210 (@value{GDBP}) @b{trace my_function} // first source line of function
7212 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
7214 (@value{GDBP}) @b{trace *0x2117c4} // an address
7218 You can abbreviate @code{trace} as @code{tr}.
7221 @cindex last tracepoint number
7222 @cindex recent tracepoint number
7223 @cindex tracepoint number
7224 The convenience variable @code{$tpnum} records the tracepoint number
7225 of the most recently set tracepoint.
7227 @kindex delete tracepoint
7228 @cindex tracepoint deletion
7229 @item delete tracepoint @r{[}@var{num}@r{]}
7230 Permanently delete one or more tracepoints. With no argument, the
7231 default is to delete all tracepoints.
7236 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
7238 (@value{GDBP}) @b{delete trace} // remove all tracepoints
7242 You can abbreviate this command as @code{del tr}.
7245 @node Enable and Disable Tracepoints
7246 @subsection Enable and Disable Tracepoints
7249 @kindex disable tracepoint
7250 @item disable tracepoint @r{[}@var{num}@r{]}
7251 Disable tracepoint @var{num}, or all tracepoints if no argument
7252 @var{num} is given. A disabled tracepoint will have no effect during
7253 the next trace experiment, but it is not forgotten. You can re-enable
7254 a disabled tracepoint using the @code{enable tracepoint} command.
7256 @kindex enable tracepoint
7257 @item enable tracepoint @r{[}@var{num}@r{]}
7258 Enable tracepoint @var{num}, or all tracepoints. The enabled
7259 tracepoints will become effective the next time a trace experiment is
7263 @node Tracepoint Passcounts
7264 @subsection Tracepoint Passcounts
7268 @cindex tracepoint pass count
7269 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
7270 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
7271 automatically stop a trace experiment. If a tracepoint's passcount is
7272 @var{n}, then the trace experiment will be automatically stopped on
7273 the @var{n}'th time that tracepoint is hit. If the tracepoint number
7274 @var{num} is not specified, the @code{passcount} command sets the
7275 passcount of the most recently defined tracepoint. If no passcount is
7276 given, the trace experiment will run until stopped explicitly by the
7282 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
7283 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
7285 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
7286 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
7287 (@value{GDBP}) @b{trace foo}
7288 (@value{GDBP}) @b{pass 3}
7289 (@value{GDBP}) @b{trace bar}
7290 (@value{GDBP}) @b{pass 2}
7291 (@value{GDBP}) @b{trace baz}
7292 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
7293 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
7294 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
7295 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
7299 @node Tracepoint Actions
7300 @subsection Tracepoint Action Lists
7304 @cindex tracepoint actions
7305 @item actions @r{[}@var{num}@r{]}
7306 This command will prompt for a list of actions to be taken when the
7307 tracepoint is hit. If the tracepoint number @var{num} is not
7308 specified, this command sets the actions for the one that was most
7309 recently defined (so that you can define a tracepoint and then say
7310 @code{actions} without bothering about its number). You specify the
7311 actions themselves on the following lines, one action at a time, and
7312 terminate the actions list with a line containing just @code{end}. So
7313 far, the only defined actions are @code{collect} and
7314 @code{while-stepping}.
7316 @cindex remove actions from a tracepoint
7317 To remove all actions from a tracepoint, type @samp{actions @var{num}}
7318 and follow it immediately with @samp{end}.
7321 (@value{GDBP}) @b{collect @var{data}} // collect some data
7323 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
7325 (@value{GDBP}) @b{end} // signals the end of actions.
7328 In the following example, the action list begins with @code{collect}
7329 commands indicating the things to be collected when the tracepoint is
7330 hit. Then, in order to single-step and collect additional data
7331 following the tracepoint, a @code{while-stepping} command is used,
7332 followed by the list of things to be collected while stepping. The
7333 @code{while-stepping} command is terminated by its own separate
7334 @code{end} command. Lastly, the action list is terminated by an
7338 (@value{GDBP}) @b{trace foo}
7339 (@value{GDBP}) @b{actions}
7340 Enter actions for tracepoint 1, one per line:
7349 @kindex collect @r{(tracepoints)}
7350 @item collect @var{expr1}, @var{expr2}, @dots{}
7351 Collect values of the given expressions when the tracepoint is hit.
7352 This command accepts a comma-separated list of any valid expressions.
7353 In addition to global, static, or local variables, the following
7354 special arguments are supported:
7358 collect all registers
7361 collect all function arguments
7364 collect all local variables.
7367 You can give several consecutive @code{collect} commands, each one
7368 with a single argument, or one @code{collect} command with several
7369 arguments separated by commas: the effect is the same.
7371 The command @code{info scope} (@pxref{Symbols, info scope}) is
7372 particularly useful for figuring out what data to collect.
7374 @kindex while-stepping @r{(tracepoints)}
7375 @item while-stepping @var{n}
7376 Perform @var{n} single-step traces after the tracepoint, collecting
7377 new data at each step. The @code{while-stepping} command is
7378 followed by the list of what to collect while stepping (followed by
7379 its own @code{end} command):
7383 > collect $regs, myglobal
7389 You may abbreviate @code{while-stepping} as @code{ws} or
7393 @node Listing Tracepoints
7394 @subsection Listing Tracepoints
7397 @kindex info tracepoints
7399 @cindex information about tracepoints
7400 @item info tracepoints @r{[}@var{num}@r{]}
7401 Display information about the tracepoint @var{num}. If you don't specify
7402 a tracepoint number, displays information about all the tracepoints
7403 defined so far. For each tracepoint, the following information is
7410 whether it is enabled or disabled
7414 its passcount as given by the @code{passcount @var{n}} command
7416 its step count as given by the @code{while-stepping @var{n}} command
7418 where in the source files is the tracepoint set
7420 its action list as given by the @code{actions} command
7424 (@value{GDBP}) @b{info trace}
7425 Num Enb Address PassC StepC What
7426 1 y 0x002117c4 0 0 <gdb_asm>
7427 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
7428 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
7433 This command can be abbreviated @code{info tp}.
7436 @node Starting and Stopping Trace Experiment
7437 @subsection Starting and Stopping Trace Experiment
7441 @cindex start a new trace experiment
7442 @cindex collected data discarded
7444 This command takes no arguments. It starts the trace experiment, and
7445 begins collecting data. This has the side effect of discarding all
7446 the data collected in the trace buffer during the previous trace
7450 @cindex stop a running trace experiment
7452 This command takes no arguments. It ends the trace experiment, and
7453 stops collecting data.
7455 @strong{Note}: a trace experiment and data collection may stop
7456 automatically if any tracepoint's passcount is reached
7457 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
7460 @cindex status of trace data collection
7461 @cindex trace experiment, status of
7463 This command displays the status of the current trace data
7467 Here is an example of the commands we described so far:
7470 (@value{GDBP}) @b{trace gdb_c_test}
7471 (@value{GDBP}) @b{actions}
7472 Enter actions for tracepoint #1, one per line.
7473 > collect $regs,$locals,$args
7478 (@value{GDBP}) @b{tstart}
7479 [time passes @dots{}]
7480 (@value{GDBP}) @b{tstop}
7484 @node Analyze Collected Data
7485 @section Using the collected data
7487 After the tracepoint experiment ends, you use @value{GDBN} commands
7488 for examining the trace data. The basic idea is that each tracepoint
7489 collects a trace @dfn{snapshot} every time it is hit and another
7490 snapshot every time it single-steps. All these snapshots are
7491 consecutively numbered from zero and go into a buffer, and you can
7492 examine them later. The way you examine them is to @dfn{focus} on a
7493 specific trace snapshot. When the remote stub is focused on a trace
7494 snapshot, it will respond to all @value{GDBN} requests for memory and
7495 registers by reading from the buffer which belongs to that snapshot,
7496 rather than from @emph{real} memory or registers of the program being
7497 debugged. This means that @strong{all} @value{GDBN} commands
7498 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
7499 behave as if we were currently debugging the program state as it was
7500 when the tracepoint occurred. Any requests for data that are not in
7501 the buffer will fail.
7504 * tfind:: How to select a trace snapshot
7505 * tdump:: How to display all data for a snapshot
7506 * save-tracepoints:: How to save tracepoints for a future run
7510 @subsection @code{tfind @var{n}}
7513 @cindex select trace snapshot
7514 @cindex find trace snapshot
7515 The basic command for selecting a trace snapshot from the buffer is
7516 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
7517 counting from zero. If no argument @var{n} is given, the next
7518 snapshot is selected.
7520 Here are the various forms of using the @code{tfind} command.
7524 Find the first snapshot in the buffer. This is a synonym for
7525 @code{tfind 0} (since 0 is the number of the first snapshot).
7528 Stop debugging trace snapshots, resume @emph{live} debugging.
7531 Same as @samp{tfind none}.
7534 No argument means find the next trace snapshot.
7537 Find the previous trace snapshot before the current one. This permits
7538 retracing earlier steps.
7540 @item tfind tracepoint @var{num}
7541 Find the next snapshot associated with tracepoint @var{num}. Search
7542 proceeds forward from the last examined trace snapshot. If no
7543 argument @var{num} is given, it means find the next snapshot collected
7544 for the same tracepoint as the current snapshot.
7546 @item tfind pc @var{addr}
7547 Find the next snapshot associated with the value @var{addr} of the
7548 program counter. Search proceeds forward from the last examined trace
7549 snapshot. If no argument @var{addr} is given, it means find the next
7550 snapshot with the same value of PC as the current snapshot.
7552 @item tfind outside @var{addr1}, @var{addr2}
7553 Find the next snapshot whose PC is outside the given range of
7556 @item tfind range @var{addr1}, @var{addr2}
7557 Find the next snapshot whose PC is between @var{addr1} and
7558 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
7560 @item tfind line @r{[}@var{file}:@r{]}@var{n}
7561 Find the next snapshot associated with the source line @var{n}. If
7562 the optional argument @var{file} is given, refer to line @var{n} in
7563 that source file. Search proceeds forward from the last examined
7564 trace snapshot. If no argument @var{n} is given, it means find the
7565 next line other than the one currently being examined; thus saying
7566 @code{tfind line} repeatedly can appear to have the same effect as
7567 stepping from line to line in a @emph{live} debugging session.
7570 The default arguments for the @code{tfind} commands are specifically
7571 designed to make it easy to scan through the trace buffer. For
7572 instance, @code{tfind} with no argument selects the next trace
7573 snapshot, and @code{tfind -} with no argument selects the previous
7574 trace snapshot. So, by giving one @code{tfind} command, and then
7575 simply hitting @key{RET} repeatedly you can examine all the trace
7576 snapshots in order. Or, by saying @code{tfind -} and then hitting
7577 @key{RET} repeatedly you can examine the snapshots in reverse order.
7578 The @code{tfind line} command with no argument selects the snapshot
7579 for the next source line executed. The @code{tfind pc} command with
7580 no argument selects the next snapshot with the same program counter
7581 (PC) as the current frame. The @code{tfind tracepoint} command with
7582 no argument selects the next trace snapshot collected by the same
7583 tracepoint as the current one.
7585 In addition to letting you scan through the trace buffer manually,
7586 these commands make it easy to construct @value{GDBN} scripts that
7587 scan through the trace buffer and print out whatever collected data
7588 you are interested in. Thus, if we want to examine the PC, FP, and SP
7589 registers from each trace frame in the buffer, we can say this:
7592 (@value{GDBP}) @b{tfind start}
7593 (@value{GDBP}) @b{while ($trace_frame != -1)}
7594 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
7595 $trace_frame, $pc, $sp, $fp
7599 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
7600 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
7601 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
7602 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
7603 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
7604 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
7605 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
7606 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
7607 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
7608 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
7609 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
7612 Or, if we want to examine the variable @code{X} at each source line in
7616 (@value{GDBP}) @b{tfind start}
7617 (@value{GDBP}) @b{while ($trace_frame != -1)}
7618 > printf "Frame %d, X == %d\n", $trace_frame, X
7628 @subsection @code{tdump}
7630 @cindex dump all data collected at tracepoint
7631 @cindex tracepoint data, display
7633 This command takes no arguments. It prints all the data collected at
7634 the current trace snapshot.
7637 (@value{GDBP}) @b{trace 444}
7638 (@value{GDBP}) @b{actions}
7639 Enter actions for tracepoint #2, one per line:
7640 > collect $regs, $locals, $args, gdb_long_test
7643 (@value{GDBP}) @b{tstart}
7645 (@value{GDBP}) @b{tfind line 444}
7646 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
7648 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
7650 (@value{GDBP}) @b{tdump}
7651 Data collected at tracepoint 2, trace frame 1:
7652 d0 0xc4aa0085 -995491707
7656 d4 0x71aea3d 119204413
7661 a1 0x3000668 50333288
7664 a4 0x3000698 50333336
7666 fp 0x30bf3c 0x30bf3c
7667 sp 0x30bf34 0x30bf34
7669 pc 0x20b2c8 0x20b2c8
7673 p = 0x20e5b4 "gdb-test"
7680 gdb_long_test = 17 '\021'
7685 @node save-tracepoints
7686 @subsection @code{save-tracepoints @var{filename}}
7687 @kindex save-tracepoints
7688 @cindex save tracepoints for future sessions
7690 This command saves all current tracepoint definitions together with
7691 their actions and passcounts, into a file @file{@var{filename}}
7692 suitable for use in a later debugging session. To read the saved
7693 tracepoint definitions, use the @code{source} command (@pxref{Command
7696 @node Tracepoint Variables
7697 @section Convenience Variables for Tracepoints
7698 @cindex tracepoint variables
7699 @cindex convenience variables for tracepoints
7702 @vindex $trace_frame
7703 @item (int) $trace_frame
7704 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
7705 snapshot is selected.
7708 @item (int) $tracepoint
7709 The tracepoint for the current trace snapshot.
7712 @item (int) $trace_line
7713 The line number for the current trace snapshot.
7716 @item (char []) $trace_file
7717 The source file for the current trace snapshot.
7720 @item (char []) $trace_func
7721 The name of the function containing @code{$tracepoint}.
7724 Note: @code{$trace_file} is not suitable for use in @code{printf},
7725 use @code{output} instead.
7727 Here's a simple example of using these convenience variables for
7728 stepping through all the trace snapshots and printing some of their
7732 (@value{GDBP}) @b{tfind start}
7734 (@value{GDBP}) @b{while $trace_frame != -1}
7735 > output $trace_file
7736 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
7742 @chapter Debugging Programs That Use Overlays
7745 If your program is too large to fit completely in your target system's
7746 memory, you can sometimes use @dfn{overlays} to work around this
7747 problem. @value{GDBN} provides some support for debugging programs that
7751 * How Overlays Work:: A general explanation of overlays.
7752 * Overlay Commands:: Managing overlays in @value{GDBN}.
7753 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
7754 mapped by asking the inferior.
7755 * Overlay Sample Program:: A sample program using overlays.
7758 @node How Overlays Work
7759 @section How Overlays Work
7760 @cindex mapped overlays
7761 @cindex unmapped overlays
7762 @cindex load address, overlay's
7763 @cindex mapped address
7764 @cindex overlay area
7766 Suppose you have a computer whose instruction address space is only 64
7767 kilobytes long, but which has much more memory which can be accessed by
7768 other means: special instructions, segment registers, or memory
7769 management hardware, for example. Suppose further that you want to
7770 adapt a program which is larger than 64 kilobytes to run on this system.
7772 One solution is to identify modules of your program which are relatively
7773 independent, and need not call each other directly; call these modules
7774 @dfn{overlays}. Separate the overlays from the main program, and place
7775 their machine code in the larger memory. Place your main program in
7776 instruction memory, but leave at least enough space there to hold the
7777 largest overlay as well.
7779 Now, to call a function located in an overlay, you must first copy that
7780 overlay's machine code from the large memory into the space set aside
7781 for it in the instruction memory, and then jump to its entry point
7784 @c NB: In the below the mapped area's size is greater or equal to the
7785 @c size of all overlays. This is intentional to remind the developer
7786 @c that overlays don't necessarily need to be the same size.
7790 Data Instruction Larger
7791 Address Space Address Space Address Space
7792 +-----------+ +-----------+ +-----------+
7794 +-----------+ +-----------+ +-----------+<-- overlay 1
7795 | program | | main | .----| overlay 1 | load address
7796 | variables | | program | | +-----------+
7797 | and heap | | | | | |
7798 +-----------+ | | | +-----------+<-- overlay 2
7799 | | +-----------+ | | | load address
7800 +-----------+ | | | .-| overlay 2 |
7802 mapped --->+-----------+ | | +-----------+
7804 | overlay | <-' | | |
7805 | area | <---' +-----------+<-- overlay 3
7806 | | <---. | | load address
7807 +-----------+ `--| overlay 3 |
7814 @anchor{A code overlay}A code overlay
7818 The diagram (@pxref{A code overlay}) shows a system with separate data
7819 and instruction address spaces. To map an overlay, the program copies
7820 its code from the larger address space to the instruction address space.
7821 Since the overlays shown here all use the same mapped address, only one
7822 may be mapped at a time. For a system with a single address space for
7823 data and instructions, the diagram would be similar, except that the
7824 program variables and heap would share an address space with the main
7825 program and the overlay area.
7827 An overlay loaded into instruction memory and ready for use is called a
7828 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
7829 instruction memory. An overlay not present (or only partially present)
7830 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
7831 is its address in the larger memory. The mapped address is also called
7832 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
7833 called the @dfn{load memory address}, or @dfn{LMA}.
7835 Unfortunately, overlays are not a completely transparent way to adapt a
7836 program to limited instruction memory. They introduce a new set of
7837 global constraints you must keep in mind as you design your program:
7842 Before calling or returning to a function in an overlay, your program
7843 must make sure that overlay is actually mapped. Otherwise, the call or
7844 return will transfer control to the right address, but in the wrong
7845 overlay, and your program will probably crash.
7848 If the process of mapping an overlay is expensive on your system, you
7849 will need to choose your overlays carefully to minimize their effect on
7850 your program's performance.
7853 The executable file you load onto your system must contain each
7854 overlay's instructions, appearing at the overlay's load address, not its
7855 mapped address. However, each overlay's instructions must be relocated
7856 and its symbols defined as if the overlay were at its mapped address.
7857 You can use GNU linker scripts to specify different load and relocation
7858 addresses for pieces of your program; see @ref{Overlay Description,,,
7859 ld.info, Using ld: the GNU linker}.
7862 The procedure for loading executable files onto your system must be able
7863 to load their contents into the larger address space as well as the
7864 instruction and data spaces.
7868 The overlay system described above is rather simple, and could be
7869 improved in many ways:
7874 If your system has suitable bank switch registers or memory management
7875 hardware, you could use those facilities to make an overlay's load area
7876 contents simply appear at their mapped address in instruction space.
7877 This would probably be faster than copying the overlay to its mapped
7878 area in the usual way.
7881 If your overlays are small enough, you could set aside more than one
7882 overlay area, and have more than one overlay mapped at a time.
7885 You can use overlays to manage data, as well as instructions. In
7886 general, data overlays are even less transparent to your design than
7887 code overlays: whereas code overlays only require care when you call or
7888 return to functions, data overlays require care every time you access
7889 the data. Also, if you change the contents of a data overlay, you
7890 must copy its contents back out to its load address before you can copy a
7891 different data overlay into the same mapped area.
7896 @node Overlay Commands
7897 @section Overlay Commands
7899 To use @value{GDBN}'s overlay support, each overlay in your program must
7900 correspond to a separate section of the executable file. The section's
7901 virtual memory address and load memory address must be the overlay's
7902 mapped and load addresses. Identifying overlays with sections allows
7903 @value{GDBN} to determine the appropriate address of a function or
7904 variable, depending on whether the overlay is mapped or not.
7906 @value{GDBN}'s overlay commands all start with the word @code{overlay};
7907 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
7912 Disable @value{GDBN}'s overlay support. When overlay support is
7913 disabled, @value{GDBN} assumes that all functions and variables are
7914 always present at their mapped addresses. By default, @value{GDBN}'s
7915 overlay support is disabled.
7917 @item overlay manual
7918 @cindex manual overlay debugging
7919 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
7920 relies on you to tell it which overlays are mapped, and which are not,
7921 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
7922 commands described below.
7924 @item overlay map-overlay @var{overlay}
7925 @itemx overlay map @var{overlay}
7926 @cindex map an overlay
7927 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
7928 be the name of the object file section containing the overlay. When an
7929 overlay is mapped, @value{GDBN} assumes it can find the overlay's
7930 functions and variables at their mapped addresses. @value{GDBN} assumes
7931 that any other overlays whose mapped ranges overlap that of
7932 @var{overlay} are now unmapped.
7934 @item overlay unmap-overlay @var{overlay}
7935 @itemx overlay unmap @var{overlay}
7936 @cindex unmap an overlay
7937 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
7938 must be the name of the object file section containing the overlay.
7939 When an overlay is unmapped, @value{GDBN} assumes it can find the
7940 overlay's functions and variables at their load addresses.
7943 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
7944 consults a data structure the overlay manager maintains in the inferior
7945 to see which overlays are mapped. For details, see @ref{Automatic
7948 @item overlay load-target
7950 @cindex reloading the overlay table
7951 Re-read the overlay table from the inferior. Normally, @value{GDBN}
7952 re-reads the table @value{GDBN} automatically each time the inferior
7953 stops, so this command should only be necessary if you have changed the
7954 overlay mapping yourself using @value{GDBN}. This command is only
7955 useful when using automatic overlay debugging.
7957 @item overlay list-overlays
7959 @cindex listing mapped overlays
7960 Display a list of the overlays currently mapped, along with their mapped
7961 addresses, load addresses, and sizes.
7965 Normally, when @value{GDBN} prints a code address, it includes the name
7966 of the function the address falls in:
7969 (@value{GDBP}) print main
7970 $3 = @{int ()@} 0x11a0 <main>
7973 When overlay debugging is enabled, @value{GDBN} recognizes code in
7974 unmapped overlays, and prints the names of unmapped functions with
7975 asterisks around them. For example, if @code{foo} is a function in an
7976 unmapped overlay, @value{GDBN} prints it this way:
7979 (@value{GDBP}) overlay list
7980 No sections are mapped.
7981 (@value{GDBP}) print foo
7982 $5 = @{int (int)@} 0x100000 <*foo*>
7985 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
7989 (@value{GDBP}) overlay list
7990 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
7991 mapped at 0x1016 - 0x104a
7992 (@value{GDBP}) print foo
7993 $6 = @{int (int)@} 0x1016 <foo>
7996 When overlay debugging is enabled, @value{GDBN} can find the correct
7997 address for functions and variables in an overlay, whether or not the
7998 overlay is mapped. This allows most @value{GDBN} commands, like
7999 @code{break} and @code{disassemble}, to work normally, even on unmapped
8000 code. However, @value{GDBN}'s breakpoint support has some limitations:
8004 @cindex breakpoints in overlays
8005 @cindex overlays, setting breakpoints in
8006 You can set breakpoints in functions in unmapped overlays, as long as
8007 @value{GDBN} can write to the overlay at its load address.
8009 @value{GDBN} can not set hardware or simulator-based breakpoints in
8010 unmapped overlays. However, if you set a breakpoint at the end of your
8011 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
8012 you are using manual overlay management), @value{GDBN} will re-set its
8013 breakpoints properly.
8017 @node Automatic Overlay Debugging
8018 @section Automatic Overlay Debugging
8019 @cindex automatic overlay debugging
8021 @value{GDBN} can automatically track which overlays are mapped and which
8022 are not, given some simple co-operation from the overlay manager in the
8023 inferior. If you enable automatic overlay debugging with the
8024 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
8025 looks in the inferior's memory for certain variables describing the
8026 current state of the overlays.
8028 Here are the variables your overlay manager must define to support
8029 @value{GDBN}'s automatic overlay debugging:
8033 @item @code{_ovly_table}:
8034 This variable must be an array of the following structures:
8039 /* The overlay's mapped address. */
8042 /* The size of the overlay, in bytes. */
8045 /* The overlay's load address. */
8048 /* Non-zero if the overlay is currently mapped;
8050 unsigned long mapped;
8054 @item @code{_novlys}:
8055 This variable must be a four-byte signed integer, holding the total
8056 number of elements in @code{_ovly_table}.
8060 To decide whether a particular overlay is mapped or not, @value{GDBN}
8061 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
8062 @code{lma} members equal the VMA and LMA of the overlay's section in the
8063 executable file. When @value{GDBN} finds a matching entry, it consults
8064 the entry's @code{mapped} member to determine whether the overlay is
8067 In addition, your overlay manager may define a function called
8068 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
8069 will silently set a breakpoint there. If the overlay manager then
8070 calls this function whenever it has changed the overlay table, this
8071 will enable @value{GDBN} to accurately keep track of which overlays
8072 are in program memory, and update any breakpoints that may be set
8073 in overlays. This will allow breakpoints to work even if the
8074 overlays are kept in ROM or other non-writable memory while they
8075 are not being executed.
8077 @node Overlay Sample Program
8078 @section Overlay Sample Program
8079 @cindex overlay example program
8081 When linking a program which uses overlays, you must place the overlays
8082 at their load addresses, while relocating them to run at their mapped
8083 addresses. To do this, you must write a linker script (@pxref{Overlay
8084 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
8085 since linker scripts are specific to a particular host system, target
8086 architecture, and target memory layout, this manual cannot provide
8087 portable sample code demonstrating @value{GDBN}'s overlay support.
8089 However, the @value{GDBN} source distribution does contain an overlaid
8090 program, with linker scripts for a few systems, as part of its test
8091 suite. The program consists of the following files from
8092 @file{gdb/testsuite/gdb.base}:
8096 The main program file.
8098 A simple overlay manager, used by @file{overlays.c}.
8103 Overlay modules, loaded and used by @file{overlays.c}.
8106 Linker scripts for linking the test program on the @code{d10v-elf}
8107 and @code{m32r-elf} targets.
8110 You can build the test program using the @code{d10v-elf} GCC
8111 cross-compiler like this:
8114 $ d10v-elf-gcc -g -c overlays.c
8115 $ d10v-elf-gcc -g -c ovlymgr.c
8116 $ d10v-elf-gcc -g -c foo.c
8117 $ d10v-elf-gcc -g -c bar.c
8118 $ d10v-elf-gcc -g -c baz.c
8119 $ d10v-elf-gcc -g -c grbx.c
8120 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
8121 baz.o grbx.o -Wl,-Td10v.ld -o overlays
8124 The build process is identical for any other architecture, except that
8125 you must substitute the appropriate compiler and linker script for the
8126 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
8130 @chapter Using @value{GDBN} with Different Languages
8133 Although programming languages generally have common aspects, they are
8134 rarely expressed in the same manner. For instance, in ANSI C,
8135 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
8136 Modula-2, it is accomplished by @code{p^}. Values can also be
8137 represented (and displayed) differently. Hex numbers in C appear as
8138 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
8140 @cindex working language
8141 Language-specific information is built into @value{GDBN} for some languages,
8142 allowing you to express operations like the above in your program's
8143 native language, and allowing @value{GDBN} to output values in a manner
8144 consistent with the syntax of your program's native language. The
8145 language you use to build expressions is called the @dfn{working
8149 * Setting:: Switching between source languages
8150 * Show:: Displaying the language
8151 * Checks:: Type and range checks
8152 * Supported languages:: Supported languages
8153 * Unsupported languages:: Unsupported languages
8157 @section Switching between source languages
8159 There are two ways to control the working language---either have @value{GDBN}
8160 set it automatically, or select it manually yourself. You can use the
8161 @code{set language} command for either purpose. On startup, @value{GDBN}
8162 defaults to setting the language automatically. The working language is
8163 used to determine how expressions you type are interpreted, how values
8166 In addition to the working language, every source file that
8167 @value{GDBN} knows about has its own working language. For some object
8168 file formats, the compiler might indicate which language a particular
8169 source file is in. However, most of the time @value{GDBN} infers the
8170 language from the name of the file. The language of a source file
8171 controls whether C@t{++} names are demangled---this way @code{backtrace} can
8172 show each frame appropriately for its own language. There is no way to
8173 set the language of a source file from within @value{GDBN}, but you can
8174 set the language associated with a filename extension. @xref{Show, ,
8175 Displaying the language}.
8177 This is most commonly a problem when you use a program, such
8178 as @code{cfront} or @code{f2c}, that generates C but is written in
8179 another language. In that case, make the
8180 program use @code{#line} directives in its C output; that way
8181 @value{GDBN} will know the correct language of the source code of the original
8182 program, and will display that source code, not the generated C code.
8185 * Filenames:: Filename extensions and languages.
8186 * Manually:: Setting the working language manually
8187 * Automatically:: Having @value{GDBN} infer the source language
8191 @subsection List of filename extensions and languages
8193 If a source file name ends in one of the following extensions, then
8194 @value{GDBN} infers that its language is the one indicated.
8215 Objective-C source file
8222 Modula-2 source file
8226 Assembler source file. This actually behaves almost like C, but
8227 @value{GDBN} does not skip over function prologues when stepping.
8230 In addition, you may set the language associated with a filename
8231 extension. @xref{Show, , Displaying the language}.
8234 @subsection Setting the working language
8236 If you allow @value{GDBN} to set the language automatically,
8237 expressions are interpreted the same way in your debugging session and
8240 @kindex set language
8241 If you wish, you may set the language manually. To do this, issue the
8242 command @samp{set language @var{lang}}, where @var{lang} is the name of
8244 @code{c} or @code{modula-2}.
8245 For a list of the supported languages, type @samp{set language}.
8247 Setting the language manually prevents @value{GDBN} from updating the working
8248 language automatically. This can lead to confusion if you try
8249 to debug a program when the working language is not the same as the
8250 source language, when an expression is acceptable to both
8251 languages---but means different things. For instance, if the current
8252 source file were written in C, and @value{GDBN} was parsing Modula-2, a
8260 might not have the effect you intended. In C, this means to add
8261 @code{b} and @code{c} and place the result in @code{a}. The result
8262 printed would be the value of @code{a}. In Modula-2, this means to compare
8263 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
8266 @subsection Having @value{GDBN} infer the source language
8268 To have @value{GDBN} set the working language automatically, use
8269 @samp{set language local} or @samp{set language auto}. @value{GDBN}
8270 then infers the working language. That is, when your program stops in a
8271 frame (usually by encountering a breakpoint), @value{GDBN} sets the
8272 working language to the language recorded for the function in that
8273 frame. If the language for a frame is unknown (that is, if the function
8274 or block corresponding to the frame was defined in a source file that
8275 does not have a recognized extension), the current working language is
8276 not changed, and @value{GDBN} issues a warning.
8278 This may not seem necessary for most programs, which are written
8279 entirely in one source language. However, program modules and libraries
8280 written in one source language can be used by a main program written in
8281 a different source language. Using @samp{set language auto} in this
8282 case frees you from having to set the working language manually.
8285 @section Displaying the language
8287 The following commands help you find out which language is the
8288 working language, and also what language source files were written in.
8292 @kindex show language
8293 Display the current working language. This is the
8294 language you can use with commands such as @code{print} to
8295 build and compute expressions that may involve variables in your program.
8298 @kindex info frame@r{, show the source language}
8299 Display the source language for this frame. This language becomes the
8300 working language if you use an identifier from this frame.
8301 @xref{Frame Info, ,Information about a frame}, to identify the other
8302 information listed here.
8305 @kindex info source@r{, show the source language}
8306 Display the source language of this source file.
8307 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
8308 information listed here.
8311 In unusual circumstances, you may have source files with extensions
8312 not in the standard list. You can then set the extension associated
8313 with a language explicitly:
8316 @item set extension-language @var{ext} @var{language}
8317 @kindex set extension-language
8318 Tell @value{GDBN} that source files with extension @var{ext} are to be
8319 assumed as written in the source language @var{language}.
8321 @item info extensions
8322 @kindex info extensions
8323 List all the filename extensions and the associated languages.
8327 @section Type and range checking
8330 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
8331 checking are included, but they do not yet have any effect. This
8332 section documents the intended facilities.
8334 @c FIXME remove warning when type/range code added
8336 Some languages are designed to guard you against making seemingly common
8337 errors through a series of compile- and run-time checks. These include
8338 checking the type of arguments to functions and operators, and making
8339 sure mathematical overflows are caught at run time. Checks such as
8340 these help to ensure a program's correctness once it has been compiled
8341 by eliminating type mismatches, and providing active checks for range
8342 errors when your program is running.
8344 @value{GDBN} can check for conditions like the above if you wish.
8345 Although @value{GDBN} does not check the statements in your program,
8346 it can check expressions entered directly into @value{GDBN} for
8347 evaluation via the @code{print} command, for example. As with the
8348 working language, @value{GDBN} can also decide whether or not to check
8349 automatically based on your program's source language.
8350 @xref{Supported languages, ,Supported languages}, for the default
8351 settings of supported languages.
8354 * Type Checking:: An overview of type checking
8355 * Range Checking:: An overview of range checking
8358 @cindex type checking
8359 @cindex checks, type
8361 @subsection An overview of type checking
8363 Some languages, such as Modula-2, are strongly typed, meaning that the
8364 arguments to operators and functions have to be of the correct type,
8365 otherwise an error occurs. These checks prevent type mismatch
8366 errors from ever causing any run-time problems. For example,
8374 The second example fails because the @code{CARDINAL} 1 is not
8375 type-compatible with the @code{REAL} 2.3.
8377 For the expressions you use in @value{GDBN} commands, you can tell the
8378 @value{GDBN} type checker to skip checking;
8379 to treat any mismatches as errors and abandon the expression;
8380 or to only issue warnings when type mismatches occur,
8381 but evaluate the expression anyway. When you choose the last of
8382 these, @value{GDBN} evaluates expressions like the second example above, but
8383 also issues a warning.
8385 Even if you turn type checking off, there may be other reasons
8386 related to type that prevent @value{GDBN} from evaluating an expression.
8387 For instance, @value{GDBN} does not know how to add an @code{int} and
8388 a @code{struct foo}. These particular type errors have nothing to do
8389 with the language in use, and usually arise from expressions, such as
8390 the one described above, which make little sense to evaluate anyway.
8392 Each language defines to what degree it is strict about type. For
8393 instance, both Modula-2 and C require the arguments to arithmetical
8394 operators to be numbers. In C, enumerated types and pointers can be
8395 represented as numbers, so that they are valid arguments to mathematical
8396 operators. @xref{Supported languages, ,Supported languages}, for further
8397 details on specific languages.
8399 @value{GDBN} provides some additional commands for controlling the type checker:
8401 @kindex set check type
8402 @kindex show check type
8404 @item set check type auto
8405 Set type checking on or off based on the current working language.
8406 @xref{Supported languages, ,Supported languages}, for the default settings for
8409 @item set check type on
8410 @itemx set check type off
8411 Set type checking on or off, overriding the default setting for the
8412 current working language. Issue a warning if the setting does not
8413 match the language default. If any type mismatches occur in
8414 evaluating an expression while type checking is on, @value{GDBN} prints a
8415 message and aborts evaluation of the expression.
8417 @item set check type warn
8418 Cause the type checker to issue warnings, but to always attempt to
8419 evaluate the expression. Evaluating the expression may still
8420 be impossible for other reasons. For example, @value{GDBN} cannot add
8421 numbers and structures.
8424 Show the current setting of the type checker, and whether or not @value{GDBN}
8425 is setting it automatically.
8428 @cindex range checking
8429 @cindex checks, range
8430 @node Range Checking
8431 @subsection An overview of range checking
8433 In some languages (such as Modula-2), it is an error to exceed the
8434 bounds of a type; this is enforced with run-time checks. Such range
8435 checking is meant to ensure program correctness by making sure
8436 computations do not overflow, or indices on an array element access do
8437 not exceed the bounds of the array.
8439 For expressions you use in @value{GDBN} commands, you can tell
8440 @value{GDBN} to treat range errors in one of three ways: ignore them,
8441 always treat them as errors and abandon the expression, or issue
8442 warnings but evaluate the expression anyway.
8444 A range error can result from numerical overflow, from exceeding an
8445 array index bound, or when you type a constant that is not a member
8446 of any type. Some languages, however, do not treat overflows as an
8447 error. In many implementations of C, mathematical overflow causes the
8448 result to ``wrap around'' to lower values---for example, if @var{m} is
8449 the largest integer value, and @var{s} is the smallest, then
8452 @var{m} + 1 @result{} @var{s}
8455 This, too, is specific to individual languages, and in some cases
8456 specific to individual compilers or machines. @xref{Supported languages, ,
8457 Supported languages}, for further details on specific languages.
8459 @value{GDBN} provides some additional commands for controlling the range checker:
8461 @kindex set check range
8462 @kindex show check range
8464 @item set check range auto
8465 Set range checking on or off based on the current working language.
8466 @xref{Supported languages, ,Supported languages}, for the default settings for
8469 @item set check range on
8470 @itemx set check range off
8471 Set range checking on or off, overriding the default setting for the
8472 current working language. A warning is issued if the setting does not
8473 match the language default. If a range error occurs and range checking is on,
8474 then a message is printed and evaluation of the expression is aborted.
8476 @item set check range warn
8477 Output messages when the @value{GDBN} range checker detects a range error,
8478 but attempt to evaluate the expression anyway. Evaluating the
8479 expression may still be impossible for other reasons, such as accessing
8480 memory that the process does not own (a typical example from many Unix
8484 Show the current setting of the range checker, and whether or not it is
8485 being set automatically by @value{GDBN}.
8488 @node Supported languages
8489 @section Supported languages
8491 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
8492 assembly, Modula-2, and Ada.
8493 @c This is false ...
8494 Some @value{GDBN} features may be used in expressions regardless of the
8495 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
8496 and the @samp{@{type@}addr} construct (@pxref{Expressions,
8497 ,Expressions}) can be used with the constructs of any supported
8500 The following sections detail to what degree each source language is
8501 supported by @value{GDBN}. These sections are not meant to be language
8502 tutorials or references, but serve only as a reference guide to what the
8503 @value{GDBN} expression parser accepts, and what input and output
8504 formats should look like for different languages. There are many good
8505 books written on each of these languages; please look to these for a
8506 language reference or tutorial.
8510 * Objective-C:: Objective-C
8513 * Modula-2:: Modula-2
8518 @subsection C and C@t{++}
8520 @cindex C and C@t{++}
8521 @cindex expressions in C or C@t{++}
8523 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
8524 to both languages. Whenever this is the case, we discuss those languages
8528 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
8529 @cindex @sc{gnu} C@t{++}
8530 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
8531 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
8532 effectively, you must compile your C@t{++} programs with a supported
8533 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
8534 compiler (@code{aCC}).
8536 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
8537 format; if it doesn't work on your system, try the stabs+ debugging
8538 format. You can select those formats explicitly with the @code{g++}
8539 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
8540 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
8541 CC, gcc.info, Using @sc{gnu} CC}.
8544 * C Operators:: C and C@t{++} operators
8545 * C Constants:: C and C@t{++} constants
8546 * C plus plus expressions:: C@t{++} expressions
8547 * C Defaults:: Default settings for C and C@t{++}
8548 * C Checks:: C and C@t{++} type and range checks
8549 * Debugging C:: @value{GDBN} and C
8550 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
8554 @subsubsection C and C@t{++} operators
8556 @cindex C and C@t{++} operators
8558 Operators must be defined on values of specific types. For instance,
8559 @code{+} is defined on numbers, but not on structures. Operators are
8560 often defined on groups of types.
8562 For the purposes of C and C@t{++}, the following definitions hold:
8567 @emph{Integral types} include @code{int} with any of its storage-class
8568 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
8571 @emph{Floating-point types} include @code{float}, @code{double}, and
8572 @code{long double} (if supported by the target platform).
8575 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
8578 @emph{Scalar types} include all of the above.
8583 The following operators are supported. They are listed here
8584 in order of increasing precedence:
8588 The comma or sequencing operator. Expressions in a comma-separated list
8589 are evaluated from left to right, with the result of the entire
8590 expression being the last expression evaluated.
8593 Assignment. The value of an assignment expression is the value
8594 assigned. Defined on scalar types.
8597 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
8598 and translated to @w{@code{@var{a} = @var{a op b}}}.
8599 @w{@code{@var{op}=}} and @code{=} have the same precedence.
8600 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
8601 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
8604 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
8605 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
8609 Logical @sc{or}. Defined on integral types.
8612 Logical @sc{and}. Defined on integral types.
8615 Bitwise @sc{or}. Defined on integral types.
8618 Bitwise exclusive-@sc{or}. Defined on integral types.
8621 Bitwise @sc{and}. Defined on integral types.
8624 Equality and inequality. Defined on scalar types. The value of these
8625 expressions is 0 for false and non-zero for true.
8627 @item <@r{, }>@r{, }<=@r{, }>=
8628 Less than, greater than, less than or equal, greater than or equal.
8629 Defined on scalar types. The value of these expressions is 0 for false
8630 and non-zero for true.
8633 left shift, and right shift. Defined on integral types.
8636 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8639 Addition and subtraction. Defined on integral types, floating-point types and
8642 @item *@r{, }/@r{, }%
8643 Multiplication, division, and modulus. Multiplication and division are
8644 defined on integral and floating-point types. Modulus is defined on
8648 Increment and decrement. When appearing before a variable, the
8649 operation is performed before the variable is used in an expression;
8650 when appearing after it, the variable's value is used before the
8651 operation takes place.
8654 Pointer dereferencing. Defined on pointer types. Same precedence as
8658 Address operator. Defined on variables. Same precedence as @code{++}.
8660 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
8661 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
8662 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
8663 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
8667 Negative. Defined on integral and floating-point types. Same
8668 precedence as @code{++}.
8671 Logical negation. Defined on integral types. Same precedence as
8675 Bitwise complement operator. Defined on integral types. Same precedence as
8680 Structure member, and pointer-to-structure member. For convenience,
8681 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
8682 pointer based on the stored type information.
8683 Defined on @code{struct} and @code{union} data.
8686 Dereferences of pointers to members.
8689 Array indexing. @code{@var{a}[@var{i}]} is defined as
8690 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
8693 Function parameter list. Same precedence as @code{->}.
8696 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
8697 and @code{class} types.
8700 Doubled colons also represent the @value{GDBN} scope operator
8701 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
8705 If an operator is redefined in the user code, @value{GDBN} usually
8706 attempts to invoke the redefined version instead of using the operator's
8714 @subsubsection C and C@t{++} constants
8716 @cindex C and C@t{++} constants
8718 @value{GDBN} allows you to express the constants of C and C@t{++} in the
8723 Integer constants are a sequence of digits. Octal constants are
8724 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
8725 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
8726 @samp{l}, specifying that the constant should be treated as a
8730 Floating point constants are a sequence of digits, followed by a decimal
8731 point, followed by a sequence of digits, and optionally followed by an
8732 exponent. An exponent is of the form:
8733 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
8734 sequence of digits. The @samp{+} is optional for positive exponents.
8735 A floating-point constant may also end with a letter @samp{f} or
8736 @samp{F}, specifying that the constant should be treated as being of
8737 the @code{float} (as opposed to the default @code{double}) type; or with
8738 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
8742 Enumerated constants consist of enumerated identifiers, or their
8743 integral equivalents.
8746 Character constants are a single character surrounded by single quotes
8747 (@code{'}), or a number---the ordinal value of the corresponding character
8748 (usually its @sc{ascii} value). Within quotes, the single character may
8749 be represented by a letter or by @dfn{escape sequences}, which are of
8750 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
8751 of the character's ordinal value; or of the form @samp{\@var{x}}, where
8752 @samp{@var{x}} is a predefined special character---for example,
8753 @samp{\n} for newline.
8756 String constants are a sequence of character constants surrounded by
8757 double quotes (@code{"}). Any valid character constant (as described
8758 above) may appear. Double quotes within the string must be preceded by
8759 a backslash, so for instance @samp{"a\"b'c"} is a string of five
8763 Pointer constants are an integral value. You can also write pointers
8764 to constants using the C operator @samp{&}.
8767 Array constants are comma-separated lists surrounded by braces @samp{@{}
8768 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
8769 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
8770 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
8774 * C plus plus expressions::
8781 @node C plus plus expressions
8782 @subsubsection C@t{++} expressions
8784 @cindex expressions in C@t{++}
8785 @value{GDBN} expression handling can interpret most C@t{++} expressions.
8787 @cindex debugging C@t{++} programs
8788 @cindex C@t{++} compilers
8789 @cindex debug formats and C@t{++}
8790 @cindex @value{NGCC} and C@t{++}
8792 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
8793 proper compiler and the proper debug format. Currently, @value{GDBN}
8794 works best when debugging C@t{++} code that is compiled with
8795 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
8796 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
8797 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
8798 stabs+ as their default debug format, so you usually don't need to
8799 specify a debug format explicitly. Other compilers and/or debug formats
8800 are likely to work badly or not at all when using @value{GDBN} to debug
8806 @cindex member functions
8808 Member function calls are allowed; you can use expressions like
8811 count = aml->GetOriginal(x, y)
8814 @vindex this@r{, inside C@t{++} member functions}
8815 @cindex namespace in C@t{++}
8817 While a member function is active (in the selected stack frame), your
8818 expressions have the same namespace available as the member function;
8819 that is, @value{GDBN} allows implicit references to the class instance
8820 pointer @code{this} following the same rules as C@t{++}.
8822 @cindex call overloaded functions
8823 @cindex overloaded functions, calling
8824 @cindex type conversions in C@t{++}
8826 You can call overloaded functions; @value{GDBN} resolves the function
8827 call to the right definition, with some restrictions. @value{GDBN} does not
8828 perform overload resolution involving user-defined type conversions,
8829 calls to constructors, or instantiations of templates that do not exist
8830 in the program. It also cannot handle ellipsis argument lists or
8833 It does perform integral conversions and promotions, floating-point
8834 promotions, arithmetic conversions, pointer conversions, conversions of
8835 class objects to base classes, and standard conversions such as those of
8836 functions or arrays to pointers; it requires an exact match on the
8837 number of function arguments.
8839 Overload resolution is always performed, unless you have specified
8840 @code{set overload-resolution off}. @xref{Debugging C plus plus,
8841 ,@value{GDBN} features for C@t{++}}.
8843 You must specify @code{set overload-resolution off} in order to use an
8844 explicit function signature to call an overloaded function, as in
8846 p 'foo(char,int)'('x', 13)
8849 The @value{GDBN} command-completion facility can simplify this;
8850 see @ref{Completion, ,Command completion}.
8852 @cindex reference declarations
8854 @value{GDBN} understands variables declared as C@t{++} references; you can use
8855 them in expressions just as you do in C@t{++} source---they are automatically
8858 In the parameter list shown when @value{GDBN} displays a frame, the values of
8859 reference variables are not displayed (unlike other variables); this
8860 avoids clutter, since references are often used for large structures.
8861 The @emph{address} of a reference variable is always shown, unless
8862 you have specified @samp{set print address off}.
8865 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
8866 expressions can use it just as expressions in your program do. Since
8867 one scope may be defined in another, you can use @code{::} repeatedly if
8868 necessary, for example in an expression like
8869 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
8870 resolving name scope by reference to source files, in both C and C@t{++}
8871 debugging (@pxref{Variables, ,Program variables}).
8874 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
8875 calling virtual functions correctly, printing out virtual bases of
8876 objects, calling functions in a base subobject, casting objects, and
8877 invoking user-defined operators.
8880 @subsubsection C and C@t{++} defaults
8882 @cindex C and C@t{++} defaults
8884 If you allow @value{GDBN} to set type and range checking automatically, they
8885 both default to @code{off} whenever the working language changes to
8886 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
8887 selects the working language.
8889 If you allow @value{GDBN} to set the language automatically, it
8890 recognizes source files whose names end with @file{.c}, @file{.C}, or
8891 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
8892 these files, it sets the working language to C or C@t{++}.
8893 @xref{Automatically, ,Having @value{GDBN} infer the source language},
8894 for further details.
8896 @c Type checking is (a) primarily motivated by Modula-2, and (b)
8897 @c unimplemented. If (b) changes, it might make sense to let this node
8898 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
8901 @subsubsection C and C@t{++} type and range checks
8903 @cindex C and C@t{++} checks
8905 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
8906 is not used. However, if you turn type checking on, @value{GDBN}
8907 considers two variables type equivalent if:
8911 The two variables are structured and have the same structure, union, or
8915 The two variables have the same type name, or types that have been
8916 declared equivalent through @code{typedef}.
8919 @c leaving this out because neither J Gilmore nor R Pesch understand it.
8922 The two @code{struct}, @code{union}, or @code{enum} variables are
8923 declared in the same declaration. (Note: this may not be true for all C
8928 Range checking, if turned on, is done on mathematical operations. Array
8929 indices are not checked, since they are often used to index a pointer
8930 that is not itself an array.
8933 @subsubsection @value{GDBN} and C
8935 The @code{set print union} and @code{show print union} commands apply to
8936 the @code{union} type. When set to @samp{on}, any @code{union} that is
8937 inside a @code{struct} or @code{class} is also printed. Otherwise, it
8938 appears as @samp{@{...@}}.
8940 The @code{@@} operator aids in the debugging of dynamic arrays, formed
8941 with pointers and a memory allocation function. @xref{Expressions,
8945 * Debugging C plus plus::
8948 @node Debugging C plus plus
8949 @subsubsection @value{GDBN} features for C@t{++}
8951 @cindex commands for C@t{++}
8953 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
8954 designed specifically for use with C@t{++}. Here is a summary:
8957 @cindex break in overloaded functions
8958 @item @r{breakpoint menus}
8959 When you want a breakpoint in a function whose name is overloaded,
8960 @value{GDBN} breakpoint menus help you specify which function definition
8961 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
8963 @cindex overloading in C@t{++}
8964 @item rbreak @var{regex}
8965 Setting breakpoints using regular expressions is helpful for setting
8966 breakpoints on overloaded functions that are not members of any special
8968 @xref{Set Breaks, ,Setting breakpoints}.
8970 @cindex C@t{++} exception handling
8973 Debug C@t{++} exception handling using these commands. @xref{Set
8974 Catchpoints, , Setting catchpoints}.
8977 @item ptype @var{typename}
8978 Print inheritance relationships as well as other information for type
8980 @xref{Symbols, ,Examining the Symbol Table}.
8982 @cindex C@t{++} symbol display
8983 @item set print demangle
8984 @itemx show print demangle
8985 @itemx set print asm-demangle
8986 @itemx show print asm-demangle
8987 Control whether C@t{++} symbols display in their source form, both when
8988 displaying code as C@t{++} source and when displaying disassemblies.
8989 @xref{Print Settings, ,Print settings}.
8991 @item set print object
8992 @itemx show print object
8993 Choose whether to print derived (actual) or declared types of objects.
8994 @xref{Print Settings, ,Print settings}.
8996 @item set print vtbl
8997 @itemx show print vtbl
8998 Control the format for printing virtual function tables.
8999 @xref{Print Settings, ,Print settings}.
9000 (The @code{vtbl} commands do not work on programs compiled with the HP
9001 ANSI C@t{++} compiler (@code{aCC}).)
9003 @kindex set overload-resolution
9004 @cindex overloaded functions, overload resolution
9005 @item set overload-resolution on
9006 Enable overload resolution for C@t{++} expression evaluation. The default
9007 is on. For overloaded functions, @value{GDBN} evaluates the arguments
9008 and searches for a function whose signature matches the argument types,
9009 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
9010 expressions}, for details). If it cannot find a match, it emits a
9013 @item set overload-resolution off
9014 Disable overload resolution for C@t{++} expression evaluation. For
9015 overloaded functions that are not class member functions, @value{GDBN}
9016 chooses the first function of the specified name that it finds in the
9017 symbol table, whether or not its arguments are of the correct type. For
9018 overloaded functions that are class member functions, @value{GDBN}
9019 searches for a function whose signature @emph{exactly} matches the
9022 @kindex show overload-resolution
9023 @item show overload-resolution
9024 Show the current setting of overload resolution.
9026 @item @r{Overloaded symbol names}
9027 You can specify a particular definition of an overloaded symbol, using
9028 the same notation that is used to declare such symbols in C@t{++}: type
9029 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
9030 also use the @value{GDBN} command-line word completion facilities to list the
9031 available choices, or to finish the type list for you.
9032 @xref{Completion,, Command completion}, for details on how to do this.
9036 @subsection Objective-C
9039 This section provides information about some commands and command
9040 options that are useful for debugging Objective-C code. See also
9041 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
9042 few more commands specific to Objective-C support.
9045 * Method Names in Commands::
9046 * The Print Command with Objective-C::
9049 @node Method Names in Commands, The Print Command with Objective-C, Objective-C, Objective-C
9050 @subsubsection Method Names in Commands
9052 The following commands have been extended to accept Objective-C method
9053 names as line specifications:
9055 @kindex clear@r{, and Objective-C}
9056 @kindex break@r{, and Objective-C}
9057 @kindex info line@r{, and Objective-C}
9058 @kindex jump@r{, and Objective-C}
9059 @kindex list@r{, and Objective-C}
9063 @item @code{info line}
9068 A fully qualified Objective-C method name is specified as
9071 -[@var{Class} @var{methodName}]
9074 where the minus sign is used to indicate an instance method and a
9075 plus sign (not shown) is used to indicate a class method. The class
9076 name @var{Class} and method name @var{methodName} are enclosed in
9077 brackets, similar to the way messages are specified in Objective-C
9078 source code. For example, to set a breakpoint at the @code{create}
9079 instance method of class @code{Fruit} in the program currently being
9083 break -[Fruit create]
9086 To list ten program lines around the @code{initialize} class method,
9090 list +[NSText initialize]
9093 In the current version of @value{GDBN}, the plus or minus sign is
9094 required. In future versions of @value{GDBN}, the plus or minus
9095 sign will be optional, but you can use it to narrow the search. It
9096 is also possible to specify just a method name:
9102 You must specify the complete method name, including any colons. If
9103 your program's source files contain more than one @code{create} method,
9104 you'll be presented with a numbered list of classes that implement that
9105 method. Indicate your choice by number, or type @samp{0} to exit if
9108 As another example, to clear a breakpoint established at the
9109 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
9112 clear -[NSWindow makeKeyAndOrderFront:]
9115 @node The Print Command with Objective-C
9116 @subsubsection The Print Command With Objective-C
9117 @cindex Objective-C, print objects
9118 @kindex print-object
9119 @kindex po @r{(@code{print-object})}
9121 The print command has also been extended to accept methods. For example:
9124 print -[@var{object} hash]
9127 @cindex print an Objective-C object description
9128 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
9130 will tell @value{GDBN} to send the @code{hash} message to @var{object}
9131 and print the result. Also, an additional command has been added,
9132 @code{print-object} or @code{po} for short, which is meant to print
9133 the description of an object. However, this command may only work
9134 with certain Objective-C libraries that have a particular hook
9135 function, @code{_NSPrintForDebugger}, defined.
9139 @cindex Fortran-specific support in @value{GDBN}
9141 @value{GDBN} can be used to debug programs written in Fortran, but it
9142 currently supports only the features of Fortran 77 language.
9144 @cindex trailing underscore, in Fortran symbols
9145 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
9146 among them) append an underscore to the names of variables and
9147 functions. When you debug programs compiled by those compilers, you
9148 will need to refer to variables and functions with a trailing
9152 * Fortran Operators:: Fortran operators and expressions
9153 * Fortran Defaults:: Default settings for Fortran
9154 * Special Fortran commands:: Special @value{GDBN} commands for Fortran
9157 @node Fortran Operators
9158 @subsubsection Fortran operators and expressions
9160 @cindex Fortran operators and expressions
9162 Operators must be defined on values of specific types. For instance,
9163 @code{+} is defined on numbers, but not on characters or other non-
9164 arithmetic types. Operators are often defined on groups of types.
9168 The exponentiation operator. It raises the first operand to the power
9172 The range operator. Normally used in the form of array(low:high) to
9173 represent a section of array.
9176 @node Fortran Defaults
9177 @subsubsection Fortran Defaults
9179 @cindex Fortran Defaults
9181 Fortran symbols are usually case-insensitive, so @value{GDBN} by
9182 default uses case-insensitive matches for Fortran symbols. You can
9183 change that with the @samp{set case-insensitive} command, see
9184 @ref{Symbols}, for the details.
9186 @node Special Fortran commands
9187 @subsubsection Special Fortran commands
9189 @cindex Special Fortran commands
9191 @value{GDBN} had some commands to support Fortran specific feature,
9192 such as common block displaying.
9195 @cindex @code{COMMON} blocks, Fortran
9197 @item info common @r{[}@var{common-name}@r{]}
9198 This command prints the values contained in the Fortran @code{COMMON}
9199 block whose name is @var{common-name}. With no argument, the names of
9200 all @code{COMMON} blocks visible at current program location are
9207 @cindex Pascal support in @value{GDBN}, limitations
9208 Debugging Pascal programs which use sets, subranges, file variables, or
9209 nested functions does not currently work. @value{GDBN} does not support
9210 entering expressions, printing values, or similar features using Pascal
9213 The Pascal-specific command @code{set print pascal_static-members}
9214 controls whether static members of Pascal objects are displayed.
9215 @xref{Print Settings, pascal_static-members}.
9218 @subsection Modula-2
9220 @cindex Modula-2, @value{GDBN} support
9222 The extensions made to @value{GDBN} to support Modula-2 only support
9223 output from the @sc{gnu} Modula-2 compiler (which is currently being
9224 developed). Other Modula-2 compilers are not currently supported, and
9225 attempting to debug executables produced by them is most likely
9226 to give an error as @value{GDBN} reads in the executable's symbol
9229 @cindex expressions in Modula-2
9231 * M2 Operators:: Built-in operators
9232 * Built-In Func/Proc:: Built-in functions and procedures
9233 * M2 Constants:: Modula-2 constants
9234 * M2 Defaults:: Default settings for Modula-2
9235 * Deviations:: Deviations from standard Modula-2
9236 * M2 Checks:: Modula-2 type and range checks
9237 * M2 Scope:: The scope operators @code{::} and @code{.}
9238 * GDB/M2:: @value{GDBN} and Modula-2
9242 @subsubsection Operators
9243 @cindex Modula-2 operators
9245 Operators must be defined on values of specific types. For instance,
9246 @code{+} is defined on numbers, but not on structures. Operators are
9247 often defined on groups of types. For the purposes of Modula-2, the
9248 following definitions hold:
9253 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
9257 @emph{Character types} consist of @code{CHAR} and its subranges.
9260 @emph{Floating-point types} consist of @code{REAL}.
9263 @emph{Pointer types} consist of anything declared as @code{POINTER TO
9267 @emph{Scalar types} consist of all of the above.
9270 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
9273 @emph{Boolean types} consist of @code{BOOLEAN}.
9277 The following operators are supported, and appear in order of
9278 increasing precedence:
9282 Function argument or array index separator.
9285 Assignment. The value of @var{var} @code{:=} @var{value} is
9289 Less than, greater than on integral, floating-point, or enumerated
9293 Less than or equal to, greater than or equal to
9294 on integral, floating-point and enumerated types, or set inclusion on
9295 set types. Same precedence as @code{<}.
9297 @item =@r{, }<>@r{, }#
9298 Equality and two ways of expressing inequality, valid on scalar types.
9299 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
9300 available for inequality, since @code{#} conflicts with the script
9304 Set membership. Defined on set types and the types of their members.
9305 Same precedence as @code{<}.
9308 Boolean disjunction. Defined on boolean types.
9311 Boolean conjunction. Defined on boolean types.
9314 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9317 Addition and subtraction on integral and floating-point types, or union
9318 and difference on set types.
9321 Multiplication on integral and floating-point types, or set intersection
9325 Division on floating-point types, or symmetric set difference on set
9326 types. Same precedence as @code{*}.
9329 Integer division and remainder. Defined on integral types. Same
9330 precedence as @code{*}.
9333 Negative. Defined on @code{INTEGER} and @code{REAL} data.
9336 Pointer dereferencing. Defined on pointer types.
9339 Boolean negation. Defined on boolean types. Same precedence as
9343 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
9344 precedence as @code{^}.
9347 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
9350 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
9354 @value{GDBN} and Modula-2 scope operators.
9358 @emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
9359 treats the use of the operator @code{IN}, or the use of operators
9360 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
9361 @code{<=}, and @code{>=} on sets as an error.
9365 @node Built-In Func/Proc
9366 @subsubsection Built-in functions and procedures
9367 @cindex Modula-2 built-ins
9369 Modula-2 also makes available several built-in procedures and functions.
9370 In describing these, the following metavariables are used:
9375 represents an @code{ARRAY} variable.
9378 represents a @code{CHAR} constant or variable.
9381 represents a variable or constant of integral type.
9384 represents an identifier that belongs to a set. Generally used in the
9385 same function with the metavariable @var{s}. The type of @var{s} should
9386 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
9389 represents a variable or constant of integral or floating-point type.
9392 represents a variable or constant of floating-point type.
9398 represents a variable.
9401 represents a variable or constant of one of many types. See the
9402 explanation of the function for details.
9405 All Modula-2 built-in procedures also return a result, described below.
9409 Returns the absolute value of @var{n}.
9412 If @var{c} is a lower case letter, it returns its upper case
9413 equivalent, otherwise it returns its argument.
9416 Returns the character whose ordinal value is @var{i}.
9419 Decrements the value in the variable @var{v} by one. Returns the new value.
9421 @item DEC(@var{v},@var{i})
9422 Decrements the value in the variable @var{v} by @var{i}. Returns the
9425 @item EXCL(@var{m},@var{s})
9426 Removes the element @var{m} from the set @var{s}. Returns the new
9429 @item FLOAT(@var{i})
9430 Returns the floating point equivalent of the integer @var{i}.
9433 Returns the index of the last member of @var{a}.
9436 Increments the value in the variable @var{v} by one. Returns the new value.
9438 @item INC(@var{v},@var{i})
9439 Increments the value in the variable @var{v} by @var{i}. Returns the
9442 @item INCL(@var{m},@var{s})
9443 Adds the element @var{m} to the set @var{s} if it is not already
9444 there. Returns the new set.
9447 Returns the maximum value of the type @var{t}.
9450 Returns the minimum value of the type @var{t}.
9453 Returns boolean TRUE if @var{i} is an odd number.
9456 Returns the ordinal value of its argument. For example, the ordinal
9457 value of a character is its @sc{ascii} value (on machines supporting the
9458 @sc{ascii} character set). @var{x} must be of an ordered type, which include
9459 integral, character and enumerated types.
9462 Returns the size of its argument. @var{x} can be a variable or a type.
9464 @item TRUNC(@var{r})
9465 Returns the integral part of @var{r}.
9467 @item VAL(@var{t},@var{i})
9468 Returns the member of the type @var{t} whose ordinal value is @var{i}.
9472 @emph{Warning:} Sets and their operations are not yet supported, so
9473 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
9477 @cindex Modula-2 constants
9479 @subsubsection Constants
9481 @value{GDBN} allows you to express the constants of Modula-2 in the following
9487 Integer constants are simply a sequence of digits. When used in an
9488 expression, a constant is interpreted to be type-compatible with the
9489 rest of the expression. Hexadecimal integers are specified by a
9490 trailing @samp{H}, and octal integers by a trailing @samp{B}.
9493 Floating point constants appear as a sequence of digits, followed by a
9494 decimal point and another sequence of digits. An optional exponent can
9495 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
9496 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
9497 digits of the floating point constant must be valid decimal (base 10)
9501 Character constants consist of a single character enclosed by a pair of
9502 like quotes, either single (@code{'}) or double (@code{"}). They may
9503 also be expressed by their ordinal value (their @sc{ascii} value, usually)
9504 followed by a @samp{C}.
9507 String constants consist of a sequence of characters enclosed by a
9508 pair of like quotes, either single (@code{'}) or double (@code{"}).
9509 Escape sequences in the style of C are also allowed. @xref{C
9510 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
9514 Enumerated constants consist of an enumerated identifier.
9517 Boolean constants consist of the identifiers @code{TRUE} and
9521 Pointer constants consist of integral values only.
9524 Set constants are not yet supported.
9528 @subsubsection Modula-2 defaults
9529 @cindex Modula-2 defaults
9531 If type and range checking are set automatically by @value{GDBN}, they
9532 both default to @code{on} whenever the working language changes to
9533 Modula-2. This happens regardless of whether you or @value{GDBN}
9534 selected the working language.
9536 If you allow @value{GDBN} to set the language automatically, then entering
9537 code compiled from a file whose name ends with @file{.mod} sets the
9538 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
9539 the language automatically}, for further details.
9542 @subsubsection Deviations from standard Modula-2
9543 @cindex Modula-2, deviations from
9545 A few changes have been made to make Modula-2 programs easier to debug.
9546 This is done primarily via loosening its type strictness:
9550 Unlike in standard Modula-2, pointer constants can be formed by
9551 integers. This allows you to modify pointer variables during
9552 debugging. (In standard Modula-2, the actual address contained in a
9553 pointer variable is hidden from you; it can only be modified
9554 through direct assignment to another pointer variable or expression that
9555 returned a pointer.)
9558 C escape sequences can be used in strings and characters to represent
9559 non-printable characters. @value{GDBN} prints out strings with these
9560 escape sequences embedded. Single non-printable characters are
9561 printed using the @samp{CHR(@var{nnn})} format.
9564 The assignment operator (@code{:=}) returns the value of its right-hand
9568 All built-in procedures both modify @emph{and} return their argument.
9572 @subsubsection Modula-2 type and range checks
9573 @cindex Modula-2 checks
9576 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
9579 @c FIXME remove warning when type/range checks added
9581 @value{GDBN} considers two Modula-2 variables type equivalent if:
9585 They are of types that have been declared equivalent via a @code{TYPE
9586 @var{t1} = @var{t2}} statement
9589 They have been declared on the same line. (Note: This is true of the
9590 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
9593 As long as type checking is enabled, any attempt to combine variables
9594 whose types are not equivalent is an error.
9596 Range checking is done on all mathematical operations, assignment, array
9597 index bounds, and all built-in functions and procedures.
9600 @subsubsection The scope operators @code{::} and @code{.}
9602 @cindex @code{.}, Modula-2 scope operator
9603 @cindex colon, doubled as scope operator
9605 @vindex colon-colon@r{, in Modula-2}
9606 @c Info cannot handle :: but TeX can.
9609 @vindex ::@r{, in Modula-2}
9612 There are a few subtle differences between the Modula-2 scope operator
9613 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
9618 @var{module} . @var{id}
9619 @var{scope} :: @var{id}
9623 where @var{scope} is the name of a module or a procedure,
9624 @var{module} the name of a module, and @var{id} is any declared
9625 identifier within your program, except another module.
9627 Using the @code{::} operator makes @value{GDBN} search the scope
9628 specified by @var{scope} for the identifier @var{id}. If it is not
9629 found in the specified scope, then @value{GDBN} searches all scopes
9630 enclosing the one specified by @var{scope}.
9632 Using the @code{.} operator makes @value{GDBN} search the current scope for
9633 the identifier specified by @var{id} that was imported from the
9634 definition module specified by @var{module}. With this operator, it is
9635 an error if the identifier @var{id} was not imported from definition
9636 module @var{module}, or if @var{id} is not an identifier in
9640 @subsubsection @value{GDBN} and Modula-2
9642 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
9643 Five subcommands of @code{set print} and @code{show print} apply
9644 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
9645 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
9646 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
9647 analogue in Modula-2.
9649 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
9650 with any language, is not useful with Modula-2. Its
9651 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
9652 created in Modula-2 as they can in C or C@t{++}. However, because an
9653 address can be specified by an integral constant, the construct
9654 @samp{@{@var{type}@}@var{adrexp}} is still useful.
9656 @cindex @code{#} in Modula-2
9657 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
9658 interpreted as the beginning of a comment. Use @code{<>} instead.
9664 The extensions made to @value{GDBN} for Ada only support
9665 output from the @sc{gnu} Ada (GNAT) compiler.
9666 Other Ada compilers are not currently supported, and
9667 attempting to debug executables produced by them is most likely
9671 @cindex expressions in Ada
9673 * Ada Mode Intro:: General remarks on the Ada syntax
9674 and semantics supported by Ada mode
9676 * Omissions from Ada:: Restrictions on the Ada expression syntax.
9677 * Additions to Ada:: Extensions of the Ada expression syntax.
9678 * Stopping Before Main Program:: Debugging the program during elaboration.
9679 * Ada Glitches:: Known peculiarities of Ada mode.
9682 @node Ada Mode Intro
9683 @subsubsection Introduction
9684 @cindex Ada mode, general
9686 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
9687 syntax, with some extensions.
9688 The philosophy behind the design of this subset is
9692 That @value{GDBN} should provide basic literals and access to operations for
9693 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
9694 leaving more sophisticated computations to subprograms written into the
9695 program (which therefore may be called from @value{GDBN}).
9698 That type safety and strict adherence to Ada language restrictions
9699 are not particularly important to the @value{GDBN} user.
9702 That brevity is important to the @value{GDBN} user.
9705 Thus, for brevity, the debugger acts as if there were
9706 implicit @code{with} and @code{use} clauses in effect for all user-written
9707 packages, making it unnecessary to fully qualify most names with
9708 their packages, regardless of context. Where this causes ambiguity,
9709 @value{GDBN} asks the user's intent.
9711 The debugger will start in Ada mode if it detects an Ada main program.
9712 As for other languages, it will enter Ada mode when stopped in a program that
9713 was translated from an Ada source file.
9715 While in Ada mode, you may use `@t{--}' for comments. This is useful
9716 mostly for documenting command files. The standard @value{GDBN} comment
9717 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
9718 middle (to allow based literals).
9720 The debugger supports limited overloading. Given a subprogram call in which
9721 the function symbol has multiple definitions, it will use the number of
9722 actual parameters and some information about their types to attempt to narrow
9723 the set of definitions. It also makes very limited use of context, preferring
9724 procedures to functions in the context of the @code{call} command, and
9725 functions to procedures elsewhere.
9727 @node Omissions from Ada
9728 @subsubsection Omissions from Ada
9729 @cindex Ada, omissions from
9731 Here are the notable omissions from the subset:
9735 Only a subset of the attributes are supported:
9739 @t{'First}, @t{'Last}, and @t{'Length}
9740 on array objects (not on types and subtypes).
9743 @t{'Min} and @t{'Max}.
9746 @t{'Pos} and @t{'Val}.
9752 @t{'Range} on array objects (not subtypes), but only as the right
9753 operand of the membership (@code{in}) operator.
9756 @t{'Access}, @t{'Unchecked_Access}, and
9757 @t{'Unrestricted_Access} (a GNAT extension).
9765 @code{Characters.Latin_1} are not available and
9766 concatenation is not implemented. Thus, escape characters in strings are
9767 not currently available.
9770 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
9771 equality of representations. They will generally work correctly
9772 for strings and arrays whose elements have integer or enumeration types.
9773 They may not work correctly for arrays whose element
9774 types have user-defined equality, for arrays of real values
9775 (in particular, IEEE-conformant floating point, because of negative
9776 zeroes and NaNs), and for arrays whose elements contain unused bits with
9777 indeterminate values.
9780 The other component-by-component array operations (@code{and}, @code{or},
9781 @code{xor}, @code{not}, and relational tests other than equality)
9782 are not implemented.
9785 There are no record or array aggregates.
9788 Calls to dispatching subprograms are not implemented.
9791 The overloading algorithm is much more limited (i.e., less selective)
9792 than that of real Ada. It makes only limited use of the context in which a subexpression
9793 appears to resolve its meaning, and it is much looser in its rules for allowing
9794 type matches. As a result, some function calls will be ambiguous, and the user
9795 will be asked to choose the proper resolution.
9798 The @code{new} operator is not implemented.
9801 Entry calls are not implemented.
9804 Aside from printing, arithmetic operations on the native VAX floating-point
9805 formats are not supported.
9808 It is not possible to slice a packed array.
9811 @node Additions to Ada
9812 @subsubsection Additions to Ada
9813 @cindex Ada, deviations from
9815 As it does for other languages, @value{GDBN} makes certain generic
9816 extensions to Ada (@pxref{Expressions}):
9820 If the expression @var{E} is a variable residing in memory
9821 (typically a local variable or array element) and @var{N} is
9822 a positive integer, then @code{@var{E}@@@var{N}} displays the values of
9823 @var{E} and the @var{N}-1 adjacent variables following it in memory as an array.
9824 In Ada, this operator is generally not necessary, since its prime use
9825 is in displaying parts of an array, and slicing will usually do this in Ada.
9826 However, there are occasional uses when debugging programs
9827 in which certain debugging information has been optimized away.
9830 @code{@var{B}::@var{var}} means ``the variable named @var{var} that appears
9831 in function or file @var{B}.'' When @var{B} is a file name, you must typically
9832 surround it in single quotes.
9835 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
9836 @var{type} that appears at address @var{addr}.''
9839 A name starting with @samp{$} is a convenience variable
9840 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
9843 In addition, @value{GDBN} provides a few other shortcuts and outright additions specific
9848 The assignment statement is allowed as an expression, returning
9849 its right-hand operand as its value. Thus, you may enter
9853 print A(tmp := y + 1)
9857 The semicolon is allowed as an ``operator,'' returning as its value
9858 the value of its right-hand operand.
9859 This allows, for example,
9860 complex conditional breaks:
9864 condition 1 (report(i); k += 1; A(k) > 100)
9868 Rather than use catenation and symbolic character names to introduce special
9869 characters into strings, one may instead use a special bracket notation,
9870 which is also used to print strings. A sequence of characters of the form
9871 @samp{["@var{XX}"]} within a string or character literal denotes the
9872 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
9873 sequence of characters @samp{["""]} also denotes a single quotation mark
9874 in strings. For example,
9876 "One line.["0a"]Next line.["0a"]"
9879 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF}) after each
9883 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
9884 @t{'Max} is optional (and is ignored in any case). For example, it is valid
9892 When printing arrays, @value{GDBN} uses positional notation when the
9893 array has a lower bound of 1, and uses a modified named notation otherwise.
9894 For example, a one-dimensional array of three integers with a lower bound of 3 might print as
9901 That is, in contrast to valid Ada, only the first component has a @code{=>}
9905 You may abbreviate attributes in expressions with any unique,
9906 multi-character subsequence of
9907 their names (an exact match gets preference).
9908 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
9909 in place of @t{a'length}.
9912 @cindex quoting Ada internal identifiers
9913 Since Ada is case-insensitive, the debugger normally maps identifiers you type
9914 to lower case. The GNAT compiler uses upper-case characters for
9915 some of its internal identifiers, which are normally of no interest to users.
9916 For the rare occasions when you actually have to look at them,
9917 enclose them in angle brackets to avoid the lower-case mapping.
9920 @value{GDBP} print <JMPBUF_SAVE>[0]
9924 Printing an object of class-wide type or dereferencing an
9925 access-to-class-wide value will display all the components of the object's
9926 specific type (as indicated by its run-time tag). Likewise, component
9927 selection on such a value will operate on the specific type of the
9932 @node Stopping Before Main Program
9933 @subsubsection Stopping at the Very Beginning
9935 @cindex breakpointing Ada elaboration code
9936 It is sometimes necessary to debug the program during elaboration, and
9937 before reaching the main procedure.
9938 As defined in the Ada Reference
9939 Manual, the elaboration code is invoked from a procedure called
9940 @code{adainit}. To run your program up to the beginning of
9941 elaboration, simply use the following two commands:
9942 @code{tbreak adainit} and @code{run}.
9945 @subsubsection Known Peculiarities of Ada Mode
9946 @cindex Ada, problems
9948 Besides the omissions listed previously (@pxref{Omissions from Ada}),
9949 we know of several problems with and limitations of Ada mode in
9951 some of which will be fixed with planned future releases of the debugger
9952 and the GNU Ada compiler.
9956 Currently, the debugger
9957 has insufficient information to determine whether certain pointers represent
9958 pointers to objects or the objects themselves.
9959 Thus, the user may have to tack an extra @code{.all} after an expression
9960 to get it printed properly.
9963 Static constants that the compiler chooses not to materialize as objects in
9964 storage are invisible to the debugger.
9967 Named parameter associations in function argument lists are ignored (the
9968 argument lists are treated as positional).
9971 Many useful library packages are currently invisible to the debugger.
9974 Fixed-point arithmetic, conversions, input, and output is carried out using
9975 floating-point arithmetic, and may give results that only approximate those on
9979 The type of the @t{'Address} attribute may not be @code{System.Address}.
9982 The GNAT compiler never generates the prefix @code{Standard} for any of
9983 the standard symbols defined by the Ada language. @value{GDBN} knows about
9984 this: it will strip the prefix from names when you use it, and will never
9985 look for a name you have so qualified among local symbols, nor match against
9986 symbols in other packages or subprograms. If you have
9987 defined entities anywhere in your program other than parameters and
9988 local variables whose simple names match names in @code{Standard},
9989 GNAT's lack of qualification here can cause confusion. When this happens,
9990 you can usually resolve the confusion
9991 by qualifying the problematic names with package
9992 @code{Standard} explicitly.
9995 @node Unsupported languages
9996 @section Unsupported languages
9998 @cindex unsupported languages
9999 @cindex minimal language
10000 In addition to the other fully-supported programming languages,
10001 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
10002 It does not represent a real programming language, but provides a set
10003 of capabilities close to what the C or assembly languages provide.
10004 This should allow most simple operations to be performed while debugging
10005 an application that uses a language currently not supported by @value{GDBN}.
10007 If the language is set to @code{auto}, @value{GDBN} will automatically
10008 select this language if the current frame corresponds to an unsupported
10012 @chapter Examining the Symbol Table
10014 The commands described in this chapter allow you to inquire about the
10015 symbols (names of variables, functions and types) defined in your
10016 program. This information is inherent in the text of your program and
10017 does not change as your program executes. @value{GDBN} finds it in your
10018 program's symbol table, in the file indicated when you started @value{GDBN}
10019 (@pxref{File Options, ,Choosing files}), or by one of the
10020 file-management commands (@pxref{Files, ,Commands to specify files}).
10022 @cindex symbol names
10023 @cindex names of symbols
10024 @cindex quoting names
10025 Occasionally, you may need to refer to symbols that contain unusual
10026 characters, which @value{GDBN} ordinarily treats as word delimiters. The
10027 most frequent case is in referring to static variables in other
10028 source files (@pxref{Variables,,Program variables}). File names
10029 are recorded in object files as debugging symbols, but @value{GDBN} would
10030 ordinarily parse a typical file name, like @file{foo.c}, as the three words
10031 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
10032 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
10039 looks up the value of @code{x} in the scope of the file @file{foo.c}.
10042 @cindex case-insensitive symbol names
10043 @cindex case sensitivity in symbol names
10044 @kindex set case-sensitive
10045 @item set case-sensitive on
10046 @itemx set case-sensitive off
10047 @itemx set case-sensitive auto
10048 Normally, when @value{GDBN} looks up symbols, it matches their names
10049 with case sensitivity determined by the current source language.
10050 Occasionally, you may wish to control that. The command @code{set
10051 case-sensitive} lets you do that by specifying @code{on} for
10052 case-sensitive matches or @code{off} for case-insensitive ones. If
10053 you specify @code{auto}, case sensitivity is reset to the default
10054 suitable for the source language. The default is case-sensitive
10055 matches for all languages except for Fortran, for which the default is
10056 case-insensitive matches.
10058 @kindex show case-sensitive
10059 @item show case-sensitive
10060 This command shows the current setting of case sensitivity for symbols
10063 @kindex info address
10064 @cindex address of a symbol
10065 @item info address @var{symbol}
10066 Describe where the data for @var{symbol} is stored. For a register
10067 variable, this says which register it is kept in. For a non-register
10068 local variable, this prints the stack-frame offset at which the variable
10071 Note the contrast with @samp{print &@var{symbol}}, which does not work
10072 at all for a register variable, and for a stack local variable prints
10073 the exact address of the current instantiation of the variable.
10075 @kindex info symbol
10076 @cindex symbol from address
10077 @cindex closest symbol and offset for an address
10078 @item info symbol @var{addr}
10079 Print the name of a symbol which is stored at the address @var{addr}.
10080 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
10081 nearest symbol and an offset from it:
10084 (@value{GDBP}) info symbol 0x54320
10085 _initialize_vx + 396 in section .text
10089 This is the opposite of the @code{info address} command. You can use
10090 it to find out the name of a variable or a function given its address.
10093 @item whatis @var{expr}
10094 Print the data type of expression @var{expr}. @var{expr} is not
10095 actually evaluated, and any side-effecting operations (such as
10096 assignments or function calls) inside it do not take place.
10097 @xref{Expressions, ,Expressions}.
10100 Print the data type of @code{$}, the last value in the value history.
10103 @item ptype @var{typename}
10104 Print a description of data type @var{typename}. @var{typename} may be
10105 the name of a type, or for C code it may have the form @samp{class
10106 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
10107 @var{union-tag}} or @samp{enum @var{enum-tag}}.
10109 @item ptype @var{expr}
10111 Print a description of the type of expression @var{expr}. @code{ptype}
10112 differs from @code{whatis} by printing a detailed description, instead
10113 of just the name of the type.
10115 For example, for this variable declaration:
10118 struct complex @{double real; double imag;@} v;
10122 the two commands give this output:
10126 (@value{GDBP}) whatis v
10127 type = struct complex
10128 (@value{GDBP}) ptype v
10129 type = struct complex @{
10137 As with @code{whatis}, using @code{ptype} without an argument refers to
10138 the type of @code{$}, the last value in the value history.
10140 @cindex incomplete type
10141 Sometimes, programs use opaque data types or incomplete specifications
10142 of complex data structure. If the debug information included in the
10143 program does not allow @value{GDBN} to display a full declaration of
10144 the data type, it will say @samp{<incomplete type>}. For example,
10145 given these declarations:
10149 struct foo *fooptr;
10153 but no definition for @code{struct foo} itself, @value{GDBN} will say:
10157 $1 = <incomplete type>
10161 ``Incomplete type'' is C terminology for data types that are not
10162 completely specified.
10165 @item info types @var{regexp}
10167 Print a brief description of all types whose names match the regular
10168 expression @var{regexp} (or all types in your program, if you supply
10169 no argument). Each complete typename is matched as though it were a
10170 complete line; thus, @samp{i type value} gives information on all
10171 types in your program whose names include the string @code{value}, but
10172 @samp{i type ^value$} gives information only on types whose complete
10173 name is @code{value}.
10175 This command differs from @code{ptype} in two ways: first, like
10176 @code{whatis}, it does not print a detailed description; second, it
10177 lists all source files where a type is defined.
10180 @cindex local variables
10181 @item info scope @var{location}
10182 List all the variables local to a particular scope. This command
10183 accepts a @var{location} argument---a function name, a source line, or
10184 an address preceded by a @samp{*}, and prints all the variables local
10185 to the scope defined by that location. For example:
10188 (@value{GDBP}) @b{info scope command_line_handler}
10189 Scope for command_line_handler:
10190 Symbol rl is an argument at stack/frame offset 8, length 4.
10191 Symbol linebuffer is in static storage at address 0x150a18, length 4.
10192 Symbol linelength is in static storage at address 0x150a1c, length 4.
10193 Symbol p is a local variable in register $esi, length 4.
10194 Symbol p1 is a local variable in register $ebx, length 4.
10195 Symbol nline is a local variable in register $edx, length 4.
10196 Symbol repeat is a local variable at frame offset -8, length 4.
10200 This command is especially useful for determining what data to collect
10201 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
10204 @kindex info source
10206 Show information about the current source file---that is, the source file for
10207 the function containing the current point of execution:
10210 the name of the source file, and the directory containing it,
10212 the directory it was compiled in,
10214 its length, in lines,
10216 which programming language it is written in,
10218 whether the executable includes debugging information for that file, and
10219 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
10221 whether the debugging information includes information about
10222 preprocessor macros.
10226 @kindex info sources
10228 Print the names of all source files in your program for which there is
10229 debugging information, organized into two lists: files whose symbols
10230 have already been read, and files whose symbols will be read when needed.
10232 @kindex info functions
10233 @item info functions
10234 Print the names and data types of all defined functions.
10236 @item info functions @var{regexp}
10237 Print the names and data types of all defined functions
10238 whose names contain a match for regular expression @var{regexp}.
10239 Thus, @samp{info fun step} finds all functions whose names
10240 include @code{step}; @samp{info fun ^step} finds those whose names
10241 start with @code{step}. If a function name contains characters
10242 that conflict with the regular expression language (e.g.@:
10243 @samp{operator*()}), they may be quoted with a backslash.
10245 @kindex info variables
10246 @item info variables
10247 Print the names and data types of all variables that are declared
10248 outside of functions (i.e.@: excluding local variables).
10250 @item info variables @var{regexp}
10251 Print the names and data types of all variables (except for local
10252 variables) whose names contain a match for regular expression
10255 @kindex info classes
10256 @cindex Objective-C, classes and selectors
10258 @itemx info classes @var{regexp}
10259 Display all Objective-C classes in your program, or
10260 (with the @var{regexp} argument) all those matching a particular regular
10263 @kindex info selectors
10264 @item info selectors
10265 @itemx info selectors @var{regexp}
10266 Display all Objective-C selectors in your program, or
10267 (with the @var{regexp} argument) all those matching a particular regular
10271 This was never implemented.
10272 @kindex info methods
10274 @itemx info methods @var{regexp}
10275 The @code{info methods} command permits the user to examine all defined
10276 methods within C@t{++} program, or (with the @var{regexp} argument) a
10277 specific set of methods found in the various C@t{++} classes. Many
10278 C@t{++} classes provide a large number of methods. Thus, the output
10279 from the @code{ptype} command can be overwhelming and hard to use. The
10280 @code{info-methods} command filters the methods, printing only those
10281 which match the regular-expression @var{regexp}.
10284 @cindex reloading symbols
10285 Some systems allow individual object files that make up your program to
10286 be replaced without stopping and restarting your program. For example,
10287 in VxWorks you can simply recompile a defective object file and keep on
10288 running. If you are running on one of these systems, you can allow
10289 @value{GDBN} to reload the symbols for automatically relinked modules:
10292 @kindex set symbol-reloading
10293 @item set symbol-reloading on
10294 Replace symbol definitions for the corresponding source file when an
10295 object file with a particular name is seen again.
10297 @item set symbol-reloading off
10298 Do not replace symbol definitions when encountering object files of the
10299 same name more than once. This is the default state; if you are not
10300 running on a system that permits automatic relinking of modules, you
10301 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
10302 may discard symbols when linking large programs, that may contain
10303 several modules (from different directories or libraries) with the same
10306 @kindex show symbol-reloading
10307 @item show symbol-reloading
10308 Show the current @code{on} or @code{off} setting.
10311 @cindex opaque data types
10312 @kindex set opaque-type-resolution
10313 @item set opaque-type-resolution on
10314 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
10315 declared as a pointer to a @code{struct}, @code{class}, or
10316 @code{union}---for example, @code{struct MyType *}---that is used in one
10317 source file although the full declaration of @code{struct MyType} is in
10318 another source file. The default is on.
10320 A change in the setting of this subcommand will not take effect until
10321 the next time symbols for a file are loaded.
10323 @item set opaque-type-resolution off
10324 Tell @value{GDBN} not to resolve opaque types. In this case, the type
10325 is printed as follows:
10327 @{<no data fields>@}
10330 @kindex show opaque-type-resolution
10331 @item show opaque-type-resolution
10332 Show whether opaque types are resolved or not.
10334 @kindex maint print symbols
10335 @cindex symbol dump
10336 @kindex maint print psymbols
10337 @cindex partial symbol dump
10338 @item maint print symbols @var{filename}
10339 @itemx maint print psymbols @var{filename}
10340 @itemx maint print msymbols @var{filename}
10341 Write a dump of debugging symbol data into the file @var{filename}.
10342 These commands are used to debug the @value{GDBN} symbol-reading code. Only
10343 symbols with debugging data are included. If you use @samp{maint print
10344 symbols}, @value{GDBN} includes all the symbols for which it has already
10345 collected full details: that is, @var{filename} reflects symbols for
10346 only those files whose symbols @value{GDBN} has read. You can use the
10347 command @code{info sources} to find out which files these are. If you
10348 use @samp{maint print psymbols} instead, the dump shows information about
10349 symbols that @value{GDBN} only knows partially---that is, symbols defined in
10350 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
10351 @samp{maint print msymbols} dumps just the minimal symbol information
10352 required for each object file from which @value{GDBN} has read some symbols.
10353 @xref{Files, ,Commands to specify files}, for a discussion of how
10354 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
10356 @kindex maint info symtabs
10357 @kindex maint info psymtabs
10358 @cindex listing @value{GDBN}'s internal symbol tables
10359 @cindex symbol tables, listing @value{GDBN}'s internal
10360 @cindex full symbol tables, listing @value{GDBN}'s internal
10361 @cindex partial symbol tables, listing @value{GDBN}'s internal
10362 @item maint info symtabs @r{[} @var{regexp} @r{]}
10363 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
10365 List the @code{struct symtab} or @code{struct partial_symtab}
10366 structures whose names match @var{regexp}. If @var{regexp} is not
10367 given, list them all. The output includes expressions which you can
10368 copy into a @value{GDBN} debugging this one to examine a particular
10369 structure in more detail. For example:
10372 (@value{GDBP}) maint info psymtabs dwarf2read
10373 @{ objfile /home/gnu/build/gdb/gdb
10374 ((struct objfile *) 0x82e69d0)
10375 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
10376 ((struct partial_symtab *) 0x8474b10)
10379 text addresses 0x814d3c8 -- 0x8158074
10380 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
10381 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
10382 dependencies (none)
10385 (@value{GDBP}) maint info symtabs
10389 We see that there is one partial symbol table whose filename contains
10390 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
10391 and we see that @value{GDBN} has not read in any symtabs yet at all.
10392 If we set a breakpoint on a function, that will cause @value{GDBN} to
10393 read the symtab for the compilation unit containing that function:
10396 (@value{GDBP}) break dwarf2_psymtab_to_symtab
10397 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
10399 (@value{GDBP}) maint info symtabs
10400 @{ objfile /home/gnu/build/gdb/gdb
10401 ((struct objfile *) 0x82e69d0)
10402 @{ symtab /home/gnu/src/gdb/dwarf2read.c
10403 ((struct symtab *) 0x86c1f38)
10406 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
10407 debugformat DWARF 2
10416 @chapter Altering Execution
10418 Once you think you have found an error in your program, you might want to
10419 find out for certain whether correcting the apparent error would lead to
10420 correct results in the rest of the run. You can find the answer by
10421 experiment, using the @value{GDBN} features for altering execution of the
10424 For example, you can store new values into variables or memory
10425 locations, give your program a signal, restart it at a different
10426 address, or even return prematurely from a function.
10429 * Assignment:: Assignment to variables
10430 * Jumping:: Continuing at a different address
10431 * Signaling:: Giving your program a signal
10432 * Returning:: Returning from a function
10433 * Calling:: Calling your program's functions
10434 * Patching:: Patching your program
10438 @section Assignment to variables
10441 @cindex setting variables
10442 To alter the value of a variable, evaluate an assignment expression.
10443 @xref{Expressions, ,Expressions}. For example,
10450 stores the value 4 into the variable @code{x}, and then prints the
10451 value of the assignment expression (which is 4).
10452 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
10453 information on operators in supported languages.
10455 @kindex set variable
10456 @cindex variables, setting
10457 If you are not interested in seeing the value of the assignment, use the
10458 @code{set} command instead of the @code{print} command. @code{set} is
10459 really the same as @code{print} except that the expression's value is
10460 not printed and is not put in the value history (@pxref{Value History,
10461 ,Value history}). The expression is evaluated only for its effects.
10463 If the beginning of the argument string of the @code{set} command
10464 appears identical to a @code{set} subcommand, use the @code{set
10465 variable} command instead of just @code{set}. This command is identical
10466 to @code{set} except for its lack of subcommands. For example, if your
10467 program has a variable @code{width}, you get an error if you try to set
10468 a new value with just @samp{set width=13}, because @value{GDBN} has the
10469 command @code{set width}:
10472 (@value{GDBP}) whatis width
10474 (@value{GDBP}) p width
10476 (@value{GDBP}) set width=47
10477 Invalid syntax in expression.
10481 The invalid expression, of course, is @samp{=47}. In
10482 order to actually set the program's variable @code{width}, use
10485 (@value{GDBP}) set var width=47
10488 Because the @code{set} command has many subcommands that can conflict
10489 with the names of program variables, it is a good idea to use the
10490 @code{set variable} command instead of just @code{set}. For example, if
10491 your program has a variable @code{g}, you run into problems if you try
10492 to set a new value with just @samp{set g=4}, because @value{GDBN} has
10493 the command @code{set gnutarget}, abbreviated @code{set g}:
10497 (@value{GDBP}) whatis g
10501 (@value{GDBP}) set g=4
10505 The program being debugged has been started already.
10506 Start it from the beginning? (y or n) y
10507 Starting program: /home/smith/cc_progs/a.out
10508 "/home/smith/cc_progs/a.out": can't open to read symbols:
10509 Invalid bfd target.
10510 (@value{GDBP}) show g
10511 The current BFD target is "=4".
10516 The program variable @code{g} did not change, and you silently set the
10517 @code{gnutarget} to an invalid value. In order to set the variable
10521 (@value{GDBP}) set var g=4
10524 @value{GDBN} allows more implicit conversions in assignments than C; you can
10525 freely store an integer value into a pointer variable or vice versa,
10526 and you can convert any structure to any other structure that is the
10527 same length or shorter.
10528 @comment FIXME: how do structs align/pad in these conversions?
10529 @comment /doc@cygnus.com 18dec1990
10531 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
10532 construct to generate a value of specified type at a specified address
10533 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
10534 to memory location @code{0x83040} as an integer (which implies a certain size
10535 and representation in memory), and
10538 set @{int@}0x83040 = 4
10542 stores the value 4 into that memory location.
10545 @section Continuing at a different address
10547 Ordinarily, when you continue your program, you do so at the place where
10548 it stopped, with the @code{continue} command. You can instead continue at
10549 an address of your own choosing, with the following commands:
10553 @item jump @var{linespec}
10554 Resume execution at line @var{linespec}. Execution stops again
10555 immediately if there is a breakpoint there. @xref{List, ,Printing
10556 source lines}, for a description of the different forms of
10557 @var{linespec}. It is common practice to use the @code{tbreak} command
10558 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
10561 The @code{jump} command does not change the current stack frame, or
10562 the stack pointer, or the contents of any memory location or any
10563 register other than the program counter. If line @var{linespec} is in
10564 a different function from the one currently executing, the results may
10565 be bizarre if the two functions expect different patterns of arguments or
10566 of local variables. For this reason, the @code{jump} command requests
10567 confirmation if the specified line is not in the function currently
10568 executing. However, even bizarre results are predictable if you are
10569 well acquainted with the machine-language code of your program.
10571 @item jump *@var{address}
10572 Resume execution at the instruction at address @var{address}.
10575 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
10576 On many systems, you can get much the same effect as the @code{jump}
10577 command by storing a new value into the register @code{$pc}. The
10578 difference is that this does not start your program running; it only
10579 changes the address of where it @emph{will} run when you continue. For
10587 makes the next @code{continue} command or stepping command execute at
10588 address @code{0x485}, rather than at the address where your program stopped.
10589 @xref{Continuing and Stepping, ,Continuing and stepping}.
10591 The most common occasion to use the @code{jump} command is to back
10592 up---perhaps with more breakpoints set---over a portion of a program
10593 that has already executed, in order to examine its execution in more
10598 @section Giving your program a signal
10599 @cindex deliver a signal to a program
10603 @item signal @var{signal}
10604 Resume execution where your program stopped, but immediately give it the
10605 signal @var{signal}. @var{signal} can be the name or the number of a
10606 signal. For example, on many systems @code{signal 2} and @code{signal
10607 SIGINT} are both ways of sending an interrupt signal.
10609 Alternatively, if @var{signal} is zero, continue execution without
10610 giving a signal. This is useful when your program stopped on account of
10611 a signal and would ordinary see the signal when resumed with the
10612 @code{continue} command; @samp{signal 0} causes it to resume without a
10615 @code{signal} does not repeat when you press @key{RET} a second time
10616 after executing the command.
10620 Invoking the @code{signal} command is not the same as invoking the
10621 @code{kill} utility from the shell. Sending a signal with @code{kill}
10622 causes @value{GDBN} to decide what to do with the signal depending on
10623 the signal handling tables (@pxref{Signals}). The @code{signal} command
10624 passes the signal directly to your program.
10628 @section Returning from a function
10631 @cindex returning from a function
10634 @itemx return @var{expression}
10635 You can cancel execution of a function call with the @code{return}
10636 command. If you give an
10637 @var{expression} argument, its value is used as the function's return
10641 When you use @code{return}, @value{GDBN} discards the selected stack frame
10642 (and all frames within it). You can think of this as making the
10643 discarded frame return prematurely. If you wish to specify a value to
10644 be returned, give that value as the argument to @code{return}.
10646 This pops the selected stack frame (@pxref{Selection, ,Selecting a
10647 frame}), and any other frames inside of it, leaving its caller as the
10648 innermost remaining frame. That frame becomes selected. The
10649 specified value is stored in the registers used for returning values
10652 The @code{return} command does not resume execution; it leaves the
10653 program stopped in the state that would exist if the function had just
10654 returned. In contrast, the @code{finish} command (@pxref{Continuing
10655 and Stepping, ,Continuing and stepping}) resumes execution until the
10656 selected stack frame returns naturally.
10659 @section Calling program functions
10662 @cindex calling functions
10663 @cindex inferior functions, calling
10664 @item print @var{expr}
10665 Evaluate the expression @var{expr} and display the resuling value.
10666 @var{expr} may include calls to functions in the program being
10670 @item call @var{expr}
10671 Evaluate the expression @var{expr} without displaying @code{void}
10674 You can use this variant of the @code{print} command if you want to
10675 execute a function from your program that does not return anything
10676 (a.k.a.@: @dfn{a void function}), but without cluttering the output
10677 with @code{void} returned values that @value{GDBN} will otherwise
10678 print. If the result is not void, it is printed and saved in the
10682 It is possible for the function you call via the @code{print} or
10683 @code{call} command to generate a signal (e.g., if there's a bug in
10684 the function, or if you passed it incorrect arguments). What happens
10685 in that case is controlled by the @code{set unwindonsignal} command.
10688 @item set unwindonsignal
10689 @kindex set unwindonsignal
10690 @cindex unwind stack in called functions
10691 @cindex call dummy stack unwinding
10692 Set unwinding of the stack if a signal is received while in a function
10693 that @value{GDBN} called in the program being debugged. If set to on,
10694 @value{GDBN} unwinds the stack it created for the call and restores
10695 the context to what it was before the call. If set to off (the
10696 default), @value{GDBN} stops in the frame where the signal was
10699 @item show unwindonsignal
10700 @kindex show unwindonsignal
10701 Show the current setting of stack unwinding in the functions called by
10705 @cindex weak alias functions
10706 Sometimes, a function you wish to call is actually a @dfn{weak alias}
10707 for another function. In such case, @value{GDBN} might not pick up
10708 the type information, including the types of the function arguments,
10709 which causes @value{GDBN} to call the inferior function incorrectly.
10710 As a result, the called function will function erroneously and may
10711 even crash. A solution to that is to use the name of the aliased
10715 @section Patching programs
10717 @cindex patching binaries
10718 @cindex writing into executables
10719 @cindex writing into corefiles
10721 By default, @value{GDBN} opens the file containing your program's
10722 executable code (or the corefile) read-only. This prevents accidental
10723 alterations to machine code; but it also prevents you from intentionally
10724 patching your program's binary.
10726 If you'd like to be able to patch the binary, you can specify that
10727 explicitly with the @code{set write} command. For example, you might
10728 want to turn on internal debugging flags, or even to make emergency
10734 @itemx set write off
10735 If you specify @samp{set write on}, @value{GDBN} opens executable and
10736 core files for both reading and writing; if you specify @samp{set write
10737 off} (the default), @value{GDBN} opens them read-only.
10739 If you have already loaded a file, you must load it again (using the
10740 @code{exec-file} or @code{core-file} command) after changing @code{set
10741 write}, for your new setting to take effect.
10745 Display whether executable files and core files are opened for writing
10746 as well as reading.
10750 @chapter @value{GDBN} Files
10752 @value{GDBN} needs to know the file name of the program to be debugged,
10753 both in order to read its symbol table and in order to start your
10754 program. To debug a core dump of a previous run, you must also tell
10755 @value{GDBN} the name of the core dump file.
10758 * Files:: Commands to specify files
10759 * Separate Debug Files:: Debugging information in separate files
10760 * Symbol Errors:: Errors reading symbol files
10764 @section Commands to specify files
10766 @cindex symbol table
10767 @cindex core dump file
10769 You may want to specify executable and core dump file names. The usual
10770 way to do this is at start-up time, using the arguments to
10771 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
10772 Out of @value{GDBN}}).
10774 Occasionally it is necessary to change to a different file during a
10775 @value{GDBN} session. Or you may run @value{GDBN} and forget to
10776 specify a file you want to use. Or you are debugging a remote target
10777 via @code{gdbserver} (@pxref{Server, file}). In these situations the
10778 @value{GDBN} commands to specify new files are useful.
10781 @cindex executable file
10783 @item file @var{filename}
10784 Use @var{filename} as the program to be debugged. It is read for its
10785 symbols and for the contents of pure memory. It is also the program
10786 executed when you use the @code{run} command. If you do not specify a
10787 directory and the file is not found in the @value{GDBN} working directory,
10788 @value{GDBN} uses the environment variable @code{PATH} as a list of
10789 directories to search, just as the shell does when looking for a program
10790 to run. You can change the value of this variable, for both @value{GDBN}
10791 and your program, using the @code{path} command.
10793 @cindex unlinked object files
10794 @cindex patching object files
10795 You can load unlinked object @file{.o} files into @value{GDBN} using
10796 the @code{file} command. You will not be able to ``run'' an object
10797 file, but you can disassemble functions and inspect variables. Also,
10798 if the underlying BFD functionality supports it, you could use
10799 @kbd{gdb -write} to patch object files using this technique. Note
10800 that @value{GDBN} can neither interpret nor modify relocations in this
10801 case, so branches and some initialized variables will appear to go to
10802 the wrong place. But this feature is still handy from time to time.
10805 @code{file} with no argument makes @value{GDBN} discard any information it
10806 has on both executable file and the symbol table.
10809 @item exec-file @r{[} @var{filename} @r{]}
10810 Specify that the program to be run (but not the symbol table) is found
10811 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
10812 if necessary to locate your program. Omitting @var{filename} means to
10813 discard information on the executable file.
10815 @kindex symbol-file
10816 @item symbol-file @r{[} @var{filename} @r{]}
10817 Read symbol table information from file @var{filename}. @code{PATH} is
10818 searched when necessary. Use the @code{file} command to get both symbol
10819 table and program to run from the same file.
10821 @code{symbol-file} with no argument clears out @value{GDBN} information on your
10822 program's symbol table.
10824 The @code{symbol-file} command causes @value{GDBN} to forget the contents
10825 of its convenience variables, the value history, and all breakpoints and
10826 auto-display expressions. This is because they may contain pointers to
10827 the internal data recording symbols and data types, which are part of
10828 the old symbol table data being discarded inside @value{GDBN}.
10830 @code{symbol-file} does not repeat if you press @key{RET} again after
10833 When @value{GDBN} is configured for a particular environment, it
10834 understands debugging information in whatever format is the standard
10835 generated for that environment; you may use either a @sc{gnu} compiler, or
10836 other compilers that adhere to the local conventions.
10837 Best results are usually obtained from @sc{gnu} compilers; for example,
10838 using @code{@value{GCC}} you can generate debugging information for
10841 For most kinds of object files, with the exception of old SVR3 systems
10842 using COFF, the @code{symbol-file} command does not normally read the
10843 symbol table in full right away. Instead, it scans the symbol table
10844 quickly to find which source files and which symbols are present. The
10845 details are read later, one source file at a time, as they are needed.
10847 The purpose of this two-stage reading strategy is to make @value{GDBN}
10848 start up faster. For the most part, it is invisible except for
10849 occasional pauses while the symbol table details for a particular source
10850 file are being read. (The @code{set verbose} command can turn these
10851 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
10852 warnings and messages}.)
10854 We have not implemented the two-stage strategy for COFF yet. When the
10855 symbol table is stored in COFF format, @code{symbol-file} reads the
10856 symbol table data in full right away. Note that ``stabs-in-COFF''
10857 still does the two-stage strategy, since the debug info is actually
10861 @cindex reading symbols immediately
10862 @cindex symbols, reading immediately
10863 @item symbol-file @var{filename} @r{[} -readnow @r{]}
10864 @itemx file @var{filename} @r{[} -readnow @r{]}
10865 You can override the @value{GDBN} two-stage strategy for reading symbol
10866 tables by using the @samp{-readnow} option with any of the commands that
10867 load symbol table information, if you want to be sure @value{GDBN} has the
10868 entire symbol table available.
10870 @c FIXME: for now no mention of directories, since this seems to be in
10871 @c flux. 13mar1992 status is that in theory GDB would look either in
10872 @c current dir or in same dir as myprog; but issues like competing
10873 @c GDB's, or clutter in system dirs, mean that in practice right now
10874 @c only current dir is used. FFish says maybe a special GDB hierarchy
10875 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
10879 @item core-file @r{[}@var{filename}@r{]}
10881 Specify the whereabouts of a core dump file to be used as the ``contents
10882 of memory''. Traditionally, core files contain only some parts of the
10883 address space of the process that generated them; @value{GDBN} can access the
10884 executable file itself for other parts.
10886 @code{core-file} with no argument specifies that no core file is
10889 Note that the core file is ignored when your program is actually running
10890 under @value{GDBN}. So, if you have been running your program and you
10891 wish to debug a core file instead, you must kill the subprocess in which
10892 the program is running. To do this, use the @code{kill} command
10893 (@pxref{Kill Process, ,Killing the child process}).
10895 @kindex add-symbol-file
10896 @cindex dynamic linking
10897 @item add-symbol-file @var{filename} @var{address}
10898 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
10899 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
10900 The @code{add-symbol-file} command reads additional symbol table
10901 information from the file @var{filename}. You would use this command
10902 when @var{filename} has been dynamically loaded (by some other means)
10903 into the program that is running. @var{address} should be the memory
10904 address at which the file has been loaded; @value{GDBN} cannot figure
10905 this out for itself. You can additionally specify an arbitrary number
10906 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
10907 section name and base address for that section. You can specify any
10908 @var{address} as an expression.
10910 The symbol table of the file @var{filename} is added to the symbol table
10911 originally read with the @code{symbol-file} command. You can use the
10912 @code{add-symbol-file} command any number of times; the new symbol data
10913 thus read keeps adding to the old. To discard all old symbol data
10914 instead, use the @code{symbol-file} command without any arguments.
10916 @cindex relocatable object files, reading symbols from
10917 @cindex object files, relocatable, reading symbols from
10918 @cindex reading symbols from relocatable object files
10919 @cindex symbols, reading from relocatable object files
10920 @cindex @file{.o} files, reading symbols from
10921 Although @var{filename} is typically a shared library file, an
10922 executable file, or some other object file which has been fully
10923 relocated for loading into a process, you can also load symbolic
10924 information from relocatable @file{.o} files, as long as:
10928 the file's symbolic information refers only to linker symbols defined in
10929 that file, not to symbols defined by other object files,
10931 every section the file's symbolic information refers to has actually
10932 been loaded into the inferior, as it appears in the file, and
10934 you can determine the address at which every section was loaded, and
10935 provide these to the @code{add-symbol-file} command.
10939 Some embedded operating systems, like Sun Chorus and VxWorks, can load
10940 relocatable files into an already running program; such systems
10941 typically make the requirements above easy to meet. However, it's
10942 important to recognize that many native systems use complex link
10943 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
10944 assembly, for example) that make the requirements difficult to meet. In
10945 general, one cannot assume that using @code{add-symbol-file} to read a
10946 relocatable object file's symbolic information will have the same effect
10947 as linking the relocatable object file into the program in the normal
10950 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
10952 @kindex add-symbol-file-from-memory
10953 @cindex @code{syscall DSO}
10954 @cindex load symbols from memory
10955 @item add-symbol-file-from-memory @var{address}
10956 Load symbols from the given @var{address} in a dynamically loaded
10957 object file whose image is mapped directly into the inferior's memory.
10958 For example, the Linux kernel maps a @code{syscall DSO} into each
10959 process's address space; this DSO provides kernel-specific code for
10960 some system calls. The argument can be any expression whose
10961 evaluation yields the address of the file's shared object file header.
10962 For this command to work, you must have used @code{symbol-file} or
10963 @code{exec-file} commands in advance.
10965 @kindex add-shared-symbol-files
10967 @item add-shared-symbol-files @var{library-file}
10968 @itemx assf @var{library-file}
10969 The @code{add-shared-symbol-files} command can currently be used only
10970 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
10971 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
10972 @value{GDBN} automatically looks for shared libraries, however if
10973 @value{GDBN} does not find yours, you can invoke
10974 @code{add-shared-symbol-files}. It takes one argument: the shared
10975 library's file name. @code{assf} is a shorthand alias for
10976 @code{add-shared-symbol-files}.
10979 @item section @var{section} @var{addr}
10980 The @code{section} command changes the base address of the named
10981 @var{section} of the exec file to @var{addr}. This can be used if the
10982 exec file does not contain section addresses, (such as in the
10983 @code{a.out} format), or when the addresses specified in the file
10984 itself are wrong. Each section must be changed separately. The
10985 @code{info files} command, described below, lists all the sections and
10989 @kindex info target
10992 @code{info files} and @code{info target} are synonymous; both print the
10993 current target (@pxref{Targets, ,Specifying a Debugging Target}),
10994 including the names of the executable and core dump files currently in
10995 use by @value{GDBN}, and the files from which symbols were loaded. The
10996 command @code{help target} lists all possible targets rather than
10999 @kindex maint info sections
11000 @item maint info sections
11001 Another command that can give you extra information about program sections
11002 is @code{maint info sections}. In addition to the section information
11003 displayed by @code{info files}, this command displays the flags and file
11004 offset of each section in the executable and core dump files. In addition,
11005 @code{maint info sections} provides the following command options (which
11006 may be arbitrarily combined):
11010 Display sections for all loaded object files, including shared libraries.
11011 @item @var{sections}
11012 Display info only for named @var{sections}.
11013 @item @var{section-flags}
11014 Display info only for sections for which @var{section-flags} are true.
11015 The section flags that @value{GDBN} currently knows about are:
11018 Section will have space allocated in the process when loaded.
11019 Set for all sections except those containing debug information.
11021 Section will be loaded from the file into the child process memory.
11022 Set for pre-initialized code and data, clear for @code{.bss} sections.
11024 Section needs to be relocated before loading.
11026 Section cannot be modified by the child process.
11028 Section contains executable code only.
11030 Section contains data only (no executable code).
11032 Section will reside in ROM.
11034 Section contains data for constructor/destructor lists.
11036 Section is not empty.
11038 An instruction to the linker to not output the section.
11039 @item COFF_SHARED_LIBRARY
11040 A notification to the linker that the section contains
11041 COFF shared library information.
11043 Section contains common symbols.
11046 @kindex set trust-readonly-sections
11047 @cindex read-only sections
11048 @item set trust-readonly-sections on
11049 Tell @value{GDBN} that readonly sections in your object file
11050 really are read-only (i.e.@: that their contents will not change).
11051 In that case, @value{GDBN} can fetch values from these sections
11052 out of the object file, rather than from the target program.
11053 For some targets (notably embedded ones), this can be a significant
11054 enhancement to debugging performance.
11056 The default is off.
11058 @item set trust-readonly-sections off
11059 Tell @value{GDBN} not to trust readonly sections. This means that
11060 the contents of the section might change while the program is running,
11061 and must therefore be fetched from the target when needed.
11063 @item show trust-readonly-sections
11064 Show the current setting of trusting readonly sections.
11067 All file-specifying commands allow both absolute and relative file names
11068 as arguments. @value{GDBN} always converts the file name to an absolute file
11069 name and remembers it that way.
11071 @cindex shared libraries
11072 @value{GDBN} supports GNU/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
11073 and IBM RS/6000 AIX shared libraries.
11075 @value{GDBN} automatically loads symbol definitions from shared libraries
11076 when you use the @code{run} command, or when you examine a core file.
11077 (Before you issue the @code{run} command, @value{GDBN} does not understand
11078 references to a function in a shared library, however---unless you are
11079 debugging a core file).
11081 On HP-UX, if the program loads a library explicitly, @value{GDBN}
11082 automatically loads the symbols at the time of the @code{shl_load} call.
11084 @c FIXME: some @value{GDBN} release may permit some refs to undef
11085 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
11086 @c FIXME...lib; check this from time to time when updating manual
11088 There are times, however, when you may wish to not automatically load
11089 symbol definitions from shared libraries, such as when they are
11090 particularly large or there are many of them.
11092 To control the automatic loading of shared library symbols, use the
11096 @kindex set auto-solib-add
11097 @item set auto-solib-add @var{mode}
11098 If @var{mode} is @code{on}, symbols from all shared object libraries
11099 will be loaded automatically when the inferior begins execution, you
11100 attach to an independently started inferior, or when the dynamic linker
11101 informs @value{GDBN} that a new library has been loaded. If @var{mode}
11102 is @code{off}, symbols must be loaded manually, using the
11103 @code{sharedlibrary} command. The default value is @code{on}.
11105 @cindex memory used for symbol tables
11106 If your program uses lots of shared libraries with debug info that
11107 takes large amounts of memory, you can decrease the @value{GDBN}
11108 memory footprint by preventing it from automatically loading the
11109 symbols from shared libraries. To that end, type @kbd{set
11110 auto-solib-add off} before running the inferior, then load each
11111 library whose debug symbols you do need with @kbd{sharedlibrary
11112 @var{regexp}}, where @var{regexp} is a regular expresion that matches
11113 the libraries whose symbols you want to be loaded.
11115 @kindex show auto-solib-add
11116 @item show auto-solib-add
11117 Display the current autoloading mode.
11120 @cindex load shared library
11121 To explicitly load shared library symbols, use the @code{sharedlibrary}
11125 @kindex info sharedlibrary
11128 @itemx info sharedlibrary
11129 Print the names of the shared libraries which are currently loaded.
11131 @kindex sharedlibrary
11133 @item sharedlibrary @var{regex}
11134 @itemx share @var{regex}
11135 Load shared object library symbols for files matching a
11136 Unix regular expression.
11137 As with files loaded automatically, it only loads shared libraries
11138 required by your program for a core file or after typing @code{run}. If
11139 @var{regex} is omitted all shared libraries required by your program are
11142 @item nosharedlibrary
11143 @kindex nosharedlibrary
11144 @cindex unload symbols from shared libraries
11145 Unload all shared object library symbols. This discards all symbols
11146 that have been loaded from all shared libraries. Symbols from shared
11147 libraries that were loaded by explicit user requests are not
11151 Sometimes you may wish that @value{GDBN} stops and gives you control
11152 when any of shared library events happen. Use the @code{set
11153 stop-on-solib-events} command for this:
11156 @item set stop-on-solib-events
11157 @kindex set stop-on-solib-events
11158 This command controls whether @value{GDBN} should give you control
11159 when the dynamic linker notifies it about some shared library event.
11160 The most common event of interest is loading or unloading of a new
11163 @item show stop-on-solib-events
11164 @kindex show stop-on-solib-events
11165 Show whether @value{GDBN} stops and gives you control when shared
11166 library events happen.
11169 Shared libraries are also supported in many cross or remote debugging
11170 configurations. A copy of the target's libraries need to be present on the
11171 host system; they need to be the same as the target libraries, although the
11172 copies on the target can be stripped as long as the copies on the host are
11175 @cindex where to look for shared libraries
11176 For remote debugging, you need to tell @value{GDBN} where the target
11177 libraries are, so that it can load the correct copies---otherwise, it
11178 may try to load the host's libraries. @value{GDBN} has two variables
11179 to specify the search directories for target libraries.
11182 @cindex prefix for shared library file names
11183 @kindex set solib-absolute-prefix
11184 @item set solib-absolute-prefix @var{path}
11185 If this variable is set, @var{path} will be used as a prefix for any
11186 absolute shared library paths; many runtime loaders store the absolute
11187 paths to the shared library in the target program's memory. If you use
11188 @samp{solib-absolute-prefix} to find shared libraries, they need to be laid
11189 out in the same way that they are on the target, with e.g.@: a
11190 @file{/usr/lib} hierarchy under @var{path}.
11192 @cindex default value of @samp{solib-absolute-prefix}
11193 @cindex @samp{--with-sysroot}
11194 You can set the default value of @samp{solib-absolute-prefix} by using the
11195 configure-time @samp{--with-sysroot} option.
11197 @kindex show solib-absolute-prefix
11198 @item show solib-absolute-prefix
11199 Display the current shared library prefix.
11201 @kindex set solib-search-path
11202 @item set solib-search-path @var{path}
11203 If this variable is set, @var{path} is a colon-separated list of directories
11204 to search for shared libraries. @samp{solib-search-path} is used after
11205 @samp{solib-absolute-prefix} fails to locate the library, or if the path to
11206 the library is relative instead of absolute. If you want to use
11207 @samp{solib-search-path} instead of @samp{solib-absolute-prefix}, be sure to
11208 set @samp{solib-absolute-prefix} to a nonexistant directory to prevent
11209 @value{GDBN} from finding your host's libraries.
11211 @kindex show solib-search-path
11212 @item show solib-search-path
11213 Display the current shared library search path.
11217 @node Separate Debug Files
11218 @section Debugging Information in Separate Files
11219 @cindex separate debugging information files
11220 @cindex debugging information in separate files
11221 @cindex @file{.debug} subdirectories
11222 @cindex debugging information directory, global
11223 @cindex global debugging information directory
11225 @value{GDBN} allows you to put a program's debugging information in a
11226 file separate from the executable itself, in a way that allows
11227 @value{GDBN} to find and load the debugging information automatically.
11228 Since debugging information can be very large --- sometimes larger
11229 than the executable code itself --- some systems distribute debugging
11230 information for their executables in separate files, which users can
11231 install only when they need to debug a problem.
11233 If an executable's debugging information has been extracted to a
11234 separate file, the executable should contain a @dfn{debug link} giving
11235 the name of the debugging information file (with no directory
11236 components), and a checksum of its contents. (The exact form of a
11237 debug link is described below.) If the full name of the directory
11238 containing the executable is @var{execdir}, and the executable has a
11239 debug link that specifies the name @var{debugfile}, then @value{GDBN}
11240 will automatically search for the debugging information file in three
11245 the directory containing the executable file (that is, it will look
11246 for a file named @file{@var{execdir}/@var{debugfile}},
11248 a subdirectory of that directory named @file{.debug} (that is, the
11249 file @file{@var{execdir}/.debug/@var{debugfile}}, and
11251 a subdirectory of the global debug file directory that includes the
11252 executable's full path, and the name from the link (that is, the file
11253 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
11254 @var{globaldebugdir} is the global debug file directory, and
11255 @var{execdir} has been turned into a relative path).
11258 @value{GDBN} checks under each of these names for a debugging
11259 information file whose checksum matches that given in the link, and
11260 reads the debugging information from the first one it finds.
11262 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
11263 which has a link containing the name @file{ls.debug}, and the global
11264 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
11265 for debug information in @file{/usr/bin/ls.debug},
11266 @file{/usr/bin/.debug/ls.debug}, and
11267 @file{/usr/lib/debug/usr/bin/ls.debug}.
11269 You can set the global debugging info directory's name, and view the
11270 name @value{GDBN} is currently using.
11274 @kindex set debug-file-directory
11275 @item set debug-file-directory @var{directory}
11276 Set the directory which @value{GDBN} searches for separate debugging
11277 information files to @var{directory}.
11279 @kindex show debug-file-directory
11280 @item show debug-file-directory
11281 Show the directory @value{GDBN} searches for separate debugging
11286 @cindex @code{.gnu_debuglink} sections
11287 @cindex debug links
11288 A debug link is a special section of the executable file named
11289 @code{.gnu_debuglink}. The section must contain:
11293 A filename, with any leading directory components removed, followed by
11296 zero to three bytes of padding, as needed to reach the next four-byte
11297 boundary within the section, and
11299 a four-byte CRC checksum, stored in the same endianness used for the
11300 executable file itself. The checksum is computed on the debugging
11301 information file's full contents by the function given below, passing
11302 zero as the @var{crc} argument.
11305 Any executable file format can carry a debug link, as long as it can
11306 contain a section named @code{.gnu_debuglink} with the contents
11309 The debugging information file itself should be an ordinary
11310 executable, containing a full set of linker symbols, sections, and
11311 debugging information. The sections of the debugging information file
11312 should have the same names, addresses and sizes as the original file,
11313 but they need not contain any data --- much like a @code{.bss} section
11314 in an ordinary executable.
11316 As of December 2002, there is no standard GNU utility to produce
11317 separated executable / debugging information file pairs. Ulrich
11318 Drepper's @file{elfutils} package, starting with version 0.53,
11319 contains a version of the @code{strip} command such that the command
11320 @kbd{strip foo -f foo.debug} removes the debugging information from
11321 the executable file @file{foo}, places it in the file
11322 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
11324 Since there are many different ways to compute CRC's (different
11325 polynomials, reversals, byte ordering, etc.), the simplest way to
11326 describe the CRC used in @code{.gnu_debuglink} sections is to give the
11327 complete code for a function that computes it:
11329 @kindex gnu_debuglink_crc32
11332 gnu_debuglink_crc32 (unsigned long crc,
11333 unsigned char *buf, size_t len)
11335 static const unsigned long crc32_table[256] =
11337 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
11338 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
11339 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
11340 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
11341 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
11342 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
11343 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
11344 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
11345 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
11346 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
11347 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
11348 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
11349 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
11350 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
11351 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
11352 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
11353 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
11354 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
11355 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
11356 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
11357 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
11358 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
11359 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
11360 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
11361 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
11362 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
11363 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
11364 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
11365 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
11366 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
11367 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
11368 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
11369 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
11370 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
11371 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
11372 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
11373 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
11374 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
11375 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
11376 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
11377 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
11378 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
11379 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
11380 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
11381 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
11382 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
11383 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
11384 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
11385 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
11386 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
11387 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
11390 unsigned char *end;
11392 crc = ~crc & 0xffffffff;
11393 for (end = buf + len; buf < end; ++buf)
11394 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
11395 return ~crc & 0xffffffff;
11400 @node Symbol Errors
11401 @section Errors reading symbol files
11403 While reading a symbol file, @value{GDBN} occasionally encounters problems,
11404 such as symbol types it does not recognize, or known bugs in compiler
11405 output. By default, @value{GDBN} does not notify you of such problems, since
11406 they are relatively common and primarily of interest to people
11407 debugging compilers. If you are interested in seeing information
11408 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
11409 only one message about each such type of problem, no matter how many
11410 times the problem occurs; or you can ask @value{GDBN} to print more messages,
11411 to see how many times the problems occur, with the @code{set
11412 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
11415 The messages currently printed, and their meanings, include:
11418 @item inner block not inside outer block in @var{symbol}
11420 The symbol information shows where symbol scopes begin and end
11421 (such as at the start of a function or a block of statements). This
11422 error indicates that an inner scope block is not fully contained
11423 in its outer scope blocks.
11425 @value{GDBN} circumvents the problem by treating the inner block as if it had
11426 the same scope as the outer block. In the error message, @var{symbol}
11427 may be shown as ``@code{(don't know)}'' if the outer block is not a
11430 @item block at @var{address} out of order
11432 The symbol information for symbol scope blocks should occur in
11433 order of increasing addresses. This error indicates that it does not
11436 @value{GDBN} does not circumvent this problem, and has trouble
11437 locating symbols in the source file whose symbols it is reading. (You
11438 can often determine what source file is affected by specifying
11439 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
11442 @item bad block start address patched
11444 The symbol information for a symbol scope block has a start address
11445 smaller than the address of the preceding source line. This is known
11446 to occur in the SunOS 4.1.1 (and earlier) C compiler.
11448 @value{GDBN} circumvents the problem by treating the symbol scope block as
11449 starting on the previous source line.
11451 @item bad string table offset in symbol @var{n}
11454 Symbol number @var{n} contains a pointer into the string table which is
11455 larger than the size of the string table.
11457 @value{GDBN} circumvents the problem by considering the symbol to have the
11458 name @code{foo}, which may cause other problems if many symbols end up
11461 @item unknown symbol type @code{0x@var{nn}}
11463 The symbol information contains new data types that @value{GDBN} does
11464 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
11465 uncomprehended information, in hexadecimal.
11467 @value{GDBN} circumvents the error by ignoring this symbol information.
11468 This usually allows you to debug your program, though certain symbols
11469 are not accessible. If you encounter such a problem and feel like
11470 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
11471 on @code{complain}, then go up to the function @code{read_dbx_symtab}
11472 and examine @code{*bufp} to see the symbol.
11474 @item stub type has NULL name
11476 @value{GDBN} could not find the full definition for a struct or class.
11478 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
11479 The symbol information for a C@t{++} member function is missing some
11480 information that recent versions of the compiler should have output for
11483 @item info mismatch between compiler and debugger
11485 @value{GDBN} could not parse a type specification output by the compiler.
11490 @chapter Specifying a Debugging Target
11492 @cindex debugging target
11493 A @dfn{target} is the execution environment occupied by your program.
11495 Often, @value{GDBN} runs in the same host environment as your program;
11496 in that case, the debugging target is specified as a side effect when
11497 you use the @code{file} or @code{core} commands. When you need more
11498 flexibility---for example, running @value{GDBN} on a physically separate
11499 host, or controlling a standalone system over a serial port or a
11500 realtime system over a TCP/IP connection---you can use the @code{target}
11501 command to specify one of the target types configured for @value{GDBN}
11502 (@pxref{Target Commands, ,Commands for managing targets}).
11504 @cindex target architecture
11505 It is possible to build @value{GDBN} for several different @dfn{target
11506 architectures}. When @value{GDBN} is built like that, you can choose
11507 one of the available architectures with the @kbd{set architecture}
11511 @kindex set architecture
11512 @kindex show architecture
11513 @item set architecture @var{arch}
11514 This command sets the current target architecture to @var{arch}. The
11515 value of @var{arch} can be @code{"auto"}, in addition to one of the
11516 supported architectures.
11518 @item show architecture
11519 Show the current target architecture.
11521 @item set processor
11523 @kindex set processor
11524 @kindex show processor
11525 These are alias commands for, respectively, @code{set architecture}
11526 and @code{show architecture}.
11530 * Active Targets:: Active targets
11531 * Target Commands:: Commands for managing targets
11532 * Byte Order:: Choosing target byte order
11533 * Remote:: Remote debugging
11534 * KOD:: Kernel Object Display
11538 @node Active Targets
11539 @section Active targets
11541 @cindex stacking targets
11542 @cindex active targets
11543 @cindex multiple targets
11545 There are three classes of targets: processes, core files, and
11546 executable files. @value{GDBN} can work concurrently on up to three
11547 active targets, one in each class. This allows you to (for example)
11548 start a process and inspect its activity without abandoning your work on
11551 For example, if you execute @samp{gdb a.out}, then the executable file
11552 @code{a.out} is the only active target. If you designate a core file as
11553 well---presumably from a prior run that crashed and coredumped---then
11554 @value{GDBN} has two active targets and uses them in tandem, looking
11555 first in the corefile target, then in the executable file, to satisfy
11556 requests for memory addresses. (Typically, these two classes of target
11557 are complementary, since core files contain only a program's
11558 read-write memory---variables and so on---plus machine status, while
11559 executable files contain only the program text and initialized data.)
11561 When you type @code{run}, your executable file becomes an active process
11562 target as well. When a process target is active, all @value{GDBN}
11563 commands requesting memory addresses refer to that target; addresses in
11564 an active core file or executable file target are obscured while the
11565 process target is active.
11567 Use the @code{core-file} and @code{exec-file} commands to select a new
11568 core file or executable target (@pxref{Files, ,Commands to specify
11569 files}). To specify as a target a process that is already running, use
11570 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
11573 @node Target Commands
11574 @section Commands for managing targets
11577 @item target @var{type} @var{parameters}
11578 Connects the @value{GDBN} host environment to a target machine or
11579 process. A target is typically a protocol for talking to debugging
11580 facilities. You use the argument @var{type} to specify the type or
11581 protocol of the target machine.
11583 Further @var{parameters} are interpreted by the target protocol, but
11584 typically include things like device names or host names to connect
11585 with, process numbers, and baud rates.
11587 The @code{target} command does not repeat if you press @key{RET} again
11588 after executing the command.
11590 @kindex help target
11592 Displays the names of all targets available. To display targets
11593 currently selected, use either @code{info target} or @code{info files}
11594 (@pxref{Files, ,Commands to specify files}).
11596 @item help target @var{name}
11597 Describe a particular target, including any parameters necessary to
11600 @kindex set gnutarget
11601 @item set gnutarget @var{args}
11602 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
11603 knows whether it is reading an @dfn{executable},
11604 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
11605 with the @code{set gnutarget} command. Unlike most @code{target} commands,
11606 with @code{gnutarget} the @code{target} refers to a program, not a machine.
11609 @emph{Warning:} To specify a file format with @code{set gnutarget},
11610 you must know the actual BFD name.
11614 @xref{Files, , Commands to specify files}.
11616 @kindex show gnutarget
11617 @item show gnutarget
11618 Use the @code{show gnutarget} command to display what file format
11619 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
11620 @value{GDBN} will determine the file format for each file automatically,
11621 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
11624 @cindex common targets
11625 Here are some common targets (available, or not, depending on the GDB
11630 @item target exec @var{program}
11631 @cindex executable file target
11632 An executable file. @samp{target exec @var{program}} is the same as
11633 @samp{exec-file @var{program}}.
11635 @item target core @var{filename}
11636 @cindex core dump file target
11637 A core dump file. @samp{target core @var{filename}} is the same as
11638 @samp{core-file @var{filename}}.
11640 @item target remote @var{dev}
11641 @cindex remote target
11642 Remote serial target in GDB-specific protocol. The argument @var{dev}
11643 specifies what serial device to use for the connection (e.g.@:
11644 @file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote}
11645 supports the @code{load} command. This is only useful if you have
11646 some other way of getting the stub to the target system, and you can put
11647 it somewhere in memory where it won't get clobbered by the download.
11650 @cindex built-in simulator target
11651 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
11659 works; however, you cannot assume that a specific memory map, device
11660 drivers, or even basic I/O is available, although some simulators do
11661 provide these. For info about any processor-specific simulator details,
11662 see the appropriate section in @ref{Embedded Processors, ,Embedded
11667 Some configurations may include these targets as well:
11671 @item target nrom @var{dev}
11672 @cindex NetROM ROM emulator target
11673 NetROM ROM emulator. This target only supports downloading.
11677 Different targets are available on different configurations of @value{GDBN};
11678 your configuration may have more or fewer targets.
11680 Many remote targets require you to download the executable's code once
11681 you've successfully established a connection. You may wish to control
11682 various aspects of this process, such as the size of the data chunks
11683 used by @value{GDBN} to download program parts to the remote target.
11686 @kindex set download-write-size
11687 @item set download-write-size @var{size}
11688 Set the write size used when downloading a program. Only used when
11689 downloading a program onto a remote target. Specify zero or a
11690 negative value to disable blocked writes. The actual size of each
11691 transfer is also limited by the size of the target packet and the
11694 @kindex show download-write-size
11695 @item show download-write-size
11696 @kindex show download-write-size
11697 Show the current value of the write size.
11700 @kindex set hash@r{, for remote monitors}
11701 @cindex hash mark while downloading
11702 This command controls whether a hash mark @samp{#} is displayed while
11703 downloading a file to the remote monitor. If on, a hash mark is
11704 displayed after each S-record is successfully downloaded to the
11708 @kindex show hash@r{, for remote monitors}
11709 Show the current status of displaying the hash mark.
11711 @item set debug monitor
11712 @kindex set debug monitor
11713 @cindex display remote monitor communications
11714 Enable or disable display of communications messages between
11715 @value{GDBN} and the remote monitor.
11717 @item show debug monitor
11718 @kindex show debug monitor
11719 Show the current status of displaying communications between
11720 @value{GDBN} and the remote monitor.
11725 @kindex load @var{filename}
11726 @item load @var{filename}
11727 Depending on what remote debugging facilities are configured into
11728 @value{GDBN}, the @code{load} command may be available. Where it exists, it
11729 is meant to make @var{filename} (an executable) available for debugging
11730 on the remote system---by downloading, or dynamic linking, for example.
11731 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
11732 the @code{add-symbol-file} command.
11734 If your @value{GDBN} does not have a @code{load} command, attempting to
11735 execute it gets the error message ``@code{You can't do that when your
11736 target is @dots{}}''
11738 The file is loaded at whatever address is specified in the executable.
11739 For some object file formats, you can specify the load address when you
11740 link the program; for other formats, like a.out, the object file format
11741 specifies a fixed address.
11742 @c FIXME! This would be a good place for an xref to the GNU linker doc.
11744 @code{load} does not repeat if you press @key{RET} again after using it.
11748 @section Choosing target byte order
11750 @cindex choosing target byte order
11751 @cindex target byte order
11753 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
11754 offer the ability to run either big-endian or little-endian byte
11755 orders. Usually the executable or symbol will include a bit to
11756 designate the endian-ness, and you will not need to worry about
11757 which to use. However, you may still find it useful to adjust
11758 @value{GDBN}'s idea of processor endian-ness manually.
11762 @item set endian big
11763 Instruct @value{GDBN} to assume the target is big-endian.
11765 @item set endian little
11766 Instruct @value{GDBN} to assume the target is little-endian.
11768 @item set endian auto
11769 Instruct @value{GDBN} to use the byte order associated with the
11773 Display @value{GDBN}'s current idea of the target byte order.
11777 Note that these commands merely adjust interpretation of symbolic
11778 data on the host, and that they have absolutely no effect on the
11782 @section Remote debugging
11783 @cindex remote debugging
11785 If you are trying to debug a program running on a machine that cannot run
11786 @value{GDBN} in the usual way, it is often useful to use remote debugging.
11787 For example, you might use remote debugging on an operating system kernel,
11788 or on a small system which does not have a general purpose operating system
11789 powerful enough to run a full-featured debugger.
11791 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
11792 to make this work with particular debugging targets. In addition,
11793 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
11794 but not specific to any particular target system) which you can use if you
11795 write the remote stubs---the code that runs on the remote system to
11796 communicate with @value{GDBN}.
11798 Other remote targets may be available in your
11799 configuration of @value{GDBN}; use @code{help target} to list them.
11801 Once you've connected to the remote target, @value{GDBN} allows you to
11802 send arbitrary commands to the remote monitor:
11805 @item remote @var{command}
11806 @kindex remote@r{, a command}
11807 @cindex send command to remote monitor
11808 Send an arbitrary @var{command} string to the remote monitor.
11813 @section Kernel Object Display
11814 @cindex kernel object display
11817 Some targets support kernel object display. Using this facility,
11818 @value{GDBN} communicates specially with the underlying operating system
11819 and can display information about operating system-level objects such as
11820 mutexes and other synchronization objects. Exactly which objects can be
11821 displayed is determined on a per-OS basis.
11824 Use the @code{set os} command to set the operating system. This tells
11825 @value{GDBN} which kernel object display module to initialize:
11828 (@value{GDBP}) set os cisco
11832 The associated command @code{show os} displays the operating system
11833 set with the @code{set os} command; if no operating system has been
11834 set, @code{show os} will display an empty string @samp{""}.
11836 If @code{set os} succeeds, @value{GDBN} will display some information
11837 about the operating system, and will create a new @code{info} command
11838 which can be used to query the target. The @code{info} command is named
11839 after the operating system:
11843 (@value{GDBP}) info cisco
11844 List of Cisco Kernel Objects
11846 any Any and all objects
11849 Further subcommands can be used to query about particular objects known
11852 There is currently no way to determine whether a given operating
11853 system is supported other than to try setting it with @kbd{set os
11854 @var{name}}, where @var{name} is the name of the operating system you
11858 @node Remote Debugging
11859 @chapter Debugging remote programs
11862 * Connecting:: Connecting to a remote target
11863 * Server:: Using the gdbserver program
11864 * NetWare:: Using the gdbserve.nlm program
11865 * Remote configuration:: Remote configuration
11866 * remote stub:: Implementing a remote stub
11870 @section Connecting to a remote target
11872 On the @value{GDBN} host machine, you will need an unstripped copy of
11873 your program, since @value{GDBN} needs symobl and debugging information.
11874 Start up @value{GDBN} as usual, using the name of the local copy of your
11875 program as the first argument.
11877 @cindex serial line, @code{target remote}
11878 If you're using a serial line, you may want to give @value{GDBN} the
11879 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
11880 (@pxref{Remote configuration, set remotebaud}) before the
11881 @code{target} command.
11883 After that, use @code{target remote} to establish communications with
11884 the target machine. Its argument specifies how to communicate---either
11885 via a devicename attached to a direct serial line, or a TCP or UDP port
11886 (possibly to a terminal server which in turn has a serial line to the
11887 target). For example, to use a serial line connected to the device
11888 named @file{/dev/ttyb}:
11891 target remote /dev/ttyb
11894 @cindex TCP port, @code{target remote}
11895 To use a TCP connection, use an argument of the form
11896 @code{@var{host}:@var{port}} or @code{tcp:@var{host}:@var{port}}.
11897 For example, to connect to port 2828 on a
11898 terminal server named @code{manyfarms}:
11901 target remote manyfarms:2828
11904 If your remote target is actually running on the same machine as
11905 your debugger session (e.g.@: a simulator of your target running on
11906 the same host), you can omit the hostname. For example, to connect
11907 to port 1234 on your local machine:
11910 target remote :1234
11914 Note that the colon is still required here.
11916 @cindex UDP port, @code{target remote}
11917 To use a UDP connection, use an argument of the form
11918 @code{udp:@var{host}:@var{port}}. For example, to connect to UDP port 2828
11919 on a terminal server named @code{manyfarms}:
11922 target remote udp:manyfarms:2828
11925 When using a UDP connection for remote debugging, you should keep in mind
11926 that the `U' stands for ``Unreliable''. UDP can silently drop packets on
11927 busy or unreliable networks, which will cause havoc with your debugging
11930 Now you can use all the usual commands to examine and change data and to
11931 step and continue the remote program.
11933 @cindex interrupting remote programs
11934 @cindex remote programs, interrupting
11935 Whenever @value{GDBN} is waiting for the remote program, if you type the
11936 interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
11937 program. This may or may not succeed, depending in part on the hardware
11938 and the serial drivers the remote system uses. If you type the
11939 interrupt character once again, @value{GDBN} displays this prompt:
11942 Interrupted while waiting for the program.
11943 Give up (and stop debugging it)? (y or n)
11946 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
11947 (If you decide you want to try again later, you can use @samp{target
11948 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
11949 goes back to waiting.
11952 @kindex detach (remote)
11954 When you have finished debugging the remote program, you can use the
11955 @code{detach} command to release it from @value{GDBN} control.
11956 Detaching from the target normally resumes its execution, but the results
11957 will depend on your particular remote stub. After the @code{detach}
11958 command, @value{GDBN} is free to connect to another target.
11962 The @code{disconnect} command behaves like @code{detach}, except that
11963 the target is generally not resumed. It will wait for @value{GDBN}
11964 (this instance or another one) to connect and continue debugging. After
11965 the @code{disconnect} command, @value{GDBN} is again free to connect to
11968 @cindex send command to remote monitor
11969 @cindex extend @value{GDBN} for remote targets
11970 @cindex add new commands for external monitor
11972 @item monitor @var{cmd}
11973 This command allows you to send arbitrary commands directly to the
11974 remote monitor. Since @value{GDBN} doesn't care about the commands it
11975 sends like this, this command is the way to extend @value{GDBN}---you
11976 can add new commands that only the external monitor will understand
11981 @section Using the @code{gdbserver} program
11984 @cindex remote connection without stubs
11985 @code{gdbserver} is a control program for Unix-like systems, which
11986 allows you to connect your program with a remote @value{GDBN} via
11987 @code{target remote}---but without linking in the usual debugging stub.
11989 @code{gdbserver} is not a complete replacement for the debugging stubs,
11990 because it requires essentially the same operating-system facilities
11991 that @value{GDBN} itself does. In fact, a system that can run
11992 @code{gdbserver} to connect to a remote @value{GDBN} could also run
11993 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
11994 because it is a much smaller program than @value{GDBN} itself. It is
11995 also easier to port than all of @value{GDBN}, so you may be able to get
11996 started more quickly on a new system by using @code{gdbserver}.
11997 Finally, if you develop code for real-time systems, you may find that
11998 the tradeoffs involved in real-time operation make it more convenient to
11999 do as much development work as possible on another system, for example
12000 by cross-compiling. You can use @code{gdbserver} to make a similar
12001 choice for debugging.
12003 @value{GDBN} and @code{gdbserver} communicate via either a serial line
12004 or a TCP connection, using the standard @value{GDBN} remote serial
12008 @item On the target machine,
12009 you need to have a copy of the program you want to debug.
12010 @code{gdbserver} does not need your program's symbol table, so you can
12011 strip the program if necessary to save space. @value{GDBN} on the host
12012 system does all the symbol handling.
12014 To use the server, you must tell it how to communicate with @value{GDBN};
12015 the name of your program; and the arguments for your program. The usual
12019 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
12022 @var{comm} is either a device name (to use a serial line) or a TCP
12023 hostname and portnumber. For example, to debug Emacs with the argument
12024 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
12028 target> gdbserver /dev/com1 emacs foo.txt
12031 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
12034 To use a TCP connection instead of a serial line:
12037 target> gdbserver host:2345 emacs foo.txt
12040 The only difference from the previous example is the first argument,
12041 specifying that you are communicating with the host @value{GDBN} via
12042 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
12043 expect a TCP connection from machine @samp{host} to local TCP port 2345.
12044 (Currently, the @samp{host} part is ignored.) You can choose any number
12045 you want for the port number as long as it does not conflict with any
12046 TCP ports already in use on the target system (for example, @code{23} is
12047 reserved for @code{telnet}).@footnote{If you choose a port number that
12048 conflicts with another service, @code{gdbserver} prints an error message
12049 and exits.} You must use the same port number with the host @value{GDBN}
12050 @code{target remote} command.
12052 On some targets, @code{gdbserver} can also attach to running programs.
12053 This is accomplished via the @code{--attach} argument. The syntax is:
12056 target> gdbserver @var{comm} --attach @var{pid}
12059 @var{pid} is the process ID of a currently running process. It isn't necessary
12060 to point @code{gdbserver} at a binary for the running process.
12063 @cindex attach to a program by name
12064 You can debug processes by name instead of process ID if your target has the
12065 @code{pidof} utility:
12068 target> gdbserver @var{comm} --attach `pidof @var{PROGRAM}`
12071 In case more than one copy of @var{PROGRAM} is running, or @var{PROGRAM}
12072 has multiple threads, most versions of @code{pidof} support the
12073 @code{-s} option to only return the first process ID.
12075 @item On the host machine,
12076 connect to your target (@pxref{Connecting,,Connecting to a remote target}).
12077 For TCP connections, you must start up @code{gdbserver} prior to using
12078 the @code{target remote} command. Otherwise you may get an error whose
12079 text depends on the host system, but which usually looks something like
12080 @samp{Connection refused}. You don't need to use the @code{load}
12081 command in @value{GDBN} when using @code{gdbserver}, since the program is
12082 already on the target. However, if you want to load the symbols (as
12083 you normally would), do that with the @code{file} command, and issue
12084 it @emph{before} connecting to the server; otherwise, you will get an
12085 error message saying @code{"Program is already running"}, since the
12086 program is considered running after the connection.
12091 @section Using the @code{gdbserve.nlm} program
12093 @kindex gdbserve.nlm
12094 @code{gdbserve.nlm} is a control program for NetWare systems, which
12095 allows you to connect your program with a remote @value{GDBN} via
12096 @code{target remote}.
12098 @value{GDBN} and @code{gdbserve.nlm} communicate via a serial line,
12099 using the standard @value{GDBN} remote serial protocol.
12102 @item On the target machine,
12103 you need to have a copy of the program you want to debug.
12104 @code{gdbserve.nlm} does not need your program's symbol table, so you
12105 can strip the program if necessary to save space. @value{GDBN} on the
12106 host system does all the symbol handling.
12108 To use the server, you must tell it how to communicate with
12109 @value{GDBN}; the name of your program; and the arguments for your
12110 program. The syntax is:
12113 load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ]
12114 [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ]
12117 @var{board} and @var{port} specify the serial line; @var{baud} specifies
12118 the baud rate used by the connection. @var{port} and @var{node} default
12119 to 0, @var{baud} defaults to 9600@dmn{bps}.
12121 For example, to debug Emacs with the argument @samp{foo.txt}and
12122 communicate with @value{GDBN} over serial port number 2 or board 1
12123 using a 19200@dmn{bps} connection:
12126 load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
12130 On the @value{GDBN} host machine, connect to your target (@pxref{Connecting,,
12131 Connecting to a remote target}).
12135 @node Remote configuration
12136 @section Remote configuration
12139 @kindex show remote
12140 This section documents the configuration options available when
12141 debugging remote programs. For the options related to the File I/O
12142 extensions of the remote protocol, see @ref{The system call,
12143 system-call-allowed}.
12146 @item set remoteaddresssize @var{bits}
12147 @cindex adress size for remote targets
12148 @cindex bits in remote address
12149 Set the maximum size of address in a memory packet to the specified
12150 number of bits. @value{GDBN} will mask off the address bits above
12151 that number, when it passes addresses to the remote target. The
12152 default value is the number of bits in the target's address.
12154 @item show remoteaddresssize
12155 Show the current value of remote address size in bits.
12157 @item set remotebaud @var{n}
12158 @cindex baud rate for remote targets
12159 Set the baud rate for the remote serial I/O to @var{n} baud. The
12160 value is used to set the speed of the serial port used for debugging
12163 @item show remotebaud
12164 Show the current speed of the remote connection.
12166 @item set remotebreak
12167 @cindex interrupt remote programs
12168 @cindex BREAK signal instead of Ctrl-C
12169 @anchor{set remotebreak}
12170 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
12171 when you press the @key{Ctrl-C} key to interrupt the program running
12172 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
12173 character instead. The default is off, since most remote systems
12174 expect to see @samp{Ctrl-C} as the interrupt signal.
12176 @item show remotebreak
12177 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
12178 interrupt the remote program.
12180 @item set remotedebug
12181 @cindex debug remote protocol
12182 @cindex remote protocol debugging
12183 @cindex display remote packets
12184 Control the debugging of the remote protocol. When enabled, each
12185 packet sent to or received from the remote target is displayed. The
12188 @item show remotedebug
12189 Show the current setting of the remote protocol debugging.
12191 @item set remotedevice @var{device}
12192 @cindex serial port name
12193 Set the name of the serial port through which to communicate to the
12194 remote target to @var{device}. This is the device used by
12195 @value{GDBN} to open the serial communications line to the remote
12196 target. There's no default, so you must set a valid port name for the
12197 remote serial communications to work. (Some varieties of the
12198 @code{target} command accept the port name as part of their
12201 @item show remotedevice
12202 Show the current name of the serial port.
12204 @item set remotelogbase @var{base}
12205 Set the base (a.k.a.@: radix) of logging serial protocol
12206 communications to @var{base}. Supported values of @var{base} are:
12207 @code{ascii}, @code{octal}, and @code{hex}. The default is
12210 @item show remotelogbase
12211 Show the current setting of the radix for logging remote serial
12214 @item set remotelogfile @var{file}
12215 @cindex record serial communications on file
12216 Record remote serial communications on the named @var{file}. The
12217 default is not to record at all.
12219 @item show remotelogfile.
12220 Show the current setting of the file name on which to record the
12221 serial communications.
12223 @item set remotetimeout @var{num}
12224 @cindex timeout for serial communications
12225 @cindex remote timeout
12226 Set the timeout limit to wait for the remote target to respond to
12227 @var{num} seconds. The default is 2 seconds.
12229 @item show remotetimeout
12230 Show the current number of seconds to wait for the remote target
12233 @cindex limit hardware breakpoints and watchpoints
12234 @cindex remote target, limit break- and watchpoints
12235 @anchor{set remote hardware-watchpoint-limit}
12236 @anchor{set remote hardware-breakpoint-limit}
12237 @item set remote hardware-watchpoint-limit @var{limit}
12238 @itemx set remote hardware-breakpoint-limit @var{limit}
12239 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
12240 watchpoints. A limit of -1, the default, is treated as unlimited.
12242 @item set remote fetch-register-packet
12243 @itemx set remote set-register-packet
12244 @itemx set remote P-packet
12245 @itemx set remote p-packet
12247 @cindex fetch registers from remote targets
12248 @cindex set registers in remote targets
12249 Determine whether @value{GDBN} can set and fetch registers from the
12250 remote target using the @samp{P} packets. The default depends on the
12251 remote stub's support of the @samp{P} packets (@value{GDBN} queries
12252 the stub when this packet is first required).
12254 @item show remote fetch-register-packet
12255 @itemx show remote set-register-packet
12256 @itemx show remote P-packet
12257 @itemx show remote p-packet
12258 Show the current setting of using the @samp{P} packets for setting and
12259 fetching registers from the remote target.
12261 @cindex binary downloads
12263 @item set remote binary-download-packet
12264 @itemx set remote X-packet
12265 Determine whether @value{GDBN} sends downloads in binary mode using
12266 the @samp{X} packets. The default is on.
12268 @item show remote binary-download-packet
12269 @itemx show remote X-packet
12270 Show the current setting of using the @samp{X} packets for binary
12273 @item set remote read-aux-vector-packet
12274 @cindex auxiliary vector of remote target
12275 @cindex @code{auxv}, and remote targets
12276 Set the use of the remote protocol's @samp{qPart:auxv:read} (target
12277 auxiliary vector read) request. This request is used to fetch the
12278 remote target's @dfn{auxiliary vector}, see @ref{OS Information,
12279 Auxiliary Vector}. The default setting depends on the remote stub's
12280 support of this request (@value{GDBN} queries the stub when this
12281 request is first required). @xref{General Query Packets, qPart}, for
12282 more information about this request.
12284 @item show remote read-aux-vector-packet
12285 Show the current setting of use of the @samp{qPart:auxv:read} request.
12287 @item set remote symbol-lookup-packet
12288 @cindex remote symbol lookup request
12289 Set the use of the remote protocol's @samp{qSymbol} (target symbol
12290 lookup) request. This request is used to communicate symbol
12291 information to the remote target, e.g., whenever a new shared library
12292 is loaded by the remote (@pxref{Files, shared libraries}). The
12293 default setting depends on the remote stub's support of this request
12294 (@value{GDBN} queries the stub when this request is first required).
12295 @xref{General Query Packets, qSymbol}, for more information about this
12298 @item show remote symbol-lookup-packet
12299 Show the current setting of use of the @samp{qSymbol} request.
12301 @item set remote verbose-resume-packet
12302 @cindex resume remote target
12303 @cindex signal thread, and remote targets
12304 @cindex single-step thread, and remote targets
12305 @cindex thread-specific operations on remote targets
12306 Set the use of the remote protocol's @samp{vCont} (descriptive resume)
12307 request. This request is used to resume specific threads in the
12308 remote target, and to single-step or signal them. The default setting
12309 depends on the remote stub's support of this request (@value{GDBN}
12310 queries the stub when this request is first required). This setting
12311 affects debugging of multithreaded programs: if @samp{vCont} cannot be
12312 used, @value{GDBN} might be unable to single-step a specific thread,
12313 especially under @code{set scheduler-locking off}; it is also
12314 impossible to pause a specific thread. @xref{Packets, vCont}, for
12317 @item show remote verbose-resume-packet
12318 Show the current setting of use of the @samp{vCont} request
12320 @item set remote software-breakpoint-packet
12321 @itemx set remote hardware-breakpoint-packet
12322 @itemx set remote write-watchpoint-packet
12323 @itemx set remote read-watchpoint-packet
12324 @itemx set remote access-watchpoint-packet
12325 @itemx set remote Z-packet
12327 @cindex remote hardware breakpoints and watchpoints
12328 These commands enable or disable the use of @samp{Z} packets for
12329 setting breakpoints and watchpoints in the remote target. The default
12330 depends on the remote stub's support of the @samp{Z} packets
12331 (@value{GDBN} queries the stub when each packet is first required).
12332 The command @code{set remote Z-packet}, kept for back-compatibility,
12333 turns on or off all the features that require the use of @samp{Z}
12336 @item show remote software-breakpoint-packet
12337 @itemx show remote hardware-breakpoint-packet
12338 @itemx show remote write-watchpoint-packet
12339 @itemx show remote read-watchpoint-packet
12340 @itemx show remote access-watchpoint-packet
12341 @itemx show remote Z-packet
12342 Show the current setting of @samp{Z} packets usage.
12344 @item set remote get-thread-local-storage-address
12345 @kindex set remote get-thread-local-storage-address
12346 @cindex thread local storage of remote targets
12347 This command enables or disables the use of the @samp{qGetTLSAddr}
12348 (Get Thread Local Storage Address) request packet. The default
12349 depends on whether the remote stub supports this request.
12350 @xref{General Query Packets, qGetTLSAddr}, for more details about this
12353 @item show remote get-thread-local-storage-address
12354 @kindex show remote get-thread-local-storage-address
12355 Show the current setting of @samp{qGetTLSAddr} packet usage.
12359 @section Implementing a remote stub
12361 @cindex debugging stub, example
12362 @cindex remote stub, example
12363 @cindex stub example, remote debugging
12364 The stub files provided with @value{GDBN} implement the target side of the
12365 communication protocol, and the @value{GDBN} side is implemented in the
12366 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
12367 these subroutines to communicate, and ignore the details. (If you're
12368 implementing your own stub file, you can still ignore the details: start
12369 with one of the existing stub files. @file{sparc-stub.c} is the best
12370 organized, and therefore the easiest to read.)
12372 @cindex remote serial debugging, overview
12373 To debug a program running on another machine (the debugging
12374 @dfn{target} machine), you must first arrange for all the usual
12375 prerequisites for the program to run by itself. For example, for a C
12380 A startup routine to set up the C runtime environment; these usually
12381 have a name like @file{crt0}. The startup routine may be supplied by
12382 your hardware supplier, or you may have to write your own.
12385 A C subroutine library to support your program's
12386 subroutine calls, notably managing input and output.
12389 A way of getting your program to the other machine---for example, a
12390 download program. These are often supplied by the hardware
12391 manufacturer, but you may have to write your own from hardware
12395 The next step is to arrange for your program to use a serial port to
12396 communicate with the machine where @value{GDBN} is running (the @dfn{host}
12397 machine). In general terms, the scheme looks like this:
12401 @value{GDBN} already understands how to use this protocol; when everything
12402 else is set up, you can simply use the @samp{target remote} command
12403 (@pxref{Targets,,Specifying a Debugging Target}).
12405 @item On the target,
12406 you must link with your program a few special-purpose subroutines that
12407 implement the @value{GDBN} remote serial protocol. The file containing these
12408 subroutines is called a @dfn{debugging stub}.
12410 On certain remote targets, you can use an auxiliary program
12411 @code{gdbserver} instead of linking a stub into your program.
12412 @xref{Server,,Using the @code{gdbserver} program}, for details.
12415 The debugging stub is specific to the architecture of the remote
12416 machine; for example, use @file{sparc-stub.c} to debug programs on
12419 @cindex remote serial stub list
12420 These working remote stubs are distributed with @value{GDBN}:
12425 @cindex @file{i386-stub.c}
12428 For Intel 386 and compatible architectures.
12431 @cindex @file{m68k-stub.c}
12432 @cindex Motorola 680x0
12434 For Motorola 680x0 architectures.
12437 @cindex @file{sh-stub.c}
12440 For Renesas SH architectures.
12443 @cindex @file{sparc-stub.c}
12445 For @sc{sparc} architectures.
12447 @item sparcl-stub.c
12448 @cindex @file{sparcl-stub.c}
12451 For Fujitsu @sc{sparclite} architectures.
12455 The @file{README} file in the @value{GDBN} distribution may list other
12456 recently added stubs.
12459 * Stub Contents:: What the stub can do for you
12460 * Bootstrapping:: What you must do for the stub
12461 * Debug Session:: Putting it all together
12464 @node Stub Contents
12465 @subsection What the stub can do for you
12467 @cindex remote serial stub
12468 The debugging stub for your architecture supplies these three
12472 @item set_debug_traps
12473 @findex set_debug_traps
12474 @cindex remote serial stub, initialization
12475 This routine arranges for @code{handle_exception} to run when your
12476 program stops. You must call this subroutine explicitly near the
12477 beginning of your program.
12479 @item handle_exception
12480 @findex handle_exception
12481 @cindex remote serial stub, main routine
12482 This is the central workhorse, but your program never calls it
12483 explicitly---the setup code arranges for @code{handle_exception} to
12484 run when a trap is triggered.
12486 @code{handle_exception} takes control when your program stops during
12487 execution (for example, on a breakpoint), and mediates communications
12488 with @value{GDBN} on the host machine. This is where the communications
12489 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
12490 representative on the target machine. It begins by sending summary
12491 information on the state of your program, then continues to execute,
12492 retrieving and transmitting any information @value{GDBN} needs, until you
12493 execute a @value{GDBN} command that makes your program resume; at that point,
12494 @code{handle_exception} returns control to your own code on the target
12498 @cindex @code{breakpoint} subroutine, remote
12499 Use this auxiliary subroutine to make your program contain a
12500 breakpoint. Depending on the particular situation, this may be the only
12501 way for @value{GDBN} to get control. For instance, if your target
12502 machine has some sort of interrupt button, you won't need to call this;
12503 pressing the interrupt button transfers control to
12504 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
12505 simply receiving characters on the serial port may also trigger a trap;
12506 again, in that situation, you don't need to call @code{breakpoint} from
12507 your own program---simply running @samp{target remote} from the host
12508 @value{GDBN} session gets control.
12510 Call @code{breakpoint} if none of these is true, or if you simply want
12511 to make certain your program stops at a predetermined point for the
12512 start of your debugging session.
12515 @node Bootstrapping
12516 @subsection What you must do for the stub
12518 @cindex remote stub, support routines
12519 The debugging stubs that come with @value{GDBN} are set up for a particular
12520 chip architecture, but they have no information about the rest of your
12521 debugging target machine.
12523 First of all you need to tell the stub how to communicate with the
12527 @item int getDebugChar()
12528 @findex getDebugChar
12529 Write this subroutine to read a single character from the serial port.
12530 It may be identical to @code{getchar} for your target system; a
12531 different name is used to allow you to distinguish the two if you wish.
12533 @item void putDebugChar(int)
12534 @findex putDebugChar
12535 Write this subroutine to write a single character to the serial port.
12536 It may be identical to @code{putchar} for your target system; a
12537 different name is used to allow you to distinguish the two if you wish.
12540 @cindex control C, and remote debugging
12541 @cindex interrupting remote targets
12542 If you want @value{GDBN} to be able to stop your program while it is
12543 running, you need to use an interrupt-driven serial driver, and arrange
12544 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
12545 character). That is the character which @value{GDBN} uses to tell the
12546 remote system to stop.
12548 Getting the debugging target to return the proper status to @value{GDBN}
12549 probably requires changes to the standard stub; one quick and dirty way
12550 is to just execute a breakpoint instruction (the ``dirty'' part is that
12551 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
12553 Other routines you need to supply are:
12556 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
12557 @findex exceptionHandler
12558 Write this function to install @var{exception_address} in the exception
12559 handling tables. You need to do this because the stub does not have any
12560 way of knowing what the exception handling tables on your target system
12561 are like (for example, the processor's table might be in @sc{rom},
12562 containing entries which point to a table in @sc{ram}).
12563 @var{exception_number} is the exception number which should be changed;
12564 its meaning is architecture-dependent (for example, different numbers
12565 might represent divide by zero, misaligned access, etc). When this
12566 exception occurs, control should be transferred directly to
12567 @var{exception_address}, and the processor state (stack, registers,
12568 and so on) should be just as it is when a processor exception occurs. So if
12569 you want to use a jump instruction to reach @var{exception_address}, it
12570 should be a simple jump, not a jump to subroutine.
12572 For the 386, @var{exception_address} should be installed as an interrupt
12573 gate so that interrupts are masked while the handler runs. The gate
12574 should be at privilege level 0 (the most privileged level). The
12575 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
12576 help from @code{exceptionHandler}.
12578 @item void flush_i_cache()
12579 @findex flush_i_cache
12580 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
12581 instruction cache, if any, on your target machine. If there is no
12582 instruction cache, this subroutine may be a no-op.
12584 On target machines that have instruction caches, @value{GDBN} requires this
12585 function to make certain that the state of your program is stable.
12589 You must also make sure this library routine is available:
12592 @item void *memset(void *, int, int)
12594 This is the standard library function @code{memset} that sets an area of
12595 memory to a known value. If you have one of the free versions of
12596 @code{libc.a}, @code{memset} can be found there; otherwise, you must
12597 either obtain it from your hardware manufacturer, or write your own.
12600 If you do not use the GNU C compiler, you may need other standard
12601 library subroutines as well; this varies from one stub to another,
12602 but in general the stubs are likely to use any of the common library
12603 subroutines which @code{@value{GCC}} generates as inline code.
12606 @node Debug Session
12607 @subsection Putting it all together
12609 @cindex remote serial debugging summary
12610 In summary, when your program is ready to debug, you must follow these
12615 Make sure you have defined the supporting low-level routines
12616 (@pxref{Bootstrapping,,What you must do for the stub}):
12618 @code{getDebugChar}, @code{putDebugChar},
12619 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
12623 Insert these lines near the top of your program:
12631 For the 680x0 stub only, you need to provide a variable called
12632 @code{exceptionHook}. Normally you just use:
12635 void (*exceptionHook)() = 0;
12639 but if before calling @code{set_debug_traps}, you set it to point to a
12640 function in your program, that function is called when
12641 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
12642 error). The function indicated by @code{exceptionHook} is called with
12643 one parameter: an @code{int} which is the exception number.
12646 Compile and link together: your program, the @value{GDBN} debugging stub for
12647 your target architecture, and the supporting subroutines.
12650 Make sure you have a serial connection between your target machine and
12651 the @value{GDBN} host, and identify the serial port on the host.
12654 @c The "remote" target now provides a `load' command, so we should
12655 @c document that. FIXME.
12656 Download your program to your target machine (or get it there by
12657 whatever means the manufacturer provides), and start it.
12660 Start @value{GDBN} on the host, and connect to the target
12661 (@pxref{Connecting,,Connecting to a remote target}).
12665 @node Configurations
12666 @chapter Configuration-Specific Information
12668 While nearly all @value{GDBN} commands are available for all native and
12669 cross versions of the debugger, there are some exceptions. This chapter
12670 describes things that are only available in certain configurations.
12672 There are three major categories of configurations: native
12673 configurations, where the host and target are the same, embedded
12674 operating system configurations, which are usually the same for several
12675 different processor architectures, and bare embedded processors, which
12676 are quite different from each other.
12681 * Embedded Processors::
12688 This section describes details specific to particular native
12693 * BSD libkvm Interface:: Debugging BSD kernel memory images
12694 * SVR4 Process Information:: SVR4 process information
12695 * DJGPP Native:: Features specific to the DJGPP port
12696 * Cygwin Native:: Features specific to the Cygwin port
12697 * Hurd Native:: Features specific to @sc{gnu} Hurd
12698 * Neutrino:: Features specific to QNX Neutrino
12704 On HP-UX systems, if you refer to a function or variable name that
12705 begins with a dollar sign, @value{GDBN} searches for a user or system
12706 name first, before it searches for a convenience variable.
12709 @node BSD libkvm Interface
12710 @subsection BSD libkvm Interface
12713 @cindex kernel memory image
12714 @cindex kernel crash dump
12716 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
12717 interface that provides a uniform interface for accessing kernel virtual
12718 memory images, including live systems and crash dumps. @value{GDBN}
12719 uses this interface to allow you to debug live kernels and kernel crash
12720 dumps on many native BSD configurations. This is implemented as a
12721 special @code{kvm} debugging target. For debugging a live system, load
12722 the currently running kernel into @value{GDBN} and connect to the
12726 (@value{GDBP}) @b{target kvm}
12729 For debugging crash dumps, provide the file name of the crash dump as an
12733 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
12736 Once connected to the @code{kvm} target, the following commands are
12742 Set current context from the @dfn{Process Control Block} (PCB) address.
12745 Set current context from proc address. This command isn't available on
12746 modern FreeBSD systems.
12749 @node SVR4 Process Information
12750 @subsection SVR4 process information
12752 @cindex examine process image
12753 @cindex process info via @file{/proc}
12755 Many versions of SVR4 and compatible systems provide a facility called
12756 @samp{/proc} that can be used to examine the image of a running
12757 process using file-system subroutines. If @value{GDBN} is configured
12758 for an operating system with this facility, the command @code{info
12759 proc} is available to report information about the process running
12760 your program, or about any process running on your system. @code{info
12761 proc} works only on SVR4 systems that include the @code{procfs} code.
12762 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
12763 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
12769 @itemx info proc @var{process-id}
12770 Summarize available information about any running process. If a
12771 process ID is specified by @var{process-id}, display information about
12772 that process; otherwise display information about the program being
12773 debugged. The summary includes the debugged process ID, the command
12774 line used to invoke it, its current working directory, and its
12775 executable file's absolute file name.
12777 On some systems, @var{process-id} can be of the form
12778 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
12779 within a process. If the optional @var{pid} part is missing, it means
12780 a thread from the process being debugged (the leading @samp{/} still
12781 needs to be present, or else @value{GDBN} will interpret the number as
12782 a process ID rather than a thread ID).
12784 @item info proc mappings
12785 @cindex memory address space mappings
12786 Report the memory address space ranges accessible in the program, with
12787 information on whether the process has read, write, or execute access
12788 rights to each range. On @sc{gnu}/Linux systems, each memory range
12789 includes the object file which is mapped to that range, instead of the
12790 memory access rights to that range.
12792 @item info proc stat
12793 @itemx info proc status
12794 @cindex process detailed status information
12795 These subcommands are specific to @sc{gnu}/Linux systems. They show
12796 the process-related information, including the user ID and group ID;
12797 how many threads are there in the process; its virtual memory usage;
12798 the signals that are pending, blocked, and ignored; its TTY; its
12799 consumption of system and user time; its stack size; its @samp{nice}
12800 value; etc. For more information, see the @samp{proc} man page
12801 (type @kbd{man 5 proc} from your shell prompt).
12803 @item info proc all
12804 Show all the information about the process described under all of the
12805 above @code{info proc} subcommands.
12808 @comment These sub-options of 'info proc' were not included when
12809 @comment procfs.c was re-written. Keep their descriptions around
12810 @comment against the day when someone finds the time to put them back in.
12811 @kindex info proc times
12812 @item info proc times
12813 Starting time, user CPU time, and system CPU time for your program and
12816 @kindex info proc id
12818 Report on the process IDs related to your program: its own process ID,
12819 the ID of its parent, the process group ID, and the session ID.
12822 @item set procfs-trace
12823 @kindex set procfs-trace
12824 @cindex @code{procfs} API calls
12825 This command enables and disables tracing of @code{procfs} API calls.
12827 @item show procfs-trace
12828 @kindex show procfs-trace
12829 Show the current state of @code{procfs} API call tracing.
12831 @item set procfs-file @var{file}
12832 @kindex set procfs-file
12833 Tell @value{GDBN} to write @code{procfs} API trace to the named
12834 @var{file}. @value{GDBN} appends the trace info to the previous
12835 contents of the file. The default is to display the trace on the
12838 @item show procfs-file
12839 @kindex show procfs-file
12840 Show the file to which @code{procfs} API trace is written.
12842 @item proc-trace-entry
12843 @itemx proc-trace-exit
12844 @itemx proc-untrace-entry
12845 @itemx proc-untrace-exit
12846 @kindex proc-trace-entry
12847 @kindex proc-trace-exit
12848 @kindex proc-untrace-entry
12849 @kindex proc-untrace-exit
12850 These commands enable and disable tracing of entries into and exits
12851 from the @code{syscall} interface.
12854 @kindex info pidlist
12855 @cindex process list, QNX Neutrino
12856 For QNX Neutrino only, this command displays the list of all the
12857 processes and all the threads within each process.
12860 @kindex info meminfo
12861 @cindex mapinfo list, QNX Neutrino
12862 For QNX Neutrino only, this command displays the list of all mapinfos.
12866 @subsection Features for Debugging @sc{djgpp} Programs
12867 @cindex @sc{djgpp} debugging
12868 @cindex native @sc{djgpp} debugging
12869 @cindex MS-DOS-specific commands
12872 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
12873 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
12874 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
12875 top of real-mode DOS systems and their emulations.
12877 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
12878 defines a few commands specific to the @sc{djgpp} port. This
12879 subsection describes those commands.
12884 This is a prefix of @sc{djgpp}-specific commands which print
12885 information about the target system and important OS structures.
12888 @cindex MS-DOS system info
12889 @cindex free memory information (MS-DOS)
12890 @item info dos sysinfo
12891 This command displays assorted information about the underlying
12892 platform: the CPU type and features, the OS version and flavor, the
12893 DPMI version, and the available conventional and DPMI memory.
12898 @cindex segment descriptor tables
12899 @cindex descriptor tables display
12901 @itemx info dos ldt
12902 @itemx info dos idt
12903 These 3 commands display entries from, respectively, Global, Local,
12904 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
12905 tables are data structures which store a descriptor for each segment
12906 that is currently in use. The segment's selector is an index into a
12907 descriptor table; the table entry for that index holds the
12908 descriptor's base address and limit, and its attributes and access
12911 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
12912 segment (used for both data and the stack), and a DOS segment (which
12913 allows access to DOS/BIOS data structures and absolute addresses in
12914 conventional memory). However, the DPMI host will usually define
12915 additional segments in order to support the DPMI environment.
12917 @cindex garbled pointers
12918 These commands allow to display entries from the descriptor tables.
12919 Without an argument, all entries from the specified table are
12920 displayed. An argument, which should be an integer expression, means
12921 display a single entry whose index is given by the argument. For
12922 example, here's a convenient way to display information about the
12923 debugged program's data segment:
12926 @exdent @code{(@value{GDBP}) info dos ldt $ds}
12927 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
12931 This comes in handy when you want to see whether a pointer is outside
12932 the data segment's limit (i.e.@: @dfn{garbled}).
12934 @cindex page tables display (MS-DOS)
12936 @itemx info dos pte
12937 These two commands display entries from, respectively, the Page
12938 Directory and the Page Tables. Page Directories and Page Tables are
12939 data structures which control how virtual memory addresses are mapped
12940 into physical addresses. A Page Table includes an entry for every
12941 page of memory that is mapped into the program's address space; there
12942 may be several Page Tables, each one holding up to 4096 entries. A
12943 Page Directory has up to 4096 entries, one each for every Page Table
12944 that is currently in use.
12946 Without an argument, @kbd{info dos pde} displays the entire Page
12947 Directory, and @kbd{info dos pte} displays all the entries in all of
12948 the Page Tables. An argument, an integer expression, given to the
12949 @kbd{info dos pde} command means display only that entry from the Page
12950 Directory table. An argument given to the @kbd{info dos pte} command
12951 means display entries from a single Page Table, the one pointed to by
12952 the specified entry in the Page Directory.
12954 @cindex direct memory access (DMA) on MS-DOS
12955 These commands are useful when your program uses @dfn{DMA} (Direct
12956 Memory Access), which needs physical addresses to program the DMA
12959 These commands are supported only with some DPMI servers.
12961 @cindex physical address from linear address
12962 @item info dos address-pte @var{addr}
12963 This command displays the Page Table entry for a specified linear
12964 address. The argument @var{addr} is a linear address which should
12965 already have the appropriate segment's base address added to it,
12966 because this command accepts addresses which may belong to @emph{any}
12967 segment. For example, here's how to display the Page Table entry for
12968 the page where a variable @code{i} is stored:
12971 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
12972 @exdent @code{Page Table entry for address 0x11a00d30:}
12973 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
12977 This says that @code{i} is stored at offset @code{0xd30} from the page
12978 whose physical base address is @code{0x02698000}, and shows all the
12979 attributes of that page.
12981 Note that you must cast the addresses of variables to a @code{char *},
12982 since otherwise the value of @code{__djgpp_base_address}, the base
12983 address of all variables and functions in a @sc{djgpp} program, will
12984 be added using the rules of C pointer arithmetics: if @code{i} is
12985 declared an @code{int}, @value{GDBN} will add 4 times the value of
12986 @code{__djgpp_base_address} to the address of @code{i}.
12988 Here's another example, it displays the Page Table entry for the
12992 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
12993 @exdent @code{Page Table entry for address 0x29110:}
12994 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
12998 (The @code{+ 3} offset is because the transfer buffer's address is the
12999 3rd member of the @code{_go32_info_block} structure.) The output
13000 clearly shows that this DPMI server maps the addresses in conventional
13001 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
13002 linear (@code{0x29110}) addresses are identical.
13004 This command is supported only with some DPMI servers.
13007 @cindex DOS serial data link, remote debugging
13008 In addition to native debugging, the DJGPP port supports remote
13009 debugging via a serial data link. The following commands are specific
13010 to remote serial debugging in the DJGPP port of @value{GDBN}.
13013 @kindex set com1base
13014 @kindex set com1irq
13015 @kindex set com2base
13016 @kindex set com2irq
13017 @kindex set com3base
13018 @kindex set com3irq
13019 @kindex set com4base
13020 @kindex set com4irq
13021 @item set com1base @var{addr}
13022 This command sets the base I/O port address of the @file{COM1} serial
13025 @item set com1irq @var{irq}
13026 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
13027 for the @file{COM1} serial port.
13029 There are similar commands @samp{set com2base}, @samp{set com3irq},
13030 etc.@: for setting the port address and the @code{IRQ} lines for the
13033 @kindex show com1base
13034 @kindex show com1irq
13035 @kindex show com2base
13036 @kindex show com2irq
13037 @kindex show com3base
13038 @kindex show com3irq
13039 @kindex show com4base
13040 @kindex show com4irq
13041 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
13042 display the current settings of the base address and the @code{IRQ}
13043 lines used by the COM ports.
13046 @kindex info serial
13047 @cindex DOS serial port status
13048 This command prints the status of the 4 DOS serial ports. For each
13049 port, it prints whether it's active or not, its I/O base address and
13050 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
13051 counts of various errors encountered so far.
13055 @node Cygwin Native
13056 @subsection Features for Debugging MS Windows PE executables
13057 @cindex MS Windows debugging
13058 @cindex native Cygwin debugging
13059 @cindex Cygwin-specific commands
13061 @value{GDBN} supports native debugging of MS Windows programs, including
13062 DLLs with and without symbolic debugging information. There are various
13063 additional Cygwin-specific commands, described in this subsection. The
13064 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
13065 that have no debugging symbols.
13071 This is a prefix of MS Windows specific commands which print
13072 information about the target system and important OS structures.
13074 @item info w32 selector
13075 This command displays information returned by
13076 the Win32 API @code{GetThreadSelectorEntry} function.
13077 It takes an optional argument that is evaluated to
13078 a long value to give the information about this given selector.
13079 Without argument, this command displays information
13080 about the the six segment registers.
13084 This is a Cygwin specific alias of info shared.
13086 @kindex dll-symbols
13088 This command loads symbols from a dll similarly to
13089 add-sym command but without the need to specify a base address.
13091 @kindex set new-console
13092 @item set new-console @var{mode}
13093 If @var{mode} is @code{on} the debuggee will
13094 be started in a new console on next start.
13095 If @var{mode} is @code{off}i, the debuggee will
13096 be started in the same console as the debugger.
13098 @kindex show new-console
13099 @item show new-console
13100 Displays whether a new console is used
13101 when the debuggee is started.
13103 @kindex set new-group
13104 @item set new-group @var{mode}
13105 This boolean value controls whether the debuggee should
13106 start a new group or stay in the same group as the debugger.
13107 This affects the way the Windows OS handles
13110 @kindex show new-group
13111 @item show new-group
13112 Displays current value of new-group boolean.
13114 @kindex set debugevents
13115 @item set debugevents
13116 This boolean value adds debug output concerning events seen by the debugger.
13118 @kindex set debugexec
13119 @item set debugexec
13120 This boolean value adds debug output concerning execute events
13121 seen by the debugger.
13123 @kindex set debugexceptions
13124 @item set debugexceptions
13125 This boolean value adds debug ouptut concerning exception events
13126 seen by the debugger.
13128 @kindex set debugmemory
13129 @item set debugmemory
13130 This boolean value adds debug ouptut concerning memory events
13131 seen by the debugger.
13135 This boolean values specifies whether the debuggee is called
13136 via a shell or directly (default value is on).
13140 Displays if the debuggee will be started with a shell.
13145 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
13148 @node Non-debug DLL symbols
13149 @subsubsection Support for DLLs without debugging symbols
13150 @cindex DLLs with no debugging symbols
13151 @cindex Minimal symbols and DLLs
13153 Very often on windows, some of the DLLs that your program relies on do
13154 not include symbolic debugging information (for example,
13155 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
13156 symbols in a DLL, it relies on the minimal amount of symbolic
13157 information contained in the DLL's export table. This subsubsection
13158 describes working with such symbols, known internally to @value{GDBN} as
13159 ``minimal symbols''.
13161 Note that before the debugged program has started execution, no DLLs
13162 will have been loaded. The easiest way around this problem is simply to
13163 start the program --- either by setting a breakpoint or letting the
13164 program run once to completion. It is also possible to force
13165 @value{GDBN} to load a particular DLL before starting the executable ---
13166 see the shared library information in @pxref{Files} or the
13167 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
13168 explicitly loading symbols from a DLL with no debugging information will
13169 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
13170 which may adversely affect symbol lookup performance.
13172 @subsubsection DLL name prefixes
13174 In keeping with the naming conventions used by the Microsoft debugging
13175 tools, DLL export symbols are made available with a prefix based on the
13176 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
13177 also entered into the symbol table, so @code{CreateFileA} is often
13178 sufficient. In some cases there will be name clashes within a program
13179 (particularly if the executable itself includes full debugging symbols)
13180 necessitating the use of the fully qualified name when referring to the
13181 contents of the DLL. Use single-quotes around the name to avoid the
13182 exclamation mark (``!'') being interpreted as a language operator.
13184 Note that the internal name of the DLL may be all upper-case, even
13185 though the file name of the DLL is lower-case, or vice-versa. Since
13186 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
13187 some confusion. If in doubt, try the @code{info functions} and
13188 @code{info variables} commands or even @code{maint print msymbols} (see
13189 @pxref{Symbols}). Here's an example:
13192 (@value{GDBP}) info function CreateFileA
13193 All functions matching regular expression "CreateFileA":
13195 Non-debugging symbols:
13196 0x77e885f4 CreateFileA
13197 0x77e885f4 KERNEL32!CreateFileA
13201 (@value{GDBP}) info function !
13202 All functions matching regular expression "!":
13204 Non-debugging symbols:
13205 0x6100114c cygwin1!__assert
13206 0x61004034 cygwin1!_dll_crt0@@0
13207 0x61004240 cygwin1!dll_crt0(per_process *)
13211 @subsubsection Working with minimal symbols
13213 Symbols extracted from a DLL's export table do not contain very much
13214 type information. All that @value{GDBN} can do is guess whether a symbol
13215 refers to a function or variable depending on the linker section that
13216 contains the symbol. Also note that the actual contents of the memory
13217 contained in a DLL are not available unless the program is running. This
13218 means that you cannot examine the contents of a variable or disassemble
13219 a function within a DLL without a running program.
13221 Variables are generally treated as pointers and dereferenced
13222 automatically. For this reason, it is often necessary to prefix a
13223 variable name with the address-of operator (``&'') and provide explicit
13224 type information in the command. Here's an example of the type of
13228 (@value{GDBP}) print 'cygwin1!__argv'
13233 (@value{GDBP}) x 'cygwin1!__argv'
13234 0x10021610: "\230y\""
13237 And two possible solutions:
13240 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
13241 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
13245 (@value{GDBP}) x/2x &'cygwin1!__argv'
13246 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
13247 (@value{GDBP}) x/x 0x10021608
13248 0x10021608: 0x0022fd98
13249 (@value{GDBP}) x/s 0x0022fd98
13250 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
13253 Setting a break point within a DLL is possible even before the program
13254 starts execution. However, under these circumstances, @value{GDBN} can't
13255 examine the initial instructions of the function in order to skip the
13256 function's frame set-up code. You can work around this by using ``*&''
13257 to set the breakpoint at a raw memory address:
13260 (@value{GDBP}) break *&'python22!PyOS_Readline'
13261 Breakpoint 1 at 0x1e04eff0
13264 The author of these extensions is not entirely convinced that setting a
13265 break point within a shared DLL like @file{kernel32.dll} is completely
13269 @subsection Commands specific to @sc{gnu} Hurd systems
13270 @cindex @sc{gnu} Hurd debugging
13272 This subsection describes @value{GDBN} commands specific to the
13273 @sc{gnu} Hurd native debugging.
13278 @kindex set signals@r{, Hurd command}
13279 @kindex set sigs@r{, Hurd command}
13280 This command toggles the state of inferior signal interception by
13281 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
13282 affected by this command. @code{sigs} is a shorthand alias for
13287 @kindex show signals@r{, Hurd command}
13288 @kindex show sigs@r{, Hurd command}
13289 Show the current state of intercepting inferior's signals.
13291 @item set signal-thread
13292 @itemx set sigthread
13293 @kindex set signal-thread
13294 @kindex set sigthread
13295 This command tells @value{GDBN} which thread is the @code{libc} signal
13296 thread. That thread is run when a signal is delivered to a running
13297 process. @code{set sigthread} is the shorthand alias of @code{set
13300 @item show signal-thread
13301 @itemx show sigthread
13302 @kindex show signal-thread
13303 @kindex show sigthread
13304 These two commands show which thread will run when the inferior is
13305 delivered a signal.
13308 @kindex set stopped@r{, Hurd command}
13309 This commands tells @value{GDBN} that the inferior process is stopped,
13310 as with the @code{SIGSTOP} signal. The stopped process can be
13311 continued by delivering a signal to it.
13314 @kindex show stopped@r{, Hurd command}
13315 This command shows whether @value{GDBN} thinks the debuggee is
13318 @item set exceptions
13319 @kindex set exceptions@r{, Hurd command}
13320 Use this command to turn off trapping of exceptions in the inferior.
13321 When exception trapping is off, neither breakpoints nor
13322 single-stepping will work. To restore the default, set exception
13325 @item show exceptions
13326 @kindex show exceptions@r{, Hurd command}
13327 Show the current state of trapping exceptions in the inferior.
13329 @item set task pause
13330 @kindex set task@r{, Hurd commands}
13331 @cindex task attributes (@sc{gnu} Hurd)
13332 @cindex pause current task (@sc{gnu} Hurd)
13333 This command toggles task suspension when @value{GDBN} has control.
13334 Setting it to on takes effect immediately, and the task is suspended
13335 whenever @value{GDBN} gets control. Setting it to off will take
13336 effect the next time the inferior is continued. If this option is set
13337 to off, you can use @code{set thread default pause on} or @code{set
13338 thread pause on} (see below) to pause individual threads.
13340 @item show task pause
13341 @kindex show task@r{, Hurd commands}
13342 Show the current state of task suspension.
13344 @item set task detach-suspend-count
13345 @cindex task suspend count
13346 @cindex detach from task, @sc{gnu} Hurd
13347 This command sets the suspend count the task will be left with when
13348 @value{GDBN} detaches from it.
13350 @item show task detach-suspend-count
13351 Show the suspend count the task will be left with when detaching.
13353 @item set task exception-port
13354 @itemx set task excp
13355 @cindex task exception port, @sc{gnu} Hurd
13356 This command sets the task exception port to which @value{GDBN} will
13357 forward exceptions. The argument should be the value of the @dfn{send
13358 rights} of the task. @code{set task excp} is a shorthand alias.
13360 @item set noninvasive
13361 @cindex noninvasive task options
13362 This command switches @value{GDBN} to a mode that is the least
13363 invasive as far as interfering with the inferior is concerned. This
13364 is the same as using @code{set task pause}, @code{set exceptions}, and
13365 @code{set signals} to values opposite to the defaults.
13367 @item info send-rights
13368 @itemx info receive-rights
13369 @itemx info port-rights
13370 @itemx info port-sets
13371 @itemx info dead-names
13374 @cindex send rights, @sc{gnu} Hurd
13375 @cindex receive rights, @sc{gnu} Hurd
13376 @cindex port rights, @sc{gnu} Hurd
13377 @cindex port sets, @sc{gnu} Hurd
13378 @cindex dead names, @sc{gnu} Hurd
13379 These commands display information about, respectively, send rights,
13380 receive rights, port rights, port sets, and dead names of a task.
13381 There are also shorthand aliases: @code{info ports} for @code{info
13382 port-rights} and @code{info psets} for @code{info port-sets}.
13384 @item set thread pause
13385 @kindex set thread@r{, Hurd command}
13386 @cindex thread properties, @sc{gnu} Hurd
13387 @cindex pause current thread (@sc{gnu} Hurd)
13388 This command toggles current thread suspension when @value{GDBN} has
13389 control. Setting it to on takes effect immediately, and the current
13390 thread is suspended whenever @value{GDBN} gets control. Setting it to
13391 off will take effect the next time the inferior is continued.
13392 Normally, this command has no effect, since when @value{GDBN} has
13393 control, the whole task is suspended. However, if you used @code{set
13394 task pause off} (see above), this command comes in handy to suspend
13395 only the current thread.
13397 @item show thread pause
13398 @kindex show thread@r{, Hurd command}
13399 This command shows the state of current thread suspension.
13401 @item set thread run
13402 This comamnd sets whether the current thread is allowed to run.
13404 @item show thread run
13405 Show whether the current thread is allowed to run.
13407 @item set thread detach-suspend-count
13408 @cindex thread suspend count, @sc{gnu} Hurd
13409 @cindex detach from thread, @sc{gnu} Hurd
13410 This command sets the suspend count @value{GDBN} will leave on a
13411 thread when detaching. This number is relative to the suspend count
13412 found by @value{GDBN} when it notices the thread; use @code{set thread
13413 takeover-suspend-count} to force it to an absolute value.
13415 @item show thread detach-suspend-count
13416 Show the suspend count @value{GDBN} will leave on the thread when
13419 @item set thread exception-port
13420 @itemx set thread excp
13421 Set the thread exception port to which to forward exceptions. This
13422 overrides the port set by @code{set task exception-port} (see above).
13423 @code{set thread excp} is the shorthand alias.
13425 @item set thread takeover-suspend-count
13426 Normally, @value{GDBN}'s thread suspend counts are relative to the
13427 value @value{GDBN} finds when it notices each thread. This command
13428 changes the suspend counts to be absolute instead.
13430 @item set thread default
13431 @itemx show thread default
13432 @cindex thread default settings, @sc{gnu} Hurd
13433 Each of the above @code{set thread} commands has a @code{set thread
13434 default} counterpart (e.g., @code{set thread default pause}, @code{set
13435 thread default exception-port}, etc.). The @code{thread default}
13436 variety of commands sets the default thread properties for all
13437 threads; you can then change the properties of individual threads with
13438 the non-default commands.
13443 @subsection QNX Neutrino
13444 @cindex QNX Neutrino
13446 @value{GDBN} provides the following commands specific to the QNX
13450 @item set debug nto-debug
13451 @kindex set debug nto-debug
13452 When set to on, enables debugging messages specific to the QNX
13455 @item show debug nto-debug
13456 @kindex show debug nto-debug
13457 Show the current state of QNX Neutrino messages.
13462 @section Embedded Operating Systems
13464 This section describes configurations involving the debugging of
13465 embedded operating systems that are available for several different
13469 * VxWorks:: Using @value{GDBN} with VxWorks
13472 @value{GDBN} includes the ability to debug programs running on
13473 various real-time operating systems.
13476 @subsection Using @value{GDBN} with VxWorks
13482 @kindex target vxworks
13483 @item target vxworks @var{machinename}
13484 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
13485 is the target system's machine name or IP address.
13489 On VxWorks, @code{load} links @var{filename} dynamically on the
13490 current target system as well as adding its symbols in @value{GDBN}.
13492 @value{GDBN} enables developers to spawn and debug tasks running on networked
13493 VxWorks targets from a Unix host. Already-running tasks spawned from
13494 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
13495 both the Unix host and on the VxWorks target. The program
13496 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
13497 installed with the name @code{vxgdb}, to distinguish it from a
13498 @value{GDBN} for debugging programs on the host itself.)
13501 @item VxWorks-timeout @var{args}
13502 @kindex vxworks-timeout
13503 All VxWorks-based targets now support the option @code{vxworks-timeout}.
13504 This option is set by the user, and @var{args} represents the number of
13505 seconds @value{GDBN} waits for responses to rpc's. You might use this if
13506 your VxWorks target is a slow software simulator or is on the far side
13507 of a thin network line.
13510 The following information on connecting to VxWorks was current when
13511 this manual was produced; newer releases of VxWorks may use revised
13514 @findex INCLUDE_RDB
13515 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
13516 to include the remote debugging interface routines in the VxWorks
13517 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
13518 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
13519 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
13520 source debugging task @code{tRdbTask} when VxWorks is booted. For more
13521 information on configuring and remaking VxWorks, see the manufacturer's
13523 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
13525 Once you have included @file{rdb.a} in your VxWorks system image and set
13526 your Unix execution search path to find @value{GDBN}, you are ready to
13527 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
13528 @code{vxgdb}, depending on your installation).
13530 @value{GDBN} comes up showing the prompt:
13537 * VxWorks Connection:: Connecting to VxWorks
13538 * VxWorks Download:: VxWorks download
13539 * VxWorks Attach:: Running tasks
13542 @node VxWorks Connection
13543 @subsubsection Connecting to VxWorks
13545 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
13546 network. To connect to a target whose host name is ``@code{tt}'', type:
13549 (vxgdb) target vxworks tt
13553 @value{GDBN} displays messages like these:
13556 Attaching remote machine across net...
13561 @value{GDBN} then attempts to read the symbol tables of any object modules
13562 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
13563 these files by searching the directories listed in the command search
13564 path (@pxref{Environment, ,Your program's environment}); if it fails
13565 to find an object file, it displays a message such as:
13568 prog.o: No such file or directory.
13571 When this happens, add the appropriate directory to the search path with
13572 the @value{GDBN} command @code{path}, and execute the @code{target}
13575 @node VxWorks Download
13576 @subsubsection VxWorks download
13578 @cindex download to VxWorks
13579 If you have connected to the VxWorks target and you want to debug an
13580 object that has not yet been loaded, you can use the @value{GDBN}
13581 @code{load} command to download a file from Unix to VxWorks
13582 incrementally. The object file given as an argument to the @code{load}
13583 command is actually opened twice: first by the VxWorks target in order
13584 to download the code, then by @value{GDBN} in order to read the symbol
13585 table. This can lead to problems if the current working directories on
13586 the two systems differ. If both systems have NFS mounted the same
13587 filesystems, you can avoid these problems by using absolute paths.
13588 Otherwise, it is simplest to set the working directory on both systems
13589 to the directory in which the object file resides, and then to reference
13590 the file by its name, without any path. For instance, a program
13591 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
13592 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
13593 program, type this on VxWorks:
13596 -> cd "@var{vxpath}/vw/demo/rdb"
13600 Then, in @value{GDBN}, type:
13603 (vxgdb) cd @var{hostpath}/vw/demo/rdb
13604 (vxgdb) load prog.o
13607 @value{GDBN} displays a response similar to this:
13610 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
13613 You can also use the @code{load} command to reload an object module
13614 after editing and recompiling the corresponding source file. Note that
13615 this makes @value{GDBN} delete all currently-defined breakpoints,
13616 auto-displays, and convenience variables, and to clear the value
13617 history. (This is necessary in order to preserve the integrity of
13618 debugger's data structures that reference the target system's symbol
13621 @node VxWorks Attach
13622 @subsubsection Running tasks
13624 @cindex running VxWorks tasks
13625 You can also attach to an existing task using the @code{attach} command as
13629 (vxgdb) attach @var{task}
13633 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
13634 or suspended when you attach to it. Running tasks are suspended at
13635 the time of attachment.
13637 @node Embedded Processors
13638 @section Embedded Processors
13640 This section goes into details specific to particular embedded
13643 @cindex send command to simulator
13644 Whenever a specific embedded processor has a simulator, @value{GDBN}
13645 allows to send an arbitrary command to the simulator.
13648 @item sim @var{command}
13649 @kindex sim@r{, a command}
13650 Send an arbitrary @var{command} string to the simulator. Consult the
13651 documentation for the specific simulator in use for information about
13652 acceptable commands.
13658 * H8/300:: Renesas H8/300
13659 * H8/500:: Renesas H8/500
13660 * M32R/D:: Renesas M32R/D
13661 * M68K:: Motorola M68K
13662 * MIPS Embedded:: MIPS Embedded
13663 * OpenRISC 1000:: OpenRisc 1000
13664 * PA:: HP PA Embedded
13667 * Sparclet:: Tsqware Sparclet
13668 * Sparclite:: Fujitsu Sparclite
13669 * ST2000:: Tandem ST2000
13670 * Z8000:: Zilog Z8000
13673 * Super-H:: Renesas Super-H
13674 * WinCE:: Windows CE child processes
13683 @item target rdi @var{dev}
13684 ARM Angel monitor, via RDI library interface to ADP protocol. You may
13685 use this target to communicate with both boards running the Angel
13686 monitor, or with the EmbeddedICE JTAG debug device.
13689 @item target rdp @var{dev}
13694 @value{GDBN} provides the following ARM-specific commands:
13697 @item set arm disassembler
13699 This commands selects from a list of disassembly styles. The
13700 @code{"std"} style is the standard style.
13702 @item show arm disassembler
13704 Show the current disassembly style.
13706 @item set arm apcs32
13707 @cindex ARM 32-bit mode
13708 This command toggles ARM operation mode between 32-bit and 26-bit.
13710 @item show arm apcs32
13711 Display the current usage of the ARM 32-bit mode.
13713 @item set arm fpu @var{fputype}
13714 This command sets the ARM floating-point unit (FPU) type. The
13715 argument @var{fputype} can be one of these:
13719 Determine the FPU type by querying the OS ABI.
13721 Software FPU, with mixed-endian doubles on little-endian ARM
13724 GCC-compiled FPA co-processor.
13726 Software FPU with pure-endian doubles.
13732 Show the current type of the FPU.
13735 This command forces @value{GDBN} to use the specified ABI.
13738 Show the currently used ABI.
13740 @item set debug arm
13741 Toggle whether to display ARM-specific debugging messages from the ARM
13742 target support subsystem.
13744 @item show debug arm
13745 Show whether ARM-specific debugging messages are enabled.
13748 The following commands are available when an ARM target is debugged
13749 using the RDI interface:
13752 @item rdilogfile @r{[}@var{file}@r{]}
13754 @cindex ADP (Angel Debugger Protocol) logging
13755 Set the filename for the ADP (Angel Debugger Protocol) packet log.
13756 With an argument, sets the log file to the specified @var{file}. With
13757 no argument, show the current log file name. The default log file is
13760 @item rdilogenable @r{[}@var{arg}@r{]}
13761 @kindex rdilogenable
13762 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
13763 enables logging, with an argument 0 or @code{"no"} disables it. With
13764 no arguments displays the current setting. When logging is enabled,
13765 ADP packets exchanged between @value{GDBN} and the RDI target device
13766 are logged to a file.
13768 @item set rdiromatzero
13769 @kindex set rdiromatzero
13770 @cindex ROM at zero address, RDI
13771 Tell @value{GDBN} whether the target has ROM at address 0. If on,
13772 vector catching is disabled, so that zero address can be used. If off
13773 (the default), vector catching is enabled. For this command to take
13774 effect, it needs to be invoked prior to the @code{target rdi} command.
13776 @item show rdiromatzero
13777 @kindex show rdiromatzero
13778 Show the current setting of ROM at zero address.
13780 @item set rdiheartbeat
13781 @kindex set rdiheartbeat
13782 @cindex RDI heartbeat
13783 Enable or disable RDI heartbeat packets. It is not recommended to
13784 turn on this option, since it confuses ARM and EPI JTAG interface, as
13785 well as the Angel monitor.
13787 @item show rdiheartbeat
13788 @kindex show rdiheartbeat
13789 Show the setting of RDI heartbeat packets.
13794 @subsection Renesas H8/300
13798 @kindex target hms@r{, with H8/300}
13799 @item target hms @var{dev}
13800 A Renesas SH, H8/300, or H8/500 board, attached via serial line to your host.
13801 Use special commands @code{device} and @code{speed} to control the serial
13802 line and the communications speed used.
13804 @kindex target e7000@r{, with H8/300}
13805 @item target e7000 @var{dev}
13806 E7000 emulator for Renesas H8 and SH.
13808 @kindex target sh3@r{, with H8/300}
13809 @kindex target sh3e@r{, with H8/300}
13810 @item target sh3 @var{dev}
13811 @itemx target sh3e @var{dev}
13812 Renesas SH-3 and SH-3E target systems.
13816 @cindex download to H8/300 or H8/500
13817 @cindex H8/300 or H8/500 download
13818 @cindex download to Renesas SH
13819 @cindex Renesas SH download
13820 When you select remote debugging to a Renesas SH, H8/300, or H8/500
13821 board, the @code{load} command downloads your program to the Renesas
13822 board and also opens it as the current executable target for
13823 @value{GDBN} on your host (like the @code{file} command).
13825 @value{GDBN} needs to know these things to talk to your
13826 Renesas SH, H8/300, or H8/500:
13830 that you want to use @samp{target hms}, the remote debugging interface
13831 for Renesas microprocessors, or @samp{target e7000}, the in-circuit
13832 emulator for the Renesas SH and the Renesas 300H. (@samp{target hms} is
13833 the default when @value{GDBN} is configured specifically for the Renesas SH,
13834 H8/300, or H8/500.)
13837 what serial device connects your host to your Renesas board (the first
13838 serial device available on your host is the default).
13841 what speed to use over the serial device.
13845 * Renesas Boards:: Connecting to Renesas boards.
13846 * Renesas ICE:: Using the E7000 In-Circuit Emulator.
13847 * Renesas Special:: Special @value{GDBN} commands for Renesas micros.
13850 @node Renesas Boards
13851 @subsubsection Connecting to Renesas boards
13853 @c only for Unix hosts
13855 @cindex serial device, Renesas micros
13856 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
13857 need to explicitly set the serial device. The default @var{port} is the
13858 first available port on your host. This is only necessary on Unix
13859 hosts, where it is typically something like @file{/dev/ttya}.
13862 @cindex serial line speed, Renesas micros
13863 @code{@value{GDBN}} has another special command to set the communications
13864 speed: @samp{speed @var{bps}}. This command also is only used from Unix
13865 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
13866 the DOS @code{mode} command (for instance,
13867 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
13869 The @samp{device} and @samp{speed} commands are available only when you
13870 use a Unix host to debug your Renesas microprocessor programs. If you
13872 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
13873 called @code{asynctsr} to communicate with the development board
13874 through a PC serial port. You must also use the DOS @code{mode} command
13875 to set up the serial port on the DOS side.
13877 The following sample session illustrates the steps needed to start a
13878 program under @value{GDBN} control on an H8/300. The example uses a
13879 sample H8/300 program called @file{t.x}. The procedure is the same for
13880 the Renesas SH and the H8/500.
13882 First hook up your development board. In this example, we use a
13883 board attached to serial port @code{COM2}; if you use a different serial
13884 port, substitute its name in the argument of the @code{mode} command.
13885 When you call @code{asynctsr}, the auxiliary comms program used by the
13886 debugger, you give it just the numeric part of the serial port's name;
13887 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
13891 C:\H8300\TEST> asynctsr 2
13892 C:\H8300\TEST> mode com2:9600,n,8,1,p
13894 Resident portion of MODE loaded
13896 COM2: 9600, n, 8, 1, p
13901 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
13902 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
13903 disable it, or even boot without it, to use @code{asynctsr} to control
13904 your development board.
13907 @kindex target hms@r{, and serial protocol}
13908 Now that serial communications are set up, and the development board is
13909 connected, you can start up @value{GDBN}. Call @code{@value{GDBN}} with
13910 the name of your program as the argument. @code{@value{GDBN}} prompts
13911 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
13912 commands to begin your debugging session: @samp{target hms} to specify
13913 cross-debugging to the Renesas board, and the @code{load} command to
13914 download your program to the board. @code{load} displays the names of
13915 the program's sections, and a @samp{*} for each 2K of data downloaded.
13916 (If you want to refresh @value{GDBN} data on symbols or on the
13917 executable file without downloading, use the @value{GDBN} commands
13918 @code{file} or @code{symbol-file}. These commands, and @code{load}
13919 itself, are described in @ref{Files,,Commands to specify files}.)
13922 (eg-C:\H8300\TEST) @value{GDBP} t.x
13923 @value{GDBN} is free software and you are welcome to distribute copies
13924 of it under certain conditions; type "show copying" to see
13926 There is absolutely no warranty for @value{GDBN}; type "show warranty"
13928 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
13929 (@value{GDBP}) target hms
13930 Connected to remote H8/300 HMS system.
13931 (@value{GDBP}) load t.x
13932 .text : 0x8000 .. 0xabde ***********
13933 .data : 0xabde .. 0xad30 *
13934 .stack : 0xf000 .. 0xf014 *
13937 At this point, you're ready to run or debug your program. From here on,
13938 you can use all the usual @value{GDBN} commands. The @code{break} command
13939 sets breakpoints; the @code{run} command starts your program;
13940 @code{print} or @code{x} display data; the @code{continue} command
13941 resumes execution after stopping at a breakpoint. You can use the
13942 @code{help} command at any time to find out more about @value{GDBN} commands.
13944 Remember, however, that @emph{operating system} facilities aren't
13945 available on your development board; for example, if your program hangs,
13946 you can't send an interrupt---but you can press the @sc{reset} switch!
13948 Use the @sc{reset} button on the development board
13951 to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
13952 no way to pass an interrupt signal to the development board); and
13955 to return to the @value{GDBN} command prompt after your program finishes
13956 normally. The communications protocol provides no other way for @value{GDBN}
13957 to detect program completion.
13960 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
13961 development board as a ``normal exit'' of your program.
13964 @subsubsection Using the E7000 in-circuit emulator
13966 @kindex target e7000@r{, with Renesas ICE}
13967 You can use the E7000 in-circuit emulator to develop code for either the
13968 Renesas SH or the H8/300H. Use one of these forms of the @samp{target
13969 e7000} command to connect @value{GDBN} to your E7000:
13972 @item target e7000 @var{port} @var{speed}
13973 Use this form if your E7000 is connected to a serial port. The
13974 @var{port} argument identifies what serial port to use (for example,
13975 @samp{com2}). The third argument is the line speed in bits per second
13976 (for example, @samp{9600}).
13978 @item target e7000 @var{hostname}
13979 If your E7000 is installed as a host on a TCP/IP network, you can just
13980 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
13983 The following special commands are available when debugging with the
13987 @item e7000 @var{command}
13989 @cindex send command to E7000 monitor
13990 This sends the specified @var{command} to the E7000 monitor.
13992 @item ftplogin @var{machine} @var{username} @var{password} @var{dir}
13993 @kindex ftplogin@r{, E7000}
13994 This command records information for subsequent interface with the
13995 E7000 monitor via the FTP protocol: @value{GDBN} will log into the
13996 named @var{machine} using specified @var{username} and @var{password},
13997 and then chdir to the named directory @var{dir}.
13999 @item ftpload @var{file}
14000 @kindex ftpload@r{, E7000}
14001 This command uses credentials recorded by @code{ftplogin} to fetch and
14002 load the named @var{file} from the E7000 monitor.
14005 @kindex drain@r{, E7000}
14006 This command drains any pending text buffers stored on the E7000.
14008 @item set usehardbreakpoints
14009 @itemx show usehardbreakpoints
14010 @kindex set usehardbreakpoints@r{, E7000}
14011 @kindex show usehardbreakpoints@r{, E7000}
14012 @cindex hardware breakpoints, and E7000
14013 These commands set and show the use of hardware breakpoints for all
14014 breakpoints. @xref{Set Breaks, hardware-assisted breakpoint}, for
14015 more information about using hardware breakpoints selectively.
14018 @node Renesas Special
14019 @subsubsection Special @value{GDBN} commands for Renesas micros
14021 Some @value{GDBN} commands are available only for the H8/300:
14025 @kindex set machine
14026 @kindex show machine
14027 @item set machine h8300
14028 @itemx set machine h8300h
14029 Condition @value{GDBN} for one of the two variants of the H8/300
14030 architecture with @samp{set machine}. You can use @samp{show machine}
14031 to check which variant is currently in effect.
14040 @kindex set memory @var{mod}
14041 @cindex memory models, H8/500
14042 @item set memory @var{mod}
14044 Specify which H8/500 memory model (@var{mod}) you are using with
14045 @samp{set memory}; check which memory model is in effect with @samp{show
14046 memory}. The accepted values for @var{mod} are @code{small},
14047 @code{big}, @code{medium}, and @code{compact}.
14052 @subsection Renesas M32R/D and M32R/SDI
14055 @kindex target m32r
14056 @item target m32r @var{dev}
14057 Renesas M32R/D ROM monitor.
14059 @kindex target m32rsdi
14060 @item target m32rsdi @var{dev}
14061 Renesas M32R SDI server, connected via parallel port to the board.
14064 The following @value{GDBN} commands are specific to the M32R monitor:
14067 @item set download-path @var{path}
14068 @kindex set download-path
14069 @cindex find downloadable @sc{srec} files (M32R)
14070 Set the default path for finding donwloadable @sc{srec} files.
14072 @item show download-path
14073 @kindex show download-path
14074 Show the default path for downloadable @sc{srec} files.
14076 @item set board-address @var{addr}
14077 @kindex set board-address
14078 @cindex M32-EVA target board address
14079 Set the IP address for the M32R-EVA target board.
14081 @item show board-address
14082 @kindex show board-address
14083 Show the current IP address of the target board.
14085 @item set server-address @var{addr}
14086 @kindex set server-address
14087 @cindex download server address (M32R)
14088 Set the IP address for the download server, which is the @value{GDBN}'s
14091 @item show server-address
14092 @kindex show server-address
14093 Display the IP address of the download server.
14095 @item upload @r{[}@var{file}@r{]}
14096 @kindex upload@r{, M32R}
14097 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
14098 upload capability. If no @var{file} argument is given, the current
14099 executable file is uploaded.
14101 @item tload @r{[}@var{file}@r{]}
14102 @kindex tload@r{, M32R}
14103 Test the @code{upload} command.
14106 The following commands are available for M32R/SDI:
14111 @cindex reset SDI connection, M32R
14112 This command resets the SDI connection.
14116 This command shows the SDI connection status.
14119 @kindex debug_chaos
14120 @cindex M32R/Chaos debugging
14121 Instructs the remote that M32R/Chaos debugging is to be used.
14123 @item use_debug_dma
14124 @kindex use_debug_dma
14125 Instructs the remote to use the DEBUG_DMA method of accessing memory.
14128 @kindex use_mon_code
14129 Instructs the remote to use the MON_CODE method of accessing memory.
14132 @kindex use_ib_break
14133 Instructs the remote to set breakpoints by IB break.
14135 @item use_dbt_break
14136 @kindex use_dbt_break
14137 Instructs the remote to set breakpoints by DBT.
14143 The Motorola m68k configuration includes ColdFire support, and
14144 target command for the following ROM monitors.
14148 @kindex target abug
14149 @item target abug @var{dev}
14150 ABug ROM monitor for M68K.
14152 @kindex target cpu32bug
14153 @item target cpu32bug @var{dev}
14154 CPU32BUG monitor, running on a CPU32 (M68K) board.
14156 @kindex target dbug
14157 @item target dbug @var{dev}
14158 dBUG ROM monitor for Motorola ColdFire.
14161 @item target est @var{dev}
14162 EST-300 ICE monitor, running on a CPU32 (M68K) board.
14164 @kindex target rom68k
14165 @item target rom68k @var{dev}
14166 ROM 68K monitor, running on an M68K IDP board.
14172 @kindex target rombug
14173 @item target rombug @var{dev}
14174 ROMBUG ROM monitor for OS/9000.
14178 @node MIPS Embedded
14179 @subsection MIPS Embedded
14181 @cindex MIPS boards
14182 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
14183 MIPS board attached to a serial line. This is available when
14184 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
14187 Use these @value{GDBN} commands to specify the connection to your target board:
14190 @item target mips @var{port}
14191 @kindex target mips @var{port}
14192 To run a program on the board, start up @code{@value{GDBP}} with the
14193 name of your program as the argument. To connect to the board, use the
14194 command @samp{target mips @var{port}}, where @var{port} is the name of
14195 the serial port connected to the board. If the program has not already
14196 been downloaded to the board, you may use the @code{load} command to
14197 download it. You can then use all the usual @value{GDBN} commands.
14199 For example, this sequence connects to the target board through a serial
14200 port, and loads and runs a program called @var{prog} through the
14204 host$ @value{GDBP} @var{prog}
14205 @value{GDBN} is free software and @dots{}
14206 (@value{GDBP}) target mips /dev/ttyb
14207 (@value{GDBP}) load @var{prog}
14211 @item target mips @var{hostname}:@var{portnumber}
14212 On some @value{GDBN} host configurations, you can specify a TCP
14213 connection (for instance, to a serial line managed by a terminal
14214 concentrator) instead of a serial port, using the syntax
14215 @samp{@var{hostname}:@var{portnumber}}.
14217 @item target pmon @var{port}
14218 @kindex target pmon @var{port}
14221 @item target ddb @var{port}
14222 @kindex target ddb @var{port}
14223 NEC's DDB variant of PMON for Vr4300.
14225 @item target lsi @var{port}
14226 @kindex target lsi @var{port}
14227 LSI variant of PMON.
14229 @kindex target r3900
14230 @item target r3900 @var{dev}
14231 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
14233 @kindex target array
14234 @item target array @var{dev}
14235 Array Tech LSI33K RAID controller board.
14241 @value{GDBN} also supports these special commands for MIPS targets:
14244 @item set mipsfpu double
14245 @itemx set mipsfpu single
14246 @itemx set mipsfpu none
14247 @itemx set mipsfpu auto
14248 @itemx show mipsfpu
14249 @kindex set mipsfpu
14250 @kindex show mipsfpu
14251 @cindex MIPS remote floating point
14252 @cindex floating point, MIPS remote
14253 If your target board does not support the MIPS floating point
14254 coprocessor, you should use the command @samp{set mipsfpu none} (if you
14255 need this, you may wish to put the command in your @value{GDBN} init
14256 file). This tells @value{GDBN} how to find the return value of
14257 functions which return floating point values. It also allows
14258 @value{GDBN} to avoid saving the floating point registers when calling
14259 functions on the board. If you are using a floating point coprocessor
14260 with only single precision floating point support, as on the @sc{r4650}
14261 processor, use the command @samp{set mipsfpu single}. The default
14262 double precision floating point coprocessor may be selected using
14263 @samp{set mipsfpu double}.
14265 In previous versions the only choices were double precision or no
14266 floating point, so @samp{set mipsfpu on} will select double precision
14267 and @samp{set mipsfpu off} will select no floating point.
14269 As usual, you can inquire about the @code{mipsfpu} variable with
14270 @samp{show mipsfpu}.
14272 @item set timeout @var{seconds}
14273 @itemx set retransmit-timeout @var{seconds}
14274 @itemx show timeout
14275 @itemx show retransmit-timeout
14276 @cindex @code{timeout}, MIPS protocol
14277 @cindex @code{retransmit-timeout}, MIPS protocol
14278 @kindex set timeout
14279 @kindex show timeout
14280 @kindex set retransmit-timeout
14281 @kindex show retransmit-timeout
14282 You can control the timeout used while waiting for a packet, in the MIPS
14283 remote protocol, with the @code{set timeout @var{seconds}} command. The
14284 default is 5 seconds. Similarly, you can control the timeout used while
14285 waiting for an acknowledgement of a packet with the @code{set
14286 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
14287 You can inspect both values with @code{show timeout} and @code{show
14288 retransmit-timeout}. (These commands are @emph{only} available when
14289 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
14291 The timeout set by @code{set timeout} does not apply when @value{GDBN}
14292 is waiting for your program to stop. In that case, @value{GDBN} waits
14293 forever because it has no way of knowing how long the program is going
14294 to run before stopping.
14296 @item set syn-garbage-limit @var{num}
14297 @kindex set syn-garbage-limit@r{, MIPS remote}
14298 @cindex synchronize with remote MIPS target
14299 Limit the maximum number of characters @value{GDBN} should ignore when
14300 it tries to synchronize with the remote target. The default is 10
14301 characters. Setting the limit to -1 means there's no limit.
14303 @item show syn-garbage-limit
14304 @kindex show syn-garbage-limit@r{, MIPS remote}
14305 Show the current limit on the number of characters to ignore when
14306 trying to synchronize with the remote system.
14308 @item set monitor-prompt @var{prompt}
14309 @kindex set monitor-prompt@r{, MIPS remote}
14310 @cindex remote monitor prompt
14311 Tell @value{GDBN} to expect the specified @var{prompt} string from the
14312 remote monitor. The default depends on the target:
14322 @item show monitor-prompt
14323 @kindex show monitor-prompt@r{, MIPS remote}
14324 Show the current strings @value{GDBN} expects as the prompt from the
14327 @item set monitor-warnings
14328 @kindex set monitor-warnings@r{, MIPS remote}
14329 Enable or disable monitor warnings about hardware breakpoints. This
14330 has effect only for the @code{lsi} target. When on, @value{GDBN} will
14331 display warning messages whose codes are returned by the @code{lsi}
14332 PMON monitor for breakpoint commands.
14334 @item show monitor-warnings
14335 @kindex show monitor-warnings@r{, MIPS remote}
14336 Show the current setting of printing monitor warnings.
14338 @item pmon @var{command}
14339 @kindex pmon@r{, MIPS remote}
14340 @cindex send PMON command
14341 This command allows sending an arbitrary @var{command} string to the
14342 monitor. The monitor must be in debug mode for this to work.
14345 @node OpenRISC 1000
14346 @subsection OpenRISC 1000
14347 @cindex OpenRISC 1000
14349 @cindex or1k boards
14350 See OR1k Architecture document (@uref{www.opencores.org}) for more information
14351 about platform and commands.
14355 @kindex target jtag
14356 @item target jtag jtag://@var{host}:@var{port}
14358 Connects to remote JTAG server.
14359 JTAG remote server can be either an or1ksim or JTAG server,
14360 connected via parallel port to the board.
14362 Example: @code{target jtag jtag://localhost:9999}
14365 @item or1ksim @var{command}
14366 If connected to @code{or1ksim} OpenRISC 1000 Architectural
14367 Simulator, proprietary commands can be executed.
14369 @kindex info or1k spr
14370 @item info or1k spr
14371 Displays spr groups.
14373 @item info or1k spr @var{group}
14374 @itemx info or1k spr @var{groupno}
14375 Displays register names in selected group.
14377 @item info or1k spr @var{group} @var{register}
14378 @itemx info or1k spr @var{register}
14379 @itemx info or1k spr @var{groupno} @var{registerno}
14380 @itemx info or1k spr @var{registerno}
14381 Shows information about specified spr register.
14384 @item spr @var{group} @var{register} @var{value}
14385 @itemx spr @var{register @var{value}}
14386 @itemx spr @var{groupno} @var{registerno @var{value}}
14387 @itemx spr @var{registerno @var{value}}
14388 Writes @var{value} to specified spr register.
14391 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
14392 It is very similar to @value{GDBN} trace, except it does not interfere with normal
14393 program execution and is thus much faster. Hardware breakpoints/watchpoint
14394 triggers can be set using:
14397 Load effective address/data
14399 Store effective address/data
14401 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
14406 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
14407 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
14409 @code{htrace} commands:
14410 @cindex OpenRISC 1000 htrace
14413 @item hwatch @var{conditional}
14414 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
14415 or Data. For example:
14417 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14419 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14423 Display information about current HW trace configuration.
14425 @item htrace trigger @var{conditional}
14426 Set starting criteria for HW trace.
14428 @item htrace qualifier @var{conditional}
14429 Set acquisition qualifier for HW trace.
14431 @item htrace stop @var{conditional}
14432 Set HW trace stopping criteria.
14434 @item htrace record [@var{data}]*
14435 Selects the data to be recorded, when qualifier is met and HW trace was
14438 @item htrace enable
14439 @itemx htrace disable
14440 Enables/disables the HW trace.
14442 @item htrace rewind [@var{filename}]
14443 Clears currently recorded trace data.
14445 If filename is specified, new trace file is made and any newly collected data
14446 will be written there.
14448 @item htrace print [@var{start} [@var{len}]]
14449 Prints trace buffer, using current record configuration.
14451 @item htrace mode continuous
14452 Set continuous trace mode.
14454 @item htrace mode suspend
14455 Set suspend trace mode.
14460 @subsection PowerPC
14463 @kindex target dink32
14464 @item target dink32 @var{dev}
14465 DINK32 ROM monitor.
14467 @kindex target ppcbug
14468 @item target ppcbug @var{dev}
14469 @kindex target ppcbug1
14470 @item target ppcbug1 @var{dev}
14471 PPCBUG ROM monitor for PowerPC.
14474 @item target sds @var{dev}
14475 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
14478 @cindex SDS protocol
14479 The following commands specifi to the SDS protocol are supported
14483 @item set sdstimeout @var{nsec}
14484 @kindex set sdstimeout
14485 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
14486 default is 2 seconds.
14488 @item show sdstimeout
14489 @kindex show sdstimeout
14490 Show the current value of the SDS timeout.
14492 @item sds @var{command}
14493 @kindex sds@r{, a command}
14494 Send the specified @var{command} string to the SDS monitor.
14499 @subsection HP PA Embedded
14503 @kindex target op50n
14504 @item target op50n @var{dev}
14505 OP50N monitor, running on an OKI HPPA board.
14507 @kindex target w89k
14508 @item target w89k @var{dev}
14509 W89K monitor, running on a Winbond HPPA board.
14514 @subsection Renesas SH
14518 @kindex target hms@r{, with Renesas SH}
14519 @item target hms @var{dev}
14520 A Renesas SH board attached via serial line to your host. Use special
14521 commands @code{device} and @code{speed} to control the serial line and
14522 the communications speed used.
14524 @kindex target e7000@r{, with Renesas SH}
14525 @item target e7000 @var{dev}
14526 E7000 emulator for Renesas SH.
14528 @kindex target sh3@r{, with SH}
14529 @kindex target sh3e@r{, with SH}
14530 @item target sh3 @var{dev}
14531 @item target sh3e @var{dev}
14532 Renesas SH-3 and SH-3E target systems.
14537 @subsection Tsqware Sparclet
14541 @value{GDBN} enables developers to debug tasks running on
14542 Sparclet targets from a Unix host.
14543 @value{GDBN} uses code that runs on
14544 both the Unix host and on the Sparclet target. The program
14545 @code{@value{GDBP}} is installed and executed on the Unix host.
14548 @item remotetimeout @var{args}
14549 @kindex remotetimeout
14550 @value{GDBN} supports the option @code{remotetimeout}.
14551 This option is set by the user, and @var{args} represents the number of
14552 seconds @value{GDBN} waits for responses.
14555 @cindex compiling, on Sparclet
14556 When compiling for debugging, include the options @samp{-g} to get debug
14557 information and @samp{-Ttext} to relocate the program to where you wish to
14558 load it on the target. You may also want to add the options @samp{-n} or
14559 @samp{-N} in order to reduce the size of the sections. Example:
14562 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
14565 You can use @code{objdump} to verify that the addresses are what you intended:
14568 sparclet-aout-objdump --headers --syms prog
14571 @cindex running, on Sparclet
14573 your Unix execution search path to find @value{GDBN}, you are ready to
14574 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
14575 (or @code{sparclet-aout-gdb}, depending on your installation).
14577 @value{GDBN} comes up showing the prompt:
14584 * Sparclet File:: Setting the file to debug
14585 * Sparclet Connection:: Connecting to Sparclet
14586 * Sparclet Download:: Sparclet download
14587 * Sparclet Execution:: Running and debugging
14590 @node Sparclet File
14591 @subsubsection Setting file to debug
14593 The @value{GDBN} command @code{file} lets you choose with program to debug.
14596 (gdbslet) file prog
14600 @value{GDBN} then attempts to read the symbol table of @file{prog}.
14601 @value{GDBN} locates
14602 the file by searching the directories listed in the command search
14604 If the file was compiled with debug information (option "-g"), source
14605 files will be searched as well.
14606 @value{GDBN} locates
14607 the source files by searching the directories listed in the directory search
14608 path (@pxref{Environment, ,Your program's environment}).
14610 to find a file, it displays a message such as:
14613 prog: No such file or directory.
14616 When this happens, add the appropriate directories to the search paths with
14617 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
14618 @code{target} command again.
14620 @node Sparclet Connection
14621 @subsubsection Connecting to Sparclet
14623 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
14624 To connect to a target on serial port ``@code{ttya}'', type:
14627 (gdbslet) target sparclet /dev/ttya
14628 Remote target sparclet connected to /dev/ttya
14629 main () at ../prog.c:3
14633 @value{GDBN} displays messages like these:
14639 @node Sparclet Download
14640 @subsubsection Sparclet download
14642 @cindex download to Sparclet
14643 Once connected to the Sparclet target,
14644 you can use the @value{GDBN}
14645 @code{load} command to download the file from the host to the target.
14646 The file name and load offset should be given as arguments to the @code{load}
14648 Since the file format is aout, the program must be loaded to the starting
14649 address. You can use @code{objdump} to find out what this value is. The load
14650 offset is an offset which is added to the VMA (virtual memory address)
14651 of each of the file's sections.
14652 For instance, if the program
14653 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
14654 and bss at 0x12010170, in @value{GDBN}, type:
14657 (gdbslet) load prog 0x12010000
14658 Loading section .text, size 0xdb0 vma 0x12010000
14661 If the code is loaded at a different address then what the program was linked
14662 to, you may need to use the @code{section} and @code{add-symbol-file} commands
14663 to tell @value{GDBN} where to map the symbol table.
14665 @node Sparclet Execution
14666 @subsubsection Running and debugging
14668 @cindex running and debugging Sparclet programs
14669 You can now begin debugging the task using @value{GDBN}'s execution control
14670 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
14671 manual for the list of commands.
14675 Breakpoint 1 at 0x12010000: file prog.c, line 3.
14677 Starting program: prog
14678 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
14679 3 char *symarg = 0;
14681 4 char *execarg = "hello!";
14686 @subsection Fujitsu Sparclite
14690 @kindex target sparclite
14691 @item target sparclite @var{dev}
14692 Fujitsu sparclite boards, used only for the purpose of loading.
14693 You must use an additional command to debug the program.
14694 For example: target remote @var{dev} using @value{GDBN} standard
14700 @subsection Tandem ST2000
14702 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
14705 To connect your ST2000 to the host system, see the manufacturer's
14706 manual. Once the ST2000 is physically attached, you can run:
14709 target st2000 @var{dev} @var{speed}
14713 to establish it as your debugging environment. @var{dev} is normally
14714 the name of a serial device, such as @file{/dev/ttya}, connected to the
14715 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
14716 connection (for example, to a serial line attached via a terminal
14717 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
14719 The @code{load} and @code{attach} commands are @emph{not} defined for
14720 this target; you must load your program into the ST2000 as you normally
14721 would for standalone operation. @value{GDBN} reads debugging information
14722 (such as symbols) from a separate, debugging version of the program
14723 available on your host computer.
14724 @c FIXME!! This is terribly vague; what little content is here is
14725 @c basically hearsay.
14727 @cindex ST2000 auxiliary commands
14728 These auxiliary @value{GDBN} commands are available to help you with the ST2000
14732 @item st2000 @var{command}
14733 @kindex st2000 @var{cmd}
14734 @cindex STDBUG commands (ST2000)
14735 @cindex commands to STDBUG (ST2000)
14736 Send a @var{command} to the STDBUG monitor. See the manufacturer's
14737 manual for available commands.
14740 @cindex connect (to STDBUG)
14741 Connect the controlling terminal to the STDBUG command monitor. When
14742 you are done interacting with STDBUG, typing either of two character
14743 sequences gets you back to the @value{GDBN} command prompt:
14744 @kbd{@key{RET}~.} (Return, followed by tilde and period) or
14745 @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
14749 @subsection Zilog Z8000
14752 @cindex simulator, Z8000
14753 @cindex Zilog Z8000 simulator
14755 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
14758 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
14759 unsegmented variant of the Z8000 architecture) or the Z8001 (the
14760 segmented variant). The simulator recognizes which architecture is
14761 appropriate by inspecting the object code.
14764 @item target sim @var{args}
14766 @kindex target sim@r{, with Z8000}
14767 Debug programs on a simulated CPU. If the simulator supports setup
14768 options, specify them via @var{args}.
14772 After specifying this target, you can debug programs for the simulated
14773 CPU in the same style as programs for your host computer; use the
14774 @code{file} command to load a new program image, the @code{run} command
14775 to run your program, and so on.
14777 As well as making available all the usual machine registers
14778 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
14779 additional items of information as specially named registers:
14784 Counts clock-ticks in the simulator.
14787 Counts instructions run in the simulator.
14790 Execution time in 60ths of a second.
14794 You can refer to these values in @value{GDBN} expressions with the usual
14795 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
14796 conditional breakpoint that suspends only after at least 5000
14797 simulated clock ticks.
14800 @subsection Atmel AVR
14803 When configured for debugging the Atmel AVR, @value{GDBN} supports the
14804 following AVR-specific commands:
14807 @item info io_registers
14808 @kindex info io_registers@r{, AVR}
14809 @cindex I/O registers (Atmel AVR)
14810 This command displays information about the AVR I/O registers. For
14811 each register, @value{GDBN} prints its number and value.
14818 When configured for debugging CRIS, @value{GDBN} provides the
14819 following CRIS-specific commands:
14822 @item set cris-version @var{ver}
14823 @cindex CRIS version
14824 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
14825 The CRIS version affects register names and sizes. This command is useful in
14826 case autodetection of the CRIS version fails.
14828 @item show cris-version
14829 Show the current CRIS version.
14831 @item set cris-dwarf2-cfi
14832 @cindex DWARF-2 CFI and CRIS
14833 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
14834 Change to @samp{off} when using @code{gcc-cris} whose version is below
14837 @item show cris-dwarf2-cfi
14838 Show the current state of using DWARF-2 CFI.
14840 @item set cris-mode @var{mode}
14842 Set the current CRIS mode to @var{mode}. It should only be changed when
14843 debugging in guru mode, in which case it should be set to
14844 @samp{guru} (the default is @samp{normal}).
14846 @item show cris-mode
14847 Show the current CRIS mode.
14851 @subsection Renesas Super-H
14854 For the Renesas Super-H processor, @value{GDBN} provides these
14859 @kindex regs@r{, Super-H}
14860 Show the values of all Super-H registers.
14864 @subsection Windows CE
14867 The following commands are available for Windows CE:
14870 @item set remotedirectory @var{dir}
14871 @kindex set remotedirectory
14872 Tell @value{GDBN} to upload files from the named directory @var{dir}.
14873 The default is @file{/gdb}, i.e.@: the root directory on the current
14876 @item show remotedirectory
14877 @kindex show remotedirectory
14878 Show the current value of the upload directory.
14880 @item set remoteupload @var{method}
14881 @kindex set remoteupload
14882 Set the method used to upload files to remote device. Valid values
14883 for @var{method} are @samp{always}, @samp{newer}, and @samp{never}.
14884 The default is @samp{newer}.
14886 @item show remoteupload
14887 @kindex show remoteupload
14888 Show the current setting of the upload method.
14890 @item set remoteaddhost
14891 @kindex set remoteaddhost
14892 Tell @value{GDBN} whether to add this host to the remote stub's
14893 arguments when you debug over a network.
14895 @item show remoteaddhost
14896 @kindex show remoteaddhost
14897 Show whether to add this host to remote stub's arguments when
14898 debugging over a network.
14902 @node Architectures
14903 @section Architectures
14905 This section describes characteristics of architectures that affect
14906 all uses of @value{GDBN} with the architecture, both native and cross.
14913 * HPPA:: HP PA architecture
14917 @subsection x86 Architecture-specific issues.
14920 @item set struct-convention @var{mode}
14921 @kindex set struct-convention
14922 @cindex struct return convention
14923 @cindex struct/union returned in registers
14924 Set the convention used by the inferior to return @code{struct}s and
14925 @code{union}s from functions to @var{mode}. Possible values of
14926 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
14927 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
14928 are returned on the stack, while @code{"reg"} means that a
14929 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
14930 be returned in a register.
14932 @item show struct-convention
14933 @kindex show struct-convention
14934 Show the current setting of the convention to return @code{struct}s
14943 @kindex set rstack_high_address
14944 @cindex AMD 29K register stack
14945 @cindex register stack, AMD29K
14946 @item set rstack_high_address @var{address}
14947 On AMD 29000 family processors, registers are saved in a separate
14948 @dfn{register stack}. There is no way for @value{GDBN} to determine the
14949 extent of this stack. Normally, @value{GDBN} just assumes that the
14950 stack is ``large enough''. This may result in @value{GDBN} referencing
14951 memory locations that do not exist. If necessary, you can get around
14952 this problem by specifying the ending address of the register stack with
14953 the @code{set rstack_high_address} command. The argument should be an
14954 address, which you probably want to precede with @samp{0x} to specify in
14957 @kindex show rstack_high_address
14958 @item show rstack_high_address
14959 Display the current limit of the register stack, on AMD 29000 family
14967 See the following section.
14972 @cindex stack on Alpha
14973 @cindex stack on MIPS
14974 @cindex Alpha stack
14976 Alpha- and MIPS-based computers use an unusual stack frame, which
14977 sometimes requires @value{GDBN} to search backward in the object code to
14978 find the beginning of a function.
14980 @cindex response time, MIPS debugging
14981 To improve response time (especially for embedded applications, where
14982 @value{GDBN} may be restricted to a slow serial line for this search)
14983 you may want to limit the size of this search, using one of these
14987 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
14988 @item set heuristic-fence-post @var{limit}
14989 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
14990 search for the beginning of a function. A value of @var{0} (the
14991 default) means there is no limit. However, except for @var{0}, the
14992 larger the limit the more bytes @code{heuristic-fence-post} must search
14993 and therefore the longer it takes to run. You should only need to use
14994 this command when debugging a stripped executable.
14996 @item show heuristic-fence-post
14997 Display the current limit.
15001 These commands are available @emph{only} when @value{GDBN} is configured
15002 for debugging programs on Alpha or MIPS processors.
15004 Several MIPS-specific commands are available when debugging MIPS
15008 @item set mips saved-gpreg-size @var{size}
15009 @kindex set mips saved-gpreg-size
15010 @cindex MIPS GP register size on stack
15011 Set the size of MIPS general-purpose registers saved on the stack.
15012 The argument @var{size} can be one of the following:
15016 32-bit GP registers
15018 64-bit GP registers
15020 Use the target's default setting or autodetect the saved size from the
15021 information contained in the executable. This is the default
15024 @item show mips saved-gpreg-size
15025 @kindex show mips saved-gpreg-size
15026 Show the current size of MIPS GP registers on the stack.
15028 @item set mips stack-arg-size @var{size}
15029 @kindex set mips stack-arg-size
15030 @cindex MIPS stack space for arguments
15031 Set the amount of stack space reserved for arguments to functions.
15032 The argument can be one of @code{"32"}, @code{"64"} or @code{"auto"}
15035 @item set mips abi @var{arg}
15036 @kindex set mips abi
15037 @cindex set ABI for MIPS
15038 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
15039 values of @var{arg} are:
15043 The default ABI associated with the current binary (this is the
15054 @item show mips abi
15055 @kindex show mips abi
15056 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
15059 @itemx show mipsfpu
15060 @xref{MIPS Embedded, set mipsfpu}.
15062 @item set mips mask-address @var{arg}
15063 @kindex set mips mask-address
15064 @cindex MIPS addresses, masking
15065 This command determines whether the most-significant 32 bits of 64-bit
15066 MIPS addresses are masked off. The argument @var{arg} can be
15067 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
15068 setting, which lets @value{GDBN} determine the correct value.
15070 @item show mips mask-address
15071 @kindex show mips mask-address
15072 Show whether the upper 32 bits of MIPS addresses are masked off or
15075 @item set remote-mips64-transfers-32bit-regs
15076 @kindex set remote-mips64-transfers-32bit-regs
15077 This command controls compatibility with 64-bit MIPS targets that
15078 transfer data in 32-bit quantities. If you have an old MIPS 64 target
15079 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
15080 and 64 bits for other registers, set this option to @samp{on}.
15082 @item show remote-mips64-transfers-32bit-regs
15083 @kindex show remote-mips64-transfers-32bit-regs
15084 Show the current setting of compatibility with older MIPS 64 targets.
15086 @item set debug mips
15087 @kindex set debug mips
15088 This command turns on and off debugging messages for the MIPS-specific
15089 target code in @value{GDBN}.
15091 @item show debug mips
15092 @kindex show debug mips
15093 Show the current setting of MIPS debugging messages.
15099 @cindex HPPA support
15101 When @value{GDBN} is debugging te HP PA architecture, it provides the
15102 following special commands:
15105 @item set debug hppa
15106 @kindex set debug hppa
15107 THis command determines whether HPPA architecture specific debugging
15108 messages are to be displayed.
15110 @item show debug hppa
15111 Show whether HPPA debugging messages are displayed.
15113 @item maint print unwind @var{address}
15114 @kindex maint print unwind@r{, HPPA}
15115 This command displays the contents of the unwind table entry at the
15116 given @var{address}.
15121 @node Controlling GDB
15122 @chapter Controlling @value{GDBN}
15124 You can alter the way @value{GDBN} interacts with you by using the
15125 @code{set} command. For commands controlling how @value{GDBN} displays
15126 data, see @ref{Print Settings, ,Print settings}. Other settings are
15131 * Editing:: Command editing
15132 * Command History:: Command history
15133 * Screen Size:: Screen size
15134 * Numbers:: Numbers
15135 * ABI:: Configuring the current ABI
15136 * Messages/Warnings:: Optional warnings and messages
15137 * Debugging Output:: Optional messages about internal happenings
15145 @value{GDBN} indicates its readiness to read a command by printing a string
15146 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
15147 can change the prompt string with the @code{set prompt} command. For
15148 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
15149 the prompt in one of the @value{GDBN} sessions so that you can always tell
15150 which one you are talking to.
15152 @emph{Note:} @code{set prompt} does not add a space for you after the
15153 prompt you set. This allows you to set a prompt which ends in a space
15154 or a prompt that does not.
15158 @item set prompt @var{newprompt}
15159 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
15161 @kindex show prompt
15163 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
15167 @section Command editing
15169 @cindex command line editing
15171 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
15172 @sc{gnu} library provides consistent behavior for programs which provide a
15173 command line interface to the user. Advantages are @sc{gnu} Emacs-style
15174 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
15175 substitution, and a storage and recall of command history across
15176 debugging sessions.
15178 You may control the behavior of command line editing in @value{GDBN} with the
15179 command @code{set}.
15182 @kindex set editing
15185 @itemx set editing on
15186 Enable command line editing (enabled by default).
15188 @item set editing off
15189 Disable command line editing.
15191 @kindex show editing
15193 Show whether command line editing is enabled.
15196 @xref{Command Line Editing}, for more details about the Readline
15197 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
15198 encouraged to read that chapter.
15200 @node Command History
15201 @section Command history
15202 @cindex command history
15204 @value{GDBN} can keep track of the commands you type during your
15205 debugging sessions, so that you can be certain of precisely what
15206 happened. Use these commands to manage the @value{GDBN} command
15209 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
15210 package, to provide the history facility. @xref{Using History
15211 Interactively}, for the detailed description of the History library.
15213 To issue a command to @value{GDBN} without affecting certain aspects of
15214 the state which is seen by users, prefix it with @samp{server }. This
15215 means that this command will not affect the command history, nor will it
15216 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
15217 pressed on a line by itself.
15219 @cindex @code{server}, command prefix
15220 The server prefix does not affect the recording of values into the value
15221 history; to print a value without recording it into the value history,
15222 use the @code{output} command instead of the @code{print} command.
15224 Here is the description of @value{GDBN} commands related to command
15228 @cindex history substitution
15229 @cindex history file
15230 @kindex set history filename
15231 @cindex @env{GDBHISTFILE}, environment variable
15232 @item set history filename @var{fname}
15233 Set the name of the @value{GDBN} command history file to @var{fname}.
15234 This is the file where @value{GDBN} reads an initial command history
15235 list, and where it writes the command history from this session when it
15236 exits. You can access this list through history expansion or through
15237 the history command editing characters listed below. This file defaults
15238 to the value of the environment variable @code{GDBHISTFILE}, or to
15239 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
15242 @cindex save command history
15243 @kindex set history save
15244 @item set history save
15245 @itemx set history save on
15246 Record command history in a file, whose name may be specified with the
15247 @code{set history filename} command. By default, this option is disabled.
15249 @item set history save off
15250 Stop recording command history in a file.
15252 @cindex history size
15253 @kindex set history size
15254 @cindex @env{HISTSIZE}, environment variable
15255 @item set history size @var{size}
15256 Set the number of commands which @value{GDBN} keeps in its history list.
15257 This defaults to the value of the environment variable
15258 @code{HISTSIZE}, or to 256 if this variable is not set.
15261 History expansion assigns special meaning to the character @kbd{!}.
15262 @xref{Event Designators}, for more details.
15264 @cindex history expansion, turn on/off
15265 Since @kbd{!} is also the logical not operator in C, history expansion
15266 is off by default. If you decide to enable history expansion with the
15267 @code{set history expansion on} command, you may sometimes need to
15268 follow @kbd{!} (when it is used as logical not, in an expression) with
15269 a space or a tab to prevent it from being expanded. The readline
15270 history facilities do not attempt substitution on the strings
15271 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
15273 The commands to control history expansion are:
15276 @item set history expansion on
15277 @itemx set history expansion
15278 @kindex set history expansion
15279 Enable history expansion. History expansion is off by default.
15281 @item set history expansion off
15282 Disable history expansion.
15285 @kindex show history
15287 @itemx show history filename
15288 @itemx show history save
15289 @itemx show history size
15290 @itemx show history expansion
15291 These commands display the state of the @value{GDBN} history parameters.
15292 @code{show history} by itself displays all four states.
15297 @kindex show commands
15298 @cindex show last commands
15299 @cindex display command history
15300 @item show commands
15301 Display the last ten commands in the command history.
15303 @item show commands @var{n}
15304 Print ten commands centered on command number @var{n}.
15306 @item show commands +
15307 Print ten commands just after the commands last printed.
15311 @section Screen size
15312 @cindex size of screen
15313 @cindex pauses in output
15315 Certain commands to @value{GDBN} may produce large amounts of
15316 information output to the screen. To help you read all of it,
15317 @value{GDBN} pauses and asks you for input at the end of each page of
15318 output. Type @key{RET} when you want to continue the output, or @kbd{q}
15319 to discard the remaining output. Also, the screen width setting
15320 determines when to wrap lines of output. Depending on what is being
15321 printed, @value{GDBN} tries to break the line at a readable place,
15322 rather than simply letting it overflow onto the following line.
15324 Normally @value{GDBN} knows the size of the screen from the terminal
15325 driver software. For example, on Unix @value{GDBN} uses the termcap data base
15326 together with the value of the @code{TERM} environment variable and the
15327 @code{stty rows} and @code{stty cols} settings. If this is not correct,
15328 you can override it with the @code{set height} and @code{set
15335 @kindex show height
15336 @item set height @var{lpp}
15338 @itemx set width @var{cpl}
15340 These @code{set} commands specify a screen height of @var{lpp} lines and
15341 a screen width of @var{cpl} characters. The associated @code{show}
15342 commands display the current settings.
15344 If you specify a height of zero lines, @value{GDBN} does not pause during
15345 output no matter how long the output is. This is useful if output is to a
15346 file or to an editor buffer.
15348 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
15349 from wrapping its output.
15351 @item set pagination on
15352 @itemx set pagination off
15353 @kindex set pagination
15354 Turn the output pagination on or off; the default is on. Turning
15355 pagination off is the alternative to @code{set height 0}.
15357 @item show pagination
15358 @kindex show pagination
15359 Show the current pagination mode.
15364 @cindex number representation
15365 @cindex entering numbers
15367 You can always enter numbers in octal, decimal, or hexadecimal in
15368 @value{GDBN} by the usual conventions: octal numbers begin with
15369 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
15370 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
15371 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
15372 10; likewise, the default display for numbers---when no particular
15373 format is specified---is base 10. You can change the default base for
15374 both input and output with the commands described below.
15377 @kindex set input-radix
15378 @item set input-radix @var{base}
15379 Set the default base for numeric input. Supported choices
15380 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15381 specified either unambiguously or using the current input radix; for
15385 set input-radix 012
15386 set input-radix 10.
15387 set input-radix 0xa
15391 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
15392 leaves the input radix unchanged, no matter what it was, since
15393 @samp{10}, being without any leading or trailing signs of its base, is
15394 interpreted in the current radix. Thus, if the current radix is 16,
15395 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
15398 @kindex set output-radix
15399 @item set output-radix @var{base}
15400 Set the default base for numeric display. Supported choices
15401 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15402 specified either unambiguously or using the current input radix.
15404 @kindex show input-radix
15405 @item show input-radix
15406 Display the current default base for numeric input.
15408 @kindex show output-radix
15409 @item show output-radix
15410 Display the current default base for numeric display.
15412 @item set radix @r{[}@var{base}@r{]}
15416 These commands set and show the default base for both input and output
15417 of numbers. @code{set radix} sets the radix of input and output to
15418 the same base; without an argument, it resets the radix back to its
15419 default value of 10.
15424 @section Configuring the current ABI
15426 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
15427 application automatically. However, sometimes you need to override its
15428 conclusions. Use these commands to manage @value{GDBN}'s view of the
15435 One @value{GDBN} configuration can debug binaries for multiple operating
15436 system targets, either via remote debugging or native emulation.
15437 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
15438 but you can override its conclusion using the @code{set osabi} command.
15439 One example where this is useful is in debugging of binaries which use
15440 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
15441 not have the same identifying marks that the standard C library for your
15446 Show the OS ABI currently in use.
15449 With no argument, show the list of registered available OS ABI's.
15451 @item set osabi @var{abi}
15452 Set the current OS ABI to @var{abi}.
15455 @cindex float promotion
15457 Generally, the way that an argument of type @code{float} is passed to a
15458 function depends on whether the function is prototyped. For a prototyped
15459 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
15460 according to the architecture's convention for @code{float}. For unprototyped
15461 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
15462 @code{double} and then passed.
15464 Unfortunately, some forms of debug information do not reliably indicate whether
15465 a function is prototyped. If @value{GDBN} calls a function that is not marked
15466 as prototyped, it consults @kbd{set coerce-float-to-double}.
15469 @kindex set coerce-float-to-double
15470 @item set coerce-float-to-double
15471 @itemx set coerce-float-to-double on
15472 Arguments of type @code{float} will be promoted to @code{double} when passed
15473 to an unprototyped function. This is the default setting.
15475 @item set coerce-float-to-double off
15476 Arguments of type @code{float} will be passed directly to unprototyped
15479 @kindex show coerce-float-to-double
15480 @item show coerce-float-to-double
15481 Show the current setting of promoting @code{float} to @code{double}.
15485 @kindex show cp-abi
15486 @value{GDBN} needs to know the ABI used for your program's C@t{++}
15487 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
15488 used to build your application. @value{GDBN} only fully supports
15489 programs with a single C@t{++} ABI; if your program contains code using
15490 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
15491 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
15492 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
15493 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
15494 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
15495 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
15500 Show the C@t{++} ABI currently in use.
15503 With no argument, show the list of supported C@t{++} ABI's.
15505 @item set cp-abi @var{abi}
15506 @itemx set cp-abi auto
15507 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
15510 @node Messages/Warnings
15511 @section Optional warnings and messages
15513 @cindex verbose operation
15514 @cindex optional warnings
15515 By default, @value{GDBN} is silent about its inner workings. If you are
15516 running on a slow machine, you may want to use the @code{set verbose}
15517 command. This makes @value{GDBN} tell you when it does a lengthy
15518 internal operation, so you will not think it has crashed.
15520 Currently, the messages controlled by @code{set verbose} are those
15521 which announce that the symbol table for a source file is being read;
15522 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
15525 @kindex set verbose
15526 @item set verbose on
15527 Enables @value{GDBN} output of certain informational messages.
15529 @item set verbose off
15530 Disables @value{GDBN} output of certain informational messages.
15532 @kindex show verbose
15534 Displays whether @code{set verbose} is on or off.
15537 By default, if @value{GDBN} encounters bugs in the symbol table of an
15538 object file, it is silent; but if you are debugging a compiler, you may
15539 find this information useful (@pxref{Symbol Errors, ,Errors reading
15544 @kindex set complaints
15545 @item set complaints @var{limit}
15546 Permits @value{GDBN} to output @var{limit} complaints about each type of
15547 unusual symbols before becoming silent about the problem. Set
15548 @var{limit} to zero to suppress all complaints; set it to a large number
15549 to prevent complaints from being suppressed.
15551 @kindex show complaints
15552 @item show complaints
15553 Displays how many symbol complaints @value{GDBN} is permitted to produce.
15557 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
15558 lot of stupid questions to confirm certain commands. For example, if
15559 you try to run a program which is already running:
15563 The program being debugged has been started already.
15564 Start it from the beginning? (y or n)
15567 If you are willing to unflinchingly face the consequences of your own
15568 commands, you can disable this ``feature'':
15572 @kindex set confirm
15574 @cindex confirmation
15575 @cindex stupid questions
15576 @item set confirm off
15577 Disables confirmation requests.
15579 @item set confirm on
15580 Enables confirmation requests (the default).
15582 @kindex show confirm
15584 Displays state of confirmation requests.
15588 @node Debugging Output
15589 @section Optional messages about internal happenings
15590 @cindex optional debugging messages
15592 @value{GDBN} has commands that enable optional debugging messages from
15593 various @value{GDBN} subsystems; normally these commands are of
15594 interest to @value{GDBN} maintainers, or when reporting a bug. This
15595 section documents those commands.
15598 @kindex set exec-done-display
15599 @item set exec-done-display
15600 Turns on or off the notification of asynchronous commands'
15601 completion. When on, @value{GDBN} will print a message when an
15602 asynchronous command finishes its execution. The default is off.
15603 @kindex show exec-done-display
15604 @item show exec-done-display
15605 Displays the current setting of asynchronous command completion
15608 @cindex gdbarch debugging info
15609 @cindex architecture debugging info
15610 @item set debug arch
15611 Turns on or off display of gdbarch debugging info. The default is off
15613 @item show debug arch
15614 Displays the current state of displaying gdbarch debugging info.
15615 @item set debug aix-thread
15616 @cindex AIX threads
15617 Display debugging messages about inner workings of the AIX thread
15619 @item show debug aix-thread
15620 Show the current state of AIX thread debugging info display.
15621 @item set debug event
15622 @cindex event debugging info
15623 Turns on or off display of @value{GDBN} event debugging info. The
15625 @item show debug event
15626 Displays the current state of displaying @value{GDBN} event debugging
15628 @item set debug expression
15629 @cindex expression debugging info
15630 Turns on or off display of debugging info about @value{GDBN}
15631 expression parsing. The default is off.
15632 @item show debug expression
15633 Displays the current state of displaying debugging info about
15634 @value{GDBN} expression parsing.
15635 @item set debug frame
15636 @cindex frame debugging info
15637 Turns on or off display of @value{GDBN} frame debugging info. The
15639 @item show debug frame
15640 Displays the current state of displaying @value{GDBN} frame debugging
15642 @item set debug infrun
15643 @cindex inferior debugging info
15644 Turns on or off display of @value{GDBN} debugging info for running the inferior.
15645 The default is off. @file{infrun.c} contains GDB's runtime state machine used
15646 for implementing operations such as single-stepping the inferior.
15647 @item show debug infrun
15648 Displays the current state of @value{GDBN} inferior debugging.
15649 @item set debug lin-lwp
15650 @cindex @sc{gnu}/Linux LWP debug messages
15651 @cindex Linux lightweight processes
15652 Turns on or off debugging messages from the Linux LWP debug support.
15653 @item show debug lin-lwp
15654 Show the current state of Linux LWP debugging messages.
15655 @item set debug observer
15656 @cindex observer debugging info
15657 Turns on or off display of @value{GDBN} observer debugging. This
15658 includes info such as the notification of observable events.
15659 @item show debug observer
15660 Displays the current state of observer debugging.
15661 @item set debug overload
15662 @cindex C@t{++} overload debugging info
15663 Turns on or off display of @value{GDBN} C@t{++} overload debugging
15664 info. This includes info such as ranking of functions, etc. The default
15666 @item show debug overload
15667 Displays the current state of displaying @value{GDBN} C@t{++} overload
15669 @cindex packets, reporting on stdout
15670 @cindex serial connections, debugging
15671 @item set debug remote
15672 Turns on or off display of reports on all packets sent back and forth across
15673 the serial line to the remote machine. The info is printed on the
15674 @value{GDBN} standard output stream. The default is off.
15675 @item show debug remote
15676 Displays the state of display of remote packets.
15677 @item set debug serial
15678 Turns on or off display of @value{GDBN} serial debugging info. The
15680 @item show debug serial
15681 Displays the current state of displaying @value{GDBN} serial debugging
15683 @item set debug solib-frv
15684 @cindex FR-V shared-library debugging
15685 Turns on or off debugging messages for FR-V shared-library code.
15686 @item show debug solib-frv
15687 Display the current state of FR-V shared-library code debugging
15689 @item set debug target
15690 @cindex target debugging info
15691 Turns on or off display of @value{GDBN} target debugging info. This info
15692 includes what is going on at the target level of GDB, as it happens. The
15693 default is 0. Set it to 1 to track events, and to 2 to also track the
15694 value of large memory transfers. Changes to this flag do not take effect
15695 until the next time you connect to a target or use the @code{run} command.
15696 @item show debug target
15697 Displays the current state of displaying @value{GDBN} target debugging
15699 @item set debugvarobj
15700 @cindex variable object debugging info
15701 Turns on or off display of @value{GDBN} variable object debugging
15702 info. The default is off.
15703 @item show debugvarobj
15704 Displays the current state of displaying @value{GDBN} variable object
15709 @chapter Canned Sequences of Commands
15711 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
15712 command lists}), @value{GDBN} provides two ways to store sequences of
15713 commands for execution as a unit: user-defined commands and command
15717 * Define:: User-defined commands
15718 * Hooks:: User-defined command hooks
15719 * Command Files:: Command files
15720 * Output:: Commands for controlled output
15724 @section User-defined commands
15726 @cindex user-defined command
15727 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
15728 which you assign a new name as a command. This is done with the
15729 @code{define} command. User commands may accept up to 10 arguments
15730 separated by whitespace. Arguments are accessed within the user command
15731 via @code{$arg0@dots{}$arg9}. A trivial example:
15735 print $arg0 + $arg1 + $arg2
15740 To execute the command use:
15747 This defines the command @code{adder}, which prints the sum of
15748 its three arguments. Note the arguments are text substitutions, so they may
15749 reference variables, use complex expressions, or even perform inferior
15752 In addition, @code{$argc} may be used to find out how many arguments have
15753 been passed. This expands to a number in the range 0@dots{}10.
15758 print $arg0 + $arg1
15761 print $arg0 + $arg1 + $arg2
15769 @item define @var{commandname}
15770 Define a command named @var{commandname}. If there is already a command
15771 by that name, you are asked to confirm that you want to redefine it.
15773 The definition of the command is made up of other @value{GDBN} command lines,
15774 which are given following the @code{define} command. The end of these
15775 commands is marked by a line containing @code{end}.
15781 Takes a single argument, which is an expression to evaluate.
15782 It is followed by a series of commands that are executed
15783 only if the expression is true (nonzero).
15784 There can then optionally be a line @code{else}, followed
15785 by a series of commands that are only executed if the expression
15786 was false. The end of the list is marked by a line containing @code{end}.
15790 The syntax is similar to @code{if}: the command takes a single argument,
15791 which is an expression to evaluate, and must be followed by the commands to
15792 execute, one per line, terminated by an @code{end}.
15793 The commands are executed repeatedly as long as the expression
15797 @item document @var{commandname}
15798 Document the user-defined command @var{commandname}, so that it can be
15799 accessed by @code{help}. The command @var{commandname} must already be
15800 defined. This command reads lines of documentation just as @code{define}
15801 reads the lines of the command definition, ending with @code{end}.
15802 After the @code{document} command is finished, @code{help} on command
15803 @var{commandname} displays the documentation you have written.
15805 You may use the @code{document} command again to change the
15806 documentation of a command. Redefining the command with @code{define}
15807 does not change the documentation.
15809 @kindex dont-repeat
15810 @cindex don't repeat command
15812 Used inside a user-defined command, this tells @value{GDBN} that this
15813 command should not be repeated when the user hits @key{RET}
15814 (@pxref{Command Syntax, repeat last command}).
15816 @kindex help user-defined
15817 @item help user-defined
15818 List all user-defined commands, with the first line of the documentation
15823 @itemx show user @var{commandname}
15824 Display the @value{GDBN} commands used to define @var{commandname} (but
15825 not its documentation). If no @var{commandname} is given, display the
15826 definitions for all user-defined commands.
15828 @cindex infinite recusrion in user-defined commands
15829 @kindex show max-user-call-depth
15830 @kindex set max-user-call-depth
15831 @item show max-user-call-depth
15832 @itemx set max-user-call-depth
15833 The value of @code{max-user-call-depth} controls how many recursion
15834 levels are allowed in user-defined commands before GDB suspects an
15835 infinite recursion and aborts the command.
15839 When user-defined commands are executed, the
15840 commands of the definition are not printed. An error in any command
15841 stops execution of the user-defined command.
15843 If used interactively, commands that would ask for confirmation proceed
15844 without asking when used inside a user-defined command. Many @value{GDBN}
15845 commands that normally print messages to say what they are doing omit the
15846 messages when used in a user-defined command.
15849 @section User-defined command hooks
15850 @cindex command hooks
15851 @cindex hooks, for commands
15852 @cindex hooks, pre-command
15855 You may define @dfn{hooks}, which are a special kind of user-defined
15856 command. Whenever you run the command @samp{foo}, if the user-defined
15857 command @samp{hook-foo} exists, it is executed (with no arguments)
15858 before that command.
15860 @cindex hooks, post-command
15862 A hook may also be defined which is run after the command you executed.
15863 Whenever you run the command @samp{foo}, if the user-defined command
15864 @samp{hookpost-foo} exists, it is executed (with no arguments) after
15865 that command. Post-execution hooks may exist simultaneously with
15866 pre-execution hooks, for the same command.
15868 It is valid for a hook to call the command which it hooks. If this
15869 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
15871 @c It would be nice if hookpost could be passed a parameter indicating
15872 @c if the command it hooks executed properly or not. FIXME!
15874 @kindex stop@r{, a pseudo-command}
15875 In addition, a pseudo-command, @samp{stop} exists. Defining
15876 (@samp{hook-stop}) makes the associated commands execute every time
15877 execution stops in your program: before breakpoint commands are run,
15878 displays are printed, or the stack frame is printed.
15880 For example, to ignore @code{SIGALRM} signals while
15881 single-stepping, but treat them normally during normal execution,
15886 handle SIGALRM nopass
15890 handle SIGALRM pass
15893 define hook-continue
15894 handle SIGLARM pass
15898 As a further example, to hook at the begining and end of the @code{echo}
15899 command, and to add extra text to the beginning and end of the message,
15907 define hookpost-echo
15911 (@value{GDBP}) echo Hello World
15912 <<<---Hello World--->>>
15917 You can define a hook for any single-word command in @value{GDBN}, but
15918 not for command aliases; you should define a hook for the basic command
15919 name, e.g.@: @code{backtrace} rather than @code{bt}.
15920 @c FIXME! So how does Joe User discover whether a command is an alias
15922 If an error occurs during the execution of your hook, execution of
15923 @value{GDBN} commands stops and @value{GDBN} issues a prompt
15924 (before the command that you actually typed had a chance to run).
15926 If you try to define a hook which does not match any known command, you
15927 get a warning from the @code{define} command.
15929 @node Command Files
15930 @section Command files
15932 @cindex command files
15933 A command file for @value{GDBN} is a text file made of lines that are
15934 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
15935 also be included. An empty line in a command file does nothing; it
15936 does not mean to repeat the last command, as it would from the
15939 You can request the execution of a command file with the @code{source}
15944 @item source @var{filename}
15945 Execute the command file @var{filename}.
15948 The lines in a command file are executed sequentially. They are not
15949 printed as they are executed. An error in any command terminates
15950 execution of the command file and control is returned to the console.
15952 Commands that would ask for confirmation if used interactively proceed
15953 without asking when used in a command file. Many @value{GDBN} commands that
15954 normally print messages to say what they are doing omit the messages
15955 when called from command files.
15957 @value{GDBN} also accepts command input from standard input. In this
15958 mode, normal output goes to standard output and error output goes to
15959 standard error. Errors in a command file supplied on standard input do
15960 not terminate execution of the command file---execution continues with
15964 gdb < cmds > log 2>&1
15967 (The syntax above will vary depending on the shell used.) This example
15968 will execute commands from the file @file{cmds}. All output and errors
15969 would be directed to @file{log}.
15972 @section Commands for controlled output
15974 During the execution of a command file or a user-defined command, normal
15975 @value{GDBN} output is suppressed; the only output that appears is what is
15976 explicitly printed by the commands in the definition. This section
15977 describes three commands useful for generating exactly the output you
15982 @item echo @var{text}
15983 @c I do not consider backslash-space a standard C escape sequence
15984 @c because it is not in ANSI.
15985 Print @var{text}. Nonprinting characters can be included in
15986 @var{text} using C escape sequences, such as @samp{\n} to print a
15987 newline. @strong{No newline is printed unless you specify one.}
15988 In addition to the standard C escape sequences, a backslash followed
15989 by a space stands for a space. This is useful for displaying a
15990 string with spaces at the beginning or the end, since leading and
15991 trailing spaces are otherwise trimmed from all arguments.
15992 To print @samp{@w{ }and foo =@w{ }}, use the command
15993 @samp{echo \@w{ }and foo = \@w{ }}.
15995 A backslash at the end of @var{text} can be used, as in C, to continue
15996 the command onto subsequent lines. For example,
15999 echo This is some text\n\
16000 which is continued\n\
16001 onto several lines.\n
16004 produces the same output as
16007 echo This is some text\n
16008 echo which is continued\n
16009 echo onto several lines.\n
16013 @item output @var{expression}
16014 Print the value of @var{expression} and nothing but that value: no
16015 newlines, no @samp{$@var{nn} = }. The value is not entered in the
16016 value history either. @xref{Expressions, ,Expressions}, for more information
16019 @item output/@var{fmt} @var{expression}
16020 Print the value of @var{expression} in format @var{fmt}. You can use
16021 the same formats as for @code{print}. @xref{Output Formats,,Output
16022 formats}, for more information.
16025 @item printf @var{string}, @var{expressions}@dots{}
16026 Print the values of the @var{expressions} under the control of
16027 @var{string}. The @var{expressions} are separated by commas and may be
16028 either numbers or pointers. Their values are printed as specified by
16029 @var{string}, exactly as if your program were to execute the C
16031 @c FIXME: the above implies that at least all ANSI C formats are
16032 @c supported, but it isn't true: %E and %G don't work (or so it seems).
16033 @c Either this is a bug, or the manual should document what formats are
16037 printf (@var{string}, @var{expressions}@dots{});
16040 For example, you can print two values in hex like this:
16043 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
16046 The only backslash-escape sequences that you can use in the format
16047 string are the simple ones that consist of backslash followed by a
16052 @chapter Command Interpreters
16053 @cindex command interpreters
16055 @value{GDBN} supports multiple command interpreters, and some command
16056 infrastructure to allow users or user interface writers to switch
16057 between interpreters or run commands in other interpreters.
16059 @value{GDBN} currently supports two command interpreters, the console
16060 interpreter (sometimes called the command-line interpreter or @sc{cli})
16061 and the machine interface interpreter (or @sc{gdb/mi}). This manual
16062 describes both of these interfaces in great detail.
16064 By default, @value{GDBN} will start with the console interpreter.
16065 However, the user may choose to start @value{GDBN} with another
16066 interpreter by specifying the @option{-i} or @option{--interpreter}
16067 startup options. Defined interpreters include:
16071 @cindex console interpreter
16072 The traditional console or command-line interpreter. This is the most often
16073 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
16074 @value{GDBN} will use this interpreter.
16077 @cindex mi interpreter
16078 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
16079 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
16080 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
16084 @cindex mi2 interpreter
16085 The current @sc{gdb/mi} interface.
16088 @cindex mi1 interpreter
16089 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
16093 @cindex invoke another interpreter
16094 The interpreter being used by @value{GDBN} may not be dynamically
16095 switched at runtime. Although possible, this could lead to a very
16096 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
16097 enters the command "interpreter-set console" in a console view,
16098 @value{GDBN} would switch to using the console interpreter, rendering
16099 the IDE inoperable!
16101 @kindex interpreter-exec
16102 Although you may only choose a single interpreter at startup, you may execute
16103 commands in any interpreter from the current interpreter using the appropriate
16104 command. If you are running the console interpreter, simply use the
16105 @code{interpreter-exec} command:
16108 interpreter-exec mi "-data-list-register-names"
16111 @sc{gdb/mi} has a similar command, although it is only available in versions of
16112 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
16115 @chapter @value{GDBN} Text User Interface
16117 @cindex Text User Interface
16120 * TUI Overview:: TUI overview
16121 * TUI Keys:: TUI key bindings
16122 * TUI Single Key Mode:: TUI single key mode
16123 * TUI Commands:: TUI specific commands
16124 * TUI Configuration:: TUI configuration variables
16127 The @value{GDBN} Text User Interface, TUI in short, is a terminal
16128 interface which uses the @code{curses} library to show the source
16129 file, the assembly output, the program registers and @value{GDBN}
16130 commands in separate text windows.
16132 The TUI is enabled by invoking @value{GDBN} using either
16134 @samp{gdbtui} or @samp{gdb -tui}.
16137 @section TUI overview
16139 The TUI has two display modes that can be switched while
16144 A curses (or TUI) mode in which it displays several text
16145 windows on the terminal.
16148 A standard mode which corresponds to the @value{GDBN} configured without
16152 In the TUI mode, @value{GDBN} can display several text window
16157 This window is the @value{GDBN} command window with the @value{GDBN}
16158 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
16159 managed using readline but through the TUI. The @emph{command}
16160 window is always visible.
16163 The source window shows the source file of the program. The current
16164 line as well as active breakpoints are displayed in this window.
16167 The assembly window shows the disassembly output of the program.
16170 This window shows the processor registers. It detects when
16171 a register is changed and when this is the case, registers that have
16172 changed are highlighted.
16176 The source and assembly windows show the current program position
16177 by highlighting the current line and marking them with the @samp{>} marker.
16178 Breakpoints are also indicated with two markers. A first one
16179 indicates the breakpoint type:
16183 Breakpoint which was hit at least once.
16186 Breakpoint which was never hit.
16189 Hardware breakpoint which was hit at least once.
16192 Hardware breakpoint which was never hit.
16196 The second marker indicates whether the breakpoint is enabled or not:
16200 Breakpoint is enabled.
16203 Breakpoint is disabled.
16207 The source, assembly and register windows are attached to the thread
16208 and the frame position. They are updated when the current thread
16209 changes, when the frame changes or when the program counter changes.
16210 These three windows are arranged by the TUI according to several
16211 layouts. The layout defines which of these three windows are visible.
16212 The following layouts are available:
16222 source and assembly
16225 source and registers
16228 assembly and registers
16232 On top of the command window a status line gives various information
16233 concerning the current process begin debugged. The status line is
16234 updated when the information it shows changes. The following fields
16239 Indicates the current gdb target
16240 (@pxref{Targets, ,Specifying a Debugging Target}).
16243 Gives information about the current process or thread number.
16244 When no process is being debugged, this field is set to @code{No process}.
16247 Gives the current function name for the selected frame.
16248 The name is demangled if demangling is turned on (@pxref{Print Settings}).
16249 When there is no symbol corresponding to the current program counter
16250 the string @code{??} is displayed.
16253 Indicates the current line number for the selected frame.
16254 When the current line number is not known the string @code{??} is displayed.
16257 Indicates the current program counter address.
16262 @section TUI Key Bindings
16263 @cindex TUI key bindings
16265 The TUI installs several key bindings in the readline keymaps
16266 (@pxref{Command Line Editing}).
16267 They allow to leave or enter in the TUI mode or they operate
16268 directly on the TUI layout and windows. The TUI also provides
16269 a @emph{SingleKey} keymap which binds several keys directly to
16270 @value{GDBN} commands. The following key bindings
16271 are installed for both TUI mode and the @value{GDBN} standard mode.
16280 Enter or leave the TUI mode. When the TUI mode is left,
16281 the curses window management is left and @value{GDBN} operates using
16282 its standard mode writing on the terminal directly. When the TUI
16283 mode is entered, the control is given back to the curses windows.
16284 The screen is then refreshed.
16288 Use a TUI layout with only one window. The layout will
16289 either be @samp{source} or @samp{assembly}. When the TUI mode
16290 is not active, it will switch to the TUI mode.
16292 Think of this key binding as the Emacs @kbd{C-x 1} binding.
16296 Use a TUI layout with at least two windows. When the current
16297 layout shows already two windows, a next layout with two windows is used.
16298 When a new layout is chosen, one window will always be common to the
16299 previous layout and the new one.
16301 Think of it as the Emacs @kbd{C-x 2} binding.
16305 Change the active window. The TUI associates several key bindings
16306 (like scrolling and arrow keys) to the active window. This command
16307 gives the focus to the next TUI window.
16309 Think of it as the Emacs @kbd{C-x o} binding.
16313 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
16314 (@pxref{TUI Single Key Mode}).
16318 The following key bindings are handled only by the TUI mode:
16323 Scroll the active window one page up.
16327 Scroll the active window one page down.
16331 Scroll the active window one line up.
16335 Scroll the active window one line down.
16339 Scroll the active window one column left.
16343 Scroll the active window one column right.
16347 Refresh the screen.
16351 In the TUI mode, the arrow keys are used by the active window
16352 for scrolling. This means they are available for readline when the
16353 active window is the command window. When the command window
16354 does not have the focus, it is necessary to use other readline
16355 key bindings such as @key{C-p}, @key{C-n}, @key{C-b} and @key{C-f}.
16357 @node TUI Single Key Mode
16358 @section TUI Single Key Mode
16359 @cindex TUI single key mode
16361 The TUI provides a @emph{SingleKey} mode in which it installs a particular
16362 key binding in the readline keymaps to connect single keys to
16366 @kindex c @r{(SingleKey TUI key)}
16370 @kindex d @r{(SingleKey TUI key)}
16374 @kindex f @r{(SingleKey TUI key)}
16378 @kindex n @r{(SingleKey TUI key)}
16382 @kindex q @r{(SingleKey TUI key)}
16384 exit the @emph{SingleKey} mode.
16386 @kindex r @r{(SingleKey TUI key)}
16390 @kindex s @r{(SingleKey TUI key)}
16394 @kindex u @r{(SingleKey TUI key)}
16398 @kindex v @r{(SingleKey TUI key)}
16402 @kindex w @r{(SingleKey TUI key)}
16408 Other keys temporarily switch to the @value{GDBN} command prompt.
16409 The key that was pressed is inserted in the editing buffer so that
16410 it is possible to type most @value{GDBN} commands without interaction
16411 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
16412 @emph{SingleKey} mode is restored. The only way to permanently leave
16413 this mode is by hitting @key{q} or @samp{@key{C-x} @key{s}}.
16417 @section TUI specific commands
16418 @cindex TUI commands
16420 The TUI has specific commands to control the text windows.
16421 These commands are always available, that is they do not depend on
16422 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
16423 is in the standard mode, using these commands will automatically switch
16429 List and give the size of all displayed windows.
16433 Display the next layout.
16436 Display the previous layout.
16439 Display the source window only.
16442 Display the assembly window only.
16445 Display the source and assembly window.
16448 Display the register window together with the source or assembly window.
16450 @item focus next | prev | src | asm | regs | split
16452 Set the focus to the named window.
16453 This command allows to change the active window so that scrolling keys
16454 can be affected to another window.
16458 Refresh the screen. This is similar to using @key{C-L} key.
16460 @item tui reg float
16462 Show the floating point registers in the register window.
16464 @item tui reg general
16465 Show the general registers in the register window.
16468 Show the next register group. The list of register groups as well as
16469 their order is target specific. The predefined register groups are the
16470 following: @code{general}, @code{float}, @code{system}, @code{vector},
16471 @code{all}, @code{save}, @code{restore}.
16473 @item tui reg system
16474 Show the system registers in the register window.
16478 Update the source window and the current execution point.
16480 @item winheight @var{name} +@var{count}
16481 @itemx winheight @var{name} -@var{count}
16483 Change the height of the window @var{name} by @var{count}
16484 lines. Positive counts increase the height, while negative counts
16488 @kindex tabset @var{nchars}
16489 Set the width of tab stops to be @var{nchars} characters.
16493 @node TUI Configuration
16494 @section TUI configuration variables
16495 @cindex TUI configuration variables
16497 The TUI has several configuration variables that control the
16498 appearance of windows on the terminal.
16501 @item set tui border-kind @var{kind}
16502 @kindex set tui border-kind
16503 Select the border appearance for the source, assembly and register windows.
16504 The possible values are the following:
16507 Use a space character to draw the border.
16510 Use ascii characters + - and | to draw the border.
16513 Use the Alternate Character Set to draw the border. The border is
16514 drawn using character line graphics if the terminal supports them.
16518 @item set tui active-border-mode @var{mode}
16519 @kindex set tui active-border-mode
16520 Select the attributes to display the border of the active window.
16521 The possible values are @code{normal}, @code{standout}, @code{reverse},
16522 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
16524 @item set tui border-mode @var{mode}
16525 @kindex set tui border-mode
16526 Select the attributes to display the border of other windows.
16527 The @var{mode} can be one of the following:
16530 Use normal attributes to display the border.
16536 Use reverse video mode.
16539 Use half bright mode.
16541 @item half-standout
16542 Use half bright and standout mode.
16545 Use extra bright or bold mode.
16547 @item bold-standout
16548 Use extra bright or bold and standout mode.
16555 @chapter Using @value{GDBN} under @sc{gnu} Emacs
16558 @cindex @sc{gnu} Emacs
16559 A special interface allows you to use @sc{gnu} Emacs to view (and
16560 edit) the source files for the program you are debugging with
16563 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
16564 executable file you want to debug as an argument. This command starts
16565 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
16566 created Emacs buffer.
16567 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
16569 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
16574 All ``terminal'' input and output goes through the Emacs buffer.
16577 This applies both to @value{GDBN} commands and their output, and to the input
16578 and output done by the program you are debugging.
16580 This is useful because it means that you can copy the text of previous
16581 commands and input them again; you can even use parts of the output
16584 All the facilities of Emacs' Shell mode are available for interacting
16585 with your program. In particular, you can send signals the usual
16586 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
16591 @value{GDBN} displays source code through Emacs.
16594 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
16595 source file for that frame and puts an arrow (@samp{=>}) at the
16596 left margin of the current line. Emacs uses a separate buffer for
16597 source display, and splits the screen to show both your @value{GDBN} session
16600 Explicit @value{GDBN} @code{list} or search commands still produce output as
16601 usual, but you probably have no reason to use them from Emacs.
16603 If you specify an absolute file name when prompted for the @kbd{M-x
16604 gdb} argument, then Emacs sets your current working directory to where
16605 your program resides. If you only specify the file name, then Emacs
16606 sets your current working directory to to the directory associated
16607 with the previous buffer. In this case, @value{GDBN} may find your
16608 program by searching your environment's @code{PATH} variable, but on
16609 some operating systems it might not find the source. So, although the
16610 @value{GDBN} input and output session proceeds normally, the auxiliary
16611 buffer does not display the current source and line of execution.
16613 The initial working directory of @value{GDBN} is printed on the top
16614 line of the @value{GDBN} I/O buffer and this serves as a default for
16615 the commands that specify files for @value{GDBN} to operate
16616 on. @xref{Files, ,Commands to specify files}.
16618 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
16619 need to call @value{GDBN} by a different name (for example, if you
16620 keep several configurations around, with different names) you can
16621 customize the Emacs variable @code{gud-gdb-command-name} to run the
16624 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
16625 addition to the standard Shell mode commands:
16629 Describe the features of Emacs' @value{GDBN} Mode.
16632 Execute to another source line, like the @value{GDBN} @code{step} command; also
16633 update the display window to show the current file and location.
16636 Execute to next source line in this function, skipping all function
16637 calls, like the @value{GDBN} @code{next} command. Then update the display window
16638 to show the current file and location.
16641 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
16642 display window accordingly.
16645 Execute until exit from the selected stack frame, like the @value{GDBN}
16646 @code{finish} command.
16649 Continue execution of your program, like the @value{GDBN} @code{continue}
16653 Go up the number of frames indicated by the numeric argument
16654 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
16655 like the @value{GDBN} @code{up} command.
16658 Go down the number of frames indicated by the numeric argument, like the
16659 @value{GDBN} @code{down} command.
16662 In any source file, the Emacs command @kbd{C-x SPC} (@code{gud-break})
16663 tells @value{GDBN} to set a breakpoint on the source line point is on.
16665 If you type @kbd{M-x speedbar}, then Emacs displays a separate frame which
16666 shows a backtrace when the @value{GDBN} I/O buffer is current. Move
16667 point to any frame in the stack and type @key{RET} to make it become the
16668 current frame and display the associated source in the source buffer.
16669 Alternatively, click @kbd{Mouse-2} to make the selected frame become the
16672 If you accidentally delete the source-display buffer, an easy way to get
16673 it back is to type the command @code{f} in the @value{GDBN} buffer, to
16674 request a frame display; when you run under Emacs, this recreates
16675 the source buffer if necessary to show you the context of the current
16678 The source files displayed in Emacs are in ordinary Emacs buffers
16679 which are visiting the source files in the usual way. You can edit
16680 the files with these buffers if you wish; but keep in mind that @value{GDBN}
16681 communicates with Emacs in terms of line numbers. If you add or
16682 delete lines from the text, the line numbers that @value{GDBN} knows cease
16683 to correspond properly with the code.
16685 The description given here is for GNU Emacs version 21.3 and a more
16686 detailed description of its interaction with @value{GDBN} is given in
16687 the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu} Emacs Manual}).
16689 @c The following dropped because Epoch is nonstandard. Reactivate
16690 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
16692 @kindex Emacs Epoch environment
16696 Version 18 of @sc{gnu} Emacs has a built-in window system
16697 called the @code{epoch}
16698 environment. Users of this environment can use a new command,
16699 @code{inspect} which performs identically to @code{print} except that
16700 each value is printed in its own window.
16705 @chapter The @sc{gdb/mi} Interface
16707 @unnumberedsec Function and Purpose
16709 @cindex @sc{gdb/mi}, its purpose
16710 @sc{gdb/mi} is a line based machine oriented text interface to
16711 @value{GDBN} and is activated by specifying using the
16712 @option{--interpreter} command line option (@pxref{Mode Options}). It
16713 is specifically intended to support the development of systems which
16714 use the debugger as just one small component of a larger system.
16716 This chapter is a specification of the @sc{gdb/mi} interface. It is written
16717 in the form of a reference manual.
16719 Note that @sc{gdb/mi} is still under construction, so some of the
16720 features described below are incomplete and subject to change.
16722 @unnumberedsec Notation and Terminology
16724 @cindex notational conventions, for @sc{gdb/mi}
16725 This chapter uses the following notation:
16729 @code{|} separates two alternatives.
16732 @code{[ @var{something} ]} indicates that @var{something} is optional:
16733 it may or may not be given.
16736 @code{( @var{group} )*} means that @var{group} inside the parentheses
16737 may repeat zero or more times.
16740 @code{( @var{group} )+} means that @var{group} inside the parentheses
16741 may repeat one or more times.
16744 @code{"@var{string}"} means a literal @var{string}.
16748 @heading Dependencies
16751 @heading Acknowledgments
16753 In alphabetic order: Andrew Cagney, Fernando Nasser, Stan Shebs and
16757 * GDB/MI Command Syntax::
16758 * GDB/MI Compatibility with CLI::
16759 * GDB/MI Output Records::
16760 * GDB/MI Command Description Format::
16761 * GDB/MI Breakpoint Table Commands::
16762 * GDB/MI Data Manipulation::
16763 * GDB/MI Program Control::
16764 * GDB/MI Miscellaneous Commands::
16766 * GDB/MI Kod Commands::
16767 * GDB/MI Memory Overlay Commands::
16768 * GDB/MI Signal Handling Commands::
16770 * GDB/MI Stack Manipulation::
16771 * GDB/MI Symbol Query::
16772 * GDB/MI Target Manipulation::
16773 * GDB/MI Thread Commands::
16774 * GDB/MI Tracepoint Commands::
16775 * GDB/MI Variable Objects::
16778 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16779 @node GDB/MI Command Syntax
16780 @section @sc{gdb/mi} Command Syntax
16783 * GDB/MI Input Syntax::
16784 * GDB/MI Output Syntax::
16785 * GDB/MI Simple Examples::
16788 @node GDB/MI Input Syntax
16789 @subsection @sc{gdb/mi} Input Syntax
16791 @cindex input syntax for @sc{gdb/mi}
16792 @cindex @sc{gdb/mi}, input syntax
16794 @item @var{command} @expansion{}
16795 @code{@var{cli-command} | @var{mi-command}}
16797 @item @var{cli-command} @expansion{}
16798 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
16799 @var{cli-command} is any existing @value{GDBN} CLI command.
16801 @item @var{mi-command} @expansion{}
16802 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
16803 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
16805 @item @var{token} @expansion{}
16806 "any sequence of digits"
16808 @item @var{option} @expansion{}
16809 @code{"-" @var{parameter} [ " " @var{parameter} ]}
16811 @item @var{parameter} @expansion{}
16812 @code{@var{non-blank-sequence} | @var{c-string}}
16814 @item @var{operation} @expansion{}
16815 @emph{any of the operations described in this chapter}
16817 @item @var{non-blank-sequence} @expansion{}
16818 @emph{anything, provided it doesn't contain special characters such as
16819 "-", @var{nl}, """ and of course " "}
16821 @item @var{c-string} @expansion{}
16822 @code{""" @var{seven-bit-iso-c-string-content} """}
16824 @item @var{nl} @expansion{}
16833 The CLI commands are still handled by the @sc{mi} interpreter; their
16834 output is described below.
16837 The @code{@var{token}}, when present, is passed back when the command
16841 Some @sc{mi} commands accept optional arguments as part of the parameter
16842 list. Each option is identified by a leading @samp{-} (dash) and may be
16843 followed by an optional argument parameter. Options occur first in the
16844 parameter list and can be delimited from normal parameters using
16845 @samp{--} (this is useful when some parameters begin with a dash).
16852 We want easy access to the existing CLI syntax (for debugging).
16855 We want it to be easy to spot a @sc{mi} operation.
16858 @node GDB/MI Output Syntax
16859 @subsection @sc{gdb/mi} Output Syntax
16861 @cindex output syntax of @sc{gdb/mi}
16862 @cindex @sc{gdb/mi}, output syntax
16863 The output from @sc{gdb/mi} consists of zero or more out-of-band records
16864 followed, optionally, by a single result record. This result record
16865 is for the most recent command. The sequence of output records is
16866 terminated by @samp{(@value{GDBP})}.
16868 If an input command was prefixed with a @code{@var{token}} then the
16869 corresponding output for that command will also be prefixed by that same
16873 @item @var{output} @expansion{}
16874 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(@value{GDBP})" @var{nl}}
16876 @item @var{result-record} @expansion{}
16877 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
16879 @item @var{out-of-band-record} @expansion{}
16880 @code{@var{async-record} | @var{stream-record}}
16882 @item @var{async-record} @expansion{}
16883 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
16885 @item @var{exec-async-output} @expansion{}
16886 @code{[ @var{token} ] "*" @var{async-output}}
16888 @item @var{status-async-output} @expansion{}
16889 @code{[ @var{token} ] "+" @var{async-output}}
16891 @item @var{notify-async-output} @expansion{}
16892 @code{[ @var{token} ] "=" @var{async-output}}
16894 @item @var{async-output} @expansion{}
16895 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
16897 @item @var{result-class} @expansion{}
16898 @code{"done" | "running" | "connected" | "error" | "exit"}
16900 @item @var{async-class} @expansion{}
16901 @code{"stopped" | @var{others}} (where @var{others} will be added
16902 depending on the needs---this is still in development).
16904 @item @var{result} @expansion{}
16905 @code{ @var{variable} "=" @var{value}}
16907 @item @var{variable} @expansion{}
16908 @code{ @var{string} }
16910 @item @var{value} @expansion{}
16911 @code{ @var{const} | @var{tuple} | @var{list} }
16913 @item @var{const} @expansion{}
16914 @code{@var{c-string}}
16916 @item @var{tuple} @expansion{}
16917 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
16919 @item @var{list} @expansion{}
16920 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
16921 @var{result} ( "," @var{result} )* "]" }
16923 @item @var{stream-record} @expansion{}
16924 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
16926 @item @var{console-stream-output} @expansion{}
16927 @code{"~" @var{c-string}}
16929 @item @var{target-stream-output} @expansion{}
16930 @code{"@@" @var{c-string}}
16932 @item @var{log-stream-output} @expansion{}
16933 @code{"&" @var{c-string}}
16935 @item @var{nl} @expansion{}
16938 @item @var{token} @expansion{}
16939 @emph{any sequence of digits}.
16947 All output sequences end in a single line containing a period.
16950 The @code{@var{token}} is from the corresponding request. If an execution
16951 command is interrupted by the @samp{-exec-interrupt} command, the
16952 @var{token} associated with the @samp{*stopped} message is the one of the
16953 original execution command, not the one of the interrupt command.
16956 @cindex status output in @sc{gdb/mi}
16957 @var{status-async-output} contains on-going status information about the
16958 progress of a slow operation. It can be discarded. All status output is
16959 prefixed by @samp{+}.
16962 @cindex async output in @sc{gdb/mi}
16963 @var{exec-async-output} contains asynchronous state change on the target
16964 (stopped, started, disappeared). All async output is prefixed by
16968 @cindex notify output in @sc{gdb/mi}
16969 @var{notify-async-output} contains supplementary information that the
16970 client should handle (e.g., a new breakpoint information). All notify
16971 output is prefixed by @samp{=}.
16974 @cindex console output in @sc{gdb/mi}
16975 @var{console-stream-output} is output that should be displayed as is in the
16976 console. It is the textual response to a CLI command. All the console
16977 output is prefixed by @samp{~}.
16980 @cindex target output in @sc{gdb/mi}
16981 @var{target-stream-output} is the output produced by the target program.
16982 All the target output is prefixed by @samp{@@}.
16985 @cindex log output in @sc{gdb/mi}
16986 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
16987 instance messages that should be displayed as part of an error log. All
16988 the log output is prefixed by @samp{&}.
16991 @cindex list output in @sc{gdb/mi}
16992 New @sc{gdb/mi} commands should only output @var{lists} containing
16998 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
16999 details about the various output records.
17001 @node GDB/MI Simple Examples
17002 @subsection Simple Examples of @sc{gdb/mi} Interaction
17003 @cindex @sc{gdb/mi}, simple examples
17005 This subsection presents several simple examples of interaction using
17006 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
17007 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
17008 the output received from @sc{gdb/mi}.
17010 @subsubheading Target Stop
17011 @c Ummm... There is no "-stop" command. This assumes async, no?
17012 Here's an example of stopping the inferior process:
17023 <- *stop,reason="stop",address="0x123",source="a.c:123"
17027 @subsubheading Simple CLI Command
17029 Here's an example of a simple CLI command being passed through
17030 @sc{gdb/mi} and on to the CLI.
17040 @subsubheading Command With Side Effects
17043 -> -symbol-file xyz.exe
17044 <- *breakpoint,nr="3",address="0x123",source="a.c:123"
17048 @subsubheading A Bad Command
17050 Here's what happens if you pass a non-existent command:
17054 <- ^error,msg="Undefined MI command: rubbish"
17058 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17059 @node GDB/MI Compatibility with CLI
17060 @section @sc{gdb/mi} Compatibility with CLI
17062 @cindex compatibility, @sc{gdb/mi} and CLI
17063 @cindex @sc{gdb/mi}, compatibility with CLI
17064 To help users familiar with @value{GDBN}'s existing CLI interface, @sc{gdb/mi}
17065 accepts existing CLI commands. As specified by the syntax, such
17066 commands can be directly entered into the @sc{gdb/mi} interface and @value{GDBN} will
17069 This mechanism is provided as an aid to developers of @sc{gdb/mi}
17070 clients and not as a reliable interface into the CLI. Since the command
17071 is being interpreteted in an environment that assumes @sc{gdb/mi}
17072 behaviour, the exact output of such commands is likely to end up being
17073 an un-supported hybrid of @sc{gdb/mi} and CLI output.
17075 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17076 @node GDB/MI Output Records
17077 @section @sc{gdb/mi} Output Records
17080 * GDB/MI Result Records::
17081 * GDB/MI Stream Records::
17082 * GDB/MI Out-of-band Records::
17085 @node GDB/MI Result Records
17086 @subsection @sc{gdb/mi} Result Records
17088 @cindex result records in @sc{gdb/mi}
17089 @cindex @sc{gdb/mi}, result records
17090 In addition to a number of out-of-band notifications, the response to a
17091 @sc{gdb/mi} command includes one of the following result indications:
17095 @item "^done" [ "," @var{results} ]
17096 The synchronous operation was successful, @code{@var{results}} are the return
17101 @c Is this one correct? Should it be an out-of-band notification?
17102 The asynchronous operation was successfully started. The target is
17105 @item "^error" "," @var{c-string}
17107 The operation failed. The @code{@var{c-string}} contains the corresponding
17111 @node GDB/MI Stream Records
17112 @subsection @sc{gdb/mi} Stream Records
17114 @cindex @sc{gdb/mi}, stream records
17115 @cindex stream records in @sc{gdb/mi}
17116 @value{GDBN} internally maintains a number of output streams: the console, the
17117 target, and the log. The output intended for each of these streams is
17118 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
17120 Each stream record begins with a unique @dfn{prefix character} which
17121 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
17122 Syntax}). In addition to the prefix, each stream record contains a
17123 @code{@var{string-output}}. This is either raw text (with an implicit new
17124 line) or a quoted C string (which does not contain an implicit newline).
17127 @item "~" @var{string-output}
17128 The console output stream contains text that should be displayed in the
17129 CLI console window. It contains the textual responses to CLI commands.
17131 @item "@@" @var{string-output}
17132 The target output stream contains any textual output from the running
17135 @item "&" @var{string-output}
17136 The log stream contains debugging messages being produced by @value{GDBN}'s
17140 @node GDB/MI Out-of-band Records
17141 @subsection @sc{gdb/mi} Out-of-band Records
17143 @cindex out-of-band records in @sc{gdb/mi}
17144 @cindex @sc{gdb/mi}, out-of-band records
17145 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
17146 additional changes that have occurred. Those changes can either be a
17147 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
17148 target activity (e.g., target stopped).
17150 The following is a preliminary list of possible out-of-band records.
17151 In particular, the @var{exec-async-output} records.
17154 @item *stopped,reason="@var{reason}"
17157 @var{reason} can be one of the following:
17160 @item breakpoint-hit
17161 A breakpoint was reached.
17162 @item watchpoint-trigger
17163 A watchpoint was triggered.
17164 @item read-watchpoint-trigger
17165 A read watchpoint was triggered.
17166 @item access-watchpoint-trigger
17167 An access watchpoint was triggered.
17168 @item function-finished
17169 An -exec-finish or similar CLI command was accomplished.
17170 @item location-reached
17171 An -exec-until or similar CLI command was accomplished.
17172 @item watchpoint-scope
17173 A watchpoint has gone out of scope.
17174 @item end-stepping-range
17175 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
17176 similar CLI command was accomplished.
17177 @item exited-signalled
17178 The inferior exited because of a signal.
17180 The inferior exited.
17181 @item exited-normally
17182 The inferior exited normally.
17183 @item signal-received
17184 A signal was received by the inferior.
17188 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17189 @node GDB/MI Command Description Format
17190 @section @sc{gdb/mi} Command Description Format
17192 The remaining sections describe blocks of commands. Each block of
17193 commands is laid out in a fashion similar to this section.
17195 Note the the line breaks shown in the examples are here only for
17196 readability. They don't appear in the real output.
17197 Also note that the commands with a non-available example (N.A.@:) are
17198 not yet implemented.
17200 @subheading Motivation
17202 The motivation for this collection of commands.
17204 @subheading Introduction
17206 A brief introduction to this collection of commands as a whole.
17208 @subheading Commands
17210 For each command in the block, the following is described:
17212 @subsubheading Synopsis
17215 -command @var{args}@dots{}
17218 @subsubheading Result
17220 @subsubheading @value{GDBN} Command
17222 The corresponding @value{GDBN} CLI command(s), if any.
17224 @subsubheading Example
17226 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17227 @node GDB/MI Breakpoint Table Commands
17228 @section @sc{gdb/mi} Breakpoint table commands
17230 @cindex breakpoint commands for @sc{gdb/mi}
17231 @cindex @sc{gdb/mi}, breakpoint commands
17232 This section documents @sc{gdb/mi} commands for manipulating
17235 @subheading The @code{-break-after} Command
17236 @findex -break-after
17238 @subsubheading Synopsis
17241 -break-after @var{number} @var{count}
17244 The breakpoint number @var{number} is not in effect until it has been
17245 hit @var{count} times. To see how this is reflected in the output of
17246 the @samp{-break-list} command, see the description of the
17247 @samp{-break-list} command below.
17249 @subsubheading @value{GDBN} Command
17251 The corresponding @value{GDBN} command is @samp{ignore}.
17253 @subsubheading Example
17258 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",line="5"@}
17265 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17266 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17267 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17268 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17269 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17270 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17271 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17272 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17273 addr="0x000100d0",func="main",file="hello.c",line="5",times="0",
17279 @subheading The @code{-break-catch} Command
17280 @findex -break-catch
17282 @subheading The @code{-break-commands} Command
17283 @findex -break-commands
17287 @subheading The @code{-break-condition} Command
17288 @findex -break-condition
17290 @subsubheading Synopsis
17293 -break-condition @var{number} @var{expr}
17296 Breakpoint @var{number} will stop the program only if the condition in
17297 @var{expr} is true. The condition becomes part of the
17298 @samp{-break-list} output (see the description of the @samp{-break-list}
17301 @subsubheading @value{GDBN} Command
17303 The corresponding @value{GDBN} command is @samp{condition}.
17305 @subsubheading Example
17309 -break-condition 1 1
17313 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17314 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17315 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17316 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17317 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17318 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17319 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17320 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17321 addr="0x000100d0",func="main",file="hello.c",line="5",cond="1",
17322 times="0",ignore="3"@}]@}
17326 @subheading The @code{-break-delete} Command
17327 @findex -break-delete
17329 @subsubheading Synopsis
17332 -break-delete ( @var{breakpoint} )+
17335 Delete the breakpoint(s) whose number(s) are specified in the argument
17336 list. This is obviously reflected in the breakpoint list.
17338 @subsubheading @value{GDBN} command
17340 The corresponding @value{GDBN} command is @samp{delete}.
17342 @subsubheading Example
17350 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
17351 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17352 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17353 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17354 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17355 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17356 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17361 @subheading The @code{-break-disable} Command
17362 @findex -break-disable
17364 @subsubheading Synopsis
17367 -break-disable ( @var{breakpoint} )+
17370 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
17371 break list is now set to @samp{n} for the named @var{breakpoint}(s).
17373 @subsubheading @value{GDBN} Command
17375 The corresponding @value{GDBN} command is @samp{disable}.
17377 @subsubheading Example
17385 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17386 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17387 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17388 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17389 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17390 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17391 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17392 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
17393 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
17397 @subheading The @code{-break-enable} Command
17398 @findex -break-enable
17400 @subsubheading Synopsis
17403 -break-enable ( @var{breakpoint} )+
17406 Enable (previously disabled) @var{breakpoint}(s).
17408 @subsubheading @value{GDBN} Command
17410 The corresponding @value{GDBN} command is @samp{enable}.
17412 @subsubheading Example
17420 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17421 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17422 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17423 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17424 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17425 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17426 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17427 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
17428 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
17432 @subheading The @code{-break-info} Command
17433 @findex -break-info
17435 @subsubheading Synopsis
17438 -break-info @var{breakpoint}
17442 Get information about a single breakpoint.
17444 @subsubheading @value{GDBN} command
17446 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
17448 @subsubheading Example
17451 @subheading The @code{-break-insert} Command
17452 @findex -break-insert
17454 @subsubheading Synopsis
17457 -break-insert [ -t ] [ -h ] [ -r ]
17458 [ -c @var{condition} ] [ -i @var{ignore-count} ]
17459 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
17463 If specified, @var{line}, can be one of:
17470 @item filename:linenum
17471 @item filename:function
17475 The possible optional parameters of this command are:
17479 Insert a tempoary breakpoint.
17481 Insert a hardware breakpoint.
17482 @item -c @var{condition}
17483 Make the breakpoint conditional on @var{condition}.
17484 @item -i @var{ignore-count}
17485 Initialize the @var{ignore-count}.
17487 Insert a regular breakpoint in all the functions whose names match the
17488 given regular expression. Other flags are not applicable to regular
17492 @subsubheading Result
17494 The result is in the form:
17497 ^done,bkptno="@var{number}",func="@var{funcname}",
17498 file="@var{filename}",line="@var{lineno}"
17502 where @var{number} is the @value{GDBN} number for this breakpoint, @var{funcname}
17503 is the name of the function where the breakpoint was inserted,
17504 @var{filename} is the name of the source file which contains this
17505 function, and @var{lineno} is the source line number within that file.
17507 Note: this format is open to change.
17508 @c An out-of-band breakpoint instead of part of the result?
17510 @subsubheading @value{GDBN} Command
17512 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
17513 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
17515 @subsubheading Example
17520 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
17522 -break-insert -t foo
17523 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",line="11"@}
17526 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17527 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17528 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17529 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17530 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17531 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17532 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17533 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17534 addr="0x0001072c", func="main",file="recursive2.c",line="4",times="0"@},
17535 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
17536 addr="0x00010774",func="foo",file="recursive2.c",line="11",times="0"@}]@}
17538 -break-insert -r foo.*
17539 ~int foo(int, int);
17540 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c",line="11"@}
17544 @subheading The @code{-break-list} Command
17545 @findex -break-list
17547 @subsubheading Synopsis
17553 Displays the list of inserted breakpoints, showing the following fields:
17557 number of the breakpoint
17559 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
17561 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
17564 is the breakpoint enabled or no: @samp{y} or @samp{n}
17566 memory location at which the breakpoint is set
17568 logical location of the breakpoint, expressed by function name, file
17571 number of times the breakpoint has been hit
17574 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
17575 @code{body} field is an empty list.
17577 @subsubheading @value{GDBN} Command
17579 The corresponding @value{GDBN} command is @samp{info break}.
17581 @subsubheading Example
17586 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17587 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17588 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17589 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17590 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17591 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17592 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17593 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17594 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
17595 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
17596 addr="0x00010114",func="foo",file="hello.c",line="13",times="0"@}]@}
17600 Here's an example of the result when there are no breakpoints:
17605 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
17606 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17607 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17608 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17609 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17610 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17611 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17616 @subheading The @code{-break-watch} Command
17617 @findex -break-watch
17619 @subsubheading Synopsis
17622 -break-watch [ -a | -r ]
17625 Create a watchpoint. With the @samp{-a} option it will create an
17626 @dfn{access} watchpoint, i.e. a watchpoint that triggers either on a
17627 read from or on a write to the memory location. With the @samp{-r}
17628 option, the watchpoint created is a @dfn{read} watchpoint, i.e. it will
17629 trigger only when the memory location is accessed for reading. Without
17630 either of the options, the watchpoint created is a regular watchpoint,
17631 i.e. it will trigger when the memory location is accessed for writing.
17632 @xref{Set Watchpoints, , Setting watchpoints}.
17634 Note that @samp{-break-list} will report a single list of watchpoints and
17635 breakpoints inserted.
17637 @subsubheading @value{GDBN} Command
17639 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
17642 @subsubheading Example
17644 Setting a watchpoint on a variable in the @code{main} function:
17649 ^done,wpt=@{number="2",exp="x"@}
17653 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
17654 value=@{old="-268439212",new="55"@},
17655 frame=@{func="main",args=[],file="recursive2.c",
17656 fullname="/home/foo/bar/devo/myproject/recursive2.c",line="5"@}
17660 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
17661 the program execution twice: first for the variable changing value, then
17662 for the watchpoint going out of scope.
17667 ^done,wpt=@{number="5",exp="C"@}
17671 ^done,reason="watchpoint-trigger",
17672 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
17673 frame=@{func="callee4",args=[],
17674 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
17675 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
17679 ^done,reason="watchpoint-scope",wpnum="5",
17680 frame=@{func="callee3",args=[@{name="strarg",
17681 value="0x11940 \"A string argument.\""@}],
17682 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
17683 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
17687 Listing breakpoints and watchpoints, at different points in the program
17688 execution. Note that once the watchpoint goes out of scope, it is
17694 ^done,wpt=@{number="2",exp="C"@}
17697 ^done,BreakpointTable=@{nr_rows="2",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="1",type="breakpoint",disp="keep",enabled="y",
17705 addr="0x00010734",func="callee4",
17706 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
17707 bkpt=@{number="2",type="watchpoint",disp="keep",
17708 enabled="y",addr="",what="C",times="0"@}]@}
17712 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
17713 value=@{old="-276895068",new="3"@},
17714 frame=@{func="callee4",args=[],
17715 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
17716 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
17719 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17720 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17721 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17722 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17723 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17724 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17725 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17726 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17727 addr="0x00010734",func="callee4",
17728 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
17729 bkpt=@{number="2",type="watchpoint",disp="keep",
17730 enabled="y",addr="",what="C",times="-5"@}]@}
17734 ^done,reason="watchpoint-scope",wpnum="2",
17735 frame=@{func="callee3",args=[@{name="strarg",
17736 value="0x11940 \"A string argument.\""@}],
17737 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
17738 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
17741 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17742 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17743 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17744 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17745 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17746 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17747 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17748 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17749 addr="0x00010734",func="callee4",
17750 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@}]@}
17754 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17755 @node GDB/MI Data Manipulation
17756 @section @sc{gdb/mi} Data Manipulation
17758 @cindex data manipulation, in @sc{gdb/mi}
17759 @cindex @sc{gdb/mi}, data manipulation
17760 This section describes the @sc{gdb/mi} commands that manipulate data:
17761 examine memory and registers, evaluate expressions, etc.
17763 @c REMOVED FROM THE INTERFACE.
17764 @c @subheading -data-assign
17765 @c Change the value of a program variable. Plenty of side effects.
17766 @c @subsubheading GDB command
17768 @c @subsubheading Example
17771 @subheading The @code{-data-disassemble} Command
17772 @findex -data-disassemble
17774 @subsubheading Synopsis
17778 [ -s @var{start-addr} -e @var{end-addr} ]
17779 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
17787 @item @var{start-addr}
17788 is the beginning address (or @code{$pc})
17789 @item @var{end-addr}
17791 @item @var{filename}
17792 is the name of the file to disassemble
17793 @item @var{linenum}
17794 is the line number to disassemble around
17796 is the the number of disassembly lines to be produced. If it is -1,
17797 the whole function will be disassembled, in case no @var{end-addr} is
17798 specified. If @var{end-addr} is specified as a non-zero value, and
17799 @var{lines} is lower than the number of disassembly lines between
17800 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
17801 displayed; if @var{lines} is higher than the number of lines between
17802 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
17805 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
17809 @subsubheading Result
17811 The output for each instruction is composed of four fields:
17820 Note that whatever included in the instruction field, is not manipulated
17821 directely by @sc{gdb/mi}, i.e. it is not possible to adjust its format.
17823 @subsubheading @value{GDBN} Command
17825 There's no direct mapping from this command to the CLI.
17827 @subsubheading Example
17829 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
17833 -data-disassemble -s $pc -e "$pc + 20" -- 0
17836 @{address="0x000107c0",func-name="main",offset="4",
17837 inst="mov 2, %o0"@},
17838 @{address="0x000107c4",func-name="main",offset="8",
17839 inst="sethi %hi(0x11800), %o2"@},
17840 @{address="0x000107c8",func-name="main",offset="12",
17841 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
17842 @{address="0x000107cc",func-name="main",offset="16",
17843 inst="sethi %hi(0x11800), %o2"@},
17844 @{address="0x000107d0",func-name="main",offset="20",
17845 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
17849 Disassemble the whole @code{main} function. Line 32 is part of
17853 -data-disassemble -f basics.c -l 32 -- 0
17855 @{address="0x000107bc",func-name="main",offset="0",
17856 inst="save %sp, -112, %sp"@},
17857 @{address="0x000107c0",func-name="main",offset="4",
17858 inst="mov 2, %o0"@},
17859 @{address="0x000107c4",func-name="main",offset="8",
17860 inst="sethi %hi(0x11800), %o2"@},
17862 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
17863 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
17867 Disassemble 3 instructions from the start of @code{main}:
17871 -data-disassemble -f basics.c -l 32 -n 3 -- 0
17873 @{address="0x000107bc",func-name="main",offset="0",
17874 inst="save %sp, -112, %sp"@},
17875 @{address="0x000107c0",func-name="main",offset="4",
17876 inst="mov 2, %o0"@},
17877 @{address="0x000107c4",func-name="main",offset="8",
17878 inst="sethi %hi(0x11800), %o2"@}]
17882 Disassemble 3 instructions from the start of @code{main} in mixed mode:
17886 -data-disassemble -f basics.c -l 32 -n 3 -- 1
17888 src_and_asm_line=@{line="31",
17889 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
17890 testsuite/gdb.mi/basics.c",line_asm_insn=[
17891 @{address="0x000107bc",func-name="main",offset="0",
17892 inst="save %sp, -112, %sp"@}]@},
17893 src_and_asm_line=@{line="32",
17894 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
17895 testsuite/gdb.mi/basics.c",line_asm_insn=[
17896 @{address="0x000107c0",func-name="main",offset="4",
17897 inst="mov 2, %o0"@},
17898 @{address="0x000107c4",func-name="main",offset="8",
17899 inst="sethi %hi(0x11800), %o2"@}]@}]
17904 @subheading The @code{-data-evaluate-expression} Command
17905 @findex -data-evaluate-expression
17907 @subsubheading Synopsis
17910 -data-evaluate-expression @var{expr}
17913 Evaluate @var{expr} as an expression. The expression could contain an
17914 inferior function call. The function call will execute synchronously.
17915 If the expression contains spaces, it must be enclosed in double quotes.
17917 @subsubheading @value{GDBN} Command
17919 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
17920 @samp{call}. In @code{gdbtk} only, there's a corresponding
17921 @samp{gdb_eval} command.
17923 @subsubheading Example
17925 In the following example, the numbers that precede the commands are the
17926 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
17927 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
17931 211-data-evaluate-expression A
17934 311-data-evaluate-expression &A
17935 311^done,value="0xefffeb7c"
17937 411-data-evaluate-expression A+3
17940 511-data-evaluate-expression "A + 3"
17946 @subheading The @code{-data-list-changed-registers} Command
17947 @findex -data-list-changed-registers
17949 @subsubheading Synopsis
17952 -data-list-changed-registers
17955 Display a list of the registers that have changed.
17957 @subsubheading @value{GDBN} Command
17959 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
17960 has the corresponding command @samp{gdb_changed_register_list}.
17962 @subsubheading Example
17964 On a PPC MBX board:
17972 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
17973 args=[],file="try.c",fullname="/home/foo/bar/devo/myproject/try.c",line="5"@}
17975 -data-list-changed-registers
17976 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
17977 "10","11","13","14","15","16","17","18","19","20","21","22","23",
17978 "24","25","26","27","28","30","31","64","65","66","67","69"]
17983 @subheading The @code{-data-list-register-names} Command
17984 @findex -data-list-register-names
17986 @subsubheading Synopsis
17989 -data-list-register-names [ ( @var{regno} )+ ]
17992 Show a list of register names for the current target. If no arguments
17993 are given, it shows a list of the names of all the registers. If
17994 integer numbers are given as arguments, it will print a list of the
17995 names of the registers corresponding to the arguments. To ensure
17996 consistency between a register name and its number, the output list may
17997 include empty register names.
17999 @subsubheading @value{GDBN} Command
18001 @value{GDBN} does not have a command which corresponds to
18002 @samp{-data-list-register-names}. In @code{gdbtk} there is a
18003 corresponding command @samp{gdb_regnames}.
18005 @subsubheading Example
18007 For the PPC MBX board:
18010 -data-list-register-names
18011 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
18012 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
18013 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
18014 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
18015 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
18016 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
18017 "", "pc","ps","cr","lr","ctr","xer"]
18019 -data-list-register-names 1 2 3
18020 ^done,register-names=["r1","r2","r3"]
18024 @subheading The @code{-data-list-register-values} Command
18025 @findex -data-list-register-values
18027 @subsubheading Synopsis
18030 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
18033 Display the registers' contents. @var{fmt} is the format according to
18034 which the registers' contents are to be returned, followed by an optional
18035 list of numbers specifying the registers to display. A missing list of
18036 numbers indicates that the contents of all the registers must be returned.
18038 Allowed formats for @var{fmt} are:
18055 @subsubheading @value{GDBN} Command
18057 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
18058 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
18060 @subsubheading Example
18062 For a PPC MBX board (note: line breaks are for readability only, they
18063 don't appear in the actual output):
18067 -data-list-register-values r 64 65
18068 ^done,register-values=[@{number="64",value="0xfe00a300"@},
18069 @{number="65",value="0x00029002"@}]
18071 -data-list-register-values x
18072 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
18073 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
18074 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
18075 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
18076 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
18077 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
18078 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
18079 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
18080 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
18081 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
18082 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
18083 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
18084 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
18085 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
18086 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
18087 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
18088 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
18089 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
18090 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
18091 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
18092 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
18093 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
18094 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
18095 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
18096 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
18097 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
18098 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
18099 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
18100 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
18101 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
18102 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
18103 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
18104 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
18105 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
18106 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
18107 @{number="69",value="0x20002b03"@}]
18112 @subheading The @code{-data-read-memory} Command
18113 @findex -data-read-memory
18115 @subsubheading Synopsis
18118 -data-read-memory [ -o @var{byte-offset} ]
18119 @var{address} @var{word-format} @var{word-size}
18120 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
18127 @item @var{address}
18128 An expression specifying the address of the first memory word to be
18129 read. Complex expressions containing embedded white space should be
18130 quoted using the C convention.
18132 @item @var{word-format}
18133 The format to be used to print the memory words. The notation is the
18134 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
18137 @item @var{word-size}
18138 The size of each memory word in bytes.
18140 @item @var{nr-rows}
18141 The number of rows in the output table.
18143 @item @var{nr-cols}
18144 The number of columns in the output table.
18147 If present, indicates that each row should include an @sc{ascii} dump. The
18148 value of @var{aschar} is used as a padding character when a byte is not a
18149 member of the printable @sc{ascii} character set (printable @sc{ascii}
18150 characters are those whose code is between 32 and 126, inclusively).
18152 @item @var{byte-offset}
18153 An offset to add to the @var{address} before fetching memory.
18156 This command displays memory contents as a table of @var{nr-rows} by
18157 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
18158 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
18159 (returned as @samp{total-bytes}). Should less than the requested number
18160 of bytes be returned by the target, the missing words are identified
18161 using @samp{N/A}. The number of bytes read from the target is returned
18162 in @samp{nr-bytes} and the starting address used to read memory in
18165 The address of the next/previous row or page is available in
18166 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
18169 @subsubheading @value{GDBN} Command
18171 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
18172 @samp{gdb_get_mem} memory read command.
18174 @subsubheading Example
18176 Read six bytes of memory starting at @code{bytes+6} but then offset by
18177 @code{-6} bytes. Format as three rows of two columns. One byte per
18178 word. Display each word in hex.
18182 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
18183 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
18184 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
18185 prev-page="0x0000138a",memory=[
18186 @{addr="0x00001390",data=["0x00","0x01"]@},
18187 @{addr="0x00001392",data=["0x02","0x03"]@},
18188 @{addr="0x00001394",data=["0x04","0x05"]@}]
18192 Read two bytes of memory starting at address @code{shorts + 64} and
18193 display as a single word formatted in decimal.
18197 5-data-read-memory shorts+64 d 2 1 1
18198 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
18199 next-row="0x00001512",prev-row="0x0000150e",
18200 next-page="0x00001512",prev-page="0x0000150e",memory=[
18201 @{addr="0x00001510",data=["128"]@}]
18205 Read thirty two bytes of memory starting at @code{bytes+16} and format
18206 as eight rows of four columns. Include a string encoding with @samp{x}
18207 used as the non-printable character.
18211 4-data-read-memory bytes+16 x 1 8 4 x
18212 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
18213 next-row="0x000013c0",prev-row="0x0000139c",
18214 next-page="0x000013c0",prev-page="0x00001380",memory=[
18215 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
18216 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
18217 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
18218 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
18219 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
18220 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
18221 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
18222 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
18226 @subheading The @code{-display-delete} Command
18227 @findex -display-delete
18229 @subsubheading Synopsis
18232 -display-delete @var{number}
18235 Delete the display @var{number}.
18237 @subsubheading @value{GDBN} Command
18239 The corresponding @value{GDBN} command is @samp{delete display}.
18241 @subsubheading Example
18245 @subheading The @code{-display-disable} Command
18246 @findex -display-disable
18248 @subsubheading Synopsis
18251 -display-disable @var{number}
18254 Disable display @var{number}.
18256 @subsubheading @value{GDBN} Command
18258 The corresponding @value{GDBN} command is @samp{disable display}.
18260 @subsubheading Example
18264 @subheading The @code{-display-enable} Command
18265 @findex -display-enable
18267 @subsubheading Synopsis
18270 -display-enable @var{number}
18273 Enable display @var{number}.
18275 @subsubheading @value{GDBN} Command
18277 The corresponding @value{GDBN} command is @samp{enable display}.
18279 @subsubheading Example
18283 @subheading The @code{-display-insert} Command
18284 @findex -display-insert
18286 @subsubheading Synopsis
18289 -display-insert @var{expression}
18292 Display @var{expression} every time the program stops.
18294 @subsubheading @value{GDBN} Command
18296 The corresponding @value{GDBN} command is @samp{display}.
18298 @subsubheading Example
18302 @subheading The @code{-display-list} Command
18303 @findex -display-list
18305 @subsubheading Synopsis
18311 List the displays. Do not show the current values.
18313 @subsubheading @value{GDBN} Command
18315 The corresponding @value{GDBN} command is @samp{info display}.
18317 @subsubheading Example
18321 @subheading The @code{-environment-cd} Command
18322 @findex -environment-cd
18324 @subsubheading Synopsis
18327 -environment-cd @var{pathdir}
18330 Set @value{GDBN}'s working directory.
18332 @subsubheading @value{GDBN} Command
18334 The corresponding @value{GDBN} command is @samp{cd}.
18336 @subsubheading Example
18340 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18346 @subheading The @code{-environment-directory} Command
18347 @findex -environment-directory
18349 @subsubheading Synopsis
18352 -environment-directory [ -r ] [ @var{pathdir} ]+
18355 Add directories @var{pathdir} to beginning of search path for source files.
18356 If the @samp{-r} option is used, the search path is reset to the default
18357 search path. If directories @var{pathdir} are supplied in addition to the
18358 @samp{-r} option, the search path is first reset and then addition
18360 Multiple directories may be specified, separated by blanks. Specifying
18361 multiple directories in a single command
18362 results in the directories added to the beginning of the
18363 search path in the same order they were presented in the command.
18364 If blanks are needed as
18365 part of a directory name, double-quotes should be used around
18366 the name. In the command output, the path will show up separated
18367 by the system directory-separator character. The directory-seperator
18368 character must not be used
18369 in any directory name.
18370 If no directories are specified, the current search path is displayed.
18372 @subsubheading @value{GDBN} Command
18374 The corresponding @value{GDBN} command is @samp{dir}.
18376 @subsubheading Example
18380 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18381 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18383 -environment-directory ""
18384 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18386 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
18387 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
18389 -environment-directory -r
18390 ^done,source-path="$cdir:$cwd"
18395 @subheading The @code{-environment-path} Command
18396 @findex -environment-path
18398 @subsubheading Synopsis
18401 -environment-path [ -r ] [ @var{pathdir} ]+
18404 Add directories @var{pathdir} to beginning of search path for object files.
18405 If the @samp{-r} option is used, the search path is reset to the original
18406 search path that existed at gdb start-up. If directories @var{pathdir} are
18407 supplied in addition to the
18408 @samp{-r} option, the search path is first reset and then addition
18410 Multiple directories may be specified, separated by blanks. Specifying
18411 multiple directories in a single command
18412 results in the directories added to the beginning of the
18413 search path in the same order they were presented in the command.
18414 If blanks are needed as
18415 part of a directory name, double-quotes should be used around
18416 the name. In the command output, the path will show up separated
18417 by the system directory-separator character. The directory-seperator
18418 character must not be used
18419 in any directory name.
18420 If no directories are specified, the current path is displayed.
18423 @subsubheading @value{GDBN} Command
18425 The corresponding @value{GDBN} command is @samp{path}.
18427 @subsubheading Example
18432 ^done,path="/usr/bin"
18434 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
18435 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
18437 -environment-path -r /usr/local/bin
18438 ^done,path="/usr/local/bin:/usr/bin"
18443 @subheading The @code{-environment-pwd} Command
18444 @findex -environment-pwd
18446 @subsubheading Synopsis
18452 Show the current working directory.
18454 @subsubheading @value{GDBN} command
18456 The corresponding @value{GDBN} command is @samp{pwd}.
18458 @subsubheading Example
18463 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
18467 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18468 @node GDB/MI Program Control
18469 @section @sc{gdb/mi} Program control
18471 @subsubheading Program termination
18473 As a result of execution, the inferior program can run to completion, if
18474 it doesn't encounter any breakpoints. In this case the output will
18475 include an exit code, if the program has exited exceptionally.
18477 @subsubheading Examples
18480 Program exited normally:
18488 *stopped,reason="exited-normally"
18493 Program exited exceptionally:
18501 *stopped,reason="exited",exit-code="01"
18505 Another way the program can terminate is if it receives a signal such as
18506 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
18510 *stopped,reason="exited-signalled",signal-name="SIGINT",
18511 signal-meaning="Interrupt"
18515 @subheading The @code{-exec-abort} Command
18516 @findex -exec-abort
18518 @subsubheading Synopsis
18524 Kill the inferior running program.
18526 @subsubheading @value{GDBN} Command
18528 The corresponding @value{GDBN} command is @samp{kill}.
18530 @subsubheading Example
18534 @subheading The @code{-exec-arguments} Command
18535 @findex -exec-arguments
18537 @subsubheading Synopsis
18540 -exec-arguments @var{args}
18543 Set the inferior program arguments, to be used in the next
18546 @subsubheading @value{GDBN} Command
18548 The corresponding @value{GDBN} command is @samp{set args}.
18550 @subsubheading Example
18553 Don't have one around.
18556 @subheading The @code{-exec-continue} Command
18557 @findex -exec-continue
18559 @subsubheading Synopsis
18565 Asynchronous command. Resumes the execution of the inferior program
18566 until a breakpoint is encountered, or until the inferior exits.
18568 @subsubheading @value{GDBN} Command
18570 The corresponding @value{GDBN} corresponding is @samp{continue}.
18572 @subsubheading Example
18579 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
18580 file="hello.c",fullname="/home/foo/bar/devo/myproject/hello.c",line="13"@}
18585 @subheading The @code{-exec-finish} Command
18586 @findex -exec-finish
18588 @subsubheading Synopsis
18594 Asynchronous command. Resumes the execution of the inferior program
18595 until the current function is exited. Displays the results returned by
18598 @subsubheading @value{GDBN} Command
18600 The corresponding @value{GDBN} command is @samp{finish}.
18602 @subsubheading Example
18604 Function returning @code{void}.
18611 *stopped,reason="function-finished",frame=@{func="main",args=[],
18612 file="hello.c",fullname="/home/foo/bar/devo/myproject/hello.c",line="7"@}
18616 Function returning other than @code{void}. The name of the internal
18617 @value{GDBN} variable storing the result is printed, together with the
18624 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
18625 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
18626 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
18627 gdb-result-var="$1",return-value="0"
18632 @subheading The @code{-exec-interrupt} Command
18633 @findex -exec-interrupt
18635 @subsubheading Synopsis
18641 Asynchronous command. Interrupts the background execution of the target.
18642 Note how the token associated with the stop message is the one for the
18643 execution command that has been interrupted. The token for the interrupt
18644 itself only appears in the @samp{^done} output. If the user is trying to
18645 interrupt a non-running program, an error message will be printed.
18647 @subsubheading @value{GDBN} Command
18649 The corresponding @value{GDBN} command is @samp{interrupt}.
18651 @subsubheading Example
18662 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
18663 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
18664 fullname="/home/foo/bar/devo/myproject/try.c",line="13"@}
18669 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
18674 @subheading The @code{-exec-next} Command
18677 @subsubheading Synopsis
18683 Asynchronous command. Resumes execution of the inferior program, stopping
18684 when the beginning of the next source line is reached.
18686 @subsubheading @value{GDBN} Command
18688 The corresponding @value{GDBN} command is @samp{next}.
18690 @subsubheading Example
18696 *stopped,reason="end-stepping-range",line="8",file="hello.c"
18701 @subheading The @code{-exec-next-instruction} Command
18702 @findex -exec-next-instruction
18704 @subsubheading Synopsis
18707 -exec-next-instruction
18710 Asynchronous command. Executes one machine instruction. If the
18711 instruction is a function call continues until the function returns. If
18712 the program stops at an instruction in the middle of a source line, the
18713 address will be printed as well.
18715 @subsubheading @value{GDBN} Command
18717 The corresponding @value{GDBN} command is @samp{nexti}.
18719 @subsubheading Example
18723 -exec-next-instruction
18727 *stopped,reason="end-stepping-range",
18728 addr="0x000100d4",line="5",file="hello.c"
18733 @subheading The @code{-exec-return} Command
18734 @findex -exec-return
18736 @subsubheading Synopsis
18742 Makes current function return immediately. Doesn't execute the inferior.
18743 Displays the new current frame.
18745 @subsubheading @value{GDBN} Command
18747 The corresponding @value{GDBN} command is @samp{return}.
18749 @subsubheading Example
18753 200-break-insert callee4
18754 200^done,bkpt=@{number="1",addr="0x00010734",
18755 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18760 000*stopped,reason="breakpoint-hit",bkptno="1",
18761 frame=@{func="callee4",args=[],
18762 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18763 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18769 111^done,frame=@{level="0",func="callee3",
18770 args=[@{name="strarg",
18771 value="0x11940 \"A string argument.\""@}],
18772 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18773 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18778 @subheading The @code{-exec-run} Command
18781 @subsubheading Synopsis
18787 Asynchronous command. Starts execution of the inferior from the
18788 beginning. The inferior executes until either a breakpoint is
18789 encountered or the program exits.
18791 @subsubheading @value{GDBN} Command
18793 The corresponding @value{GDBN} command is @samp{run}.
18795 @subsubheading Example
18800 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
18805 *stopped,reason="breakpoint-hit",bkptno="1",
18806 frame=@{func="main",args=[],file="recursive2.c",
18807 fullname="/home/foo/bar/devo/myproject/recursive2.c",line="4"@}
18812 @subheading The @code{-exec-show-arguments} Command
18813 @findex -exec-show-arguments
18815 @subsubheading Synopsis
18818 -exec-show-arguments
18821 Print the arguments of the program.
18823 @subsubheading @value{GDBN} Command
18825 The corresponding @value{GDBN} command is @samp{show args}.
18827 @subsubheading Example
18830 @c @subheading -exec-signal
18832 @subheading The @code{-exec-step} Command
18835 @subsubheading Synopsis
18841 Asynchronous command. Resumes execution of the inferior program, stopping
18842 when the beginning of the next source line is reached, if the next
18843 source line is not a function call. If it is, stop at the first
18844 instruction of the called function.
18846 @subsubheading @value{GDBN} Command
18848 The corresponding @value{GDBN} command is @samp{step}.
18850 @subsubheading Example
18852 Stepping into a function:
18858 *stopped,reason="end-stepping-range",
18859 frame=@{func="foo",args=[@{name="a",value="10"@},
18860 @{name="b",value="0"@}],file="recursive2.c",
18861 fullname="/home/foo/bar/devo/myproject/recursive2.c",line="11"@}
18871 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
18876 @subheading The @code{-exec-step-instruction} Command
18877 @findex -exec-step-instruction
18879 @subsubheading Synopsis
18882 -exec-step-instruction
18885 Asynchronous command. Resumes the inferior which executes one machine
18886 instruction. The output, once @value{GDBN} has stopped, will vary depending on
18887 whether we have stopped in the middle of a source line or not. In the
18888 former case, the address at which the program stopped will be printed as
18891 @subsubheading @value{GDBN} Command
18893 The corresponding @value{GDBN} command is @samp{stepi}.
18895 @subsubheading Example
18899 -exec-step-instruction
18903 *stopped,reason="end-stepping-range",
18904 frame=@{func="foo",args=[],file="try.c",
18905 fullname="/home/foo/bar/devo/myproject/try.c",line="10"@}
18907 -exec-step-instruction
18911 *stopped,reason="end-stepping-range",
18912 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
18913 fullname="/home/foo/bar/devo/myproject/try.c",line="10"@}
18918 @subheading The @code{-exec-until} Command
18919 @findex -exec-until
18921 @subsubheading Synopsis
18924 -exec-until [ @var{location} ]
18927 Asynchronous command. Executes the inferior until the @var{location}
18928 specified in the argument is reached. If there is no argument, the inferior
18929 executes until a source line greater than the current one is reached.
18930 The reason for stopping in this case will be @samp{location-reached}.
18932 @subsubheading @value{GDBN} Command
18934 The corresponding @value{GDBN} command is @samp{until}.
18936 @subsubheading Example
18940 -exec-until recursive2.c:6
18944 *stopped,reason="location-reached",frame=@{func="main",args=[],
18945 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="6"@}
18950 @subheading -file-clear
18951 Is this going away????
18955 @subheading The @code{-file-exec-and-symbols} Command
18956 @findex -file-exec-and-symbols
18958 @subsubheading Synopsis
18961 -file-exec-and-symbols @var{file}
18964 Specify the executable file to be debugged. This file is the one from
18965 which the symbol table is also read. If no file is specified, the
18966 command clears the executable and symbol information. If breakpoints
18967 are set when using this command with no arguments, @value{GDBN} will produce
18968 error messages. Otherwise, no output is produced, except a completion
18971 @subsubheading @value{GDBN} Command
18973 The corresponding @value{GDBN} command is @samp{file}.
18975 @subsubheading Example
18979 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
18985 @subheading The @code{-file-exec-file} Command
18986 @findex -file-exec-file
18988 @subsubheading Synopsis
18991 -file-exec-file @var{file}
18994 Specify the executable file to be debugged. Unlike
18995 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
18996 from this file. If used without argument, @value{GDBN} clears the information
18997 about the executable file. No output is produced, except a completion
19000 @subsubheading @value{GDBN} Command
19002 The corresponding @value{GDBN} command is @samp{exec-file}.
19004 @subsubheading Example
19008 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
19014 @subheading The @code{-file-list-exec-sections} Command
19015 @findex -file-list-exec-sections
19017 @subsubheading Synopsis
19020 -file-list-exec-sections
19023 List the sections of the current executable file.
19025 @subsubheading @value{GDBN} Command
19027 The @value{GDBN} command @samp{info file} shows, among the rest, the same
19028 information as this command. @code{gdbtk} has a corresponding command
19029 @samp{gdb_load_info}.
19031 @subsubheading Example
19035 @subheading The @code{-file-list-exec-source-file} Command
19036 @findex -file-list-exec-source-file
19038 @subsubheading Synopsis
19041 -file-list-exec-source-file
19044 List the line number, the current source file, and the absolute path
19045 to the current source file for the current executable.
19047 @subsubheading @value{GDBN} Command
19049 There's no @value{GDBN} command which directly corresponds to this one.
19051 @subsubheading Example
19055 123-file-list-exec-source-file
19056 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
19061 @subheading The @code{-file-list-exec-source-files} Command
19062 @findex -file-list-exec-source-files
19064 @subsubheading Synopsis
19067 -file-list-exec-source-files
19070 List the source files for the current executable.
19072 It will always output the filename, but only when GDB can find the absolute
19073 file name of a source file, will it output the fullname.
19075 @subsubheading @value{GDBN} Command
19077 There's no @value{GDBN} command which directly corresponds to this one.
19078 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
19080 @subsubheading Example
19083 -file-list-exec-source-files
19085 @{file=foo.c,fullname=/home/foo.c@},
19086 @{file=/home/bar.c,fullname=/home/bar.c@},
19087 @{file=gdb_could_not_find_fullpath.c@}]
19091 @subheading The @code{-file-list-shared-libraries} Command
19092 @findex -file-list-shared-libraries
19094 @subsubheading Synopsis
19097 -file-list-shared-libraries
19100 List the shared libraries in the program.
19102 @subsubheading @value{GDBN} Command
19104 The corresponding @value{GDBN} command is @samp{info shared}.
19106 @subsubheading Example
19110 @subheading The @code{-file-list-symbol-files} Command
19111 @findex -file-list-symbol-files
19113 @subsubheading Synopsis
19116 -file-list-symbol-files
19121 @subsubheading @value{GDBN} Command
19123 The corresponding @value{GDBN} command is @samp{info file} (part of it).
19125 @subsubheading Example
19129 @subheading The @code{-file-symbol-file} Command
19130 @findex -file-symbol-file
19132 @subsubheading Synopsis
19135 -file-symbol-file @var{file}
19138 Read symbol table info from the specified @var{file} argument. When
19139 used without arguments, clears @value{GDBN}'s symbol table info. No output is
19140 produced, except for a completion notification.
19142 @subsubheading @value{GDBN} Command
19144 The corresponding @value{GDBN} command is @samp{symbol-file}.
19146 @subsubheading Example
19150 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
19155 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19156 @node GDB/MI Miscellaneous Commands
19157 @section Miscellaneous @value{GDBN} commands in @sc{gdb/mi}
19159 @c @subheading -gdb-complete
19161 @subheading The @code{-gdb-exit} Command
19164 @subsubheading Synopsis
19170 Exit @value{GDBN} immediately.
19172 @subsubheading @value{GDBN} Command
19174 Approximately corresponds to @samp{quit}.
19176 @subsubheading Example
19183 @subheading The @code{-gdb-set} Command
19186 @subsubheading Synopsis
19192 Set an internal @value{GDBN} variable.
19193 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
19195 @subsubheading @value{GDBN} Command
19197 The corresponding @value{GDBN} command is @samp{set}.
19199 @subsubheading Example
19209 @subheading The @code{-gdb-show} Command
19212 @subsubheading Synopsis
19218 Show the current value of a @value{GDBN} variable.
19220 @subsubheading @value{GDBN} command
19222 The corresponding @value{GDBN} command is @samp{show}.
19224 @subsubheading Example
19233 @c @subheading -gdb-source
19236 @subheading The @code{-gdb-version} Command
19237 @findex -gdb-version
19239 @subsubheading Synopsis
19245 Show version information for @value{GDBN}. Used mostly in testing.
19247 @subsubheading @value{GDBN} Command
19249 There's no equivalent @value{GDBN} command. @value{GDBN} by default shows this
19250 information when you start an interactive session.
19252 @subsubheading Example
19254 @c This example modifies the actual output from GDB to avoid overfull
19260 ~Copyright 2000 Free Software Foundation, Inc.
19261 ~GDB is free software, covered by the GNU General Public License, and
19262 ~you are welcome to change it and/or distribute copies of it under
19263 ~ certain conditions.
19264 ~Type "show copying" to see the conditions.
19265 ~There is absolutely no warranty for GDB. Type "show warranty" for
19267 ~This GDB was configured as
19268 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
19273 @subheading The @code{-interpreter-exec} Command
19274 @findex -interpreter-exec
19276 @subheading Synopsis
19279 -interpreter-exec @var{interpreter} @var{command}
19282 Execute the specified @var{command} in the given @var{interpreter}.
19284 @subheading @value{GDBN} Command
19286 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
19288 @subheading Example
19292 -interpreter-exec console "break main"
19293 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
19294 &"During symbol reading, bad structure-type format.\n"
19295 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
19300 @subheading The @code{-inferior-tty-set} Command
19301 @findex -inferior-tty-set
19303 @subheading Synopsis
19306 -inferior-tty-set /dev/pts/1
19309 Set terminal for future runs of the program being debugged.
19311 @subheading @value{GDBN} Command
19313 The corresponding @value{GDBN} command is @samp{set inferior-tty /dev/pts/1}.
19315 @subheading Example
19319 -inferior-tty-set /dev/pts/1
19324 @subheading The @code{-inferior-tty-show} Command
19325 @findex -inferior-tty-show
19327 @subheading Synopsis
19333 Show terminal for future runs of program being debugged.
19335 @subheading @value{GDBN} Command
19337 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
19339 @subheading Example
19343 -inferior-tty-set /dev/pts/1
19347 ^done,inferior_tty_terminal="/dev/pts/1"
19352 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19353 @node GDB/MI Kod Commands
19354 @section @sc{gdb/mi} Kod Commands
19356 The Kod commands are not implemented.
19358 @c @subheading -kod-info
19360 @c @subheading -kod-list
19362 @c @subheading -kod-list-object-types
19364 @c @subheading -kod-show
19366 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19367 @node GDB/MI Memory Overlay Commands
19368 @section @sc{gdb/mi} Memory Overlay Commands
19370 The memory overlay commands are not implemented.
19372 @c @subheading -overlay-auto
19374 @c @subheading -overlay-list-mapping-state
19376 @c @subheading -overlay-list-overlays
19378 @c @subheading -overlay-map
19380 @c @subheading -overlay-off
19382 @c @subheading -overlay-on
19384 @c @subheading -overlay-unmap
19386 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19387 @node GDB/MI Signal Handling Commands
19388 @section @sc{gdb/mi} Signal Handling Commands
19390 Signal handling commands are not implemented.
19392 @c @subheading -signal-handle
19394 @c @subheading -signal-list-handle-actions
19396 @c @subheading -signal-list-signal-types
19400 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19401 @node GDB/MI Stack Manipulation
19402 @section @sc{gdb/mi} Stack Manipulation Commands
19405 @subheading The @code{-stack-info-frame} Command
19406 @findex -stack-info-frame
19408 @subsubheading Synopsis
19414 Get info on the selected frame.
19416 @subsubheading @value{GDBN} Command
19418 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
19419 (without arguments).
19421 @subsubheading Example
19426 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
19427 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19428 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
19432 @subheading The @code{-stack-info-depth} Command
19433 @findex -stack-info-depth
19435 @subsubheading Synopsis
19438 -stack-info-depth [ @var{max-depth} ]
19441 Return the depth of the stack. If the integer argument @var{max-depth}
19442 is specified, do not count beyond @var{max-depth} frames.
19444 @subsubheading @value{GDBN} Command
19446 There's no equivalent @value{GDBN} command.
19448 @subsubheading Example
19450 For a stack with frame levels 0 through 11:
19457 -stack-info-depth 4
19460 -stack-info-depth 12
19463 -stack-info-depth 11
19466 -stack-info-depth 13
19471 @subheading The @code{-stack-list-arguments} Command
19472 @findex -stack-list-arguments
19474 @subsubheading Synopsis
19477 -stack-list-arguments @var{show-values}
19478 [ @var{low-frame} @var{high-frame} ]
19481 Display a list of the arguments for the frames between @var{low-frame}
19482 and @var{high-frame} (inclusive). If @var{low-frame} and
19483 @var{high-frame} are not provided, list the arguments for the whole call
19486 The @var{show-values} argument must have a value of 0 or 1. A value of
19487 0 means that only the names of the arguments are listed, a value of 1
19488 means that both names and values of the arguments are printed.
19490 @subsubheading @value{GDBN} Command
19492 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
19493 @samp{gdb_get_args} command which partially overlaps with the
19494 functionality of @samp{-stack-list-arguments}.
19496 @subsubheading Example
19503 frame=@{level="0",addr="0x00010734",func="callee4",
19504 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19505 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
19506 frame=@{level="1",addr="0x0001076c",func="callee3",
19507 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19508 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
19509 frame=@{level="2",addr="0x0001078c",func="callee2",
19510 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19511 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
19512 frame=@{level="3",addr="0x000107b4",func="callee1",
19513 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19514 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
19515 frame=@{level="4",addr="0x000107e0",func="main",
19516 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19517 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
19519 -stack-list-arguments 0
19522 frame=@{level="0",args=[]@},
19523 frame=@{level="1",args=[name="strarg"]@},
19524 frame=@{level="2",args=[name="intarg",name="strarg"]@},
19525 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
19526 frame=@{level="4",args=[]@}]
19528 -stack-list-arguments 1
19531 frame=@{level="0",args=[]@},
19533 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19534 frame=@{level="2",args=[
19535 @{name="intarg",value="2"@},
19536 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19537 @{frame=@{level="3",args=[
19538 @{name="intarg",value="2"@},
19539 @{name="strarg",value="0x11940 \"A string argument.\""@},
19540 @{name="fltarg",value="3.5"@}]@},
19541 frame=@{level="4",args=[]@}]
19543 -stack-list-arguments 0 2 2
19544 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
19546 -stack-list-arguments 1 2 2
19547 ^done,stack-args=[frame=@{level="2",
19548 args=[@{name="intarg",value="2"@},
19549 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
19553 @c @subheading -stack-list-exception-handlers
19556 @subheading The @code{-stack-list-frames} Command
19557 @findex -stack-list-frames
19559 @subsubheading Synopsis
19562 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
19565 List the frames currently on the stack. For each frame it displays the
19570 The frame number, 0 being the topmost frame, i.e. the innermost function.
19572 The @code{$pc} value for that frame.
19576 File name of the source file where the function lives.
19578 Line number corresponding to the @code{$pc}.
19581 If invoked without arguments, this command prints a backtrace for the
19582 whole stack. If given two integer arguments, it shows the frames whose
19583 levels are between the two arguments (inclusive). If the two arguments
19584 are equal, it shows the single frame at the corresponding level.
19586 @subsubheading @value{GDBN} Command
19588 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
19590 @subsubheading Example
19592 Full stack backtrace:
19598 [frame=@{level="0",addr="0x0001076c",func="foo",
19599 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="11"@},
19600 frame=@{level="1",addr="0x000107a4",func="foo",
19601 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19602 frame=@{level="2",addr="0x000107a4",func="foo",
19603 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19604 frame=@{level="3",addr="0x000107a4",func="foo",
19605 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19606 frame=@{level="4",addr="0x000107a4",func="foo",
19607 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19608 frame=@{level="5",addr="0x000107a4",func="foo",
19609 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19610 frame=@{level="6",addr="0x000107a4",func="foo",
19611 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19612 frame=@{level="7",addr="0x000107a4",func="foo",
19613 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19614 frame=@{level="8",addr="0x000107a4",func="foo",
19615 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19616 frame=@{level="9",addr="0x000107a4",func="foo",
19617 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19618 frame=@{level="10",addr="0x000107a4",func="foo",
19619 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19620 frame=@{level="11",addr="0x00010738",func="main",
19621 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="4"@}]
19625 Show frames between @var{low_frame} and @var{high_frame}:
19629 -stack-list-frames 3 5
19631 [frame=@{level="3",addr="0x000107a4",func="foo",
19632 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19633 frame=@{level="4",addr="0x000107a4",func="foo",
19634 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19635 frame=@{level="5",addr="0x000107a4",func="foo",
19636 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@}]
19640 Show a single frame:
19644 -stack-list-frames 3 3
19646 [frame=@{level="3",addr="0x000107a4",func="foo",
19647 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@}]
19652 @subheading The @code{-stack-list-locals} Command
19653 @findex -stack-list-locals
19655 @subsubheading Synopsis
19658 -stack-list-locals @var{print-values}
19661 Display the local variable names for the selected frame. If
19662 @var{print-values} is 0 or @code{--no-values}, print only the names of
19663 the variables; if it is 1 or @code{--all-values}, print also their
19664 values; and if it is 2 or @code{--simple-values}, print the name,
19665 type and value for simple data types and the name and type for arrays,
19666 structures and unions. In this last case, a frontend can immediately
19667 display the value of simple data types and create variable objects for
19668 other data types when the the user wishes to explore their values in
19671 @subsubheading @value{GDBN} Command
19673 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
19675 @subsubheading Example
19679 -stack-list-locals 0
19680 ^done,locals=[name="A",name="B",name="C"]
19682 -stack-list-locals --all-values
19683 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
19684 @{name="C",value="@{1, 2, 3@}"@}]
19685 -stack-list-locals --simple-values
19686 ^done,locals=[@{name="A",type="int",value="1"@},
19687 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
19692 @subheading The @code{-stack-select-frame} Command
19693 @findex -stack-select-frame
19695 @subsubheading Synopsis
19698 -stack-select-frame @var{framenum}
19701 Change the selected frame. Select a different frame @var{framenum} on
19704 @subsubheading @value{GDBN} Command
19706 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
19707 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
19709 @subsubheading Example
19713 -stack-select-frame 2
19718 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19719 @node GDB/MI Symbol Query
19720 @section @sc{gdb/mi} Symbol Query Commands
19723 @subheading The @code{-symbol-info-address} Command
19724 @findex -symbol-info-address
19726 @subsubheading Synopsis
19729 -symbol-info-address @var{symbol}
19732 Describe where @var{symbol} is stored.
19734 @subsubheading @value{GDBN} Command
19736 The corresponding @value{GDBN} command is @samp{info address}.
19738 @subsubheading Example
19742 @subheading The @code{-symbol-info-file} Command
19743 @findex -symbol-info-file
19745 @subsubheading Synopsis
19751 Show the file for the symbol.
19753 @subsubheading @value{GDBN} Command
19755 There's no equivalent @value{GDBN} command. @code{gdbtk} has
19756 @samp{gdb_find_file}.
19758 @subsubheading Example
19762 @subheading The @code{-symbol-info-function} Command
19763 @findex -symbol-info-function
19765 @subsubheading Synopsis
19768 -symbol-info-function
19771 Show which function the symbol lives in.
19773 @subsubheading @value{GDBN} Command
19775 @samp{gdb_get_function} in @code{gdbtk}.
19777 @subsubheading Example
19781 @subheading The @code{-symbol-info-line} Command
19782 @findex -symbol-info-line
19784 @subsubheading Synopsis
19790 Show the core addresses of the code for a source line.
19792 @subsubheading @value{GDBN} Command
19794 The corresponding @value{GDBN} command is @samp{info line}.
19795 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
19797 @subsubheading Example
19801 @subheading The @code{-symbol-info-symbol} Command
19802 @findex -symbol-info-symbol
19804 @subsubheading Synopsis
19807 -symbol-info-symbol @var{addr}
19810 Describe what symbol is at location @var{addr}.
19812 @subsubheading @value{GDBN} Command
19814 The corresponding @value{GDBN} command is @samp{info symbol}.
19816 @subsubheading Example
19820 @subheading The @code{-symbol-list-functions} Command
19821 @findex -symbol-list-functions
19823 @subsubheading Synopsis
19826 -symbol-list-functions
19829 List the functions in the executable.
19831 @subsubheading @value{GDBN} Command
19833 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
19834 @samp{gdb_search} in @code{gdbtk}.
19836 @subsubheading Example
19840 @subheading The @code{-symbol-list-lines} Command
19841 @findex -symbol-list-lines
19843 @subsubheading Synopsis
19846 -symbol-list-lines @var{filename}
19849 Print the list of lines that contain code and their associated program
19850 addresses for the given source filename. The entries are sorted in
19851 ascending PC order.
19853 @subsubheading @value{GDBN} Command
19855 There is no corresponding @value{GDBN} command.
19857 @subsubheading Example
19860 -symbol-list-lines basics.c
19861 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
19866 @subheading The @code{-symbol-list-types} Command
19867 @findex -symbol-list-types
19869 @subsubheading Synopsis
19875 List all the type names.
19877 @subsubheading @value{GDBN} Command
19879 The corresponding commands are @samp{info types} in @value{GDBN},
19880 @samp{gdb_search} in @code{gdbtk}.
19882 @subsubheading Example
19886 @subheading The @code{-symbol-list-variables} Command
19887 @findex -symbol-list-variables
19889 @subsubheading Synopsis
19892 -symbol-list-variables
19895 List all the global and static variable names.
19897 @subsubheading @value{GDBN} Command
19899 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
19901 @subsubheading Example
19905 @subheading The @code{-symbol-locate} Command
19906 @findex -symbol-locate
19908 @subsubheading Synopsis
19914 @subsubheading @value{GDBN} Command
19916 @samp{gdb_loc} in @code{gdbtk}.
19918 @subsubheading Example
19922 @subheading The @code{-symbol-type} Command
19923 @findex -symbol-type
19925 @subsubheading Synopsis
19928 -symbol-type @var{variable}
19931 Show type of @var{variable}.
19933 @subsubheading @value{GDBN} Command
19935 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
19936 @samp{gdb_obj_variable}.
19938 @subsubheading Example
19942 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19943 @node GDB/MI Target Manipulation
19944 @section @sc{gdb/mi} Target Manipulation Commands
19947 @subheading The @code{-target-attach} Command
19948 @findex -target-attach
19950 @subsubheading Synopsis
19953 -target-attach @var{pid} | @var{file}
19956 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
19958 @subsubheading @value{GDBN} command
19960 The corresponding @value{GDBN} command is @samp{attach}.
19962 @subsubheading Example
19966 @subheading The @code{-target-compare-sections} Command
19967 @findex -target-compare-sections
19969 @subsubheading Synopsis
19972 -target-compare-sections [ @var{section} ]
19975 Compare data of section @var{section} on target to the exec file.
19976 Without the argument, all sections are compared.
19978 @subsubheading @value{GDBN} Command
19980 The @value{GDBN} equivalent is @samp{compare-sections}.
19982 @subsubheading Example
19986 @subheading The @code{-target-detach} Command
19987 @findex -target-detach
19989 @subsubheading Synopsis
19995 Disconnect from the remote target. There's no output.
19997 @subsubheading @value{GDBN} command
19999 The corresponding @value{GDBN} command is @samp{detach}.
20001 @subsubheading Example
20011 @subheading The @code{-target-disconnect} Command
20012 @findex -target-disconnect
20014 @subsubheading Synopsis
20020 Disconnect from the remote target. There's no output.
20022 @subsubheading @value{GDBN} command
20024 The corresponding @value{GDBN} command is @samp{disconnect}.
20026 @subsubheading Example
20036 @subheading The @code{-target-download} Command
20037 @findex -target-download
20039 @subsubheading Synopsis
20045 Loads the executable onto the remote target.
20046 It prints out an update message every half second, which includes the fields:
20050 The name of the section.
20052 The size of what has been sent so far for that section.
20054 The size of the section.
20056 The total size of what was sent so far (the current and the previous sections).
20058 The size of the overall executable to download.
20062 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
20063 @sc{gdb/mi} Output Syntax}).
20065 In addition, it prints the name and size of the sections, as they are
20066 downloaded. These messages include the following fields:
20070 The name of the section.
20072 The size of the section.
20074 The size of the overall executable to download.
20078 At the end, a summary is printed.
20080 @subsubheading @value{GDBN} Command
20082 The corresponding @value{GDBN} command is @samp{load}.
20084 @subsubheading Example
20086 Note: each status message appears on a single line. Here the messages
20087 have been broken down so that they can fit onto a page.
20092 +download,@{section=".text",section-size="6668",total-size="9880"@}
20093 +download,@{section=".text",section-sent="512",section-size="6668",
20094 total-sent="512",total-size="9880"@}
20095 +download,@{section=".text",section-sent="1024",section-size="6668",
20096 total-sent="1024",total-size="9880"@}
20097 +download,@{section=".text",section-sent="1536",section-size="6668",
20098 total-sent="1536",total-size="9880"@}
20099 +download,@{section=".text",section-sent="2048",section-size="6668",
20100 total-sent="2048",total-size="9880"@}
20101 +download,@{section=".text",section-sent="2560",section-size="6668",
20102 total-sent="2560",total-size="9880"@}
20103 +download,@{section=".text",section-sent="3072",section-size="6668",
20104 total-sent="3072",total-size="9880"@}
20105 +download,@{section=".text",section-sent="3584",section-size="6668",
20106 total-sent="3584",total-size="9880"@}
20107 +download,@{section=".text",section-sent="4096",section-size="6668",
20108 total-sent="4096",total-size="9880"@}
20109 +download,@{section=".text",section-sent="4608",section-size="6668",
20110 total-sent="4608",total-size="9880"@}
20111 +download,@{section=".text",section-sent="5120",section-size="6668",
20112 total-sent="5120",total-size="9880"@}
20113 +download,@{section=".text",section-sent="5632",section-size="6668",
20114 total-sent="5632",total-size="9880"@}
20115 +download,@{section=".text",section-sent="6144",section-size="6668",
20116 total-sent="6144",total-size="9880"@}
20117 +download,@{section=".text",section-sent="6656",section-size="6668",
20118 total-sent="6656",total-size="9880"@}
20119 +download,@{section=".init",section-size="28",total-size="9880"@}
20120 +download,@{section=".fini",section-size="28",total-size="9880"@}
20121 +download,@{section=".data",section-size="3156",total-size="9880"@}
20122 +download,@{section=".data",section-sent="512",section-size="3156",
20123 total-sent="7236",total-size="9880"@}
20124 +download,@{section=".data",section-sent="1024",section-size="3156",
20125 total-sent="7748",total-size="9880"@}
20126 +download,@{section=".data",section-sent="1536",section-size="3156",
20127 total-sent="8260",total-size="9880"@}
20128 +download,@{section=".data",section-sent="2048",section-size="3156",
20129 total-sent="8772",total-size="9880"@}
20130 +download,@{section=".data",section-sent="2560",section-size="3156",
20131 total-sent="9284",total-size="9880"@}
20132 +download,@{section=".data",section-sent="3072",section-size="3156",
20133 total-sent="9796",total-size="9880"@}
20134 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
20140 @subheading The @code{-target-exec-status} Command
20141 @findex -target-exec-status
20143 @subsubheading Synopsis
20146 -target-exec-status
20149 Provide information on the state of the target (whether it is running or
20150 not, for instance).
20152 @subsubheading @value{GDBN} Command
20154 There's no equivalent @value{GDBN} command.
20156 @subsubheading Example
20160 @subheading The @code{-target-list-available-targets} Command
20161 @findex -target-list-available-targets
20163 @subsubheading Synopsis
20166 -target-list-available-targets
20169 List the possible targets to connect to.
20171 @subsubheading @value{GDBN} Command
20173 The corresponding @value{GDBN} command is @samp{help target}.
20175 @subsubheading Example
20179 @subheading The @code{-target-list-current-targets} Command
20180 @findex -target-list-current-targets
20182 @subsubheading Synopsis
20185 -target-list-current-targets
20188 Describe the current target.
20190 @subsubheading @value{GDBN} Command
20192 The corresponding information is printed by @samp{info file} (among
20195 @subsubheading Example
20199 @subheading The @code{-target-list-parameters} Command
20200 @findex -target-list-parameters
20202 @subsubheading Synopsis
20205 -target-list-parameters
20210 @subsubheading @value{GDBN} Command
20214 @subsubheading Example
20218 @subheading The @code{-target-select} Command
20219 @findex -target-select
20221 @subsubheading Synopsis
20224 -target-select @var{type} @var{parameters @dots{}}
20227 Connect @value{GDBN} to the remote target. This command takes two args:
20231 The type of target, for instance @samp{async}, @samp{remote}, etc.
20232 @item @var{parameters}
20233 Device names, host names and the like. @xref{Target Commands, ,
20234 Commands for managing targets}, for more details.
20237 The output is a connection notification, followed by the address at
20238 which the target program is, in the following form:
20241 ^connected,addr="@var{address}",func="@var{function name}",
20242 args=[@var{arg list}]
20245 @subsubheading @value{GDBN} Command
20247 The corresponding @value{GDBN} command is @samp{target}.
20249 @subsubheading Example
20253 -target-select async /dev/ttya
20254 ^connected,addr="0xfe00a300",func="??",args=[]
20258 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20259 @node GDB/MI Thread Commands
20260 @section @sc{gdb/mi} Thread Commands
20263 @subheading The @code{-thread-info} Command
20264 @findex -thread-info
20266 @subsubheading Synopsis
20272 @subsubheading @value{GDBN} command
20276 @subsubheading Example
20280 @subheading The @code{-thread-list-all-threads} Command
20281 @findex -thread-list-all-threads
20283 @subsubheading Synopsis
20286 -thread-list-all-threads
20289 @subsubheading @value{GDBN} Command
20291 The equivalent @value{GDBN} command is @samp{info threads}.
20293 @subsubheading Example
20297 @subheading The @code{-thread-list-ids} Command
20298 @findex -thread-list-ids
20300 @subsubheading Synopsis
20306 Produces a list of the currently known @value{GDBN} thread ids. At the
20307 end of the list it also prints the total number of such threads.
20309 @subsubheading @value{GDBN} Command
20311 Part of @samp{info threads} supplies the same information.
20313 @subsubheading Example
20315 No threads present, besides the main process:
20320 ^done,thread-ids=@{@},number-of-threads="0"
20330 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20331 number-of-threads="3"
20336 @subheading The @code{-thread-select} Command
20337 @findex -thread-select
20339 @subsubheading Synopsis
20342 -thread-select @var{threadnum}
20345 Make @var{threadnum} the current thread. It prints the number of the new
20346 current thread, and the topmost frame for that thread.
20348 @subsubheading @value{GDBN} Command
20350 The corresponding @value{GDBN} command is @samp{thread}.
20352 @subsubheading Example
20359 *stopped,reason="end-stepping-range",thread-id="2",line="187",
20360 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
20364 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20365 number-of-threads="3"
20368 ^done,new-thread-id="3",
20369 frame=@{level="0",func="vprintf",
20370 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
20371 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
20375 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20376 @node GDB/MI Tracepoint Commands
20377 @section @sc{gdb/mi} Tracepoint Commands
20379 The tracepoint commands are not yet implemented.
20381 @c @subheading -trace-actions
20383 @c @subheading -trace-delete
20385 @c @subheading -trace-disable
20387 @c @subheading -trace-dump
20389 @c @subheading -trace-enable
20391 @c @subheading -trace-exists
20393 @c @subheading -trace-find
20395 @c @subheading -trace-frame-number
20397 @c @subheading -trace-info
20399 @c @subheading -trace-insert
20401 @c @subheading -trace-list
20403 @c @subheading -trace-pass-count
20405 @c @subheading -trace-save
20407 @c @subheading -trace-start
20409 @c @subheading -trace-stop
20412 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20413 @node GDB/MI Variable Objects
20414 @section @sc{gdb/mi} Variable Objects
20417 @subheading Motivation for Variable Objects in @sc{gdb/mi}
20419 For the implementation of a variable debugger window (locals, watched
20420 expressions, etc.), we are proposing the adaptation of the existing code
20421 used by @code{Insight}.
20423 The two main reasons for that are:
20427 It has been proven in practice (it is already on its second generation).
20430 It will shorten development time (needless to say how important it is
20434 The original interface was designed to be used by Tcl code, so it was
20435 slightly changed so it could be used through @sc{gdb/mi}. This section
20436 describes the @sc{gdb/mi} operations that will be available and gives some
20437 hints about their use.
20439 @emph{Note}: In addition to the set of operations described here, we
20440 expect the @sc{gui} implementation of a variable window to require, at
20441 least, the following operations:
20444 @item @code{-gdb-show} @code{output-radix}
20445 @item @code{-stack-list-arguments}
20446 @item @code{-stack-list-locals}
20447 @item @code{-stack-select-frame}
20450 @subheading Introduction to Variable Objects in @sc{gdb/mi}
20452 @cindex variable objects in @sc{gdb/mi}
20453 The basic idea behind variable objects is the creation of a named object
20454 to represent a variable, an expression, a memory location or even a CPU
20455 register. For each object created, a set of operations is available for
20456 examining or changing its properties.
20458 Furthermore, complex data types, such as C structures, are represented
20459 in a tree format. For instance, the @code{struct} type variable is the
20460 root and the children will represent the struct members. If a child
20461 is itself of a complex type, it will also have children of its own.
20462 Appropriate language differences are handled for C, C@t{++} and Java.
20464 When returning the actual values of the objects, this facility allows
20465 for the individual selection of the display format used in the result
20466 creation. It can be chosen among: binary, decimal, hexadecimal, octal
20467 and natural. Natural refers to a default format automatically
20468 chosen based on the variable type (like decimal for an @code{int}, hex
20469 for pointers, etc.).
20471 The following is the complete set of @sc{gdb/mi} operations defined to
20472 access this functionality:
20474 @multitable @columnfractions .4 .6
20475 @item @strong{Operation}
20476 @tab @strong{Description}
20478 @item @code{-var-create}
20479 @tab create a variable object
20480 @item @code{-var-delete}
20481 @tab delete the variable object and its children
20482 @item @code{-var-set-format}
20483 @tab set the display format of this variable
20484 @item @code{-var-show-format}
20485 @tab show the display format of this variable
20486 @item @code{-var-info-num-children}
20487 @tab tells how many children this object has
20488 @item @code{-var-list-children}
20489 @tab return a list of the object's children
20490 @item @code{-var-info-type}
20491 @tab show the type of this variable object
20492 @item @code{-var-info-expression}
20493 @tab print what this variable object represents
20494 @item @code{-var-show-attributes}
20495 @tab is this variable editable? does it exist here?
20496 @item @code{-var-evaluate-expression}
20497 @tab get the value of this variable
20498 @item @code{-var-assign}
20499 @tab set the value of this variable
20500 @item @code{-var-update}
20501 @tab update the variable and its children
20504 In the next subsection we describe each operation in detail and suggest
20505 how it can be used.
20507 @subheading Description And Use of Operations on Variable Objects
20509 @subheading The @code{-var-create} Command
20510 @findex -var-create
20512 @subsubheading Synopsis
20515 -var-create @{@var{name} | "-"@}
20516 @{@var{frame-addr} | "*"@} @var{expression}
20519 This operation creates a variable object, which allows the monitoring of
20520 a variable, the result of an expression, a memory cell or a CPU
20523 The @var{name} parameter is the string by which the object can be
20524 referenced. It must be unique. If @samp{-} is specified, the varobj
20525 system will generate a string ``varNNNNNN'' automatically. It will be
20526 unique provided that one does not specify @var{name} on that format.
20527 The command fails if a duplicate name is found.
20529 The frame under which the expression should be evaluated can be
20530 specified by @var{frame-addr}. A @samp{*} indicates that the current
20531 frame should be used.
20533 @var{expression} is any expression valid on the current language set (must not
20534 begin with a @samp{*}), or one of the following:
20538 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
20541 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
20544 @samp{$@var{regname}} --- a CPU register name
20547 @subsubheading Result
20549 This operation returns the name, number of children and the type of the
20550 object created. Type is returned as a string as the ones generated by
20551 the @value{GDBN} CLI:
20554 name="@var{name}",numchild="N",type="@var{type}"
20558 @subheading The @code{-var-delete} Command
20559 @findex -var-delete
20561 @subsubheading Synopsis
20564 -var-delete @var{name}
20567 Deletes a previously created variable object and all of its children.
20569 Returns an error if the object @var{name} is not found.
20572 @subheading The @code{-var-set-format} Command
20573 @findex -var-set-format
20575 @subsubheading Synopsis
20578 -var-set-format @var{name} @var{format-spec}
20581 Sets the output format for the value of the object @var{name} to be
20584 The syntax for the @var{format-spec} is as follows:
20587 @var{format-spec} @expansion{}
20588 @{binary | decimal | hexadecimal | octal | natural@}
20592 @subheading The @code{-var-show-format} Command
20593 @findex -var-show-format
20595 @subsubheading Synopsis
20598 -var-show-format @var{name}
20601 Returns the format used to display the value of the object @var{name}.
20604 @var{format} @expansion{}
20609 @subheading The @code{-var-info-num-children} Command
20610 @findex -var-info-num-children
20612 @subsubheading Synopsis
20615 -var-info-num-children @var{name}
20618 Returns the number of children of a variable object @var{name}:
20625 @subheading The @code{-var-list-children} Command
20626 @findex -var-list-children
20628 @subsubheading Synopsis
20631 -var-list-children [@var{print-values}] @var{name}
20633 @anchor{-var-list-children}
20635 Return a list of the children of the specified variable object and
20636 create variable objects for them, if they do not already exist. With
20637 a single argument or if @var{print-values} has a value for of 0 or
20638 @code{--no-values}, print only the names of the variables; if
20639 @var{print-values} is 1 or @code{--all-values}, also print their
20640 values; and if it is 2 or @code{--simple-values} print the name and
20641 value for simple data types and just the name for arrays, structures
20644 @subsubheading Example
20648 -var-list-children n
20649 ^done,numchild=@var{n},children=[@{name=@var{name},
20650 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
20652 -var-list-children --all-values n
20653 ^done,numchild=@var{n},children=[@{name=@var{name},
20654 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
20658 @subheading The @code{-var-info-type} Command
20659 @findex -var-info-type
20661 @subsubheading Synopsis
20664 -var-info-type @var{name}
20667 Returns the type of the specified variable @var{name}. The type is
20668 returned as a string in the same format as it is output by the
20672 type=@var{typename}
20676 @subheading The @code{-var-info-expression} Command
20677 @findex -var-info-expression
20679 @subsubheading Synopsis
20682 -var-info-expression @var{name}
20685 Returns what is represented by the variable object @var{name}:
20688 lang=@var{lang-spec},exp=@var{expression}
20692 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
20694 @subheading The @code{-var-show-attributes} Command
20695 @findex -var-show-attributes
20697 @subsubheading Synopsis
20700 -var-show-attributes @var{name}
20703 List attributes of the specified variable object @var{name}:
20706 status=@var{attr} [ ( ,@var{attr} )* ]
20710 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
20712 @subheading The @code{-var-evaluate-expression} Command
20713 @findex -var-evaluate-expression
20715 @subsubheading Synopsis
20718 -var-evaluate-expression @var{name}
20721 Evaluates the expression that is represented by the specified variable
20722 object and returns its value as a string in the current format specified
20729 Note that one must invoke @code{-var-list-children} for a variable
20730 before the value of a child variable can be evaluated.
20732 @subheading The @code{-var-assign} Command
20733 @findex -var-assign
20735 @subsubheading Synopsis
20738 -var-assign @var{name} @var{expression}
20741 Assigns the value of @var{expression} to the variable object specified
20742 by @var{name}. The object must be @samp{editable}. If the variable's
20743 value is altered by the assign, the variable will show up in any
20744 subsequent @code{-var-update} list.
20746 @subsubheading Example
20754 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
20758 @subheading The @code{-var-update} Command
20759 @findex -var-update
20761 @subsubheading Synopsis
20764 -var-update [@var{print-values}] @{@var{name} | "*"@}
20767 Update the value of the variable object @var{name} by evaluating its
20768 expression after fetching all the new values from memory or registers.
20769 A @samp{*} causes all existing variable objects to be updated. The
20770 option @var{print-values} determines whether names both and values, or
20771 just names are printed in the manner described for
20772 @code{-var-list-children} (@pxref{-var-list-children}).
20774 @subsubheading Example
20781 -var-update --all-values var1
20782 ^done,changelist=[@{name="var1",value="3",in_scope="true",
20783 type_changed="false"@}]
20788 @chapter @value{GDBN} Annotations
20790 This chapter describes annotations in @value{GDBN}. Annotations were
20791 designed to interface @value{GDBN} to graphical user interfaces or other
20792 similar programs which want to interact with @value{GDBN} at a
20793 relatively high level.
20795 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
20799 This is Edition @value{EDITION}, @value{DATE}.
20803 * Annotations Overview:: What annotations are; the general syntax.
20804 * Prompting:: Annotations marking @value{GDBN}'s need for input.
20805 * Errors:: Annotations for error messages.
20806 * Invalidation:: Some annotations describe things now invalid.
20807 * Annotations for Running::
20808 Whether the program is running, how it stopped, etc.
20809 * Source Annotations:: Annotations describing source code.
20812 @node Annotations Overview
20813 @section What is an Annotation?
20814 @cindex annotations
20816 Annotations start with a newline character, two @samp{control-z}
20817 characters, and the name of the annotation. If there is no additional
20818 information associated with this annotation, the name of the annotation
20819 is followed immediately by a newline. If there is additional
20820 information, the name of the annotation is followed by a space, the
20821 additional information, and a newline. The additional information
20822 cannot contain newline characters.
20824 Any output not beginning with a newline and two @samp{control-z}
20825 characters denotes literal output from @value{GDBN}. Currently there is
20826 no need for @value{GDBN} to output a newline followed by two
20827 @samp{control-z} characters, but if there was such a need, the
20828 annotations could be extended with an @samp{escape} annotation which
20829 means those three characters as output.
20831 The annotation @var{level}, which is specified using the
20832 @option{--annotate} command line option (@pxref{Mode Options}), controls
20833 how much information @value{GDBN} prints together with its prompt,
20834 values of expressions, source lines, and other types of output. Level 0
20835 is for no anntations, level 1 is for use when @value{GDBN} is run as a
20836 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
20837 for programs that control @value{GDBN}, and level 2 annotations have
20838 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
20839 Interface, annotate, GDB's Obsolete Annotations}).
20842 @kindex set annotate
20843 @item set annotate @var{level}
20844 The @value{GDBN} command @code{set annotate} sets the level of
20845 annotations to the specified @var{level}.
20847 @item show annotate
20848 @kindex show annotate
20849 Show the current annotation level.
20852 This chapter describes level 3 annotations.
20854 A simple example of starting up @value{GDBN} with annotations is:
20857 $ @kbd{gdb --annotate=3}
20859 Copyright 2003 Free Software Foundation, Inc.
20860 GDB is free software, covered by the GNU General Public License,
20861 and you are welcome to change it and/or distribute copies of it
20862 under certain conditions.
20863 Type "show copying" to see the conditions.
20864 There is absolutely no warranty for GDB. Type "show warranty"
20866 This GDB was configured as "i386-pc-linux-gnu"
20877 Here @samp{quit} is input to @value{GDBN}; the rest is output from
20878 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
20879 denotes a @samp{control-z} character) are annotations; the rest is
20880 output from @value{GDBN}.
20883 @section Annotation for @value{GDBN} Input
20885 @cindex annotations for prompts
20886 When @value{GDBN} prompts for input, it annotates this fact so it is possible
20887 to know when to send output, when the output from a given command is
20890 Different kinds of input each have a different @dfn{input type}. Each
20891 input type has three annotations: a @code{pre-} annotation, which
20892 denotes the beginning of any prompt which is being output, a plain
20893 annotation, which denotes the end of the prompt, and then a @code{post-}
20894 annotation which denotes the end of any echo which may (or may not) be
20895 associated with the input. For example, the @code{prompt} input type
20896 features the following annotations:
20904 The input types are
20909 @findex post-prompt
20911 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
20913 @findex pre-commands
20915 @findex post-commands
20917 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
20918 command. The annotations are repeated for each command which is input.
20920 @findex pre-overload-choice
20921 @findex overload-choice
20922 @findex post-overload-choice
20923 @item overload-choice
20924 When @value{GDBN} wants the user to select between various overloaded functions.
20930 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
20932 @findex pre-prompt-for-continue
20933 @findex prompt-for-continue
20934 @findex post-prompt-for-continue
20935 @item prompt-for-continue
20936 When @value{GDBN} is asking the user to press return to continue. Note: Don't
20937 expect this to work well; instead use @code{set height 0} to disable
20938 prompting. This is because the counting of lines is buggy in the
20939 presence of annotations.
20944 @cindex annotations for errors, warnings and interrupts
20951 This annotation occurs right before @value{GDBN} responds to an interrupt.
20958 This annotation occurs right before @value{GDBN} responds to an error.
20960 Quit and error annotations indicate that any annotations which @value{GDBN} was
20961 in the middle of may end abruptly. For example, if a
20962 @code{value-history-begin} annotation is followed by a @code{error}, one
20963 cannot expect to receive the matching @code{value-history-end}. One
20964 cannot expect not to receive it either, however; an error annotation
20965 does not necessarily mean that @value{GDBN} is immediately returning all the way
20968 @findex error-begin
20969 A quit or error annotation may be preceded by
20975 Any output between that and the quit or error annotation is the error
20978 Warning messages are not yet annotated.
20979 @c If we want to change that, need to fix warning(), type_error(),
20980 @c range_error(), and possibly other places.
20983 @section Invalidation Notices
20985 @cindex annotations for invalidation messages
20986 The following annotations say that certain pieces of state may have
20990 @findex frames-invalid
20991 @item ^Z^Zframes-invalid
20993 The frames (for example, output from the @code{backtrace} command) may
20996 @findex breakpoints-invalid
20997 @item ^Z^Zbreakpoints-invalid
20999 The breakpoints may have changed. For example, the user just added or
21000 deleted a breakpoint.
21003 @node Annotations for Running
21004 @section Running the Program
21005 @cindex annotations for running programs
21009 When the program starts executing due to a @value{GDBN} command such as
21010 @code{step} or @code{continue},
21016 is output. When the program stops,
21022 is output. Before the @code{stopped} annotation, a variety of
21023 annotations describe how the program stopped.
21027 @item ^Z^Zexited @var{exit-status}
21028 The program exited, and @var{exit-status} is the exit status (zero for
21029 successful exit, otherwise nonzero).
21032 @findex signal-name
21033 @findex signal-name-end
21034 @findex signal-string
21035 @findex signal-string-end
21036 @item ^Z^Zsignalled
21037 The program exited with a signal. After the @code{^Z^Zsignalled}, the
21038 annotation continues:
21044 ^Z^Zsignal-name-end
21048 ^Z^Zsignal-string-end
21053 where @var{name} is the name of the signal, such as @code{SIGILL} or
21054 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
21055 as @code{Illegal Instruction} or @code{Segmentation fault}.
21056 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
21057 user's benefit and have no particular format.
21061 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
21062 just saying that the program received the signal, not that it was
21063 terminated with it.
21066 @item ^Z^Zbreakpoint @var{number}
21067 The program hit breakpoint number @var{number}.
21070 @item ^Z^Zwatchpoint @var{number}
21071 The program hit watchpoint number @var{number}.
21074 @node Source Annotations
21075 @section Displaying Source
21076 @cindex annotations for source display
21079 The following annotation is used instead of displaying source code:
21082 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
21085 where @var{filename} is an absolute file name indicating which source
21086 file, @var{line} is the line number within that file (where 1 is the
21087 first line in the file), @var{character} is the character position
21088 within the file (where 0 is the first character in the file) (for most
21089 debug formats this will necessarily point to the beginning of a line),
21090 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
21091 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
21092 @var{addr} is the address in the target program associated with the
21093 source which is being displayed. @var{addr} is in the form @samp{0x}
21094 followed by one or more lowercase hex digits (note that this does not
21095 depend on the language).
21098 @chapter Reporting Bugs in @value{GDBN}
21099 @cindex bugs in @value{GDBN}
21100 @cindex reporting bugs in @value{GDBN}
21102 Your bug reports play an essential role in making @value{GDBN} reliable.
21104 Reporting a bug may help you by bringing a solution to your problem, or it
21105 may not. But in any case the principal function of a bug report is to help
21106 the entire community by making the next version of @value{GDBN} work better. Bug
21107 reports are your contribution to the maintenance of @value{GDBN}.
21109 In order for a bug report to serve its purpose, you must include the
21110 information that enables us to fix the bug.
21113 * Bug Criteria:: Have you found a bug?
21114 * Bug Reporting:: How to report bugs
21118 @section Have you found a bug?
21119 @cindex bug criteria
21121 If you are not sure whether you have found a bug, here are some guidelines:
21124 @cindex fatal signal
21125 @cindex debugger crash
21126 @cindex crash of debugger
21128 If the debugger gets a fatal signal, for any input whatever, that is a
21129 @value{GDBN} bug. Reliable debuggers never crash.
21131 @cindex error on valid input
21133 If @value{GDBN} produces an error message for valid input, that is a
21134 bug. (Note that if you're cross debugging, the problem may also be
21135 somewhere in the connection to the target.)
21137 @cindex invalid input
21139 If @value{GDBN} does not produce an error message for invalid input,
21140 that is a bug. However, you should note that your idea of
21141 ``invalid input'' might be our idea of ``an extension'' or ``support
21142 for traditional practice''.
21145 If you are an experienced user of debugging tools, your suggestions
21146 for improvement of @value{GDBN} are welcome in any case.
21149 @node Bug Reporting
21150 @section How to report bugs
21151 @cindex bug reports
21152 @cindex @value{GDBN} bugs, reporting
21154 A number of companies and individuals offer support for @sc{gnu} products.
21155 If you obtained @value{GDBN} from a support organization, we recommend you
21156 contact that organization first.
21158 You can find contact information for many support companies and
21159 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
21161 @c should add a web page ref...
21163 In any event, we also recommend that you submit bug reports for
21164 @value{GDBN}. The prefered method is to submit them directly using
21165 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
21166 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
21169 @strong{Do not send bug reports to @samp{info-gdb}, or to
21170 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
21171 not want to receive bug reports. Those that do have arranged to receive
21174 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
21175 serves as a repeater. The mailing list and the newsgroup carry exactly
21176 the same messages. Often people think of posting bug reports to the
21177 newsgroup instead of mailing them. This appears to work, but it has one
21178 problem which can be crucial: a newsgroup posting often lacks a mail
21179 path back to the sender. Thus, if we need to ask for more information,
21180 we may be unable to reach you. For this reason, it is better to send
21181 bug reports to the mailing list.
21183 The fundamental principle of reporting bugs usefully is this:
21184 @strong{report all the facts}. If you are not sure whether to state a
21185 fact or leave it out, state it!
21187 Often people omit facts because they think they know what causes the
21188 problem and assume that some details do not matter. Thus, you might
21189 assume that the name of the variable you use in an example does not matter.
21190 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
21191 stray memory reference which happens to fetch from the location where that
21192 name is stored in memory; perhaps, if the name were different, the contents
21193 of that location would fool the debugger into doing the right thing despite
21194 the bug. Play it safe and give a specific, complete example. That is the
21195 easiest thing for you to do, and the most helpful.
21197 Keep in mind that the purpose of a bug report is to enable us to fix the
21198 bug. It may be that the bug has been reported previously, but neither
21199 you nor we can know that unless your bug report is complete and
21202 Sometimes people give a few sketchy facts and ask, ``Does this ring a
21203 bell?'' Those bug reports are useless, and we urge everyone to
21204 @emph{refuse to respond to them} except to chide the sender to report
21207 To enable us to fix the bug, you should include all these things:
21211 The version of @value{GDBN}. @value{GDBN} announces it if you start
21212 with no arguments; you can also print it at any time using @code{show
21215 Without this, we will not know whether there is any point in looking for
21216 the bug in the current version of @value{GDBN}.
21219 The type of machine you are using, and the operating system name and
21223 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
21224 ``@value{GCC}--2.8.1''.
21227 What compiler (and its version) was used to compile the program you are
21228 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
21229 C Compiler''. For GCC, you can say @code{gcc --version} to get this
21230 information; for other compilers, see the documentation for those
21234 The command arguments you gave the compiler to compile your example and
21235 observe the bug. For example, did you use @samp{-O}? To guarantee
21236 you will not omit something important, list them all. A copy of the
21237 Makefile (or the output from make) is sufficient.
21239 If we were to try to guess the arguments, we would probably guess wrong
21240 and then we might not encounter the bug.
21243 A complete input script, and all necessary source files, that will
21247 A description of what behavior you observe that you believe is
21248 incorrect. For example, ``It gets a fatal signal.''
21250 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
21251 will certainly notice it. But if the bug is incorrect output, we might
21252 not notice unless it is glaringly wrong. You might as well not give us
21253 a chance to make a mistake.
21255 Even if the problem you experience is a fatal signal, you should still
21256 say so explicitly. Suppose something strange is going on, such as, your
21257 copy of @value{GDBN} is out of synch, or you have encountered a bug in
21258 the C library on your system. (This has happened!) Your copy might
21259 crash and ours would not. If you told us to expect a crash, then when
21260 ours fails to crash, we would know that the bug was not happening for
21261 us. If you had not told us to expect a crash, then we would not be able
21262 to draw any conclusion from our observations.
21265 @cindex recording a session script
21266 To collect all this information, you can use a session recording program
21267 such as @command{script}, which is available on many Unix systems.
21268 Just run your @value{GDBN} session inside @command{script} and then
21269 include the @file{typescript} file with your bug report.
21271 Another way to record a @value{GDBN} session is to run @value{GDBN}
21272 inside Emacs and then save the entire buffer to a file.
21275 If you wish to suggest changes to the @value{GDBN} source, send us context
21276 diffs. If you even discuss something in the @value{GDBN} source, refer to
21277 it by context, not by line number.
21279 The line numbers in our development sources will not match those in your
21280 sources. Your line numbers would convey no useful information to us.
21284 Here are some things that are not necessary:
21288 A description of the envelope of the bug.
21290 Often people who encounter a bug spend a lot of time investigating
21291 which changes to the input file will make the bug go away and which
21292 changes will not affect it.
21294 This is often time consuming and not very useful, because the way we
21295 will find the bug is by running a single example under the debugger
21296 with breakpoints, not by pure deduction from a series of examples.
21297 We recommend that you save your time for something else.
21299 Of course, if you can find a simpler example to report @emph{instead}
21300 of the original one, that is a convenience for us. Errors in the
21301 output will be easier to spot, running under the debugger will take
21302 less time, and so on.
21304 However, simplification is not vital; if you do not want to do this,
21305 report the bug anyway and send us the entire test case you used.
21308 A patch for the bug.
21310 A patch for the bug does help us if it is a good one. But do not omit
21311 the necessary information, such as the test case, on the assumption that
21312 a patch is all we need. We might see problems with your patch and decide
21313 to fix the problem another way, or we might not understand it at all.
21315 Sometimes with a program as complicated as @value{GDBN} it is very hard to
21316 construct an example that will make the program follow a certain path
21317 through the code. If you do not send us the example, we will not be able
21318 to construct one, so we will not be able to verify that the bug is fixed.
21320 And if we cannot understand what bug you are trying to fix, or why your
21321 patch should be an improvement, we will not install it. A test case will
21322 help us to understand.
21325 A guess about what the bug is or what it depends on.
21327 Such guesses are usually wrong. Even we cannot guess right about such
21328 things without first using the debugger to find the facts.
21331 @c The readline documentation is distributed with the readline code
21332 @c and consists of the two following files:
21334 @c inc-hist.texinfo
21335 @c Use -I with makeinfo to point to the appropriate directory,
21336 @c environment var TEXINPUTS with TeX.
21337 @include rluser.texinfo
21338 @include inc-hist.texinfo
21341 @node Formatting Documentation
21342 @appendix Formatting Documentation
21344 @cindex @value{GDBN} reference card
21345 @cindex reference card
21346 The @value{GDBN} 4 release includes an already-formatted reference card, ready
21347 for printing with PostScript or Ghostscript, in the @file{gdb}
21348 subdirectory of the main source directory@footnote{In
21349 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
21350 release.}. If you can use PostScript or Ghostscript with your printer,
21351 you can print the reference card immediately with @file{refcard.ps}.
21353 The release also includes the source for the reference card. You
21354 can format it, using @TeX{}, by typing:
21360 The @value{GDBN} reference card is designed to print in @dfn{landscape}
21361 mode on US ``letter'' size paper;
21362 that is, on a sheet 11 inches wide by 8.5 inches
21363 high. You will need to specify this form of printing as an option to
21364 your @sc{dvi} output program.
21366 @cindex documentation
21368 All the documentation for @value{GDBN} comes as part of the machine-readable
21369 distribution. The documentation is written in Texinfo format, which is
21370 a documentation system that uses a single source file to produce both
21371 on-line information and a printed manual. You can use one of the Info
21372 formatting commands to create the on-line version of the documentation
21373 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
21375 @value{GDBN} includes an already formatted copy of the on-line Info
21376 version of this manual in the @file{gdb} subdirectory. The main Info
21377 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
21378 subordinate files matching @samp{gdb.info*} in the same directory. If
21379 necessary, you can print out these files, or read them with any editor;
21380 but they are easier to read using the @code{info} subsystem in @sc{gnu}
21381 Emacs or the standalone @code{info} program, available as part of the
21382 @sc{gnu} Texinfo distribution.
21384 If you want to format these Info files yourself, you need one of the
21385 Info formatting programs, such as @code{texinfo-format-buffer} or
21388 If you have @code{makeinfo} installed, and are in the top level
21389 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
21390 version @value{GDBVN}), you can make the Info file by typing:
21397 If you want to typeset and print copies of this manual, you need @TeX{},
21398 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
21399 Texinfo definitions file.
21401 @TeX{} is a typesetting program; it does not print files directly, but
21402 produces output files called @sc{dvi} files. To print a typeset
21403 document, you need a program to print @sc{dvi} files. If your system
21404 has @TeX{} installed, chances are it has such a program. The precise
21405 command to use depends on your system; @kbd{lpr -d} is common; another
21406 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
21407 require a file name without any extension or a @samp{.dvi} extension.
21409 @TeX{} also requires a macro definitions file called
21410 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
21411 written in Texinfo format. On its own, @TeX{} cannot either read or
21412 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
21413 and is located in the @file{gdb-@var{version-number}/texinfo}
21416 If you have @TeX{} and a @sc{dvi} printer program installed, you can
21417 typeset and print this manual. First switch to the the @file{gdb}
21418 subdirectory of the main source directory (for example, to
21419 @file{gdb-@value{GDBVN}/gdb}) and type:
21425 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
21427 @node Installing GDB
21428 @appendix Installing @value{GDBN}
21429 @cindex configuring @value{GDBN}
21430 @cindex installation
21431 @cindex configuring @value{GDBN}, and source tree subdirectories
21433 @value{GDBN} comes with a @code{configure} script that automates the process
21434 of preparing @value{GDBN} for installation; you can then use @code{make} to
21435 build the @code{gdb} program.
21437 @c irrelevant in info file; it's as current as the code it lives with.
21438 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
21439 look at the @file{README} file in the sources; we may have improved the
21440 installation procedures since publishing this manual.}
21443 The @value{GDBN} distribution includes all the source code you need for
21444 @value{GDBN} in a single directory, whose name is usually composed by
21445 appending the version number to @samp{gdb}.
21447 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
21448 @file{gdb-@value{GDBVN}} directory. That directory contains:
21451 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
21452 script for configuring @value{GDBN} and all its supporting libraries
21454 @item gdb-@value{GDBVN}/gdb
21455 the source specific to @value{GDBN} itself
21457 @item gdb-@value{GDBVN}/bfd
21458 source for the Binary File Descriptor library
21460 @item gdb-@value{GDBVN}/include
21461 @sc{gnu} include files
21463 @item gdb-@value{GDBVN}/libiberty
21464 source for the @samp{-liberty} free software library
21466 @item gdb-@value{GDBVN}/opcodes
21467 source for the library of opcode tables and disassemblers
21469 @item gdb-@value{GDBVN}/readline
21470 source for the @sc{gnu} command-line interface
21472 @item gdb-@value{GDBVN}/glob
21473 source for the @sc{gnu} filename pattern-matching subroutine
21475 @item gdb-@value{GDBVN}/mmalloc
21476 source for the @sc{gnu} memory-mapped malloc package
21479 The simplest way to configure and build @value{GDBN} is to run @code{configure}
21480 from the @file{gdb-@var{version-number}} source directory, which in
21481 this example is the @file{gdb-@value{GDBVN}} directory.
21483 First switch to the @file{gdb-@var{version-number}} source directory
21484 if you are not already in it; then run @code{configure}. Pass the
21485 identifier for the platform on which @value{GDBN} will run as an
21491 cd gdb-@value{GDBVN}
21492 ./configure @var{host}
21497 where @var{host} is an identifier such as @samp{sun4} or
21498 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
21499 (You can often leave off @var{host}; @code{configure} tries to guess the
21500 correct value by examining your system.)
21502 Running @samp{configure @var{host}} and then running @code{make} builds the
21503 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
21504 libraries, then @code{gdb} itself. The configured source files, and the
21505 binaries, are left in the corresponding source directories.
21508 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
21509 system does not recognize this automatically when you run a different
21510 shell, you may need to run @code{sh} on it explicitly:
21513 sh configure @var{host}
21516 If you run @code{configure} from a directory that contains source
21517 directories for multiple libraries or programs, such as the
21518 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
21519 creates configuration files for every directory level underneath (unless
21520 you tell it not to, with the @samp{--norecursion} option).
21522 You should run the @code{configure} script from the top directory in the
21523 source tree, the @file{gdb-@var{version-number}} directory. If you run
21524 @code{configure} from one of the subdirectories, you will configure only
21525 that subdirectory. That is usually not what you want. In particular,
21526 if you run the first @code{configure} from the @file{gdb} subdirectory
21527 of the @file{gdb-@var{version-number}} directory, you will omit the
21528 configuration of @file{bfd}, @file{readline}, and other sibling
21529 directories of the @file{gdb} subdirectory. This leads to build errors
21530 about missing include files such as @file{bfd/bfd.h}.
21532 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
21533 However, you should make sure that the shell on your path (named by
21534 the @samp{SHELL} environment variable) is publicly readable. Remember
21535 that @value{GDBN} uses the shell to start your program---some systems refuse to
21536 let @value{GDBN} debug child processes whose programs are not readable.
21539 * Separate Objdir:: Compiling @value{GDBN} in another directory
21540 * Config Names:: Specifying names for hosts and targets
21541 * Configure Options:: Summary of options for configure
21544 @node Separate Objdir
21545 @section Compiling @value{GDBN} in another directory
21547 If you want to run @value{GDBN} versions for several host or target machines,
21548 you need a different @code{gdb} compiled for each combination of
21549 host and target. @code{configure} is designed to make this easy by
21550 allowing you to generate each configuration in a separate subdirectory,
21551 rather than in the source directory. If your @code{make} program
21552 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
21553 @code{make} in each of these directories builds the @code{gdb}
21554 program specified there.
21556 To build @code{gdb} in a separate directory, run @code{configure}
21557 with the @samp{--srcdir} option to specify where to find the source.
21558 (You also need to specify a path to find @code{configure}
21559 itself from your working directory. If the path to @code{configure}
21560 would be the same as the argument to @samp{--srcdir}, you can leave out
21561 the @samp{--srcdir} option; it is assumed.)
21563 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
21564 separate directory for a Sun 4 like this:
21568 cd gdb-@value{GDBVN}
21571 ../gdb-@value{GDBVN}/configure sun4
21576 When @code{configure} builds a configuration using a remote source
21577 directory, it creates a tree for the binaries with the same structure
21578 (and using the same names) as the tree under the source directory. In
21579 the example, you'd find the Sun 4 library @file{libiberty.a} in the
21580 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
21581 @file{gdb-sun4/gdb}.
21583 Make sure that your path to the @file{configure} script has just one
21584 instance of @file{gdb} in it. If your path to @file{configure} looks
21585 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
21586 one subdirectory of @value{GDBN}, not the whole package. This leads to
21587 build errors about missing include files such as @file{bfd/bfd.h}.
21589 One popular reason to build several @value{GDBN} configurations in separate
21590 directories is to configure @value{GDBN} for cross-compiling (where
21591 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
21592 programs that run on another machine---the @dfn{target}).
21593 You specify a cross-debugging target by
21594 giving the @samp{--target=@var{target}} option to @code{configure}.
21596 When you run @code{make} to build a program or library, you must run
21597 it in a configured directory---whatever directory you were in when you
21598 called @code{configure} (or one of its subdirectories).
21600 The @code{Makefile} that @code{configure} generates in each source
21601 directory also runs recursively. If you type @code{make} in a source
21602 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
21603 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
21604 will build all the required libraries, and then build GDB.
21606 When you have multiple hosts or targets configured in separate
21607 directories, you can run @code{make} on them in parallel (for example,
21608 if they are NFS-mounted on each of the hosts); they will not interfere
21612 @section Specifying names for hosts and targets
21614 The specifications used for hosts and targets in the @code{configure}
21615 script are based on a three-part naming scheme, but some short predefined
21616 aliases are also supported. The full naming scheme encodes three pieces
21617 of information in the following pattern:
21620 @var{architecture}-@var{vendor}-@var{os}
21623 For example, you can use the alias @code{sun4} as a @var{host} argument,
21624 or as the value for @var{target} in a @code{--target=@var{target}}
21625 option. The equivalent full name is @samp{sparc-sun-sunos4}.
21627 The @code{configure} script accompanying @value{GDBN} does not provide
21628 any query facility to list all supported host and target names or
21629 aliases. @code{configure} calls the Bourne shell script
21630 @code{config.sub} to map abbreviations to full names; you can read the
21631 script, if you wish, or you can use it to test your guesses on
21632 abbreviations---for example:
21635 % sh config.sub i386-linux
21637 % sh config.sub alpha-linux
21638 alpha-unknown-linux-gnu
21639 % sh config.sub hp9k700
21641 % sh config.sub sun4
21642 sparc-sun-sunos4.1.1
21643 % sh config.sub sun3
21644 m68k-sun-sunos4.1.1
21645 % sh config.sub i986v
21646 Invalid configuration `i986v': machine `i986v' not recognized
21650 @code{config.sub} is also distributed in the @value{GDBN} source
21651 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
21653 @node Configure Options
21654 @section @code{configure} options
21656 Here is a summary of the @code{configure} options and arguments that
21657 are most often useful for building @value{GDBN}. @code{configure} also has
21658 several other options not listed here. @inforef{What Configure
21659 Does,,configure.info}, for a full explanation of @code{configure}.
21662 configure @r{[}--help@r{]}
21663 @r{[}--prefix=@var{dir}@r{]}
21664 @r{[}--exec-prefix=@var{dir}@r{]}
21665 @r{[}--srcdir=@var{dirname}@r{]}
21666 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
21667 @r{[}--target=@var{target}@r{]}
21672 You may introduce options with a single @samp{-} rather than
21673 @samp{--} if you prefer; but you may abbreviate option names if you use
21678 Display a quick summary of how to invoke @code{configure}.
21680 @item --prefix=@var{dir}
21681 Configure the source to install programs and files under directory
21684 @item --exec-prefix=@var{dir}
21685 Configure the source to install programs under directory
21688 @c avoid splitting the warning from the explanation:
21690 @item --srcdir=@var{dirname}
21691 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
21692 @code{make} that implements the @code{VPATH} feature.}@*
21693 Use this option to make configurations in directories separate from the
21694 @value{GDBN} source directories. Among other things, you can use this to
21695 build (or maintain) several configurations simultaneously, in separate
21696 directories. @code{configure} writes configuration specific files in
21697 the current directory, but arranges for them to use the source in the
21698 directory @var{dirname}. @code{configure} creates directories under
21699 the working directory in parallel to the source directories below
21702 @item --norecursion
21703 Configure only the directory level where @code{configure} is executed; do not
21704 propagate configuration to subdirectories.
21706 @item --target=@var{target}
21707 Configure @value{GDBN} for cross-debugging programs running on the specified
21708 @var{target}. Without this option, @value{GDBN} is configured to debug
21709 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
21711 There is no convenient way to generate a list of all available targets.
21713 @item @var{host} @dots{}
21714 Configure @value{GDBN} to run on the specified @var{host}.
21716 There is no convenient way to generate a list of all available hosts.
21719 There are many other options available as well, but they are generally
21720 needed for special purposes only.
21722 @node Maintenance Commands
21723 @appendix Maintenance Commands
21724 @cindex maintenance commands
21725 @cindex internal commands
21727 In addition to commands intended for @value{GDBN} users, @value{GDBN}
21728 includes a number of commands intended for @value{GDBN} developers,
21729 that are not documented elsewhere in this manual. These commands are
21730 provided here for reference. (For commands that turn on debugging
21731 messages, see @ref{Debugging Output}.)
21734 @kindex maint agent
21735 @item maint agent @var{expression}
21736 Translate the given @var{expression} into remote agent bytecodes.
21737 This command is useful for debugging the Agent Expression mechanism
21738 (@pxref{Agent Expressions}).
21740 @kindex maint info breakpoints
21741 @item @anchor{maint info breakpoints}maint info breakpoints
21742 Using the same format as @samp{info breakpoints}, display both the
21743 breakpoints you've set explicitly, and those @value{GDBN} is using for
21744 internal purposes. Internal breakpoints are shown with negative
21745 breakpoint numbers. The type column identifies what kind of breakpoint
21750 Normal, explicitly set breakpoint.
21753 Normal, explicitly set watchpoint.
21756 Internal breakpoint, used to handle correctly stepping through
21757 @code{longjmp} calls.
21759 @item longjmp resume
21760 Internal breakpoint at the target of a @code{longjmp}.
21763 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
21766 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
21769 Shared library events.
21773 @kindex maint check-symtabs
21774 @item maint check-symtabs
21775 Check the consistency of psymtabs and symtabs.
21777 @kindex maint cplus first_component
21778 @item maint cplus first_component @var{name}
21779 Print the first C@t{++} class/namespace component of @var{name}.
21781 @kindex maint cplus namespace
21782 @item maint cplus namespace
21783 Print the list of possible C@t{++} namespaces.
21785 @kindex maint demangle
21786 @item maint demangle @var{name}
21787 Demangle a C@t{++} or Objective-C manled @var{name}.
21789 @kindex maint deprecate
21790 @kindex maint undeprecate
21791 @cindex deprecated commands
21792 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
21793 @itemx maint undeprecate @var{command}
21794 Deprecate or undeprecate the named @var{command}. Deprecated commands
21795 cause @value{GDBN} to issue a warning when you use them. The optional
21796 argument @var{replacement} says which newer command should be used in
21797 favor of the deprecated one; if it is given, @value{GDBN} will mention
21798 the replacement as part of the warning.
21800 @kindex maint dump-me
21801 @item maint dump-me
21802 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
21803 Cause a fatal signal in the debugger and force it to dump its core.
21804 This is supported only on systems which support aborting a program
21805 with the @code{SIGQUIT} signal.
21807 @kindex maint internal-error
21808 @kindex maint internal-warning
21809 @item maint internal-error @r{[}@var{message-text}@r{]}
21810 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
21811 Cause @value{GDBN} to call the internal function @code{internal_error}
21812 or @code{internal_warning} and hence behave as though an internal error
21813 or internal warning has been detected. In addition to reporting the
21814 internal problem, these functions give the user the opportunity to
21815 either quit @value{GDBN} or create a core file of the current
21816 @value{GDBN} session.
21818 These commands take an optional parameter @var{message-text} that is
21819 used as the text of the error or warning message.
21821 Here's an example of using @code{indernal-error}:
21824 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
21825 @dots{}/maint.c:121: internal-error: testing, 1, 2
21826 A problem internal to GDB has been detected. Further
21827 debugging may prove unreliable.
21828 Quit this debugging session? (y or n) @kbd{n}
21829 Create a core file? (y or n) @kbd{n}
21833 @kindex maint packet
21834 @item maint packet @var{text}
21835 If @value{GDBN} is talking to an inferior via the serial protocol,
21836 then this command sends the string @var{text} to the inferior, and
21837 displays the response packet. @value{GDBN} supplies the initial
21838 @samp{$} character, the terminating @samp{#} character, and the
21841 @kindex maint print architecture
21842 @item maint print architecture @r{[}@var{file}@r{]}
21843 Print the entire architecture configuration. The optional argument
21844 @var{file} names the file where the output goes.
21846 @kindex maint print dummy-frames
21847 @item maint print dummy-frames
21848 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
21851 (@value{GDBP}) @kbd{b add}
21853 (@value{GDBP}) @kbd{print add(2,3)}
21854 Breakpoint 2, add (a=2, b=3) at @dots{}
21856 The program being debugged stopped while in a function called from GDB.
21858 (@value{GDBP}) @kbd{maint print dummy-frames}
21859 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
21860 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
21861 call_lo=0x01014000 call_hi=0x01014001
21865 Takes an optional file parameter.
21867 @kindex maint print registers
21868 @kindex maint print raw-registers
21869 @kindex maint print cooked-registers
21870 @kindex maint print register-groups
21871 @item maint print registers @r{[}@var{file}@r{]}
21872 @itemx maint print raw-registers @r{[}@var{file}@r{]}
21873 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
21874 @itemx maint print register-groups @r{[}@var{file}@r{]}
21875 Print @value{GDBN}'s internal register data structures.
21877 The command @code{maint print raw-registers} includes the contents of
21878 the raw register cache; the command @code{maint print cooked-registers}
21879 includes the (cooked) value of all registers; and the command
21880 @code{maint print register-groups} includes the groups that each
21881 register is a member of. @xref{Registers,, Registers, gdbint,
21882 @value{GDBN} Internals}.
21884 These commands take an optional parameter, a file name to which to
21885 write the information.
21887 @kindex maint print reggroups
21888 @item maint print reggroups @r{[}@var{file}@r{]}
21889 Print @value{GDBN}'s internal register group data structures. The
21890 optional argument @var{file} tells to what file to write the
21893 The register groups info looks like this:
21896 (@value{GDBP}) @kbd{maint print reggroups}
21909 This command forces @value{GDBN} to flush its internal register cache.
21911 @kindex maint print objfiles
21912 @cindex info for known object files
21913 @item maint print objfiles
21914 Print a dump of all known object files. For each object file, this
21915 command prints its name, address in memory, and all of its psymtabs
21918 @kindex maint print statistics
21919 @cindex bcache statistics
21920 @item maint print statistics
21921 This command prints, for each object file in the program, various data
21922 about that object file followed by the byte cache (@dfn{bcache})
21923 statistics for the object file. The objfile data includes the number
21924 of minimal, partical, full, and stabs symbols, the number of types
21925 defined by the objfile, the number of as yet unexpanded psym tables,
21926 the number of line tables and string tables, and the amount of memory
21927 used by the various tables. The bcache statistics include the counts,
21928 sizes, and counts of duplicates of all and unique objects, max,
21929 average, and median entry size, total memory used and its overhead and
21930 savings, and various measures of the hash table size and chain
21933 @kindex maint print type
21934 @cindex type chain of a data type
21935 @item maint print type @var{expr}
21936 Print the type chain for a type specified by @var{expr}. The argument
21937 can be either a type name or a symbol. If it is a symbol, the type of
21938 that symbol is described. The type chain produced by this command is
21939 a recursive definition of the data type as stored in @value{GDBN}'s
21940 data structures, including its flags and contained types.
21942 @kindex maint set dwarf2 max-cache-age
21943 @kindex maint show dwarf2 max-cache-age
21944 @item maint set dwarf2 max-cache-age
21945 @itemx maint show dwarf2 max-cache-age
21946 Control the DWARF 2 compilation unit cache.
21948 @cindex DWARF 2 compilation units cache
21949 In object files with inter-compilation-unit references, such as those
21950 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
21951 reader needs to frequently refer to previously read compilation units.
21952 This setting controls how long a compilation unit will remain in the
21953 cache if it is not referenced. A higher limit means that cached
21954 compilation units will be stored in memory longer, and more total
21955 memory will be used. Setting it to zero disables caching, which will
21956 slow down @value{GDBN} startup, but reduce memory consumption.
21958 @kindex maint set profile
21959 @kindex maint show profile
21960 @cindex profiling GDB
21961 @item maint set profile
21962 @itemx maint show profile
21963 Control profiling of @value{GDBN}.
21965 Profiling will be disabled until you use the @samp{maint set profile}
21966 command to enable it. When you enable profiling, the system will begin
21967 collecting timing and execution count data; when you disable profiling or
21968 exit @value{GDBN}, the results will be written to a log file. Remember that
21969 if you use profiling, @value{GDBN} will overwrite the profiling log file
21970 (often called @file{gmon.out}). If you have a record of important profiling
21971 data in a @file{gmon.out} file, be sure to move it to a safe location.
21973 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
21974 compiled with the @samp{-pg} compiler option.
21976 @kindex maint show-debug-regs
21977 @cindex x86 hardware debug registers
21978 @item maint show-debug-regs
21979 Control whether to show variables that mirror the x86 hardware debug
21980 registers. Use @code{ON} to enable, @code{OFF} to disable. If
21981 enabled, the debug registers values are shown when GDB inserts or
21982 removes a hardware breakpoint or watchpoint, and when the inferior
21983 triggers a hardware-assisted breakpoint or watchpoint.
21985 @kindex maint space
21986 @cindex memory used by commands
21988 Control whether to display memory usage for each command. If set to a
21989 nonzero value, @value{GDBN} will display how much memory each command
21990 took, following the command's own output. This can also be requested
21991 by invoking @value{GDBN} with the @option{--statistics} command-line
21992 switch (@pxref{Mode Options}).
21995 @cindex time of command execution
21997 Control whether to display the execution time for each command. If
21998 set to a nonzero value, @value{GDBN} will display how much time it
21999 took to execute each command, following the command's own output.
22000 This can also be requested by invoking @value{GDBN} with the
22001 @option{--statistics} command-line switch (@pxref{Mode Options}).
22003 @kindex maint translate-address
22004 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
22005 Find the symbol stored at the location specified by the address
22006 @var{addr} and an optional section name @var{section}. If found,
22007 @value{GDBN} prints the name of the closest symbol and an offset from
22008 the symbol's location to the specified address. This is similar to
22009 the @code{info address} command (@pxref{Symbols}), except that this
22010 command also allows to find symbols in other sections.
22014 The following command is useful for non-interactive invocations of
22015 @value{GDBN}, such as in the test suite.
22018 @item set watchdog @var{nsec}
22019 @kindex set watchdog
22020 @cindex watchdog timer
22021 @cindex timeout for commands
22022 Set the maximum number of seconds @value{GDBN} will wait for the
22023 target operation to finish. If this time expires, @value{GDBN}
22024 reports and error and the command is aborted.
22026 @item show watchdog
22027 Show the current setting of the target wait timeout.
22030 @node Remote Protocol
22031 @appendix @value{GDBN} Remote Serial Protocol
22036 * Stop Reply Packets::
22037 * General Query Packets::
22038 * Register Packet Format::
22039 * Tracepoint Packets::
22042 * File-I/O remote protocol extension::
22048 There may be occasions when you need to know something about the
22049 protocol---for example, if there is only one serial port to your target
22050 machine, you might want your program to do something special if it
22051 recognizes a packet meant for @value{GDBN}.
22053 In the examples below, @samp{->} and @samp{<-} are used to indicate
22054 transmitted and received data respectfully.
22056 @cindex protocol, @value{GDBN} remote serial
22057 @cindex serial protocol, @value{GDBN} remote
22058 @cindex remote serial protocol
22059 All @value{GDBN} commands and responses (other than acknowledgments) are
22060 sent as a @var{packet}. A @var{packet} is introduced with the character
22061 @samp{$}, the actual @var{packet-data}, and the terminating character
22062 @samp{#} followed by a two-digit @var{checksum}:
22065 @code{$}@var{packet-data}@code{#}@var{checksum}
22069 @cindex checksum, for @value{GDBN} remote
22071 The two-digit @var{checksum} is computed as the modulo 256 sum of all
22072 characters between the leading @samp{$} and the trailing @samp{#} (an
22073 eight bit unsigned checksum).
22075 Implementors should note that prior to @value{GDBN} 5.0 the protocol
22076 specification also included an optional two-digit @var{sequence-id}:
22079 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
22082 @cindex sequence-id, for @value{GDBN} remote
22084 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
22085 has never output @var{sequence-id}s. Stubs that handle packets added
22086 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
22088 @cindex acknowledgment, for @value{GDBN} remote
22089 When either the host or the target machine receives a packet, the first
22090 response expected is an acknowledgment: either @samp{+} (to indicate
22091 the package was received correctly) or @samp{-} (to request
22095 -> @code{$}@var{packet-data}@code{#}@var{checksum}
22100 The host (@value{GDBN}) sends @var{command}s, and the target (the
22101 debugging stub incorporated in your program) sends a @var{response}. In
22102 the case of step and continue @var{command}s, the response is only sent
22103 when the operation has completed (the target has again stopped).
22105 @var{packet-data} consists of a sequence of characters with the
22106 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
22109 Fields within the packet should be separated using @samp{,} @samp{;} or
22110 @cindex remote protocol, field separator
22111 @samp{:}. Except where otherwise noted all numbers are represented in
22112 @sc{hex} with leading zeros suppressed.
22114 Implementors should note that prior to @value{GDBN} 5.0, the character
22115 @samp{:} could not appear as the third character in a packet (as it
22116 would potentially conflict with the @var{sequence-id}).
22118 Response @var{data} can be run-length encoded to save space. A @samp{*}
22119 means that the next character is an @sc{ascii} encoding giving a repeat count
22120 which stands for that many repetitions of the character preceding the
22121 @samp{*}. The encoding is @code{n+29}, yielding a printable character
22122 where @code{n >=3} (which is where rle starts to win). The printable
22123 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
22124 value greater than 126 should not be used.
22131 means the same as "0000".
22133 The error response returned for some packets includes a two character
22134 error number. That number is not well defined.
22136 For any @var{command} not supported by the stub, an empty response
22137 (@samp{$#00}) should be returned. That way it is possible to extend the
22138 protocol. A newer @value{GDBN} can tell if a packet is supported based
22141 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
22142 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
22148 The following table provides a complete list of all currently defined
22149 @var{command}s and their corresponding response @var{data}.
22150 @xref{File-I/O remote protocol extension}, for details about the File
22151 I/O extension of the remote protocol.
22153 Each packet's description has a template showing the packet's overall
22154 syntax, followed by an explanation of the packet's meaning. We
22155 include spaces in some of the templates for clarity; these are not
22156 part of the packet's syntax. No @value{GDBN} packet uses spaces to
22157 separate its components. For example, a template like @samp{foo
22158 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
22159 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
22160 @var{baz}. GDB does not transmit a space character between the
22161 @samp{foo} and the @var{bar}, or between the @var{bar} and the
22164 Note that all packet forms beginning with an upper- or lower-case
22165 letter, other than those described here, are reserved for future use.
22167 Here are the packet descriptions.
22172 @cindex @samp{!} packet
22173 Enable extended mode. In extended mode, the remote server is made
22174 persistent. The @samp{R} packet is used to restart the program being
22180 The remote target both supports and has enabled extended mode.
22184 @cindex @samp{?} packet
22185 Indicate the reason the target halted. The reply is the same as for
22189 @xref{Stop Reply Packets}, for the reply specifications.
22191 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
22192 @cindex @samp{A} packet
22193 Initialized @code{argv[]} array passed into program. @var{arglen}
22194 specifies the number of bytes in the hex encoded byte stream
22195 @var{arg}. See @code{gdbserver} for more details.
22200 The arguments were set.
22206 @cindex @samp{b} packet
22207 (Don't use this packet; its behavior is not well-defined.)
22208 Change the serial line speed to @var{baud}.
22210 JTC: @emph{When does the transport layer state change? When it's
22211 received, or after the ACK is transmitted. In either case, there are
22212 problems if the command or the acknowledgment packet is dropped.}
22214 Stan: @emph{If people really wanted to add something like this, and get
22215 it working for the first time, they ought to modify ser-unix.c to send
22216 some kind of out-of-band message to a specially-setup stub and have the
22217 switch happen "in between" packets, so that from remote protocol's point
22218 of view, nothing actually happened.}
22220 @item B @var{addr},@var{mode}
22221 @cindex @samp{B} packet
22222 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
22223 breakpoint at @var{addr}.
22225 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
22226 (@pxref{insert breakpoint or watchpoint packet}).
22229 @cindex @samp{c} packet
22230 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
22231 resume at current address.
22234 @xref{Stop Reply Packets}, for the reply specifications.
22236 @item C @var{sig};@var{addr}
22237 @cindex @samp{C} packet
22238 Continue with signal @var{sig} (hex signal number). If
22239 @samp{;@var{addr}} is omitted, resume at same address.
22242 @xref{Stop Reply Packets}, for the reply specifications.
22245 @cindex @samp{d} packet
22248 Don't use this packet; instead, define a general set packet
22249 (@pxref{General Query Packets}).
22252 @cindex @samp{D} packet
22253 Detach @value{GDBN} from the remote system. Sent to the remote target
22254 before @value{GDBN} disconnects via the @code{detach} command.
22264 @item F @var{RC},@var{EE},@var{CF};@var{XX}
22265 @cindex @samp{F} packet
22266 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
22267 This is part of the File-I/O protocol extension. @xref{File-I/O
22268 remote protocol extension}, for the specification.
22271 @anchor{read registers packet}
22272 @cindex @samp{g} packet
22273 Read general registers.
22277 @item @var{XX@dots{}}
22278 Each byte of register data is described by two hex digits. The bytes
22279 with the register are transmitted in target byte order. The size of
22280 each register and their position within the @samp{g} packet are
22281 determined by the @value{GDBN} internal macros
22282 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{REGISTER_NAME} macros. The
22283 specification of several standard @samp{g} packets is specified below.
22288 @item G @var{XX@dots{}}
22289 @cindex @samp{G} packet
22290 Write general registers. @xref{read registers packet}, for a
22291 description of the @var{XX@dots{}} data.
22301 @item H @var{c} @var{t}
22302 @cindex @samp{H} packet
22303 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
22304 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
22305 should be @samp{c} for step and continue operations, @samp{g} for other
22306 operations. The thread designator @var{t} may be @samp{-1}, meaning all
22307 the threads, a thread number, or @samp{0} which means pick any thread.
22318 @c 'H': How restrictive (or permissive) is the thread model. If a
22319 @c thread is selected and stopped, are other threads allowed
22320 @c to continue to execute? As I mentioned above, I think the
22321 @c semantics of each command when a thread is selected must be
22322 @c described. For example:
22324 @c 'g': If the stub supports threads and a specific thread is
22325 @c selected, returns the register block from that thread;
22326 @c otherwise returns current registers.
22328 @c 'G' If the stub supports threads and a specific thread is
22329 @c selected, sets the registers of the register block of
22330 @c that thread; otherwise sets current registers.
22332 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
22333 @anchor{cycle step packet}
22334 @cindex @samp{i} packet
22335 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
22336 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
22337 step starting at that address.
22340 @cindex @samp{I} packet
22341 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
22345 @cindex @samp{k} packet
22348 FIXME: @emph{There is no description of how to operate when a specific
22349 thread context has been selected (i.e.@: does 'k' kill only that
22352 @item m @var{addr},@var{length}
22353 @cindex @samp{m} packet
22354 Read @var{length} bytes of memory starting at address @var{addr}.
22355 Note that @var{addr} may not be aligned to any particular boundary.
22357 The stub need not use any particular size or alignment when gathering
22358 data from memory for the response; even if @var{addr} is word-aligned
22359 and @var{length} is a multiple of the word size, the stub is free to
22360 use byte accesses, or not. For this reason, this packet may not be
22361 suitable for accessing memory-mapped I/O devices.
22362 @cindex alignment of remote memory accesses
22363 @cindex size of remote memory accesses
22364 @cindex memory, alignment and size of remote accesses
22368 @item @var{XX@dots{}}
22369 Memory contents; each byte is transmitted as a two-digit hexidecimal
22370 number. The reply may contain fewer bytes than requested if the
22371 server was able to read only part of the region of memory.
22376 @item M @var{addr},@var{length}:@var{XX@dots{}}
22377 @cindex @samp{M} packet
22378 Write @var{length} bytes of memory starting at address @var{addr}.
22379 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
22380 hexidecimal number.
22387 for an error (this includes the case where only part of the data was
22392 @cindex @samp{p} packet
22393 Read the value of register @var{n}; @var{n} is in hex.
22394 @xref{read registers packet}, for a description of how the returned
22395 register value is encoded.
22399 @item @var{XX@dots{}}
22400 the register's value
22404 Indicating an unrecognized @var{query}.
22407 @item P @var{n@dots{}}=@var{r@dots{}}
22408 @anchor{write register packet}
22409 @cindex @samp{P} packet
22410 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
22411 number @var{n} is in hexidecimal, and @var{r@dots{}} contains two hex
22412 digits for each byte in the register (target byte order).
22422 @item q @var{name} @var{params}@dots{}
22423 @itemx Q @var{name} @var{params}@dots{}
22424 @cindex @samp{q} packet
22425 @cindex @samp{Q} packet
22426 General query (@samp{q}) and set (@samp{Q}). These packets are
22427 described fully in @ref{General Query Packets}.
22430 @cindex @samp{r} packet
22431 Reset the entire system.
22433 Don't use this packet; use the @samp{R} packet instead.
22436 @cindex @samp{R} packet
22437 Restart the program being debugged. @var{XX}, while needed, is ignored.
22438 This packet is only available in extended mode.
22440 The @samp{R} packet has no reply.
22443 @cindex @samp{s} packet
22444 Single step. @var{addr} is the address at which to resume. If
22445 @var{addr} is omitted, resume at same address.
22448 @xref{Stop Reply Packets}, for the reply specifications.
22450 @item S @var{sig};@var{addr}
22451 @anchor{step with signal packet}
22452 @cindex @samp{S} packet
22453 Step with signal. This is analogous to the @samp{C} packet, but
22454 requests a single-step, rather than a normal resumption of execution.
22457 @xref{Stop Reply Packets}, for the reply specifications.
22459 @item t @var{addr}:@var{PP},@var{MM}
22460 @cindex @samp{t} packet
22461 Search backwards starting at address @var{addr} for a match with pattern
22462 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
22463 @var{addr} must be at least 3 digits.
22466 @cindex @samp{T} packet
22467 Find out if the thread XX is alive.
22472 thread is still alive
22478 Packets starting with @samp{v} are identified by a multi-letter name,
22479 up to the first @samp{;} or @samp{?} (or the end of the packet).
22481 @item vCont@r{[};@var{action}@r{[}:@var{tid}@r{]]}@dots{}
22482 @cindex @samp{vCont} packet
22483 Resume the inferior, specifying different actions for each thread.
22484 If an action is specified with no @var{tid}, then it is applied to any
22485 threads that don't have a specific action specified; if no default action is
22486 specified then other threads should remain stopped. Specifying multiple
22487 default actions is an error; specifying no actions is also an error.
22488 Thread IDs are specified in hexadecimal. Currently supported actions are:
22494 Continue with signal @var{sig}. @var{sig} should be two hex digits.
22498 Step with signal @var{sig}. @var{sig} should be two hex digits.
22501 The optional @var{addr} argument normally associated with these packets is
22502 not supported in @samp{vCont}.
22505 @xref{Stop Reply Packets}, for the reply specifications.
22508 @cindex @samp{vCont?} packet
22509 Request a list of actions supporetd by the @samp{vCont} packet.
22513 @item vCont@r{[};@var{action}@dots{}@r{]}
22514 The @samp{vCont} packet is supported. Each @var{action} is a supported
22515 command in the @samp{vCont} packet.
22517 The @samp{vCont} packet is not supported.
22520 @item X @var{addr},@var{length}:@var{XX@dots{}}
22522 @cindex @samp{X} packet
22523 Write data to memory, where the data is transmitted in binary.
22524 @var{addr} is address, @var{length} is number of bytes,
22525 @samp{@var{XX}@dots{}} is binary data. The bytes @code{0x23}
22526 (@sc{ascii} @samp{#}), @code{0x24} (@sc{ascii} @samp{$}), and
22527 @code{0x7d} (@sc{ascii} @samp{@}}) are escaped using @code{0x7d}
22528 (@sc{ascii} @samp{@}}), and then XORed with @code{0x20}. For example,
22529 the byte @code{0x7d} would be transmitted as the two bytes @code{0x7d
22540 @item z @var{type},@var{addr},@var{length}
22541 @itemx Z @var{type},@var{addr},@var{length}
22542 @anchor{insert breakpoint or watchpoint packet}
22543 @cindex @samp{z} packet
22544 @cindex @samp{Z} packets
22545 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
22546 watchpoint starting at address @var{address} and covering the next
22547 @var{length} bytes.
22549 Each breakpoint and watchpoint packet @var{type} is documented
22552 @emph{Implementation notes: A remote target shall return an empty string
22553 for an unrecognized breakpoint or watchpoint packet @var{type}. A
22554 remote target shall support either both or neither of a given
22555 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
22556 avoid potential problems with duplicate packets, the operations should
22557 be implemented in an idempotent way.}
22559 @item z0,@var{addr},@var{length}
22560 @itemx Z0,@var{addr},@var{length}
22561 @cindex @samp{z0} packet
22562 @cindex @samp{Z0} packet
22563 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
22564 @var{addr} of size @var{length}.
22566 A memory breakpoint is implemented by replacing the instruction at
22567 @var{addr} with a software breakpoint or trap instruction. The
22568 @var{length} is used by targets that indicates the size of the
22569 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
22570 @sc{mips} can insert either a 2 or 4 byte breakpoint).
22572 @emph{Implementation note: It is possible for a target to copy or move
22573 code that contains memory breakpoints (e.g., when implementing
22574 overlays). The behavior of this packet, in the presence of such a
22575 target, is not defined.}
22587 @item z1,@var{addr},@var{length}
22588 @itemx Z1,@var{addr},@var{length}
22589 @cindex @samp{z1} packet
22590 @cindex @samp{Z1} packet
22591 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
22592 address @var{addr} of size @var{length}.
22594 A hardware breakpoint is implemented using a mechanism that is not
22595 dependant on being able to modify the target's memory.
22597 @emph{Implementation note: A hardware breakpoint is not affected by code
22610 @item z2,@var{addr},@var{length}
22611 @itemx Z2,@var{addr},@var{length}
22612 @cindex @samp{z2} packet
22613 @cindex @samp{Z2} packet
22614 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
22626 @item z3,@var{addr},@var{length}
22627 @itemx Z3,@var{addr},@var{length}
22628 @cindex @samp{z3} packet
22629 @cindex @samp{Z3} packet
22630 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
22642 @item z4,@var{addr},@var{length}
22643 @itemx Z4,@var{addr},@var{length}
22644 @cindex @samp{z4} packet
22645 @cindex @samp{Z4} packet
22646 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
22660 @node Stop Reply Packets
22661 @section Stop Reply Packets
22662 @cindex stop reply packets
22664 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
22665 receive any of the below as a reply. In the case of the @samp{C},
22666 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
22667 when the target halts. In the below the exact meaning of @dfn{signal
22668 number} is poorly defined. In general one of the UNIX signal
22669 numbering conventions is used.
22671 As in the description of request packets, we include spaces in the
22672 reply templates for clarity; these are not part of the reply packet's
22673 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
22679 The program received signal number @var{AA} (a two-digit hexidecimal
22682 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
22683 @cindex @samp{T} packet reply
22684 The program received signal number @var{AA} (a two-digit hexidecimal
22685 number). Single-step and breakpoint traps are reported this way. The
22686 @samp{@var{n}:@var{r}} pairs give the values of important registers or
22690 If @var{n} is a hexidecimal number, it is a register number, and the
22691 corresponding @var{r} gives that register's value. @var{r} is a
22692 series of bytes in target byte order, with each byte given by a
22693 two-digit hex number.
22695 If @var{n} is @samp{thread}, then @var{r} is the thread process ID, in
22698 If @var{n} is @samp{watch}, @samp{rwatch}, or @samp{awatch}, then the
22699 packet indicates a watchpoint hit, and @var{r} is the data address, in
22702 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
22703 and go on to the next; this allows us to extend the protocol in the
22708 The process exited, and @var{AA} is the exit status. This is only
22709 applicable to certain targets.
22712 The process terminated with signal @var{AA}.
22714 @item O @var{XX}@dots{}
22715 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
22716 written as the program's console output. This can happen at any time
22717 while the program is running and the debugger should continue to wait
22718 for @samp{W}, @samp{T}, etc.
22720 @item F @var{call-id},@var{parameter}@dots{}
22721 @var{call-id} is the identifier which says which host system call should
22722 be called. This is just the name of the function. Translation into the
22723 correct system call is only applicable as it's defined in @value{GDBN}.
22724 @xref{File-I/O remote protocol extension}, for a list of implemented
22727 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
22728 this very system call.
22730 The target replies with this packet when it expects @value{GDBN} to
22731 call a host system call on behalf of the target. @value{GDBN} replies
22732 with an appropriate @samp{F} packet and keeps up waiting for the next
22733 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
22734 or @samp{s} action is expected to be continued. @xref{File-I/O remote
22735 protocol extension}, for more details.
22739 @node General Query Packets
22740 @section General Query Packets
22741 @cindex remote query requests
22743 Packets starting with @samp{q} are @dfn{general query packets};
22744 packets starting with @samp{Q} are @dfn{general set packets}. General
22745 query and set packets are a semi-unified form for retrieving and
22746 sending information to and from the stub.
22748 The initial letter of a query or set packet is followed by a name
22749 indicating what sort of thing the packet applies to. For example,
22750 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
22751 definitions with the stub. These packet names follow some
22756 The name must not contain commas, colons or semicolons.
22758 Most @value{GDBN} query and set packets have a leading upper case
22761 The names of custom vendor packets should use a company prefix, in
22762 lower case, followed by a period. For example, packets designed at
22763 the Acme Corporation might begin with @samp{qacme.foo} (for querying
22764 foos) or @samp{Qacme.bar} (for setting bars).
22767 A query or set packet may optionally be followed by a @samp{,} or
22768 @samp{;} separated list. Stubs must be careful to match the full
22769 packet name, in case packet names have common prefixes.
22771 Like the descriptions of the other packets, each description here
22772 has a template showing the packet's overall syntax, followed by an
22773 explanation of the packet's meaning. We include spaces in some of the
22774 templates for clarity; these are not part of the packet's syntax. No
22775 @value{GDBN} packet uses spaces to separate its components.
22777 Here are the currently defined query and set packets:
22782 @cindex current thread, remote request
22783 @cindex @samp{qC} packet
22784 Return the current thread id.
22789 Where @var{pid} is an unsigned hexidecimal process id.
22790 @item @r{(anything else)}
22791 Any other reply implies the old pid.
22794 @item qCRC:@var{addr},@var{length}
22795 @cindex CRC of memory block, remote request
22796 @cindex @samp{qCRC} packet
22797 Compute the CRC checksum of a block of memory.
22801 An error (such as memory fault)
22802 @item C @var{crc32}
22803 The specified memory region's checksum is @var{crc32}.
22807 @itemx qsThreadInfo
22808 @cindex list active threads, remote request
22809 @cindex @samp{qfThreadInfo} packet
22810 @cindex @samp{qsThreadInfo} packet
22811 Obtain a list of all active thread ids from the target (OS). Since there
22812 may be too many active threads to fit into one reply packet, this query
22813 works iteratively: it may require more than one query/reply sequence to
22814 obtain the entire list of threads. The first query of the sequence will
22815 be the @samp{qfThreadInfo} query; subsequent queries in the
22816 sequence will be the @samp{qsThreadInfo} query.
22818 NOTE: This packet replaces the @samp{qL} query (see below).
22824 @item m @var{id},@var{id}@dots{}
22825 a comma-separated list of thread ids
22827 (lower case letter @samp{L}) denotes end of list.
22830 In response to each query, the target will reply with a list of one or
22831 more thread ids, in big-endian unsigned hex, separated by commas.
22832 @value{GDBN} will respond to each reply with a request for more thread
22833 ids (using the @samp{qs} form of the query), until the target responds
22834 with @samp{l} (lower-case el, for @dfn{last}).
22836 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
22837 @cindex get thread-local storage address, remote request
22838 @cindex @samp{qGetTLSAddr} packet
22839 Fetch the address associated with thread local storage specified
22840 by @var{thread-id}, @var{offset}, and @var{lm}.
22842 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
22843 thread for which to fetch the TLS address.
22845 @var{offset} is the (big endian, hex encoded) offset associated with the
22846 thread local variable. (This offset is obtained from the debug
22847 information associated with the variable.)
22849 @var{lm} is the (big endian, hex encoded) OS/ABI specific encoding of the
22850 the load module associated with the thread local storage. For example,
22851 a @sc{gnu}/Linux system will pass the link map address of the shared
22852 object associated with the thread local storage under consideration.
22853 Other operating environments may choose to represent the load module
22854 differently, so the precise meaning of this parameter will vary.
22858 @item @var{XX}@dots{}
22859 Hex encoded (big endian) bytes representing the address of the thread
22860 local storage requested.
22863 An error occurred. @var{nn} are hex digits.
22866 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
22869 Use of this request packet is controlled by the @code{set remote
22870 get-thread-local-storage-address} command (@pxref{Remote
22871 configuration, set remote get-thread-local-storage-address}).
22873 @item qL @var{startflag} @var{threadcount} @var{nextthread}
22874 Obtain thread information from RTOS. Where: @var{startflag} (one hex
22875 digit) is one to indicate the first query and zero to indicate a
22876 subsequent query; @var{threadcount} (two hex digits) is the maximum
22877 number of threads the response packet can contain; and @var{nextthread}
22878 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
22879 returned in the response as @var{argthread}.
22881 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
22885 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
22886 Where: @var{count} (two hex digits) is the number of threads being
22887 returned; @var{done} (one hex digit) is zero to indicate more threads
22888 and one indicates no further threads; @var{argthreadid} (eight hex
22889 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
22890 is a sequence of thread IDs from the target. @var{threadid} (eight hex
22891 digits). See @code{remote.c:parse_threadlist_response()}.
22895 @cindex section offsets, remote request
22896 @cindex @samp{qOffsets} packet
22897 Get section offsets that the target used when re-locating the downloaded
22898 image. @emph{Note: while a @code{Bss} offset is included in the
22899 response, @value{GDBN} ignores this and instead applies the @code{Data}
22900 offset to the @code{Bss} section.}
22904 @item Text=@var{xxx};Data=@var{yyy};Bss=@var{zzz}
22907 @item qP @var{mode} @var{threadid}
22908 @cindex thread information, remote request
22909 @cindex @samp{qP} packet
22910 Returns information on @var{threadid}. Where: @var{mode} is a hex
22911 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
22913 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
22915 @item qPart:@var{object}:read:@var{annex}:@var{offset},@var{length}
22916 @cindex read special object, remote request
22917 @cindex @samp{qPart} packet
22918 Read uninterpreted bytes from the target's special data area
22919 identified by the keyword @var{object}. Request @var{length} bytes
22920 starting at @var{offset} bytes into the data. The content and
22921 encoding of @var{annex} is specific to the object; it can supply
22922 additional details about what data to access.
22924 Here are the specific requests of this form defined so far. All
22925 @samp{qPart:@var{object}:read:@dots{}} requests use the same reply
22926 formats, listed below.
22929 @item qPart:auxv:read::@var{offset},@var{length}
22930 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
22931 auxiliary vector}, and see @ref{Remote configuration,
22932 read-aux-vector-packet}. Note @var{annex} must be empty.
22938 The @var{offset} in the request is at the end of the data.
22939 There is no more data to be read.
22941 @item @var{XX}@dots{}
22942 Hex encoded data bytes read.
22943 This may be fewer bytes than the @var{length} in the request.
22946 The request was malformed, or @var{annex} was invalid.
22949 The offset was invalid, or there was an error encountered reading the data.
22950 @var{nn} is a hex-encoded @code{errno} value.
22953 An empty reply indicates the @var{object} or @var{annex} string was not
22954 recognized by the stub.
22957 @item qPart:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
22958 @cindex write data into object, remote request
22959 Write uninterpreted bytes into the target's special data area
22960 identified by the keyword @var{object}, starting at @var{offset} bytes
22961 into the data. @samp{@var{data}@dots{}} is the hex-encoded data to be
22962 written. The content and encoding of @var{annex} is specific to the
22963 object; it can supply additional details about what data to access.
22965 No requests of this form are presently in use. This specification
22966 serves as a placeholder to document the common format that new
22967 specific request specifications ought to use.
22972 @var{nn} (hex encoded) is the number of bytes written.
22973 This may be fewer bytes than supplied in the request.
22976 The request was malformed, or @var{annex} was invalid.
22979 The offset was invalid, or there was an error encountered writing the data.
22980 @var{nn} is a hex-encoded @code{errno} value.
22983 An empty reply indicates the @var{object} or @var{annex} string was not
22984 recognized by the stub, or that the object does not support writing.
22987 @item qPart:@var{object}:@var{operation}:@dots{}
22988 Requests of this form may be added in the future. When a stub does
22989 not recognize the @var{object} keyword, or its support for
22990 @var{object} does not recognize the @var{operation} keyword, the stub
22991 must respond with an empty packet.
22993 @item qRcmd,@var{command}
22994 @cindex execute remote command, remote request
22995 @cindex @samp{qRcmd} packet
22996 @var{command} (hex encoded) is passed to the local interpreter for
22997 execution. Invalid commands should be reported using the output
22998 string. Before the final result packet, the target may also respond
22999 with a number of intermediate @samp{O@var{output}} console output
23000 packets. @emph{Implementors should note that providing access to a
23001 stubs's interpreter may have security implications}.
23006 A command response with no output.
23008 A command response with the hex encoded output string @var{OUTPUT}.
23010 Indicate a badly formed request.
23012 An empty reply indicates that @samp{qRcmd} is not recognized.
23016 @cindex symbol lookup, remote request
23017 @cindex @samp{qSymbol} packet
23018 Notify the target that @value{GDBN} is prepared to serve symbol lookup
23019 requests. Accept requests from the target for the values of symbols.
23024 The target does not need to look up any (more) symbols.
23025 @item qSymbol:@var{sym_name}
23026 The target requests the value of symbol @var{sym_name} (hex encoded).
23027 @value{GDBN} may provide the value by using the
23028 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
23032 @item qSymbol:@var{sym_value}:@var{sym_name}
23033 Set the value of @var{sym_name} to @var{sym_value}.
23035 @var{sym_name} (hex encoded) is the name of a symbol whose value the
23036 target has previously requested.
23038 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
23039 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
23045 The target does not need to look up any (more) symbols.
23046 @item qSymbol:@var{sym_name}
23047 The target requests the value of a new symbol @var{sym_name} (hex
23048 encoded). @value{GDBN} will continue to supply the values of symbols
23049 (if available), until the target ceases to request them.
23054 @xref{Tracepoint Packets}.
23056 @item qThreadExtraInfo,@var{id}
23057 @cindex thread attributes info, remote request
23058 @cindex @samp{qThreadExtraInfo} packet
23059 Obtain a printable string description of a thread's attributes from
23060 the target OS. @var{id} is a thread-id in big-endian hex. This
23061 string may contain anything that the target OS thinks is interesting
23062 for @value{GDBN} to tell the user about the thread. The string is
23063 displayed in @value{GDBN}'s @code{info threads} display. Some
23064 examples of possible thread extra info strings are @samp{Runnable}, or
23065 @samp{Blocked on Mutex}.
23069 @item @var{XX}@dots{}
23070 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
23071 comprising the printable string containing the extra information about
23072 the thread's attributes.
23080 @xref{Tracepoint Packets}.
23084 @node Register Packet Format
23085 @section Register Packet Format
23087 The following @code{g}/@code{G} packets have previously been defined.
23088 In the below, some thirty-two bit registers are transferred as
23089 sixty-four bits. Those registers should be zero/sign extended (which?)
23090 to fill the space allocated. Register bytes are transfered in target
23091 byte order. The two nibbles within a register byte are transfered
23092 most-significant - least-significant.
23098 All registers are transfered as thirty-two bit quantities in the order:
23099 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
23100 registers; fsr; fir; fp.
23104 All registers are transfered as sixty-four bit quantities (including
23105 thirty-two bit registers such as @code{sr}). The ordering is the same
23110 @node Tracepoint Packets
23111 @section Tracepoint Packets
23112 @cindex tracepoint packets
23113 @cindex packets, tracepoint
23115 Here we describe the packets @value{GDBN} uses to implement
23116 tracepoints (@pxref{Tracepoints}).
23120 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
23121 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
23122 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
23123 the tracepoint is disabled. @var{step} is the tracepoint's step
23124 count, and @var{pass} is its pass count. If the trailing @samp{-} is
23125 present, further @samp{QTDP} packets will follow to specify this
23126 tracepoint's actions.
23131 The packet was understood and carried out.
23133 The packet was not recognized.
23136 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
23137 Define actions to be taken when a tracepoint is hit. @var{n} and
23138 @var{addr} must be the same as in the initial @samp{QTDP} packet for
23139 this tracepoint. This packet may only be sent immediately after
23140 another @samp{QTDP} packet that ended with a @samp{-}. If the
23141 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
23142 specifying more actions for this tracepoint.
23144 In the series of action packets for a given tracepoint, at most one
23145 can have an @samp{S} before its first @var{action}. If such a packet
23146 is sent, it and the following packets define ``while-stepping''
23147 actions. Any prior packets define ordinary actions --- that is, those
23148 taken when the tracepoint is first hit. If no action packet has an
23149 @samp{S}, then all the packets in the series specify ordinary
23150 tracepoint actions.
23152 The @samp{@var{action}@dots{}} portion of the packet is a series of
23153 actions, concatenated without separators. Each action has one of the
23159 Collect the registers whose bits are set in @var{mask}. @var{mask} is
23160 a hexidecimal number whose @var{i}'th bit is set if register number
23161 @var{i} should be collected. (The least significant bit is numbered
23162 zero.) Note that @var{mask} may be any number of digits long; it may
23163 not fit in a 32-bit word.
23165 @item M @var{basereg},@var{offset},@var{len}
23166 Collect @var{len} bytes of memory starting at the address in register
23167 number @var{basereg}, plus @var{offset}. If @var{basereg} is
23168 @samp{-1}, then the range has a fixed address: @var{offset} is the
23169 address of the lowest byte to collect. The @var{basereg},
23170 @var{offset}, and @var{len} parameters are all unsigned hexidecimal
23171 values (the @samp{-1} value for @var{basereg} is a special case).
23173 @item X @var{len},@var{expr}
23174 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
23175 it directs. @var{expr} is an agent expression, as described in
23176 @ref{Agent Expressions}. Each byte of the expression is encoded as a
23177 two-digit hex number in the packet; @var{len} is the number of bytes
23178 in the expression (and thus one-half the number of hex digits in the
23183 Any number of actions may be packed together in a single @samp{QTDP}
23184 packet, as long as the packet does not exceed the maximum packet
23185 length (400 bytes, for many stubs). There may be only one @samp{R}
23186 action per tracepoint, and it must precede any @samp{M} or @samp{X}
23187 actions. Any registers referred to by @samp{M} and @samp{X} actions
23188 must be collected by a preceding @samp{R} action. (The
23189 ``while-stepping'' actions are treated as if they were attached to a
23190 separate tracepoint, as far as these restrictions are concerned.)
23195 The packet was understood and carried out.
23197 The packet was not recognized.
23200 @item QTFrame:@var{n}
23201 Select the @var{n}'th tracepoint frame from the buffer, and use the
23202 register and memory contents recorded there to answer subsequent
23203 request packets from @value{GDBN}.
23205 A successful reply from the stub indicates that the stub has found the
23206 requested frame. The response is a series of parts, concatenated
23207 without separators, describing the frame we selected. Each part has
23208 one of the following forms:
23212 The selected frame is number @var{n} in the trace frame buffer;
23213 @var{f} is a hexidecimal number. If @var{f} is @samp{-1}, then there
23214 was no frame matching the criteria in the request packet.
23217 The selected trace frame records a hit of tracepoint number @var{t};
23218 @var{t} is a hexidecimal number.
23222 @item QTFrame:pc:@var{addr}
23223 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
23224 currently selected frame whose PC is @var{addr};
23225 @var{addr} is a hexidecimal number.
23227 @item QTFrame:tdp:@var{t}
23228 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
23229 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
23230 is a hexidecimal number.
23232 @item QTFrame:range:@var{start}:@var{end}
23233 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
23234 currently selected frame whose PC is between @var{start} (inclusive)
23235 and @var{end} (exclusive); @var{start} and @var{end} are hexidecimal
23238 @item QTFrame:outside:@var{start}:@var{end}
23239 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
23240 frame @emph{outside} the given range of addresses.
23243 Begin the tracepoint experiment. Begin collecting data from tracepoint
23244 hits in the trace frame buffer.
23247 End the tracepoint experiment. Stop collecting trace frames.
23250 Clear the table of tracepoints, and empty the trace frame buffer.
23252 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
23253 Establish the given ranges of memory as ``transparent''. The stub
23254 will answer requests for these ranges from memory's current contents,
23255 if they were not collected as part of the tracepoint hit.
23257 @value{GDBN} uses this to mark read-only regions of memory, like those
23258 containing program code. Since these areas never change, they should
23259 still have the same contents they did when the tracepoint was hit, so
23260 there's no reason for the stub to refuse to provide their contents.
23263 Ask the stub if there is a trace experiment running right now.
23268 There is no trace experiment running.
23270 There is a trace experiment running.
23277 @section Interrupts
23278 @cindex interrupts (remote protocol)
23280 When a program on the remote target is running, @value{GDBN} may
23281 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
23282 control of which is specified via @value{GDBN}'s @samp{remotebreak}
23283 setting (@pxref{set remotebreak}).
23285 The precise meaning of @code{BREAK} is defined by the transport
23286 mechanism and may, in fact, be undefined. @value{GDBN} does
23287 not currently define a @code{BREAK} mechanism for any of the network
23290 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
23291 transport mechanisms. It is represented by sending the single byte
23292 @code{0x03} without any of the usual packet overhead described in
23293 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
23294 transmitted as part of a packet, it is considered to be packet data
23295 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
23296 (@pxref{X packet}, used for binary downloads, may include an unescaped
23297 @code{0x03} as part of its packet.
23299 Stubs are not required to recognize these interrupt mechanisms and the
23300 precise meaning associated with receipt of the interrupt is
23301 implementation defined. If the stub is successful at interrupting the
23302 running program, it is expected that it will send one of the Stop
23303 Reply Packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
23304 of successfully stopping the program. Interrupts received while the
23305 program is stopped will be discarded.
23310 Example sequence of a target being re-started. Notice how the restart
23311 does not get any direct output:
23316 @emph{target restarts}
23319 <- @code{T001:1234123412341234}
23323 Example sequence of a target being stepped by a single instruction:
23326 -> @code{G1445@dots{}}
23331 <- @code{T001:1234123412341234}
23335 <- @code{1455@dots{}}
23339 @node File-I/O remote protocol extension
23340 @section File-I/O remote protocol extension
23341 @cindex File-I/O remote protocol extension
23344 * File-I/O Overview::
23345 * Protocol basics::
23346 * The F request packet::
23347 * The F reply packet::
23348 * Memory transfer::
23349 * The Ctrl-C message::
23351 * The isatty call::
23352 * The system call::
23353 * List of supported calls::
23354 * Protocol specific representation of datatypes::
23356 * File-I/O Examples::
23359 @node File-I/O Overview
23360 @subsection File-I/O Overview
23361 @cindex file-i/o overview
23363 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
23364 target to use the host's file system and console I/O when calling various
23365 system calls. System calls on the target system are translated into a
23366 remote protocol packet to the host system which then performs the needed
23367 actions and returns with an adequate response packet to the target system.
23368 This simulates file system operations even on targets that lack file systems.
23370 The protocol is defined host- and target-system independent. It uses
23371 its own independent representation of datatypes and values. Both,
23372 @value{GDBN} and the target's @value{GDBN} stub are responsible for
23373 translating the system dependent values into the unified protocol values
23374 when data is transmitted.
23376 The communication is synchronous. A system call is possible only
23377 when GDB is waiting for the @samp{C}, @samp{c}, @samp{S} or @samp{s}
23378 packets. While @value{GDBN} handles the request for a system call,
23379 the target is stopped to allow deterministic access to the target's
23380 memory. Therefore File-I/O is not interuptible by target signals. It
23381 is possible to interrupt File-I/O by a user interrupt (Ctrl-C), though.
23383 The target's request to perform a host system call does not finish
23384 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
23385 after finishing the system call, the target returns to continuing the
23386 previous activity (continue, step). No additional continue or step
23387 request from @value{GDBN} is required.
23390 (@value{GDBP}) continue
23391 <- target requests 'system call X'
23392 target is stopped, @value{GDBN} executes system call
23393 -> GDB returns result
23394 ... target continues, GDB returns to wait for the target
23395 <- target hits breakpoint and sends a Txx packet
23398 The protocol is only used for files on the host file system and
23399 for I/O on the console. Character or block special devices, pipes,
23400 named pipes or sockets or any other communication method on the host
23401 system are not supported by this protocol.
23403 @node Protocol basics
23404 @subsection Protocol basics
23405 @cindex protocol basics, file-i/o
23407 The File-I/O protocol uses the @code{F} packet, as request as well
23408 as as reply packet. Since a File-I/O system call can only occur when
23409 @value{GDBN} is waiting for the continuing or stepping target, the
23410 File-I/O request is a reply that @value{GDBN} has to expect as a result
23411 of a former @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
23412 This @code{F} packet contains all information needed to allow @value{GDBN}
23413 to call the appropriate host system call:
23417 A unique identifier for the requested system call.
23420 All parameters to the system call. Pointers are given as addresses
23421 in the target memory address space. Pointers to strings are given as
23422 pointer/length pair. Numerical values are given as they are.
23423 Numerical control values are given in a protocol specific representation.
23427 At that point @value{GDBN} has to perform the following actions.
23431 If parameter pointer values are given, which point to data needed as input
23432 to a system call, @value{GDBN} requests this data from the target with a
23433 standard @code{m} packet request. This additional communication has to be
23434 expected by the target implementation and is handled as any other @code{m}
23438 @value{GDBN} translates all value from protocol representation to host
23439 representation as needed. Datatypes are coerced into the host types.
23442 @value{GDBN} calls the system call
23445 It then coerces datatypes back to protocol representation.
23448 If pointer parameters in the request packet point to buffer space in which
23449 a system call is expected to copy data to, the data is transmitted to the
23450 target using a @code{M} or @code{X} packet. This packet has to be expected
23451 by the target implementation and is handled as any other @code{M} or @code{X}
23456 Eventually @value{GDBN} replies with another @code{F} packet which contains all
23457 necessary information for the target to continue. This at least contains
23464 @code{errno}, if has been changed by the system call.
23471 After having done the needed type and value coercion, the target continues
23472 the latest continue or step action.
23474 @node The F request packet
23475 @subsection The @code{F} request packet
23476 @cindex file-i/o request packet
23477 @cindex @code{F} request packet
23479 The @code{F} request packet has the following format:
23484 @code{F}@var{call-id}@code{,}@var{parameter@dots{}}
23487 @var{call-id} is the identifier to indicate the host system call to be called.
23488 This is just the name of the function.
23490 @var{parameter@dots{}} are the parameters to the system call.
23494 Parameters are hexadecimal integer values, either the real values in case
23495 of scalar datatypes, as pointers to target buffer space in case of compound
23496 datatypes and unspecified memory areas or as pointer/length pairs in case
23497 of string parameters. These are appended to the call-id, each separated
23498 from its predecessor by a comma. All values are transmitted in ASCII
23499 string representation, pointer/length pairs separated by a slash.
23501 @node The F reply packet
23502 @subsection The @code{F} reply packet
23503 @cindex file-i/o reply packet
23504 @cindex @code{F} reply packet
23506 The @code{F} reply packet has the following format:
23511 @code{F}@var{retcode}@code{,}@var{errno}@code{,}@var{Ctrl-C flag}@code{;}@var{call specific attachment}
23514 @var{retcode} is the return code of the system call as hexadecimal value.
23516 @var{errno} is the errno set by the call, in protocol specific representation.
23517 This parameter can be omitted if the call was successful.
23519 @var{Ctrl-C flag} is only send if the user requested a break. In this
23520 case, @var{errno} must be send as well, even if the call was successful.
23521 The @var{Ctrl-C flag} itself consists of the character 'C':
23528 or, if the call was interupted before the host call has been performed:
23535 assuming 4 is the protocol specific representation of @code{EINTR}.
23539 @node Memory transfer
23540 @subsection Memory transfer
23541 @cindex memory transfer, in file-i/o protocol
23543 Structured data which is transferred using a memory read or write as e.g.@:
23544 a @code{struct stat} is expected to be in a protocol specific format with
23545 all scalar multibyte datatypes being big endian. This should be done by
23546 the target before the @code{F} packet is sent resp.@: by @value{GDBN} before
23547 it transfers memory to the target. Transferred pointers to structured
23548 data should point to the already coerced data at any time.
23550 @node The Ctrl-C message
23551 @subsection The Ctrl-C message
23552 @cindex ctrl-c message, in file-i/o protocol
23554 A special case is, if the @var{Ctrl-C flag} is set in the @value{GDBN}
23555 reply packet. In this case the target should behave, as if it had
23556 gotten a break message. The meaning for the target is ``system call
23557 interupted by @code{SIGINT}''. Consequentially, the target should actually stop
23558 (as with a break message) and return to @value{GDBN} with a @code{T02}
23559 packet. In this case, it's important for the target to know, in which
23560 state the system call was interrupted. Since this action is by design
23561 not an atomic operation, we have to differ between two cases:
23565 The system call hasn't been performed on the host yet.
23568 The system call on the host has been finished.
23572 These two states can be distinguished by the target by the value of the
23573 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
23574 call hasn't been performed. This is equivalent to the @code{EINTR} handling
23575 on POSIX systems. In any other case, the target may presume that the
23576 system call has been finished --- successful or not --- and should behave
23577 as if the break message arrived right after the system call.
23579 @value{GDBN} must behave reliable. If the system call has not been called
23580 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
23581 @code{errno} in the packet. If the system call on the host has been finished
23582 before the user requests a break, the full action must be finshed by
23583 @value{GDBN}. This requires sending @code{M} or @code{X} packets as they fit.
23584 The @code{F} packet may only be send when either nothing has happened
23585 or the full action has been completed.
23588 @subsection Console I/O
23589 @cindex console i/o as part of file-i/o
23591 By default and if not explicitely closed by the target system, the file
23592 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
23593 on the @value{GDBN} console is handled as any other file output operation
23594 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
23595 by @value{GDBN} so that after the target read request from file descriptor
23596 0 all following typing is buffered until either one of the following
23601 The user presses @kbd{Ctrl-C}. The behaviour is as explained above, the
23603 system call is treated as finished.
23606 The user presses @kbd{Enter}. This is treated as end of input with a trailing
23610 The user presses @kbd{Ctrl-D}. This is treated as end of input. No trailing
23611 character, especially no Ctrl-D is appended to the input.
23615 If the user has typed more characters as fit in the buffer given to
23616 the read call, the trailing characters are buffered in @value{GDBN} until
23617 either another @code{read(0, @dots{})} is requested by the target or debugging
23618 is stopped on users request.
23620 @node The isatty call
23621 @subsection The @samp{isatty} function call
23622 @cindex isatty call, file-i/o protocol
23624 A special case in this protocol is the library call @code{isatty} which
23625 is implemented as its own call inside of this protocol. It returns
23626 1 to the target if the file descriptor given as parameter is attached
23627 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
23628 would require implementing @code{ioctl} and would be more complex than
23631 @node The system call
23632 @subsection The @samp{system} function call
23633 @cindex system call, file-i/o protocol
23635 The other special case in this protocol is the @code{system} call which
23636 is implemented as its own call, too. @value{GDBN} is taking over the full
23637 task of calling the necessary host calls to perform the @code{system}
23638 call. The return value of @code{system} is simplified before it's returned
23639 to the target. Basically, the only signal transmitted back is @code{EINTR}
23640 in case the user pressed @kbd{Ctrl-C}. Otherwise the return value consists
23641 entirely of the exit status of the called command.
23643 Due to security concerns, the @code{system} call is by default refused
23644 by @value{GDBN}. The user has to allow this call explicitly with the
23645 @kbd{set remote system-call-allowed 1} command.
23648 @item set remote system-call-allowed
23649 @kindex set remote system-call-allowed
23650 Control whether to allow the @code{system} calls in the File I/O
23651 protocol for the remote target. The default is zero (disabled).
23653 @item show remote system-call-allowed
23654 @kindex show remote system-call-allowed
23655 Show the current setting of system calls for the remote File I/O
23659 @node List of supported calls
23660 @subsection List of supported calls
23661 @cindex list of supported file-i/o calls
23678 @unnumberedsubsubsec open
23679 @cindex open, file-i/o system call
23683 int open(const char *pathname, int flags);
23684 int open(const char *pathname, int flags, mode_t mode);
23687 Fopen,pathptr/len,flags,mode
23691 @code{flags} is the bitwise or of the following values:
23695 If the file does not exist it will be created. The host
23696 rules apply as far as file ownership and time stamps
23700 When used with O_CREAT, if the file already exists it is
23701 an error and open() fails.
23704 If the file already exists and the open mode allows
23705 writing (O_RDWR or O_WRONLY is given) it will be
23706 truncated to length 0.
23709 The file is opened in append mode.
23712 The file is opened for reading only.
23715 The file is opened for writing only.
23718 The file is opened for reading and writing.
23721 Each other bit is silently ignored.
23726 @code{mode} is the bitwise or of the following values:
23730 User has read permission.
23733 User has write permission.
23736 Group has read permission.
23739 Group has write permission.
23742 Others have read permission.
23745 Others have write permission.
23748 Each other bit is silently ignored.
23753 @exdent Return value:
23754 open returns the new file descriptor or -1 if an error
23762 pathname already exists and O_CREAT and O_EXCL were used.
23765 pathname refers to a directory.
23768 The requested access is not allowed.
23771 pathname was too long.
23774 A directory component in pathname does not exist.
23777 pathname refers to a device, pipe, named pipe or socket.
23780 pathname refers to a file on a read-only filesystem and
23781 write access was requested.
23784 pathname is an invalid pointer value.
23787 No space on device to create the file.
23790 The process already has the maximum number of files open.
23793 The limit on the total number of files open on the system
23797 The call was interrupted by the user.
23801 @unnumberedsubsubsec close
23802 @cindex close, file-i/o system call
23811 @exdent Return value:
23812 close returns zero on success, or -1 if an error occurred.
23819 fd isn't a valid open file descriptor.
23822 The call was interrupted by the user.
23826 @unnumberedsubsubsec read
23827 @cindex read, file-i/o system call
23831 int read(int fd, void *buf, unsigned int count);
23834 Fread,fd,bufptr,count
23836 @exdent Return value:
23837 On success, the number of bytes read is returned.
23838 Zero indicates end of file. If count is zero, read
23839 returns zero as well. On error, -1 is returned.
23846 fd is not a valid file descriptor or is not open for
23850 buf is an invalid pointer value.
23853 The call was interrupted by the user.
23857 @unnumberedsubsubsec write
23858 @cindex write, file-i/o system call
23862 int write(int fd, const void *buf, unsigned int count);
23865 Fwrite,fd,bufptr,count
23867 @exdent Return value:
23868 On success, the number of bytes written are returned.
23869 Zero indicates nothing was written. On error, -1
23877 fd is not a valid file descriptor or is not open for
23881 buf is an invalid pointer value.
23884 An attempt was made to write a file that exceeds the
23885 host specific maximum file size allowed.
23888 No space on device to write the data.
23891 The call was interrupted by the user.
23895 @unnumberedsubsubsec lseek
23896 @cindex lseek, file-i/o system call
23900 long lseek (int fd, long offset, int flag);
23903 Flseek,fd,offset,flag
23906 @code{flag} is one of:
23910 The offset is set to offset bytes.
23913 The offset is set to its current location plus offset
23917 The offset is set to the size of the file plus offset
23922 @exdent Return value:
23923 On success, the resulting unsigned offset in bytes from
23924 the beginning of the file is returned. Otherwise, a
23925 value of -1 is returned.
23932 fd is not a valid open file descriptor.
23935 fd is associated with the @value{GDBN} console.
23938 flag is not a proper value.
23941 The call was interrupted by the user.
23945 @unnumberedsubsubsec rename
23946 @cindex rename, file-i/o system call
23950 int rename(const char *oldpath, const char *newpath);
23953 Frename,oldpathptr/len,newpathptr/len
23955 @exdent Return value:
23956 On success, zero is returned. On error, -1 is returned.
23963 newpath is an existing directory, but oldpath is not a
23967 newpath is a non-empty directory.
23970 oldpath or newpath is a directory that is in use by some
23974 An attempt was made to make a directory a subdirectory
23978 A component used as a directory in oldpath or new
23979 path is not a directory. Or oldpath is a directory
23980 and newpath exists but is not a directory.
23983 oldpathptr or newpathptr are invalid pointer values.
23986 No access to the file or the path of the file.
23990 oldpath or newpath was too long.
23993 A directory component in oldpath or newpath does not exist.
23996 The file is on a read-only filesystem.
23999 The device containing the file has no room for the new
24003 The call was interrupted by the user.
24007 @unnumberedsubsubsec unlink
24008 @cindex unlink, file-i/o system call
24012 int unlink(const char *pathname);
24015 Funlink,pathnameptr/len
24017 @exdent Return value:
24018 On success, zero is returned. On error, -1 is returned.
24025 No access to the file or the path of the file.
24028 The system does not allow unlinking of directories.
24031 The file pathname cannot be unlinked because it's
24032 being used by another process.
24035 pathnameptr is an invalid pointer value.
24038 pathname was too long.
24041 A directory component in pathname does not exist.
24044 A component of the path is not a directory.
24047 The file is on a read-only filesystem.
24050 The call was interrupted by the user.
24054 @unnumberedsubsubsec stat/fstat
24055 @cindex fstat, file-i/o system call
24056 @cindex stat, file-i/o system call
24060 int stat(const char *pathname, struct stat *buf);
24061 int fstat(int fd, struct stat *buf);
24064 Fstat,pathnameptr/len,bufptr
24067 @exdent Return value:
24068 On success, zero is returned. On error, -1 is returned.
24075 fd is not a valid open file.
24078 A directory component in pathname does not exist or the
24079 path is an empty string.
24082 A component of the path is not a directory.
24085 pathnameptr is an invalid pointer value.
24088 No access to the file or the path of the file.
24091 pathname was too long.
24094 The call was interrupted by the user.
24098 @unnumberedsubsubsec gettimeofday
24099 @cindex gettimeofday, file-i/o system call
24103 int gettimeofday(struct timeval *tv, void *tz);
24106 Fgettimeofday,tvptr,tzptr
24108 @exdent Return value:
24109 On success, 0 is returned, -1 otherwise.
24116 tz is a non-NULL pointer.
24119 tvptr and/or tzptr is an invalid pointer value.
24123 @unnumberedsubsubsec isatty
24124 @cindex isatty, file-i/o system call
24128 int isatty(int fd);
24133 @exdent Return value:
24134 Returns 1 if fd refers to the @value{GDBN} console, 0 otherwise.
24141 The call was interrupted by the user.
24145 @unnumberedsubsubsec system
24146 @cindex system, file-i/o system call
24150 int system(const char *command);
24153 Fsystem,commandptr/len
24155 @exdent Return value:
24156 The value returned is -1 on error and the return status
24157 of the command otherwise. Only the exit status of the
24158 command is returned, which is extracted from the hosts
24159 system return value by calling WEXITSTATUS(retval).
24160 In case /bin/sh could not be executed, 127 is returned.
24167 The call was interrupted by the user.
24170 @node Protocol specific representation of datatypes
24171 @subsection Protocol specific representation of datatypes
24172 @cindex protocol specific representation of datatypes, in file-i/o protocol
24175 * Integral datatypes::
24181 @node Integral datatypes
24182 @unnumberedsubsubsec Integral datatypes
24183 @cindex integral datatypes, in file-i/o protocol
24185 The integral datatypes used in the system calls are
24188 int@r{,} unsigned int@r{,} long@r{,} unsigned long@r{,} mode_t @r{and} time_t
24191 @code{Int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
24192 implemented as 32 bit values in this protocol.
24194 @code{Long} and @code{unsigned long} are implemented as 64 bit types.
24196 @xref{Limits}, for corresponding MIN and MAX values (similar to those
24197 in @file{limits.h}) to allow range checking on host and target.
24199 @code{time_t} datatypes are defined as seconds since the Epoch.
24201 All integral datatypes transferred as part of a memory read or write of a
24202 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
24205 @node Pointer values
24206 @unnumberedsubsubsec Pointer values
24207 @cindex pointer values, in file-i/o protocol
24209 Pointers to target data are transmitted as they are. An exception
24210 is made for pointers to buffers for which the length isn't
24211 transmitted as part of the function call, namely strings. Strings
24212 are transmitted as a pointer/length pair, both as hex values, e.g.@:
24219 which is a pointer to data of length 18 bytes at position 0x1aaf.
24220 The length is defined as the full string length in bytes, including
24221 the trailing null byte. Example:
24224 ``hello, world'' at address 0x123456
24235 @unnumberedsubsubsec struct stat
24236 @cindex struct stat, in file-i/o protocol
24238 The buffer of type struct stat used by the target and @value{GDBN} is defined
24243 unsigned int st_dev; /* device */
24244 unsigned int st_ino; /* inode */
24245 mode_t st_mode; /* protection */
24246 unsigned int st_nlink; /* number of hard links */
24247 unsigned int st_uid; /* user ID of owner */
24248 unsigned int st_gid; /* group ID of owner */
24249 unsigned int st_rdev; /* device type (if inode device) */
24250 unsigned long st_size; /* total size, in bytes */
24251 unsigned long st_blksize; /* blocksize for filesystem I/O */
24252 unsigned long st_blocks; /* number of blocks allocated */
24253 time_t st_atime; /* time of last access */
24254 time_t st_mtime; /* time of last modification */
24255 time_t st_ctime; /* time of last change */
24259 The integral datatypes are conforming to the definitions given in the
24260 approriate section (see @ref{Integral datatypes}, for details) so this
24261 structure is of size 64 bytes.
24263 The values of several fields have a restricted meaning and/or
24270 st_ino: No valid meaning for the target. Transmitted unchanged.
24272 st_mode: Valid mode bits are described in Appendix C. Any other
24273 bits have currently no meaning for the target.
24275 st_uid: No valid meaning for the target. Transmitted unchanged.
24277 st_gid: No valid meaning for the target. Transmitted unchanged.
24279 st_rdev: No valid meaning for the target. Transmitted unchanged.
24281 st_atime, st_mtime, st_ctime:
24282 These values have a host and file system dependent
24283 accuracy. Especially on Windows hosts the file systems
24284 don't support exact timing values.
24287 The target gets a struct stat of the above representation and is
24288 responsible to coerce it to the target representation before
24291 Note that due to size differences between the host and target
24292 representation of stat members, these members could eventually
24293 get truncated on the target.
24295 @node struct timeval
24296 @unnumberedsubsubsec struct timeval
24297 @cindex struct timeval, in file-i/o protocol
24299 The buffer of type struct timeval used by the target and @value{GDBN}
24300 is defined as follows:
24304 time_t tv_sec; /* second */
24305 long tv_usec; /* microsecond */
24309 The integral datatypes are conforming to the definitions given in the
24310 approriate section (see @ref{Integral datatypes}, for details) so this
24311 structure is of size 8 bytes.
24314 @subsection Constants
24315 @cindex constants, in file-i/o protocol
24317 The following values are used for the constants inside of the
24318 protocol. @value{GDBN} and target are resposible to translate these
24319 values before and after the call as needed.
24330 @unnumberedsubsubsec Open flags
24331 @cindex open flags, in file-i/o protocol
24333 All values are given in hexadecimal representation.
24345 @node mode_t values
24346 @unnumberedsubsubsec mode_t values
24347 @cindex mode_t values, in file-i/o protocol
24349 All values are given in octal representation.
24366 @unnumberedsubsubsec Errno values
24367 @cindex errno values, in file-i/o protocol
24369 All values are given in decimal representation.
24394 EUNKNOWN is used as a fallback error value if a host system returns
24395 any error value not in the list of supported error numbers.
24398 @unnumberedsubsubsec Lseek flags
24399 @cindex lseek flags, in file-i/o protocol
24408 @unnumberedsubsubsec Limits
24409 @cindex limits, in file-i/o protocol
24411 All values are given in decimal representation.
24414 INT_MIN -2147483648
24416 UINT_MAX 4294967295
24417 LONG_MIN -9223372036854775808
24418 LONG_MAX 9223372036854775807
24419 ULONG_MAX 18446744073709551615
24422 @node File-I/O Examples
24423 @subsection File-I/O Examples
24424 @cindex file-i/o examples
24426 Example sequence of a write call, file descriptor 3, buffer is at target
24427 address 0x1234, 6 bytes should be written:
24430 <- @code{Fwrite,3,1234,6}
24431 @emph{request memory read from target}
24434 @emph{return "6 bytes written"}
24438 Example sequence of a read call, file descriptor 3, buffer is at target
24439 address 0x1234, 6 bytes should be read:
24442 <- @code{Fread,3,1234,6}
24443 @emph{request memory write to target}
24444 -> @code{X1234,6:XXXXXX}
24445 @emph{return "6 bytes read"}
24449 Example sequence of a read call, call fails on the host due to invalid
24450 file descriptor (EBADF):
24453 <- @code{Fread,3,1234,6}
24457 Example sequence of a read call, user presses Ctrl-C before syscall on
24461 <- @code{Fread,3,1234,6}
24466 Example sequence of a read call, user presses Ctrl-C after syscall on
24470 <- @code{Fread,3,1234,6}
24471 -> @code{X1234,6:XXXXXX}
24475 @include agentexpr.texi
24489 % I think something like @colophon should be in texinfo. In the
24491 \long\def\colophon{\hbox to0pt{}\vfill
24492 \centerline{The body of this manual is set in}
24493 \centerline{\fontname\tenrm,}
24494 \centerline{with headings in {\bf\fontname\tenbf}}
24495 \centerline{and examples in {\tt\fontname\tentt}.}
24496 \centerline{{\it\fontname\tenit\/},}
24497 \centerline{{\bf\fontname\tenbf}, and}
24498 \centerline{{\sl\fontname\tensl\/}}
24499 \centerline{are used for emphasis.}\vfill}
24501 % Blame: doc@cygnus.com, 1991.