1 \input texinfo @c -*-texinfo-*-
2 @c Copyright 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
3 @c 1999, 2000, 2001, 2002, 2003, 2004
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 Free Software Foundation, Inc.
57 Permission is granted to copy, distribute and/or modify this document
58 under the terms of the GNU Free Documentation License, Version 1.1 or
59 any later version published by the Free Software Foundation; with the
60 Invariant Sections being ``Free Software'' and ``Free Software Needs
61 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
62 and with the Back-Cover Texts as in (a) below.
64 (a) The Free Software Foundation's Back-Cover Text is: ``You have
65 freedom to copy and modify this GNU Manual, like GNU software. Copies
66 published by the Free Software Foundation raise funds for GNU
71 @title Debugging with @value{GDBN}
72 @subtitle The @sc{gnu} Source-Level Debugger
74 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
75 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
79 \hfill (Send bugs and comments on @value{GDBN} to bug-gdb\@gnu.org.)\par
80 \hfill {\it Debugging with @value{GDBN}}\par
81 \hfill \TeX{}info \texinfoversion\par
85 @vskip 0pt plus 1filll
86 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
87 1996, 1998, 1999, 2000, 2001, 2002, 2003, 2004 Free Software Foundation, Inc.
89 Published by the Free Software Foundation @*
90 59 Temple Place - Suite 330, @*
91 Boston, MA 02111-1307 USA @*
94 Permission is granted to copy, distribute and/or modify this document
95 under the terms of the GNU Free Documentation License, Version 1.1 or
96 any later version published by the Free Software Foundation; with the
97 Invariant Sections being ``Free Software'' and ``Free Software Needs
98 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
99 and with the Back-Cover Texts as in (a) below.
101 (a) The Free Software Foundation's Back-Cover Text is: ``You have
102 freedom to copy and modify this GNU Manual, like GNU software. Copies
103 published by the Free Software Foundation raise funds for GNU
109 @node Top, Summary, (dir), (dir)
111 @top Debugging with @value{GDBN}
113 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
115 This is the @value{EDITION} Edition, for @value{GDBN} Version
118 Copyright (C) 1988-2004 Free Software Foundation, Inc.
121 * Summary:: Summary of @value{GDBN}
122 * Sample Session:: A sample @value{GDBN} session
124 * Invocation:: Getting in and out of @value{GDBN}
125 * Commands:: @value{GDBN} commands
126 * Running:: Running programs under @value{GDBN}
127 * Stopping:: Stopping and continuing
128 * Stack:: Examining the stack
129 * Source:: Examining source files
130 * Data:: Examining data
131 * Macros:: Preprocessor Macros
132 * Tracepoints:: Debugging remote targets non-intrusively
133 * Overlays:: Debugging programs that use overlays
135 * Languages:: Using @value{GDBN} with different languages
137 * Symbols:: Examining the symbol table
138 * Altering:: Altering execution
139 * GDB Files:: @value{GDBN} files
140 * Targets:: Specifying a debugging target
141 * Remote Debugging:: Debugging remote programs
142 * Configurations:: Configuration-specific information
143 * Controlling GDB:: Controlling @value{GDBN}
144 * Sequences:: Canned sequences of commands
145 * TUI:: @value{GDBN} Text User Interface
146 * Interpreters:: Command Interpreters
147 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
148 * Annotations:: @value{GDBN}'s annotation interface.
149 * GDB/MI:: @value{GDBN}'s Machine Interface.
151 * GDB Bugs:: Reporting bugs in @value{GDBN}
152 * Formatting Documentation:: How to format and print @value{GDBN} documentation
154 * Command Line Editing:: Command Line Editing
155 * Using History Interactively:: Using History Interactively
156 * Installing GDB:: Installing GDB
157 * Maintenance Commands:: Maintenance Commands
158 * Remote Protocol:: GDB Remote Serial Protocol
159 * Agent Expressions:: The GDB Agent Expression Mechanism
160 * Copying:: GNU General Public License says
161 how you can copy and share GDB
162 * GNU Free Documentation License:: The license for this documentation
171 @unnumbered Summary of @value{GDBN}
173 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
174 going on ``inside'' another program while it executes---or what another
175 program was doing at the moment it crashed.
177 @value{GDBN} can do four main kinds of things (plus other things in support of
178 these) to help you catch bugs in the act:
182 Start your program, specifying anything that might affect its behavior.
185 Make your program stop on specified conditions.
188 Examine what has happened, when your program has stopped.
191 Change things in your program, so you can experiment with correcting the
192 effects of one bug and go on to learn about another.
195 You can use @value{GDBN} to debug programs written in C and C@t{++}.
196 For more information, see @ref{Support,,Supported languages}.
197 For more information, see @ref{C,,C and C++}.
200 Support for Modula-2 is partial. For information on Modula-2, see
201 @ref{Modula-2,,Modula-2}.
204 Debugging Pascal programs which use sets, subranges, file variables, or
205 nested functions does not currently work. @value{GDBN} does not support
206 entering expressions, printing values, or similar features using Pascal
210 @value{GDBN} can be used to debug programs written in Fortran, although
211 it may be necessary to refer to some variables with a trailing
214 @value{GDBN} can be used to debug programs written in Objective-C,
215 using either the Apple/NeXT or the GNU Objective-C runtime.
218 * Free Software:: Freely redistributable software
219 * Contributors:: Contributors to GDB
223 @unnumberedsec Free software
225 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
226 General Public License
227 (GPL). The GPL gives you the freedom to copy or adapt a licensed
228 program---but every person getting a copy also gets with it the
229 freedom to modify that copy (which means that they must get access to
230 the source code), and the freedom to distribute further copies.
231 Typical software companies use copyrights to limit your freedoms; the
232 Free Software Foundation uses the GPL to preserve these freedoms.
234 Fundamentally, the General Public License is a license which says that
235 you have these freedoms and that you cannot take these freedoms away
238 @unnumberedsec Free Software Needs Free Documentation
240 The biggest deficiency in the free software community today is not in
241 the software---it is the lack of good free documentation that we can
242 include with the free software. Many of our most important
243 programs do not come with free reference manuals and free introductory
244 texts. Documentation is an essential part of any software package;
245 when an important free software package does not come with a free
246 manual and a free tutorial, that is a major gap. We have many such
249 Consider Perl, for instance. The tutorial manuals that people
250 normally use are non-free. How did this come about? Because the
251 authors of those manuals published them with restrictive terms---no
252 copying, no modification, source files not available---which exclude
253 them from the free software world.
255 That wasn't the first time this sort of thing happened, and it was far
256 from the last. Many times we have heard a GNU user eagerly describe a
257 manual that he is writing, his intended contribution to the community,
258 only to learn that he had ruined everything by signing a publication
259 contract to make it non-free.
261 Free documentation, like free software, is a matter of freedom, not
262 price. The problem with the non-free manual is not that publishers
263 charge a price for printed copies---that in itself is fine. (The Free
264 Software Foundation sells printed copies of manuals, too.) The
265 problem is the restrictions on the use of the manual. Free manuals
266 are available in source code form, and give you permission to copy and
267 modify. Non-free manuals do not allow this.
269 The criteria of freedom for a free manual are roughly the same as for
270 free software. Redistribution (including the normal kinds of
271 commercial redistribution) must be permitted, so that the manual can
272 accompany every copy of the program, both on-line and on paper.
274 Permission for modification of the technical content is crucial too.
275 When people modify the software, adding or changing features, if they
276 are conscientious they will change the manual too---so they can
277 provide accurate and clear documentation for the modified program. A
278 manual that leaves you no choice but to write a new manual to document
279 a changed version of the program is not really available to our
282 Some kinds of limits on the way modification is handled are
283 acceptable. For example, requirements to preserve the original
284 author's copyright notice, the distribution terms, or the list of
285 authors, are ok. It is also no problem to require modified versions
286 to include notice that they were modified. Even entire sections that
287 may not be deleted or changed are acceptable, as long as they deal
288 with nontechnical topics (like this one). These kinds of restrictions
289 are acceptable because they don't obstruct the community's normal use
292 However, it must be possible to modify all the @emph{technical}
293 content of the manual, and then distribute the result in all the usual
294 media, through all the usual channels. Otherwise, the restrictions
295 obstruct the use of the manual, it is not free, and we need another
296 manual to replace it.
298 Please spread the word about this issue. Our community continues to
299 lose manuals to proprietary publishing. If we spread the word that
300 free software needs free reference manuals and free tutorials, perhaps
301 the next person who wants to contribute by writing documentation will
302 realize, before it is too late, that only free manuals contribute to
303 the free software community.
305 If you are writing documentation, please insist on publishing it under
306 the GNU Free Documentation License or another free documentation
307 license. Remember that this decision requires your approval---you
308 don't have to let the publisher decide. Some commercial publishers
309 will use a free license if you insist, but they will not propose the
310 option; it is up to you to raise the issue and say firmly that this is
311 what you want. If the publisher you are dealing with refuses, please
312 try other publishers. If you're not sure whether a proposed license
313 is free, write to @email{licensing@@gnu.org}.
315 You can encourage commercial publishers to sell more free, copylefted
316 manuals and tutorials by buying them, and particularly by buying
317 copies from the publishers that paid for their writing or for major
318 improvements. Meanwhile, try to avoid buying non-free documentation
319 at all. Check the distribution terms of a manual before you buy it,
320 and insist that whoever seeks your business must respect your freedom.
321 Check the history of the book, and try to reward the publishers that
322 have paid or pay the authors to work on it.
324 The Free Software Foundation maintains a list of free documentation
325 published by other publishers, at
326 @url{http://www.fsf.org/doc/other-free-books.html}.
329 @unnumberedsec Contributors to @value{GDBN}
331 Richard Stallman was the original author of @value{GDBN}, and of many
332 other @sc{gnu} programs. Many others have contributed to its
333 development. This section attempts to credit major contributors. One
334 of the virtues of free software is that everyone is free to contribute
335 to it; with regret, we cannot actually acknowledge everyone here. The
336 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
337 blow-by-blow account.
339 Changes much prior to version 2.0 are lost in the mists of time.
342 @emph{Plea:} Additions to this section are particularly welcome. If you
343 or your friends (or enemies, to be evenhanded) have been unfairly
344 omitted from this list, we would like to add your names!
347 So that they may not regard their many labors as thankless, we
348 particularly thank those who shepherded @value{GDBN} through major
350 Andrew Cagney (releases 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
351 Jim Blandy (release 4.18);
352 Jason Molenda (release 4.17);
353 Stan Shebs (release 4.14);
354 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
355 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
356 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
357 Jim Kingdon (releases 3.5, 3.4, and 3.3);
358 and Randy Smith (releases 3.2, 3.1, and 3.0).
360 Richard Stallman, assisted at various times by Peter TerMaat, Chris
361 Hanson, and Richard Mlynarik, handled releases through 2.8.
363 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
364 in @value{GDBN}, with significant additional contributions from Per
365 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
366 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
367 much general update work leading to release 3.0).
369 @value{GDBN} uses the BFD subroutine library to examine multiple
370 object-file formats; BFD was a joint project of David V.
371 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
373 David Johnson wrote the original COFF support; Pace Willison did
374 the original support for encapsulated COFF.
376 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
378 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
379 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
381 Jean-Daniel Fekete contributed Sun 386i support.
382 Chris Hanson improved the HP9000 support.
383 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
384 David Johnson contributed Encore Umax support.
385 Jyrki Kuoppala contributed Altos 3068 support.
386 Jeff Law contributed HP PA and SOM support.
387 Keith Packard contributed NS32K support.
388 Doug Rabson contributed Acorn Risc Machine support.
389 Bob Rusk contributed Harris Nighthawk CX-UX support.
390 Chris Smith contributed Convex support (and Fortran debugging).
391 Jonathan Stone contributed Pyramid support.
392 Michael Tiemann contributed SPARC support.
393 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
394 Pace Willison contributed Intel 386 support.
395 Jay Vosburgh contributed Symmetry support.
396 Marko Mlinar contributed OpenRISC 1000 support.
398 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
400 Rich Schaefer and Peter Schauer helped with support of SunOS shared
403 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
404 about several machine instruction sets.
406 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
407 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
408 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
409 and RDI targets, respectively.
411 Brian Fox is the author of the readline libraries providing
412 command-line editing and command history.
414 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
415 Modula-2 support, and contributed the Languages chapter of this manual.
417 Fred Fish wrote most of the support for Unix System Vr4.
418 He also enhanced the command-completion support to cover C@t{++} overloaded
421 Hitachi America (now Renesas America), Ltd. sponsored the support for
422 H8/300, H8/500, and Super-H processors.
424 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
426 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
429 Toshiba sponsored the support for the TX39 Mips processor.
431 Matsushita sponsored the support for the MN10200 and MN10300 processors.
433 Fujitsu sponsored the support for SPARClite and FR30 processors.
435 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
438 Michael Snyder added support for tracepoints.
440 Stu Grossman wrote gdbserver.
442 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
443 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
445 The following people at the Hewlett-Packard Company contributed
446 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
447 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
448 compiler, and the Text User Interface (nee Terminal User Interface):
449 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
450 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
451 provided HP-specific information in this manual.
453 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
454 Robert Hoehne made significant contributions to the DJGPP port.
456 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
457 development since 1991. Cygnus engineers who have worked on @value{GDBN}
458 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
459 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
460 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
461 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
462 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
463 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
464 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
465 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
466 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
467 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
468 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
469 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
470 Zuhn have made contributions both large and small.
472 Jim Blandy added support for preprocessor macros, while working for Red
476 @chapter A Sample @value{GDBN} Session
478 You can use this manual at your leisure to read all about @value{GDBN}.
479 However, a handful of commands are enough to get started using the
480 debugger. This chapter illustrates those commands.
483 In this sample session, we emphasize user input like this: @b{input},
484 to make it easier to pick out from the surrounding output.
487 @c FIXME: this example may not be appropriate for some configs, where
488 @c FIXME...primary interest is in remote use.
490 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
491 processor) exhibits the following bug: sometimes, when we change its
492 quote strings from the default, the commands used to capture one macro
493 definition within another stop working. In the following short @code{m4}
494 session, we define a macro @code{foo} which expands to @code{0000}; we
495 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
496 same thing. However, when we change the open quote string to
497 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
498 procedure fails to define a new synonym @code{baz}:
507 @b{define(bar,defn(`foo'))}
511 @b{changequote(<QUOTE>,<UNQUOTE>)}
513 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
516 m4: End of input: 0: fatal error: EOF in string
520 Let us use @value{GDBN} to try to see what is going on.
523 $ @b{@value{GDBP} m4}
524 @c FIXME: this falsifies the exact text played out, to permit smallbook
525 @c FIXME... format to come out better.
526 @value{GDBN} is free software and you are welcome to distribute copies
527 of it under certain conditions; type "show copying" to see
529 There is absolutely no warranty for @value{GDBN}; type "show warranty"
532 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
537 @value{GDBN} reads only enough symbol data to know where to find the
538 rest when needed; as a result, the first prompt comes up very quickly.
539 We now tell @value{GDBN} to use a narrower display width than usual, so
540 that examples fit in this manual.
543 (@value{GDBP}) @b{set width 70}
547 We need to see how the @code{m4} built-in @code{changequote} works.
548 Having looked at the source, we know the relevant subroutine is
549 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
550 @code{break} command.
553 (@value{GDBP}) @b{break m4_changequote}
554 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
558 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
559 control; as long as control does not reach the @code{m4_changequote}
560 subroutine, the program runs as usual:
563 (@value{GDBP}) @b{run}
564 Starting program: /work/Editorial/gdb/gnu/m4/m4
572 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
573 suspends execution of @code{m4}, displaying information about the
574 context where it stops.
577 @b{changequote(<QUOTE>,<UNQUOTE>)}
579 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
581 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
585 Now we use the command @code{n} (@code{next}) to advance execution to
586 the next line of the current function.
590 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
595 @code{set_quotes} looks like a promising subroutine. We can go into it
596 by using the command @code{s} (@code{step}) instead of @code{next}.
597 @code{step} goes to the next line to be executed in @emph{any}
598 subroutine, so it steps into @code{set_quotes}.
602 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
604 530 if (lquote != def_lquote)
608 The display that shows the subroutine where @code{m4} is now
609 suspended (and its arguments) is called a stack frame display. It
610 shows a summary of the stack. We can use the @code{backtrace}
611 command (which can also be spelled @code{bt}), to see where we are
612 in the stack as a whole: the @code{backtrace} command displays a
613 stack frame for each active subroutine.
616 (@value{GDBP}) @b{bt}
617 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
619 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
621 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
622 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
624 #4 0x79dc in expand_input () at macro.c:40
625 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
629 We step through a few more lines to see what happens. The first two
630 times, we can use @samp{s}; the next two times we use @code{n} to avoid
631 falling into the @code{xstrdup} subroutine.
635 0x3b5c 532 if (rquote != def_rquote)
637 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
638 def_lquote : xstrdup(lq);
640 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
643 538 len_lquote = strlen(rquote);
647 The last line displayed looks a little odd; we can examine the variables
648 @code{lquote} and @code{rquote} to see if they are in fact the new left
649 and right quotes we specified. We use the command @code{p}
650 (@code{print}) to see their values.
653 (@value{GDBP}) @b{p lquote}
654 $1 = 0x35d40 "<QUOTE>"
655 (@value{GDBP}) @b{p rquote}
656 $2 = 0x35d50 "<UNQUOTE>"
660 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
661 To look at some context, we can display ten lines of source
662 surrounding the current line with the @code{l} (@code{list}) command.
668 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
670 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
673 538 len_lquote = strlen(rquote);
674 539 len_rquote = strlen(lquote);
681 Let us step past the two lines that set @code{len_lquote} and
682 @code{len_rquote}, and then examine the values of those variables.
686 539 len_rquote = strlen(lquote);
689 (@value{GDBP}) @b{p len_lquote}
691 (@value{GDBP}) @b{p len_rquote}
696 That certainly looks wrong, assuming @code{len_lquote} and
697 @code{len_rquote} are meant to be the lengths of @code{lquote} and
698 @code{rquote} respectively. We can set them to better values using
699 the @code{p} command, since it can print the value of
700 any expression---and that expression can include subroutine calls and
704 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
706 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
711 Is that enough to fix the problem of using the new quotes with the
712 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
713 executing with the @code{c} (@code{continue}) command, and then try the
714 example that caused trouble initially:
720 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
727 Success! The new quotes now work just as well as the default ones. The
728 problem seems to have been just the two typos defining the wrong
729 lengths. We allow @code{m4} exit by giving it an EOF as input:
733 Program exited normally.
737 The message @samp{Program exited normally.} is from @value{GDBN}; it
738 indicates @code{m4} has finished executing. We can end our @value{GDBN}
739 session with the @value{GDBN} @code{quit} command.
742 (@value{GDBP}) @b{quit}
746 @chapter Getting In and Out of @value{GDBN}
748 This chapter discusses how to start @value{GDBN}, and how to get out of it.
752 type @samp{@value{GDBP}} to start @value{GDBN}.
754 type @kbd{quit} or @kbd{C-d} to exit.
758 * Invoking GDB:: How to start @value{GDBN}
759 * Quitting GDB:: How to quit @value{GDBN}
760 * Shell Commands:: How to use shell commands inside @value{GDBN}
761 * Logging output:: How to log @value{GDBN}'s output to a file
765 @section Invoking @value{GDBN}
767 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
768 @value{GDBN} reads commands from the terminal until you tell it to exit.
770 You can also run @code{@value{GDBP}} with a variety of arguments and options,
771 to specify more of your debugging environment at the outset.
773 The command-line options described here are designed
774 to cover a variety of situations; in some environments, some of these
775 options may effectively be unavailable.
777 The most usual way to start @value{GDBN} is with one argument,
778 specifying an executable program:
781 @value{GDBP} @var{program}
785 You can also start with both an executable program and a core file
789 @value{GDBP} @var{program} @var{core}
792 You can, instead, specify a process ID as a second argument, if you want
793 to debug a running process:
796 @value{GDBP} @var{program} 1234
800 would attach @value{GDBN} to process @code{1234} (unless you also have a file
801 named @file{1234}; @value{GDBN} does check for a core file first).
803 Taking advantage of the second command-line argument requires a fairly
804 complete operating system; when you use @value{GDBN} as a remote
805 debugger attached to a bare board, there may not be any notion of
806 ``process'', and there is often no way to get a core dump. @value{GDBN}
807 will warn you if it is unable to attach or to read core dumps.
809 You can optionally have @code{@value{GDBP}} pass any arguments after the
810 executable file to the inferior using @code{--args}. This option stops
813 gdb --args gcc -O2 -c foo.c
815 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
816 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
818 You can run @code{@value{GDBP}} without printing the front material, which describes
819 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
826 You can further control how @value{GDBN} starts up by using command-line
827 options. @value{GDBN} itself can remind you of the options available.
837 to display all available options and briefly describe their use
838 (@samp{@value{GDBP} -h} is a shorter equivalent).
840 All options and command line arguments you give are processed
841 in sequential order. The order makes a difference when the
842 @samp{-x} option is used.
846 * File Options:: Choosing files
847 * Mode Options:: Choosing modes
851 @subsection Choosing files
853 When @value{GDBN} starts, it reads any arguments other than options as
854 specifying an executable file and core file (or process ID). This is
855 the same as if the arguments were specified by the @samp{-se} and
856 @samp{-c} (or @samp{-p} options respectively. (@value{GDBN} reads the
857 first argument that does not have an associated option flag as
858 equivalent to the @samp{-se} option followed by that argument; and the
859 second argument that does not have an associated option flag, if any, as
860 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
861 If the second argument begins with a decimal digit, @value{GDBN} will
862 first attempt to attach to it as a process, and if that fails, attempt
863 to open it as a corefile. If you have a corefile whose name begins with
864 a digit, you can prevent @value{GDBN} from treating it as a pid by
865 prefixing it with @file{./}, eg. @file{./12345}.
867 If @value{GDBN} has not been configured to included core file support,
868 such as for most embedded targets, then it will complain about a second
869 argument and ignore it.
871 Many options have both long and short forms; both are shown in the
872 following list. @value{GDBN} also recognizes the long forms if you truncate
873 them, so long as enough of the option is present to be unambiguous.
874 (If you prefer, you can flag option arguments with @samp{--} rather
875 than @samp{-}, though we illustrate the more usual convention.)
877 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
878 @c way, both those who look for -foo and --foo in the index, will find
882 @item -symbols @var{file}
884 @cindex @code{--symbols}
886 Read symbol table from file @var{file}.
888 @item -exec @var{file}
890 @cindex @code{--exec}
892 Use file @var{file} as the executable file to execute when appropriate,
893 and for examining pure data in conjunction with a core dump.
897 Read symbol table from file @var{file} and use it as the executable
900 @item -core @var{file}
902 @cindex @code{--core}
904 Use file @var{file} as a core dump to examine.
906 @item -c @var{number}
907 @item -pid @var{number}
908 @itemx -p @var{number}
911 Connect to process ID @var{number}, as with the @code{attach} command.
912 If there is no such process, @value{GDBN} will attempt to open a core
913 file named @var{number}.
915 @item -command @var{file}
917 @cindex @code{--command}
919 Execute @value{GDBN} commands from file @var{file}. @xref{Command
920 Files,, Command files}.
922 @item -directory @var{directory}
923 @itemx -d @var{directory}
924 @cindex @code{--directory}
926 Add @var{directory} to the path to search for source files.
930 @cindex @code{--mapped}
932 @emph{Warning: this option depends on operating system facilities that are not
933 supported on all systems.}@*
934 If memory-mapped files are available on your system through the @code{mmap}
935 system call, you can use this option
936 to have @value{GDBN} write the symbols from your
937 program into a reusable file in the current directory. If the program you are debugging is
938 called @file{/tmp/fred}, the mapped symbol file is @file{/tmp/fred.syms}.
939 Future @value{GDBN} debugging sessions notice the presence of this file,
940 and can quickly map in symbol information from it, rather than reading
941 the symbol table from the executable program.
943 The @file{.syms} file is specific to the host machine where @value{GDBN}
944 is run. It holds an exact image of the internal @value{GDBN} symbol
945 table. It cannot be shared across multiple host platforms.
949 @cindex @code{--readnow}
951 Read each symbol file's entire symbol table immediately, rather than
952 the default, which is to read it incrementally as it is needed.
953 This makes startup slower, but makes future operations faster.
957 You typically combine the @code{-mapped} and @code{-readnow} options in
958 order to build a @file{.syms} file that contains complete symbol
959 information. (@xref{Files,,Commands to specify files}, for information
960 on @file{.syms} files.) A simple @value{GDBN} invocation to do nothing
961 but build a @file{.syms} file for future use is:
964 gdb -batch -nx -mapped -readnow programname
968 @subsection Choosing modes
970 You can run @value{GDBN} in various alternative modes---for example, in
971 batch mode or quiet mode.
978 Do not execute commands found in any initialization files. Normally,
979 @value{GDBN} executes the commands in these files after all the command
980 options and arguments have been processed. @xref{Command Files,,Command
986 @cindex @code{--quiet}
987 @cindex @code{--silent}
989 ``Quiet''. Do not print the introductory and copyright messages. These
990 messages are also suppressed in batch mode.
993 @cindex @code{--batch}
994 Run in batch mode. Exit with status @code{0} after processing all the
995 command files specified with @samp{-x} (and all commands from
996 initialization files, if not inhibited with @samp{-n}). Exit with
997 nonzero status if an error occurs in executing the @value{GDBN} commands
998 in the command files.
1000 Batch mode may be useful for running @value{GDBN} as a filter, for
1001 example to download and run a program on another computer; in order to
1002 make this more useful, the message
1005 Program exited normally.
1009 (which is ordinarily issued whenever a program running under
1010 @value{GDBN} control terminates) is not issued when running in batch
1015 @cindex @code{--nowindows}
1017 ``No windows''. If @value{GDBN} comes with a graphical user interface
1018 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1019 interface. If no GUI is available, this option has no effect.
1023 @cindex @code{--windows}
1025 If @value{GDBN} includes a GUI, then this option requires it to be
1028 @item -cd @var{directory}
1030 Run @value{GDBN} using @var{directory} as its working directory,
1031 instead of the current directory.
1035 @cindex @code{--fullname}
1037 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1038 subprocess. It tells @value{GDBN} to output the full file name and line
1039 number in a standard, recognizable fashion each time a stack frame is
1040 displayed (which includes each time your program stops). This
1041 recognizable format looks like two @samp{\032} characters, followed by
1042 the file name, line number and character position separated by colons,
1043 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1044 @samp{\032} characters as a signal to display the source code for the
1048 @cindex @code{--epoch}
1049 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1050 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1051 routines so as to allow Epoch to display values of expressions in a
1054 @item -annotate @var{level}
1055 @cindex @code{--annotate}
1056 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1057 effect is identical to using @samp{set annotate @var{level}}
1058 (@pxref{Annotations}). The annotation @var{level} controls how much
1059 information @value{GDBN} prints together with its prompt, values of
1060 expressions, source lines, and other types of output. Level 0 is the
1061 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1062 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1063 that control @value{GDBN}, and level 2 has been deprecated.
1065 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
1069 @cindex @code{--args}
1070 Change interpretation of command line so that arguments following the
1071 executable file are passed as command line arguments to the inferior.
1072 This option stops option processing.
1074 @item -baud @var{bps}
1076 @cindex @code{--baud}
1078 Set the line speed (baud rate or bits per second) of any serial
1079 interface used by @value{GDBN} for remote debugging.
1081 @item -tty @var{device}
1082 @itemx -t @var{device}
1083 @cindex @code{--tty}
1085 Run using @var{device} for your program's standard input and output.
1086 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1088 @c resolve the situation of these eventually
1090 @cindex @code{--tui}
1091 Activate the @dfn{Text User Interface} when starting. The Text User
1092 Interface manages several text windows on the terminal, showing
1093 source, assembly, registers and @value{GDBN} command outputs
1094 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1095 Text User Interface can be enabled by invoking the program
1096 @samp{gdbtui}. Do not use this option if you run @value{GDBN} from
1097 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1100 @c @cindex @code{--xdb}
1101 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1102 @c For information, see the file @file{xdb_trans.html}, which is usually
1103 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1106 @item -interpreter @var{interp}
1107 @cindex @code{--interpreter}
1108 Use the interpreter @var{interp} for interface with the controlling
1109 program or device. This option is meant to be set by programs which
1110 communicate with @value{GDBN} using it as a back end.
1111 @xref{Interpreters, , Command Interpreters}.
1113 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1114 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1115 The @sc{gdb/mi} Interface}) included since @var{GDBN} version 6.0. The
1116 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1117 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1118 @sc{gdb/mi} interfaces are no longer supported.
1121 @cindex @code{--write}
1122 Open the executable and core files for both reading and writing. This
1123 is equivalent to the @samp{set write on} command inside @value{GDBN}
1127 @cindex @code{--statistics}
1128 This option causes @value{GDBN} to print statistics about time and
1129 memory usage after it completes each command and returns to the prompt.
1132 @cindex @code{--version}
1133 This option causes @value{GDBN} to print its version number and
1134 no-warranty blurb, and exit.
1139 @section Quitting @value{GDBN}
1140 @cindex exiting @value{GDBN}
1141 @cindex leaving @value{GDBN}
1144 @kindex quit @r{[}@var{expression}@r{]}
1145 @kindex q @r{(@code{quit})}
1146 @item quit @r{[}@var{expression}@r{]}
1148 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1149 @code{q}), or type an end-of-file character (usually @kbd{C-d}). If you
1150 do not supply @var{expression}, @value{GDBN} will terminate normally;
1151 otherwise it will terminate using the result of @var{expression} as the
1156 An interrupt (often @kbd{C-c}) does not exit from @value{GDBN}, but rather
1157 terminates the action of any @value{GDBN} command that is in progress and
1158 returns to @value{GDBN} command level. It is safe to type the interrupt
1159 character at any time because @value{GDBN} does not allow it to take effect
1160 until a time when it is safe.
1162 If you have been using @value{GDBN} to control an attached process or
1163 device, you can release it with the @code{detach} command
1164 (@pxref{Attach, ,Debugging an already-running process}).
1166 @node Shell Commands
1167 @section Shell commands
1169 If you need to execute occasional shell commands during your
1170 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1171 just use the @code{shell} command.
1175 @cindex shell escape
1176 @item shell @var{command string}
1177 Invoke a standard shell to execute @var{command string}.
1178 If it exists, the environment variable @code{SHELL} determines which
1179 shell to run. Otherwise @value{GDBN} uses the default shell
1180 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1183 The utility @code{make} is often needed in development environments.
1184 You do not have to use the @code{shell} command for this purpose in
1189 @cindex calling make
1190 @item make @var{make-args}
1191 Execute the @code{make} program with the specified
1192 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1195 @node Logging output
1196 @section Logging output
1197 @cindex logging @value{GDBN} output
1199 You may want to save the output of @value{GDBN} commands to a file.
1200 There are several commands to control @value{GDBN}'s logging.
1204 @item set logging on
1206 @item set logging off
1208 @item set logging file @var{file}
1209 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1210 @item set logging overwrite [on|off]
1211 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1212 you want @code{set logging on} to overwrite the logfile instead.
1213 @item set logging redirect [on|off]
1214 By default, @value{GDBN} output will go to both the terminal and the logfile.
1215 Set @code{redirect} if you want output to go only to the log file.
1216 @kindex show logging
1218 Show the current values of the logging settings.
1222 @chapter @value{GDBN} Commands
1224 You can abbreviate a @value{GDBN} command to the first few letters of the command
1225 name, if that abbreviation is unambiguous; and you can repeat certain
1226 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1227 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1228 show you the alternatives available, if there is more than one possibility).
1231 * Command Syntax:: How to give commands to @value{GDBN}
1232 * Completion:: Command completion
1233 * Help:: How to ask @value{GDBN} for help
1236 @node Command Syntax
1237 @section Command syntax
1239 A @value{GDBN} command is a single line of input. There is no limit on
1240 how long it can be. It starts with a command name, which is followed by
1241 arguments whose meaning depends on the command name. For example, the
1242 command @code{step} accepts an argument which is the number of times to
1243 step, as in @samp{step 5}. You can also use the @code{step} command
1244 with no arguments. Some commands do not allow any arguments.
1246 @cindex abbreviation
1247 @value{GDBN} command names may always be truncated if that abbreviation is
1248 unambiguous. Other possible command abbreviations are listed in the
1249 documentation for individual commands. In some cases, even ambiguous
1250 abbreviations are allowed; for example, @code{s} is specially defined as
1251 equivalent to @code{step} even though there are other commands whose
1252 names start with @code{s}. You can test abbreviations by using them as
1253 arguments to the @code{help} command.
1255 @cindex repeating commands
1256 @kindex RET @r{(repeat last command)}
1257 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1258 repeat the previous command. Certain commands (for example, @code{run})
1259 will not repeat this way; these are commands whose unintentional
1260 repetition might cause trouble and which you are unlikely to want to
1263 The @code{list} and @code{x} commands, when you repeat them with
1264 @key{RET}, construct new arguments rather than repeating
1265 exactly as typed. This permits easy scanning of source or memory.
1267 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1268 output, in a way similar to the common utility @code{more}
1269 (@pxref{Screen Size,,Screen size}). Since it is easy to press one
1270 @key{RET} too many in this situation, @value{GDBN} disables command
1271 repetition after any command that generates this sort of display.
1273 @kindex # @r{(a comment)}
1275 Any text from a @kbd{#} to the end of the line is a comment; it does
1276 nothing. This is useful mainly in command files (@pxref{Command
1277 Files,,Command files}).
1279 @cindex repeating command sequences
1280 @kindex C-o @r{(operate-and-get-next)}
1281 The @kbd{C-o} binding is useful for repeating a complex sequence of
1282 commands. This command accepts the current line, like @kbd{RET}, and
1283 then fetches the next line relative to the current line from the history
1287 @section Command completion
1290 @cindex word completion
1291 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1292 only one possibility; it can also show you what the valid possibilities
1293 are for the next word in a command, at any time. This works for @value{GDBN}
1294 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1296 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1297 of a word. If there is only one possibility, @value{GDBN} fills in the
1298 word, and waits for you to finish the command (or press @key{RET} to
1299 enter it). For example, if you type
1301 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1302 @c complete accuracy in these examples; space introduced for clarity.
1303 @c If texinfo enhancements make it unnecessary, it would be nice to
1304 @c replace " @key" by "@key" in the following...
1306 (@value{GDBP}) info bre @key{TAB}
1310 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1311 the only @code{info} subcommand beginning with @samp{bre}:
1314 (@value{GDBP}) info breakpoints
1318 You can either press @key{RET} at this point, to run the @code{info
1319 breakpoints} command, or backspace and enter something else, if
1320 @samp{breakpoints} does not look like the command you expected. (If you
1321 were sure you wanted @code{info breakpoints} in the first place, you
1322 might as well just type @key{RET} immediately after @samp{info bre},
1323 to exploit command abbreviations rather than command completion).
1325 If there is more than one possibility for the next word when you press
1326 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1327 characters and try again, or just press @key{TAB} a second time;
1328 @value{GDBN} displays all the possible completions for that word. For
1329 example, you might want to set a breakpoint on a subroutine whose name
1330 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1331 just sounds the bell. Typing @key{TAB} again displays all the
1332 function names in your program that begin with those characters, for
1336 (@value{GDBP}) b make_ @key{TAB}
1337 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1338 make_a_section_from_file make_environ
1339 make_abs_section make_function_type
1340 make_blockvector make_pointer_type
1341 make_cleanup make_reference_type
1342 make_command make_symbol_completion_list
1343 (@value{GDBP}) b make_
1347 After displaying the available possibilities, @value{GDBN} copies your
1348 partial input (@samp{b make_} in the example) so you can finish the
1351 If you just want to see the list of alternatives in the first place, you
1352 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1353 means @kbd{@key{META} ?}. You can type this either by holding down a
1354 key designated as the @key{META} shift on your keyboard (if there is
1355 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1357 @cindex quotes in commands
1358 @cindex completion of quoted strings
1359 Sometimes the string you need, while logically a ``word'', may contain
1360 parentheses or other characters that @value{GDBN} normally excludes from
1361 its notion of a word. To permit word completion to work in this
1362 situation, you may enclose words in @code{'} (single quote marks) in
1363 @value{GDBN} commands.
1365 The most likely situation where you might need this is in typing the
1366 name of a C@t{++} function. This is because C@t{++} allows function
1367 overloading (multiple definitions of the same function, distinguished
1368 by argument type). For example, when you want to set a breakpoint you
1369 may need to distinguish whether you mean the version of @code{name}
1370 that takes an @code{int} parameter, @code{name(int)}, or the version
1371 that takes a @code{float} parameter, @code{name(float)}. To use the
1372 word-completion facilities in this situation, type a single quote
1373 @code{'} at the beginning of the function name. This alerts
1374 @value{GDBN} that it may need to consider more information than usual
1375 when you press @key{TAB} or @kbd{M-?} to request word completion:
1378 (@value{GDBP}) b 'bubble( @kbd{M-?}
1379 bubble(double,double) bubble(int,int)
1380 (@value{GDBP}) b 'bubble(
1383 In some cases, @value{GDBN} can tell that completing a name requires using
1384 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1385 completing as much as it can) if you do not type the quote in the first
1389 (@value{GDBP}) b bub @key{TAB}
1390 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1391 (@value{GDBP}) b 'bubble(
1395 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1396 you have not yet started typing the argument list when you ask for
1397 completion on an overloaded symbol.
1399 For more information about overloaded functions, see @ref{C plus plus
1400 expressions, ,C@t{++} expressions}. You can use the command @code{set
1401 overload-resolution off} to disable overload resolution;
1402 see @ref{Debugging C plus plus, ,@value{GDBN} features for C@t{++}}.
1406 @section Getting help
1407 @cindex online documentation
1410 You can always ask @value{GDBN} itself for information on its commands,
1411 using the command @code{help}.
1414 @kindex h @r{(@code{help})}
1417 You can use @code{help} (abbreviated @code{h}) with no arguments to
1418 display a short list of named classes of commands:
1422 List of classes of commands:
1424 aliases -- Aliases of other commands
1425 breakpoints -- Making program stop at certain points
1426 data -- Examining data
1427 files -- Specifying and examining files
1428 internals -- Maintenance commands
1429 obscure -- Obscure features
1430 running -- Running the program
1431 stack -- Examining the stack
1432 status -- Status inquiries
1433 support -- Support facilities
1434 tracepoints -- Tracing of program execution without@*
1435 stopping the program
1436 user-defined -- User-defined commands
1438 Type "help" followed by a class name for a list of
1439 commands in that class.
1440 Type "help" followed by command name for full
1442 Command name abbreviations are allowed if unambiguous.
1445 @c the above line break eliminates huge line overfull...
1447 @item help @var{class}
1448 Using one of the general help classes as an argument, you can get a
1449 list of the individual commands in that class. For example, here is the
1450 help display for the class @code{status}:
1453 (@value{GDBP}) help status
1458 @c Line break in "show" line falsifies real output, but needed
1459 @c to fit in smallbook page size.
1460 info -- Generic command for showing things
1461 about the program being debugged
1462 show -- Generic command for showing things
1465 Type "help" followed by command name for full
1467 Command name abbreviations are allowed if unambiguous.
1471 @item help @var{command}
1472 With a command name as @code{help} argument, @value{GDBN} displays a
1473 short paragraph on how to use that command.
1476 @item apropos @var{args}
1477 The @code{apropos @var{args}} command searches through all of the @value{GDBN}
1478 commands, and their documentation, for the regular expression specified in
1479 @var{args}. It prints out all matches found. For example:
1490 set symbol-reloading -- Set dynamic symbol table reloading
1491 multiple times in one run
1492 show symbol-reloading -- Show dynamic symbol table reloading
1493 multiple times in one run
1498 @item complete @var{args}
1499 The @code{complete @var{args}} command lists all the possible completions
1500 for the beginning of a command. Use @var{args} to specify the beginning of the
1501 command you want completed. For example:
1507 @noindent results in:
1518 @noindent This is intended for use by @sc{gnu} Emacs.
1521 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1522 and @code{show} to inquire about the state of your program, or the state
1523 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1524 manual introduces each of them in the appropriate context. The listings
1525 under @code{info} and under @code{show} in the Index point to
1526 all the sub-commands. @xref{Index}.
1531 @kindex i @r{(@code{info})}
1533 This command (abbreviated @code{i}) is for describing the state of your
1534 program. For example, you can list the arguments given to your program
1535 with @code{info args}, list the registers currently in use with @code{info
1536 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1537 You can get a complete list of the @code{info} sub-commands with
1538 @w{@code{help info}}.
1542 You can assign the result of an expression to an environment variable with
1543 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1544 @code{set prompt $}.
1548 In contrast to @code{info}, @code{show} is for describing the state of
1549 @value{GDBN} itself.
1550 You can change most of the things you can @code{show}, by using the
1551 related command @code{set}; for example, you can control what number
1552 system is used for displays with @code{set radix}, or simply inquire
1553 which is currently in use with @code{show radix}.
1556 To display all the settable parameters and their current
1557 values, you can use @code{show} with no arguments; you may also use
1558 @code{info set}. Both commands produce the same display.
1559 @c FIXME: "info set" violates the rule that "info" is for state of
1560 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1561 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1565 Here are three miscellaneous @code{show} subcommands, all of which are
1566 exceptional in lacking corresponding @code{set} commands:
1569 @kindex show version
1570 @cindex version number
1572 Show what version of @value{GDBN} is running. You should include this
1573 information in @value{GDBN} bug-reports. If multiple versions of
1574 @value{GDBN} are in use at your site, you may need to determine which
1575 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1576 commands are introduced, and old ones may wither away. Also, many
1577 system vendors ship variant versions of @value{GDBN}, and there are
1578 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1579 The version number is the same as the one announced when you start
1582 @kindex show copying
1584 Display information about permission for copying @value{GDBN}.
1586 @kindex show warranty
1588 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1589 if your version of @value{GDBN} comes with one.
1594 @chapter Running Programs Under @value{GDBN}
1596 When you run a program under @value{GDBN}, you must first generate
1597 debugging information when you compile it.
1599 You may start @value{GDBN} with its arguments, if any, in an environment
1600 of your choice. If you are doing native debugging, you may redirect
1601 your program's input and output, debug an already running process, or
1602 kill a child process.
1605 * Compilation:: Compiling for debugging
1606 * Starting:: Starting your program
1607 * Arguments:: Your program's arguments
1608 * Environment:: Your program's environment
1610 * Working Directory:: Your program's working directory
1611 * Input/Output:: Your program's input and output
1612 * Attach:: Debugging an already-running process
1613 * Kill Process:: Killing the child process
1615 * Threads:: Debugging programs with multiple threads
1616 * Processes:: Debugging programs with multiple processes
1620 @section Compiling for debugging
1622 In order to debug a program effectively, you need to generate
1623 debugging information when you compile it. This debugging information
1624 is stored in the object file; it describes the data type of each
1625 variable or function and the correspondence between source line numbers
1626 and addresses in the executable code.
1628 To request debugging information, specify the @samp{-g} option when you run
1631 Most compilers do not include information about preprocessor macros in
1632 the debugging information if you specify the @option{-g} flag alone,
1633 because this information is rather large. Version 3.1 of @value{NGCC},
1634 the @sc{gnu} C compiler, provides macro information if you specify the
1635 options @option{-gdwarf-2} and @option{-g3}; the former option requests
1636 debugging information in the Dwarf 2 format, and the latter requests
1637 ``extra information''. In the future, we hope to find more compact ways
1638 to represent macro information, so that it can be included with
1641 Many C compilers are unable to handle the @samp{-g} and @samp{-O}
1642 options together. Using those compilers, you cannot generate optimized
1643 executables containing debugging information.
1645 @value{NGCC}, the @sc{gnu} C compiler, supports @samp{-g} with or
1646 without @samp{-O}, making it possible to debug optimized code. We
1647 recommend that you @emph{always} use @samp{-g} whenever you compile a
1648 program. You may think your program is correct, but there is no sense
1649 in pushing your luck.
1651 @cindex optimized code, debugging
1652 @cindex debugging optimized code
1653 When you debug a program compiled with @samp{-g -O}, remember that the
1654 optimizer is rearranging your code; the debugger shows you what is
1655 really there. Do not be too surprised when the execution path does not
1656 exactly match your source file! An extreme example: if you define a
1657 variable, but never use it, @value{GDBN} never sees that
1658 variable---because the compiler optimizes it out of existence.
1660 Some things do not work as well with @samp{-g -O} as with just
1661 @samp{-g}, particularly on machines with instruction scheduling. If in
1662 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1663 please report it to us as a bug (including a test case!).
1664 @xref{Variables}, for more information about debugging optimized code.
1666 Older versions of the @sc{gnu} C compiler permitted a variant option
1667 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1668 format; if your @sc{gnu} C compiler has this option, do not use it.
1672 @section Starting your program
1678 @kindex r @r{(@code{run})}
1681 Use the @code{run} command to start your program under @value{GDBN}.
1682 You must first specify the program name (except on VxWorks) with an
1683 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1684 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1685 (@pxref{Files, ,Commands to specify files}).
1689 If you are running your program in an execution environment that
1690 supports processes, @code{run} creates an inferior process and makes
1691 that process run your program. (In environments without processes,
1692 @code{run} jumps to the start of your program.)
1694 The execution of a program is affected by certain information it
1695 receives from its superior. @value{GDBN} provides ways to specify this
1696 information, which you must do @emph{before} starting your program. (You
1697 can change it after starting your program, but such changes only affect
1698 your program the next time you start it.) This information may be
1699 divided into four categories:
1702 @item The @emph{arguments.}
1703 Specify the arguments to give your program as the arguments of the
1704 @code{run} command. If a shell is available on your target, the shell
1705 is used to pass the arguments, so that you may use normal conventions
1706 (such as wildcard expansion or variable substitution) in describing
1708 In Unix systems, you can control which shell is used with the
1709 @code{SHELL} environment variable.
1710 @xref{Arguments, ,Your program's arguments}.
1712 @item The @emph{environment.}
1713 Your program normally inherits its environment from @value{GDBN}, but you can
1714 use the @value{GDBN} commands @code{set environment} and @code{unset
1715 environment} to change parts of the environment that affect
1716 your program. @xref{Environment, ,Your program's environment}.
1718 @item The @emph{working directory.}
1719 Your program inherits its working directory from @value{GDBN}. You can set
1720 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1721 @xref{Working Directory, ,Your program's working directory}.
1723 @item The @emph{standard input and output.}
1724 Your program normally uses the same device for standard input and
1725 standard output as @value{GDBN} is using. You can redirect input and output
1726 in the @code{run} command line, or you can use the @code{tty} command to
1727 set a different device for your program.
1728 @xref{Input/Output, ,Your program's input and output}.
1731 @emph{Warning:} While input and output redirection work, you cannot use
1732 pipes to pass the output of the program you are debugging to another
1733 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1737 When you issue the @code{run} command, your program begins to execute
1738 immediately. @xref{Stopping, ,Stopping and continuing}, for discussion
1739 of how to arrange for your program to stop. Once your program has
1740 stopped, you may call functions in your program, using the @code{print}
1741 or @code{call} commands. @xref{Data, ,Examining Data}.
1743 If the modification time of your symbol file has changed since the last
1744 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1745 table, and reads it again. When it does this, @value{GDBN} tries to retain
1746 your current breakpoints.
1751 @cindex run to main procedure
1752 The name of the main procedure can vary from language to language.
1753 With C or C@t{++}, the main procedure name is always @code{main}, but
1754 other languages such as Ada do not require a specific name for their
1755 main procedure. The debugger provides a convenient way to start the
1756 execution of the program and to stop at the beginning of the main
1757 procedure, depending on the language used.
1759 The @samp{start} command does the equivalent of setting a temporary
1760 breakpoint at the beginning of the main procedure and then invoking
1761 the @samp{run} command.
1763 Some programs contain an elaboration phase where some startup code is
1764 executed before the main program is called. This depends on the
1765 languages used to write your program. In C@t{++} for instance,
1766 constructors for static and global objects are executed before
1767 @code{main} is called. It is therefore possible that the debugger stops
1768 before reaching the main procedure. However, the temporary breakpoint
1769 will remain to halt execution.
1771 Specify the arguments to give to your program as arguments to the
1772 @samp{start} command. These arguments will be given verbatim to the
1773 underlying @samp{run} command. Note that the same arguments will be
1774 reused if no argument is provided during subsequent calls to
1775 @samp{start} or @samp{run}.
1777 It is sometimes necessary to debug the program during elaboration. In
1778 these cases, using the @code{start} command would stop the execution of
1779 your program too late, as the program would have already completed the
1780 elaboration phase. Under these circumstances, insert breakpoints in your
1781 elaboration code before running your program.
1785 @section Your program's arguments
1787 @cindex arguments (to your program)
1788 The arguments to your program can be specified by the arguments of the
1790 They are passed to a shell, which expands wildcard characters and
1791 performs redirection of I/O, and thence to your program. Your
1792 @code{SHELL} environment variable (if it exists) specifies what shell
1793 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1794 the default shell (@file{/bin/sh} on Unix).
1796 On non-Unix systems, the program is usually invoked directly by
1797 @value{GDBN}, which emulates I/O redirection via the appropriate system
1798 calls, and the wildcard characters are expanded by the startup code of
1799 the program, not by the shell.
1801 @code{run} with no arguments uses the same arguments used by the previous
1802 @code{run}, or those set by the @code{set args} command.
1807 Specify the arguments to be used the next time your program is run. If
1808 @code{set args} has no arguments, @code{run} executes your program
1809 with no arguments. Once you have run your program with arguments,
1810 using @code{set args} before the next @code{run} is the only way to run
1811 it again without arguments.
1815 Show the arguments to give your program when it is started.
1819 @section Your program's environment
1821 @cindex environment (of your program)
1822 The @dfn{environment} consists of a set of environment variables and
1823 their values. Environment variables conventionally record such things as
1824 your user name, your home directory, your terminal type, and your search
1825 path for programs to run. Usually you set up environment variables with
1826 the shell and they are inherited by all the other programs you run. When
1827 debugging, it can be useful to try running your program with a modified
1828 environment without having to start @value{GDBN} over again.
1832 @item path @var{directory}
1833 Add @var{directory} to the front of the @code{PATH} environment variable
1834 (the search path for executables) that will be passed to your program.
1835 The value of @code{PATH} used by @value{GDBN} does not change.
1836 You may specify several directory names, separated by whitespace or by a
1837 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1838 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1839 is moved to the front, so it is searched sooner.
1841 You can use the string @samp{$cwd} to refer to whatever is the current
1842 working directory at the time @value{GDBN} searches the path. If you
1843 use @samp{.} instead, it refers to the directory where you executed the
1844 @code{path} command. @value{GDBN} replaces @samp{.} in the
1845 @var{directory} argument (with the current path) before adding
1846 @var{directory} to the search path.
1847 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1848 @c document that, since repeating it would be a no-op.
1852 Display the list of search paths for executables (the @code{PATH}
1853 environment variable).
1855 @kindex show environment
1856 @item show environment @r{[}@var{varname}@r{]}
1857 Print the value of environment variable @var{varname} to be given to
1858 your program when it starts. If you do not supply @var{varname},
1859 print the names and values of all environment variables to be given to
1860 your program. You can abbreviate @code{environment} as @code{env}.
1862 @kindex set environment
1863 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1864 Set environment variable @var{varname} to @var{value}. The value
1865 changes for your program only, not for @value{GDBN} itself. @var{value} may
1866 be any string; the values of environment variables are just strings, and
1867 any interpretation is supplied by your program itself. The @var{value}
1868 parameter is optional; if it is eliminated, the variable is set to a
1870 @c "any string" here does not include leading, trailing
1871 @c blanks. Gnu asks: does anyone care?
1873 For example, this command:
1880 tells the debugged program, when subsequently run, that its user is named
1881 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
1882 are not actually required.)
1884 @kindex unset environment
1885 @item unset environment @var{varname}
1886 Remove variable @var{varname} from the environment to be passed to your
1887 program. This is different from @samp{set env @var{varname} =};
1888 @code{unset environment} removes the variable from the environment,
1889 rather than assigning it an empty value.
1892 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
1894 by your @code{SHELL} environment variable if it exists (or
1895 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
1896 that runs an initialization file---such as @file{.cshrc} for C-shell, or
1897 @file{.bashrc} for BASH---any variables you set in that file affect
1898 your program. You may wish to move setting of environment variables to
1899 files that are only run when you sign on, such as @file{.login} or
1902 @node Working Directory
1903 @section Your program's working directory
1905 @cindex working directory (of your program)
1906 Each time you start your program with @code{run}, it inherits its
1907 working directory from the current working directory of @value{GDBN}.
1908 The @value{GDBN} working directory is initially whatever it inherited
1909 from its parent process (typically the shell), but you can specify a new
1910 working directory in @value{GDBN} with the @code{cd} command.
1912 The @value{GDBN} working directory also serves as a default for the commands
1913 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
1918 @item cd @var{directory}
1919 Set the @value{GDBN} working directory to @var{directory}.
1923 Print the @value{GDBN} working directory.
1926 It is generally impossible to find the current working directory of
1927 the process being debugged (since a program can change its directory
1928 during its run). If you work on a system where @value{GDBN} is
1929 configured with the @file{/proc} support, you can use the @code{info
1930 proc} command (@pxref{SVR4 Process Information}) to find out the
1931 current working directory of the debuggee.
1934 @section Your program's input and output
1939 By default, the program you run under @value{GDBN} does input and output to
1940 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
1941 to its own terminal modes to interact with you, but it records the terminal
1942 modes your program was using and switches back to them when you continue
1943 running your program.
1946 @kindex info terminal
1948 Displays information recorded by @value{GDBN} about the terminal modes your
1952 You can redirect your program's input and/or output using shell
1953 redirection with the @code{run} command. For example,
1960 starts your program, diverting its output to the file @file{outfile}.
1963 @cindex controlling terminal
1964 Another way to specify where your program should do input and output is
1965 with the @code{tty} command. This command accepts a file name as
1966 argument, and causes this file to be the default for future @code{run}
1967 commands. It also resets the controlling terminal for the child
1968 process, for future @code{run} commands. For example,
1975 directs that processes started with subsequent @code{run} commands
1976 default to do input and output on the terminal @file{/dev/ttyb} and have
1977 that as their controlling terminal.
1979 An explicit redirection in @code{run} overrides the @code{tty} command's
1980 effect on the input/output device, but not its effect on the controlling
1983 When you use the @code{tty} command or redirect input in the @code{run}
1984 command, only the input @emph{for your program} is affected. The input
1985 for @value{GDBN} still comes from your terminal.
1988 @section Debugging an already-running process
1993 @item attach @var{process-id}
1994 This command attaches to a running process---one that was started
1995 outside @value{GDBN}. (@code{info files} shows your active
1996 targets.) The command takes as argument a process ID. The usual way to
1997 find out the process-id of a Unix process is with the @code{ps} utility,
1998 or with the @samp{jobs -l} shell command.
2000 @code{attach} does not repeat if you press @key{RET} a second time after
2001 executing the command.
2004 To use @code{attach}, your program must be running in an environment
2005 which supports processes; for example, @code{attach} does not work for
2006 programs on bare-board targets that lack an operating system. You must
2007 also have permission to send the process a signal.
2009 When you use @code{attach}, the debugger finds the program running in
2010 the process first by looking in the current working directory, then (if
2011 the program is not found) by using the source file search path
2012 (@pxref{Source Path, ,Specifying source directories}). You can also use
2013 the @code{file} command to load the program. @xref{Files, ,Commands to
2016 The first thing @value{GDBN} does after arranging to debug the specified
2017 process is to stop it. You can examine and modify an attached process
2018 with all the @value{GDBN} commands that are ordinarily available when
2019 you start processes with @code{run}. You can insert breakpoints; you
2020 can step and continue; you can modify storage. If you would rather the
2021 process continue running, you may use the @code{continue} command after
2022 attaching @value{GDBN} to the process.
2027 When you have finished debugging the attached process, you can use the
2028 @code{detach} command to release it from @value{GDBN} control. Detaching
2029 the process continues its execution. After the @code{detach} command,
2030 that process and @value{GDBN} become completely independent once more, and you
2031 are ready to @code{attach} another process or start one with @code{run}.
2032 @code{detach} does not repeat if you press @key{RET} again after
2033 executing the command.
2036 If you exit @value{GDBN} or use the @code{run} command while you have an
2037 attached process, you kill that process. By default, @value{GDBN} asks
2038 for confirmation if you try to do either of these things; you can
2039 control whether or not you need to confirm by using the @code{set
2040 confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
2044 @section Killing the child process
2049 Kill the child process in which your program is running under @value{GDBN}.
2052 This command is useful if you wish to debug a core dump instead of a
2053 running process. @value{GDBN} ignores any core dump file while your program
2056 On some operating systems, a program cannot be executed outside @value{GDBN}
2057 while you have breakpoints set on it inside @value{GDBN}. You can use the
2058 @code{kill} command in this situation to permit running your program
2059 outside the debugger.
2061 The @code{kill} command is also useful if you wish to recompile and
2062 relink your program, since on many systems it is impossible to modify an
2063 executable file while it is running in a process. In this case, when you
2064 next type @code{run}, @value{GDBN} notices that the file has changed, and
2065 reads the symbol table again (while trying to preserve your current
2066 breakpoint settings).
2069 @section Debugging programs with multiple threads
2071 @cindex threads of execution
2072 @cindex multiple threads
2073 @cindex switching threads
2074 In some operating systems, such as HP-UX and Solaris, a single program
2075 may have more than one @dfn{thread} of execution. The precise semantics
2076 of threads differ from one operating system to another, but in general
2077 the threads of a single program are akin to multiple processes---except
2078 that they share one address space (that is, they can all examine and
2079 modify the same variables). On the other hand, each thread has its own
2080 registers and execution stack, and perhaps private memory.
2082 @value{GDBN} provides these facilities for debugging multi-thread
2086 @item automatic notification of new threads
2087 @item @samp{thread @var{threadno}}, a command to switch among threads
2088 @item @samp{info threads}, a command to inquire about existing threads
2089 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2090 a command to apply a command to a list of threads
2091 @item thread-specific breakpoints
2095 @emph{Warning:} These facilities are not yet available on every
2096 @value{GDBN} configuration where the operating system supports threads.
2097 If your @value{GDBN} does not support threads, these commands have no
2098 effect. For example, a system without thread support shows no output
2099 from @samp{info threads}, and always rejects the @code{thread} command,
2103 (@value{GDBP}) info threads
2104 (@value{GDBP}) thread 1
2105 Thread ID 1 not known. Use the "info threads" command to
2106 see the IDs of currently known threads.
2108 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2109 @c doesn't support threads"?
2112 @cindex focus of debugging
2113 @cindex current thread
2114 The @value{GDBN} thread debugging facility allows you to observe all
2115 threads while your program runs---but whenever @value{GDBN} takes
2116 control, one thread in particular is always the focus of debugging.
2117 This thread is called the @dfn{current thread}. Debugging commands show
2118 program information from the perspective of the current thread.
2120 @cindex @code{New} @var{systag} message
2121 @cindex thread identifier (system)
2122 @c FIXME-implementors!! It would be more helpful if the [New...] message
2123 @c included GDB's numeric thread handle, so you could just go to that
2124 @c thread without first checking `info threads'.
2125 Whenever @value{GDBN} detects a new thread in your program, it displays
2126 the target system's identification for the thread with a message in the
2127 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2128 whose form varies depending on the particular system. For example, on
2129 LynxOS, you might see
2132 [New process 35 thread 27]
2136 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2137 the @var{systag} is simply something like @samp{process 368}, with no
2140 @c FIXME!! (1) Does the [New...] message appear even for the very first
2141 @c thread of a program, or does it only appear for the
2142 @c second---i.e.@: when it becomes obvious we have a multithread
2144 @c (2) *Is* there necessarily a first thread always? Or do some
2145 @c multithread systems permit starting a program with multiple
2146 @c threads ab initio?
2148 @cindex thread number
2149 @cindex thread identifier (GDB)
2150 For debugging purposes, @value{GDBN} associates its own thread
2151 number---always a single integer---with each thread in your program.
2154 @kindex info threads
2156 Display a summary of all threads currently in your
2157 program. @value{GDBN} displays for each thread (in this order):
2160 @item the thread number assigned by @value{GDBN}
2162 @item the target system's thread identifier (@var{systag})
2164 @item the current stack frame summary for that thread
2168 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2169 indicates the current thread.
2173 @c end table here to get a little more width for example
2176 (@value{GDBP}) info threads
2177 3 process 35 thread 27 0x34e5 in sigpause ()
2178 2 process 35 thread 23 0x34e5 in sigpause ()
2179 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2185 @cindex debugging multithreaded programs (on HP-UX)
2186 @cindex thread identifier (GDB), on HP-UX
2187 For debugging purposes, @value{GDBN} associates its own thread
2188 number---a small integer assigned in thread-creation order---with each
2189 thread in your program.
2191 @cindex @code{New} @var{systag} message, on HP-UX
2192 @cindex thread identifier (system), on HP-UX
2193 @c FIXME-implementors!! It would be more helpful if the [New...] message
2194 @c included GDB's numeric thread handle, so you could just go to that
2195 @c thread without first checking `info threads'.
2196 Whenever @value{GDBN} detects a new thread in your program, it displays
2197 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2198 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2199 whose form varies depending on the particular system. For example, on
2203 [New thread 2 (system thread 26594)]
2207 when @value{GDBN} notices a new thread.
2210 @kindex info threads (HP-UX)
2212 Display a summary of all threads currently in your
2213 program. @value{GDBN} displays for each thread (in this order):
2216 @item the thread number assigned by @value{GDBN}
2218 @item the target system's thread identifier (@var{systag})
2220 @item the current stack frame summary for that thread
2224 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2225 indicates the current thread.
2229 @c end table here to get a little more width for example
2232 (@value{GDBP}) info threads
2233 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2235 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2236 from /usr/lib/libc.2
2237 1 system thread 27905 0x7b003498 in _brk () \@*
2238 from /usr/lib/libc.2
2242 @kindex thread @var{threadno}
2243 @item thread @var{threadno}
2244 Make thread number @var{threadno} the current thread. The command
2245 argument @var{threadno} is the internal @value{GDBN} thread number, as
2246 shown in the first field of the @samp{info threads} display.
2247 @value{GDBN} responds by displaying the system identifier of the thread
2248 you selected, and its current stack frame summary:
2251 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2252 (@value{GDBP}) thread 2
2253 [Switching to process 35 thread 23]
2254 0x34e5 in sigpause ()
2258 As with the @samp{[New @dots{}]} message, the form of the text after
2259 @samp{Switching to} depends on your system's conventions for identifying
2262 @item thread apply [@var{threadno}] [@var{all}] @var{args}
2263 The @code{thread apply} command allows you to apply a command to one or
2264 more threads. Specify the numbers of the threads that you want affected
2265 with the command argument @var{threadno}. @var{threadno} is the internal
2266 @value{GDBN} thread number, as shown in the first field of the @samp{info
2267 threads} display. To apply a command to all threads, use
2268 @code{thread apply all} @var{args}.
2271 @cindex automatic thread selection
2272 @cindex switching threads automatically
2273 @cindex threads, automatic switching
2274 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2275 signal, it automatically selects the thread where that breakpoint or
2276 signal happened. @value{GDBN} alerts you to the context switch with a
2277 message of the form @samp{[Switching to @var{systag}]} to identify the
2280 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2281 more information about how @value{GDBN} behaves when you stop and start
2282 programs with multiple threads.
2284 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2285 watchpoints in programs with multiple threads.
2288 @section Debugging programs with multiple processes
2290 @cindex fork, debugging programs which call
2291 @cindex multiple processes
2292 @cindex processes, multiple
2293 On most systems, @value{GDBN} has no special support for debugging
2294 programs which create additional processes using the @code{fork}
2295 function. When a program forks, @value{GDBN} will continue to debug the
2296 parent process and the child process will run unimpeded. If you have
2297 set a breakpoint in any code which the child then executes, the child
2298 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2299 will cause it to terminate.
2301 However, if you want to debug the child process there is a workaround
2302 which isn't too painful. Put a call to @code{sleep} in the code which
2303 the child process executes after the fork. It may be useful to sleep
2304 only if a certain environment variable is set, or a certain file exists,
2305 so that the delay need not occur when you don't want to run @value{GDBN}
2306 on the child. While the child is sleeping, use the @code{ps} program to
2307 get its process ID. Then tell @value{GDBN} (a new invocation of
2308 @value{GDBN} if you are also debugging the parent process) to attach to
2309 the child process (@pxref{Attach}). From that point on you can debug
2310 the child process just like any other process which you attached to.
2312 On some systems, @value{GDBN} provides support for debugging programs that
2313 create additional processes using the @code{fork} or @code{vfork} functions.
2314 Currently, the only platforms with this feature are HP-UX (11.x and later
2315 only?) and GNU/Linux (kernel version 2.5.60 and later).
2317 By default, when a program forks, @value{GDBN} will continue to debug
2318 the parent process and the child process will run unimpeded.
2320 If you want to follow the child process instead of the parent process,
2321 use the command @w{@code{set follow-fork-mode}}.
2324 @kindex set follow-fork-mode
2325 @item set follow-fork-mode @var{mode}
2326 Set the debugger response to a program call of @code{fork} or
2327 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2328 process. The @var{mode} can be:
2332 The original process is debugged after a fork. The child process runs
2333 unimpeded. This is the default.
2336 The new process is debugged after a fork. The parent process runs
2341 @item show follow-fork-mode
2342 Display the current debugger response to a @code{fork} or @code{vfork} call.
2345 If you ask to debug a child process and a @code{vfork} is followed by an
2346 @code{exec}, @value{GDBN} executes the new target up to the first
2347 breakpoint in the new target. If you have a breakpoint set on
2348 @code{main} in your original program, the breakpoint will also be set on
2349 the child process's @code{main}.
2351 When a child process is spawned by @code{vfork}, you cannot debug the
2352 child or parent until an @code{exec} call completes.
2354 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2355 call executes, the new target restarts. To restart the parent process,
2356 use the @code{file} command with the parent executable name as its
2359 You can use the @code{catch} command to make @value{GDBN} stop whenever
2360 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2361 Catchpoints, ,Setting catchpoints}.
2364 @chapter Stopping and Continuing
2366 The principal purposes of using a debugger are so that you can stop your
2367 program before it terminates; or so that, if your program runs into
2368 trouble, you can investigate and find out why.
2370 Inside @value{GDBN}, your program may stop for any of several reasons,
2371 such as a signal, a breakpoint, or reaching a new line after a
2372 @value{GDBN} command such as @code{step}. You may then examine and
2373 change variables, set new breakpoints or remove old ones, and then
2374 continue execution. Usually, the messages shown by @value{GDBN} provide
2375 ample explanation of the status of your program---but you can also
2376 explicitly request this information at any time.
2379 @kindex info program
2381 Display information about the status of your program: whether it is
2382 running or not, what process it is, and why it stopped.
2386 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2387 * Continuing and Stepping:: Resuming execution
2389 * Thread Stops:: Stopping and starting multi-thread programs
2393 @section Breakpoints, watchpoints, and catchpoints
2396 A @dfn{breakpoint} makes your program stop whenever a certain point in
2397 the program is reached. For each breakpoint, you can add conditions to
2398 control in finer detail whether your program stops. You can set
2399 breakpoints with the @code{break} command and its variants (@pxref{Set
2400 Breaks, ,Setting breakpoints}), to specify the place where your program
2401 should stop by line number, function name or exact address in the
2404 In HP-UX, SunOS 4.x, SVR4, and Alpha OSF/1 configurations, you can set
2405 breakpoints in shared libraries before the executable is run. There is
2406 a minor limitation on HP-UX systems: you must wait until the executable
2407 is run in order to set breakpoints in shared library routines that are
2408 not called directly by the program (for example, routines that are
2409 arguments in a @code{pthread_create} call).
2412 @cindex memory tracing
2413 @cindex breakpoint on memory address
2414 @cindex breakpoint on variable modification
2415 A @dfn{watchpoint} is a special breakpoint that stops your program
2416 when the value of an expression changes. You must use a different
2417 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
2418 watchpoints}), but aside from that, you can manage a watchpoint like
2419 any other breakpoint: you enable, disable, and delete both breakpoints
2420 and watchpoints using the same commands.
2422 You can arrange to have values from your program displayed automatically
2423 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2427 @cindex breakpoint on events
2428 A @dfn{catchpoint} is another special breakpoint that stops your program
2429 when a certain kind of event occurs, such as the throwing of a C@t{++}
2430 exception or the loading of a library. As with watchpoints, you use a
2431 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2432 catchpoints}), but aside from that, you can manage a catchpoint like any
2433 other breakpoint. (To stop when your program receives a signal, use the
2434 @code{handle} command; see @ref{Signals, ,Signals}.)
2436 @cindex breakpoint numbers
2437 @cindex numbers for breakpoints
2438 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2439 catchpoint when you create it; these numbers are successive integers
2440 starting with one. In many of the commands for controlling various
2441 features of breakpoints you use the breakpoint number to say which
2442 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2443 @dfn{disabled}; if disabled, it has no effect on your program until you
2446 @cindex breakpoint ranges
2447 @cindex ranges of breakpoints
2448 Some @value{GDBN} commands accept a range of breakpoints on which to
2449 operate. A breakpoint range is either a single breakpoint number, like
2450 @samp{5}, or two such numbers, in increasing order, separated by a
2451 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2452 all breakpoint in that range are operated on.
2455 * Set Breaks:: Setting breakpoints
2456 * Set Watchpoints:: Setting watchpoints
2457 * Set Catchpoints:: Setting catchpoints
2458 * Delete Breaks:: Deleting breakpoints
2459 * Disabling:: Disabling breakpoints
2460 * Conditions:: Break conditions
2461 * Break Commands:: Breakpoint command lists
2462 * Breakpoint Menus:: Breakpoint menus
2463 * Error in Breakpoints:: ``Cannot insert breakpoints''
2464 * Breakpoint related warnings:: ``Breakpoint address adjusted...''
2468 @subsection Setting breakpoints
2470 @c FIXME LMB what does GDB do if no code on line of breakpt?
2471 @c consider in particular declaration with/without initialization.
2473 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2476 @kindex b @r{(@code{break})}
2477 @vindex $bpnum@r{, convenience variable}
2478 @cindex latest breakpoint
2479 Breakpoints are set with the @code{break} command (abbreviated
2480 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2481 number of the breakpoint you've set most recently; see @ref{Convenience
2482 Vars,, Convenience variables}, for a discussion of what you can do with
2483 convenience variables.
2485 You have several ways to say where the breakpoint should go.
2488 @item break @var{function}
2489 Set a breakpoint at entry to function @var{function}.
2490 When using source languages that permit overloading of symbols, such as
2491 C@t{++}, @var{function} may refer to more than one possible place to break.
2492 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2494 @item break +@var{offset}
2495 @itemx break -@var{offset}
2496 Set a breakpoint some number of lines forward or back from the position
2497 at which execution stopped in the currently selected @dfn{stack frame}.
2498 (@xref{Frames, ,Frames}, for a description of stack frames.)
2500 @item break @var{linenum}
2501 Set a breakpoint at line @var{linenum} in the current source file.
2502 The current source file is the last file whose source text was printed.
2503 The breakpoint will stop your program just before it executes any of the
2506 @item break @var{filename}:@var{linenum}
2507 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2509 @item break @var{filename}:@var{function}
2510 Set a breakpoint at entry to function @var{function} found in file
2511 @var{filename}. Specifying a file name as well as a function name is
2512 superfluous except when multiple files contain similarly named
2515 @item break *@var{address}
2516 Set a breakpoint at address @var{address}. You can use this to set
2517 breakpoints in parts of your program which do not have debugging
2518 information or source files.
2521 When called without any arguments, @code{break} sets a breakpoint at
2522 the next instruction to be executed in the selected stack frame
2523 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2524 innermost, this makes your program stop as soon as control
2525 returns to that frame. This is similar to the effect of a
2526 @code{finish} command in the frame inside the selected frame---except
2527 that @code{finish} does not leave an active breakpoint. If you use
2528 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2529 the next time it reaches the current location; this may be useful
2532 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2533 least one instruction has been executed. If it did not do this, you
2534 would be unable to proceed past a breakpoint without first disabling the
2535 breakpoint. This rule applies whether or not the breakpoint already
2536 existed when your program stopped.
2538 @item break @dots{} if @var{cond}
2539 Set a breakpoint with condition @var{cond}; evaluate the expression
2540 @var{cond} each time the breakpoint is reached, and stop only if the
2541 value is nonzero---that is, if @var{cond} evaluates as true.
2542 @samp{@dots{}} stands for one of the possible arguments described
2543 above (or no argument) specifying where to break. @xref{Conditions,
2544 ,Break conditions}, for more information on breakpoint conditions.
2547 @item tbreak @var{args}
2548 Set a breakpoint enabled only for one stop. @var{args} are the
2549 same as for the @code{break} command, and the breakpoint is set in the same
2550 way, but the breakpoint is automatically deleted after the first time your
2551 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2554 @item hbreak @var{args}
2555 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2556 @code{break} command and the breakpoint is set in the same way, but the
2557 breakpoint requires hardware support and some target hardware may not
2558 have this support. The main purpose of this is EPROM/ROM code
2559 debugging, so you can set a breakpoint at an instruction without
2560 changing the instruction. This can be used with the new trap-generation
2561 provided by SPARClite DSU and some x86-based targets. These targets
2562 will generate traps when a program accesses some data or instruction
2563 address that is assigned to the debug registers. However the hardware
2564 breakpoint registers can take a limited number of breakpoints. For
2565 example, on the DSU, only two data breakpoints can be set at a time, and
2566 @value{GDBN} will reject this command if more than two are used. Delete
2567 or disable unused hardware breakpoints before setting new ones
2568 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2569 @xref{set remote hardware-breakpoint-limit}.
2573 @item thbreak @var{args}
2574 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2575 are the same as for the @code{hbreak} command and the breakpoint is set in
2576 the same way. However, like the @code{tbreak} command,
2577 the breakpoint is automatically deleted after the
2578 first time your program stops there. Also, like the @code{hbreak}
2579 command, the breakpoint requires hardware support and some target hardware
2580 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2581 See also @ref{Conditions, ,Break conditions}.
2584 @cindex regular expression
2585 @item rbreak @var{regex}
2586 Set breakpoints on all functions matching the regular expression
2587 @var{regex}. This command sets an unconditional breakpoint on all
2588 matches, printing a list of all breakpoints it set. Once these
2589 breakpoints are set, they are treated just like the breakpoints set with
2590 the @code{break} command. You can delete them, disable them, or make
2591 them conditional the same way as any other breakpoint.
2593 The syntax of the regular expression is the standard one used with tools
2594 like @file{grep}. Note that this is different from the syntax used by
2595 shells, so for instance @code{foo*} matches all functions that include
2596 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2597 @code{.*} leading and trailing the regular expression you supply, so to
2598 match only functions that begin with @code{foo}, use @code{^foo}.
2600 @cindex non-member C@t{++} functions, set breakpoint in
2601 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2602 breakpoints on overloaded functions that are not members of any special
2605 @cindex set breakpoints on all functions
2606 The @code{rbreak} command can be used to set breakpoints in
2607 @strong{all} the functions in a program, like this:
2610 (@value{GDBP}) rbreak .
2613 @kindex info breakpoints
2614 @cindex @code{$_} and @code{info breakpoints}
2615 @item info breakpoints @r{[}@var{n}@r{]}
2616 @itemx info break @r{[}@var{n}@r{]}
2617 @itemx info watchpoints @r{[}@var{n}@r{]}
2618 Print a table of all breakpoints, watchpoints, and catchpoints set and
2619 not deleted, with the following columns for each breakpoint:
2622 @item Breakpoint Numbers
2624 Breakpoint, watchpoint, or catchpoint.
2626 Whether the breakpoint is marked to be disabled or deleted when hit.
2627 @item Enabled or Disabled
2628 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2629 that are not enabled.
2631 Where the breakpoint is in your program, as a memory address. If the
2632 breakpoint is pending (see below for details) on a future load of a shared library, the address
2633 will be listed as @samp{<PENDING>}.
2635 Where the breakpoint is in the source for your program, as a file and
2636 line number. For a pending breakpoint, the original string passed to
2637 the breakpoint command will be listed as it cannot be resolved until
2638 the appropriate shared library is loaded in the future.
2642 If a breakpoint is conditional, @code{info break} shows the condition on
2643 the line following the affected breakpoint; breakpoint commands, if any,
2644 are listed after that. A pending breakpoint is allowed to have a condition
2645 specified for it. The condition is not parsed for validity until a shared
2646 library is loaded that allows the pending breakpoint to resolve to a
2650 @code{info break} with a breakpoint
2651 number @var{n} as argument lists only that breakpoint. The
2652 convenience variable @code{$_} and the default examining-address for
2653 the @code{x} command are set to the address of the last breakpoint
2654 listed (@pxref{Memory, ,Examining memory}).
2657 @code{info break} displays a count of the number of times the breakpoint
2658 has been hit. This is especially useful in conjunction with the
2659 @code{ignore} command. You can ignore a large number of breakpoint
2660 hits, look at the breakpoint info to see how many times the breakpoint
2661 was hit, and then run again, ignoring one less than that number. This
2662 will get you quickly to the last hit of that breakpoint.
2665 @value{GDBN} allows you to set any number of breakpoints at the same place in
2666 your program. There is nothing silly or meaningless about this. When
2667 the breakpoints are conditional, this is even useful
2668 (@pxref{Conditions, ,Break conditions}).
2670 @cindex pending breakpoints
2671 If a specified breakpoint location cannot be found, it may be due to the fact
2672 that the location is in a shared library that is yet to be loaded. In such
2673 a case, you may want @value{GDBN} to create a special breakpoint (known as
2674 a @dfn{pending breakpoint}) that
2675 attempts to resolve itself in the future when an appropriate shared library
2678 Pending breakpoints are useful to set at the start of your
2679 @value{GDBN} session for locations that you know will be dynamically loaded
2680 later by the program being debugged. When shared libraries are loaded,
2681 a check is made to see if the load resolves any pending breakpoint locations.
2682 If a pending breakpoint location gets resolved,
2683 a regular breakpoint is created and the original pending breakpoint is removed.
2685 @value{GDBN} provides some additional commands for controlling pending
2688 @kindex set breakpoint pending
2689 @kindex show breakpoint pending
2691 @item set breakpoint pending auto
2692 This is the default behavior. When @value{GDBN} cannot find the breakpoint
2693 location, it queries you whether a pending breakpoint should be created.
2695 @item set breakpoint pending on
2696 This indicates that an unrecognized breakpoint location should automatically
2697 result in a pending breakpoint being created.
2699 @item set breakpoint pending off
2700 This indicates that pending breakpoints are not to be created. Any
2701 unrecognized breakpoint location results in an error. This setting does
2702 not affect any pending breakpoints previously created.
2704 @item show breakpoint pending
2705 Show the current behavior setting for creating pending breakpoints.
2708 @cindex operations allowed on pending breakpoints
2709 Normal breakpoint operations apply to pending breakpoints as well. You may
2710 specify a condition for a pending breakpoint and/or commands to run when the
2711 breakpoint is reached. You can also enable or disable
2712 the pending breakpoint. When you specify a condition for a pending breakpoint,
2713 the parsing of the condition will be deferred until the point where the
2714 pending breakpoint location is resolved. Disabling a pending breakpoint
2715 tells @value{GDBN} to not attempt to resolve the breakpoint on any subsequent
2716 shared library load. When a pending breakpoint is re-enabled,
2717 @value{GDBN} checks to see if the location is already resolved.
2718 This is done because any number of shared library loads could have
2719 occurred since the time the breakpoint was disabled and one or more
2720 of these loads could resolve the location.
2722 @cindex negative breakpoint numbers
2723 @cindex internal @value{GDBN} breakpoints
2724 @value{GDBN} itself sometimes sets breakpoints in your program for
2725 special purposes, such as proper handling of @code{longjmp} (in C
2726 programs). These internal breakpoints are assigned negative numbers,
2727 starting with @code{-1}; @samp{info breakpoints} does not display them.
2728 You can see these breakpoints with the @value{GDBN} maintenance command
2729 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
2732 @node Set Watchpoints
2733 @subsection Setting watchpoints
2735 @cindex setting watchpoints
2736 @cindex software watchpoints
2737 @cindex hardware watchpoints
2738 You can use a watchpoint to stop execution whenever the value of an
2739 expression changes, without having to predict a particular place where
2742 Depending on your system, watchpoints may be implemented in software or
2743 hardware. @value{GDBN} does software watchpointing by single-stepping your
2744 program and testing the variable's value each time, which is hundreds of
2745 times slower than normal execution. (But this may still be worth it, to
2746 catch errors where you have no clue what part of your program is the
2749 On some systems, such as HP-UX, @sc{gnu}/Linux and some other x86-based targets,
2750 @value{GDBN} includes support for
2751 hardware watchpoints, which do not slow down the running of your
2756 @item watch @var{expr}
2757 Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
2758 is written into by the program and its value changes.
2761 @item rwatch @var{expr}
2762 Set a watchpoint that will break when watch @var{expr} is read by the program.
2765 @item awatch @var{expr}
2766 Set a watchpoint that will break when @var{expr} is either read or written into
2769 @kindex info watchpoints
2770 @item info watchpoints
2771 This command prints a list of watchpoints, breakpoints, and catchpoints;
2772 it is the same as @code{info break}.
2775 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
2776 watchpoints execute very quickly, and the debugger reports a change in
2777 value at the exact instruction where the change occurs. If @value{GDBN}
2778 cannot set a hardware watchpoint, it sets a software watchpoint, which
2779 executes more slowly and reports the change in value at the next
2780 statement, not the instruction, after the change occurs.
2782 When you issue the @code{watch} command, @value{GDBN} reports
2785 Hardware watchpoint @var{num}: @var{expr}
2789 if it was able to set a hardware watchpoint.
2791 Currently, the @code{awatch} and @code{rwatch} commands can only set
2792 hardware watchpoints, because accesses to data that don't change the
2793 value of the watched expression cannot be detected without examining
2794 every instruction as it is being executed, and @value{GDBN} does not do
2795 that currently. If @value{GDBN} finds that it is unable to set a
2796 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
2797 will print a message like this:
2800 Expression cannot be implemented with read/access watchpoint.
2803 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
2804 data type of the watched expression is wider than what a hardware
2805 watchpoint on the target machine can handle. For example, some systems
2806 can only watch regions that are up to 4 bytes wide; on such systems you
2807 cannot set hardware watchpoints for an expression that yields a
2808 double-precision floating-point number (which is typically 8 bytes
2809 wide). As a work-around, it might be possible to break the large region
2810 into a series of smaller ones and watch them with separate watchpoints.
2812 If you set too many hardware watchpoints, @value{GDBN} might be unable
2813 to insert all of them when you resume the execution of your program.
2814 Since the precise number of active watchpoints is unknown until such
2815 time as the program is about to be resumed, @value{GDBN} might not be
2816 able to warn you about this when you set the watchpoints, and the
2817 warning will be printed only when the program is resumed:
2820 Hardware watchpoint @var{num}: Could not insert watchpoint
2824 If this happens, delete or disable some of the watchpoints.
2826 The SPARClite DSU will generate traps when a program accesses some data
2827 or instruction address that is assigned to the debug registers. For the
2828 data addresses, DSU facilitates the @code{watch} command. However the
2829 hardware breakpoint registers can only take two data watchpoints, and
2830 both watchpoints must be the same kind. For example, you can set two
2831 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
2832 @strong{or} two with @code{awatch} commands, but you cannot set one
2833 watchpoint with one command and the other with a different command.
2834 @value{GDBN} will reject the command if you try to mix watchpoints.
2835 Delete or disable unused watchpoint commands before setting new ones.
2837 If you call a function interactively using @code{print} or @code{call},
2838 any watchpoints you have set will be inactive until @value{GDBN} reaches another
2839 kind of breakpoint or the call completes.
2841 @value{GDBN} automatically deletes watchpoints that watch local
2842 (automatic) variables, or expressions that involve such variables, when
2843 they go out of scope, that is, when the execution leaves the block in
2844 which these variables were defined. In particular, when the program
2845 being debugged terminates, @emph{all} local variables go out of scope,
2846 and so only watchpoints that watch global variables remain set. If you
2847 rerun the program, you will need to set all such watchpoints again. One
2848 way of doing that would be to set a code breakpoint at the entry to the
2849 @code{main} function and when it breaks, set all the watchpoints.
2852 @cindex watchpoints and threads
2853 @cindex threads and watchpoints
2854 @emph{Warning:} In multi-thread programs, watchpoints have only limited
2855 usefulness. With the current watchpoint implementation, @value{GDBN}
2856 can only watch the value of an expression @emph{in a single thread}. If
2857 you are confident that the expression can only change due to the current
2858 thread's activity (and if you are also confident that no other thread
2859 can become current), then you can use watchpoints as usual. However,
2860 @value{GDBN} may not notice when a non-current thread's activity changes
2863 @c FIXME: this is almost identical to the previous paragraph.
2864 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
2865 have only limited usefulness. If @value{GDBN} creates a software
2866 watchpoint, it can only watch the value of an expression @emph{in a
2867 single thread}. If you are confident that the expression can only
2868 change due to the current thread's activity (and if you are also
2869 confident that no other thread can become current), then you can use
2870 software watchpoints as usual. However, @value{GDBN} may not notice
2871 when a non-current thread's activity changes the expression. (Hardware
2872 watchpoints, in contrast, watch an expression in all threads.)
2875 @xref{set remote hardware-watchpoint-limit}.
2877 @node Set Catchpoints
2878 @subsection Setting catchpoints
2879 @cindex catchpoints, setting
2880 @cindex exception handlers
2881 @cindex event handling
2883 You can use @dfn{catchpoints} to cause the debugger to stop for certain
2884 kinds of program events, such as C@t{++} exceptions or the loading of a
2885 shared library. Use the @code{catch} command to set a catchpoint.
2889 @item catch @var{event}
2890 Stop when @var{event} occurs. @var{event} can be any of the following:
2893 @cindex stop on C@t{++} exceptions
2894 The throwing of a C@t{++} exception.
2897 The catching of a C@t{++} exception.
2900 @cindex break on fork/exec
2901 A call to @code{exec}. This is currently only available for HP-UX.
2904 A call to @code{fork}. This is currently only available for HP-UX.
2907 A call to @code{vfork}. This is currently only available for HP-UX.
2910 @itemx load @var{libname}
2911 @cindex break on load/unload of shared library
2912 The dynamic loading of any shared library, or the loading of the library
2913 @var{libname}. This is currently only available for HP-UX.
2916 @itemx unload @var{libname}
2917 The unloading of any dynamically loaded shared library, or the unloading
2918 of the library @var{libname}. This is currently only available for HP-UX.
2921 @item tcatch @var{event}
2922 Set a catchpoint that is enabled only for one stop. The catchpoint is
2923 automatically deleted after the first time the event is caught.
2927 Use the @code{info break} command to list the current catchpoints.
2929 There are currently some limitations to C@t{++} exception handling
2930 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
2934 If you call a function interactively, @value{GDBN} normally returns
2935 control to you when the function has finished executing. If the call
2936 raises an exception, however, the call may bypass the mechanism that
2937 returns control to you and cause your program either to abort or to
2938 simply continue running until it hits a breakpoint, catches a signal
2939 that @value{GDBN} is listening for, or exits. This is the case even if
2940 you set a catchpoint for the exception; catchpoints on exceptions are
2941 disabled within interactive calls.
2944 You cannot raise an exception interactively.
2947 You cannot install an exception handler interactively.
2950 @cindex raise exceptions
2951 Sometimes @code{catch} is not the best way to debug exception handling:
2952 if you need to know exactly where an exception is raised, it is better to
2953 stop @emph{before} the exception handler is called, since that way you
2954 can see the stack before any unwinding takes place. If you set a
2955 breakpoint in an exception handler instead, it may not be easy to find
2956 out where the exception was raised.
2958 To stop just before an exception handler is called, you need some
2959 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
2960 raised by calling a library function named @code{__raise_exception}
2961 which has the following ANSI C interface:
2964 /* @var{addr} is where the exception identifier is stored.
2965 @var{id} is the exception identifier. */
2966 void __raise_exception (void **addr, void *id);
2970 To make the debugger catch all exceptions before any stack
2971 unwinding takes place, set a breakpoint on @code{__raise_exception}
2972 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
2974 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
2975 that depends on the value of @var{id}, you can stop your program when
2976 a specific exception is raised. You can use multiple conditional
2977 breakpoints to stop your program when any of a number of exceptions are
2982 @subsection Deleting breakpoints
2984 @cindex clearing breakpoints, watchpoints, catchpoints
2985 @cindex deleting breakpoints, watchpoints, catchpoints
2986 It is often necessary to eliminate a breakpoint, watchpoint, or
2987 catchpoint once it has done its job and you no longer want your program
2988 to stop there. This is called @dfn{deleting} the breakpoint. A
2989 breakpoint that has been deleted no longer exists; it is forgotten.
2991 With the @code{clear} command you can delete breakpoints according to
2992 where they are in your program. With the @code{delete} command you can
2993 delete individual breakpoints, watchpoints, or catchpoints by specifying
2994 their breakpoint numbers.
2996 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
2997 automatically ignores breakpoints on the first instruction to be executed
2998 when you continue execution without changing the execution address.
3003 Delete any breakpoints at the next instruction to be executed in the
3004 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
3005 the innermost frame is selected, this is a good way to delete a
3006 breakpoint where your program just stopped.
3008 @item clear @var{function}
3009 @itemx clear @var{filename}:@var{function}
3010 Delete any breakpoints set at entry to the function @var{function}.
3012 @item clear @var{linenum}
3013 @itemx clear @var{filename}:@var{linenum}
3014 Delete any breakpoints set at or within the code of the specified line.
3016 @cindex delete breakpoints
3018 @kindex d @r{(@code{delete})}
3019 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3020 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3021 ranges specified as arguments. If no argument is specified, delete all
3022 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3023 confirm off}). You can abbreviate this command as @code{d}.
3027 @subsection Disabling breakpoints
3029 @cindex enable/disable a breakpoint
3030 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3031 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3032 it had been deleted, but remembers the information on the breakpoint so
3033 that you can @dfn{enable} it again later.
3035 You disable and enable breakpoints, watchpoints, and catchpoints with
3036 the @code{enable} and @code{disable} commands, optionally specifying one
3037 or more breakpoint numbers as arguments. Use @code{info break} or
3038 @code{info watch} to print a list of breakpoints, watchpoints, and
3039 catchpoints if you do not know which numbers to use.
3041 A breakpoint, watchpoint, or catchpoint can have any of four different
3042 states of enablement:
3046 Enabled. The breakpoint stops your program. A breakpoint set
3047 with the @code{break} command starts out in this state.
3049 Disabled. The breakpoint has no effect on your program.
3051 Enabled once. The breakpoint stops your program, but then becomes
3054 Enabled for deletion. The breakpoint stops your program, but
3055 immediately after it does so it is deleted permanently. A breakpoint
3056 set with the @code{tbreak} command starts out in this state.
3059 You can use the following commands to enable or disable breakpoints,
3060 watchpoints, and catchpoints:
3064 @kindex dis @r{(@code{disable})}
3065 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3066 Disable the specified breakpoints---or all breakpoints, if none are
3067 listed. A disabled breakpoint has no effect but is not forgotten. All
3068 options such as ignore-counts, conditions and commands are remembered in
3069 case the breakpoint is enabled again later. You may abbreviate
3070 @code{disable} as @code{dis}.
3073 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3074 Enable the specified breakpoints (or all defined breakpoints). They
3075 become effective once again in stopping your program.
3077 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3078 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3079 of these breakpoints immediately after stopping your program.
3081 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3082 Enable the specified breakpoints to work once, then die. @value{GDBN}
3083 deletes any of these breakpoints as soon as your program stops there.
3086 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3087 @c confusing: tbreak is also initially enabled.
3088 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3089 ,Setting breakpoints}), breakpoints that you set are initially enabled;
3090 subsequently, they become disabled or enabled only when you use one of
3091 the commands above. (The command @code{until} can set and delete a
3092 breakpoint of its own, but it does not change the state of your other
3093 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3097 @subsection Break conditions
3098 @cindex conditional breakpoints
3099 @cindex breakpoint conditions
3101 @c FIXME what is scope of break condition expr? Context where wanted?
3102 @c in particular for a watchpoint?
3103 The simplest sort of breakpoint breaks every time your program reaches a
3104 specified place. You can also specify a @dfn{condition} for a
3105 breakpoint. A condition is just a Boolean expression in your
3106 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3107 a condition evaluates the expression each time your program reaches it,
3108 and your program stops only if the condition is @emph{true}.
3110 This is the converse of using assertions for program validation; in that
3111 situation, you want to stop when the assertion is violated---that is,
3112 when the condition is false. In C, if you want to test an assertion expressed
3113 by the condition @var{assert}, you should set the condition
3114 @samp{! @var{assert}} on the appropriate breakpoint.
3116 Conditions are also accepted for watchpoints; you may not need them,
3117 since a watchpoint is inspecting the value of an expression anyhow---but
3118 it might be simpler, say, to just set a watchpoint on a variable name,
3119 and specify a condition that tests whether the new value is an interesting
3122 Break conditions can have side effects, and may even call functions in
3123 your program. This can be useful, for example, to activate functions
3124 that log program progress, or to use your own print functions to
3125 format special data structures. The effects are completely predictable
3126 unless there is another enabled breakpoint at the same address. (In
3127 that case, @value{GDBN} might see the other breakpoint first and stop your
3128 program without checking the condition of this one.) Note that
3129 breakpoint commands are usually more convenient and flexible than break
3131 purpose of performing side effects when a breakpoint is reached
3132 (@pxref{Break Commands, ,Breakpoint command lists}).
3134 Break conditions can be specified when a breakpoint is set, by using
3135 @samp{if} in the arguments to the @code{break} command. @xref{Set
3136 Breaks, ,Setting breakpoints}. They can also be changed at any time
3137 with the @code{condition} command.
3139 You can also use the @code{if} keyword with the @code{watch} command.
3140 The @code{catch} command does not recognize the @code{if} keyword;
3141 @code{condition} is the only way to impose a further condition on a
3146 @item condition @var{bnum} @var{expression}
3147 Specify @var{expression} as the break condition for breakpoint,
3148 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3149 breakpoint @var{bnum} stops your program only if the value of
3150 @var{expression} is true (nonzero, in C). When you use
3151 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3152 syntactic correctness, and to determine whether symbols in it have
3153 referents in the context of your breakpoint. If @var{expression} uses
3154 symbols not referenced in the context of the breakpoint, @value{GDBN}
3155 prints an error message:
3158 No symbol "foo" in current context.
3163 not actually evaluate @var{expression} at the time the @code{condition}
3164 command (or a command that sets a breakpoint with a condition, like
3165 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3167 @item condition @var{bnum}
3168 Remove the condition from breakpoint number @var{bnum}. It becomes
3169 an ordinary unconditional breakpoint.
3172 @cindex ignore count (of breakpoint)
3173 A special case of a breakpoint condition is to stop only when the
3174 breakpoint has been reached a certain number of times. This is so
3175 useful that there is a special way to do it, using the @dfn{ignore
3176 count} of the breakpoint. Every breakpoint has an ignore count, which
3177 is an integer. Most of the time, the ignore count is zero, and
3178 therefore has no effect. But if your program reaches a breakpoint whose
3179 ignore count is positive, then instead of stopping, it just decrements
3180 the ignore count by one and continues. As a result, if the ignore count
3181 value is @var{n}, the breakpoint does not stop the next @var{n} times
3182 your program reaches it.
3186 @item ignore @var{bnum} @var{count}
3187 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3188 The next @var{count} times the breakpoint is reached, your program's
3189 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3192 To make the breakpoint stop the next time it is reached, specify
3195 When you use @code{continue} to resume execution of your program from a
3196 breakpoint, you can specify an ignore count directly as an argument to
3197 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3198 Stepping,,Continuing and stepping}.
3200 If a breakpoint has a positive ignore count and a condition, the
3201 condition is not checked. Once the ignore count reaches zero,
3202 @value{GDBN} resumes checking the condition.
3204 You could achieve the effect of the ignore count with a condition such
3205 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3206 is decremented each time. @xref{Convenience Vars, ,Convenience
3210 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3213 @node Break Commands
3214 @subsection Breakpoint command lists
3216 @cindex breakpoint commands
3217 You can give any breakpoint (or watchpoint or catchpoint) a series of
3218 commands to execute when your program stops due to that breakpoint. For
3219 example, you might want to print the values of certain expressions, or
3220 enable other breakpoints.
3225 @item commands @r{[}@var{bnum}@r{]}
3226 @itemx @dots{} @var{command-list} @dots{}
3228 Specify a list of commands for breakpoint number @var{bnum}. The commands
3229 themselves appear on the following lines. Type a line containing just
3230 @code{end} to terminate the commands.
3232 To remove all commands from a breakpoint, type @code{commands} and
3233 follow it immediately with @code{end}; that is, give no commands.
3235 With no @var{bnum} argument, @code{commands} refers to the last
3236 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3237 recently encountered).
3240 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3241 disabled within a @var{command-list}.
3243 You can use breakpoint commands to start your program up again. Simply
3244 use the @code{continue} command, or @code{step}, or any other command
3245 that resumes execution.
3247 Any other commands in the command list, after a command that resumes
3248 execution, are ignored. This is because any time you resume execution
3249 (even with a simple @code{next} or @code{step}), you may encounter
3250 another breakpoint---which could have its own command list, leading to
3251 ambiguities about which list to execute.
3254 If the first command you specify in a command list is @code{silent}, the
3255 usual message about stopping at a breakpoint is not printed. This may
3256 be desirable for breakpoints that are to print a specific message and
3257 then continue. If none of the remaining commands print anything, you
3258 see no sign that the breakpoint was reached. @code{silent} is
3259 meaningful only at the beginning of a breakpoint command list.
3261 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3262 print precisely controlled output, and are often useful in silent
3263 breakpoints. @xref{Output, ,Commands for controlled output}.
3265 For example, here is how you could use breakpoint commands to print the
3266 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3272 printf "x is %d\n",x
3277 One application for breakpoint commands is to compensate for one bug so
3278 you can test for another. Put a breakpoint just after the erroneous line
3279 of code, give it a condition to detect the case in which something
3280 erroneous has been done, and give it commands to assign correct values
3281 to any variables that need them. End with the @code{continue} command
3282 so that your program does not stop, and start with the @code{silent}
3283 command so that no output is produced. Here is an example:
3294 @node Breakpoint Menus
3295 @subsection Breakpoint menus
3297 @cindex symbol overloading
3299 Some programming languages (notably C@t{++} and Objective-C) permit a
3300 single function name
3301 to be defined several times, for application in different contexts.
3302 This is called @dfn{overloading}. When a function name is overloaded,
3303 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3304 a breakpoint. If you realize this is a problem, you can use
3305 something like @samp{break @var{function}(@var{types})} to specify which
3306 particular version of the function you want. Otherwise, @value{GDBN} offers
3307 you a menu of numbered choices for different possible breakpoints, and
3308 waits for your selection with the prompt @samp{>}. The first two
3309 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3310 sets a breakpoint at each definition of @var{function}, and typing
3311 @kbd{0} aborts the @code{break} command without setting any new
3314 For example, the following session excerpt shows an attempt to set a
3315 breakpoint at the overloaded symbol @code{String::after}.
3316 We choose three particular definitions of that function name:
3318 @c FIXME! This is likely to change to show arg type lists, at least
3321 (@value{GDBP}) b String::after
3324 [2] file:String.cc; line number:867
3325 [3] file:String.cc; line number:860
3326 [4] file:String.cc; line number:875
3327 [5] file:String.cc; line number:853
3328 [6] file:String.cc; line number:846
3329 [7] file:String.cc; line number:735
3331 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3332 Breakpoint 2 at 0xb344: file String.cc, line 875.
3333 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3334 Multiple breakpoints were set.
3335 Use the "delete" command to delete unwanted
3341 @c @ifclear BARETARGET
3342 @node Error in Breakpoints
3343 @subsection ``Cannot insert breakpoints''
3345 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3347 Under some operating systems, breakpoints cannot be used in a program if
3348 any other process is running that program. In this situation,
3349 attempting to run or continue a program with a breakpoint causes
3350 @value{GDBN} to print an error message:
3353 Cannot insert breakpoints.
3354 The same program may be running in another process.
3357 When this happens, you have three ways to proceed:
3361 Remove or disable the breakpoints, then continue.
3364 Suspend @value{GDBN}, and copy the file containing your program to a new
3365 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3366 that @value{GDBN} should run your program under that name.
3367 Then start your program again.
3370 Relink your program so that the text segment is nonsharable, using the
3371 linker option @samp{-N}. The operating system limitation may not apply
3372 to nonsharable executables.
3376 A similar message can be printed if you request too many active
3377 hardware-assisted breakpoints and watchpoints:
3379 @c FIXME: the precise wording of this message may change; the relevant
3380 @c source change is not committed yet (Sep 3, 1999).
3382 Stopped; cannot insert breakpoints.
3383 You may have requested too many hardware breakpoints and watchpoints.
3387 This message is printed when you attempt to resume the program, since
3388 only then @value{GDBN} knows exactly how many hardware breakpoints and
3389 watchpoints it needs to insert.
3391 When this message is printed, you need to disable or remove some of the
3392 hardware-assisted breakpoints and watchpoints, and then continue.
3394 @node Breakpoint related warnings
3395 @subsection ``Breakpoint address adjusted...''
3396 @cindex breakpoint address adjusted
3398 Some processor architectures place constraints on the addresses at
3399 which breakpoints may be placed. For architectures thus constrained,
3400 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3401 with the constraints dictated by the architecture.
3403 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3404 a VLIW architecture in which a number of RISC-like instructions may be
3405 bundled together for parallel execution. The FR-V architecture
3406 constrains the location of a breakpoint instruction within such a
3407 bundle to the instruction with the lowest address. @value{GDBN}
3408 honors this constraint by adjusting a breakpoint's address to the
3409 first in the bundle.
3411 It is not uncommon for optimized code to have bundles which contain
3412 instructions from different source statements, thus it may happen that
3413 a breakpoint's address will be adjusted from one source statement to
3414 another. Since this adjustment may significantly alter @value{GDBN}'s
3415 breakpoint related behavior from what the user expects, a warning is
3416 printed when the breakpoint is first set and also when the breakpoint
3419 A warning like the one below is printed when setting a breakpoint
3420 that's been subject to address adjustment:
3423 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3426 Such warnings are printed both for user settable and @value{GDBN}'s
3427 internal breakpoints. If you see one of these warnings, you should
3428 verify that a breakpoint set at the adjusted address will have the
3429 desired affect. If not, the breakpoint in question may be removed and
3430 other breakpoints may be set which will have the desired behavior.
3431 E.g., it may be sufficient to place the breakpoint at a later
3432 instruction. A conditional breakpoint may also be useful in some
3433 cases to prevent the breakpoint from triggering too often.
3435 @value{GDBN} will also issue a warning when stopping at one of these
3436 adjusted breakpoints:
3439 warning: Breakpoint 1 address previously adjusted from 0x00010414
3443 When this warning is encountered, it may be too late to take remedial
3444 action except in cases where the breakpoint is hit earlier or more
3445 frequently than expected.
3447 @node Continuing and Stepping
3448 @section Continuing and stepping
3452 @cindex resuming execution
3453 @dfn{Continuing} means resuming program execution until your program
3454 completes normally. In contrast, @dfn{stepping} means executing just
3455 one more ``step'' of your program, where ``step'' may mean either one
3456 line of source code, or one machine instruction (depending on what
3457 particular command you use). Either when continuing or when stepping,
3458 your program may stop even sooner, due to a breakpoint or a signal. (If
3459 it stops due to a signal, you may want to use @code{handle}, or use
3460 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3464 @kindex c @r{(@code{continue})}
3465 @kindex fg @r{(resume foreground execution)}
3466 @item continue @r{[}@var{ignore-count}@r{]}
3467 @itemx c @r{[}@var{ignore-count}@r{]}
3468 @itemx fg @r{[}@var{ignore-count}@r{]}
3469 Resume program execution, at the address where your program last stopped;
3470 any breakpoints set at that address are bypassed. The optional argument
3471 @var{ignore-count} allows you to specify a further number of times to
3472 ignore a breakpoint at this location; its effect is like that of
3473 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3475 The argument @var{ignore-count} is meaningful only when your program
3476 stopped due to a breakpoint. At other times, the argument to
3477 @code{continue} is ignored.
3479 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3480 debugged program is deemed to be the foreground program) are provided
3481 purely for convenience, and have exactly the same behavior as
3485 To resume execution at a different place, you can use @code{return}
3486 (@pxref{Returning, ,Returning from a function}) to go back to the
3487 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3488 different address}) to go to an arbitrary location in your program.
3490 A typical technique for using stepping is to set a breakpoint
3491 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3492 beginning of the function or the section of your program where a problem
3493 is believed to lie, run your program until it stops at that breakpoint,
3494 and then step through the suspect area, examining the variables that are
3495 interesting, until you see the problem happen.
3499 @kindex s @r{(@code{step})}
3501 Continue running your program until control reaches a different source
3502 line, then stop it and return control to @value{GDBN}. This command is
3503 abbreviated @code{s}.
3506 @c "without debugging information" is imprecise; actually "without line
3507 @c numbers in the debugging information". (gcc -g1 has debugging info but
3508 @c not line numbers). But it seems complex to try to make that
3509 @c distinction here.
3510 @emph{Warning:} If you use the @code{step} command while control is
3511 within a function that was compiled without debugging information,
3512 execution proceeds until control reaches a function that does have
3513 debugging information. Likewise, it will not step into a function which
3514 is compiled without debugging information. To step through functions
3515 without debugging information, use the @code{stepi} command, described
3519 The @code{step} command only stops at the first instruction of a source
3520 line. This prevents the multiple stops that could otherwise occur in
3521 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3522 to stop if a function that has debugging information is called within
3523 the line. In other words, @code{step} @emph{steps inside} any functions
3524 called within the line.
3526 Also, the @code{step} command only enters a function if there is line
3527 number information for the function. Otherwise it acts like the
3528 @code{next} command. This avoids problems when using @code{cc -gl}
3529 on MIPS machines. Previously, @code{step} entered subroutines if there
3530 was any debugging information about the routine.
3532 @item step @var{count}
3533 Continue running as in @code{step}, but do so @var{count} times. If a
3534 breakpoint is reached, or a signal not related to stepping occurs before
3535 @var{count} steps, stepping stops right away.
3538 @kindex n @r{(@code{next})}
3539 @item next @r{[}@var{count}@r{]}
3540 Continue to the next source line in the current (innermost) stack frame.
3541 This is similar to @code{step}, but function calls that appear within
3542 the line of code are executed without stopping. Execution stops when
3543 control reaches a different line of code at the original stack level
3544 that was executing when you gave the @code{next} command. This command
3545 is abbreviated @code{n}.
3547 An argument @var{count} is a repeat count, as for @code{step}.
3550 @c FIX ME!! Do we delete this, or is there a way it fits in with
3551 @c the following paragraph? --- Vctoria
3553 @c @code{next} within a function that lacks debugging information acts like
3554 @c @code{step}, but any function calls appearing within the code of the
3555 @c function are executed without stopping.
3557 The @code{next} command only stops at the first instruction of a
3558 source line. This prevents multiple stops that could otherwise occur in
3559 @code{switch} statements, @code{for} loops, etc.
3561 @kindex set step-mode
3563 @cindex functions without line info, and stepping
3564 @cindex stepping into functions with no line info
3565 @itemx set step-mode on
3566 The @code{set step-mode on} command causes the @code{step} command to
3567 stop at the first instruction of a function which contains no debug line
3568 information rather than stepping over it.
3570 This is useful in cases where you may be interested in inspecting the
3571 machine instructions of a function which has no symbolic info and do not
3572 want @value{GDBN} to automatically skip over this function.
3574 @item set step-mode off
3575 Causes the @code{step} command to step over any functions which contains no
3576 debug information. This is the default.
3580 Continue running until just after function in the selected stack frame
3581 returns. Print the returned value (if any).
3583 Contrast this with the @code{return} command (@pxref{Returning,
3584 ,Returning from a function}).
3587 @kindex u @r{(@code{until})}
3590 Continue running until a source line past the current line, in the
3591 current stack frame, is reached. This command is used to avoid single
3592 stepping through a loop more than once. It is like the @code{next}
3593 command, except that when @code{until} encounters a jump, it
3594 automatically continues execution until the program counter is greater
3595 than the address of the jump.
3597 This means that when you reach the end of a loop after single stepping
3598 though it, @code{until} makes your program continue execution until it
3599 exits the loop. In contrast, a @code{next} command at the end of a loop
3600 simply steps back to the beginning of the loop, which forces you to step
3601 through the next iteration.
3603 @code{until} always stops your program if it attempts to exit the current
3606 @code{until} may produce somewhat counterintuitive results if the order
3607 of machine code does not match the order of the source lines. For
3608 example, in the following excerpt from a debugging session, the @code{f}
3609 (@code{frame}) command shows that execution is stopped at line
3610 @code{206}; yet when we use @code{until}, we get to line @code{195}:
3614 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
3616 (@value{GDBP}) until
3617 195 for ( ; argc > 0; NEXTARG) @{
3620 This happened because, for execution efficiency, the compiler had
3621 generated code for the loop closure test at the end, rather than the
3622 start, of the loop---even though the test in a C @code{for}-loop is
3623 written before the body of the loop. The @code{until} command appeared
3624 to step back to the beginning of the loop when it advanced to this
3625 expression; however, it has not really gone to an earlier
3626 statement---not in terms of the actual machine code.
3628 @code{until} with no argument works by means of single
3629 instruction stepping, and hence is slower than @code{until} with an
3632 @item until @var{location}
3633 @itemx u @var{location}
3634 Continue running your program until either the specified location is
3635 reached, or the current stack frame returns. @var{location} is any of
3636 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
3637 ,Setting breakpoints}). This form of the command uses breakpoints, and
3638 hence is quicker than @code{until} without an argument. The specified
3639 location is actually reached only if it is in the current frame. This
3640 implies that @code{until} can be used to skip over recursive function
3641 invocations. For instance in the code below, if the current location is
3642 line @code{96}, issuing @code{until 99} will execute the program up to
3643 line @code{99} in the same invocation of factorial, i.e. after the inner
3644 invocations have returned.
3647 94 int factorial (int value)
3649 96 if (value > 1) @{
3650 97 value *= factorial (value - 1);
3657 @kindex advance @var{location}
3658 @itemx advance @var{location}
3659 Continue running the program up to the given location. An argument is
3660 required, anything of the same form as arguments for the @code{break}
3661 command. Execution will also stop upon exit from the current stack
3662 frame. This command is similar to @code{until}, but @code{advance} will
3663 not skip over recursive function calls, and the target location doesn't
3664 have to be in the same frame as the current one.
3668 @kindex si @r{(@code{stepi})}
3670 @itemx stepi @var{arg}
3672 Execute one machine instruction, then stop and return to the debugger.
3674 It is often useful to do @samp{display/i $pc} when stepping by machine
3675 instructions. This makes @value{GDBN} automatically display the next
3676 instruction to be executed, each time your program stops. @xref{Auto
3677 Display,, Automatic display}.
3679 An argument is a repeat count, as in @code{step}.
3683 @kindex ni @r{(@code{nexti})}
3685 @itemx nexti @var{arg}
3687 Execute one machine instruction, but if it is a function call,
3688 proceed until the function returns.
3690 An argument is a repeat count, as in @code{next}.
3697 A signal is an asynchronous event that can happen in a program. The
3698 operating system defines the possible kinds of signals, and gives each
3699 kind a name and a number. For example, in Unix @code{SIGINT} is the
3700 signal a program gets when you type an interrupt character (often @kbd{C-c});
3701 @code{SIGSEGV} is the signal a program gets from referencing a place in
3702 memory far away from all the areas in use; @code{SIGALRM} occurs when
3703 the alarm clock timer goes off (which happens only if your program has
3704 requested an alarm).
3706 @cindex fatal signals
3707 Some signals, including @code{SIGALRM}, are a normal part of the
3708 functioning of your program. Others, such as @code{SIGSEGV}, indicate
3709 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
3710 program has not specified in advance some other way to handle the signal.
3711 @code{SIGINT} does not indicate an error in your program, but it is normally
3712 fatal so it can carry out the purpose of the interrupt: to kill the program.
3714 @value{GDBN} has the ability to detect any occurrence of a signal in your
3715 program. You can tell @value{GDBN} in advance what to do for each kind of
3718 @cindex handling signals
3719 Normally, @value{GDBN} is set up to let the non-erroneous signals like
3720 @code{SIGALRM} be silently passed to your program
3721 (so as not to interfere with their role in the program's functioning)
3722 but to stop your program immediately whenever an error signal happens.
3723 You can change these settings with the @code{handle} command.
3726 @kindex info signals
3729 Print a table of all the kinds of signals and how @value{GDBN} has been told to
3730 handle each one. You can use this to see the signal numbers of all
3731 the defined types of signals.
3733 @code{info handle} is an alias for @code{info signals}.
3736 @item handle @var{signal} @var{keywords}@dots{}
3737 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
3738 can be the number of a signal or its name (with or without the
3739 @samp{SIG} at the beginning); a list of signal numbers of the form
3740 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
3741 known signals. The @var{keywords} say what change to make.
3745 The keywords allowed by the @code{handle} command can be abbreviated.
3746 Their full names are:
3750 @value{GDBN} should not stop your program when this signal happens. It may
3751 still print a message telling you that the signal has come in.
3754 @value{GDBN} should stop your program when this signal happens. This implies
3755 the @code{print} keyword as well.
3758 @value{GDBN} should print a message when this signal happens.
3761 @value{GDBN} should not mention the occurrence of the signal at all. This
3762 implies the @code{nostop} keyword as well.
3766 @value{GDBN} should allow your program to see this signal; your program
3767 can handle the signal, or else it may terminate if the signal is fatal
3768 and not handled. @code{pass} and @code{noignore} are synonyms.
3772 @value{GDBN} should not allow your program to see this signal.
3773 @code{nopass} and @code{ignore} are synonyms.
3777 When a signal stops your program, the signal is not visible to the
3779 continue. Your program sees the signal then, if @code{pass} is in
3780 effect for the signal in question @emph{at that time}. In other words,
3781 after @value{GDBN} reports a signal, you can use the @code{handle}
3782 command with @code{pass} or @code{nopass} to control whether your
3783 program sees that signal when you continue.
3785 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
3786 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
3787 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
3790 You can also use the @code{signal} command to prevent your program from
3791 seeing a signal, or cause it to see a signal it normally would not see,
3792 or to give it any signal at any time. For example, if your program stopped
3793 due to some sort of memory reference error, you might store correct
3794 values into the erroneous variables and continue, hoping to see more
3795 execution; but your program would probably terminate immediately as
3796 a result of the fatal signal once it saw the signal. To prevent this,
3797 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
3801 @section Stopping and starting multi-thread programs
3803 When your program has multiple threads (@pxref{Threads,, Debugging
3804 programs with multiple threads}), you can choose whether to set
3805 breakpoints on all threads, or on a particular thread.
3808 @cindex breakpoints and threads
3809 @cindex thread breakpoints
3810 @kindex break @dots{} thread @var{threadno}
3811 @item break @var{linespec} thread @var{threadno}
3812 @itemx break @var{linespec} thread @var{threadno} if @dots{}
3813 @var{linespec} specifies source lines; there are several ways of
3814 writing them, but the effect is always to specify some source line.
3816 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
3817 to specify that you only want @value{GDBN} to stop the program when a
3818 particular thread reaches this breakpoint. @var{threadno} is one of the
3819 numeric thread identifiers assigned by @value{GDBN}, shown in the first
3820 column of the @samp{info threads} display.
3822 If you do not specify @samp{thread @var{threadno}} when you set a
3823 breakpoint, the breakpoint applies to @emph{all} threads of your
3826 You can use the @code{thread} qualifier on conditional breakpoints as
3827 well; in this case, place @samp{thread @var{threadno}} before the
3828 breakpoint condition, like this:
3831 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
3836 @cindex stopped threads
3837 @cindex threads, stopped
3838 Whenever your program stops under @value{GDBN} for any reason,
3839 @emph{all} threads of execution stop, not just the current thread. This
3840 allows you to examine the overall state of the program, including
3841 switching between threads, without worrying that things may change
3844 @cindex thread breakpoints and system calls
3845 @cindex system calls and thread breakpoints
3846 @cindex premature return from system calls
3847 There is an unfortunate side effect. If one thread stops for a
3848 breakpoint, or for some other reason, and another thread is blocked in a
3849 system call, then the system call may return prematurely. This is a
3850 consequence of the interaction between multiple threads and the signals
3851 that @value{GDBN} uses to implement breakpoints and other events that
3854 To handle this problem, your program should check the return value of
3855 each system call and react appropriately. This is good programming
3858 For example, do not write code like this:
3864 The call to @code{sleep} will return early if a different thread stops
3865 at a breakpoint or for some other reason.
3867 Instead, write this:
3872 unslept = sleep (unslept);
3875 A system call is allowed to return early, so the system is still
3876 conforming to its specification. But @value{GDBN} does cause your
3877 multi-threaded program to behave differently than it would without
3880 Also, @value{GDBN} uses internal breakpoints in the thread library to
3881 monitor certain events such as thread creation and thread destruction.
3882 When such an event happens, a system call in another thread may return
3883 prematurely, even though your program does not appear to stop.
3885 @cindex continuing threads
3886 @cindex threads, continuing
3887 Conversely, whenever you restart the program, @emph{all} threads start
3888 executing. @emph{This is true even when single-stepping} with commands
3889 like @code{step} or @code{next}.
3891 In particular, @value{GDBN} cannot single-step all threads in lockstep.
3892 Since thread scheduling is up to your debugging target's operating
3893 system (not controlled by @value{GDBN}), other threads may
3894 execute more than one statement while the current thread completes a
3895 single step. Moreover, in general other threads stop in the middle of a
3896 statement, rather than at a clean statement boundary, when the program
3899 You might even find your program stopped in another thread after
3900 continuing or even single-stepping. This happens whenever some other
3901 thread runs into a breakpoint, a signal, or an exception before the
3902 first thread completes whatever you requested.
3904 On some OSes, you can lock the OS scheduler and thus allow only a single
3908 @item set scheduler-locking @var{mode}
3909 Set the scheduler locking mode. If it is @code{off}, then there is no
3910 locking and any thread may run at any time. If @code{on}, then only the
3911 current thread may run when the inferior is resumed. The @code{step}
3912 mode optimizes for single-stepping. It stops other threads from
3913 ``seizing the prompt'' by preempting the current thread while you are
3914 stepping. Other threads will only rarely (or never) get a chance to run
3915 when you step. They are more likely to run when you @samp{next} over a
3916 function call, and they are completely free to run when you use commands
3917 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
3918 thread hits a breakpoint during its timeslice, they will never steal the
3919 @value{GDBN} prompt away from the thread that you are debugging.
3921 @item show scheduler-locking
3922 Display the current scheduler locking mode.
3927 @chapter Examining the Stack
3929 When your program has stopped, the first thing you need to know is where it
3930 stopped and how it got there.
3933 Each time your program performs a function call, information about the call
3935 That information includes the location of the call in your program,
3936 the arguments of the call,
3937 and the local variables of the function being called.
3938 The information is saved in a block of data called a @dfn{stack frame}.
3939 The stack frames are allocated in a region of memory called the @dfn{call
3942 When your program stops, the @value{GDBN} commands for examining the
3943 stack allow you to see all of this information.
3945 @cindex selected frame
3946 One of the stack frames is @dfn{selected} by @value{GDBN} and many
3947 @value{GDBN} commands refer implicitly to the selected frame. In
3948 particular, whenever you ask @value{GDBN} for the value of a variable in
3949 your program, the value is found in the selected frame. There are
3950 special @value{GDBN} commands to select whichever frame you are
3951 interested in. @xref{Selection, ,Selecting a frame}.
3953 When your program stops, @value{GDBN} automatically selects the
3954 currently executing frame and describes it briefly, similar to the
3955 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
3958 * Frames:: Stack frames
3959 * Backtrace:: Backtraces
3960 * Selection:: Selecting a frame
3961 * Frame Info:: Information on a frame
3966 @section Stack frames
3968 @cindex frame, definition
3970 The call stack is divided up into contiguous pieces called @dfn{stack
3971 frames}, or @dfn{frames} for short; each frame is the data associated
3972 with one call to one function. The frame contains the arguments given
3973 to the function, the function's local variables, and the address at
3974 which the function is executing.
3976 @cindex initial frame
3977 @cindex outermost frame
3978 @cindex innermost frame
3979 When your program is started, the stack has only one frame, that of the
3980 function @code{main}. This is called the @dfn{initial} frame or the
3981 @dfn{outermost} frame. Each time a function is called, a new frame is
3982 made. Each time a function returns, the frame for that function invocation
3983 is eliminated. If a function is recursive, there can be many frames for
3984 the same function. The frame for the function in which execution is
3985 actually occurring is called the @dfn{innermost} frame. This is the most
3986 recently created of all the stack frames that still exist.
3988 @cindex frame pointer
3989 Inside your program, stack frames are identified by their addresses. A
3990 stack frame consists of many bytes, each of which has its own address; each
3991 kind of computer has a convention for choosing one byte whose
3992 address serves as the address of the frame. Usually this address is kept
3993 in a register called the @dfn{frame pointer register} while execution is
3994 going on in that frame.
3996 @cindex frame number
3997 @value{GDBN} assigns numbers to all existing stack frames, starting with
3998 zero for the innermost frame, one for the frame that called it,
3999 and so on upward. These numbers do not really exist in your program;
4000 they are assigned by @value{GDBN} to give you a way of designating stack
4001 frames in @value{GDBN} commands.
4003 @c The -fomit-frame-pointer below perennially causes hbox overflow
4004 @c underflow problems.
4005 @cindex frameless execution
4006 Some compilers provide a way to compile functions so that they operate
4007 without stack frames. (For example, the @value{GCC} option
4009 @samp{-fomit-frame-pointer}
4011 generates functions without a frame.)
4012 This is occasionally done with heavily used library functions to save
4013 the frame setup time. @value{GDBN} has limited facilities for dealing
4014 with these function invocations. If the innermost function invocation
4015 has no stack frame, @value{GDBN} nevertheless regards it as though
4016 it had a separate frame, which is numbered zero as usual, allowing
4017 correct tracing of the function call chain. However, @value{GDBN} has
4018 no provision for frameless functions elsewhere in the stack.
4021 @kindex frame@r{, command}
4022 @cindex current stack frame
4023 @item frame @var{args}
4024 The @code{frame} command allows you to move from one stack frame to another,
4025 and to print the stack frame you select. @var{args} may be either the
4026 address of the frame or the stack frame number. Without an argument,
4027 @code{frame} prints the current stack frame.
4029 @kindex select-frame
4030 @cindex selecting frame silently
4032 The @code{select-frame} command allows you to move from one stack frame
4033 to another without printing the frame. This is the silent version of
4042 @cindex stack traces
4043 A backtrace is a summary of how your program got where it is. It shows one
4044 line per frame, for many frames, starting with the currently executing
4045 frame (frame zero), followed by its caller (frame one), and on up the
4050 @kindex bt @r{(@code{backtrace})}
4053 Print a backtrace of the entire stack: one line per frame for all
4054 frames in the stack.
4056 You can stop the backtrace at any time by typing the system interrupt
4057 character, normally @kbd{C-c}.
4059 @item backtrace @var{n}
4061 Similar, but print only the innermost @var{n} frames.
4063 @item backtrace -@var{n}
4065 Similar, but print only the outermost @var{n} frames.
4070 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4071 are additional aliases for @code{backtrace}.
4073 Each line in the backtrace shows the frame number and the function name.
4074 The program counter value is also shown---unless you use @code{set
4075 print address off}. The backtrace also shows the source file name and
4076 line number, as well as the arguments to the function. The program
4077 counter value is omitted if it is at the beginning of the code for that
4080 Here is an example of a backtrace. It was made with the command
4081 @samp{bt 3}, so it shows the innermost three frames.
4085 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4087 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4088 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4090 (More stack frames follow...)
4095 The display for frame zero does not begin with a program counter
4096 value, indicating that your program has stopped at the beginning of the
4097 code for line @code{993} of @code{builtin.c}.
4099 Most programs have a standard user entry point---a place where system
4100 libraries and startup code transition into user code. For C this is
4101 @code{main}. When @value{GDBN} finds the entry function in a backtrace
4102 it will terminate the backtrace, to avoid tracing into highly
4103 system-specific (and generally uninteresting) code.
4105 If you need to examine the startup code, or limit the number of levels
4106 in a backtrace, you can change this behavior:
4109 @item set backtrace past-main
4110 @itemx set backtrace past-main on
4111 @kindex set backtrace
4112 Backtraces will continue past the user entry point.
4114 @item set backtrace past-main off
4115 Backtraces will stop when they encounter the user entry point. This is the
4118 @item show backtrace past-main
4119 @kindex show backtrace
4120 Display the current user entry point backtrace policy.
4122 @item set backtrace limit @var{n}
4123 @itemx set backtrace limit 0
4124 @cindex backtrace limit
4125 Limit the backtrace to @var{n} levels. A value of zero means
4128 @item show backtrace limit
4129 Display the current limit on backtrace levels.
4133 @section Selecting a frame
4135 Most commands for examining the stack and other data in your program work on
4136 whichever stack frame is selected at the moment. Here are the commands for
4137 selecting a stack frame; all of them finish by printing a brief description
4138 of the stack frame just selected.
4141 @kindex frame@r{, selecting}
4142 @kindex f @r{(@code{frame})}
4145 Select frame number @var{n}. Recall that frame zero is the innermost
4146 (currently executing) frame, frame one is the frame that called the
4147 innermost one, and so on. The highest-numbered frame is the one for
4150 @item frame @var{addr}
4152 Select the frame at address @var{addr}. This is useful mainly if the
4153 chaining of stack frames has been damaged by a bug, making it
4154 impossible for @value{GDBN} to assign numbers properly to all frames. In
4155 addition, this can be useful when your program has multiple stacks and
4156 switches between them.
4158 On the SPARC architecture, @code{frame} needs two addresses to
4159 select an arbitrary frame: a frame pointer and a stack pointer.
4161 On the MIPS and Alpha architecture, it needs two addresses: a stack
4162 pointer and a program counter.
4164 On the 29k architecture, it needs three addresses: a register stack
4165 pointer, a program counter, and a memory stack pointer.
4166 @c note to future updaters: this is conditioned on a flag
4167 @c SETUP_ARBITRARY_FRAME in the tm-*.h files. The above is up to date
4168 @c as of 27 Jan 1994.
4172 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4173 advances toward the outermost frame, to higher frame numbers, to frames
4174 that have existed longer. @var{n} defaults to one.
4177 @kindex do @r{(@code{down})}
4179 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4180 advances toward the innermost frame, to lower frame numbers, to frames
4181 that were created more recently. @var{n} defaults to one. You may
4182 abbreviate @code{down} as @code{do}.
4185 All of these commands end by printing two lines of output describing the
4186 frame. The first line shows the frame number, the function name, the
4187 arguments, and the source file and line number of execution in that
4188 frame. The second line shows the text of that source line.
4196 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4198 10 read_input_file (argv[i]);
4202 After such a printout, the @code{list} command with no arguments
4203 prints ten lines centered on the point of execution in the frame.
4204 You can also edit the program at the point of execution with your favorite
4205 editing program by typing @code{edit}.
4206 @xref{List, ,Printing source lines},
4210 @kindex down-silently
4212 @item up-silently @var{n}
4213 @itemx down-silently @var{n}
4214 These two commands are variants of @code{up} and @code{down},
4215 respectively; they differ in that they do their work silently, without
4216 causing display of the new frame. They are intended primarily for use
4217 in @value{GDBN} command scripts, where the output might be unnecessary and
4222 @section Information about a frame
4224 There are several other commands to print information about the selected
4230 When used without any argument, this command does not change which
4231 frame is selected, but prints a brief description of the currently
4232 selected stack frame. It can be abbreviated @code{f}. With an
4233 argument, this command is used to select a stack frame.
4234 @xref{Selection, ,Selecting a frame}.
4237 @kindex info f @r{(@code{info frame})}
4240 This command prints a verbose description of the selected stack frame,
4245 the address of the frame
4247 the address of the next frame down (called by this frame)
4249 the address of the next frame up (caller of this frame)
4251 the language in which the source code corresponding to this frame is written
4253 the address of the frame's arguments
4255 the address of the frame's local variables
4257 the program counter saved in it (the address of execution in the caller frame)
4259 which registers were saved in the frame
4262 @noindent The verbose description is useful when
4263 something has gone wrong that has made the stack format fail to fit
4264 the usual conventions.
4266 @item info frame @var{addr}
4267 @itemx info f @var{addr}
4268 Print a verbose description of the frame at address @var{addr}, without
4269 selecting that frame. The selected frame remains unchanged by this
4270 command. This requires the same kind of address (more than one for some
4271 architectures) that you specify in the @code{frame} command.
4272 @xref{Selection, ,Selecting a frame}.
4276 Print the arguments of the selected frame, each on a separate line.
4280 Print the local variables of the selected frame, each on a separate
4281 line. These are all variables (declared either static or automatic)
4282 accessible at the point of execution of the selected frame.
4285 @cindex catch exceptions, list active handlers
4286 @cindex exception handlers, how to list
4288 Print a list of all the exception handlers that are active in the
4289 current stack frame at the current point of execution. To see other
4290 exception handlers, visit the associated frame (using the @code{up},
4291 @code{down}, or @code{frame} commands); then type @code{info catch}.
4292 @xref{Set Catchpoints, , Setting catchpoints}.
4298 @chapter Examining Source Files
4300 @value{GDBN} can print parts of your program's source, since the debugging
4301 information recorded in the program tells @value{GDBN} what source files were
4302 used to build it. When your program stops, @value{GDBN} spontaneously prints
4303 the line where it stopped. Likewise, when you select a stack frame
4304 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4305 execution in that frame has stopped. You can print other portions of
4306 source files by explicit command.
4308 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4309 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4310 @value{GDBN} under @sc{gnu} Emacs}.
4313 * List:: Printing source lines
4314 * Edit:: Editing source files
4315 * Search:: Searching source files
4316 * Source Path:: Specifying source directories
4317 * Machine Code:: Source and machine code
4321 @section Printing source lines
4324 @kindex l @r{(@code{list})}
4325 To print lines from a source file, use the @code{list} command
4326 (abbreviated @code{l}). By default, ten lines are printed.
4327 There are several ways to specify what part of the file you want to print.
4329 Here are the forms of the @code{list} command most commonly used:
4332 @item list @var{linenum}
4333 Print lines centered around line number @var{linenum} in the
4334 current source file.
4336 @item list @var{function}
4337 Print lines centered around the beginning of function
4341 Print more lines. If the last lines printed were printed with a
4342 @code{list} command, this prints lines following the last lines
4343 printed; however, if the last line printed was a solitary line printed
4344 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4345 Stack}), this prints lines centered around that line.
4348 Print lines just before the lines last printed.
4351 By default, @value{GDBN} prints ten source lines with any of these forms of
4352 the @code{list} command. You can change this using @code{set listsize}:
4355 @kindex set listsize
4356 @item set listsize @var{count}
4357 Make the @code{list} command display @var{count} source lines (unless
4358 the @code{list} argument explicitly specifies some other number).
4360 @kindex show listsize
4362 Display the number of lines that @code{list} prints.
4365 Repeating a @code{list} command with @key{RET} discards the argument,
4366 so it is equivalent to typing just @code{list}. This is more useful
4367 than listing the same lines again. An exception is made for an
4368 argument of @samp{-}; that argument is preserved in repetition so that
4369 each repetition moves up in the source file.
4372 In general, the @code{list} command expects you to supply zero, one or two
4373 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4374 of writing them, but the effect is always to specify some source line.
4375 Here is a complete description of the possible arguments for @code{list}:
4378 @item list @var{linespec}
4379 Print lines centered around the line specified by @var{linespec}.
4381 @item list @var{first},@var{last}
4382 Print lines from @var{first} to @var{last}. Both arguments are
4385 @item list ,@var{last}
4386 Print lines ending with @var{last}.
4388 @item list @var{first},
4389 Print lines starting with @var{first}.
4392 Print lines just after the lines last printed.
4395 Print lines just before the lines last printed.
4398 As described in the preceding table.
4401 Here are the ways of specifying a single source line---all the
4406 Specifies line @var{number} of the current source file.
4407 When a @code{list} command has two linespecs, this refers to
4408 the same source file as the first linespec.
4411 Specifies the line @var{offset} lines after the last line printed.
4412 When used as the second linespec in a @code{list} command that has
4413 two, this specifies the line @var{offset} lines down from the
4417 Specifies the line @var{offset} lines before the last line printed.
4419 @item @var{filename}:@var{number}
4420 Specifies line @var{number} in the source file @var{filename}.
4422 @item @var{function}
4423 Specifies the line that begins the body of the function @var{function}.
4424 For example: in C, this is the line with the open brace.
4426 @item @var{filename}:@var{function}
4427 Specifies the line of the open-brace that begins the body of the
4428 function @var{function} in the file @var{filename}. You only need the
4429 file name with a function name to avoid ambiguity when there are
4430 identically named functions in different source files.
4432 @item *@var{address}
4433 Specifies the line containing the program address @var{address}.
4434 @var{address} may be any expression.
4438 @section Editing source files
4439 @cindex editing source files
4442 @kindex e @r{(@code{edit})}
4443 To edit the lines in a source file, use the @code{edit} command.
4444 The editing program of your choice
4445 is invoked with the current line set to
4446 the active line in the program.
4447 Alternatively, there are several ways to specify what part of the file you
4448 want to print if you want to see other parts of the program.
4450 Here are the forms of the @code{edit} command most commonly used:
4454 Edit the current source file at the active line number in the program.
4456 @item edit @var{number}
4457 Edit the current source file with @var{number} as the active line number.
4459 @item edit @var{function}
4460 Edit the file containing @var{function} at the beginning of its definition.
4462 @item edit @var{filename}:@var{number}
4463 Specifies line @var{number} in the source file @var{filename}.
4465 @item edit @var{filename}:@var{function}
4466 Specifies the line that begins the body of the
4467 function @var{function} in the file @var{filename}. You only need the
4468 file name with a function name to avoid ambiguity when there are
4469 identically named functions in different source files.
4471 @item edit *@var{address}
4472 Specifies the line containing the program address @var{address}.
4473 @var{address} may be any expression.
4476 @subsection Choosing your editor
4477 You can customize @value{GDBN} to use any editor you want
4479 The only restriction is that your editor (say @code{ex}), recognizes the
4480 following command-line syntax:
4482 ex +@var{number} file
4484 The optional numeric value +@var{number} specifies the number of the line in
4485 the file where to start editing.}.
4486 By default, it is @file{@value{EDITOR}}, but you can change this
4487 by setting the environment variable @code{EDITOR} before using
4488 @value{GDBN}. For example, to configure @value{GDBN} to use the
4489 @code{vi} editor, you could use these commands with the @code{sh} shell:
4495 or in the @code{csh} shell,
4497 setenv EDITOR /usr/bin/vi
4502 @section Searching source files
4503 @cindex searching source files
4504 @kindex reverse-search
4506 There are two commands for searching through the current source file for a
4511 @kindex forward-search
4512 @item forward-search @var{regexp}
4513 @itemx search @var{regexp}
4514 The command @samp{forward-search @var{regexp}} checks each line,
4515 starting with the one following the last line listed, for a match for
4516 @var{regexp}. It lists the line that is found. You can use the
4517 synonym @samp{search @var{regexp}} or abbreviate the command name as
4520 @item reverse-search @var{regexp}
4521 The command @samp{reverse-search @var{regexp}} checks each line, starting
4522 with the one before the last line listed and going backward, for a match
4523 for @var{regexp}. It lists the line that is found. You can abbreviate
4524 this command as @code{rev}.
4528 @section Specifying source directories
4531 @cindex directories for source files
4532 Executable programs sometimes do not record the directories of the source
4533 files from which they were compiled, just the names. Even when they do,
4534 the directories could be moved between the compilation and your debugging
4535 session. @value{GDBN} has a list of directories to search for source files;
4536 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
4537 it tries all the directories in the list, in the order they are present
4538 in the list, until it finds a file with the desired name.
4540 For example, suppose an executable references the file
4541 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
4542 @file{/mnt/cross}. The file is first looked up literally; if this
4543 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
4544 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
4545 message is printed. @value{GDBN} does not look up the parts of the
4546 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
4547 Likewise, the subdirectories of the source path are not searched: if
4548 the source path is @file{/mnt/cross}, and the binary refers to
4549 @file{foo.c}, @value{GDBN} would not find it under
4550 @file{/mnt/cross/usr/src/foo-1.0/lib}.
4552 Plain file names, relative file names with leading directories, file
4553 names containing dots, etc.@: are all treated as described above; for
4554 instance, if the source path is @file{/mnt/cross}, and the source file
4555 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
4556 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
4557 that---@file{/mnt/cross/foo.c}.
4559 Note that the executable search path is @emph{not} used to locate the
4560 source files. Neither is the current working directory, unless it
4561 happens to be in the source path.
4563 Whenever you reset or rearrange the source path, @value{GDBN} clears out
4564 any information it has cached about where source files are found and where
4565 each line is in the file.
4569 When you start @value{GDBN}, its source path includes only @samp{cdir}
4570 and @samp{cwd}, in that order.
4571 To add other directories, use the @code{directory} command.
4574 @item directory @var{dirname} @dots{}
4575 @item dir @var{dirname} @dots{}
4576 Add directory @var{dirname} to the front of the source path. Several
4577 directory names may be given to this command, separated by @samp{:}
4578 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
4579 part of absolute file names) or
4580 whitespace. You may specify a directory that is already in the source
4581 path; this moves it forward, so @value{GDBN} searches it sooner.
4585 @vindex $cdir@r{, convenience variable}
4586 @vindex $cwdr@r{, convenience variable}
4587 @cindex compilation directory
4588 @cindex current directory
4589 @cindex working directory
4590 @cindex directory, current
4591 @cindex directory, compilation
4592 You can use the string @samp{$cdir} to refer to the compilation
4593 directory (if one is recorded), and @samp{$cwd} to refer to the current
4594 working directory. @samp{$cwd} is not the same as @samp{.}---the former
4595 tracks the current working directory as it changes during your @value{GDBN}
4596 session, while the latter is immediately expanded to the current
4597 directory at the time you add an entry to the source path.
4600 Reset the source path to empty again. This requires confirmation.
4602 @c RET-repeat for @code{directory} is explicitly disabled, but since
4603 @c repeating it would be a no-op we do not say that. (thanks to RMS)
4605 @item show directories
4606 @kindex show directories
4607 Print the source path: show which directories it contains.
4610 If your source path is cluttered with directories that are no longer of
4611 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
4612 versions of source. You can correct the situation as follows:
4616 Use @code{directory} with no argument to reset the source path to empty.
4619 Use @code{directory} with suitable arguments to reinstall the
4620 directories you want in the source path. You can add all the
4621 directories in one command.
4625 @section Source and machine code
4626 @cindex source line and its code address
4628 You can use the command @code{info line} to map source lines to program
4629 addresses (and vice versa), and the command @code{disassemble} to display
4630 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
4631 mode, the @code{info line} command causes the arrow to point to the
4632 line specified. Also, @code{info line} prints addresses in symbolic form as
4637 @item info line @var{linespec}
4638 Print the starting and ending addresses of the compiled code for
4639 source line @var{linespec}. You can specify source lines in any of
4640 the ways understood by the @code{list} command (@pxref{List, ,Printing
4644 For example, we can use @code{info line} to discover the location of
4645 the object code for the first line of function
4646 @code{m4_changequote}:
4648 @c FIXME: I think this example should also show the addresses in
4649 @c symbolic form, as they usually would be displayed.
4651 (@value{GDBP}) info line m4_changequote
4652 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
4656 @cindex code address and its source line
4657 We can also inquire (using @code{*@var{addr}} as the form for
4658 @var{linespec}) what source line covers a particular address:
4660 (@value{GDBP}) info line *0x63ff
4661 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
4664 @cindex @code{$_} and @code{info line}
4665 @cindex @code{x} command, default address
4666 @kindex x@r{(examine), and} info line
4667 After @code{info line}, the default address for the @code{x} command
4668 is changed to the starting address of the line, so that @samp{x/i} is
4669 sufficient to begin examining the machine code (@pxref{Memory,
4670 ,Examining memory}). Also, this address is saved as the value of the
4671 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
4676 @cindex assembly instructions
4677 @cindex instructions, assembly
4678 @cindex machine instructions
4679 @cindex listing machine instructions
4681 This specialized command dumps a range of memory as machine
4682 instructions. The default memory range is the function surrounding the
4683 program counter of the selected frame. A single argument to this
4684 command is a program counter value; @value{GDBN} dumps the function
4685 surrounding this value. Two arguments specify a range of addresses
4686 (first inclusive, second exclusive) to dump.
4689 The following example shows the disassembly of a range of addresses of
4690 HP PA-RISC 2.0 code:
4693 (@value{GDBP}) disas 0x32c4 0x32e4
4694 Dump of assembler code from 0x32c4 to 0x32e4:
4695 0x32c4 <main+204>: addil 0,dp
4696 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
4697 0x32cc <main+212>: ldil 0x3000,r31
4698 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
4699 0x32d4 <main+220>: ldo 0(r31),rp
4700 0x32d8 <main+224>: addil -0x800,dp
4701 0x32dc <main+228>: ldo 0x588(r1),r26
4702 0x32e0 <main+232>: ldil 0x3000,r31
4703 End of assembler dump.
4706 Some architectures have more than one commonly-used set of instruction
4707 mnemonics or other syntax.
4710 @kindex set disassembly-flavor
4711 @cindex Intel disassembly flavor
4712 @cindex AT&T disassembly flavor
4713 @item set disassembly-flavor @var{instruction-set}
4714 Select the instruction set to use when disassembling the
4715 program via the @code{disassemble} or @code{x/i} commands.
4717 Currently this command is only defined for the Intel x86 family. You
4718 can set @var{instruction-set} to either @code{intel} or @code{att}.
4719 The default is @code{att}, the AT&T flavor used by default by Unix
4720 assemblers for x86-based targets.
4725 @chapter Examining Data
4727 @cindex printing data
4728 @cindex examining data
4731 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
4732 @c document because it is nonstandard... Under Epoch it displays in a
4733 @c different window or something like that.
4734 The usual way to examine data in your program is with the @code{print}
4735 command (abbreviated @code{p}), or its synonym @code{inspect}. It
4736 evaluates and prints the value of an expression of the language your
4737 program is written in (@pxref{Languages, ,Using @value{GDBN} with
4738 Different Languages}).
4741 @item print @var{expr}
4742 @itemx print /@var{f} @var{expr}
4743 @var{expr} is an expression (in the source language). By default the
4744 value of @var{expr} is printed in a format appropriate to its data type;
4745 you can choose a different format by specifying @samp{/@var{f}}, where
4746 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
4750 @itemx print /@var{f}
4751 @cindex reprint the last value
4752 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
4753 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
4754 conveniently inspect the same value in an alternative format.
4757 A more low-level way of examining data is with the @code{x} command.
4758 It examines data in memory at a specified address and prints it in a
4759 specified format. @xref{Memory, ,Examining memory}.
4761 If you are interested in information about types, or about how the
4762 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
4763 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
4767 * Expressions:: Expressions
4768 * Variables:: Program variables
4769 * Arrays:: Artificial arrays
4770 * Output Formats:: Output formats
4771 * Memory:: Examining memory
4772 * Auto Display:: Automatic display
4773 * Print Settings:: Print settings
4774 * Value History:: Value history
4775 * Convenience Vars:: Convenience variables
4776 * Registers:: Registers
4777 * Floating Point Hardware:: Floating point hardware
4778 * Vector Unit:: Vector Unit
4779 * Auxiliary Vector:: Auxiliary data provided by operating system
4780 * Memory Region Attributes:: Memory region attributes
4781 * Dump/Restore Files:: Copy between memory and a file
4782 * Character Sets:: Debugging programs that use a different
4783 character set than GDB does
4787 @section Expressions
4790 @code{print} and many other @value{GDBN} commands accept an expression and
4791 compute its value. Any kind of constant, variable or operator defined
4792 by the programming language you are using is valid in an expression in
4793 @value{GDBN}. This includes conditional expressions, function calls,
4794 casts, and string constants. It also includes preprocessor macros, if
4795 you compiled your program to include this information; see
4798 @cindex arrays in expressions
4799 @value{GDBN} supports array constants in expressions input by
4800 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
4801 you can use the command @code{print @{1, 2, 3@}} to build up an array in
4802 memory that is @code{malloc}ed in the target program.
4804 Because C is so widespread, most of the expressions shown in examples in
4805 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
4806 Languages}, for information on how to use expressions in other
4809 In this section, we discuss operators that you can use in @value{GDBN}
4810 expressions regardless of your programming language.
4812 @cindex casts, in expressions
4813 Casts are supported in all languages, not just in C, because it is so
4814 useful to cast a number into a pointer in order to examine a structure
4815 at that address in memory.
4816 @c FIXME: casts supported---Mod2 true?
4818 @value{GDBN} supports these operators, in addition to those common
4819 to programming languages:
4823 @samp{@@} is a binary operator for treating parts of memory as arrays.
4824 @xref{Arrays, ,Artificial arrays}, for more information.
4827 @samp{::} allows you to specify a variable in terms of the file or
4828 function where it is defined. @xref{Variables, ,Program variables}.
4830 @cindex @{@var{type}@}
4831 @cindex type casting memory
4832 @cindex memory, viewing as typed object
4833 @cindex casts, to view memory
4834 @item @{@var{type}@} @var{addr}
4835 Refers to an object of type @var{type} stored at address @var{addr} in
4836 memory. @var{addr} may be any expression whose value is an integer or
4837 pointer (but parentheses are required around binary operators, just as in
4838 a cast). This construct is allowed regardless of what kind of data is
4839 normally supposed to reside at @var{addr}.
4843 @section Program variables
4845 The most common kind of expression to use is the name of a variable
4848 Variables in expressions are understood in the selected stack frame
4849 (@pxref{Selection, ,Selecting a frame}); they must be either:
4853 global (or file-static)
4860 visible according to the scope rules of the
4861 programming language from the point of execution in that frame
4864 @noindent This means that in the function
4879 you can examine and use the variable @code{a} whenever your program is
4880 executing within the function @code{foo}, but you can only use or
4881 examine the variable @code{b} while your program is executing inside
4882 the block where @code{b} is declared.
4884 @cindex variable name conflict
4885 There is an exception: you can refer to a variable or function whose
4886 scope is a single source file even if the current execution point is not
4887 in this file. But it is possible to have more than one such variable or
4888 function with the same name (in different source files). If that
4889 happens, referring to that name has unpredictable effects. If you wish,
4890 you can specify a static variable in a particular function or file,
4891 using the colon-colon (@code{::}) notation:
4893 @cindex colon-colon, context for variables/functions
4895 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
4896 @cindex @code{::}, context for variables/functions
4899 @var{file}::@var{variable}
4900 @var{function}::@var{variable}
4904 Here @var{file} or @var{function} is the name of the context for the
4905 static @var{variable}. In the case of file names, you can use quotes to
4906 make sure @value{GDBN} parses the file name as a single word---for example,
4907 to print a global value of @code{x} defined in @file{f2.c}:
4910 (@value{GDBP}) p 'f2.c'::x
4913 @cindex C@t{++} scope resolution
4914 This use of @samp{::} is very rarely in conflict with the very similar
4915 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
4916 scope resolution operator in @value{GDBN} expressions.
4917 @c FIXME: Um, so what happens in one of those rare cases where it's in
4920 @cindex wrong values
4921 @cindex variable values, wrong
4922 @cindex function entry/exit, wrong values of variables
4923 @cindex optimized code, wrong values of variables
4925 @emph{Warning:} Occasionally, a local variable may appear to have the
4926 wrong value at certain points in a function---just after entry to a new
4927 scope, and just before exit.
4929 You may see this problem when you are stepping by machine instructions.
4930 This is because, on most machines, it takes more than one instruction to
4931 set up a stack frame (including local variable definitions); if you are
4932 stepping by machine instructions, variables may appear to have the wrong
4933 values until the stack frame is completely built. On exit, it usually
4934 also takes more than one machine instruction to destroy a stack frame;
4935 after you begin stepping through that group of instructions, local
4936 variable definitions may be gone.
4938 This may also happen when the compiler does significant optimizations.
4939 To be sure of always seeing accurate values, turn off all optimization
4942 @cindex ``No symbol "foo" in current context''
4943 Another possible effect of compiler optimizations is to optimize
4944 unused variables out of existence, or assign variables to registers (as
4945 opposed to memory addresses). Depending on the support for such cases
4946 offered by the debug info format used by the compiler, @value{GDBN}
4947 might not be able to display values for such local variables. If that
4948 happens, @value{GDBN} will print a message like this:
4951 No symbol "foo" in current context.
4954 To solve such problems, either recompile without optimizations, or use a
4955 different debug info format, if the compiler supports several such
4956 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
4957 usually supports the @option{-gstabs+} option. @option{-gstabs+}
4958 produces debug info in a format that is superior to formats such as
4959 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
4960 an effective form for debug info. @xref{Debugging Options,,Options
4961 for Debugging Your Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}.
4962 @xref{C, , Debugging C++}, for more info about debug info formats
4963 that are best suited to C@t{++} programs.
4966 @section Artificial arrays
4968 @cindex artificial array
4970 @kindex @@@r{, referencing memory as an array}
4971 It is often useful to print out several successive objects of the
4972 same type in memory; a section of an array, or an array of
4973 dynamically determined size for which only a pointer exists in the
4976 You can do this by referring to a contiguous span of memory as an
4977 @dfn{artificial array}, using the binary operator @samp{@@}. The left
4978 operand of @samp{@@} should be the first element of the desired array
4979 and be an individual object. The right operand should be the desired length
4980 of the array. The result is an array value whose elements are all of
4981 the type of the left argument. The first element is actually the left
4982 argument; the second element comes from bytes of memory immediately
4983 following those that hold the first element, and so on. Here is an
4984 example. If a program says
4987 int *array = (int *) malloc (len * sizeof (int));
4991 you can print the contents of @code{array} with
4997 The left operand of @samp{@@} must reside in memory. Array values made
4998 with @samp{@@} in this way behave just like other arrays in terms of
4999 subscripting, and are coerced to pointers when used in expressions.
5000 Artificial arrays most often appear in expressions via the value history
5001 (@pxref{Value History, ,Value history}), after printing one out.
5003 Another way to create an artificial array is to use a cast.
5004 This re-interprets a value as if it were an array.
5005 The value need not be in memory:
5007 (@value{GDBP}) p/x (short[2])0x12345678
5008 $1 = @{0x1234, 0x5678@}
5011 As a convenience, if you leave the array length out (as in
5012 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5013 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5015 (@value{GDBP}) p/x (short[])0x12345678
5016 $2 = @{0x1234, 0x5678@}
5019 Sometimes the artificial array mechanism is not quite enough; in
5020 moderately complex data structures, the elements of interest may not
5021 actually be adjacent---for example, if you are interested in the values
5022 of pointers in an array. One useful work-around in this situation is
5023 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5024 variables}) as a counter in an expression that prints the first
5025 interesting value, and then repeat that expression via @key{RET}. For
5026 instance, suppose you have an array @code{dtab} of pointers to
5027 structures, and you are interested in the values of a field @code{fv}
5028 in each structure. Here is an example of what you might type:
5038 @node Output Formats
5039 @section Output formats
5041 @cindex formatted output
5042 @cindex output formats
5043 By default, @value{GDBN} prints a value according to its data type. Sometimes
5044 this is not what you want. For example, you might want to print a number
5045 in hex, or a pointer in decimal. Or you might want to view data in memory
5046 at a certain address as a character string or as an instruction. To do
5047 these things, specify an @dfn{output format} when you print a value.
5049 The simplest use of output formats is to say how to print a value
5050 already computed. This is done by starting the arguments of the
5051 @code{print} command with a slash and a format letter. The format
5052 letters supported are:
5056 Regard the bits of the value as an integer, and print the integer in
5060 Print as integer in signed decimal.
5063 Print as integer in unsigned decimal.
5066 Print as integer in octal.
5069 Print as integer in binary. The letter @samp{t} stands for ``two''.
5070 @footnote{@samp{b} cannot be used because these format letters are also
5071 used with the @code{x} command, where @samp{b} stands for ``byte'';
5072 see @ref{Memory,,Examining memory}.}
5075 @cindex unknown address, locating
5076 @cindex locate address
5077 Print as an address, both absolute in hexadecimal and as an offset from
5078 the nearest preceding symbol. You can use this format used to discover
5079 where (in what function) an unknown address is located:
5082 (@value{GDBP}) p/a 0x54320
5083 $3 = 0x54320 <_initialize_vx+396>
5087 The command @code{info symbol 0x54320} yields similar results.
5088 @xref{Symbols, info symbol}.
5091 Regard as an integer and print it as a character constant.
5094 Regard the bits of the value as a floating point number and print
5095 using typical floating point syntax.
5098 For example, to print the program counter in hex (@pxref{Registers}), type
5105 Note that no space is required before the slash; this is because command
5106 names in @value{GDBN} cannot contain a slash.
5108 To reprint the last value in the value history with a different format,
5109 you can use the @code{print} command with just a format and no
5110 expression. For example, @samp{p/x} reprints the last value in hex.
5113 @section Examining memory
5115 You can use the command @code{x} (for ``examine'') to examine memory in
5116 any of several formats, independently of your program's data types.
5118 @cindex examining memory
5120 @kindex x @r{(examine memory)}
5121 @item x/@var{nfu} @var{addr}
5124 Use the @code{x} command to examine memory.
5127 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5128 much memory to display and how to format it; @var{addr} is an
5129 expression giving the address where you want to start displaying memory.
5130 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5131 Several commands set convenient defaults for @var{addr}.
5134 @item @var{n}, the repeat count
5135 The repeat count is a decimal integer; the default is 1. It specifies
5136 how much memory (counting by units @var{u}) to display.
5137 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5140 @item @var{f}, the display format
5141 The display format is one of the formats used by @code{print},
5142 @samp{s} (null-terminated string), or @samp{i} (machine instruction).
5143 The default is @samp{x} (hexadecimal) initially.
5144 The default changes each time you use either @code{x} or @code{print}.
5146 @item @var{u}, the unit size
5147 The unit size is any of
5153 Halfwords (two bytes).
5155 Words (four bytes). This is the initial default.
5157 Giant words (eight bytes).
5160 Each time you specify a unit size with @code{x}, that size becomes the
5161 default unit the next time you use @code{x}. (For the @samp{s} and
5162 @samp{i} formats, the unit size is ignored and is normally not written.)
5164 @item @var{addr}, starting display address
5165 @var{addr} is the address where you want @value{GDBN} to begin displaying
5166 memory. The expression need not have a pointer value (though it may);
5167 it is always interpreted as an integer address of a byte of memory.
5168 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5169 @var{addr} is usually just after the last address examined---but several
5170 other commands also set the default address: @code{info breakpoints} (to
5171 the address of the last breakpoint listed), @code{info line} (to the
5172 starting address of a line), and @code{print} (if you use it to display
5173 a value from memory).
5176 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5177 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5178 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5179 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5180 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5182 Since the letters indicating unit sizes are all distinct from the
5183 letters specifying output formats, you do not have to remember whether
5184 unit size or format comes first; either order works. The output
5185 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5186 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5188 Even though the unit size @var{u} is ignored for the formats @samp{s}
5189 and @samp{i}, you might still want to use a count @var{n}; for example,
5190 @samp{3i} specifies that you want to see three machine instructions,
5191 including any operands. The command @code{disassemble} gives an
5192 alternative way of inspecting machine instructions; see @ref{Machine
5193 Code,,Source and machine code}.
5195 All the defaults for the arguments to @code{x} are designed to make it
5196 easy to continue scanning memory with minimal specifications each time
5197 you use @code{x}. For example, after you have inspected three machine
5198 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5199 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5200 the repeat count @var{n} is used again; the other arguments default as
5201 for successive uses of @code{x}.
5203 @cindex @code{$_}, @code{$__}, and value history
5204 The addresses and contents printed by the @code{x} command are not saved
5205 in the value history because there is often too much of them and they
5206 would get in the way. Instead, @value{GDBN} makes these values available for
5207 subsequent use in expressions as values of the convenience variables
5208 @code{$_} and @code{$__}. After an @code{x} command, the last address
5209 examined is available for use in expressions in the convenience variable
5210 @code{$_}. The contents of that address, as examined, are available in
5211 the convenience variable @code{$__}.
5213 If the @code{x} command has a repeat count, the address and contents saved
5214 are from the last memory unit printed; this is not the same as the last
5215 address printed if several units were printed on the last line of output.
5218 @section Automatic display
5219 @cindex automatic display
5220 @cindex display of expressions
5222 If you find that you want to print the value of an expression frequently
5223 (to see how it changes), you might want to add it to the @dfn{automatic
5224 display list} so that @value{GDBN} prints its value each time your program stops.
5225 Each expression added to the list is given a number to identify it;
5226 to remove an expression from the list, you specify that number.
5227 The automatic display looks like this:
5231 3: bar[5] = (struct hack *) 0x3804
5235 This display shows item numbers, expressions and their current values. As with
5236 displays you request manually using @code{x} or @code{print}, you can
5237 specify the output format you prefer; in fact, @code{display} decides
5238 whether to use @code{print} or @code{x} depending on how elaborate your
5239 format specification is---it uses @code{x} if you specify a unit size,
5240 or one of the two formats (@samp{i} and @samp{s}) that are only
5241 supported by @code{x}; otherwise it uses @code{print}.
5245 @item display @var{expr}
5246 Add the expression @var{expr} to the list of expressions to display
5247 each time your program stops. @xref{Expressions, ,Expressions}.
5249 @code{display} does not repeat if you press @key{RET} again after using it.
5251 @item display/@var{fmt} @var{expr}
5252 For @var{fmt} specifying only a display format and not a size or
5253 count, add the expression @var{expr} to the auto-display list but
5254 arrange to display it each time in the specified format @var{fmt}.
5255 @xref{Output Formats,,Output formats}.
5257 @item display/@var{fmt} @var{addr}
5258 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5259 number of units, add the expression @var{addr} as a memory address to
5260 be examined each time your program stops. Examining means in effect
5261 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5264 For example, @samp{display/i $pc} can be helpful, to see the machine
5265 instruction about to be executed each time execution stops (@samp{$pc}
5266 is a common name for the program counter; @pxref{Registers, ,Registers}).
5269 @kindex delete display
5271 @item undisplay @var{dnums}@dots{}
5272 @itemx delete display @var{dnums}@dots{}
5273 Remove item numbers @var{dnums} from the list of expressions to display.
5275 @code{undisplay} does not repeat if you press @key{RET} after using it.
5276 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5278 @kindex disable display
5279 @item disable display @var{dnums}@dots{}
5280 Disable the display of item numbers @var{dnums}. A disabled display
5281 item is not printed automatically, but is not forgotten. It may be
5282 enabled again later.
5284 @kindex enable display
5285 @item enable display @var{dnums}@dots{}
5286 Enable display of item numbers @var{dnums}. It becomes effective once
5287 again in auto display of its expression, until you specify otherwise.
5290 Display the current values of the expressions on the list, just as is
5291 done when your program stops.
5293 @kindex info display
5295 Print the list of expressions previously set up to display
5296 automatically, each one with its item number, but without showing the
5297 values. This includes disabled expressions, which are marked as such.
5298 It also includes expressions which would not be displayed right now
5299 because they refer to automatic variables not currently available.
5302 @cindex display disabled out of scope
5303 If a display expression refers to local variables, then it does not make
5304 sense outside the lexical context for which it was set up. Such an
5305 expression is disabled when execution enters a context where one of its
5306 variables is not defined. For example, if you give the command
5307 @code{display last_char} while inside a function with an argument
5308 @code{last_char}, @value{GDBN} displays this argument while your program
5309 continues to stop inside that function. When it stops elsewhere---where
5310 there is no variable @code{last_char}---the display is disabled
5311 automatically. The next time your program stops where @code{last_char}
5312 is meaningful, you can enable the display expression once again.
5314 @node Print Settings
5315 @section Print settings
5317 @cindex format options
5318 @cindex print settings
5319 @value{GDBN} provides the following ways to control how arrays, structures,
5320 and symbols are printed.
5323 These settings are useful for debugging programs in any language:
5327 @item set print address
5328 @itemx set print address on
5329 @cindex print/don't print memory addresses
5330 @value{GDBN} prints memory addresses showing the location of stack
5331 traces, structure values, pointer values, breakpoints, and so forth,
5332 even when it also displays the contents of those addresses. The default
5333 is @code{on}. For example, this is what a stack frame display looks like with
5334 @code{set print address on}:
5339 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
5341 530 if (lquote != def_lquote)
5345 @item set print address off
5346 Do not print addresses when displaying their contents. For example,
5347 this is the same stack frame displayed with @code{set print address off}:
5351 (@value{GDBP}) set print addr off
5353 #0 set_quotes (lq="<<", rq=">>") at input.c:530
5354 530 if (lquote != def_lquote)
5358 You can use @samp{set print address off} to eliminate all machine
5359 dependent displays from the @value{GDBN} interface. For example, with
5360 @code{print address off}, you should get the same text for backtraces on
5361 all machines---whether or not they involve pointer arguments.
5364 @item show print address
5365 Show whether or not addresses are to be printed.
5368 When @value{GDBN} prints a symbolic address, it normally prints the
5369 closest earlier symbol plus an offset. If that symbol does not uniquely
5370 identify the address (for example, it is a name whose scope is a single
5371 source file), you may need to clarify. One way to do this is with
5372 @code{info line}, for example @samp{info line *0x4537}. Alternately,
5373 you can set @value{GDBN} to print the source file and line number when
5374 it prints a symbolic address:
5377 @item set print symbol-filename on
5378 @cindex closest symbol and offset for an address
5379 Tell @value{GDBN} to print the source file name and line number of a
5380 symbol in the symbolic form of an address.
5382 @item set print symbol-filename off
5383 Do not print source file name and line number of a symbol. This is the
5386 @item show print symbol-filename
5387 Show whether or not @value{GDBN} will print the source file name and
5388 line number of a symbol in the symbolic form of an address.
5391 Another situation where it is helpful to show symbol filenames and line
5392 numbers is when disassembling code; @value{GDBN} shows you the line
5393 number and source file that corresponds to each instruction.
5395 Also, you may wish to see the symbolic form only if the address being
5396 printed is reasonably close to the closest earlier symbol:
5399 @item set print max-symbolic-offset @var{max-offset}
5400 @cindex maximum value for offset of closest symbol
5401 Tell @value{GDBN} to only display the symbolic form of an address if the
5402 offset between the closest earlier symbol and the address is less than
5403 @var{max-offset}. The default is 0, which tells @value{GDBN}
5404 to always print the symbolic form of an address if any symbol precedes it.
5406 @item show print max-symbolic-offset
5407 Ask how large the maximum offset is that @value{GDBN} prints in a
5411 @cindex wild pointer, interpreting
5412 @cindex pointer, finding referent
5413 If you have a pointer and you are not sure where it points, try
5414 @samp{set print symbol-filename on}. Then you can determine the name
5415 and source file location of the variable where it points, using
5416 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
5417 For example, here @value{GDBN} shows that a variable @code{ptt} points
5418 at another variable @code{t}, defined in @file{hi2.c}:
5421 (@value{GDBP}) set print symbol-filename on
5422 (@value{GDBP}) p/a ptt
5423 $4 = 0xe008 <t in hi2.c>
5427 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
5428 does not show the symbol name and filename of the referent, even with
5429 the appropriate @code{set print} options turned on.
5432 Other settings control how different kinds of objects are printed:
5435 @item set print array
5436 @itemx set print array on
5437 @cindex pretty print arrays
5438 Pretty print arrays. This format is more convenient to read,
5439 but uses more space. The default is off.
5441 @item set print array off
5442 Return to compressed format for arrays.
5444 @item show print array
5445 Show whether compressed or pretty format is selected for displaying
5448 @item set print elements @var{number-of-elements}
5449 @cindex number of array elements to print
5450 Set a limit on how many elements of an array @value{GDBN} will print.
5451 If @value{GDBN} is printing a large array, it stops printing after it has
5452 printed the number of elements set by the @code{set print elements} command.
5453 This limit also applies to the display of strings.
5454 When @value{GDBN} starts, this limit is set to 200.
5455 Setting @var{number-of-elements} to zero means that the printing is unlimited.
5457 @item show print elements
5458 Display the number of elements of a large array that @value{GDBN} will print.
5459 If the number is 0, then the printing is unlimited.
5461 @item set print null-stop
5462 @cindex @sc{null} elements in arrays
5463 Cause @value{GDBN} to stop printing the characters of an array when the first
5464 @sc{null} is encountered. This is useful when large arrays actually
5465 contain only short strings.
5468 @item set print pretty on
5469 Cause @value{GDBN} to print structures in an indented format with one member
5470 per line, like this:
5485 @item set print pretty off
5486 Cause @value{GDBN} to print structures in a compact format, like this:
5490 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
5491 meat = 0x54 "Pork"@}
5496 This is the default format.
5498 @item show print pretty
5499 Show which format @value{GDBN} is using to print structures.
5501 @item set print sevenbit-strings on
5502 @cindex eight-bit characters in strings
5503 @cindex octal escapes in strings
5504 Print using only seven-bit characters; if this option is set,
5505 @value{GDBN} displays any eight-bit characters (in strings or
5506 character values) using the notation @code{\}@var{nnn}. This setting is
5507 best if you are working in English (@sc{ascii}) and you use the
5508 high-order bit of characters as a marker or ``meta'' bit.
5510 @item set print sevenbit-strings off
5511 Print full eight-bit characters. This allows the use of more
5512 international character sets, and is the default.
5514 @item show print sevenbit-strings
5515 Show whether or not @value{GDBN} is printing only seven-bit characters.
5517 @item set print union on
5518 @cindex unions in structures, printing
5519 Tell @value{GDBN} to print unions which are contained in structures. This
5520 is the default setting.
5522 @item set print union off
5523 Tell @value{GDBN} not to print unions which are contained in structures.
5525 @item show print union
5526 Ask @value{GDBN} whether or not it will print unions which are contained in
5529 For example, given the declarations
5532 typedef enum @{Tree, Bug@} Species;
5533 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
5534 typedef enum @{Caterpillar, Cocoon, Butterfly@}
5545 struct thing foo = @{Tree, @{Acorn@}@};
5549 with @code{set print union on} in effect @samp{p foo} would print
5552 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
5556 and with @code{set print union off} in effect it would print
5559 $1 = @{it = Tree, form = @{...@}@}
5565 These settings are of interest when debugging C@t{++} programs:
5568 @cindex demangling C@t{++} names
5569 @item set print demangle
5570 @itemx set print demangle on
5571 Print C@t{++} names in their source form rather than in the encoded
5572 (``mangled'') form passed to the assembler and linker for type-safe
5573 linkage. The default is on.
5575 @item show print demangle
5576 Show whether C@t{++} names are printed in mangled or demangled form.
5578 @item set print asm-demangle
5579 @itemx set print asm-demangle on
5580 Print C@t{++} names in their source form rather than their mangled form, even
5581 in assembler code printouts such as instruction disassemblies.
5584 @item show print asm-demangle
5585 Show whether C@t{++} names in assembly listings are printed in mangled
5588 @cindex C@t{++} symbol decoding style
5589 @cindex symbol decoding style, C@t{++}
5590 @item set demangle-style @var{style}
5591 Choose among several encoding schemes used by different compilers to
5592 represent C@t{++} names. The choices for @var{style} are currently:
5596 Allow @value{GDBN} to choose a decoding style by inspecting your program.
5599 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
5600 This is the default.
5603 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
5606 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
5609 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
5610 @strong{Warning:} this setting alone is not sufficient to allow
5611 debugging @code{cfront}-generated executables. @value{GDBN} would
5612 require further enhancement to permit that.
5615 If you omit @var{style}, you will see a list of possible formats.
5617 @item show demangle-style
5618 Display the encoding style currently in use for decoding C@t{++} symbols.
5620 @item set print object
5621 @itemx set print object on
5622 @cindex derived type of an object, printing
5623 When displaying a pointer to an object, identify the @emph{actual}
5624 (derived) type of the object rather than the @emph{declared} type, using
5625 the virtual function table.
5627 @item set print object off
5628 Display only the declared type of objects, without reference to the
5629 virtual function table. This is the default setting.
5631 @item show print object
5632 Show whether actual, or declared, object types are displayed.
5634 @item set print static-members
5635 @itemx set print static-members on
5636 @cindex static members of C@t{++} objects
5637 Print static members when displaying a C@t{++} object. The default is on.
5639 @item set print static-members off
5640 Do not print static members when displaying a C@t{++} object.
5642 @item show print static-members
5643 Show whether C@t{++} static members are printed, or not.
5645 @c These don't work with HP ANSI C++ yet.
5646 @item set print vtbl
5647 @itemx set print vtbl on
5648 @cindex pretty print C@t{++} virtual function tables
5649 Pretty print C@t{++} virtual function tables. The default is off.
5650 (The @code{vtbl} commands do not work on programs compiled with the HP
5651 ANSI C@t{++} compiler (@code{aCC}).)
5653 @item set print vtbl off
5654 Do not pretty print C@t{++} virtual function tables.
5656 @item show print vtbl
5657 Show whether C@t{++} virtual function tables are pretty printed, or not.
5661 @section Value history
5663 @cindex value history
5664 Values printed by the @code{print} command are saved in the @value{GDBN}
5665 @dfn{value history}. This allows you to refer to them in other expressions.
5666 Values are kept until the symbol table is re-read or discarded
5667 (for example with the @code{file} or @code{symbol-file} commands).
5668 When the symbol table changes, the value history is discarded,
5669 since the values may contain pointers back to the types defined in the
5674 @cindex history number
5675 The values printed are given @dfn{history numbers} by which you can
5676 refer to them. These are successive integers starting with one.
5677 @code{print} shows you the history number assigned to a value by
5678 printing @samp{$@var{num} = } before the value; here @var{num} is the
5681 To refer to any previous value, use @samp{$} followed by the value's
5682 history number. The way @code{print} labels its output is designed to
5683 remind you of this. Just @code{$} refers to the most recent value in
5684 the history, and @code{$$} refers to the value before that.
5685 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
5686 is the value just prior to @code{$$}, @code{$$1} is equivalent to
5687 @code{$$}, and @code{$$0} is equivalent to @code{$}.
5689 For example, suppose you have just printed a pointer to a structure and
5690 want to see the contents of the structure. It suffices to type
5696 If you have a chain of structures where the component @code{next} points
5697 to the next one, you can print the contents of the next one with this:
5704 You can print successive links in the chain by repeating this
5705 command---which you can do by just typing @key{RET}.
5707 Note that the history records values, not expressions. If the value of
5708 @code{x} is 4 and you type these commands:
5716 then the value recorded in the value history by the @code{print} command
5717 remains 4 even though the value of @code{x} has changed.
5722 Print the last ten values in the value history, with their item numbers.
5723 This is like @samp{p@ $$9} repeated ten times, except that @code{show
5724 values} does not change the history.
5726 @item show values @var{n}
5727 Print ten history values centered on history item number @var{n}.
5730 Print ten history values just after the values last printed. If no more
5731 values are available, @code{show values +} produces no display.
5734 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
5735 same effect as @samp{show values +}.
5737 @node Convenience Vars
5738 @section Convenience variables
5740 @cindex convenience variables
5741 @value{GDBN} provides @dfn{convenience variables} that you can use within
5742 @value{GDBN} to hold on to a value and refer to it later. These variables
5743 exist entirely within @value{GDBN}; they are not part of your program, and
5744 setting a convenience variable has no direct effect on further execution
5745 of your program. That is why you can use them freely.
5747 Convenience variables are prefixed with @samp{$}. Any name preceded by
5748 @samp{$} can be used for a convenience variable, unless it is one of
5749 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
5750 (Value history references, in contrast, are @emph{numbers} preceded
5751 by @samp{$}. @xref{Value History, ,Value history}.)
5753 You can save a value in a convenience variable with an assignment
5754 expression, just as you would set a variable in your program.
5758 set $foo = *object_ptr
5762 would save in @code{$foo} the value contained in the object pointed to by
5765 Using a convenience variable for the first time creates it, but its
5766 value is @code{void} until you assign a new value. You can alter the
5767 value with another assignment at any time.
5769 Convenience variables have no fixed types. You can assign a convenience
5770 variable any type of value, including structures and arrays, even if
5771 that variable already has a value of a different type. The convenience
5772 variable, when used as an expression, has the type of its current value.
5775 @kindex show convenience
5776 @item show convenience
5777 Print a list of convenience variables used so far, and their values.
5778 Abbreviated @code{show conv}.
5781 One of the ways to use a convenience variable is as a counter to be
5782 incremented or a pointer to be advanced. For example, to print
5783 a field from successive elements of an array of structures:
5787 print bar[$i++]->contents
5791 Repeat that command by typing @key{RET}.
5793 Some convenience variables are created automatically by @value{GDBN} and given
5794 values likely to be useful.
5797 @vindex $_@r{, convenience variable}
5799 The variable @code{$_} is automatically set by the @code{x} command to
5800 the last address examined (@pxref{Memory, ,Examining memory}). Other
5801 commands which provide a default address for @code{x} to examine also
5802 set @code{$_} to that address; these commands include @code{info line}
5803 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
5804 except when set by the @code{x} command, in which case it is a pointer
5805 to the type of @code{$__}.
5807 @vindex $__@r{, convenience variable}
5809 The variable @code{$__} is automatically set by the @code{x} command
5810 to the value found in the last address examined. Its type is chosen
5811 to match the format in which the data was printed.
5814 @vindex $_exitcode@r{, convenience variable}
5815 The variable @code{$_exitcode} is automatically set to the exit code when
5816 the program being debugged terminates.
5819 On HP-UX systems, if you refer to a function or variable name that
5820 begins with a dollar sign, @value{GDBN} searches for a user or system
5821 name first, before it searches for a convenience variable.
5827 You can refer to machine register contents, in expressions, as variables
5828 with names starting with @samp{$}. The names of registers are different
5829 for each machine; use @code{info registers} to see the names used on
5833 @kindex info registers
5834 @item info registers
5835 Print the names and values of all registers except floating-point
5836 and vector registers (in the selected stack frame).
5838 @kindex info all-registers
5839 @cindex floating point registers
5840 @item info all-registers
5841 Print the names and values of all registers, including floating-point
5842 and vector registers (in the selected stack frame).
5844 @item info registers @var{regname} @dots{}
5845 Print the @dfn{relativized} value of each specified register @var{regname}.
5846 As discussed in detail below, register values are normally relative to
5847 the selected stack frame. @var{regname} may be any register name valid on
5848 the machine you are using, with or without the initial @samp{$}.
5851 @value{GDBN} has four ``standard'' register names that are available (in
5852 expressions) on most machines---whenever they do not conflict with an
5853 architecture's canonical mnemonics for registers. The register names
5854 @code{$pc} and @code{$sp} are used for the program counter register and
5855 the stack pointer. @code{$fp} is used for a register that contains a
5856 pointer to the current stack frame, and @code{$ps} is used for a
5857 register that contains the processor status. For example,
5858 you could print the program counter in hex with
5865 or print the instruction to be executed next with
5872 or add four to the stack pointer@footnote{This is a way of removing
5873 one word from the stack, on machines where stacks grow downward in
5874 memory (most machines, nowadays). This assumes that the innermost
5875 stack frame is selected; setting @code{$sp} is not allowed when other
5876 stack frames are selected. To pop entire frames off the stack,
5877 regardless of machine architecture, use @code{return};
5878 see @ref{Returning, ,Returning from a function}.} with
5884 Whenever possible, these four standard register names are available on
5885 your machine even though the machine has different canonical mnemonics,
5886 so long as there is no conflict. The @code{info registers} command
5887 shows the canonical names. For example, on the SPARC, @code{info
5888 registers} displays the processor status register as @code{$psr} but you
5889 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
5890 is an alias for the @sc{eflags} register.
5892 @value{GDBN} always considers the contents of an ordinary register as an
5893 integer when the register is examined in this way. Some machines have
5894 special registers which can hold nothing but floating point; these
5895 registers are considered to have floating point values. There is no way
5896 to refer to the contents of an ordinary register as floating point value
5897 (although you can @emph{print} it as a floating point value with
5898 @samp{print/f $@var{regname}}).
5900 Some registers have distinct ``raw'' and ``virtual'' data formats. This
5901 means that the data format in which the register contents are saved by
5902 the operating system is not the same one that your program normally
5903 sees. For example, the registers of the 68881 floating point
5904 coprocessor are always saved in ``extended'' (raw) format, but all C
5905 programs expect to work with ``double'' (virtual) format. In such
5906 cases, @value{GDBN} normally works with the virtual format only (the format
5907 that makes sense for your program), but the @code{info registers} command
5908 prints the data in both formats.
5910 Normally, register values are relative to the selected stack frame
5911 (@pxref{Selection, ,Selecting a frame}). This means that you get the
5912 value that the register would contain if all stack frames farther in
5913 were exited and their saved registers restored. In order to see the
5914 true contents of hardware registers, you must select the innermost
5915 frame (with @samp{frame 0}).
5917 However, @value{GDBN} must deduce where registers are saved, from the machine
5918 code generated by your compiler. If some registers are not saved, or if
5919 @value{GDBN} is unable to locate the saved registers, the selected stack
5920 frame makes no difference.
5922 @node Floating Point Hardware
5923 @section Floating point hardware
5924 @cindex floating point
5926 Depending on the configuration, @value{GDBN} may be able to give
5927 you more information about the status of the floating point hardware.
5932 Display hardware-dependent information about the floating
5933 point unit. The exact contents and layout vary depending on the
5934 floating point chip. Currently, @samp{info float} is supported on
5935 the ARM and x86 machines.
5939 @section Vector Unit
5942 Depending on the configuration, @value{GDBN} may be able to give you
5943 more information about the status of the vector unit.
5948 Display information about the vector unit. The exact contents and
5949 layout vary depending on the hardware.
5952 @node Auxiliary Vector
5953 @section Operating system auxiliary vector
5954 @cindex auxiliary vector
5955 @cindex vector, auxiliary
5957 Some operating systems supply an @dfn{auxiliary vector} to programs at
5958 startup. This is akin to the arguments and environment that you
5959 specify for a program, but contains a system-dependent variety of
5960 binary values that tell system libraries important details about the
5961 hardware, operating system, and process. Each value's purpose is
5962 identified by an integer tag; the meanings are well-known but system-specific.
5963 Depending on the configuration and operating system facilities,
5964 @value{GDBN} may be able to show you this information.
5969 Display the auxiliary vector of the inferior, which can be either a
5970 live process or a core dump file. @value{GDBN} prints each tag value
5971 numerically, and also shows names and text descriptions for recognized
5972 tags. Some values in the vector are numbers, some bit masks, and some
5973 pointers to strings or other data. @value{GDBN} displays each value in the
5974 most appropriate form for a recognized tag, and in hexadecimal for
5975 an unrecognized tag.
5978 @node Memory Region Attributes
5979 @section Memory region attributes
5980 @cindex memory region attributes
5982 @dfn{Memory region attributes} allow you to describe special handling
5983 required by regions of your target's memory. @value{GDBN} uses attributes
5984 to determine whether to allow certain types of memory accesses; whether to
5985 use specific width accesses; and whether to cache target memory.
5987 Defined memory regions can be individually enabled and disabled. When a
5988 memory region is disabled, @value{GDBN} uses the default attributes when
5989 accessing memory in that region. Similarly, if no memory regions have
5990 been defined, @value{GDBN} uses the default attributes when accessing
5993 When a memory region is defined, it is given a number to identify it;
5994 to enable, disable, or remove a memory region, you specify that number.
5998 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
5999 Define memory region bounded by @var{lower} and @var{upper} with
6000 attributes @var{attributes}@dots{}. Note that @var{upper} == 0 is a
6001 special case: it is treated as the the target's maximum memory address.
6002 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
6005 @item delete mem @var{nums}@dots{}
6006 Remove memory regions @var{nums}@dots{}.
6009 @item disable mem @var{nums}@dots{}
6010 Disable memory regions @var{nums}@dots{}.
6011 A disabled memory region is not forgotten.
6012 It may be enabled again later.
6015 @item enable mem @var{nums}@dots{}
6016 Enable memory regions @var{nums}@dots{}.
6020 Print a table of all defined memory regions, with the following columns
6024 @item Memory Region Number
6025 @item Enabled or Disabled.
6026 Enabled memory regions are marked with @samp{y}.
6027 Disabled memory regions are marked with @samp{n}.
6030 The address defining the inclusive lower bound of the memory region.
6033 The address defining the exclusive upper bound of the memory region.
6036 The list of attributes set for this memory region.
6041 @subsection Attributes
6043 @subsubsection Memory Access Mode
6044 The access mode attributes set whether @value{GDBN} may make read or
6045 write accesses to a memory region.
6047 While these attributes prevent @value{GDBN} from performing invalid
6048 memory accesses, they do nothing to prevent the target system, I/O DMA,
6049 etc. from accessing memory.
6053 Memory is read only.
6055 Memory is write only.
6057 Memory is read/write. This is the default.
6060 @subsubsection Memory Access Size
6061 The acccess size attributes tells @value{GDBN} to use specific sized
6062 accesses in the memory region. Often memory mapped device registers
6063 require specific sized accesses. If no access size attribute is
6064 specified, @value{GDBN} may use accesses of any size.
6068 Use 8 bit memory accesses.
6070 Use 16 bit memory accesses.
6072 Use 32 bit memory accesses.
6074 Use 64 bit memory accesses.
6077 @c @subsubsection Hardware/Software Breakpoints
6078 @c The hardware/software breakpoint attributes set whether @value{GDBN}
6079 @c will use hardware or software breakpoints for the internal breakpoints
6080 @c used by the step, next, finish, until, etc. commands.
6084 @c Always use hardware breakpoints
6085 @c @item swbreak (default)
6088 @subsubsection Data Cache
6089 The data cache attributes set whether @value{GDBN} will cache target
6090 memory. While this generally improves performance by reducing debug
6091 protocol overhead, it can lead to incorrect results because @value{GDBN}
6092 does not know about volatile variables or memory mapped device
6097 Enable @value{GDBN} to cache target memory.
6099 Disable @value{GDBN} from caching target memory. This is the default.
6102 @c @subsubsection Memory Write Verification
6103 @c The memory write verification attributes set whether @value{GDBN}
6104 @c will re-reads data after each write to verify the write was successful.
6108 @c @item noverify (default)
6111 @node Dump/Restore Files
6112 @section Copy between memory and a file
6113 @cindex dump/restore files
6114 @cindex append data to a file
6115 @cindex dump data to a file
6116 @cindex restore data from a file
6118 You can use the commands @code{dump}, @code{append}, and
6119 @code{restore} to copy data between target memory and a file. The
6120 @code{dump} and @code{append} commands write data to a file, and the
6121 @code{restore} command reads data from a file back into the inferior's
6122 memory. Files may be in binary, Motorola S-record, Intel hex, or
6123 Tektronix Hex format; however, @value{GDBN} can only append to binary
6129 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6130 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
6131 Dump the contents of memory from @var{start_addr} to @var{end_addr},
6132 or the value of @var{expr}, to @var{filename} in the given format.
6134 The @var{format} parameter may be any one of:
6141 Motorola S-record format.
6143 Tektronix Hex format.
6146 @value{GDBN} uses the same definitions of these formats as the
6147 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
6148 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
6152 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6153 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
6154 Append the contents of memory from @var{start_addr} to @var{end_addr},
6155 or the value of @var{expr}, to @var{filename}, in raw binary form.
6156 (@value{GDBN} can only append data to files in raw binary form.)
6159 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
6160 Restore the contents of file @var{filename} into memory. The
6161 @code{restore} command can automatically recognize any known @sc{bfd}
6162 file format, except for raw binary. To restore a raw binary file you
6163 must specify the optional keyword @code{binary} after the filename.
6165 If @var{bias} is non-zero, its value will be added to the addresses
6166 contained in the file. Binary files always start at address zero, so
6167 they will be restored at address @var{bias}. Other bfd files have
6168 a built-in location; they will be restored at offset @var{bias}
6171 If @var{start} and/or @var{end} are non-zero, then only data between
6172 file offset @var{start} and file offset @var{end} will be restored.
6173 These offsets are relative to the addresses in the file, before
6174 the @var{bias} argument is applied.
6178 @node Character Sets
6179 @section Character Sets
6180 @cindex character sets
6182 @cindex translating between character sets
6183 @cindex host character set
6184 @cindex target character set
6186 If the program you are debugging uses a different character set to
6187 represent characters and strings than the one @value{GDBN} uses itself,
6188 @value{GDBN} can automatically translate between the character sets for
6189 you. The character set @value{GDBN} uses we call the @dfn{host
6190 character set}; the one the inferior program uses we call the
6191 @dfn{target character set}.
6193 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
6194 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
6195 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
6196 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
6197 then the host character set is Latin-1, and the target character set is
6198 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
6199 target-charset EBCDIC-US}, then @value{GDBN} translates between
6200 @sc{ebcdic} and Latin 1 as you print character or string values, or use
6201 character and string literals in expressions.
6203 @value{GDBN} has no way to automatically recognize which character set
6204 the inferior program uses; you must tell it, using the @code{set
6205 target-charset} command, described below.
6207 Here are the commands for controlling @value{GDBN}'s character set
6211 @item set target-charset @var{charset}
6212 @kindex set target-charset
6213 Set the current target character set to @var{charset}. We list the
6214 character set names @value{GDBN} recognizes below, but if you type
6215 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6216 list the target character sets it supports.
6220 @item set host-charset @var{charset}
6221 @kindex set host-charset
6222 Set the current host character set to @var{charset}.
6224 By default, @value{GDBN} uses a host character set appropriate to the
6225 system it is running on; you can override that default using the
6226 @code{set host-charset} command.
6228 @value{GDBN} can only use certain character sets as its host character
6229 set. We list the character set names @value{GDBN} recognizes below, and
6230 indicate which can be host character sets, but if you type
6231 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6232 list the host character sets it supports.
6234 @item set charset @var{charset}
6236 Set the current host and target character sets to @var{charset}. As
6237 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
6238 @value{GDBN} will list the name of the character sets that can be used
6239 for both host and target.
6243 @kindex show charset
6244 Show the names of the current host and target charsets.
6246 @itemx show host-charset
6247 @kindex show host-charset
6248 Show the name of the current host charset.
6250 @itemx show target-charset
6251 @kindex show target-charset
6252 Show the name of the current target charset.
6256 @value{GDBN} currently includes support for the following character
6262 @cindex ASCII character set
6263 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
6267 @cindex ISO 8859-1 character set
6268 @cindex ISO Latin 1 character set
6269 The ISO Latin 1 character set. This extends @sc{ascii} with accented
6270 characters needed for French, German, and Spanish. @value{GDBN} can use
6271 this as its host character set.
6275 @cindex EBCDIC character set
6276 @cindex IBM1047 character set
6277 Variants of the @sc{ebcdic} character set, used on some of IBM's
6278 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
6279 @value{GDBN} cannot use these as its host character set.
6283 Note that these are all single-byte character sets. More work inside
6284 GDB is needed to support multi-byte or variable-width character
6285 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
6287 Here is an example of @value{GDBN}'s character set support in action.
6288 Assume that the following source code has been placed in the file
6289 @file{charset-test.c}:
6295 = @{72, 101, 108, 108, 111, 44, 32, 119,
6296 111, 114, 108, 100, 33, 10, 0@};
6297 char ibm1047_hello[]
6298 = @{200, 133, 147, 147, 150, 107, 64, 166,
6299 150, 153, 147, 132, 90, 37, 0@};
6303 printf ("Hello, world!\n");
6307 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
6308 containing the string @samp{Hello, world!} followed by a newline,
6309 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
6311 We compile the program, and invoke the debugger on it:
6314 $ gcc -g charset-test.c -o charset-test
6315 $ gdb -nw charset-test
6316 GNU gdb 2001-12-19-cvs
6317 Copyright 2001 Free Software Foundation, Inc.
6322 We can use the @code{show charset} command to see what character sets
6323 @value{GDBN} is currently using to interpret and display characters and
6327 (@value{GDBP}) show charset
6328 The current host and target character set is `ISO-8859-1'.
6332 For the sake of printing this manual, let's use @sc{ascii} as our
6333 initial character set:
6335 (@value{GDBP}) set charset ASCII
6336 (@value{GDBP}) show charset
6337 The current host and target character set is `ASCII'.
6341 Let's assume that @sc{ascii} is indeed the correct character set for our
6342 host system --- in other words, let's assume that if @value{GDBN} prints
6343 characters using the @sc{ascii} character set, our terminal will display
6344 them properly. Since our current target character set is also
6345 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
6348 (@value{GDBP}) print ascii_hello
6349 $1 = 0x401698 "Hello, world!\n"
6350 (@value{GDBP}) print ascii_hello[0]
6355 @value{GDBN} uses the target character set for character and string
6356 literals you use in expressions:
6359 (@value{GDBP}) print '+'
6364 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
6367 @value{GDBN} relies on the user to tell it which character set the
6368 target program uses. If we print @code{ibm1047_hello} while our target
6369 character set is still @sc{ascii}, we get jibberish:
6372 (@value{GDBP}) print ibm1047_hello
6373 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
6374 (@value{GDBP}) print ibm1047_hello[0]
6379 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
6380 @value{GDBN} tells us the character sets it supports:
6383 (@value{GDBP}) set target-charset
6384 ASCII EBCDIC-US IBM1047 ISO-8859-1
6385 (@value{GDBP}) set target-charset
6388 We can select @sc{ibm1047} as our target character set, and examine the
6389 program's strings again. Now the @sc{ascii} string is wrong, but
6390 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
6391 target character set, @sc{ibm1047}, to the host character set,
6392 @sc{ascii}, and they display correctly:
6395 (@value{GDBP}) set target-charset IBM1047
6396 (@value{GDBP}) show charset
6397 The current host character set is `ASCII'.
6398 The current target character set is `IBM1047'.
6399 (@value{GDBP}) print ascii_hello
6400 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
6401 (@value{GDBP}) print ascii_hello[0]
6403 (@value{GDBP}) print ibm1047_hello
6404 $8 = 0x4016a8 "Hello, world!\n"
6405 (@value{GDBP}) print ibm1047_hello[0]
6410 As above, @value{GDBN} uses the target character set for character and
6411 string literals you use in expressions:
6414 (@value{GDBP}) print '+'
6419 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
6424 @chapter C Preprocessor Macros
6426 Some languages, such as C and C@t{++}, provide a way to define and invoke
6427 ``preprocessor macros'' which expand into strings of tokens.
6428 @value{GDBN} can evaluate expressions containing macro invocations, show
6429 the result of macro expansion, and show a macro's definition, including
6430 where it was defined.
6432 You may need to compile your program specially to provide @value{GDBN}
6433 with information about preprocessor macros. Most compilers do not
6434 include macros in their debugging information, even when you compile
6435 with the @option{-g} flag. @xref{Compilation}.
6437 A program may define a macro at one point, remove that definition later,
6438 and then provide a different definition after that. Thus, at different
6439 points in the program, a macro may have different definitions, or have
6440 no definition at all. If there is a current stack frame, @value{GDBN}
6441 uses the macros in scope at that frame's source code line. Otherwise,
6442 @value{GDBN} uses the macros in scope at the current listing location;
6445 At the moment, @value{GDBN} does not support the @code{##}
6446 token-splicing operator, the @code{#} stringification operator, or
6447 variable-arity macros.
6449 Whenever @value{GDBN} evaluates an expression, it always expands any
6450 macro invocations present in the expression. @value{GDBN} also provides
6451 the following commands for working with macros explicitly.
6455 @kindex macro expand
6456 @cindex macro expansion, showing the results of preprocessor
6457 @cindex preprocessor macro expansion, showing the results of
6458 @cindex expanding preprocessor macros
6459 @item macro expand @var{expression}
6460 @itemx macro exp @var{expression}
6461 Show the results of expanding all preprocessor macro invocations in
6462 @var{expression}. Since @value{GDBN} simply expands macros, but does
6463 not parse the result, @var{expression} need not be a valid expression;
6464 it can be any string of tokens.
6466 @item macro expand-once @var{expression}
6467 @itemx macro exp1 @var{expression}
6468 @cindex expand macro once
6469 @i{(This command is not yet implemented.)} Show the results of
6470 expanding those preprocessor macro invocations that appear explicitly in
6471 @var{expression}. Macro invocations appearing in that expansion are
6472 left unchanged. This command allows you to see the effect of a
6473 particular macro more clearly, without being confused by further
6474 expansions. Since @value{GDBN} simply expands macros, but does not
6475 parse the result, @var{expression} need not be a valid expression; it
6476 can be any string of tokens.
6479 @cindex macro definition, showing
6480 @cindex definition, showing a macro's
6481 @item info macro @var{macro}
6482 Show the definition of the macro named @var{macro}, and describe the
6483 source location where that definition was established.
6485 @kindex macro define
6486 @cindex user-defined macros
6487 @cindex defining macros interactively
6488 @cindex macros, user-defined
6489 @item macro define @var{macro} @var{replacement-list}
6490 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
6491 @i{(This command is not yet implemented.)} Introduce a definition for a
6492 preprocessor macro named @var{macro}, invocations of which are replaced
6493 by the tokens given in @var{replacement-list}. The first form of this
6494 command defines an ``object-like'' macro, which takes no arguments; the
6495 second form defines a ``function-like'' macro, which takes the arguments
6496 given in @var{arglist}.
6498 A definition introduced by this command is in scope in every expression
6499 evaluated in @value{GDBN}, until it is removed with the @command{macro
6500 undef} command, described below. The definition overrides all
6501 definitions for @var{macro} present in the program being debugged, as
6502 well as any previous user-supplied definition.
6505 @item macro undef @var{macro}
6506 @i{(This command is not yet implemented.)} Remove any user-supplied
6507 definition for the macro named @var{macro}. This command only affects
6508 definitions provided with the @command{macro define} command, described
6509 above; it cannot remove definitions present in the program being
6514 @cindex macros, example of debugging with
6515 Here is a transcript showing the above commands in action. First, we
6516 show our source files:
6524 #define ADD(x) (M + x)
6529 printf ("Hello, world!\n");
6531 printf ("We're so creative.\n");
6533 printf ("Goodbye, world!\n");
6540 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
6541 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
6542 compiler includes information about preprocessor macros in the debugging
6546 $ gcc -gdwarf-2 -g3 sample.c -o sample
6550 Now, we start @value{GDBN} on our sample program:
6554 GNU gdb 2002-05-06-cvs
6555 Copyright 2002 Free Software Foundation, Inc.
6556 GDB is free software, @dots{}
6560 We can expand macros and examine their definitions, even when the
6561 program is not running. @value{GDBN} uses the current listing position
6562 to decide which macro definitions are in scope:
6565 (@value{GDBP}) list main
6568 5 #define ADD(x) (M + x)
6573 10 printf ("Hello, world!\n");
6575 12 printf ("We're so creative.\n");
6576 (@value{GDBP}) info macro ADD
6577 Defined at /home/jimb/gdb/macros/play/sample.c:5
6578 #define ADD(x) (M + x)
6579 (@value{GDBP}) info macro Q
6580 Defined at /home/jimb/gdb/macros/play/sample.h:1
6581 included at /home/jimb/gdb/macros/play/sample.c:2
6583 (@value{GDBP}) macro expand ADD(1)
6584 expands to: (42 + 1)
6585 (@value{GDBP}) macro expand-once ADD(1)
6586 expands to: once (M + 1)
6590 In the example above, note that @command{macro expand-once} expands only
6591 the macro invocation explicit in the original text --- the invocation of
6592 @code{ADD} --- but does not expand the invocation of the macro @code{M},
6593 which was introduced by @code{ADD}.
6595 Once the program is running, GDB uses the macro definitions in force at
6596 the source line of the current stack frame:
6599 (@value{GDBP}) break main
6600 Breakpoint 1 at 0x8048370: file sample.c, line 10.
6602 Starting program: /home/jimb/gdb/macros/play/sample
6604 Breakpoint 1, main () at sample.c:10
6605 10 printf ("Hello, world!\n");
6609 At line 10, the definition of the macro @code{N} at line 9 is in force:
6612 (@value{GDBP}) info macro N
6613 Defined at /home/jimb/gdb/macros/play/sample.c:9
6615 (@value{GDBP}) macro expand N Q M
6617 (@value{GDBP}) print N Q M
6622 As we step over directives that remove @code{N}'s definition, and then
6623 give it a new definition, @value{GDBN} finds the definition (or lack
6624 thereof) in force at each point:
6629 12 printf ("We're so creative.\n");
6630 (@value{GDBP}) info macro N
6631 The symbol `N' has no definition as a C/C++ preprocessor macro
6632 at /home/jimb/gdb/macros/play/sample.c:12
6635 14 printf ("Goodbye, world!\n");
6636 (@value{GDBP}) info macro N
6637 Defined at /home/jimb/gdb/macros/play/sample.c:13
6639 (@value{GDBP}) macro expand N Q M
6640 expands to: 1729 < 42
6641 (@value{GDBP}) print N Q M
6648 @chapter Tracepoints
6649 @c This chapter is based on the documentation written by Michael
6650 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
6653 In some applications, it is not feasible for the debugger to interrupt
6654 the program's execution long enough for the developer to learn
6655 anything helpful about its behavior. If the program's correctness
6656 depends on its real-time behavior, delays introduced by a debugger
6657 might cause the program to change its behavior drastically, or perhaps
6658 fail, even when the code itself is correct. It is useful to be able
6659 to observe the program's behavior without interrupting it.
6661 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
6662 specify locations in the program, called @dfn{tracepoints}, and
6663 arbitrary expressions to evaluate when those tracepoints are reached.
6664 Later, using the @code{tfind} command, you can examine the values
6665 those expressions had when the program hit the tracepoints. The
6666 expressions may also denote objects in memory---structures or arrays,
6667 for example---whose values @value{GDBN} should record; while visiting
6668 a particular tracepoint, you may inspect those objects as if they were
6669 in memory at that moment. However, because @value{GDBN} records these
6670 values without interacting with you, it can do so quickly and
6671 unobtrusively, hopefully not disturbing the program's behavior.
6673 The tracepoint facility is currently available only for remote
6674 targets. @xref{Targets}. In addition, your remote target must know how
6675 to collect trace data. This functionality is implemented in the remote
6676 stub; however, none of the stubs distributed with @value{GDBN} support
6677 tracepoints as of this writing.
6679 This chapter describes the tracepoint commands and features.
6683 * Analyze Collected Data::
6684 * Tracepoint Variables::
6687 @node Set Tracepoints
6688 @section Commands to Set Tracepoints
6690 Before running such a @dfn{trace experiment}, an arbitrary number of
6691 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
6692 tracepoint has a number assigned to it by @value{GDBN}. Like with
6693 breakpoints, tracepoint numbers are successive integers starting from
6694 one. Many of the commands associated with tracepoints take the
6695 tracepoint number as their argument, to identify which tracepoint to
6698 For each tracepoint, you can specify, in advance, some arbitrary set
6699 of data that you want the target to collect in the trace buffer when
6700 it hits that tracepoint. The collected data can include registers,
6701 local variables, or global data. Later, you can use @value{GDBN}
6702 commands to examine the values these data had at the time the
6705 This section describes commands to set tracepoints and associated
6706 conditions and actions.
6709 * Create and Delete Tracepoints::
6710 * Enable and Disable Tracepoints::
6711 * Tracepoint Passcounts::
6712 * Tracepoint Actions::
6713 * Listing Tracepoints::
6714 * Starting and Stopping Trace Experiment::
6717 @node Create and Delete Tracepoints
6718 @subsection Create and Delete Tracepoints
6721 @cindex set tracepoint
6724 The @code{trace} command is very similar to the @code{break} command.
6725 Its argument can be a source line, a function name, or an address in
6726 the target program. @xref{Set Breaks}. The @code{trace} command
6727 defines a tracepoint, which is a point in the target program where the
6728 debugger will briefly stop, collect some data, and then allow the
6729 program to continue. Setting a tracepoint or changing its commands
6730 doesn't take effect until the next @code{tstart} command; thus, you
6731 cannot change the tracepoint attributes once a trace experiment is
6734 Here are some examples of using the @code{trace} command:
6737 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
6739 (@value{GDBP}) @b{trace +2} // 2 lines forward
6741 (@value{GDBP}) @b{trace my_function} // first source line of function
6743 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
6745 (@value{GDBP}) @b{trace *0x2117c4} // an address
6749 You can abbreviate @code{trace} as @code{tr}.
6752 @cindex last tracepoint number
6753 @cindex recent tracepoint number
6754 @cindex tracepoint number
6755 The convenience variable @code{$tpnum} records the tracepoint number
6756 of the most recently set tracepoint.
6758 @kindex delete tracepoint
6759 @cindex tracepoint deletion
6760 @item delete tracepoint @r{[}@var{num}@r{]}
6761 Permanently delete one or more tracepoints. With no argument, the
6762 default is to delete all tracepoints.
6767 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
6769 (@value{GDBP}) @b{delete trace} // remove all tracepoints
6773 You can abbreviate this command as @code{del tr}.
6776 @node Enable and Disable Tracepoints
6777 @subsection Enable and Disable Tracepoints
6780 @kindex disable tracepoint
6781 @item disable tracepoint @r{[}@var{num}@r{]}
6782 Disable tracepoint @var{num}, or all tracepoints if no argument
6783 @var{num} is given. A disabled tracepoint will have no effect during
6784 the next trace experiment, but it is not forgotten. You can re-enable
6785 a disabled tracepoint using the @code{enable tracepoint} command.
6787 @kindex enable tracepoint
6788 @item enable tracepoint @r{[}@var{num}@r{]}
6789 Enable tracepoint @var{num}, or all tracepoints. The enabled
6790 tracepoints will become effective the next time a trace experiment is
6794 @node Tracepoint Passcounts
6795 @subsection Tracepoint Passcounts
6799 @cindex tracepoint pass count
6800 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
6801 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
6802 automatically stop a trace experiment. If a tracepoint's passcount is
6803 @var{n}, then the trace experiment will be automatically stopped on
6804 the @var{n}'th time that tracepoint is hit. If the tracepoint number
6805 @var{num} is not specified, the @code{passcount} command sets the
6806 passcount of the most recently defined tracepoint. If no passcount is
6807 given, the trace experiment will run until stopped explicitly by the
6813 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
6814 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
6816 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
6817 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
6818 (@value{GDBP}) @b{trace foo}
6819 (@value{GDBP}) @b{pass 3}
6820 (@value{GDBP}) @b{trace bar}
6821 (@value{GDBP}) @b{pass 2}
6822 (@value{GDBP}) @b{trace baz}
6823 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
6824 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
6825 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
6826 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
6830 @node Tracepoint Actions
6831 @subsection Tracepoint Action Lists
6835 @cindex tracepoint actions
6836 @item actions @r{[}@var{num}@r{]}
6837 This command will prompt for a list of actions to be taken when the
6838 tracepoint is hit. If the tracepoint number @var{num} is not
6839 specified, this command sets the actions for the one that was most
6840 recently defined (so that you can define a tracepoint and then say
6841 @code{actions} without bothering about its number). You specify the
6842 actions themselves on the following lines, one action at a time, and
6843 terminate the actions list with a line containing just @code{end}. So
6844 far, the only defined actions are @code{collect} and
6845 @code{while-stepping}.
6847 @cindex remove actions from a tracepoint
6848 To remove all actions from a tracepoint, type @samp{actions @var{num}}
6849 and follow it immediately with @samp{end}.
6852 (@value{GDBP}) @b{collect @var{data}} // collect some data
6854 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
6856 (@value{GDBP}) @b{end} // signals the end of actions.
6859 In the following example, the action list begins with @code{collect}
6860 commands indicating the things to be collected when the tracepoint is
6861 hit. Then, in order to single-step and collect additional data
6862 following the tracepoint, a @code{while-stepping} command is used,
6863 followed by the list of things to be collected while stepping. The
6864 @code{while-stepping} command is terminated by its own separate
6865 @code{end} command. Lastly, the action list is terminated by an
6869 (@value{GDBP}) @b{trace foo}
6870 (@value{GDBP}) @b{actions}
6871 Enter actions for tracepoint 1, one per line:
6880 @kindex collect @r{(tracepoints)}
6881 @item collect @var{expr1}, @var{expr2}, @dots{}
6882 Collect values of the given expressions when the tracepoint is hit.
6883 This command accepts a comma-separated list of any valid expressions.
6884 In addition to global, static, or local variables, the following
6885 special arguments are supported:
6889 collect all registers
6892 collect all function arguments
6895 collect all local variables.
6898 You can give several consecutive @code{collect} commands, each one
6899 with a single argument, or one @code{collect} command with several
6900 arguments separated by commas: the effect is the same.
6902 The command @code{info scope} (@pxref{Symbols, info scope}) is
6903 particularly useful for figuring out what data to collect.
6905 @kindex while-stepping @r{(tracepoints)}
6906 @item while-stepping @var{n}
6907 Perform @var{n} single-step traces after the tracepoint, collecting
6908 new data at each step. The @code{while-stepping} command is
6909 followed by the list of what to collect while stepping (followed by
6910 its own @code{end} command):
6914 > collect $regs, myglobal
6920 You may abbreviate @code{while-stepping} as @code{ws} or
6924 @node Listing Tracepoints
6925 @subsection Listing Tracepoints
6928 @kindex info tracepoints
6929 @cindex information about tracepoints
6930 @item info tracepoints @r{[}@var{num}@r{]}
6931 Display information about the tracepoint @var{num}. If you don't specify
6932 a tracepoint number, displays information about all the tracepoints
6933 defined so far. For each tracepoint, the following information is
6940 whether it is enabled or disabled
6944 its passcount as given by the @code{passcount @var{n}} command
6946 its step count as given by the @code{while-stepping @var{n}} command
6948 where in the source files is the tracepoint set
6950 its action list as given by the @code{actions} command
6954 (@value{GDBP}) @b{info trace}
6955 Num Enb Address PassC StepC What
6956 1 y 0x002117c4 0 0 <gdb_asm>
6957 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
6958 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
6963 This command can be abbreviated @code{info tp}.
6966 @node Starting and Stopping Trace Experiment
6967 @subsection Starting and Stopping Trace Experiment
6971 @cindex start a new trace experiment
6972 @cindex collected data discarded
6974 This command takes no arguments. It starts the trace experiment, and
6975 begins collecting data. This has the side effect of discarding all
6976 the data collected in the trace buffer during the previous trace
6980 @cindex stop a running trace experiment
6982 This command takes no arguments. It ends the trace experiment, and
6983 stops collecting data.
6985 @strong{Note:} a trace experiment and data collection may stop
6986 automatically if any tracepoint's passcount is reached
6987 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
6990 @cindex status of trace data collection
6991 @cindex trace experiment, status of
6993 This command displays the status of the current trace data
6997 Here is an example of the commands we described so far:
7000 (@value{GDBP}) @b{trace gdb_c_test}
7001 (@value{GDBP}) @b{actions}
7002 Enter actions for tracepoint #1, one per line.
7003 > collect $regs,$locals,$args
7008 (@value{GDBP}) @b{tstart}
7009 [time passes @dots{}]
7010 (@value{GDBP}) @b{tstop}
7014 @node Analyze Collected Data
7015 @section Using the collected data
7017 After the tracepoint experiment ends, you use @value{GDBN} commands
7018 for examining the trace data. The basic idea is that each tracepoint
7019 collects a trace @dfn{snapshot} every time it is hit and another
7020 snapshot every time it single-steps. All these snapshots are
7021 consecutively numbered from zero and go into a buffer, and you can
7022 examine them later. The way you examine them is to @dfn{focus} on a
7023 specific trace snapshot. When the remote stub is focused on a trace
7024 snapshot, it will respond to all @value{GDBN} requests for memory and
7025 registers by reading from the buffer which belongs to that snapshot,
7026 rather than from @emph{real} memory or registers of the program being
7027 debugged. This means that @strong{all} @value{GDBN} commands
7028 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
7029 behave as if we were currently debugging the program state as it was
7030 when the tracepoint occurred. Any requests for data that are not in
7031 the buffer will fail.
7034 * tfind:: How to select a trace snapshot
7035 * tdump:: How to display all data for a snapshot
7036 * save-tracepoints:: How to save tracepoints for a future run
7040 @subsection @code{tfind @var{n}}
7043 @cindex select trace snapshot
7044 @cindex find trace snapshot
7045 The basic command for selecting a trace snapshot from the buffer is
7046 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
7047 counting from zero. If no argument @var{n} is given, the next
7048 snapshot is selected.
7050 Here are the various forms of using the @code{tfind} command.
7054 Find the first snapshot in the buffer. This is a synonym for
7055 @code{tfind 0} (since 0 is the number of the first snapshot).
7058 Stop debugging trace snapshots, resume @emph{live} debugging.
7061 Same as @samp{tfind none}.
7064 No argument means find the next trace snapshot.
7067 Find the previous trace snapshot before the current one. This permits
7068 retracing earlier steps.
7070 @item tfind tracepoint @var{num}
7071 Find the next snapshot associated with tracepoint @var{num}. Search
7072 proceeds forward from the last examined trace snapshot. If no
7073 argument @var{num} is given, it means find the next snapshot collected
7074 for the same tracepoint as the current snapshot.
7076 @item tfind pc @var{addr}
7077 Find the next snapshot associated with the value @var{addr} of the
7078 program counter. Search proceeds forward from the last examined trace
7079 snapshot. If no argument @var{addr} is given, it means find the next
7080 snapshot with the same value of PC as the current snapshot.
7082 @item tfind outside @var{addr1}, @var{addr2}
7083 Find the next snapshot whose PC is outside the given range of
7086 @item tfind range @var{addr1}, @var{addr2}
7087 Find the next snapshot whose PC is between @var{addr1} and
7088 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
7090 @item tfind line @r{[}@var{file}:@r{]}@var{n}
7091 Find the next snapshot associated with the source line @var{n}. If
7092 the optional argument @var{file} is given, refer to line @var{n} in
7093 that source file. Search proceeds forward from the last examined
7094 trace snapshot. If no argument @var{n} is given, it means find the
7095 next line other than the one currently being examined; thus saying
7096 @code{tfind line} repeatedly can appear to have the same effect as
7097 stepping from line to line in a @emph{live} debugging session.
7100 The default arguments for the @code{tfind} commands are specifically
7101 designed to make it easy to scan through the trace buffer. For
7102 instance, @code{tfind} with no argument selects the next trace
7103 snapshot, and @code{tfind -} with no argument selects the previous
7104 trace snapshot. So, by giving one @code{tfind} command, and then
7105 simply hitting @key{RET} repeatedly you can examine all the trace
7106 snapshots in order. Or, by saying @code{tfind -} and then hitting
7107 @key{RET} repeatedly you can examine the snapshots in reverse order.
7108 The @code{tfind line} command with no argument selects the snapshot
7109 for the next source line executed. The @code{tfind pc} command with
7110 no argument selects the next snapshot with the same program counter
7111 (PC) as the current frame. The @code{tfind tracepoint} command with
7112 no argument selects the next trace snapshot collected by the same
7113 tracepoint as the current one.
7115 In addition to letting you scan through the trace buffer manually,
7116 these commands make it easy to construct @value{GDBN} scripts that
7117 scan through the trace buffer and print out whatever collected data
7118 you are interested in. Thus, if we want to examine the PC, FP, and SP
7119 registers from each trace frame in the buffer, we can say this:
7122 (@value{GDBP}) @b{tfind start}
7123 (@value{GDBP}) @b{while ($trace_frame != -1)}
7124 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
7125 $trace_frame, $pc, $sp, $fp
7129 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
7130 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
7131 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
7132 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
7133 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
7134 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
7135 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
7136 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
7137 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
7138 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
7139 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
7142 Or, if we want to examine the variable @code{X} at each source line in
7146 (@value{GDBP}) @b{tfind start}
7147 (@value{GDBP}) @b{while ($trace_frame != -1)}
7148 > printf "Frame %d, X == %d\n", $trace_frame, X
7158 @subsection @code{tdump}
7160 @cindex dump all data collected at tracepoint
7161 @cindex tracepoint data, display
7163 This command takes no arguments. It prints all the data collected at
7164 the current trace snapshot.
7167 (@value{GDBP}) @b{trace 444}
7168 (@value{GDBP}) @b{actions}
7169 Enter actions for tracepoint #2, one per line:
7170 > collect $regs, $locals, $args, gdb_long_test
7173 (@value{GDBP}) @b{tstart}
7175 (@value{GDBP}) @b{tfind line 444}
7176 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
7178 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
7180 (@value{GDBP}) @b{tdump}
7181 Data collected at tracepoint 2, trace frame 1:
7182 d0 0xc4aa0085 -995491707
7186 d4 0x71aea3d 119204413
7191 a1 0x3000668 50333288
7194 a4 0x3000698 50333336
7196 fp 0x30bf3c 0x30bf3c
7197 sp 0x30bf34 0x30bf34
7199 pc 0x20b2c8 0x20b2c8
7203 p = 0x20e5b4 "gdb-test"
7210 gdb_long_test = 17 '\021'
7215 @node save-tracepoints
7216 @subsection @code{save-tracepoints @var{filename}}
7217 @kindex save-tracepoints
7218 @cindex save tracepoints for future sessions
7220 This command saves all current tracepoint definitions together with
7221 their actions and passcounts, into a file @file{@var{filename}}
7222 suitable for use in a later debugging session. To read the saved
7223 tracepoint definitions, use the @code{source} command (@pxref{Command
7226 @node Tracepoint Variables
7227 @section Convenience Variables for Tracepoints
7228 @cindex tracepoint variables
7229 @cindex convenience variables for tracepoints
7232 @vindex $trace_frame
7233 @item (int) $trace_frame
7234 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
7235 snapshot is selected.
7238 @item (int) $tracepoint
7239 The tracepoint for the current trace snapshot.
7242 @item (int) $trace_line
7243 The line number for the current trace snapshot.
7246 @item (char []) $trace_file
7247 The source file for the current trace snapshot.
7250 @item (char []) $trace_func
7251 The name of the function containing @code{$tracepoint}.
7254 Note: @code{$trace_file} is not suitable for use in @code{printf},
7255 use @code{output} instead.
7257 Here's a simple example of using these convenience variables for
7258 stepping through all the trace snapshots and printing some of their
7262 (@value{GDBP}) @b{tfind start}
7264 (@value{GDBP}) @b{while $trace_frame != -1}
7265 > output $trace_file
7266 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
7272 @chapter Debugging Programs That Use Overlays
7275 If your program is too large to fit completely in your target system's
7276 memory, you can sometimes use @dfn{overlays} to work around this
7277 problem. @value{GDBN} provides some support for debugging programs that
7281 * How Overlays Work:: A general explanation of overlays.
7282 * Overlay Commands:: Managing overlays in @value{GDBN}.
7283 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
7284 mapped by asking the inferior.
7285 * Overlay Sample Program:: A sample program using overlays.
7288 @node How Overlays Work
7289 @section How Overlays Work
7290 @cindex mapped overlays
7291 @cindex unmapped overlays
7292 @cindex load address, overlay's
7293 @cindex mapped address
7294 @cindex overlay area
7296 Suppose you have a computer whose instruction address space is only 64
7297 kilobytes long, but which has much more memory which can be accessed by
7298 other means: special instructions, segment registers, or memory
7299 management hardware, for example. Suppose further that you want to
7300 adapt a program which is larger than 64 kilobytes to run on this system.
7302 One solution is to identify modules of your program which are relatively
7303 independent, and need not call each other directly; call these modules
7304 @dfn{overlays}. Separate the overlays from the main program, and place
7305 their machine code in the larger memory. Place your main program in
7306 instruction memory, but leave at least enough space there to hold the
7307 largest overlay as well.
7309 Now, to call a function located in an overlay, you must first copy that
7310 overlay's machine code from the large memory into the space set aside
7311 for it in the instruction memory, and then jump to its entry point
7314 @c NB: In the below the mapped area's size is greater or equal to the
7315 @c size of all overlays. This is intentional to remind the developer
7316 @c that overlays don't necessarily need to be the same size.
7320 Data Instruction Larger
7321 Address Space Address Space Address Space
7322 +-----------+ +-----------+ +-----------+
7324 +-----------+ +-----------+ +-----------+<-- overlay 1
7325 | program | | main | .----| overlay 1 | load address
7326 | variables | | program | | +-----------+
7327 | and heap | | | | | |
7328 +-----------+ | | | +-----------+<-- overlay 2
7329 | | +-----------+ | | | load address
7330 +-----------+ | | | .-| overlay 2 |
7332 mapped --->+-----------+ | | +-----------+
7334 | overlay | <-' | | |
7335 | area | <---' +-----------+<-- overlay 3
7336 | | <---. | | load address
7337 +-----------+ `--| overlay 3 |
7344 @anchor{A code overlay}A code overlay
7348 The diagram (@pxref{A code overlay}) shows a system with separate data
7349 and instruction address spaces. To map an overlay, the program copies
7350 its code from the larger address space to the instruction address space.
7351 Since the overlays shown here all use the same mapped address, only one
7352 may be mapped at a time. For a system with a single address space for
7353 data and instructions, the diagram would be similar, except that the
7354 program variables and heap would share an address space with the main
7355 program and the overlay area.
7357 An overlay loaded into instruction memory and ready for use is called a
7358 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
7359 instruction memory. An overlay not present (or only partially present)
7360 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
7361 is its address in the larger memory. The mapped address is also called
7362 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
7363 called the @dfn{load memory address}, or @dfn{LMA}.
7365 Unfortunately, overlays are not a completely transparent way to adapt a
7366 program to limited instruction memory. They introduce a new set of
7367 global constraints you must keep in mind as you design your program:
7372 Before calling or returning to a function in an overlay, your program
7373 must make sure that overlay is actually mapped. Otherwise, the call or
7374 return will transfer control to the right address, but in the wrong
7375 overlay, and your program will probably crash.
7378 If the process of mapping an overlay is expensive on your system, you
7379 will need to choose your overlays carefully to minimize their effect on
7380 your program's performance.
7383 The executable file you load onto your system must contain each
7384 overlay's instructions, appearing at the overlay's load address, not its
7385 mapped address. However, each overlay's instructions must be relocated
7386 and its symbols defined as if the overlay were at its mapped address.
7387 You can use GNU linker scripts to specify different load and relocation
7388 addresses for pieces of your program; see @ref{Overlay Description,,,
7389 ld.info, Using ld: the GNU linker}.
7392 The procedure for loading executable files onto your system must be able
7393 to load their contents into the larger address space as well as the
7394 instruction and data spaces.
7398 The overlay system described above is rather simple, and could be
7399 improved in many ways:
7404 If your system has suitable bank switch registers or memory management
7405 hardware, you could use those facilities to make an overlay's load area
7406 contents simply appear at their mapped address in instruction space.
7407 This would probably be faster than copying the overlay to its mapped
7408 area in the usual way.
7411 If your overlays are small enough, you could set aside more than one
7412 overlay area, and have more than one overlay mapped at a time.
7415 You can use overlays to manage data, as well as instructions. In
7416 general, data overlays are even less transparent to your design than
7417 code overlays: whereas code overlays only require care when you call or
7418 return to functions, data overlays require care every time you access
7419 the data. Also, if you change the contents of a data overlay, you
7420 must copy its contents back out to its load address before you can copy a
7421 different data overlay into the same mapped area.
7426 @node Overlay Commands
7427 @section Overlay Commands
7429 To use @value{GDBN}'s overlay support, each overlay in your program must
7430 correspond to a separate section of the executable file. The section's
7431 virtual memory address and load memory address must be the overlay's
7432 mapped and load addresses. Identifying overlays with sections allows
7433 @value{GDBN} to determine the appropriate address of a function or
7434 variable, depending on whether the overlay is mapped or not.
7436 @value{GDBN}'s overlay commands all start with the word @code{overlay};
7437 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
7442 Disable @value{GDBN}'s overlay support. When overlay support is
7443 disabled, @value{GDBN} assumes that all functions and variables are
7444 always present at their mapped addresses. By default, @value{GDBN}'s
7445 overlay support is disabled.
7447 @item overlay manual
7448 @cindex manual overlay debugging
7449 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
7450 relies on you to tell it which overlays are mapped, and which are not,
7451 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
7452 commands described below.
7454 @item overlay map-overlay @var{overlay}
7455 @itemx overlay map @var{overlay}
7456 @cindex map an overlay
7457 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
7458 be the name of the object file section containing the overlay. When an
7459 overlay is mapped, @value{GDBN} assumes it can find the overlay's
7460 functions and variables at their mapped addresses. @value{GDBN} assumes
7461 that any other overlays whose mapped ranges overlap that of
7462 @var{overlay} are now unmapped.
7464 @item overlay unmap-overlay @var{overlay}
7465 @itemx overlay unmap @var{overlay}
7466 @cindex unmap an overlay
7467 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
7468 must be the name of the object file section containing the overlay.
7469 When an overlay is unmapped, @value{GDBN} assumes it can find the
7470 overlay's functions and variables at their load addresses.
7473 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
7474 consults a data structure the overlay manager maintains in the inferior
7475 to see which overlays are mapped. For details, see @ref{Automatic
7478 @item overlay load-target
7480 @cindex reloading the overlay table
7481 Re-read the overlay table from the inferior. Normally, @value{GDBN}
7482 re-reads the table @value{GDBN} automatically each time the inferior
7483 stops, so this command should only be necessary if you have changed the
7484 overlay mapping yourself using @value{GDBN}. This command is only
7485 useful when using automatic overlay debugging.
7487 @item overlay list-overlays
7489 @cindex listing mapped overlays
7490 Display a list of the overlays currently mapped, along with their mapped
7491 addresses, load addresses, and sizes.
7495 Normally, when @value{GDBN} prints a code address, it includes the name
7496 of the function the address falls in:
7499 (@value{GDBP}) print main
7500 $3 = @{int ()@} 0x11a0 <main>
7503 When overlay debugging is enabled, @value{GDBN} recognizes code in
7504 unmapped overlays, and prints the names of unmapped functions with
7505 asterisks around them. For example, if @code{foo} is a function in an
7506 unmapped overlay, @value{GDBN} prints it this way:
7509 (@value{GDBP}) overlay list
7510 No sections are mapped.
7511 (@value{GDBP}) print foo
7512 $5 = @{int (int)@} 0x100000 <*foo*>
7515 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
7519 (@value{GDBP}) overlay list
7520 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
7521 mapped at 0x1016 - 0x104a
7522 (@value{GDBP}) print foo
7523 $6 = @{int (int)@} 0x1016 <foo>
7526 When overlay debugging is enabled, @value{GDBN} can find the correct
7527 address for functions and variables in an overlay, whether or not the
7528 overlay is mapped. This allows most @value{GDBN} commands, like
7529 @code{break} and @code{disassemble}, to work normally, even on unmapped
7530 code. However, @value{GDBN}'s breakpoint support has some limitations:
7534 @cindex breakpoints in overlays
7535 @cindex overlays, setting breakpoints in
7536 You can set breakpoints in functions in unmapped overlays, as long as
7537 @value{GDBN} can write to the overlay at its load address.
7539 @value{GDBN} can not set hardware or simulator-based breakpoints in
7540 unmapped overlays. However, if you set a breakpoint at the end of your
7541 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
7542 you are using manual overlay management), @value{GDBN} will re-set its
7543 breakpoints properly.
7547 @node Automatic Overlay Debugging
7548 @section Automatic Overlay Debugging
7549 @cindex automatic overlay debugging
7551 @value{GDBN} can automatically track which overlays are mapped and which
7552 are not, given some simple co-operation from the overlay manager in the
7553 inferior. If you enable automatic overlay debugging with the
7554 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
7555 looks in the inferior's memory for certain variables describing the
7556 current state of the overlays.
7558 Here are the variables your overlay manager must define to support
7559 @value{GDBN}'s automatic overlay debugging:
7563 @item @code{_ovly_table}:
7564 This variable must be an array of the following structures:
7569 /* The overlay's mapped address. */
7572 /* The size of the overlay, in bytes. */
7575 /* The overlay's load address. */
7578 /* Non-zero if the overlay is currently mapped;
7580 unsigned long mapped;
7584 @item @code{_novlys}:
7585 This variable must be a four-byte signed integer, holding the total
7586 number of elements in @code{_ovly_table}.
7590 To decide whether a particular overlay is mapped or not, @value{GDBN}
7591 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
7592 @code{lma} members equal the VMA and LMA of the overlay's section in the
7593 executable file. When @value{GDBN} finds a matching entry, it consults
7594 the entry's @code{mapped} member to determine whether the overlay is
7597 In addition, your overlay manager may define a function called
7598 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
7599 will silently set a breakpoint there. If the overlay manager then
7600 calls this function whenever it has changed the overlay table, this
7601 will enable @value{GDBN} to accurately keep track of which overlays
7602 are in program memory, and update any breakpoints that may be set
7603 in overlays. This will allow breakpoints to work even if the
7604 overlays are kept in ROM or other non-writable memory while they
7605 are not being executed.
7607 @node Overlay Sample Program
7608 @section Overlay Sample Program
7609 @cindex overlay example program
7611 When linking a program which uses overlays, you must place the overlays
7612 at their load addresses, while relocating them to run at their mapped
7613 addresses. To do this, you must write a linker script (@pxref{Overlay
7614 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
7615 since linker scripts are specific to a particular host system, target
7616 architecture, and target memory layout, this manual cannot provide
7617 portable sample code demonstrating @value{GDBN}'s overlay support.
7619 However, the @value{GDBN} source distribution does contain an overlaid
7620 program, with linker scripts for a few systems, as part of its test
7621 suite. The program consists of the following files from
7622 @file{gdb/testsuite/gdb.base}:
7626 The main program file.
7628 A simple overlay manager, used by @file{overlays.c}.
7633 Overlay modules, loaded and used by @file{overlays.c}.
7636 Linker scripts for linking the test program on the @code{d10v-elf}
7637 and @code{m32r-elf} targets.
7640 You can build the test program using the @code{d10v-elf} GCC
7641 cross-compiler like this:
7644 $ d10v-elf-gcc -g -c overlays.c
7645 $ d10v-elf-gcc -g -c ovlymgr.c
7646 $ d10v-elf-gcc -g -c foo.c
7647 $ d10v-elf-gcc -g -c bar.c
7648 $ d10v-elf-gcc -g -c baz.c
7649 $ d10v-elf-gcc -g -c grbx.c
7650 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
7651 baz.o grbx.o -Wl,-Td10v.ld -o overlays
7654 The build process is identical for any other architecture, except that
7655 you must substitute the appropriate compiler and linker script for the
7656 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
7660 @chapter Using @value{GDBN} with Different Languages
7663 Although programming languages generally have common aspects, they are
7664 rarely expressed in the same manner. For instance, in ANSI C,
7665 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
7666 Modula-2, it is accomplished by @code{p^}. Values can also be
7667 represented (and displayed) differently. Hex numbers in C appear as
7668 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
7670 @cindex working language
7671 Language-specific information is built into @value{GDBN} for some languages,
7672 allowing you to express operations like the above in your program's
7673 native language, and allowing @value{GDBN} to output values in a manner
7674 consistent with the syntax of your program's native language. The
7675 language you use to build expressions is called the @dfn{working
7679 * Setting:: Switching between source languages
7680 * Show:: Displaying the language
7681 * Checks:: Type and range checks
7682 * Support:: Supported languages
7683 * Unsupported languages:: Unsupported languages
7687 @section Switching between source languages
7689 There are two ways to control the working language---either have @value{GDBN}
7690 set it automatically, or select it manually yourself. You can use the
7691 @code{set language} command for either purpose. On startup, @value{GDBN}
7692 defaults to setting the language automatically. The working language is
7693 used to determine how expressions you type are interpreted, how values
7696 In addition to the working language, every source file that
7697 @value{GDBN} knows about has its own working language. For some object
7698 file formats, the compiler might indicate which language a particular
7699 source file is in. However, most of the time @value{GDBN} infers the
7700 language from the name of the file. The language of a source file
7701 controls whether C@t{++} names are demangled---this way @code{backtrace} can
7702 show each frame appropriately for its own language. There is no way to
7703 set the language of a source file from within @value{GDBN}, but you can
7704 set the language associated with a filename extension. @xref{Show, ,
7705 Displaying the language}.
7707 This is most commonly a problem when you use a program, such
7708 as @code{cfront} or @code{f2c}, that generates C but is written in
7709 another language. In that case, make the
7710 program use @code{#line} directives in its C output; that way
7711 @value{GDBN} will know the correct language of the source code of the original
7712 program, and will display that source code, not the generated C code.
7715 * Filenames:: Filename extensions and languages.
7716 * Manually:: Setting the working language manually
7717 * Automatically:: Having @value{GDBN} infer the source language
7721 @subsection List of filename extensions and languages
7723 If a source file name ends in one of the following extensions, then
7724 @value{GDBN} infers that its language is the one indicated.
7745 Objective-C source file
7752 Modula-2 source file
7756 Assembler source file. This actually behaves almost like C, but
7757 @value{GDBN} does not skip over function prologues when stepping.
7760 In addition, you may set the language associated with a filename
7761 extension. @xref{Show, , Displaying the language}.
7764 @subsection Setting the working language
7766 If you allow @value{GDBN} to set the language automatically,
7767 expressions are interpreted the same way in your debugging session and
7770 @kindex set language
7771 If you wish, you may set the language manually. To do this, issue the
7772 command @samp{set language @var{lang}}, where @var{lang} is the name of
7774 @code{c} or @code{modula-2}.
7775 For a list of the supported languages, type @samp{set language}.
7777 Setting the language manually prevents @value{GDBN} from updating the working
7778 language automatically. This can lead to confusion if you try
7779 to debug a program when the working language is not the same as the
7780 source language, when an expression is acceptable to both
7781 languages---but means different things. For instance, if the current
7782 source file were written in C, and @value{GDBN} was parsing Modula-2, a
7790 might not have the effect you intended. In C, this means to add
7791 @code{b} and @code{c} and place the result in @code{a}. The result
7792 printed would be the value of @code{a}. In Modula-2, this means to compare
7793 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
7796 @subsection Having @value{GDBN} infer the source language
7798 To have @value{GDBN} set the working language automatically, use
7799 @samp{set language local} or @samp{set language auto}. @value{GDBN}
7800 then infers the working language. That is, when your program stops in a
7801 frame (usually by encountering a breakpoint), @value{GDBN} sets the
7802 working language to the language recorded for the function in that
7803 frame. If the language for a frame is unknown (that is, if the function
7804 or block corresponding to the frame was defined in a source file that
7805 does not have a recognized extension), the current working language is
7806 not changed, and @value{GDBN} issues a warning.
7808 This may not seem necessary for most programs, which are written
7809 entirely in one source language. However, program modules and libraries
7810 written in one source language can be used by a main program written in
7811 a different source language. Using @samp{set language auto} in this
7812 case frees you from having to set the working language manually.
7815 @section Displaying the language
7817 The following commands help you find out which language is the
7818 working language, and also what language source files were written in.
7820 @kindex show language
7823 Display the current working language. This is the
7824 language you can use with commands such as @code{print} to
7825 build and compute expressions that may involve variables in your program.
7828 @kindex info frame@r{, show the source language}
7829 Display the source language for this frame. This language becomes the
7830 working language if you use an identifier from this frame.
7831 @xref{Frame Info, ,Information about a frame}, to identify the other
7832 information listed here.
7835 @kindex info source@r{, show the source language}
7836 Display the source language of this source file.
7837 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
7838 information listed here.
7841 In unusual circumstances, you may have source files with extensions
7842 not in the standard list. You can then set the extension associated
7843 with a language explicitly:
7845 @kindex set extension-language
7846 @kindex info extensions
7848 @item set extension-language @var{.ext} @var{language}
7849 Set source files with extension @var{.ext} to be assumed to be in
7850 the source language @var{language}.
7852 @item info extensions
7853 List all the filename extensions and the associated languages.
7857 @section Type and range checking
7860 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
7861 checking are included, but they do not yet have any effect. This
7862 section documents the intended facilities.
7864 @c FIXME remove warning when type/range code added
7866 Some languages are designed to guard you against making seemingly common
7867 errors through a series of compile- and run-time checks. These include
7868 checking the type of arguments to functions and operators, and making
7869 sure mathematical overflows are caught at run time. Checks such as
7870 these help to ensure a program's correctness once it has been compiled
7871 by eliminating type mismatches, and providing active checks for range
7872 errors when your program is running.
7874 @value{GDBN} can check for conditions like the above if you wish.
7875 Although @value{GDBN} does not check the statements in your program, it
7876 can check expressions entered directly into @value{GDBN} for evaluation via
7877 the @code{print} command, for example. As with the working language,
7878 @value{GDBN} can also decide whether or not to check automatically based on
7879 your program's source language. @xref{Support, ,Supported languages},
7880 for the default settings of supported languages.
7883 * Type Checking:: An overview of type checking
7884 * Range Checking:: An overview of range checking
7887 @cindex type checking
7888 @cindex checks, type
7890 @subsection An overview of type checking
7892 Some languages, such as Modula-2, are strongly typed, meaning that the
7893 arguments to operators and functions have to be of the correct type,
7894 otherwise an error occurs. These checks prevent type mismatch
7895 errors from ever causing any run-time problems. For example,
7903 The second example fails because the @code{CARDINAL} 1 is not
7904 type-compatible with the @code{REAL} 2.3.
7906 For the expressions you use in @value{GDBN} commands, you can tell the
7907 @value{GDBN} type checker to skip checking;
7908 to treat any mismatches as errors and abandon the expression;
7909 or to only issue warnings when type mismatches occur,
7910 but evaluate the expression anyway. When you choose the last of
7911 these, @value{GDBN} evaluates expressions like the second example above, but
7912 also issues a warning.
7914 Even if you turn type checking off, there may be other reasons
7915 related to type that prevent @value{GDBN} from evaluating an expression.
7916 For instance, @value{GDBN} does not know how to add an @code{int} and
7917 a @code{struct foo}. These particular type errors have nothing to do
7918 with the language in use, and usually arise from expressions, such as
7919 the one described above, which make little sense to evaluate anyway.
7921 Each language defines to what degree it is strict about type. For
7922 instance, both Modula-2 and C require the arguments to arithmetical
7923 operators to be numbers. In C, enumerated types and pointers can be
7924 represented as numbers, so that they are valid arguments to mathematical
7925 operators. @xref{Support, ,Supported languages}, for further
7926 details on specific languages.
7928 @value{GDBN} provides some additional commands for controlling the type checker:
7930 @kindex set check type
7931 @kindex show check type
7933 @item set check type auto
7934 Set type checking on or off based on the current working language.
7935 @xref{Support, ,Supported languages}, for the default settings for
7938 @item set check type on
7939 @itemx set check type off
7940 Set type checking on or off, overriding the default setting for the
7941 current working language. Issue a warning if the setting does not
7942 match the language default. If any type mismatches occur in
7943 evaluating an expression while type checking is on, @value{GDBN} prints a
7944 message and aborts evaluation of the expression.
7946 @item set check type warn
7947 Cause the type checker to issue warnings, but to always attempt to
7948 evaluate the expression. Evaluating the expression may still
7949 be impossible for other reasons. For example, @value{GDBN} cannot add
7950 numbers and structures.
7953 Show the current setting of the type checker, and whether or not @value{GDBN}
7954 is setting it automatically.
7957 @cindex range checking
7958 @cindex checks, range
7959 @node Range Checking
7960 @subsection An overview of range checking
7962 In some languages (such as Modula-2), it is an error to exceed the
7963 bounds of a type; this is enforced with run-time checks. Such range
7964 checking is meant to ensure program correctness by making sure
7965 computations do not overflow, or indices on an array element access do
7966 not exceed the bounds of the array.
7968 For expressions you use in @value{GDBN} commands, you can tell
7969 @value{GDBN} to treat range errors in one of three ways: ignore them,
7970 always treat them as errors and abandon the expression, or issue
7971 warnings but evaluate the expression anyway.
7973 A range error can result from numerical overflow, from exceeding an
7974 array index bound, or when you type a constant that is not a member
7975 of any type. Some languages, however, do not treat overflows as an
7976 error. In many implementations of C, mathematical overflow causes the
7977 result to ``wrap around'' to lower values---for example, if @var{m} is
7978 the largest integer value, and @var{s} is the smallest, then
7981 @var{m} + 1 @result{} @var{s}
7984 This, too, is specific to individual languages, and in some cases
7985 specific to individual compilers or machines. @xref{Support, ,
7986 Supported languages}, for further details on specific languages.
7988 @value{GDBN} provides some additional commands for controlling the range checker:
7990 @kindex set check range
7991 @kindex show check range
7993 @item set check range auto
7994 Set range checking on or off based on the current working language.
7995 @xref{Support, ,Supported languages}, for the default settings for
7998 @item set check range on
7999 @itemx set check range off
8000 Set range checking on or off, overriding the default setting for the
8001 current working language. A warning is issued if the setting does not
8002 match the language default. If a range error occurs and range checking is on,
8003 then a message is printed and evaluation of the expression is aborted.
8005 @item set check range warn
8006 Output messages when the @value{GDBN} range checker detects a range error,
8007 but attempt to evaluate the expression anyway. Evaluating the
8008 expression may still be impossible for other reasons, such as accessing
8009 memory that the process does not own (a typical example from many Unix
8013 Show the current setting of the range checker, and whether or not it is
8014 being set automatically by @value{GDBN}.
8018 @section Supported languages
8020 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, assembly, Modula-2, and Ada.
8021 @c This is false ...
8022 Some @value{GDBN} features may be used in expressions regardless of the
8023 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
8024 and the @samp{@{type@}addr} construct (@pxref{Expressions,
8025 ,Expressions}) can be used with the constructs of any supported
8028 The following sections detail to what degree each source language is
8029 supported by @value{GDBN}. These sections are not meant to be language
8030 tutorials or references, but serve only as a reference guide to what the
8031 @value{GDBN} expression parser accepts, and what input and output
8032 formats should look like for different languages. There are many good
8033 books written on each of these languages; please look to these for a
8034 language reference or tutorial.
8038 * Objective-C:: Objective-C
8039 * Modula-2:: Modula-2
8044 @subsection C and C@t{++}
8046 @cindex C and C@t{++}
8047 @cindex expressions in C or C@t{++}
8049 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
8050 to both languages. Whenever this is the case, we discuss those languages
8054 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
8055 @cindex @sc{gnu} C@t{++}
8056 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
8057 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
8058 effectively, you must compile your C@t{++} programs with a supported
8059 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
8060 compiler (@code{aCC}).
8062 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
8063 format; if it doesn't work on your system, try the stabs+ debugging
8064 format. You can select those formats explicitly with the @code{g++}
8065 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
8066 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
8067 CC, gcc.info, Using @sc{gnu} CC}.
8070 * C Operators:: C and C@t{++} operators
8071 * C Constants:: C and C@t{++} constants
8072 * C plus plus expressions:: C@t{++} expressions
8073 * C Defaults:: Default settings for C and C@t{++}
8074 * C Checks:: C and C@t{++} type and range checks
8075 * Debugging C:: @value{GDBN} and C
8076 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
8080 @subsubsection C and C@t{++} operators
8082 @cindex C and C@t{++} operators
8084 Operators must be defined on values of specific types. For instance,
8085 @code{+} is defined on numbers, but not on structures. Operators are
8086 often defined on groups of types.
8088 For the purposes of C and C@t{++}, the following definitions hold:
8093 @emph{Integral types} include @code{int} with any of its storage-class
8094 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
8097 @emph{Floating-point types} include @code{float}, @code{double}, and
8098 @code{long double} (if supported by the target platform).
8101 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
8104 @emph{Scalar types} include all of the above.
8109 The following operators are supported. They are listed here
8110 in order of increasing precedence:
8114 The comma or sequencing operator. Expressions in a comma-separated list
8115 are evaluated from left to right, with the result of the entire
8116 expression being the last expression evaluated.
8119 Assignment. The value of an assignment expression is the value
8120 assigned. Defined on scalar types.
8123 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
8124 and translated to @w{@code{@var{a} = @var{a op b}}}.
8125 @w{@code{@var{op}=}} and @code{=} have the same precedence.
8126 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
8127 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
8130 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
8131 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
8135 Logical @sc{or}. Defined on integral types.
8138 Logical @sc{and}. Defined on integral types.
8141 Bitwise @sc{or}. Defined on integral types.
8144 Bitwise exclusive-@sc{or}. Defined on integral types.
8147 Bitwise @sc{and}. Defined on integral types.
8150 Equality and inequality. Defined on scalar types. The value of these
8151 expressions is 0 for false and non-zero for true.
8153 @item <@r{, }>@r{, }<=@r{, }>=
8154 Less than, greater than, less than or equal, greater than or equal.
8155 Defined on scalar types. The value of these expressions is 0 for false
8156 and non-zero for true.
8159 left shift, and right shift. Defined on integral types.
8162 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8165 Addition and subtraction. Defined on integral types, floating-point types and
8168 @item *@r{, }/@r{, }%
8169 Multiplication, division, and modulus. Multiplication and division are
8170 defined on integral and floating-point types. Modulus is defined on
8174 Increment and decrement. When appearing before a variable, the
8175 operation is performed before the variable is used in an expression;
8176 when appearing after it, the variable's value is used before the
8177 operation takes place.
8180 Pointer dereferencing. Defined on pointer types. Same precedence as
8184 Address operator. Defined on variables. Same precedence as @code{++}.
8186 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
8187 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
8188 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
8189 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
8193 Negative. Defined on integral and floating-point types. Same
8194 precedence as @code{++}.
8197 Logical negation. Defined on integral types. Same precedence as
8201 Bitwise complement operator. Defined on integral types. Same precedence as
8206 Structure member, and pointer-to-structure member. For convenience,
8207 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
8208 pointer based on the stored type information.
8209 Defined on @code{struct} and @code{union} data.
8212 Dereferences of pointers to members.
8215 Array indexing. @code{@var{a}[@var{i}]} is defined as
8216 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
8219 Function parameter list. Same precedence as @code{->}.
8222 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
8223 and @code{class} types.
8226 Doubled colons also represent the @value{GDBN} scope operator
8227 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
8231 If an operator is redefined in the user code, @value{GDBN} usually
8232 attempts to invoke the redefined version instead of using the operator's
8240 @subsubsection C and C@t{++} constants
8242 @cindex C and C@t{++} constants
8244 @value{GDBN} allows you to express the constants of C and C@t{++} in the
8249 Integer constants are a sequence of digits. Octal constants are
8250 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
8251 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
8252 @samp{l}, specifying that the constant should be treated as a
8256 Floating point constants are a sequence of digits, followed by a decimal
8257 point, followed by a sequence of digits, and optionally followed by an
8258 exponent. An exponent is of the form:
8259 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
8260 sequence of digits. The @samp{+} is optional for positive exponents.
8261 A floating-point constant may also end with a letter @samp{f} or
8262 @samp{F}, specifying that the constant should be treated as being of
8263 the @code{float} (as opposed to the default @code{double}) type; or with
8264 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
8268 Enumerated constants consist of enumerated identifiers, or their
8269 integral equivalents.
8272 Character constants are a single character surrounded by single quotes
8273 (@code{'}), or a number---the ordinal value of the corresponding character
8274 (usually its @sc{ascii} value). Within quotes, the single character may
8275 be represented by a letter or by @dfn{escape sequences}, which are of
8276 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
8277 of the character's ordinal value; or of the form @samp{\@var{x}}, where
8278 @samp{@var{x}} is a predefined special character---for example,
8279 @samp{\n} for newline.
8282 String constants are a sequence of character constants surrounded by
8283 double quotes (@code{"}). Any valid character constant (as described
8284 above) may appear. Double quotes within the string must be preceded by
8285 a backslash, so for instance @samp{"a\"b'c"} is a string of five
8289 Pointer constants are an integral value. You can also write pointers
8290 to constants using the C operator @samp{&}.
8293 Array constants are comma-separated lists surrounded by braces @samp{@{}
8294 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
8295 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
8296 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
8300 * C plus plus expressions::
8307 @node C plus plus expressions
8308 @subsubsection C@t{++} expressions
8310 @cindex expressions in C@t{++}
8311 @value{GDBN} expression handling can interpret most C@t{++} expressions.
8313 @cindex debugging C@t{++} programs
8314 @cindex C@t{++} compilers
8315 @cindex debug formats and C@t{++}
8316 @cindex @value{NGCC} and C@t{++}
8318 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
8319 proper compiler and the proper debug format. Currently, @value{GDBN}
8320 works best when debugging C@t{++} code that is compiled with
8321 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
8322 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
8323 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
8324 stabs+ as their default debug format, so you usually don't need to
8325 specify a debug format explicitly. Other compilers and/or debug formats
8326 are likely to work badly or not at all when using @value{GDBN} to debug
8332 @cindex member functions
8334 Member function calls are allowed; you can use expressions like
8337 count = aml->GetOriginal(x, y)
8340 @vindex this@r{, inside C@t{++} member functions}
8341 @cindex namespace in C@t{++}
8343 While a member function is active (in the selected stack frame), your
8344 expressions have the same namespace available as the member function;
8345 that is, @value{GDBN} allows implicit references to the class instance
8346 pointer @code{this} following the same rules as C@t{++}.
8348 @cindex call overloaded functions
8349 @cindex overloaded functions, calling
8350 @cindex type conversions in C@t{++}
8352 You can call overloaded functions; @value{GDBN} resolves the function
8353 call to the right definition, with some restrictions. @value{GDBN} does not
8354 perform overload resolution involving user-defined type conversions,
8355 calls to constructors, or instantiations of templates that do not exist
8356 in the program. It also cannot handle ellipsis argument lists or
8359 It does perform integral conversions and promotions, floating-point
8360 promotions, arithmetic conversions, pointer conversions, conversions of
8361 class objects to base classes, and standard conversions such as those of
8362 functions or arrays to pointers; it requires an exact match on the
8363 number of function arguments.
8365 Overload resolution is always performed, unless you have specified
8366 @code{set overload-resolution off}. @xref{Debugging C plus plus,
8367 ,@value{GDBN} features for C@t{++}}.
8369 You must specify @code{set overload-resolution off} in order to use an
8370 explicit function signature to call an overloaded function, as in
8372 p 'foo(char,int)'('x', 13)
8375 The @value{GDBN} command-completion facility can simplify this;
8376 see @ref{Completion, ,Command completion}.
8378 @cindex reference declarations
8380 @value{GDBN} understands variables declared as C@t{++} references; you can use
8381 them in expressions just as you do in C@t{++} source---they are automatically
8384 In the parameter list shown when @value{GDBN} displays a frame, the values of
8385 reference variables are not displayed (unlike other variables); this
8386 avoids clutter, since references are often used for large structures.
8387 The @emph{address} of a reference variable is always shown, unless
8388 you have specified @samp{set print address off}.
8391 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
8392 expressions can use it just as expressions in your program do. Since
8393 one scope may be defined in another, you can use @code{::} repeatedly if
8394 necessary, for example in an expression like
8395 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
8396 resolving name scope by reference to source files, in both C and C@t{++}
8397 debugging (@pxref{Variables, ,Program variables}).
8400 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
8401 calling virtual functions correctly, printing out virtual bases of
8402 objects, calling functions in a base subobject, casting objects, and
8403 invoking user-defined operators.
8406 @subsubsection C and C@t{++} defaults
8408 @cindex C and C@t{++} defaults
8410 If you allow @value{GDBN} to set type and range checking automatically, they
8411 both default to @code{off} whenever the working language changes to
8412 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
8413 selects the working language.
8415 If you allow @value{GDBN} to set the language automatically, it
8416 recognizes source files whose names end with @file{.c}, @file{.C}, or
8417 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
8418 these files, it sets the working language to C or C@t{++}.
8419 @xref{Automatically, ,Having @value{GDBN} infer the source language},
8420 for further details.
8422 @c Type checking is (a) primarily motivated by Modula-2, and (b)
8423 @c unimplemented. If (b) changes, it might make sense to let this node
8424 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
8427 @subsubsection C and C@t{++} type and range checks
8429 @cindex C and C@t{++} checks
8431 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
8432 is not used. However, if you turn type checking on, @value{GDBN}
8433 considers two variables type equivalent if:
8437 The two variables are structured and have the same structure, union, or
8441 The two variables have the same type name, or types that have been
8442 declared equivalent through @code{typedef}.
8445 @c leaving this out because neither J Gilmore nor R Pesch understand it.
8448 The two @code{struct}, @code{union}, or @code{enum} variables are
8449 declared in the same declaration. (Note: this may not be true for all C
8454 Range checking, if turned on, is done on mathematical operations. Array
8455 indices are not checked, since they are often used to index a pointer
8456 that is not itself an array.
8459 @subsubsection @value{GDBN} and C
8461 The @code{set print union} and @code{show print union} commands apply to
8462 the @code{union} type. When set to @samp{on}, any @code{union} that is
8463 inside a @code{struct} or @code{class} is also printed. Otherwise, it
8464 appears as @samp{@{...@}}.
8466 The @code{@@} operator aids in the debugging of dynamic arrays, formed
8467 with pointers and a memory allocation function. @xref{Expressions,
8471 * Debugging C plus plus::
8474 @node Debugging C plus plus
8475 @subsubsection @value{GDBN} features for C@t{++}
8477 @cindex commands for C@t{++}
8479 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
8480 designed specifically for use with C@t{++}. Here is a summary:
8483 @cindex break in overloaded functions
8484 @item @r{breakpoint menus}
8485 When you want a breakpoint in a function whose name is overloaded,
8486 @value{GDBN} breakpoint menus help you specify which function definition
8487 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
8489 @cindex overloading in C@t{++}
8490 @item rbreak @var{regex}
8491 Setting breakpoints using regular expressions is helpful for setting
8492 breakpoints on overloaded functions that are not members of any special
8494 @xref{Set Breaks, ,Setting breakpoints}.
8496 @cindex C@t{++} exception handling
8499 Debug C@t{++} exception handling using these commands. @xref{Set
8500 Catchpoints, , Setting catchpoints}.
8503 @item ptype @var{typename}
8504 Print inheritance relationships as well as other information for type
8506 @xref{Symbols, ,Examining the Symbol Table}.
8508 @cindex C@t{++} symbol display
8509 @item set print demangle
8510 @itemx show print demangle
8511 @itemx set print asm-demangle
8512 @itemx show print asm-demangle
8513 Control whether C@t{++} symbols display in their source form, both when
8514 displaying code as C@t{++} source and when displaying disassemblies.
8515 @xref{Print Settings, ,Print settings}.
8517 @item set print object
8518 @itemx show print object
8519 Choose whether to print derived (actual) or declared types of objects.
8520 @xref{Print Settings, ,Print settings}.
8522 @item set print vtbl
8523 @itemx show print vtbl
8524 Control the format for printing virtual function tables.
8525 @xref{Print Settings, ,Print settings}.
8526 (The @code{vtbl} commands do not work on programs compiled with the HP
8527 ANSI C@t{++} compiler (@code{aCC}).)
8529 @kindex set overload-resolution
8530 @cindex overloaded functions, overload resolution
8531 @item set overload-resolution on
8532 Enable overload resolution for C@t{++} expression evaluation. The default
8533 is on. For overloaded functions, @value{GDBN} evaluates the arguments
8534 and searches for a function whose signature matches the argument types,
8535 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
8536 expressions}, for details). If it cannot find a match, it emits a
8539 @item set overload-resolution off
8540 Disable overload resolution for C@t{++} expression evaluation. For
8541 overloaded functions that are not class member functions, @value{GDBN}
8542 chooses the first function of the specified name that it finds in the
8543 symbol table, whether or not its arguments are of the correct type. For
8544 overloaded functions that are class member functions, @value{GDBN}
8545 searches for a function whose signature @emph{exactly} matches the
8548 @item @r{Overloaded symbol names}
8549 You can specify a particular definition of an overloaded symbol, using
8550 the same notation that is used to declare such symbols in C@t{++}: type
8551 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
8552 also use the @value{GDBN} command-line word completion facilities to list the
8553 available choices, or to finish the type list for you.
8554 @xref{Completion,, Command completion}, for details on how to do this.
8558 @subsection Objective-C
8561 This section provides information about some commands and command
8562 options that are useful for debugging Objective-C code.
8565 * Method Names in Commands::
8566 * The Print Command with Objective-C::
8569 @node Method Names in Commands, The Print Command with Objective-C, Objective-C, Objective-C
8570 @subsubsection Method Names in Commands
8572 The following commands have been extended to accept Objective-C method
8573 names as line specifications:
8575 @kindex clear@r{, and Objective-C}
8576 @kindex break@r{, and Objective-C}
8577 @kindex info line@r{, and Objective-C}
8578 @kindex jump@r{, and Objective-C}
8579 @kindex list@r{, and Objective-C}
8583 @item @code{info line}
8588 A fully qualified Objective-C method name is specified as
8591 -[@var{Class} @var{methodName}]
8594 where the minus sign is used to indicate an instance method and a
8595 plus sign (not shown) is used to indicate a class method. The class
8596 name @var{Class} and method name @var{methodName} are enclosed in
8597 brackets, similar to the way messages are specified in Objective-C
8598 source code. For example, to set a breakpoint at the @code{create}
8599 instance method of class @code{Fruit} in the program currently being
8603 break -[Fruit create]
8606 To list ten program lines around the @code{initialize} class method,
8610 list +[NSText initialize]
8613 In the current version of @value{GDBN}, the plus or minus sign is
8614 required. In future versions of @value{GDBN}, the plus or minus
8615 sign will be optional, but you can use it to narrow the search. It
8616 is also possible to specify just a method name:
8622 You must specify the complete method name, including any colons. If
8623 your program's source files contain more than one @code{create} method,
8624 you'll be presented with a numbered list of classes that implement that
8625 method. Indicate your choice by number, or type @samp{0} to exit if
8628 As another example, to clear a breakpoint established at the
8629 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
8632 clear -[NSWindow makeKeyAndOrderFront:]
8635 @node The Print Command with Objective-C
8636 @subsubsection The Print Command With Objective-C
8637 @kindex print-object
8638 @kindex po @r{(@code{print-object})}
8640 The print command has also been extended to accept methods. For example:
8643 print -[@var{object} hash]
8646 @cindex print an Objective-C object description
8647 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
8649 will tell @value{GDBN} to send the @code{hash} message to @var{object}
8650 and print the result. Also, an additional command has been added,
8651 @code{print-object} or @code{po} for short, which is meant to print
8652 the description of an object. However, this command may only work
8653 with certain Objective-C libraries that have a particular hook
8654 function, @code{_NSPrintForDebugger}, defined.
8656 @node Modula-2, Ada, Objective-C, Support
8657 @subsection Modula-2
8659 @cindex Modula-2, @value{GDBN} support
8661 The extensions made to @value{GDBN} to support Modula-2 only support
8662 output from the @sc{gnu} Modula-2 compiler (which is currently being
8663 developed). Other Modula-2 compilers are not currently supported, and
8664 attempting to debug executables produced by them is most likely
8665 to give an error as @value{GDBN} reads in the executable's symbol
8668 @cindex expressions in Modula-2
8670 * M2 Operators:: Built-in operators
8671 * Built-In Func/Proc:: Built-in functions and procedures
8672 * M2 Constants:: Modula-2 constants
8673 * M2 Defaults:: Default settings for Modula-2
8674 * Deviations:: Deviations from standard Modula-2
8675 * M2 Checks:: Modula-2 type and range checks
8676 * M2 Scope:: The scope operators @code{::} and @code{.}
8677 * GDB/M2:: @value{GDBN} and Modula-2
8681 @subsubsection Operators
8682 @cindex Modula-2 operators
8684 Operators must be defined on values of specific types. For instance,
8685 @code{+} is defined on numbers, but not on structures. Operators are
8686 often defined on groups of types. For the purposes of Modula-2, the
8687 following definitions hold:
8692 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
8696 @emph{Character types} consist of @code{CHAR} and its subranges.
8699 @emph{Floating-point types} consist of @code{REAL}.
8702 @emph{Pointer types} consist of anything declared as @code{POINTER TO
8706 @emph{Scalar types} consist of all of the above.
8709 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
8712 @emph{Boolean types} consist of @code{BOOLEAN}.
8716 The following operators are supported, and appear in order of
8717 increasing precedence:
8721 Function argument or array index separator.
8724 Assignment. The value of @var{var} @code{:=} @var{value} is
8728 Less than, greater than on integral, floating-point, or enumerated
8732 Less than or equal to, greater than or equal to
8733 on integral, floating-point and enumerated types, or set inclusion on
8734 set types. Same precedence as @code{<}.
8736 @item =@r{, }<>@r{, }#
8737 Equality and two ways of expressing inequality, valid on scalar types.
8738 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
8739 available for inequality, since @code{#} conflicts with the script
8743 Set membership. Defined on set types and the types of their members.
8744 Same precedence as @code{<}.
8747 Boolean disjunction. Defined on boolean types.
8750 Boolean conjunction. Defined on boolean types.
8753 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8756 Addition and subtraction on integral and floating-point types, or union
8757 and difference on set types.
8760 Multiplication on integral and floating-point types, or set intersection
8764 Division on floating-point types, or symmetric set difference on set
8765 types. Same precedence as @code{*}.
8768 Integer division and remainder. Defined on integral types. Same
8769 precedence as @code{*}.
8772 Negative. Defined on @code{INTEGER} and @code{REAL} data.
8775 Pointer dereferencing. Defined on pointer types.
8778 Boolean negation. Defined on boolean types. Same precedence as
8782 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
8783 precedence as @code{^}.
8786 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
8789 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
8793 @value{GDBN} and Modula-2 scope operators.
8797 @emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
8798 treats the use of the operator @code{IN}, or the use of operators
8799 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
8800 @code{<=}, and @code{>=} on sets as an error.
8804 @node Built-In Func/Proc
8805 @subsubsection Built-in functions and procedures
8806 @cindex Modula-2 built-ins
8808 Modula-2 also makes available several built-in procedures and functions.
8809 In describing these, the following metavariables are used:
8814 represents an @code{ARRAY} variable.
8817 represents a @code{CHAR} constant or variable.
8820 represents a variable or constant of integral type.
8823 represents an identifier that belongs to a set. Generally used in the
8824 same function with the metavariable @var{s}. The type of @var{s} should
8825 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
8828 represents a variable or constant of integral or floating-point type.
8831 represents a variable or constant of floating-point type.
8837 represents a variable.
8840 represents a variable or constant of one of many types. See the
8841 explanation of the function for details.
8844 All Modula-2 built-in procedures also return a result, described below.
8848 Returns the absolute value of @var{n}.
8851 If @var{c} is a lower case letter, it returns its upper case
8852 equivalent, otherwise it returns its argument.
8855 Returns the character whose ordinal value is @var{i}.
8858 Decrements the value in the variable @var{v} by one. Returns the new value.
8860 @item DEC(@var{v},@var{i})
8861 Decrements the value in the variable @var{v} by @var{i}. Returns the
8864 @item EXCL(@var{m},@var{s})
8865 Removes the element @var{m} from the set @var{s}. Returns the new
8868 @item FLOAT(@var{i})
8869 Returns the floating point equivalent of the integer @var{i}.
8872 Returns the index of the last member of @var{a}.
8875 Increments the value in the variable @var{v} by one. Returns the new value.
8877 @item INC(@var{v},@var{i})
8878 Increments the value in the variable @var{v} by @var{i}. Returns the
8881 @item INCL(@var{m},@var{s})
8882 Adds the element @var{m} to the set @var{s} if it is not already
8883 there. Returns the new set.
8886 Returns the maximum value of the type @var{t}.
8889 Returns the minimum value of the type @var{t}.
8892 Returns boolean TRUE if @var{i} is an odd number.
8895 Returns the ordinal value of its argument. For example, the ordinal
8896 value of a character is its @sc{ascii} value (on machines supporting the
8897 @sc{ascii} character set). @var{x} must be of an ordered type, which include
8898 integral, character and enumerated types.
8901 Returns the size of its argument. @var{x} can be a variable or a type.
8903 @item TRUNC(@var{r})
8904 Returns the integral part of @var{r}.
8906 @item VAL(@var{t},@var{i})
8907 Returns the member of the type @var{t} whose ordinal value is @var{i}.
8911 @emph{Warning:} Sets and their operations are not yet supported, so
8912 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
8916 @cindex Modula-2 constants
8918 @subsubsection Constants
8920 @value{GDBN} allows you to express the constants of Modula-2 in the following
8926 Integer constants are simply a sequence of digits. When used in an
8927 expression, a constant is interpreted to be type-compatible with the
8928 rest of the expression. Hexadecimal integers are specified by a
8929 trailing @samp{H}, and octal integers by a trailing @samp{B}.
8932 Floating point constants appear as a sequence of digits, followed by a
8933 decimal point and another sequence of digits. An optional exponent can
8934 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
8935 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
8936 digits of the floating point constant must be valid decimal (base 10)
8940 Character constants consist of a single character enclosed by a pair of
8941 like quotes, either single (@code{'}) or double (@code{"}). They may
8942 also be expressed by their ordinal value (their @sc{ascii} value, usually)
8943 followed by a @samp{C}.
8946 String constants consist of a sequence of characters enclosed by a
8947 pair of like quotes, either single (@code{'}) or double (@code{"}).
8948 Escape sequences in the style of C are also allowed. @xref{C
8949 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
8953 Enumerated constants consist of an enumerated identifier.
8956 Boolean constants consist of the identifiers @code{TRUE} and
8960 Pointer constants consist of integral values only.
8963 Set constants are not yet supported.
8967 @subsubsection Modula-2 defaults
8968 @cindex Modula-2 defaults
8970 If type and range checking are set automatically by @value{GDBN}, they
8971 both default to @code{on} whenever the working language changes to
8972 Modula-2. This happens regardless of whether you or @value{GDBN}
8973 selected the working language.
8975 If you allow @value{GDBN} to set the language automatically, then entering
8976 code compiled from a file whose name ends with @file{.mod} sets the
8977 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
8978 the language automatically}, for further details.
8981 @subsubsection Deviations from standard Modula-2
8982 @cindex Modula-2, deviations from
8984 A few changes have been made to make Modula-2 programs easier to debug.
8985 This is done primarily via loosening its type strictness:
8989 Unlike in standard Modula-2, pointer constants can be formed by
8990 integers. This allows you to modify pointer variables during
8991 debugging. (In standard Modula-2, the actual address contained in a
8992 pointer variable is hidden from you; it can only be modified
8993 through direct assignment to another pointer variable or expression that
8994 returned a pointer.)
8997 C escape sequences can be used in strings and characters to represent
8998 non-printable characters. @value{GDBN} prints out strings with these
8999 escape sequences embedded. Single non-printable characters are
9000 printed using the @samp{CHR(@var{nnn})} format.
9003 The assignment operator (@code{:=}) returns the value of its right-hand
9007 All built-in procedures both modify @emph{and} return their argument.
9011 @subsubsection Modula-2 type and range checks
9012 @cindex Modula-2 checks
9015 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
9018 @c FIXME remove warning when type/range checks added
9020 @value{GDBN} considers two Modula-2 variables type equivalent if:
9024 They are of types that have been declared equivalent via a @code{TYPE
9025 @var{t1} = @var{t2}} statement
9028 They have been declared on the same line. (Note: This is true of the
9029 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
9032 As long as type checking is enabled, any attempt to combine variables
9033 whose types are not equivalent is an error.
9035 Range checking is done on all mathematical operations, assignment, array
9036 index bounds, and all built-in functions and procedures.
9039 @subsubsection The scope operators @code{::} and @code{.}
9041 @cindex @code{.}, Modula-2 scope operator
9042 @cindex colon, doubled as scope operator
9044 @vindex colon-colon@r{, in Modula-2}
9045 @c Info cannot handle :: but TeX can.
9048 @vindex ::@r{, in Modula-2}
9051 There are a few subtle differences between the Modula-2 scope operator
9052 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
9057 @var{module} . @var{id}
9058 @var{scope} :: @var{id}
9062 where @var{scope} is the name of a module or a procedure,
9063 @var{module} the name of a module, and @var{id} is any declared
9064 identifier within your program, except another module.
9066 Using the @code{::} operator makes @value{GDBN} search the scope
9067 specified by @var{scope} for the identifier @var{id}. If it is not
9068 found in the specified scope, then @value{GDBN} searches all scopes
9069 enclosing the one specified by @var{scope}.
9071 Using the @code{.} operator makes @value{GDBN} search the current scope for
9072 the identifier specified by @var{id} that was imported from the
9073 definition module specified by @var{module}. With this operator, it is
9074 an error if the identifier @var{id} was not imported from definition
9075 module @var{module}, or if @var{id} is not an identifier in
9079 @subsubsection @value{GDBN} and Modula-2
9081 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
9082 Five subcommands of @code{set print} and @code{show print} apply
9083 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
9084 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
9085 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
9086 analogue in Modula-2.
9088 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
9089 with any language, is not useful with Modula-2. Its
9090 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
9091 created in Modula-2 as they can in C or C@t{++}. However, because an
9092 address can be specified by an integral constant, the construct
9093 @samp{@{@var{type}@}@var{adrexp}} is still useful.
9095 @cindex @code{#} in Modula-2
9096 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
9097 interpreted as the beginning of a comment. Use @code{<>} instead.
9103 The extensions made to @value{GDBN} for Ada only support
9104 output from the @sc{gnu} Ada (GNAT) compiler.
9105 Other Ada compilers are not currently supported, and
9106 attempting to debug executables produced by them is most likely
9110 @cindex expressions in Ada
9112 * Ada Mode Intro:: General remarks on the Ada syntax
9113 and semantics supported by Ada mode
9115 * Omissions from Ada:: Restrictions on the Ada expression syntax.
9116 * Additions to Ada:: Extensions of the Ada expression syntax.
9117 * Stopping Before Main Program:: Debugging the program during elaboration.
9118 * Ada Glitches:: Known peculiarities of Ada mode.
9121 @node Ada Mode Intro
9122 @subsubsection Introduction
9123 @cindex Ada mode, general
9125 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
9126 syntax, with some extensions.
9127 The philosophy behind the design of this subset is
9131 That @value{GDBN} should provide basic literals and access to operations for
9132 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
9133 leaving more sophisticated computations to subprograms written into the
9134 program (which therefore may be called from @value{GDBN}).
9137 That type safety and strict adherence to Ada language restrictions
9138 are not particularly important to the @value{GDBN} user.
9141 That brevity is important to the @value{GDBN} user.
9144 Thus, for brevity, the debugger acts as if there were
9145 implicit @code{with} and @code{use} clauses in effect for all user-written
9146 packages, making it unnecessary to fully qualify most names with
9147 their packages, regardless of context. Where this causes ambiguity,
9148 @value{GDBN} asks the user's intent.
9150 The debugger will start in Ada mode if it detects an Ada main program.
9151 As for other languages, it will enter Ada mode when stopped in a program that
9152 was translated from an Ada source file.
9154 While in Ada mode, you may use `@t{--}' for comments. This is useful
9155 mostly for documenting command files. The standard @value{GDBN} comment
9156 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
9157 middle (to allow based literals).
9159 The debugger supports limited overloading. Given a subprogram call in which
9160 the function symbol has multiple definitions, it will use the number of
9161 actual parameters and some information about their types to attempt to narrow
9162 the set of definitions. It also makes very limited use of context, preferring
9163 procedures to functions in the context of the @code{call} command, and
9164 functions to procedures elsewhere.
9166 @node Omissions from Ada
9167 @subsubsection Omissions from Ada
9168 @cindex Ada, omissions from
9170 Here are the notable omissions from the subset:
9174 Only a subset of the attributes are supported:
9178 @t{'First}, @t{'Last}, and @t{'Length}
9179 on array objects (not on types and subtypes).
9182 @t{'Min} and @t{'Max}.
9185 @t{'Pos} and @t{'Val}.
9191 @t{'Range} on array objects (not subtypes), but only as the right
9192 operand of the membership (@code{in}) operator.
9195 @t{'Access}, @t{'Unchecked_Access}, and
9196 @t{'Unrestricted_Access} (a GNAT extension).
9204 @code{Characters.Latin_1} are not available and
9205 concatenation is not implemented. Thus, escape characters in strings are
9206 not currently available.
9209 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
9210 equality of representations. They will generally work correctly
9211 for strings and arrays whose elements have integer or enumeration types.
9212 They may not work correctly for arrays whose element
9213 types have user-defined equality, for arrays of real values
9214 (in particular, IEEE-conformant floating point, because of negative
9215 zeroes and NaNs), and for arrays whose elements contain unused bits with
9216 indeterminate values.
9219 The other component-by-component array operations (@code{and}, @code{or},
9220 @code{xor}, @code{not}, and relational tests other than equality)
9221 are not implemented.
9224 There are no record or array aggregates.
9227 Calls to dispatching subprograms are not implemented.
9230 The overloading algorithm is much more limited (i.e., less selective)
9231 than that of real Ada. It makes only limited use of the context in which a subexpression
9232 appears to resolve its meaning, and it is much looser in its rules for allowing
9233 type matches. As a result, some function calls will be ambiguous, and the user
9234 will be asked to choose the proper resolution.
9237 The @code{new} operator is not implemented.
9240 Entry calls are not implemented.
9243 Aside from printing, arithmetic operations on the native VAX floating-point
9244 formats are not supported.
9247 It is not possible to slice a packed array.
9250 @node Additions to Ada
9251 @subsubsection Additions to Ada
9252 @cindex Ada, deviations from
9254 As it does for other languages, @value{GDBN} makes certain generic
9255 extensions to Ada (@pxref{Expressions}):
9259 If the expression @var{E} is a variable residing in memory
9260 (typically a local variable or array element) and @var{N} is
9261 a positive integer, then @code{@var{E}@@@var{N}} displays the values of
9262 @var{E} and the @var{N}-1 adjacent variables following it in memory as an array.
9263 In Ada, this operator is generally not necessary, since its prime use
9264 is in displaying parts of an array, and slicing will usually do this in Ada.
9265 However, there are occasional uses when debugging programs
9266 in which certain debugging information has been optimized away.
9269 @code{@var{B}::@var{var}} means ``the variable named @var{var} that appears
9270 in function or file @var{B}.'' When @var{B} is a file name, you must typically
9271 surround it in single quotes.
9274 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
9275 @var{type} that appears at address @var{addr}.''
9278 A name starting with @samp{$} is a convenience variable
9279 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
9282 In addition, @value{GDBN} provides a few other shortcuts and outright additions specific
9287 The assignment statement is allowed as an expression, returning
9288 its right-hand operand as its value. Thus, you may enter
9292 print A(tmp := y + 1)
9296 The semicolon is allowed as an ``operator,'' returning as its value
9297 the value of its right-hand operand.
9298 This allows, for example,
9299 complex conditional breaks:
9303 condition 1 (report(i); k += 1; A(k) > 100)
9307 Rather than use catenation and symbolic character names to introduce special
9308 characters into strings, one may instead use a special bracket notation,
9309 which is also used to print strings. A sequence of characters of the form
9310 @samp{["@var{XX}"]} within a string or character literal denotes the
9311 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
9312 sequence of characters @samp{["""]} also denotes a single quotation mark
9313 in strings. For example,
9315 "One line.["0a"]Next line.["0a"]"
9318 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF}) after each
9322 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
9323 @t{'Max} is optional (and is ignored in any case). For example, it is valid
9331 When printing arrays, @value{GDBN} uses positional notation when the
9332 array has a lower bound of 1, and uses a modified named notation otherwise.
9333 For example, a one-dimensional array of three integers with a lower bound of 3 might print as
9340 That is, in contrast to valid Ada, only the first component has a @code{=>}
9344 You may abbreviate attributes in expressions with any unique,
9345 multi-character subsequence of
9346 their names (an exact match gets preference).
9347 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
9348 in place of @t{a'length}.
9351 @cindex quoting Ada internal identifiers
9352 Since Ada is case-insensitive, the debugger normally maps identifiers you type
9353 to lower case. The GNAT compiler uses upper-case characters for
9354 some of its internal identifiers, which are normally of no interest to users.
9355 For the rare occasions when you actually have to look at them,
9356 enclose them in angle brackets to avoid the lower-case mapping.
9359 @value{GDBP} print <JMPBUF_SAVE>[0]
9363 Printing an object of class-wide type or dereferencing an
9364 access-to-class-wide value will display all the components of the object's
9365 specific type (as indicated by its run-time tag). Likewise, component
9366 selection on such a value will operate on the specific type of the
9371 @node Stopping Before Main Program
9372 @subsubsection Stopping at the Very Beginning
9374 @cindex breakpointing Ada elaboration code
9375 It is sometimes necessary to debug the program during elaboration, and
9376 before reaching the main procedure.
9377 As defined in the Ada Reference
9378 Manual, the elaboration code is invoked from a procedure called
9379 @code{adainit}. To run your program up to the beginning of
9380 elaboration, simply use the following two commands:
9381 @code{tbreak adainit} and @code{run}.
9384 @subsubsection Known Peculiarities of Ada Mode
9385 @cindex Ada, problems
9387 Besides the omissions listed previously (@pxref{Omissions from Ada}),
9388 we know of several problems with and limitations of Ada mode in
9390 some of which will be fixed with planned future releases of the debugger
9391 and the GNU Ada compiler.
9395 Currently, the debugger
9396 has insufficient information to determine whether certain pointers represent
9397 pointers to objects or the objects themselves.
9398 Thus, the user may have to tack an extra @code{.all} after an expression
9399 to get it printed properly.
9402 Static constants that the compiler chooses not to materialize as objects in
9403 storage are invisible to the debugger.
9406 Named parameter associations in function argument lists are ignored (the
9407 argument lists are treated as positional).
9410 Many useful library packages are currently invisible to the debugger.
9413 Fixed-point arithmetic, conversions, input, and output is carried out using
9414 floating-point arithmetic, and may give results that only approximate those on
9418 The type of the @t{'Address} attribute may not be @code{System.Address}.
9421 The GNAT compiler never generates the prefix @code{Standard} for any of
9422 the standard symbols defined by the Ada language. @value{GDBN} knows about
9423 this: it will strip the prefix from names when you use it, and will never
9424 look for a name you have so qualified among local symbols, nor match against
9425 symbols in other packages or subprograms. If you have
9426 defined entities anywhere in your program other than parameters and
9427 local variables whose simple names match names in @code{Standard},
9428 GNAT's lack of qualification here can cause confusion. When this happens,
9429 you can usually resolve the confusion
9430 by qualifying the problematic names with package
9431 @code{Standard} explicitly.
9434 @node Unsupported languages
9435 @section Unsupported languages
9437 @cindex unsupported languages
9438 @cindex minimal language
9439 In addition to the other fully-supported programming languages,
9440 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
9441 It does not represent a real programming language, but provides a set
9442 of capabilities close to what the C or assembly languages provide.
9443 This should allow most simple operations to be performed while debugging
9444 an application that uses a language currently not supported by @value{GDBN}.
9446 If the language is set to @code{auto}, @value{GDBN} will automatically
9447 select this language if the current frame corresponds to an unsupported
9451 @chapter Examining the Symbol Table
9453 The commands described in this chapter allow you to inquire about the
9454 symbols (names of variables, functions and types) defined in your
9455 program. This information is inherent in the text of your program and
9456 does not change as your program executes. @value{GDBN} finds it in your
9457 program's symbol table, in the file indicated when you started @value{GDBN}
9458 (@pxref{File Options, ,Choosing files}), or by one of the
9459 file-management commands (@pxref{Files, ,Commands to specify files}).
9461 @cindex symbol names
9462 @cindex names of symbols
9463 @cindex quoting names
9464 Occasionally, you may need to refer to symbols that contain unusual
9465 characters, which @value{GDBN} ordinarily treats as word delimiters. The
9466 most frequent case is in referring to static variables in other
9467 source files (@pxref{Variables,,Program variables}). File names
9468 are recorded in object files as debugging symbols, but @value{GDBN} would
9469 ordinarily parse a typical file name, like @file{foo.c}, as the three words
9470 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
9471 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
9478 looks up the value of @code{x} in the scope of the file @file{foo.c}.
9481 @kindex info address
9482 @cindex address of a symbol
9483 @item info address @var{symbol}
9484 Describe where the data for @var{symbol} is stored. For a register
9485 variable, this says which register it is kept in. For a non-register
9486 local variable, this prints the stack-frame offset at which the variable
9489 Note the contrast with @samp{print &@var{symbol}}, which does not work
9490 at all for a register variable, and for a stack local variable prints
9491 the exact address of the current instantiation of the variable.
9494 @cindex symbol from address
9495 @item info symbol @var{addr}
9496 Print the name of a symbol which is stored at the address @var{addr}.
9497 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
9498 nearest symbol and an offset from it:
9501 (@value{GDBP}) info symbol 0x54320
9502 _initialize_vx + 396 in section .text
9506 This is the opposite of the @code{info address} command. You can use
9507 it to find out the name of a variable or a function given its address.
9510 @item whatis @var{expr}
9511 Print the data type of expression @var{expr}. @var{expr} is not
9512 actually evaluated, and any side-effecting operations (such as
9513 assignments or function calls) inside it do not take place.
9514 @xref{Expressions, ,Expressions}.
9517 Print the data type of @code{$}, the last value in the value history.
9520 @item ptype @var{typename}
9521 Print a description of data type @var{typename}. @var{typename} may be
9522 the name of a type, or for C code it may have the form @samp{class
9523 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
9524 @var{union-tag}} or @samp{enum @var{enum-tag}}.
9526 @item ptype @var{expr}
9528 Print a description of the type of expression @var{expr}. @code{ptype}
9529 differs from @code{whatis} by printing a detailed description, instead
9530 of just the name of the type.
9532 For example, for this variable declaration:
9535 struct complex @{double real; double imag;@} v;
9539 the two commands give this output:
9543 (@value{GDBP}) whatis v
9544 type = struct complex
9545 (@value{GDBP}) ptype v
9546 type = struct complex @{
9554 As with @code{whatis}, using @code{ptype} without an argument refers to
9555 the type of @code{$}, the last value in the value history.
9558 @item info types @var{regexp}
9560 Print a brief description of all types whose names match @var{regexp}
9561 (or all types in your program, if you supply no argument). Each
9562 complete typename is matched as though it were a complete line; thus,
9563 @samp{i type value} gives information on all types in your program whose
9564 names include the string @code{value}, but @samp{i type ^value$} gives
9565 information only on types whose complete name is @code{value}.
9567 This command differs from @code{ptype} in two ways: first, like
9568 @code{whatis}, it does not print a detailed description; second, it
9569 lists all source files where a type is defined.
9572 @cindex local variables
9573 @item info scope @var{addr}
9574 List all the variables local to a particular scope. This command
9575 accepts a location---a function name, a source line, or an address
9576 preceded by a @samp{*}, and prints all the variables local to the
9577 scope defined by that location. For example:
9580 (@value{GDBP}) @b{info scope command_line_handler}
9581 Scope for command_line_handler:
9582 Symbol rl is an argument at stack/frame offset 8, length 4.
9583 Symbol linebuffer is in static storage at address 0x150a18, length 4.
9584 Symbol linelength is in static storage at address 0x150a1c, length 4.
9585 Symbol p is a local variable in register $esi, length 4.
9586 Symbol p1 is a local variable in register $ebx, length 4.
9587 Symbol nline is a local variable in register $edx, length 4.
9588 Symbol repeat is a local variable at frame offset -8, length 4.
9592 This command is especially useful for determining what data to collect
9593 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
9598 Show information about the current source file---that is, the source file for
9599 the function containing the current point of execution:
9602 the name of the source file, and the directory containing it,
9604 the directory it was compiled in,
9606 its length, in lines,
9608 which programming language it is written in,
9610 whether the executable includes debugging information for that file, and
9611 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
9613 whether the debugging information includes information about
9614 preprocessor macros.
9618 @kindex info sources
9620 Print the names of all source files in your program for which there is
9621 debugging information, organized into two lists: files whose symbols
9622 have already been read, and files whose symbols will be read when needed.
9624 @kindex info functions
9625 @item info functions
9626 Print the names and data types of all defined functions.
9628 @item info functions @var{regexp}
9629 Print the names and data types of all defined functions
9630 whose names contain a match for regular expression @var{regexp}.
9631 Thus, @samp{info fun step} finds all functions whose names
9632 include @code{step}; @samp{info fun ^step} finds those whose names
9633 start with @code{step}. If a function name contains characters
9634 that conflict with the regular expression language (eg.
9635 @samp{operator*()}), they may be quoted with a backslash.
9637 @kindex info variables
9638 @item info variables
9639 Print the names and data types of all variables that are declared
9640 outside of functions (i.e.@: excluding local variables).
9642 @item info variables @var{regexp}
9643 Print the names and data types of all variables (except for local
9644 variables) whose names contain a match for regular expression
9647 @kindex info classes
9649 @itemx info classes @var{regexp}
9650 Display all Objective-C classes in your program, or
9651 (with the @var{regexp} argument) all those matching a particular regular
9654 @kindex info selectors
9655 @item info selectors
9656 @itemx info selectors @var{regexp}
9657 Display all Objective-C selectors in your program, or
9658 (with the @var{regexp} argument) all those matching a particular regular
9662 This was never implemented.
9663 @kindex info methods
9665 @itemx info methods @var{regexp}
9666 The @code{info methods} command permits the user to examine all defined
9667 methods within C@t{++} program, or (with the @var{regexp} argument) a
9668 specific set of methods found in the various C@t{++} classes. Many
9669 C@t{++} classes provide a large number of methods. Thus, the output
9670 from the @code{ptype} command can be overwhelming and hard to use. The
9671 @code{info-methods} command filters the methods, printing only those
9672 which match the regular-expression @var{regexp}.
9675 @cindex reloading symbols
9676 Some systems allow individual object files that make up your program to
9677 be replaced without stopping and restarting your program. For example,
9678 in VxWorks you can simply recompile a defective object file and keep on
9679 running. If you are running on one of these systems, you can allow
9680 @value{GDBN} to reload the symbols for automatically relinked modules:
9683 @kindex set symbol-reloading
9684 @item set symbol-reloading on
9685 Replace symbol definitions for the corresponding source file when an
9686 object file with a particular name is seen again.
9688 @item set symbol-reloading off
9689 Do not replace symbol definitions when encountering object files of the
9690 same name more than once. This is the default state; if you are not
9691 running on a system that permits automatic relinking of modules, you
9692 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
9693 may discard symbols when linking large programs, that may contain
9694 several modules (from different directories or libraries) with the same
9697 @kindex show symbol-reloading
9698 @item show symbol-reloading
9699 Show the current @code{on} or @code{off} setting.
9702 @kindex set opaque-type-resolution
9703 @item set opaque-type-resolution on
9704 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
9705 declared as a pointer to a @code{struct}, @code{class}, or
9706 @code{union}---for example, @code{struct MyType *}---that is used in one
9707 source file although the full declaration of @code{struct MyType} is in
9708 another source file. The default is on.
9710 A change in the setting of this subcommand will not take effect until
9711 the next time symbols for a file are loaded.
9713 @item set opaque-type-resolution off
9714 Tell @value{GDBN} not to resolve opaque types. In this case, the type
9715 is printed as follows:
9717 @{<no data fields>@}
9720 @kindex show opaque-type-resolution
9721 @item show opaque-type-resolution
9722 Show whether opaque types are resolved or not.
9724 @kindex maint print symbols
9726 @kindex maint print psymbols
9727 @cindex partial symbol dump
9728 @item maint print symbols @var{filename}
9729 @itemx maint print psymbols @var{filename}
9730 @itemx maint print msymbols @var{filename}
9731 Write a dump of debugging symbol data into the file @var{filename}.
9732 These commands are used to debug the @value{GDBN} symbol-reading code. Only
9733 symbols with debugging data are included. If you use @samp{maint print
9734 symbols}, @value{GDBN} includes all the symbols for which it has already
9735 collected full details: that is, @var{filename} reflects symbols for
9736 only those files whose symbols @value{GDBN} has read. You can use the
9737 command @code{info sources} to find out which files these are. If you
9738 use @samp{maint print psymbols} instead, the dump shows information about
9739 symbols that @value{GDBN} only knows partially---that is, symbols defined in
9740 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
9741 @samp{maint print msymbols} dumps just the minimal symbol information
9742 required for each object file from which @value{GDBN} has read some symbols.
9743 @xref{Files, ,Commands to specify files}, for a discussion of how
9744 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
9746 @kindex maint info symtabs
9747 @kindex maint info psymtabs
9748 @cindex listing @value{GDBN}'s internal symbol tables
9749 @cindex symbol tables, listing @value{GDBN}'s internal
9750 @cindex full symbol tables, listing @value{GDBN}'s internal
9751 @cindex partial symbol tables, listing @value{GDBN}'s internal
9752 @item maint info symtabs @r{[} @var{regexp} @r{]}
9753 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
9755 List the @code{struct symtab} or @code{struct partial_symtab}
9756 structures whose names match @var{regexp}. If @var{regexp} is not
9757 given, list them all. The output includes expressions which you can
9758 copy into a @value{GDBN} debugging this one to examine a particular
9759 structure in more detail. For example:
9762 (@value{GDBP}) maint info psymtabs dwarf2read
9763 @{ objfile /home/gnu/build/gdb/gdb
9764 ((struct objfile *) 0x82e69d0)
9765 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
9766 ((struct partial_symtab *) 0x8474b10)
9769 text addresses 0x814d3c8 -- 0x8158074
9770 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
9771 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
9775 (@value{GDBP}) maint info symtabs
9779 We see that there is one partial symbol table whose filename contains
9780 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
9781 and we see that @value{GDBN} has not read in any symtabs yet at all.
9782 If we set a breakpoint on a function, that will cause @value{GDBN} to
9783 read the symtab for the compilation unit containing that function:
9786 (@value{GDBP}) break dwarf2_psymtab_to_symtab
9787 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
9789 (@value{GDBP}) maint info symtabs
9790 @{ objfile /home/gnu/build/gdb/gdb
9791 ((struct objfile *) 0x82e69d0)
9792 @{ symtab /home/gnu/src/gdb/dwarf2read.c
9793 ((struct symtab *) 0x86c1f38)
9796 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
9806 @chapter Altering Execution
9808 Once you think you have found an error in your program, you might want to
9809 find out for certain whether correcting the apparent error would lead to
9810 correct results in the rest of the run. You can find the answer by
9811 experiment, using the @value{GDBN} features for altering execution of the
9814 For example, you can store new values into variables or memory
9815 locations, give your program a signal, restart it at a different
9816 address, or even return prematurely from a function.
9819 * Assignment:: Assignment to variables
9820 * Jumping:: Continuing at a different address
9821 * Signaling:: Giving your program a signal
9822 * Returning:: Returning from a function
9823 * Calling:: Calling your program's functions
9824 * Patching:: Patching your program
9828 @section Assignment to variables
9831 @cindex setting variables
9832 To alter the value of a variable, evaluate an assignment expression.
9833 @xref{Expressions, ,Expressions}. For example,
9840 stores the value 4 into the variable @code{x}, and then prints the
9841 value of the assignment expression (which is 4).
9842 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
9843 information on operators in supported languages.
9845 @kindex set variable
9846 @cindex variables, setting
9847 If you are not interested in seeing the value of the assignment, use the
9848 @code{set} command instead of the @code{print} command. @code{set} is
9849 really the same as @code{print} except that the expression's value is
9850 not printed and is not put in the value history (@pxref{Value History,
9851 ,Value history}). The expression is evaluated only for its effects.
9853 If the beginning of the argument string of the @code{set} command
9854 appears identical to a @code{set} subcommand, use the @code{set
9855 variable} command instead of just @code{set}. This command is identical
9856 to @code{set} except for its lack of subcommands. For example, if your
9857 program has a variable @code{width}, you get an error if you try to set
9858 a new value with just @samp{set width=13}, because @value{GDBN} has the
9859 command @code{set width}:
9862 (@value{GDBP}) whatis width
9864 (@value{GDBP}) p width
9866 (@value{GDBP}) set width=47
9867 Invalid syntax in expression.
9871 The invalid expression, of course, is @samp{=47}. In
9872 order to actually set the program's variable @code{width}, use
9875 (@value{GDBP}) set var width=47
9878 Because the @code{set} command has many subcommands that can conflict
9879 with the names of program variables, it is a good idea to use the
9880 @code{set variable} command instead of just @code{set}. For example, if
9881 your program has a variable @code{g}, you run into problems if you try
9882 to set a new value with just @samp{set g=4}, because @value{GDBN} has
9883 the command @code{set gnutarget}, abbreviated @code{set g}:
9887 (@value{GDBP}) whatis g
9891 (@value{GDBP}) set g=4
9895 The program being debugged has been started already.
9896 Start it from the beginning? (y or n) y
9897 Starting program: /home/smith/cc_progs/a.out
9898 "/home/smith/cc_progs/a.out": can't open to read symbols:
9900 (@value{GDBP}) show g
9901 The current BFD target is "=4".
9906 The program variable @code{g} did not change, and you silently set the
9907 @code{gnutarget} to an invalid value. In order to set the variable
9911 (@value{GDBP}) set var g=4
9914 @value{GDBN} allows more implicit conversions in assignments than C; you can
9915 freely store an integer value into a pointer variable or vice versa,
9916 and you can convert any structure to any other structure that is the
9917 same length or shorter.
9918 @comment FIXME: how do structs align/pad in these conversions?
9919 @comment /doc@cygnus.com 18dec1990
9921 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
9922 construct to generate a value of specified type at a specified address
9923 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
9924 to memory location @code{0x83040} as an integer (which implies a certain size
9925 and representation in memory), and
9928 set @{int@}0x83040 = 4
9932 stores the value 4 into that memory location.
9935 @section Continuing at a different address
9937 Ordinarily, when you continue your program, you do so at the place where
9938 it stopped, with the @code{continue} command. You can instead continue at
9939 an address of your own choosing, with the following commands:
9943 @item jump @var{linespec}
9944 Resume execution at line @var{linespec}. Execution stops again
9945 immediately if there is a breakpoint there. @xref{List, ,Printing
9946 source lines}, for a description of the different forms of
9947 @var{linespec}. It is common practice to use the @code{tbreak} command
9948 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
9951 The @code{jump} command does not change the current stack frame, or
9952 the stack pointer, or the contents of any memory location or any
9953 register other than the program counter. If line @var{linespec} is in
9954 a different function from the one currently executing, the results may
9955 be bizarre if the two functions expect different patterns of arguments or
9956 of local variables. For this reason, the @code{jump} command requests
9957 confirmation if the specified line is not in the function currently
9958 executing. However, even bizarre results are predictable if you are
9959 well acquainted with the machine-language code of your program.
9961 @item jump *@var{address}
9962 Resume execution at the instruction at address @var{address}.
9965 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
9966 On many systems, you can get much the same effect as the @code{jump}
9967 command by storing a new value into the register @code{$pc}. The
9968 difference is that this does not start your program running; it only
9969 changes the address of where it @emph{will} run when you continue. For
9977 makes the next @code{continue} command or stepping command execute at
9978 address @code{0x485}, rather than at the address where your program stopped.
9979 @xref{Continuing and Stepping, ,Continuing and stepping}.
9981 The most common occasion to use the @code{jump} command is to back
9982 up---perhaps with more breakpoints set---over a portion of a program
9983 that has already executed, in order to examine its execution in more
9988 @section Giving your program a signal
9992 @item signal @var{signal}
9993 Resume execution where your program stopped, but immediately give it the
9994 signal @var{signal}. @var{signal} can be the name or the number of a
9995 signal. For example, on many systems @code{signal 2} and @code{signal
9996 SIGINT} are both ways of sending an interrupt signal.
9998 Alternatively, if @var{signal} is zero, continue execution without
9999 giving a signal. This is useful when your program stopped on account of
10000 a signal and would ordinary see the signal when resumed with the
10001 @code{continue} command; @samp{signal 0} causes it to resume without a
10004 @code{signal} does not repeat when you press @key{RET} a second time
10005 after executing the command.
10009 Invoking the @code{signal} command is not the same as invoking the
10010 @code{kill} utility from the shell. Sending a signal with @code{kill}
10011 causes @value{GDBN} to decide what to do with the signal depending on
10012 the signal handling tables (@pxref{Signals}). The @code{signal} command
10013 passes the signal directly to your program.
10017 @section Returning from a function
10020 @cindex returning from a function
10023 @itemx return @var{expression}
10024 You can cancel execution of a function call with the @code{return}
10025 command. If you give an
10026 @var{expression} argument, its value is used as the function's return
10030 When you use @code{return}, @value{GDBN} discards the selected stack frame
10031 (and all frames within it). You can think of this as making the
10032 discarded frame return prematurely. If you wish to specify a value to
10033 be returned, give that value as the argument to @code{return}.
10035 This pops the selected stack frame (@pxref{Selection, ,Selecting a
10036 frame}), and any other frames inside of it, leaving its caller as the
10037 innermost remaining frame. That frame becomes selected. The
10038 specified value is stored in the registers used for returning values
10041 The @code{return} command does not resume execution; it leaves the
10042 program stopped in the state that would exist if the function had just
10043 returned. In contrast, the @code{finish} command (@pxref{Continuing
10044 and Stepping, ,Continuing and stepping}) resumes execution until the
10045 selected stack frame returns naturally.
10048 @section Calling program functions
10050 @cindex calling functions
10053 @item call @var{expr}
10054 Evaluate the expression @var{expr} without displaying @code{void}
10058 You can use this variant of the @code{print} command if you want to
10059 execute a function from your program, but without cluttering the output
10060 with @code{void} returned values. If the result is not void, it
10061 is printed and saved in the value history.
10064 @section Patching programs
10066 @cindex patching binaries
10067 @cindex writing into executables
10068 @cindex writing into corefiles
10070 By default, @value{GDBN} opens the file containing your program's
10071 executable code (or the corefile) read-only. This prevents accidental
10072 alterations to machine code; but it also prevents you from intentionally
10073 patching your program's binary.
10075 If you'd like to be able to patch the binary, you can specify that
10076 explicitly with the @code{set write} command. For example, you might
10077 want to turn on internal debugging flags, or even to make emergency
10083 @itemx set write off
10084 If you specify @samp{set write on}, @value{GDBN} opens executable and
10085 core files for both reading and writing; if you specify @samp{set write
10086 off} (the default), @value{GDBN} opens them read-only.
10088 If you have already loaded a file, you must load it again (using the
10089 @code{exec-file} or @code{core-file} command) after changing @code{set
10090 write}, for your new setting to take effect.
10094 Display whether executable files and core files are opened for writing
10095 as well as reading.
10099 @chapter @value{GDBN} Files
10101 @value{GDBN} needs to know the file name of the program to be debugged,
10102 both in order to read its symbol table and in order to start your
10103 program. To debug a core dump of a previous run, you must also tell
10104 @value{GDBN} the name of the core dump file.
10107 * Files:: Commands to specify files
10108 * Separate Debug Files:: Debugging information in separate files
10109 * Symbol Errors:: Errors reading symbol files
10113 @section Commands to specify files
10115 @cindex symbol table
10116 @cindex core dump file
10118 You may want to specify executable and core dump file names. The usual
10119 way to do this is at start-up time, using the arguments to
10120 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
10121 Out of @value{GDBN}}).
10123 Occasionally it is necessary to change to a different file during a
10124 @value{GDBN} session. Or you may run @value{GDBN} and forget to specify
10125 a file you want to use. In these situations the @value{GDBN} commands
10126 to specify new files are useful.
10129 @cindex executable file
10131 @item file @var{filename}
10132 Use @var{filename} as the program to be debugged. It is read for its
10133 symbols and for the contents of pure memory. It is also the program
10134 executed when you use the @code{run} command. If you do not specify a
10135 directory and the file is not found in the @value{GDBN} working directory,
10136 @value{GDBN} uses the environment variable @code{PATH} as a list of
10137 directories to search, just as the shell does when looking for a program
10138 to run. You can change the value of this variable, for both @value{GDBN}
10139 and your program, using the @code{path} command.
10141 On systems with memory-mapped files, an auxiliary file named
10142 @file{@var{filename}.syms} may hold symbol table information for
10143 @var{filename}. If so, @value{GDBN} maps in the symbol table from
10144 @file{@var{filename}.syms}, starting up more quickly. See the
10145 descriptions of the file options @samp{-mapped} and @samp{-readnow}
10146 (available on the command line, and with the commands @code{file},
10147 @code{symbol-file}, or @code{add-symbol-file}, described below),
10148 for more information.
10151 @code{file} with no argument makes @value{GDBN} discard any information it
10152 has on both executable file and the symbol table.
10155 @item exec-file @r{[} @var{filename} @r{]}
10156 Specify that the program to be run (but not the symbol table) is found
10157 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
10158 if necessary to locate your program. Omitting @var{filename} means to
10159 discard information on the executable file.
10161 @kindex symbol-file
10162 @item symbol-file @r{[} @var{filename} @r{]}
10163 Read symbol table information from file @var{filename}. @code{PATH} is
10164 searched when necessary. Use the @code{file} command to get both symbol
10165 table and program to run from the same file.
10167 @code{symbol-file} with no argument clears out @value{GDBN} information on your
10168 program's symbol table.
10170 The @code{symbol-file} command causes @value{GDBN} to forget the contents
10171 of its convenience variables, the value history, and all breakpoints and
10172 auto-display expressions. This is because they may contain pointers to
10173 the internal data recording symbols and data types, which are part of
10174 the old symbol table data being discarded inside @value{GDBN}.
10176 @code{symbol-file} does not repeat if you press @key{RET} again after
10179 When @value{GDBN} is configured for a particular environment, it
10180 understands debugging information in whatever format is the standard
10181 generated for that environment; you may use either a @sc{gnu} compiler, or
10182 other compilers that adhere to the local conventions.
10183 Best results are usually obtained from @sc{gnu} compilers; for example,
10184 using @code{@value{GCC}} you can generate debugging information for
10187 For most kinds of object files, with the exception of old SVR3 systems
10188 using COFF, the @code{symbol-file} command does not normally read the
10189 symbol table in full right away. Instead, it scans the symbol table
10190 quickly to find which source files and which symbols are present. The
10191 details are read later, one source file at a time, as they are needed.
10193 The purpose of this two-stage reading strategy is to make @value{GDBN}
10194 start up faster. For the most part, it is invisible except for
10195 occasional pauses while the symbol table details for a particular source
10196 file are being read. (The @code{set verbose} command can turn these
10197 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
10198 warnings and messages}.)
10200 We have not implemented the two-stage strategy for COFF yet. When the
10201 symbol table is stored in COFF format, @code{symbol-file} reads the
10202 symbol table data in full right away. Note that ``stabs-in-COFF''
10203 still does the two-stage strategy, since the debug info is actually
10207 @cindex reading symbols immediately
10208 @cindex symbols, reading immediately
10210 @cindex memory-mapped symbol file
10211 @cindex saving symbol table
10212 @item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10213 @itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10214 You can override the @value{GDBN} two-stage strategy for reading symbol
10215 tables by using the @samp{-readnow} option with any of the commands that
10216 load symbol table information, if you want to be sure @value{GDBN} has the
10217 entire symbol table available.
10219 If memory-mapped files are available on your system through the
10220 @code{mmap} system call, you can use another option, @samp{-mapped}, to
10221 cause @value{GDBN} to write the symbols for your program into a reusable
10222 file. Future @value{GDBN} debugging sessions map in symbol information
10223 from this auxiliary symbol file (if the program has not changed), rather
10224 than spending time reading the symbol table from the executable
10225 program. Using the @samp{-mapped} option has the same effect as
10226 starting @value{GDBN} with the @samp{-mapped} command-line option.
10228 You can use both options together, to make sure the auxiliary symbol
10229 file has all the symbol information for your program.
10231 The auxiliary symbol file for a program called @var{myprog} is called
10232 @samp{@var{myprog}.syms}. Once this file exists (so long as it is newer
10233 than the corresponding executable), @value{GDBN} always attempts to use
10234 it when you debug @var{myprog}; no special options or commands are
10237 The @file{.syms} file is specific to the host machine where you run
10238 @value{GDBN}. It holds an exact image of the internal @value{GDBN}
10239 symbol table. It cannot be shared across multiple host platforms.
10241 @c FIXME: for now no mention of directories, since this seems to be in
10242 @c flux. 13mar1992 status is that in theory GDB would look either in
10243 @c current dir or in same dir as myprog; but issues like competing
10244 @c GDB's, or clutter in system dirs, mean that in practice right now
10245 @c only current dir is used. FFish says maybe a special GDB hierarchy
10246 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
10250 @item core-file @r{[} @var{filename} @r{]}
10252 Specify the whereabouts of a core dump file to be used as the ``contents
10253 of memory''. Traditionally, core files contain only some parts of the
10254 address space of the process that generated them; @value{GDBN} can access the
10255 executable file itself for other parts.
10257 @code{core-file} with no argument specifies that no core file is
10260 Note that the core file is ignored when your program is actually running
10261 under @value{GDBN}. So, if you have been running your program and you
10262 wish to debug a core file instead, you must kill the subprocess in which
10263 the program is running. To do this, use the @code{kill} command
10264 (@pxref{Kill Process, ,Killing the child process}).
10266 @kindex add-symbol-file
10267 @cindex dynamic linking
10268 @item add-symbol-file @var{filename} @var{address}
10269 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10270 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
10271 The @code{add-symbol-file} command reads additional symbol table
10272 information from the file @var{filename}. You would use this command
10273 when @var{filename} has been dynamically loaded (by some other means)
10274 into the program that is running. @var{address} should be the memory
10275 address at which the file has been loaded; @value{GDBN} cannot figure
10276 this out for itself. You can additionally specify an arbitrary number
10277 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
10278 section name and base address for that section. You can specify any
10279 @var{address} as an expression.
10281 The symbol table of the file @var{filename} is added to the symbol table
10282 originally read with the @code{symbol-file} command. You can use the
10283 @code{add-symbol-file} command any number of times; the new symbol data
10284 thus read keeps adding to the old. To discard all old symbol data
10285 instead, use the @code{symbol-file} command without any arguments.
10287 @cindex relocatable object files, reading symbols from
10288 @cindex object files, relocatable, reading symbols from
10289 @cindex reading symbols from relocatable object files
10290 @cindex symbols, reading from relocatable object files
10291 @cindex @file{.o} files, reading symbols from
10292 Although @var{filename} is typically a shared library file, an
10293 executable file, or some other object file which has been fully
10294 relocated for loading into a process, you can also load symbolic
10295 information from relocatable @file{.o} files, as long as:
10299 the file's symbolic information refers only to linker symbols defined in
10300 that file, not to symbols defined by other object files,
10302 every section the file's symbolic information refers to has actually
10303 been loaded into the inferior, as it appears in the file, and
10305 you can determine the address at which every section was loaded, and
10306 provide these to the @code{add-symbol-file} command.
10310 Some embedded operating systems, like Sun Chorus and VxWorks, can load
10311 relocatable files into an already running program; such systems
10312 typically make the requirements above easy to meet. However, it's
10313 important to recognize that many native systems use complex link
10314 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
10315 assembly, for example) that make the requirements difficult to meet. In
10316 general, one cannot assume that using @code{add-symbol-file} to read a
10317 relocatable object file's symbolic information will have the same effect
10318 as linking the relocatable object file into the program in the normal
10321 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
10323 You can use the @samp{-mapped} and @samp{-readnow} options just as with
10324 the @code{symbol-file} command, to change how @value{GDBN} manages the symbol
10325 table information for @var{filename}.
10327 @kindex add-shared-symbol-file
10328 @item add-shared-symbol-file
10329 The @code{add-shared-symbol-file} command can be used only under Harris' CXUX
10330 operating system for the Motorola 88k. @value{GDBN} automatically looks for
10331 shared libraries, however if @value{GDBN} does not find yours, you can run
10332 @code{add-shared-symbol-file}. It takes no arguments.
10336 The @code{section} command changes the base address of section SECTION of
10337 the exec file to ADDR. This can be used if the exec file does not contain
10338 section addresses, (such as in the a.out format), or when the addresses
10339 specified in the file itself are wrong. Each section must be changed
10340 separately. The @code{info files} command, described below, lists all
10341 the sections and their addresses.
10344 @kindex info target
10347 @code{info files} and @code{info target} are synonymous; both print the
10348 current target (@pxref{Targets, ,Specifying a Debugging Target}),
10349 including the names of the executable and core dump files currently in
10350 use by @value{GDBN}, and the files from which symbols were loaded. The
10351 command @code{help target} lists all possible targets rather than
10354 @kindex maint info sections
10355 @item maint info sections
10356 Another command that can give you extra information about program sections
10357 is @code{maint info sections}. In addition to the section information
10358 displayed by @code{info files}, this command displays the flags and file
10359 offset of each section in the executable and core dump files. In addition,
10360 @code{maint info sections} provides the following command options (which
10361 may be arbitrarily combined):
10365 Display sections for all loaded object files, including shared libraries.
10366 @item @var{sections}
10367 Display info only for named @var{sections}.
10368 @item @var{section-flags}
10369 Display info only for sections for which @var{section-flags} are true.
10370 The section flags that @value{GDBN} currently knows about are:
10373 Section will have space allocated in the process when loaded.
10374 Set for all sections except those containing debug information.
10376 Section will be loaded from the file into the child process memory.
10377 Set for pre-initialized code and data, clear for @code{.bss} sections.
10379 Section needs to be relocated before loading.
10381 Section cannot be modified by the child process.
10383 Section contains executable code only.
10385 Section contains data only (no executable code).
10387 Section will reside in ROM.
10389 Section contains data for constructor/destructor lists.
10391 Section is not empty.
10393 An instruction to the linker to not output the section.
10394 @item COFF_SHARED_LIBRARY
10395 A notification to the linker that the section contains
10396 COFF shared library information.
10398 Section contains common symbols.
10401 @kindex set trust-readonly-sections
10402 @item set trust-readonly-sections on
10403 Tell @value{GDBN} that readonly sections in your object file
10404 really are read-only (i.e.@: that their contents will not change).
10405 In that case, @value{GDBN} can fetch values from these sections
10406 out of the object file, rather than from the target program.
10407 For some targets (notably embedded ones), this can be a significant
10408 enhancement to debugging performance.
10410 The default is off.
10412 @item set trust-readonly-sections off
10413 Tell @value{GDBN} not to trust readonly sections. This means that
10414 the contents of the section might change while the program is running,
10415 and must therefore be fetched from the target when needed.
10418 All file-specifying commands allow both absolute and relative file names
10419 as arguments. @value{GDBN} always converts the file name to an absolute file
10420 name and remembers it that way.
10422 @cindex shared libraries
10423 @value{GDBN} supports HP-UX, SunOS, SVr4, Irix 5, and IBM RS/6000 shared
10426 @value{GDBN} automatically loads symbol definitions from shared libraries
10427 when you use the @code{run} command, or when you examine a core file.
10428 (Before you issue the @code{run} command, @value{GDBN} does not understand
10429 references to a function in a shared library, however---unless you are
10430 debugging a core file).
10432 On HP-UX, if the program loads a library explicitly, @value{GDBN}
10433 automatically loads the symbols at the time of the @code{shl_load} call.
10435 @c FIXME: some @value{GDBN} release may permit some refs to undef
10436 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
10437 @c FIXME...lib; check this from time to time when updating manual
10439 There are times, however, when you may wish to not automatically load
10440 symbol definitions from shared libraries, such as when they are
10441 particularly large or there are many of them.
10443 To control the automatic loading of shared library symbols, use the
10447 @kindex set auto-solib-add
10448 @item set auto-solib-add @var{mode}
10449 If @var{mode} is @code{on}, symbols from all shared object libraries
10450 will be loaded automatically when the inferior begins execution, you
10451 attach to an independently started inferior, or when the dynamic linker
10452 informs @value{GDBN} that a new library has been loaded. If @var{mode}
10453 is @code{off}, symbols must be loaded manually, using the
10454 @code{sharedlibrary} command. The default value is @code{on}.
10456 @cindex memory used for symbol tables
10457 If your program uses lots of shared libraries with debug info that
10458 takes large amounts of memory, you can decrease the @value{GDBN}
10459 memory footprint by preventing it from automatically loading the
10460 symbols from shared libraries. To that end, type @kbd{set
10461 auto-solib-add off} before running the inferior, then load each
10462 library whose debug symbols you do need with @kbd{sharedlibrary
10463 @var{regexp}}, where @var{regexp} is a regular expresion that matches
10464 the libraries whose symbols you want to be loaded.
10466 @kindex show auto-solib-add
10467 @item show auto-solib-add
10468 Display the current autoloading mode.
10471 To explicitly load shared library symbols, use the @code{sharedlibrary}
10475 @kindex info sharedlibrary
10478 @itemx info sharedlibrary
10479 Print the names of the shared libraries which are currently loaded.
10481 @kindex sharedlibrary
10483 @item sharedlibrary @var{regex}
10484 @itemx share @var{regex}
10485 Load shared object library symbols for files matching a
10486 Unix regular expression.
10487 As with files loaded automatically, it only loads shared libraries
10488 required by your program for a core file or after typing @code{run}. If
10489 @var{regex} is omitted all shared libraries required by your program are
10493 On some systems, such as HP-UX systems, @value{GDBN} supports
10494 autoloading shared library symbols until a limiting threshold size is
10495 reached. This provides the benefit of allowing autoloading to remain on
10496 by default, but avoids autoloading excessively large shared libraries,
10497 up to a threshold that is initially set, but which you can modify if you
10500 Beyond that threshold, symbols from shared libraries must be explicitly
10501 loaded. To load these symbols, use the command @code{sharedlibrary
10502 @var{filename}}. The base address of the shared library is determined
10503 automatically by @value{GDBN} and need not be specified.
10505 To display or set the threshold, use the commands:
10508 @kindex set auto-solib-limit
10509 @item set auto-solib-limit @var{threshold}
10510 Set the autoloading size threshold, in an integral number of megabytes.
10511 If @var{threshold} is nonzero and shared library autoloading is enabled,
10512 symbols from all shared object libraries will be loaded until the total
10513 size of the loaded shared library symbols exceeds this threshold.
10514 Otherwise, symbols must be loaded manually, using the
10515 @code{sharedlibrary} command. The default threshold is 100 (i.e.@: 100
10518 @kindex show auto-solib-limit
10519 @item show auto-solib-limit
10520 Display the current autoloading size threshold, in megabytes.
10523 Shared libraries are also supported in many cross or remote debugging
10524 configurations. A copy of the target's libraries need to be present on the
10525 host system; they need to be the same as the target libraries, although the
10526 copies on the target can be stripped as long as the copies on the host are
10529 You need to tell @value{GDBN} where the target libraries are, so that it can
10530 load the correct copies---otherwise, it may try to load the host's libraries.
10531 @value{GDBN} has two variables to specify the search directories for target
10535 @kindex set solib-absolute-prefix
10536 @item set solib-absolute-prefix @var{path}
10537 If this variable is set, @var{path} will be used as a prefix for any
10538 absolute shared library paths; many runtime loaders store the absolute
10539 paths to the shared library in the target program's memory. If you use
10540 @samp{solib-absolute-prefix} to find shared libraries, they need to be laid
10541 out in the same way that they are on the target, with e.g.@: a
10542 @file{/usr/lib} hierarchy under @var{path}.
10544 You can set the default value of @samp{solib-absolute-prefix} by using the
10545 configure-time @samp{--with-sysroot} option.
10547 @kindex show solib-absolute-prefix
10548 @item show solib-absolute-prefix
10549 Display the current shared library prefix.
10551 @kindex set solib-search-path
10552 @item set solib-search-path @var{path}
10553 If this variable is set, @var{path} is a colon-separated list of directories
10554 to search for shared libraries. @samp{solib-search-path} is used after
10555 @samp{solib-absolute-prefix} fails to locate the library, or if the path to
10556 the library is relative instead of absolute. If you want to use
10557 @samp{solib-search-path} instead of @samp{solib-absolute-prefix}, be sure to
10558 set @samp{solib-absolute-prefix} to a nonexistant directory to prevent
10559 @value{GDBN} from finding your host's libraries.
10561 @kindex show solib-search-path
10562 @item show solib-search-path
10563 Display the current shared library search path.
10567 @node Separate Debug Files
10568 @section Debugging Information in Separate Files
10569 @cindex separate debugging information files
10570 @cindex debugging information in separate files
10571 @cindex @file{.debug} subdirectories
10572 @cindex debugging information directory, global
10573 @cindex global debugging information directory
10575 @value{GDBN} allows you to put a program's debugging information in a
10576 file separate from the executable itself, in a way that allows
10577 @value{GDBN} to find and load the debugging information automatically.
10578 Since debugging information can be very large --- sometimes larger
10579 than the executable code itself --- some systems distribute debugging
10580 information for their executables in separate files, which users can
10581 install only when they need to debug a problem.
10583 If an executable's debugging information has been extracted to a
10584 separate file, the executable should contain a @dfn{debug link} giving
10585 the name of the debugging information file (with no directory
10586 components), and a checksum of its contents. (The exact form of a
10587 debug link is described below.) If the full name of the directory
10588 containing the executable is @var{execdir}, and the executable has a
10589 debug link that specifies the name @var{debugfile}, then @value{GDBN}
10590 will automatically search for the debugging information file in three
10595 the directory containing the executable file (that is, it will look
10596 for a file named @file{@var{execdir}/@var{debugfile}},
10598 a subdirectory of that directory named @file{.debug} (that is, the
10599 file @file{@var{execdir}/.debug/@var{debugfile}}, and
10601 a subdirectory of the global debug file directory that includes the
10602 executable's full path, and the name from the link (that is, the file
10603 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
10604 @var{globaldebugdir} is the global debug file directory, and
10605 @var{execdir} has been turned into a relative path).
10608 @value{GDBN} checks under each of these names for a debugging
10609 information file whose checksum matches that given in the link, and
10610 reads the debugging information from the first one it finds.
10612 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
10613 which has a link containing the name @file{ls.debug}, and the global
10614 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
10615 for debug information in @file{/usr/bin/ls.debug},
10616 @file{/usr/bin/.debug/ls.debug}, and
10617 @file{/usr/lib/debug/usr/bin/ls.debug}.
10619 You can set the global debugging info directory's name, and view the
10620 name @value{GDBN} is currently using.
10624 @kindex set debug-file-directory
10625 @item set debug-file-directory @var{directory}
10626 Set the directory which @value{GDBN} searches for separate debugging
10627 information files to @var{directory}.
10629 @kindex show debug-file-directory
10630 @item show debug-file-directory
10631 Show the directory @value{GDBN} searches for separate debugging
10636 @cindex @code{.gnu_debuglink} sections
10637 @cindex debug links
10638 A debug link is a special section of the executable file named
10639 @code{.gnu_debuglink}. The section must contain:
10643 A filename, with any leading directory components removed, followed by
10646 zero to three bytes of padding, as needed to reach the next four-byte
10647 boundary within the section, and
10649 a four-byte CRC checksum, stored in the same endianness used for the
10650 executable file itself. The checksum is computed on the debugging
10651 information file's full contents by the function given below, passing
10652 zero as the @var{crc} argument.
10655 Any executable file format can carry a debug link, as long as it can
10656 contain a section named @code{.gnu_debuglink} with the contents
10659 The debugging information file itself should be an ordinary
10660 executable, containing a full set of linker symbols, sections, and
10661 debugging information. The sections of the debugging information file
10662 should have the same names, addresses and sizes as the original file,
10663 but they need not contain any data --- much like a @code{.bss} section
10664 in an ordinary executable.
10666 As of December 2002, there is no standard GNU utility to produce
10667 separated executable / debugging information file pairs. Ulrich
10668 Drepper's @file{elfutils} package, starting with version 0.53,
10669 contains a version of the @code{strip} command such that the command
10670 @kbd{strip foo -f foo.debug} removes the debugging information from
10671 the executable file @file{foo}, places it in the file
10672 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
10674 Since there are many different ways to compute CRC's (different
10675 polynomials, reversals, byte ordering, etc.), the simplest way to
10676 describe the CRC used in @code{.gnu_debuglink} sections is to give the
10677 complete code for a function that computes it:
10679 @kindex gnu_debuglink_crc32
10682 gnu_debuglink_crc32 (unsigned long crc,
10683 unsigned char *buf, size_t len)
10685 static const unsigned long crc32_table[256] =
10687 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
10688 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
10689 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
10690 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
10691 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
10692 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
10693 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
10694 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
10695 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
10696 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
10697 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
10698 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
10699 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
10700 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
10701 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
10702 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
10703 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
10704 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
10705 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
10706 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
10707 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
10708 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
10709 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
10710 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
10711 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
10712 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
10713 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
10714 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
10715 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
10716 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
10717 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
10718 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
10719 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
10720 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
10721 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
10722 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
10723 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
10724 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
10725 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
10726 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
10727 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
10728 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
10729 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
10730 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
10731 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
10732 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
10733 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
10734 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
10735 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
10736 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
10737 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
10740 unsigned char *end;
10742 crc = ~crc & 0xffffffff;
10743 for (end = buf + len; buf < end; ++buf)
10744 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
10745 return ~crc & 0xffffffff;
10750 @node Symbol Errors
10751 @section Errors reading symbol files
10753 While reading a symbol file, @value{GDBN} occasionally encounters problems,
10754 such as symbol types it does not recognize, or known bugs in compiler
10755 output. By default, @value{GDBN} does not notify you of such problems, since
10756 they are relatively common and primarily of interest to people
10757 debugging compilers. If you are interested in seeing information
10758 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
10759 only one message about each such type of problem, no matter how many
10760 times the problem occurs; or you can ask @value{GDBN} to print more messages,
10761 to see how many times the problems occur, with the @code{set
10762 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
10765 The messages currently printed, and their meanings, include:
10768 @item inner block not inside outer block in @var{symbol}
10770 The symbol information shows where symbol scopes begin and end
10771 (such as at the start of a function or a block of statements). This
10772 error indicates that an inner scope block is not fully contained
10773 in its outer scope blocks.
10775 @value{GDBN} circumvents the problem by treating the inner block as if it had
10776 the same scope as the outer block. In the error message, @var{symbol}
10777 may be shown as ``@code{(don't know)}'' if the outer block is not a
10780 @item block at @var{address} out of order
10782 The symbol information for symbol scope blocks should occur in
10783 order of increasing addresses. This error indicates that it does not
10786 @value{GDBN} does not circumvent this problem, and has trouble
10787 locating symbols in the source file whose symbols it is reading. (You
10788 can often determine what source file is affected by specifying
10789 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
10792 @item bad block start address patched
10794 The symbol information for a symbol scope block has a start address
10795 smaller than the address of the preceding source line. This is known
10796 to occur in the SunOS 4.1.1 (and earlier) C compiler.
10798 @value{GDBN} circumvents the problem by treating the symbol scope block as
10799 starting on the previous source line.
10801 @item bad string table offset in symbol @var{n}
10804 Symbol number @var{n} contains a pointer into the string table which is
10805 larger than the size of the string table.
10807 @value{GDBN} circumvents the problem by considering the symbol to have the
10808 name @code{foo}, which may cause other problems if many symbols end up
10811 @item unknown symbol type @code{0x@var{nn}}
10813 The symbol information contains new data types that @value{GDBN} does
10814 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
10815 uncomprehended information, in hexadecimal.
10817 @value{GDBN} circumvents the error by ignoring this symbol information.
10818 This usually allows you to debug your program, though certain symbols
10819 are not accessible. If you encounter such a problem and feel like
10820 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
10821 on @code{complain}, then go up to the function @code{read_dbx_symtab}
10822 and examine @code{*bufp} to see the symbol.
10824 @item stub type has NULL name
10826 @value{GDBN} could not find the full definition for a struct or class.
10828 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
10829 The symbol information for a C@t{++} member function is missing some
10830 information that recent versions of the compiler should have output for
10833 @item info mismatch between compiler and debugger
10835 @value{GDBN} could not parse a type specification output by the compiler.
10840 @chapter Specifying a Debugging Target
10842 @cindex debugging target
10845 A @dfn{target} is the execution environment occupied by your program.
10847 Often, @value{GDBN} runs in the same host environment as your program;
10848 in that case, the debugging target is specified as a side effect when
10849 you use the @code{file} or @code{core} commands. When you need more
10850 flexibility---for example, running @value{GDBN} on a physically separate
10851 host, or controlling a standalone system over a serial port or a
10852 realtime system over a TCP/IP connection---you can use the @code{target}
10853 command to specify one of the target types configured for @value{GDBN}
10854 (@pxref{Target Commands, ,Commands for managing targets}).
10857 * Active Targets:: Active targets
10858 * Target Commands:: Commands for managing targets
10859 * Byte Order:: Choosing target byte order
10860 * Remote:: Remote debugging
10861 * KOD:: Kernel Object Display
10865 @node Active Targets
10866 @section Active targets
10868 @cindex stacking targets
10869 @cindex active targets
10870 @cindex multiple targets
10872 There are three classes of targets: processes, core files, and
10873 executable files. @value{GDBN} can work concurrently on up to three
10874 active targets, one in each class. This allows you to (for example)
10875 start a process and inspect its activity without abandoning your work on
10878 For example, if you execute @samp{gdb a.out}, then the executable file
10879 @code{a.out} is the only active target. If you designate a core file as
10880 well---presumably from a prior run that crashed and coredumped---then
10881 @value{GDBN} has two active targets and uses them in tandem, looking
10882 first in the corefile target, then in the executable file, to satisfy
10883 requests for memory addresses. (Typically, these two classes of target
10884 are complementary, since core files contain only a program's
10885 read-write memory---variables and so on---plus machine status, while
10886 executable files contain only the program text and initialized data.)
10888 When you type @code{run}, your executable file becomes an active process
10889 target as well. When a process target is active, all @value{GDBN}
10890 commands requesting memory addresses refer to that target; addresses in
10891 an active core file or executable file target are obscured while the
10892 process target is active.
10894 Use the @code{core-file} and @code{exec-file} commands to select a new
10895 core file or executable target (@pxref{Files, ,Commands to specify
10896 files}). To specify as a target a process that is already running, use
10897 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
10900 @node Target Commands
10901 @section Commands for managing targets
10904 @item target @var{type} @var{parameters}
10905 Connects the @value{GDBN} host environment to a target machine or
10906 process. A target is typically a protocol for talking to debugging
10907 facilities. You use the argument @var{type} to specify the type or
10908 protocol of the target machine.
10910 Further @var{parameters} are interpreted by the target protocol, but
10911 typically include things like device names or host names to connect
10912 with, process numbers, and baud rates.
10914 The @code{target} command does not repeat if you press @key{RET} again
10915 after executing the command.
10917 @kindex help target
10919 Displays the names of all targets available. To display targets
10920 currently selected, use either @code{info target} or @code{info files}
10921 (@pxref{Files, ,Commands to specify files}).
10923 @item help target @var{name}
10924 Describe a particular target, including any parameters necessary to
10927 @kindex set gnutarget
10928 @item set gnutarget @var{args}
10929 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
10930 knows whether it is reading an @dfn{executable},
10931 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
10932 with the @code{set gnutarget} command. Unlike most @code{target} commands,
10933 with @code{gnutarget} the @code{target} refers to a program, not a machine.
10936 @emph{Warning:} To specify a file format with @code{set gnutarget},
10937 you must know the actual BFD name.
10941 @xref{Files, , Commands to specify files}.
10943 @kindex show gnutarget
10944 @item show gnutarget
10945 Use the @code{show gnutarget} command to display what file format
10946 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
10947 @value{GDBN} will determine the file format for each file automatically,
10948 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
10951 @cindex common targets
10952 Here are some common targets (available, or not, depending on the GDB
10957 @item target exec @var{program}
10958 @cindex executable file target
10959 An executable file. @samp{target exec @var{program}} is the same as
10960 @samp{exec-file @var{program}}.
10962 @item target core @var{filename}
10963 @cindex core dump file target
10964 A core dump file. @samp{target core @var{filename}} is the same as
10965 @samp{core-file @var{filename}}.
10967 @item target remote @var{dev}
10968 @cindex remote target
10969 Remote serial target in GDB-specific protocol. The argument @var{dev}
10970 specifies what serial device to use for the connection (e.g.
10971 @file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote}
10972 supports the @code{load} command. This is only useful if you have
10973 some other way of getting the stub to the target system, and you can put
10974 it somewhere in memory where it won't get clobbered by the download.
10977 @cindex built-in simulator target
10978 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
10986 works; however, you cannot assume that a specific memory map, device
10987 drivers, or even basic I/O is available, although some simulators do
10988 provide these. For info about any processor-specific simulator details,
10989 see the appropriate section in @ref{Embedded Processors, ,Embedded
10994 Some configurations may include these targets as well:
10998 @item target nrom @var{dev}
10999 @cindex NetROM ROM emulator target
11000 NetROM ROM emulator. This target only supports downloading.
11004 Different targets are available on different configurations of @value{GDBN};
11005 your configuration may have more or fewer targets.
11007 Many remote targets require you to download the executable's code
11008 once you've successfully established a connection.
11012 @kindex load @var{filename}
11013 @item load @var{filename}
11014 Depending on what remote debugging facilities are configured into
11015 @value{GDBN}, the @code{load} command may be available. Where it exists, it
11016 is meant to make @var{filename} (an executable) available for debugging
11017 on the remote system---by downloading, or dynamic linking, for example.
11018 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
11019 the @code{add-symbol-file} command.
11021 If your @value{GDBN} does not have a @code{load} command, attempting to
11022 execute it gets the error message ``@code{You can't do that when your
11023 target is @dots{}}''
11025 The file is loaded at whatever address is specified in the executable.
11026 For some object file formats, you can specify the load address when you
11027 link the program; for other formats, like a.out, the object file format
11028 specifies a fixed address.
11029 @c FIXME! This would be a good place for an xref to the GNU linker doc.
11031 @code{load} does not repeat if you press @key{RET} again after using it.
11035 @section Choosing target byte order
11037 @cindex choosing target byte order
11038 @cindex target byte order
11040 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
11041 offer the ability to run either big-endian or little-endian byte
11042 orders. Usually the executable or symbol will include a bit to
11043 designate the endian-ness, and you will not need to worry about
11044 which to use. However, you may still find it useful to adjust
11045 @value{GDBN}'s idea of processor endian-ness manually.
11049 @item set endian big
11050 Instruct @value{GDBN} to assume the target is big-endian.
11052 @item set endian little
11053 Instruct @value{GDBN} to assume the target is little-endian.
11055 @item set endian auto
11056 Instruct @value{GDBN} to use the byte order associated with the
11060 Display @value{GDBN}'s current idea of the target byte order.
11064 Note that these commands merely adjust interpretation of symbolic
11065 data on the host, and that they have absolutely no effect on the
11069 @section Remote debugging
11070 @cindex remote debugging
11072 If you are trying to debug a program running on a machine that cannot run
11073 @value{GDBN} in the usual way, it is often useful to use remote debugging.
11074 For example, you might use remote debugging on an operating system kernel,
11075 or on a small system which does not have a general purpose operating system
11076 powerful enough to run a full-featured debugger.
11078 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
11079 to make this work with particular debugging targets. In addition,
11080 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
11081 but not specific to any particular target system) which you can use if you
11082 write the remote stubs---the code that runs on the remote system to
11083 communicate with @value{GDBN}.
11085 Other remote targets may be available in your
11086 configuration of @value{GDBN}; use @code{help target} to list them.
11089 @section Kernel Object Display
11090 @cindex kernel object display
11093 Some targets support kernel object display. Using this facility,
11094 @value{GDBN} communicates specially with the underlying operating system
11095 and can display information about operating system-level objects such as
11096 mutexes and other synchronization objects. Exactly which objects can be
11097 displayed is determined on a per-OS basis.
11100 Use the @code{set os} command to set the operating system. This tells
11101 @value{GDBN} which kernel object display module to initialize:
11104 (@value{GDBP}) set os cisco
11108 The associated command @code{show os} displays the operating system
11109 set with the @code{set os} command; if no operating system has been
11110 set, @code{show os} will display an empty string @samp{""}.
11112 If @code{set os} succeeds, @value{GDBN} will display some information
11113 about the operating system, and will create a new @code{info} command
11114 which can be used to query the target. The @code{info} command is named
11115 after the operating system:
11119 (@value{GDBP}) info cisco
11120 List of Cisco Kernel Objects
11122 any Any and all objects
11125 Further subcommands can be used to query about particular objects known
11128 There is currently no way to determine whether a given operating
11129 system is supported other than to try setting it with @kbd{set os
11130 @var{name}}, where @var{name} is the name of the operating system you
11134 @node Remote Debugging
11135 @chapter Debugging remote programs
11138 * Connecting:: Connecting to a remote target
11139 * Server:: Using the gdbserver program
11140 * NetWare:: Using the gdbserve.nlm program
11141 * Remote configuration:: Remote configuration
11142 * remote stub:: Implementing a remote stub
11146 @section Connecting to a remote target
11148 On the @value{GDBN} host machine, you will need an unstripped copy of
11149 your program, since @value{GDBN} needs symobl and debugging information.
11150 Start up @value{GDBN} as usual, using the name of the local copy of your
11151 program as the first argument.
11153 @cindex serial line, @code{target remote}
11154 If you're using a serial line, you may want to give @value{GDBN} the
11155 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
11156 before the @code{target} command.
11158 After that, use @code{target remote} to establish communications with
11159 the target machine. Its argument specifies how to communicate---either
11160 via a devicename attached to a direct serial line, or a TCP or UDP port
11161 (possibly to a terminal server which in turn has a serial line to the
11162 target). For example, to use a serial line connected to the device
11163 named @file{/dev/ttyb}:
11166 target remote /dev/ttyb
11169 @cindex TCP port, @code{target remote}
11170 To use a TCP connection, use an argument of the form
11171 @code{@var{host}:@var{port}} or @code{tcp:@var{host}:@var{port}}.
11172 For example, to connect to port 2828 on a
11173 terminal server named @code{manyfarms}:
11176 target remote manyfarms:2828
11179 If your remote target is actually running on the same machine as
11180 your debugger session (e.g.@: a simulator of your target running on
11181 the same host), you can omit the hostname. For example, to connect
11182 to port 1234 on your local machine:
11185 target remote :1234
11189 Note that the colon is still required here.
11191 @cindex UDP port, @code{target remote}
11192 To use a UDP connection, use an argument of the form
11193 @code{udp:@var{host}:@var{port}}. For example, to connect to UDP port 2828
11194 on a terminal server named @code{manyfarms}:
11197 target remote udp:manyfarms:2828
11200 When using a UDP connection for remote debugging, you should keep in mind
11201 that the `U' stands for ``Unreliable''. UDP can silently drop packets on
11202 busy or unreliable networks, which will cause havoc with your debugging
11205 Now you can use all the usual commands to examine and change data and to
11206 step and continue the remote program.
11208 @cindex interrupting remote programs
11209 @cindex remote programs, interrupting
11210 Whenever @value{GDBN} is waiting for the remote program, if you type the
11211 interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
11212 program. This may or may not succeed, depending in part on the hardware
11213 and the serial drivers the remote system uses. If you type the
11214 interrupt character once again, @value{GDBN} displays this prompt:
11217 Interrupted while waiting for the program.
11218 Give up (and stop debugging it)? (y or n)
11221 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
11222 (If you decide you want to try again later, you can use @samp{target
11223 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
11224 goes back to waiting.
11227 @kindex detach (remote)
11229 When you have finished debugging the remote program, you can use the
11230 @code{detach} command to release it from @value{GDBN} control.
11231 Detaching from the target normally resumes its execution, but the results
11232 will depend on your particular remote stub. After the @code{detach}
11233 command, @value{GDBN} is free to connect to another target.
11237 The @code{disconnect} command behaves like @code{detach}, except that
11238 the target is generally not resumed. It will wait for @value{GDBN}
11239 (this instance or another one) to connect and continue debugging. After
11240 the @code{disconnect} command, @value{GDBN} is again free to connect to
11245 @section Using the @code{gdbserver} program
11248 @cindex remote connection without stubs
11249 @code{gdbserver} is a control program for Unix-like systems, which
11250 allows you to connect your program with a remote @value{GDBN} via
11251 @code{target remote}---but without linking in the usual debugging stub.
11253 @code{gdbserver} is not a complete replacement for the debugging stubs,
11254 because it requires essentially the same operating-system facilities
11255 that @value{GDBN} itself does. In fact, a system that can run
11256 @code{gdbserver} to connect to a remote @value{GDBN} could also run
11257 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
11258 because it is a much smaller program than @value{GDBN} itself. It is
11259 also easier to port than all of @value{GDBN}, so you may be able to get
11260 started more quickly on a new system by using @code{gdbserver}.
11261 Finally, if you develop code for real-time systems, you may find that
11262 the tradeoffs involved in real-time operation make it more convenient to
11263 do as much development work as possible on another system, for example
11264 by cross-compiling. You can use @code{gdbserver} to make a similar
11265 choice for debugging.
11267 @value{GDBN} and @code{gdbserver} communicate via either a serial line
11268 or a TCP connection, using the standard @value{GDBN} remote serial
11272 @item On the target machine,
11273 you need to have a copy of the program you want to debug.
11274 @code{gdbserver} does not need your program's symbol table, so you can
11275 strip the program if necessary to save space. @value{GDBN} on the host
11276 system does all the symbol handling.
11278 To use the server, you must tell it how to communicate with @value{GDBN};
11279 the name of your program; and the arguments for your program. The usual
11283 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
11286 @var{comm} is either a device name (to use a serial line) or a TCP
11287 hostname and portnumber. For example, to debug Emacs with the argument
11288 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
11292 target> gdbserver /dev/com1 emacs foo.txt
11295 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
11298 To use a TCP connection instead of a serial line:
11301 target> gdbserver host:2345 emacs foo.txt
11304 The only difference from the previous example is the first argument,
11305 specifying that you are communicating with the host @value{GDBN} via
11306 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
11307 expect a TCP connection from machine @samp{host} to local TCP port 2345.
11308 (Currently, the @samp{host} part is ignored.) You can choose any number
11309 you want for the port number as long as it does not conflict with any
11310 TCP ports already in use on the target system (for example, @code{23} is
11311 reserved for @code{telnet}).@footnote{If you choose a port number that
11312 conflicts with another service, @code{gdbserver} prints an error message
11313 and exits.} You must use the same port number with the host @value{GDBN}
11314 @code{target remote} command.
11316 On some targets, @code{gdbserver} can also attach to running programs.
11317 This is accomplished via the @code{--attach} argument. The syntax is:
11320 target> gdbserver @var{comm} --attach @var{pid}
11323 @var{pid} is the process ID of a currently running process. It isn't necessary
11324 to point @code{gdbserver} at a binary for the running process.
11327 @cindex attach to a program by name
11328 You can debug processes by name instead of process ID if your target has the
11329 @code{pidof} utility:
11332 target> gdbserver @var{comm} --attach `pidof @var{PROGRAM}`
11335 In case more than one copy of @var{PROGRAM} is running, or @var{PROGRAM}
11336 has multiple threads, most versions of @code{pidof} support the
11337 @code{-s} option to only return the first process ID.
11339 @item On the host machine,
11340 connect to your target (@pxref{Connecting,,Connecting to a remote target}).
11341 For TCP connections, you must start up @code{gdbserver} prior to using
11342 the @code{target remote} command. Otherwise you may get an error whose
11343 text depends on the host system, but which usually looks something like
11344 @samp{Connection refused}. You don't need to use the @code{load}
11345 command in @value{GDBN} when using gdbserver, since the program is
11346 already on the target.
11351 @section Using the @code{gdbserve.nlm} program
11353 @kindex gdbserve.nlm
11354 @code{gdbserve.nlm} is a control program for NetWare systems, which
11355 allows you to connect your program with a remote @value{GDBN} via
11356 @code{target remote}.
11358 @value{GDBN} and @code{gdbserve.nlm} communicate via a serial line,
11359 using the standard @value{GDBN} remote serial protocol.
11362 @item On the target machine,
11363 you need to have a copy of the program you want to debug.
11364 @code{gdbserve.nlm} does not need your program's symbol table, so you
11365 can strip the program if necessary to save space. @value{GDBN} on the
11366 host system does all the symbol handling.
11368 To use the server, you must tell it how to communicate with
11369 @value{GDBN}; the name of your program; and the arguments for your
11370 program. The syntax is:
11373 load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ]
11374 [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ]
11377 @var{board} and @var{port} specify the serial line; @var{baud} specifies
11378 the baud rate used by the connection. @var{port} and @var{node} default
11379 to 0, @var{baud} defaults to 9600@dmn{bps}.
11381 For example, to debug Emacs with the argument @samp{foo.txt}and
11382 communicate with @value{GDBN} over serial port number 2 or board 1
11383 using a 19200@dmn{bps} connection:
11386 load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
11390 On the @value{GDBN} host machine, connect to your target (@pxref{Connecting,,
11391 Connecting to a remote target}).
11395 @node Remote configuration
11396 @section Remote configuration
11398 The following configuration options are available when debugging remote
11402 @kindex set remote hardware-watchpoint-limit
11403 @kindex set remote hardware-breakpoint-limit
11404 @anchor{set remote hardware-watchpoint-limit}
11405 @anchor{set remote hardware-breakpoint-limit}
11406 @item set remote hardware-watchpoint-limit @var{limit}
11407 @itemx set remote hardware-breakpoint-limit @var{limit}
11408 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
11409 watchpoints. A limit of -1, the default, is treated as unlimited.
11413 @section Implementing a remote stub
11415 @cindex debugging stub, example
11416 @cindex remote stub, example
11417 @cindex stub example, remote debugging
11418 The stub files provided with @value{GDBN} implement the target side of the
11419 communication protocol, and the @value{GDBN} side is implemented in the
11420 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
11421 these subroutines to communicate, and ignore the details. (If you're
11422 implementing your own stub file, you can still ignore the details: start
11423 with one of the existing stub files. @file{sparc-stub.c} is the best
11424 organized, and therefore the easiest to read.)
11426 @cindex remote serial debugging, overview
11427 To debug a program running on another machine (the debugging
11428 @dfn{target} machine), you must first arrange for all the usual
11429 prerequisites for the program to run by itself. For example, for a C
11434 A startup routine to set up the C runtime environment; these usually
11435 have a name like @file{crt0}. The startup routine may be supplied by
11436 your hardware supplier, or you may have to write your own.
11439 A C subroutine library to support your program's
11440 subroutine calls, notably managing input and output.
11443 A way of getting your program to the other machine---for example, a
11444 download program. These are often supplied by the hardware
11445 manufacturer, but you may have to write your own from hardware
11449 The next step is to arrange for your program to use a serial port to
11450 communicate with the machine where @value{GDBN} is running (the @dfn{host}
11451 machine). In general terms, the scheme looks like this:
11455 @value{GDBN} already understands how to use this protocol; when everything
11456 else is set up, you can simply use the @samp{target remote} command
11457 (@pxref{Targets,,Specifying a Debugging Target}).
11459 @item On the target,
11460 you must link with your program a few special-purpose subroutines that
11461 implement the @value{GDBN} remote serial protocol. The file containing these
11462 subroutines is called a @dfn{debugging stub}.
11464 On certain remote targets, you can use an auxiliary program
11465 @code{gdbserver} instead of linking a stub into your program.
11466 @xref{Server,,Using the @code{gdbserver} program}, for details.
11469 The debugging stub is specific to the architecture of the remote
11470 machine; for example, use @file{sparc-stub.c} to debug programs on
11473 @cindex remote serial stub list
11474 These working remote stubs are distributed with @value{GDBN}:
11479 @cindex @file{i386-stub.c}
11482 For Intel 386 and compatible architectures.
11485 @cindex @file{m68k-stub.c}
11486 @cindex Motorola 680x0
11488 For Motorola 680x0 architectures.
11491 @cindex @file{sh-stub.c}
11494 For Renesas SH architectures.
11497 @cindex @file{sparc-stub.c}
11499 For @sc{sparc} architectures.
11501 @item sparcl-stub.c
11502 @cindex @file{sparcl-stub.c}
11505 For Fujitsu @sc{sparclite} architectures.
11509 The @file{README} file in the @value{GDBN} distribution may list other
11510 recently added stubs.
11513 * Stub Contents:: What the stub can do for you
11514 * Bootstrapping:: What you must do for the stub
11515 * Debug Session:: Putting it all together
11518 @node Stub Contents
11519 @subsection What the stub can do for you
11521 @cindex remote serial stub
11522 The debugging stub for your architecture supplies these three
11526 @item set_debug_traps
11527 @findex set_debug_traps
11528 @cindex remote serial stub, initialization
11529 This routine arranges for @code{handle_exception} to run when your
11530 program stops. You must call this subroutine explicitly near the
11531 beginning of your program.
11533 @item handle_exception
11534 @findex handle_exception
11535 @cindex remote serial stub, main routine
11536 This is the central workhorse, but your program never calls it
11537 explicitly---the setup code arranges for @code{handle_exception} to
11538 run when a trap is triggered.
11540 @code{handle_exception} takes control when your program stops during
11541 execution (for example, on a breakpoint), and mediates communications
11542 with @value{GDBN} on the host machine. This is where the communications
11543 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
11544 representative on the target machine. It begins by sending summary
11545 information on the state of your program, then continues to execute,
11546 retrieving and transmitting any information @value{GDBN} needs, until you
11547 execute a @value{GDBN} command that makes your program resume; at that point,
11548 @code{handle_exception} returns control to your own code on the target
11552 @cindex @code{breakpoint} subroutine, remote
11553 Use this auxiliary subroutine to make your program contain a
11554 breakpoint. Depending on the particular situation, this may be the only
11555 way for @value{GDBN} to get control. For instance, if your target
11556 machine has some sort of interrupt button, you won't need to call this;
11557 pressing the interrupt button transfers control to
11558 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
11559 simply receiving characters on the serial port may also trigger a trap;
11560 again, in that situation, you don't need to call @code{breakpoint} from
11561 your own program---simply running @samp{target remote} from the host
11562 @value{GDBN} session gets control.
11564 Call @code{breakpoint} if none of these is true, or if you simply want
11565 to make certain your program stops at a predetermined point for the
11566 start of your debugging session.
11569 @node Bootstrapping
11570 @subsection What you must do for the stub
11572 @cindex remote stub, support routines
11573 The debugging stubs that come with @value{GDBN} are set up for a particular
11574 chip architecture, but they have no information about the rest of your
11575 debugging target machine.
11577 First of all you need to tell the stub how to communicate with the
11581 @item int getDebugChar()
11582 @findex getDebugChar
11583 Write this subroutine to read a single character from the serial port.
11584 It may be identical to @code{getchar} for your target system; a
11585 different name is used to allow you to distinguish the two if you wish.
11587 @item void putDebugChar(int)
11588 @findex putDebugChar
11589 Write this subroutine to write a single character to the serial port.
11590 It may be identical to @code{putchar} for your target system; a
11591 different name is used to allow you to distinguish the two if you wish.
11594 @cindex control C, and remote debugging
11595 @cindex interrupting remote targets
11596 If you want @value{GDBN} to be able to stop your program while it is
11597 running, you need to use an interrupt-driven serial driver, and arrange
11598 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
11599 character). That is the character which @value{GDBN} uses to tell the
11600 remote system to stop.
11602 Getting the debugging target to return the proper status to @value{GDBN}
11603 probably requires changes to the standard stub; one quick and dirty way
11604 is to just execute a breakpoint instruction (the ``dirty'' part is that
11605 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
11607 Other routines you need to supply are:
11610 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
11611 @findex exceptionHandler
11612 Write this function to install @var{exception_address} in the exception
11613 handling tables. You need to do this because the stub does not have any
11614 way of knowing what the exception handling tables on your target system
11615 are like (for example, the processor's table might be in @sc{rom},
11616 containing entries which point to a table in @sc{ram}).
11617 @var{exception_number} is the exception number which should be changed;
11618 its meaning is architecture-dependent (for example, different numbers
11619 might represent divide by zero, misaligned access, etc). When this
11620 exception occurs, control should be transferred directly to
11621 @var{exception_address}, and the processor state (stack, registers,
11622 and so on) should be just as it is when a processor exception occurs. So if
11623 you want to use a jump instruction to reach @var{exception_address}, it
11624 should be a simple jump, not a jump to subroutine.
11626 For the 386, @var{exception_address} should be installed as an interrupt
11627 gate so that interrupts are masked while the handler runs. The gate
11628 should be at privilege level 0 (the most privileged level). The
11629 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
11630 help from @code{exceptionHandler}.
11632 @item void flush_i_cache()
11633 @findex flush_i_cache
11634 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
11635 instruction cache, if any, on your target machine. If there is no
11636 instruction cache, this subroutine may be a no-op.
11638 On target machines that have instruction caches, @value{GDBN} requires this
11639 function to make certain that the state of your program is stable.
11643 You must also make sure this library routine is available:
11646 @item void *memset(void *, int, int)
11648 This is the standard library function @code{memset} that sets an area of
11649 memory to a known value. If you have one of the free versions of
11650 @code{libc.a}, @code{memset} can be found there; otherwise, you must
11651 either obtain it from your hardware manufacturer, or write your own.
11654 If you do not use the GNU C compiler, you may need other standard
11655 library subroutines as well; this varies from one stub to another,
11656 but in general the stubs are likely to use any of the common library
11657 subroutines which @code{@value{GCC}} generates as inline code.
11660 @node Debug Session
11661 @subsection Putting it all together
11663 @cindex remote serial debugging summary
11664 In summary, when your program is ready to debug, you must follow these
11669 Make sure you have defined the supporting low-level routines
11670 (@pxref{Bootstrapping,,What you must do for the stub}):
11672 @code{getDebugChar}, @code{putDebugChar},
11673 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
11677 Insert these lines near the top of your program:
11685 For the 680x0 stub only, you need to provide a variable called
11686 @code{exceptionHook}. Normally you just use:
11689 void (*exceptionHook)() = 0;
11693 but if before calling @code{set_debug_traps}, you set it to point to a
11694 function in your program, that function is called when
11695 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
11696 error). The function indicated by @code{exceptionHook} is called with
11697 one parameter: an @code{int} which is the exception number.
11700 Compile and link together: your program, the @value{GDBN} debugging stub for
11701 your target architecture, and the supporting subroutines.
11704 Make sure you have a serial connection between your target machine and
11705 the @value{GDBN} host, and identify the serial port on the host.
11708 @c The "remote" target now provides a `load' command, so we should
11709 @c document that. FIXME.
11710 Download your program to your target machine (or get it there by
11711 whatever means the manufacturer provides), and start it.
11714 Start @value{GDBN} on the host, and connect to the target
11715 (@pxref{Connecting,,Connecting to a remote target}).
11719 @node Configurations
11720 @chapter Configuration-Specific Information
11722 While nearly all @value{GDBN} commands are available for all native and
11723 cross versions of the debugger, there are some exceptions. This chapter
11724 describes things that are only available in certain configurations.
11726 There are three major categories of configurations: native
11727 configurations, where the host and target are the same, embedded
11728 operating system configurations, which are usually the same for several
11729 different processor architectures, and bare embedded processors, which
11730 are quite different from each other.
11735 * Embedded Processors::
11742 This section describes details specific to particular native
11747 * BSD libkvm Interface:: Debugging BSD kernel memory images
11748 * SVR4 Process Information:: SVR4 process information
11749 * DJGPP Native:: Features specific to the DJGPP port
11750 * Cygwin Native:: Features specific to the Cygwin port
11756 On HP-UX systems, if you refer to a function or variable name that
11757 begins with a dollar sign, @value{GDBN} searches for a user or system
11758 name first, before it searches for a convenience variable.
11760 @node BSD libkvm Interface
11761 @subsection BSD libkvm Interface
11764 @cindex kernel memory image
11765 @cindex kernel crash dump
11767 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
11768 interface that provides a uniform interface for accessing kernel virtual
11769 memory images, including live systems and crash dumps. @value{GDBN}
11770 uses this interface to allow you to debug live kernels and kernel crash
11771 dumps on many native BSD configurations. This is implemented as a
11772 special @code{kvm} debugging target. For debugging a live system, load
11773 the currently running kernel into @value{GDBN} and connect to the
11777 (@value{GDBP}) @b{target kvm}
11780 For debugging crash dumps, provide the file name of the crash dump as an
11784 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
11787 Once connected to the @code{kvm} target, the following commands are
11793 Set current context from pcb address.
11796 Set current context from proc address. This command isn't available on
11797 modern FreeBSD systems.
11800 @node SVR4 Process Information
11801 @subsection SVR4 process information
11803 @cindex examine process image
11804 @cindex process info via @file{/proc}
11806 Many versions of SVR4 and compatible systems provide a facility called
11807 @samp{/proc} that can be used to examine the image of a running
11808 process using file-system subroutines. If @value{GDBN} is configured
11809 for an operating system with this facility, the command @code{info
11810 proc} is available to report information about the process running
11811 your program, or about any process running on your system. @code{info
11812 proc} works only on SVR4 systems that include the @code{procfs} code.
11813 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
11814 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
11820 @itemx info proc @var{process-id}
11821 Summarize available information about any running process. If a
11822 process ID is specified by @var{process-id}, display information about
11823 that process; otherwise display information about the program being
11824 debugged. The summary includes the debugged process ID, the command
11825 line used to invoke it, its current working directory, and its
11826 executable file's absolute file name.
11828 On some systems, @var{process-id} can be of the form
11829 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
11830 within a process. If the optional @var{pid} part is missing, it means
11831 a thread from the process being debugged (the leading @samp{/} still
11832 needs to be present, or else @value{GDBN} will interpret the number as
11833 a process ID rather than a thread ID).
11835 @item info proc mappings
11836 @cindex memory address space mappings
11837 Report the memory address space ranges accessible in the program, with
11838 information on whether the process has read, write, or execute access
11839 rights to each range. On @sc{gnu}/Linux systems, each memory range
11840 includes the object file which is mapped to that range, instead of the
11841 memory access rights to that range.
11843 @item info proc stat
11844 @itemx info proc status
11845 @cindex process detailed status information
11846 These subcommands are specific to @sc{gnu}/Linux systems. They show
11847 the process-related information, including the user ID and group ID;
11848 how many threads are there in the process; its virtual memory usage;
11849 the signals that are pending, blocked, and ignored; its TTY; its
11850 consumption of system and user time; its stack size; its @samp{nice}
11851 value; etc. For more information, see the @samp{proc(5)} man page
11852 (type @kbd{man 5 proc} from your shell prompt).
11854 @item info proc all
11855 Show all the information about the process described under all of the
11856 above @code{info proc} subcommands.
11859 @comment These sub-options of 'info proc' were not included when
11860 @comment procfs.c was re-written. Keep their descriptions around
11861 @comment against the day when someone finds the time to put them back in.
11862 @kindex info proc times
11863 @item info proc times
11864 Starting time, user CPU time, and system CPU time for your program and
11867 @kindex info proc id
11869 Report on the process IDs related to your program: its own process ID,
11870 the ID of its parent, the process group ID, and the session ID.
11875 @subsection Features for Debugging @sc{djgpp} Programs
11876 @cindex @sc{djgpp} debugging
11877 @cindex native @sc{djgpp} debugging
11878 @cindex MS-DOS-specific commands
11880 @sc{djgpp} is the port of @sc{gnu} development tools to MS-DOS and
11881 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
11882 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
11883 top of real-mode DOS systems and their emulations.
11885 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
11886 defines a few commands specific to the @sc{djgpp} port. This
11887 subsection describes those commands.
11892 This is a prefix of @sc{djgpp}-specific commands which print
11893 information about the target system and important OS structures.
11896 @cindex MS-DOS system info
11897 @cindex free memory information (MS-DOS)
11898 @item info dos sysinfo
11899 This command displays assorted information about the underlying
11900 platform: the CPU type and features, the OS version and flavor, the
11901 DPMI version, and the available conventional and DPMI memory.
11906 @cindex segment descriptor tables
11907 @cindex descriptor tables display
11909 @itemx info dos ldt
11910 @itemx info dos idt
11911 These 3 commands display entries from, respectively, Global, Local,
11912 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
11913 tables are data structures which store a descriptor for each segment
11914 that is currently in use. The segment's selector is an index into a
11915 descriptor table; the table entry for that index holds the
11916 descriptor's base address and limit, and its attributes and access
11919 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
11920 segment (used for both data and the stack), and a DOS segment (which
11921 allows access to DOS/BIOS data structures and absolute addresses in
11922 conventional memory). However, the DPMI host will usually define
11923 additional segments in order to support the DPMI environment.
11925 @cindex garbled pointers
11926 These commands allow to display entries from the descriptor tables.
11927 Without an argument, all entries from the specified table are
11928 displayed. An argument, which should be an integer expression, means
11929 display a single entry whose index is given by the argument. For
11930 example, here's a convenient way to display information about the
11931 debugged program's data segment:
11934 @exdent @code{(@value{GDBP}) info dos ldt $ds}
11935 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
11939 This comes in handy when you want to see whether a pointer is outside
11940 the data segment's limit (i.e.@: @dfn{garbled}).
11942 @cindex page tables display (MS-DOS)
11944 @itemx info dos pte
11945 These two commands display entries from, respectively, the Page
11946 Directory and the Page Tables. Page Directories and Page Tables are
11947 data structures which control how virtual memory addresses are mapped
11948 into physical addresses. A Page Table includes an entry for every
11949 page of memory that is mapped into the program's address space; there
11950 may be several Page Tables, each one holding up to 4096 entries. A
11951 Page Directory has up to 4096 entries, one each for every Page Table
11952 that is currently in use.
11954 Without an argument, @kbd{info dos pde} displays the entire Page
11955 Directory, and @kbd{info dos pte} displays all the entries in all of
11956 the Page Tables. An argument, an integer expression, given to the
11957 @kbd{info dos pde} command means display only that entry from the Page
11958 Directory table. An argument given to the @kbd{info dos pte} command
11959 means display entries from a single Page Table, the one pointed to by
11960 the specified entry in the Page Directory.
11962 @cindex direct memory access (DMA) on MS-DOS
11963 These commands are useful when your program uses @dfn{DMA} (Direct
11964 Memory Access), which needs physical addresses to program the DMA
11967 These commands are supported only with some DPMI servers.
11969 @cindex physical address from linear address
11970 @item info dos address-pte @var{addr}
11971 This command displays the Page Table entry for a specified linear
11972 address. The argument linear address @var{addr} should already have the
11973 appropriate segment's base address added to it, because this command
11974 accepts addresses which may belong to @emph{any} segment. For
11975 example, here's how to display the Page Table entry for the page where
11976 the variable @code{i} is stored:
11979 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
11980 @exdent @code{Page Table entry for address 0x11a00d30:}
11981 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
11985 This says that @code{i} is stored at offset @code{0xd30} from the page
11986 whose physical base address is @code{0x02698000}, and prints all the
11987 attributes of that page.
11989 Note that you must cast the addresses of variables to a @code{char *},
11990 since otherwise the value of @code{__djgpp_base_address}, the base
11991 address of all variables and functions in a @sc{djgpp} program, will
11992 be added using the rules of C pointer arithmetics: if @code{i} is
11993 declared an @code{int}, @value{GDBN} will add 4 times the value of
11994 @code{__djgpp_base_address} to the address of @code{i}.
11996 Here's another example, it displays the Page Table entry for the
12000 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
12001 @exdent @code{Page Table entry for address 0x29110:}
12002 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
12006 (The @code{+ 3} offset is because the transfer buffer's address is the
12007 3rd member of the @code{_go32_info_block} structure.) The output of
12008 this command clearly shows that addresses in conventional memory are
12009 mapped 1:1, i.e.@: the physical and linear addresses are identical.
12011 This command is supported only with some DPMI servers.
12014 @node Cygwin Native
12015 @subsection Features for Debugging MS Windows PE executables
12016 @cindex MS Windows debugging
12017 @cindex native Cygwin debugging
12018 @cindex Cygwin-specific commands
12020 @value{GDBN} supports native debugging of MS Windows programs, including
12021 DLLs with and without symbolic debugging information. There are various
12022 additional Cygwin-specific commands, described in this subsection. The
12023 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
12024 that have no debugging symbols.
12030 This is a prefix of MS Windows specific commands which print
12031 information about the target system and important OS structures.
12033 @item info w32 selector
12034 This command displays information returned by
12035 the Win32 API @code{GetThreadSelectorEntry} function.
12036 It takes an optional argument that is evaluated to
12037 a long value to give the information about this given selector.
12038 Without argument, this command displays information
12039 about the the six segment registers.
12043 This is a Cygwin specific alias of info shared.
12045 @kindex dll-symbols
12047 This command loads symbols from a dll similarly to
12048 add-sym command but without the need to specify a base address.
12050 @kindex set new-console
12051 @item set new-console @var{mode}
12052 If @var{mode} is @code{on} the debuggee will
12053 be started in a new console on next start.
12054 If @var{mode} is @code{off}i, the debuggee will
12055 be started in the same console as the debugger.
12057 @kindex show new-console
12058 @item show new-console
12059 Displays whether a new console is used
12060 when the debuggee is started.
12062 @kindex set new-group
12063 @item set new-group @var{mode}
12064 This boolean value controls whether the debuggee should
12065 start a new group or stay in the same group as the debugger.
12066 This affects the way the Windows OS handles
12069 @kindex show new-group
12070 @item show new-group
12071 Displays current value of new-group boolean.
12073 @kindex set debugevents
12074 @item set debugevents
12075 This boolean value adds debug output concerning events seen by the debugger.
12077 @kindex set debugexec
12078 @item set debugexec
12079 This boolean value adds debug output concerning execute events
12080 seen by the debugger.
12082 @kindex set debugexceptions
12083 @item set debugexceptions
12084 This boolean value adds debug ouptut concerning exception events
12085 seen by the debugger.
12087 @kindex set debugmemory
12088 @item set debugmemory
12089 This boolean value adds debug ouptut concerning memory events
12090 seen by the debugger.
12094 This boolean values specifies whether the debuggee is called
12095 via a shell or directly (default value is on).
12099 Displays if the debuggee will be started with a shell.
12104 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
12107 @node Non-debug DLL symbols
12108 @subsubsection Support for DLLs without debugging symbols
12109 @cindex DLLs with no debugging symbols
12110 @cindex Minimal symbols and DLLs
12112 Very often on windows, some of the DLLs that your program relies on do
12113 not include symbolic debugging information (for example,
12114 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
12115 symbols in a DLL, it relies on the minimal amount of symbolic
12116 information contained in the DLL's export table. This subsubsection
12117 describes working with such symbols, known internally to @value{GDBN} as
12118 ``minimal symbols''.
12120 Note that before the debugged program has started execution, no DLLs
12121 will have been loaded. The easiest way around this problem is simply to
12122 start the program --- either by setting a breakpoint or letting the
12123 program run once to completion. It is also possible to force
12124 @value{GDBN} to load a particular DLL before starting the executable ---
12125 see the shared library information in @pxref{Files} or the
12126 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
12127 explicitly loading symbols from a DLL with no debugging information will
12128 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
12129 which may adversely affect symbol lookup performance.
12131 @subsubsection DLL name prefixes
12133 In keeping with the naming conventions used by the Microsoft debugging
12134 tools, DLL export symbols are made available with a prefix based on the
12135 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
12136 also entered into the symbol table, so @code{CreateFileA} is often
12137 sufficient. In some cases there will be name clashes within a program
12138 (particularly if the executable itself includes full debugging symbols)
12139 necessitating the use of the fully qualified name when referring to the
12140 contents of the DLL. Use single-quotes around the name to avoid the
12141 exclamation mark (``!'') being interpreted as a language operator.
12143 Note that the internal name of the DLL may be all upper-case, even
12144 though the file name of the DLL is lower-case, or vice-versa. Since
12145 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
12146 some confusion. If in doubt, try the @code{info functions} and
12147 @code{info variables} commands or even @code{maint print msymbols} (see
12148 @pxref{Symbols}). Here's an example:
12151 (@value{GDBP}) info function CreateFileA
12152 All functions matching regular expression "CreateFileA":
12154 Non-debugging symbols:
12155 0x77e885f4 CreateFileA
12156 0x77e885f4 KERNEL32!CreateFileA
12160 (@value{GDBP}) info function !
12161 All functions matching regular expression "!":
12163 Non-debugging symbols:
12164 0x6100114c cygwin1!__assert
12165 0x61004034 cygwin1!_dll_crt0@@0
12166 0x61004240 cygwin1!dll_crt0(per_process *)
12170 @subsubsection Working with minimal symbols
12172 Symbols extracted from a DLL's export table do not contain very much
12173 type information. All that @value{GDBN} can do is guess whether a symbol
12174 refers to a function or variable depending on the linker section that
12175 contains the symbol. Also note that the actual contents of the memory
12176 contained in a DLL are not available unless the program is running. This
12177 means that you cannot examine the contents of a variable or disassemble
12178 a function within a DLL without a running program.
12180 Variables are generally treated as pointers and dereferenced
12181 automatically. For this reason, it is often necessary to prefix a
12182 variable name with the address-of operator (``&'') and provide explicit
12183 type information in the command. Here's an example of the type of
12187 (@value{GDBP}) print 'cygwin1!__argv'
12192 (@value{GDBP}) x 'cygwin1!__argv'
12193 0x10021610: "\230y\""
12196 And two possible solutions:
12199 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
12200 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
12204 (@value{GDBP}) x/2x &'cygwin1!__argv'
12205 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
12206 (@value{GDBP}) x/x 0x10021608
12207 0x10021608: 0x0022fd98
12208 (@value{GDBP}) x/s 0x0022fd98
12209 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
12212 Setting a break point within a DLL is possible even before the program
12213 starts execution. However, under these circumstances, @value{GDBN} can't
12214 examine the initial instructions of the function in order to skip the
12215 function's frame set-up code. You can work around this by using ``*&''
12216 to set the breakpoint at a raw memory address:
12219 (@value{GDBP}) break *&'python22!PyOS_Readline'
12220 Breakpoint 1 at 0x1e04eff0
12223 The author of these extensions is not entirely convinced that setting a
12224 break point within a shared DLL like @file{kernel32.dll} is completely
12228 @section Embedded Operating Systems
12230 This section describes configurations involving the debugging of
12231 embedded operating systems that are available for several different
12235 * VxWorks:: Using @value{GDBN} with VxWorks
12238 @value{GDBN} includes the ability to debug programs running on
12239 various real-time operating systems.
12242 @subsection Using @value{GDBN} with VxWorks
12248 @kindex target vxworks
12249 @item target vxworks @var{machinename}
12250 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
12251 is the target system's machine name or IP address.
12255 On VxWorks, @code{load} links @var{filename} dynamically on the
12256 current target system as well as adding its symbols in @value{GDBN}.
12258 @value{GDBN} enables developers to spawn and debug tasks running on networked
12259 VxWorks targets from a Unix host. Already-running tasks spawned from
12260 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
12261 both the Unix host and on the VxWorks target. The program
12262 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
12263 installed with the name @code{vxgdb}, to distinguish it from a
12264 @value{GDBN} for debugging programs on the host itself.)
12267 @item VxWorks-timeout @var{args}
12268 @kindex vxworks-timeout
12269 All VxWorks-based targets now support the option @code{vxworks-timeout}.
12270 This option is set by the user, and @var{args} represents the number of
12271 seconds @value{GDBN} waits for responses to rpc's. You might use this if
12272 your VxWorks target is a slow software simulator or is on the far side
12273 of a thin network line.
12276 The following information on connecting to VxWorks was current when
12277 this manual was produced; newer releases of VxWorks may use revised
12280 @findex INCLUDE_RDB
12281 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
12282 to include the remote debugging interface routines in the VxWorks
12283 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
12284 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
12285 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
12286 source debugging task @code{tRdbTask} when VxWorks is booted. For more
12287 information on configuring and remaking VxWorks, see the manufacturer's
12289 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
12291 Once you have included @file{rdb.a} in your VxWorks system image and set
12292 your Unix execution search path to find @value{GDBN}, you are ready to
12293 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
12294 @code{vxgdb}, depending on your installation).
12296 @value{GDBN} comes up showing the prompt:
12303 * VxWorks Connection:: Connecting to VxWorks
12304 * VxWorks Download:: VxWorks download
12305 * VxWorks Attach:: Running tasks
12308 @node VxWorks Connection
12309 @subsubsection Connecting to VxWorks
12311 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
12312 network. To connect to a target whose host name is ``@code{tt}'', type:
12315 (vxgdb) target vxworks tt
12319 @value{GDBN} displays messages like these:
12322 Attaching remote machine across net...
12327 @value{GDBN} then attempts to read the symbol tables of any object modules
12328 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
12329 these files by searching the directories listed in the command search
12330 path (@pxref{Environment, ,Your program's environment}); if it fails
12331 to find an object file, it displays a message such as:
12334 prog.o: No such file or directory.
12337 When this happens, add the appropriate directory to the search path with
12338 the @value{GDBN} command @code{path}, and execute the @code{target}
12341 @node VxWorks Download
12342 @subsubsection VxWorks download
12344 @cindex download to VxWorks
12345 If you have connected to the VxWorks target and you want to debug an
12346 object that has not yet been loaded, you can use the @value{GDBN}
12347 @code{load} command to download a file from Unix to VxWorks
12348 incrementally. The object file given as an argument to the @code{load}
12349 command is actually opened twice: first by the VxWorks target in order
12350 to download the code, then by @value{GDBN} in order to read the symbol
12351 table. This can lead to problems if the current working directories on
12352 the two systems differ. If both systems have NFS mounted the same
12353 filesystems, you can avoid these problems by using absolute paths.
12354 Otherwise, it is simplest to set the working directory on both systems
12355 to the directory in which the object file resides, and then to reference
12356 the file by its name, without any path. For instance, a program
12357 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
12358 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
12359 program, type this on VxWorks:
12362 -> cd "@var{vxpath}/vw/demo/rdb"
12366 Then, in @value{GDBN}, type:
12369 (vxgdb) cd @var{hostpath}/vw/demo/rdb
12370 (vxgdb) load prog.o
12373 @value{GDBN} displays a response similar to this:
12376 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
12379 You can also use the @code{load} command to reload an object module
12380 after editing and recompiling the corresponding source file. Note that
12381 this makes @value{GDBN} delete all currently-defined breakpoints,
12382 auto-displays, and convenience variables, and to clear the value
12383 history. (This is necessary in order to preserve the integrity of
12384 debugger's data structures that reference the target system's symbol
12387 @node VxWorks Attach
12388 @subsubsection Running tasks
12390 @cindex running VxWorks tasks
12391 You can also attach to an existing task using the @code{attach} command as
12395 (vxgdb) attach @var{task}
12399 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
12400 or suspended when you attach to it. Running tasks are suspended at
12401 the time of attachment.
12403 @node Embedded Processors
12404 @section Embedded Processors
12406 This section goes into details specific to particular embedded
12412 * H8/300:: Renesas H8/300
12413 * H8/500:: Renesas H8/500
12414 * M32R/D:: Renesas M32R/D
12415 * M68K:: Motorola M68K
12416 * MIPS Embedded:: MIPS Embedded
12417 * OpenRISC 1000:: OpenRisc 1000
12418 * PA:: HP PA Embedded
12421 * Sparclet:: Tsqware Sparclet
12422 * Sparclite:: Fujitsu Sparclite
12423 * ST2000:: Tandem ST2000
12424 * Z8000:: Zilog Z8000
12433 @item target rdi @var{dev}
12434 ARM Angel monitor, via RDI library interface to ADP protocol. You may
12435 use this target to communicate with both boards running the Angel
12436 monitor, or with the EmbeddedICE JTAG debug device.
12439 @item target rdp @var{dev}
12445 @subsection Renesas H8/300
12449 @kindex target hms@r{, with H8/300}
12450 @item target hms @var{dev}
12451 A Renesas SH, H8/300, or H8/500 board, attached via serial line to your host.
12452 Use special commands @code{device} and @code{speed} to control the serial
12453 line and the communications speed used.
12455 @kindex target e7000@r{, with H8/300}
12456 @item target e7000 @var{dev}
12457 E7000 emulator for Renesas H8 and SH.
12459 @kindex target sh3@r{, with H8/300}
12460 @kindex target sh3e@r{, with H8/300}
12461 @item target sh3 @var{dev}
12462 @itemx target sh3e @var{dev}
12463 Renesas SH-3 and SH-3E target systems.
12467 @cindex download to H8/300 or H8/500
12468 @cindex H8/300 or H8/500 download
12469 @cindex download to Renesas SH
12470 @cindex Renesas SH download
12471 When you select remote debugging to a Renesas SH, H8/300, or H8/500
12472 board, the @code{load} command downloads your program to the Renesas
12473 board and also opens it as the current executable target for
12474 @value{GDBN} on your host (like the @code{file} command).
12476 @value{GDBN} needs to know these things to talk to your
12477 Renesas SH, H8/300, or H8/500:
12481 that you want to use @samp{target hms}, the remote debugging interface
12482 for Renesas microprocessors, or @samp{target e7000}, the in-circuit
12483 emulator for the Renesas SH and the Renesas 300H. (@samp{target hms} is
12484 the default when @value{GDBN} is configured specifically for the Renesas SH,
12485 H8/300, or H8/500.)
12488 what serial device connects your host to your Renesas board (the first
12489 serial device available on your host is the default).
12492 what speed to use over the serial device.
12496 * Renesas Boards:: Connecting to Renesas boards.
12497 * Renesas ICE:: Using the E7000 In-Circuit Emulator.
12498 * Renesas Special:: Special @value{GDBN} commands for Renesas micros.
12501 @node Renesas Boards
12502 @subsubsection Connecting to Renesas boards
12504 @c only for Unix hosts
12506 @cindex serial device, Renesas micros
12507 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
12508 need to explicitly set the serial device. The default @var{port} is the
12509 first available port on your host. This is only necessary on Unix
12510 hosts, where it is typically something like @file{/dev/ttya}.
12513 @cindex serial line speed, Renesas micros
12514 @code{@value{GDBN}} has another special command to set the communications
12515 speed: @samp{speed @var{bps}}. This command also is only used from Unix
12516 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
12517 the DOS @code{mode} command (for instance,
12518 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
12520 The @samp{device} and @samp{speed} commands are available only when you
12521 use a Unix host to debug your Renesas microprocessor programs. If you
12523 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
12524 called @code{asynctsr} to communicate with the development board
12525 through a PC serial port. You must also use the DOS @code{mode} command
12526 to set up the serial port on the DOS side.
12528 The following sample session illustrates the steps needed to start a
12529 program under @value{GDBN} control on an H8/300. The example uses a
12530 sample H8/300 program called @file{t.x}. The procedure is the same for
12531 the Renesas SH and the H8/500.
12533 First hook up your development board. In this example, we use a
12534 board attached to serial port @code{COM2}; if you use a different serial
12535 port, substitute its name in the argument of the @code{mode} command.
12536 When you call @code{asynctsr}, the auxiliary comms program used by the
12537 debugger, you give it just the numeric part of the serial port's name;
12538 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
12542 C:\H8300\TEST> asynctsr 2
12543 C:\H8300\TEST> mode com2:9600,n,8,1,p
12545 Resident portion of MODE loaded
12547 COM2: 9600, n, 8, 1, p
12552 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
12553 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
12554 disable it, or even boot without it, to use @code{asynctsr} to control
12555 your development board.
12558 @kindex target hms@r{, and serial protocol}
12559 Now that serial communications are set up, and the development board is
12560 connected, you can start up @value{GDBN}. Call @code{@value{GDBP}} with
12561 the name of your program as the argument. @code{@value{GDBN}} prompts
12562 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
12563 commands to begin your debugging session: @samp{target hms} to specify
12564 cross-debugging to the Renesas board, and the @code{load} command to
12565 download your program to the board. @code{load} displays the names of
12566 the program's sections, and a @samp{*} for each 2K of data downloaded.
12567 (If you want to refresh @value{GDBN} data on symbols or on the
12568 executable file without downloading, use the @value{GDBN} commands
12569 @code{file} or @code{symbol-file}. These commands, and @code{load}
12570 itself, are described in @ref{Files,,Commands to specify files}.)
12573 (eg-C:\H8300\TEST) @value{GDBP} t.x
12574 @value{GDBN} is free software and you are welcome to distribute copies
12575 of it under certain conditions; type "show copying" to see
12577 There is absolutely no warranty for @value{GDBN}; type "show warranty"
12579 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
12580 (@value{GDBP}) target hms
12581 Connected to remote H8/300 HMS system.
12582 (@value{GDBP}) load t.x
12583 .text : 0x8000 .. 0xabde ***********
12584 .data : 0xabde .. 0xad30 *
12585 .stack : 0xf000 .. 0xf014 *
12588 At this point, you're ready to run or debug your program. From here on,
12589 you can use all the usual @value{GDBN} commands. The @code{break} command
12590 sets breakpoints; the @code{run} command starts your program;
12591 @code{print} or @code{x} display data; the @code{continue} command
12592 resumes execution after stopping at a breakpoint. You can use the
12593 @code{help} command at any time to find out more about @value{GDBN} commands.
12595 Remember, however, that @emph{operating system} facilities aren't
12596 available on your development board; for example, if your program hangs,
12597 you can't send an interrupt---but you can press the @sc{reset} switch!
12599 Use the @sc{reset} button on the development board
12602 to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
12603 no way to pass an interrupt signal to the development board); and
12606 to return to the @value{GDBN} command prompt after your program finishes
12607 normally. The communications protocol provides no other way for @value{GDBN}
12608 to detect program completion.
12611 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
12612 development board as a ``normal exit'' of your program.
12615 @subsubsection Using the E7000 in-circuit emulator
12617 @kindex target e7000@r{, with Renesas ICE}
12618 You can use the E7000 in-circuit emulator to develop code for either the
12619 Renesas SH or the H8/300H. Use one of these forms of the @samp{target
12620 e7000} command to connect @value{GDBN} to your E7000:
12623 @item target e7000 @var{port} @var{speed}
12624 Use this form if your E7000 is connected to a serial port. The
12625 @var{port} argument identifies what serial port to use (for example,
12626 @samp{com2}). The third argument is the line speed in bits per second
12627 (for example, @samp{9600}).
12629 @item target e7000 @var{hostname}
12630 If your E7000 is installed as a host on a TCP/IP network, you can just
12631 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
12634 @node Renesas Special
12635 @subsubsection Special @value{GDBN} commands for Renesas micros
12637 Some @value{GDBN} commands are available only for the H8/300:
12641 @kindex set machine
12642 @kindex show machine
12643 @item set machine h8300
12644 @itemx set machine h8300h
12645 Condition @value{GDBN} for one of the two variants of the H8/300
12646 architecture with @samp{set machine}. You can use @samp{show machine}
12647 to check which variant is currently in effect.
12656 @kindex set memory @var{mod}
12657 @cindex memory models, H8/500
12658 @item set memory @var{mod}
12660 Specify which H8/500 memory model (@var{mod}) you are using with
12661 @samp{set memory}; check which memory model is in effect with @samp{show
12662 memory}. The accepted values for @var{mod} are @code{small},
12663 @code{big}, @code{medium}, and @code{compact}.
12668 @subsection Renesas M32R/D
12672 @kindex target m32r
12673 @item target m32r @var{dev}
12674 Renesas M32R/D ROM monitor.
12676 @kindex target m32rsdi
12677 @item target m32rsdi @var{dev}
12678 Renesas M32R SDI server, connected via parallel port to the board.
12685 The Motorola m68k configuration includes ColdFire support, and
12686 target command for the following ROM monitors.
12690 @kindex target abug
12691 @item target abug @var{dev}
12692 ABug ROM monitor for M68K.
12694 @kindex target cpu32bug
12695 @item target cpu32bug @var{dev}
12696 CPU32BUG monitor, running on a CPU32 (M68K) board.
12698 @kindex target dbug
12699 @item target dbug @var{dev}
12700 dBUG ROM monitor for Motorola ColdFire.
12703 @item target est @var{dev}
12704 EST-300 ICE monitor, running on a CPU32 (M68K) board.
12706 @kindex target rom68k
12707 @item target rom68k @var{dev}
12708 ROM 68K monitor, running on an M68K IDP board.
12714 @kindex target rombug
12715 @item target rombug @var{dev}
12716 ROMBUG ROM monitor for OS/9000.
12720 @node MIPS Embedded
12721 @subsection MIPS Embedded
12723 @cindex MIPS boards
12724 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
12725 MIPS board attached to a serial line. This is available when
12726 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
12729 Use these @value{GDBN} commands to specify the connection to your target board:
12732 @item target mips @var{port}
12733 @kindex target mips @var{port}
12734 To run a program on the board, start up @code{@value{GDBP}} with the
12735 name of your program as the argument. To connect to the board, use the
12736 command @samp{target mips @var{port}}, where @var{port} is the name of
12737 the serial port connected to the board. If the program has not already
12738 been downloaded to the board, you may use the @code{load} command to
12739 download it. You can then use all the usual @value{GDBN} commands.
12741 For example, this sequence connects to the target board through a serial
12742 port, and loads and runs a program called @var{prog} through the
12746 host$ @value{GDBP} @var{prog}
12747 @value{GDBN} is free software and @dots{}
12748 (@value{GDBP}) target mips /dev/ttyb
12749 (@value{GDBP}) load @var{prog}
12753 @item target mips @var{hostname}:@var{portnumber}
12754 On some @value{GDBN} host configurations, you can specify a TCP
12755 connection (for instance, to a serial line managed by a terminal
12756 concentrator) instead of a serial port, using the syntax
12757 @samp{@var{hostname}:@var{portnumber}}.
12759 @item target pmon @var{port}
12760 @kindex target pmon @var{port}
12763 @item target ddb @var{port}
12764 @kindex target ddb @var{port}
12765 NEC's DDB variant of PMON for Vr4300.
12767 @item target lsi @var{port}
12768 @kindex target lsi @var{port}
12769 LSI variant of PMON.
12771 @kindex target r3900
12772 @item target r3900 @var{dev}
12773 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
12775 @kindex target array
12776 @item target array @var{dev}
12777 Array Tech LSI33K RAID controller board.
12783 @value{GDBN} also supports these special commands for MIPS targets:
12786 @item set processor @var{args}
12787 @itemx show processor
12788 @kindex set processor @var{args}
12789 @kindex show processor
12790 Use the @code{set processor} command to set the type of MIPS
12791 processor when you want to access processor-type-specific registers.
12792 For example, @code{set processor @var{r3041}} tells @value{GDBN}
12793 to use the CPU registers appropriate for the 3041 chip.
12794 Use the @code{show processor} command to see what MIPS processor @value{GDBN}
12795 is using. Use the @code{info reg} command to see what registers
12796 @value{GDBN} is using.
12798 @item set mipsfpu double
12799 @itemx set mipsfpu single
12800 @itemx set mipsfpu none
12801 @itemx show mipsfpu
12802 @kindex set mipsfpu
12803 @kindex show mipsfpu
12804 @cindex MIPS remote floating point
12805 @cindex floating point, MIPS remote
12806 If your target board does not support the MIPS floating point
12807 coprocessor, you should use the command @samp{set mipsfpu none} (if you
12808 need this, you may wish to put the command in your @value{GDBN} init
12809 file). This tells @value{GDBN} how to find the return value of
12810 functions which return floating point values. It also allows
12811 @value{GDBN} to avoid saving the floating point registers when calling
12812 functions on the board. If you are using a floating point coprocessor
12813 with only single precision floating point support, as on the @sc{r4650}
12814 processor, use the command @samp{set mipsfpu single}. The default
12815 double precision floating point coprocessor may be selected using
12816 @samp{set mipsfpu double}.
12818 In previous versions the only choices were double precision or no
12819 floating point, so @samp{set mipsfpu on} will select double precision
12820 and @samp{set mipsfpu off} will select no floating point.
12822 As usual, you can inquire about the @code{mipsfpu} variable with
12823 @samp{show mipsfpu}.
12825 @item set remotedebug @var{n}
12826 @itemx show remotedebug
12827 @kindex set remotedebug@r{, MIPS protocol}
12828 @kindex show remotedebug@r{, MIPS protocol}
12829 @cindex @code{remotedebug}, MIPS protocol
12830 @cindex MIPS @code{remotedebug} protocol
12831 @c FIXME! For this to be useful, you must know something about the MIPS
12832 @c FIXME...protocol. Where is it described?
12833 You can see some debugging information about communications with the board
12834 by setting the @code{remotedebug} variable. If you set it to @code{1} using
12835 @samp{set remotedebug 1}, every packet is displayed. If you set it
12836 to @code{2}, every character is displayed. You can check the current value
12837 at any time with the command @samp{show remotedebug}.
12839 @item set timeout @var{seconds}
12840 @itemx set retransmit-timeout @var{seconds}
12841 @itemx show timeout
12842 @itemx show retransmit-timeout
12843 @cindex @code{timeout}, MIPS protocol
12844 @cindex @code{retransmit-timeout}, MIPS protocol
12845 @kindex set timeout
12846 @kindex show timeout
12847 @kindex set retransmit-timeout
12848 @kindex show retransmit-timeout
12849 You can control the timeout used while waiting for a packet, in the MIPS
12850 remote protocol, with the @code{set timeout @var{seconds}} command. The
12851 default is 5 seconds. Similarly, you can control the timeout used while
12852 waiting for an acknowledgement of a packet with the @code{set
12853 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
12854 You can inspect both values with @code{show timeout} and @code{show
12855 retransmit-timeout}. (These commands are @emph{only} available when
12856 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
12858 The timeout set by @code{set timeout} does not apply when @value{GDBN}
12859 is waiting for your program to stop. In that case, @value{GDBN} waits
12860 forever because it has no way of knowing how long the program is going
12861 to run before stopping.
12864 @node OpenRISC 1000
12865 @subsection OpenRISC 1000
12866 @cindex OpenRISC 1000
12868 @cindex or1k boards
12869 See OR1k Architecture document (@uref{www.opencores.org}) for more information
12870 about platform and commands.
12874 @kindex target jtag
12875 @item target jtag jtag://@var{host}:@var{port}
12877 Connects to remote JTAG server.
12878 JTAG remote server can be either an or1ksim or JTAG server,
12879 connected via parallel port to the board.
12881 Example: @code{target jtag jtag://localhost:9999}
12884 @item or1ksim @var{command}
12885 If connected to @code{or1ksim} OpenRISC 1000 Architectural
12886 Simulator, proprietary commands can be executed.
12888 @kindex info or1k spr
12889 @item info or1k spr
12890 Displays spr groups.
12892 @item info or1k spr @var{group}
12893 @itemx info or1k spr @var{groupno}
12894 Displays register names in selected group.
12896 @item info or1k spr @var{group} @var{register}
12897 @itemx info or1k spr @var{register}
12898 @itemx info or1k spr @var{groupno} @var{registerno}
12899 @itemx info or1k spr @var{registerno}
12900 Shows information about specified spr register.
12903 @item spr @var{group} @var{register} @var{value}
12904 @itemx spr @var{register @var{value}}
12905 @itemx spr @var{groupno} @var{registerno @var{value}}
12906 @itemx spr @var{registerno @var{value}}
12907 Writes @var{value} to specified spr register.
12910 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
12911 It is very similar to @value{GDBN} trace, except it does not interfere with normal
12912 program execution and is thus much faster. Hardware breakpoints/watchpoint
12913 triggers can be set using:
12916 Load effective address/data
12918 Store effective address/data
12920 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
12925 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
12926 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
12928 @code{htrace} commands:
12929 @cindex OpenRISC 1000 htrace
12932 @item hwatch @var{conditional}
12933 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
12934 or Data. For example:
12936 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
12938 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
12942 Display information about current HW trace configuration.
12944 @item htrace trigger @var{conditional}
12945 Set starting criteria for HW trace.
12947 @item htrace qualifier @var{conditional}
12948 Set acquisition qualifier for HW trace.
12950 @item htrace stop @var{conditional}
12951 Set HW trace stopping criteria.
12953 @item htrace record [@var{data}]*
12954 Selects the data to be recorded, when qualifier is met and HW trace was
12957 @item htrace enable
12958 @itemx htrace disable
12959 Enables/disables the HW trace.
12961 @item htrace rewind [@var{filename}]
12962 Clears currently recorded trace data.
12964 If filename is specified, new trace file is made and any newly collected data
12965 will be written there.
12967 @item htrace print [@var{start} [@var{len}]]
12968 Prints trace buffer, using current record configuration.
12970 @item htrace mode continuous
12971 Set continuous trace mode.
12973 @item htrace mode suspend
12974 Set suspend trace mode.
12979 @subsection PowerPC
12983 @kindex target dink32
12984 @item target dink32 @var{dev}
12985 DINK32 ROM monitor.
12987 @kindex target ppcbug
12988 @item target ppcbug @var{dev}
12989 @kindex target ppcbug1
12990 @item target ppcbug1 @var{dev}
12991 PPCBUG ROM monitor for PowerPC.
12994 @item target sds @var{dev}
12995 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
13000 @subsection HP PA Embedded
13004 @kindex target op50n
13005 @item target op50n @var{dev}
13006 OP50N monitor, running on an OKI HPPA board.
13008 @kindex target w89k
13009 @item target w89k @var{dev}
13010 W89K monitor, running on a Winbond HPPA board.
13015 @subsection Renesas SH
13019 @kindex target hms@r{, with Renesas SH}
13020 @item target hms @var{dev}
13021 A Renesas SH board attached via serial line to your host. Use special
13022 commands @code{device} and @code{speed} to control the serial line and
13023 the communications speed used.
13025 @kindex target e7000@r{, with Renesas SH}
13026 @item target e7000 @var{dev}
13027 E7000 emulator for Renesas SH.
13029 @kindex target sh3@r{, with SH}
13030 @kindex target sh3e@r{, with SH}
13031 @item target sh3 @var{dev}
13032 @item target sh3e @var{dev}
13033 Renesas SH-3 and SH-3E target systems.
13038 @subsection Tsqware Sparclet
13042 @value{GDBN} enables developers to debug tasks running on
13043 Sparclet targets from a Unix host.
13044 @value{GDBN} uses code that runs on
13045 both the Unix host and on the Sparclet target. The program
13046 @code{@value{GDBP}} is installed and executed on the Unix host.
13049 @item remotetimeout @var{args}
13050 @kindex remotetimeout
13051 @value{GDBN} supports the option @code{remotetimeout}.
13052 This option is set by the user, and @var{args} represents the number of
13053 seconds @value{GDBN} waits for responses.
13056 @cindex compiling, on Sparclet
13057 When compiling for debugging, include the options @samp{-g} to get debug
13058 information and @samp{-Ttext} to relocate the program to where you wish to
13059 load it on the target. You may also want to add the options @samp{-n} or
13060 @samp{-N} in order to reduce the size of the sections. Example:
13063 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
13066 You can use @code{objdump} to verify that the addresses are what you intended:
13069 sparclet-aout-objdump --headers --syms prog
13072 @cindex running, on Sparclet
13074 your Unix execution search path to find @value{GDBN}, you are ready to
13075 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
13076 (or @code{sparclet-aout-gdb}, depending on your installation).
13078 @value{GDBN} comes up showing the prompt:
13085 * Sparclet File:: Setting the file to debug
13086 * Sparclet Connection:: Connecting to Sparclet
13087 * Sparclet Download:: Sparclet download
13088 * Sparclet Execution:: Running and debugging
13091 @node Sparclet File
13092 @subsubsection Setting file to debug
13094 The @value{GDBN} command @code{file} lets you choose with program to debug.
13097 (gdbslet) file prog
13101 @value{GDBN} then attempts to read the symbol table of @file{prog}.
13102 @value{GDBN} locates
13103 the file by searching the directories listed in the command search
13105 If the file was compiled with debug information (option "-g"), source
13106 files will be searched as well.
13107 @value{GDBN} locates
13108 the source files by searching the directories listed in the directory search
13109 path (@pxref{Environment, ,Your program's environment}).
13111 to find a file, it displays a message such as:
13114 prog: No such file or directory.
13117 When this happens, add the appropriate directories to the search paths with
13118 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
13119 @code{target} command again.
13121 @node Sparclet Connection
13122 @subsubsection Connecting to Sparclet
13124 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
13125 To connect to a target on serial port ``@code{ttya}'', type:
13128 (gdbslet) target sparclet /dev/ttya
13129 Remote target sparclet connected to /dev/ttya
13130 main () at ../prog.c:3
13134 @value{GDBN} displays messages like these:
13140 @node Sparclet Download
13141 @subsubsection Sparclet download
13143 @cindex download to Sparclet
13144 Once connected to the Sparclet target,
13145 you can use the @value{GDBN}
13146 @code{load} command to download the file from the host to the target.
13147 The file name and load offset should be given as arguments to the @code{load}
13149 Since the file format is aout, the program must be loaded to the starting
13150 address. You can use @code{objdump} to find out what this value is. The load
13151 offset is an offset which is added to the VMA (virtual memory address)
13152 of each of the file's sections.
13153 For instance, if the program
13154 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
13155 and bss at 0x12010170, in @value{GDBN}, type:
13158 (gdbslet) load prog 0x12010000
13159 Loading section .text, size 0xdb0 vma 0x12010000
13162 If the code is loaded at a different address then what the program was linked
13163 to, you may need to use the @code{section} and @code{add-symbol-file} commands
13164 to tell @value{GDBN} where to map the symbol table.
13166 @node Sparclet Execution
13167 @subsubsection Running and debugging
13169 @cindex running and debugging Sparclet programs
13170 You can now begin debugging the task using @value{GDBN}'s execution control
13171 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
13172 manual for the list of commands.
13176 Breakpoint 1 at 0x12010000: file prog.c, line 3.
13178 Starting program: prog
13179 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
13180 3 char *symarg = 0;
13182 4 char *execarg = "hello!";
13187 @subsection Fujitsu Sparclite
13191 @kindex target sparclite
13192 @item target sparclite @var{dev}
13193 Fujitsu sparclite boards, used only for the purpose of loading.
13194 You must use an additional command to debug the program.
13195 For example: target remote @var{dev} using @value{GDBN} standard
13201 @subsection Tandem ST2000
13203 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
13206 To connect your ST2000 to the host system, see the manufacturer's
13207 manual. Once the ST2000 is physically attached, you can run:
13210 target st2000 @var{dev} @var{speed}
13214 to establish it as your debugging environment. @var{dev} is normally
13215 the name of a serial device, such as @file{/dev/ttya}, connected to the
13216 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
13217 connection (for example, to a serial line attached via a terminal
13218 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
13220 The @code{load} and @code{attach} commands are @emph{not} defined for
13221 this target; you must load your program into the ST2000 as you normally
13222 would for standalone operation. @value{GDBN} reads debugging information
13223 (such as symbols) from a separate, debugging version of the program
13224 available on your host computer.
13225 @c FIXME!! This is terribly vague; what little content is here is
13226 @c basically hearsay.
13228 @cindex ST2000 auxiliary commands
13229 These auxiliary @value{GDBN} commands are available to help you with the ST2000
13233 @item st2000 @var{command}
13234 @kindex st2000 @var{cmd}
13235 @cindex STDBUG commands (ST2000)
13236 @cindex commands to STDBUG (ST2000)
13237 Send a @var{command} to the STDBUG monitor. See the manufacturer's
13238 manual for available commands.
13241 @cindex connect (to STDBUG)
13242 Connect the controlling terminal to the STDBUG command monitor. When
13243 you are done interacting with STDBUG, typing either of two character
13244 sequences gets you back to the @value{GDBN} command prompt:
13245 @kbd{@key{RET}~.} (Return, followed by tilde and period) or
13246 @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
13250 @subsection Zilog Z8000
13253 @cindex simulator, Z8000
13254 @cindex Zilog Z8000 simulator
13256 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
13259 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
13260 unsegmented variant of the Z8000 architecture) or the Z8001 (the
13261 segmented variant). The simulator recognizes which architecture is
13262 appropriate by inspecting the object code.
13265 @item target sim @var{args}
13267 @kindex target sim@r{, with Z8000}
13268 Debug programs on a simulated CPU. If the simulator supports setup
13269 options, specify them via @var{args}.
13273 After specifying this target, you can debug programs for the simulated
13274 CPU in the same style as programs for your host computer; use the
13275 @code{file} command to load a new program image, the @code{run} command
13276 to run your program, and so on.
13278 As well as making available all the usual machine registers
13279 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
13280 additional items of information as specially named registers:
13285 Counts clock-ticks in the simulator.
13288 Counts instructions run in the simulator.
13291 Execution time in 60ths of a second.
13295 You can refer to these values in @value{GDBN} expressions with the usual
13296 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
13297 conditional breakpoint that suspends only after at least 5000
13298 simulated clock ticks.
13300 @node Architectures
13301 @section Architectures
13303 This section describes characteristics of architectures that affect
13304 all uses of @value{GDBN} with the architecture, both native and cross.
13317 @kindex set rstack_high_address
13318 @cindex AMD 29K register stack
13319 @cindex register stack, AMD29K
13320 @item set rstack_high_address @var{address}
13321 On AMD 29000 family processors, registers are saved in a separate
13322 @dfn{register stack}. There is no way for @value{GDBN} to determine the
13323 extent of this stack. Normally, @value{GDBN} just assumes that the
13324 stack is ``large enough''. This may result in @value{GDBN} referencing
13325 memory locations that do not exist. If necessary, you can get around
13326 this problem by specifying the ending address of the register stack with
13327 the @code{set rstack_high_address} command. The argument should be an
13328 address, which you probably want to precede with @samp{0x} to specify in
13331 @kindex show rstack_high_address
13332 @item show rstack_high_address
13333 Display the current limit of the register stack, on AMD 29000 family
13341 See the following section.
13346 @cindex stack on Alpha
13347 @cindex stack on MIPS
13348 @cindex Alpha stack
13350 Alpha- and MIPS-based computers use an unusual stack frame, which
13351 sometimes requires @value{GDBN} to search backward in the object code to
13352 find the beginning of a function.
13354 @cindex response time, MIPS debugging
13355 To improve response time (especially for embedded applications, where
13356 @value{GDBN} may be restricted to a slow serial line for this search)
13357 you may want to limit the size of this search, using one of these
13361 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
13362 @item set heuristic-fence-post @var{limit}
13363 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
13364 search for the beginning of a function. A value of @var{0} (the
13365 default) means there is no limit. However, except for @var{0}, the
13366 larger the limit the more bytes @code{heuristic-fence-post} must search
13367 and therefore the longer it takes to run.
13369 @item show heuristic-fence-post
13370 Display the current limit.
13374 These commands are available @emph{only} when @value{GDBN} is configured
13375 for debugging programs on Alpha or MIPS processors.
13378 @node Controlling GDB
13379 @chapter Controlling @value{GDBN}
13381 You can alter the way @value{GDBN} interacts with you by using the
13382 @code{set} command. For commands controlling how @value{GDBN} displays
13383 data, see @ref{Print Settings, ,Print settings}. Other settings are
13388 * Editing:: Command editing
13389 * History:: Command history
13390 * Screen Size:: Screen size
13391 * Numbers:: Numbers
13392 * ABI:: Configuring the current ABI
13393 * Messages/Warnings:: Optional warnings and messages
13394 * Debugging Output:: Optional messages about internal happenings
13402 @value{GDBN} indicates its readiness to read a command by printing a string
13403 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
13404 can change the prompt string with the @code{set prompt} command. For
13405 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
13406 the prompt in one of the @value{GDBN} sessions so that you can always tell
13407 which one you are talking to.
13409 @emph{Note:} @code{set prompt} does not add a space for you after the
13410 prompt you set. This allows you to set a prompt which ends in a space
13411 or a prompt that does not.
13415 @item set prompt @var{newprompt}
13416 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
13418 @kindex show prompt
13420 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
13424 @section Command editing
13426 @cindex command line editing
13428 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
13429 @sc{gnu} library provides consistent behavior for programs which provide a
13430 command line interface to the user. Advantages are @sc{gnu} Emacs-style
13431 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
13432 substitution, and a storage and recall of command history across
13433 debugging sessions.
13435 You may control the behavior of command line editing in @value{GDBN} with the
13436 command @code{set}.
13439 @kindex set editing
13442 @itemx set editing on
13443 Enable command line editing (enabled by default).
13445 @item set editing off
13446 Disable command line editing.
13448 @kindex show editing
13450 Show whether command line editing is enabled.
13453 @xref{Command Line Editing}, for more details about the Readline
13454 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
13455 encouraged to read that chapter.
13458 @section Command history
13459 @cindex command history
13461 @value{GDBN} can keep track of the commands you type during your
13462 debugging sessions, so that you can be certain of precisely what
13463 happened. Use these commands to manage the @value{GDBN} command
13466 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
13467 package, to provide the history facility. @xref{Using History
13468 Interactively}, for the detailed description of the History library.
13470 Here is the description of @value{GDBN} commands related to command
13474 @cindex history substitution
13475 @cindex history file
13476 @kindex set history filename
13477 @cindex @env{GDBHISTFILE}, environment variable
13478 @item set history filename @var{fname}
13479 Set the name of the @value{GDBN} command history file to @var{fname}.
13480 This is the file where @value{GDBN} reads an initial command history
13481 list, and where it writes the command history from this session when it
13482 exits. You can access this list through history expansion or through
13483 the history command editing characters listed below. This file defaults
13484 to the value of the environment variable @code{GDBHISTFILE}, or to
13485 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
13488 @cindex history save
13489 @kindex set history
13490 @item set history save
13491 @itemx set history save on
13492 Record command history in a file, whose name may be specified with the
13493 @code{set history filename} command. By default, this option is disabled.
13495 @item set history save off
13496 Stop recording command history in a file.
13498 @cindex history size
13499 @item set history size @var{size}
13500 Set the number of commands which @value{GDBN} keeps in its history list.
13501 This defaults to the value of the environment variable
13502 @code{HISTSIZE}, or to 256 if this variable is not set.
13505 History expansion assigns special meaning to the character @kbd{!}.
13506 @xref{Event Designators}, for more details.
13508 @cindex history expansion, turn on/off
13509 Since @kbd{!} is also the logical not operator in C, history expansion
13510 is off by default. If you decide to enable history expansion with the
13511 @code{set history expansion on} command, you may sometimes need to
13512 follow @kbd{!} (when it is used as logical not, in an expression) with
13513 a space or a tab to prevent it from being expanded. The readline
13514 history facilities do not attempt substitution on the strings
13515 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
13517 The commands to control history expansion are:
13520 @item set history expansion on
13521 @itemx set history expansion
13522 @kindex set history expansion
13523 Enable history expansion. History expansion is off by default.
13525 @item set history expansion off
13526 Disable history expansion.
13529 @kindex show history
13531 @itemx show history filename
13532 @itemx show history save
13533 @itemx show history size
13534 @itemx show history expansion
13535 These commands display the state of the @value{GDBN} history parameters.
13536 @code{show history} by itself displays all four states.
13542 @item show commands
13543 Display the last ten commands in the command history.
13545 @item show commands @var{n}
13546 Print ten commands centered on command number @var{n}.
13548 @item show commands +
13549 Print ten commands just after the commands last printed.
13553 @section Screen size
13554 @cindex size of screen
13555 @cindex pauses in output
13557 Certain commands to @value{GDBN} may produce large amounts of
13558 information output to the screen. To help you read all of it,
13559 @value{GDBN} pauses and asks you for input at the end of each page of
13560 output. Type @key{RET} when you want to continue the output, or @kbd{q}
13561 to discard the remaining output. Also, the screen width setting
13562 determines when to wrap lines of output. Depending on what is being
13563 printed, @value{GDBN} tries to break the line at a readable place,
13564 rather than simply letting it overflow onto the following line.
13566 Normally @value{GDBN} knows the size of the screen from the terminal
13567 driver software. For example, on Unix @value{GDBN} uses the termcap data base
13568 together with the value of the @code{TERM} environment variable and the
13569 @code{stty rows} and @code{stty cols} settings. If this is not correct,
13570 you can override it with the @code{set height} and @code{set
13577 @kindex show height
13578 @item set height @var{lpp}
13580 @itemx set width @var{cpl}
13582 These @code{set} commands specify a screen height of @var{lpp} lines and
13583 a screen width of @var{cpl} characters. The associated @code{show}
13584 commands display the current settings.
13586 If you specify a height of zero lines, @value{GDBN} does not pause during
13587 output no matter how long the output is. This is useful if output is to a
13588 file or to an editor buffer.
13590 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
13591 from wrapping its output.
13596 @cindex number representation
13597 @cindex entering numbers
13599 You can always enter numbers in octal, decimal, or hexadecimal in
13600 @value{GDBN} by the usual conventions: octal numbers begin with
13601 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
13602 begin with @samp{0x}. Numbers that begin with none of these are, by
13603 default, entered in base 10; likewise, the default display for
13604 numbers---when no particular format is specified---is base 10. You can
13605 change the default base for both input and output with the @code{set
13609 @kindex set input-radix
13610 @item set input-radix @var{base}
13611 Set the default base for numeric input. Supported choices
13612 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
13613 specified either unambiguously or using the current default radix; for
13623 sets the base to decimal. On the other hand, @samp{set radix 10}
13624 leaves the radix unchanged no matter what it was.
13626 @kindex set output-radix
13627 @item set output-radix @var{base}
13628 Set the default base for numeric display. Supported choices
13629 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
13630 specified either unambiguously or using the current default radix.
13632 @kindex show input-radix
13633 @item show input-radix
13634 Display the current default base for numeric input.
13636 @kindex show output-radix
13637 @item show output-radix
13638 Display the current default base for numeric display.
13642 @section Configuring the current ABI
13644 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
13645 application automatically. However, sometimes you need to override its
13646 conclusions. Use these commands to manage @value{GDBN}'s view of the
13653 One @value{GDBN} configuration can debug binaries for multiple operating
13654 system targets, either via remote debugging or native emulation.
13655 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
13656 but you can override its conclusion using the @code{set osabi} command.
13657 One example where this is useful is in debugging of binaries which use
13658 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
13659 not have the same identifying marks that the standard C library for your
13664 Show the OS ABI currently in use.
13667 With no argument, show the list of registered available OS ABI's.
13669 @item set osabi @var{abi}
13670 Set the current OS ABI to @var{abi}.
13673 @cindex float promotion
13674 @kindex set coerce-float-to-double
13676 Generally, the way that an argument of type @code{float} is passed to a
13677 function depends on whether the function is prototyped. For a prototyped
13678 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
13679 according to the architecture's convention for @code{float}. For unprototyped
13680 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
13681 @code{double} and then passed.
13683 Unfortunately, some forms of debug information do not reliably indicate whether
13684 a function is prototyped. If @value{GDBN} calls a function that is not marked
13685 as prototyped, it consults @kbd{set coerce-float-to-double}.
13688 @item set coerce-float-to-double
13689 @itemx set coerce-float-to-double on
13690 Arguments of type @code{float} will be promoted to @code{double} when passed
13691 to an unprototyped function. This is the default setting.
13693 @item set coerce-float-to-double off
13694 Arguments of type @code{float} will be passed directly to unprototyped
13699 @kindex show cp-abi
13700 @value{GDBN} needs to know the ABI used for your program's C@t{++}
13701 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
13702 used to build your application. @value{GDBN} only fully supports
13703 programs with a single C@t{++} ABI; if your program contains code using
13704 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
13705 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
13706 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
13707 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
13708 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
13709 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
13714 Show the C@t{++} ABI currently in use.
13717 With no argument, show the list of supported C@t{++} ABI's.
13719 @item set cp-abi @var{abi}
13720 @itemx set cp-abi auto
13721 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
13724 @node Messages/Warnings
13725 @section Optional warnings and messages
13727 By default, @value{GDBN} is silent about its inner workings. If you are
13728 running on a slow machine, you may want to use the @code{set verbose}
13729 command. This makes @value{GDBN} tell you when it does a lengthy
13730 internal operation, so you will not think it has crashed.
13732 Currently, the messages controlled by @code{set verbose} are those
13733 which announce that the symbol table for a source file is being read;
13734 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
13737 @kindex set verbose
13738 @item set verbose on
13739 Enables @value{GDBN} output of certain informational messages.
13741 @item set verbose off
13742 Disables @value{GDBN} output of certain informational messages.
13744 @kindex show verbose
13746 Displays whether @code{set verbose} is on or off.
13749 By default, if @value{GDBN} encounters bugs in the symbol table of an
13750 object file, it is silent; but if you are debugging a compiler, you may
13751 find this information useful (@pxref{Symbol Errors, ,Errors reading
13756 @kindex set complaints
13757 @item set complaints @var{limit}
13758 Permits @value{GDBN} to output @var{limit} complaints about each type of
13759 unusual symbols before becoming silent about the problem. Set
13760 @var{limit} to zero to suppress all complaints; set it to a large number
13761 to prevent complaints from being suppressed.
13763 @kindex show complaints
13764 @item show complaints
13765 Displays how many symbol complaints @value{GDBN} is permitted to produce.
13769 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
13770 lot of stupid questions to confirm certain commands. For example, if
13771 you try to run a program which is already running:
13775 The program being debugged has been started already.
13776 Start it from the beginning? (y or n)
13779 If you are willing to unflinchingly face the consequences of your own
13780 commands, you can disable this ``feature'':
13784 @kindex set confirm
13786 @cindex confirmation
13787 @cindex stupid questions
13788 @item set confirm off
13789 Disables confirmation requests.
13791 @item set confirm on
13792 Enables confirmation requests (the default).
13794 @kindex show confirm
13796 Displays state of confirmation requests.
13800 @node Debugging Output
13801 @section Optional messages about internal happenings
13802 @cindex optional debugging messages
13806 @cindex gdbarch debugging info
13807 @item set debug arch
13808 Turns on or off display of gdbarch debugging info. The default is off
13810 @item show debug arch
13811 Displays the current state of displaying gdbarch debugging info.
13812 @item set debug event
13813 @cindex event debugging info
13814 Turns on or off display of @value{GDBN} event debugging info. The
13816 @item show debug event
13817 Displays the current state of displaying @value{GDBN} event debugging
13819 @item set debug expression
13820 @cindex expression debugging info
13821 Turns on or off display of @value{GDBN} expression debugging info. The
13823 @item show debug expression
13824 Displays the current state of displaying @value{GDBN} expression
13826 @item set debug frame
13827 @cindex frame debugging info
13828 Turns on or off display of @value{GDBN} frame debugging info. The
13830 @item show debug frame
13831 Displays the current state of displaying @value{GDBN} frame debugging
13833 @item set debug observer
13834 @cindex observer debugging info
13835 Turns on or off display of @value{GDBN} observer debugging. This
13836 includes info such as the notification of observable events.
13837 @item show debug observer
13838 Displays the current state of observer debugging.
13839 @item set debug overload
13840 @cindex C@t{++} overload debugging info
13841 Turns on or off display of @value{GDBN} C@t{++} overload debugging
13842 info. This includes info such as ranking of functions, etc. The default
13844 @item show debug overload
13845 Displays the current state of displaying @value{GDBN} C@t{++} overload
13847 @cindex packets, reporting on stdout
13848 @cindex serial connections, debugging
13849 @item set debug remote
13850 Turns on or off display of reports on all packets sent back and forth across
13851 the serial line to the remote machine. The info is printed on the
13852 @value{GDBN} standard output stream. The default is off.
13853 @item show debug remote
13854 Displays the state of display of remote packets.
13855 @item set debug serial
13856 Turns on or off display of @value{GDBN} serial debugging info. The
13858 @item show debug serial
13859 Displays the current state of displaying @value{GDBN} serial debugging
13861 @item set debug target
13862 @cindex target debugging info
13863 Turns on or off display of @value{GDBN} target debugging info. This info
13864 includes what is going on at the target level of GDB, as it happens. The
13865 default is 0. Set it to 1 to track events, and to 2 to also track the
13866 value of large memory transfers. Changes to this flag do not take effect
13867 until the next time you connect to a target or use the @code{run} command.
13868 @item show debug target
13869 Displays the current state of displaying @value{GDBN} target debugging
13871 @item set debug varobj
13872 @cindex variable object debugging info
13873 Turns on or off display of @value{GDBN} variable object debugging
13874 info. The default is off.
13875 @item show debug varobj
13876 Displays the current state of displaying @value{GDBN} variable object
13881 @chapter Canned Sequences of Commands
13883 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
13884 command lists}), @value{GDBN} provides two ways to store sequences of
13885 commands for execution as a unit: user-defined commands and command
13889 * Define:: User-defined commands
13890 * Hooks:: User-defined command hooks
13891 * Command Files:: Command files
13892 * Output:: Commands for controlled output
13896 @section User-defined commands
13898 @cindex user-defined command
13899 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
13900 which you assign a new name as a command. This is done with the
13901 @code{define} command. User commands may accept up to 10 arguments
13902 separated by whitespace. Arguments are accessed within the user command
13903 via @var{$arg0@dots{}$arg9}. A trivial example:
13907 print $arg0 + $arg1 + $arg2
13911 To execute the command use:
13918 This defines the command @code{adder}, which prints the sum of
13919 its three arguments. Note the arguments are text substitutions, so they may
13920 reference variables, use complex expressions, or even perform inferior
13926 @item define @var{commandname}
13927 Define a command named @var{commandname}. If there is already a command
13928 by that name, you are asked to confirm that you want to redefine it.
13930 The definition of the command is made up of other @value{GDBN} command lines,
13931 which are given following the @code{define} command. The end of these
13932 commands is marked by a line containing @code{end}.
13937 Takes a single argument, which is an expression to evaluate.
13938 It is followed by a series of commands that are executed
13939 only if the expression is true (nonzero).
13940 There can then optionally be a line @code{else}, followed
13941 by a series of commands that are only executed if the expression
13942 was false. The end of the list is marked by a line containing @code{end}.
13946 The syntax is similar to @code{if}: the command takes a single argument,
13947 which is an expression to evaluate, and must be followed by the commands to
13948 execute, one per line, terminated by an @code{end}.
13949 The commands are executed repeatedly as long as the expression
13953 @item document @var{commandname}
13954 Document the user-defined command @var{commandname}, so that it can be
13955 accessed by @code{help}. The command @var{commandname} must already be
13956 defined. This command reads lines of documentation just as @code{define}
13957 reads the lines of the command definition, ending with @code{end}.
13958 After the @code{document} command is finished, @code{help} on command
13959 @var{commandname} displays the documentation you have written.
13961 You may use the @code{document} command again to change the
13962 documentation of a command. Redefining the command with @code{define}
13963 does not change the documentation.
13965 @kindex help user-defined
13966 @item help user-defined
13967 List all user-defined commands, with the first line of the documentation
13972 @itemx show user @var{commandname}
13973 Display the @value{GDBN} commands used to define @var{commandname} (but
13974 not its documentation). If no @var{commandname} is given, display the
13975 definitions for all user-defined commands.
13977 @kindex show max-user-call-depth
13978 @kindex set max-user-call-depth
13979 @item show max-user-call-depth
13980 @itemx set max-user-call-depth
13981 The value of @code{max-user-call-depth} controls how many recursion
13982 levels are allowed in user-defined commands before GDB suspects an
13983 infinite recursion and aborts the command.
13987 When user-defined commands are executed, the
13988 commands of the definition are not printed. An error in any command
13989 stops execution of the user-defined command.
13991 If used interactively, commands that would ask for confirmation proceed
13992 without asking when used inside a user-defined command. Many @value{GDBN}
13993 commands that normally print messages to say what they are doing omit the
13994 messages when used in a user-defined command.
13997 @section User-defined command hooks
13998 @cindex command hooks
13999 @cindex hooks, for commands
14000 @cindex hooks, pre-command
14003 You may define @dfn{hooks}, which are a special kind of user-defined
14004 command. Whenever you run the command @samp{foo}, if the user-defined
14005 command @samp{hook-foo} exists, it is executed (with no arguments)
14006 before that command.
14008 @cindex hooks, post-command
14010 A hook may also be defined which is run after the command you executed.
14011 Whenever you run the command @samp{foo}, if the user-defined command
14012 @samp{hookpost-foo} exists, it is executed (with no arguments) after
14013 that command. Post-execution hooks may exist simultaneously with
14014 pre-execution hooks, for the same command.
14016 It is valid for a hook to call the command which it hooks. If this
14017 occurs, the hook is not re-executed, thereby avoiding infinte recursion.
14019 @c It would be nice if hookpost could be passed a parameter indicating
14020 @c if the command it hooks executed properly or not. FIXME!
14022 @kindex stop@r{, a pseudo-command}
14023 In addition, a pseudo-command, @samp{stop} exists. Defining
14024 (@samp{hook-stop}) makes the associated commands execute every time
14025 execution stops in your program: before breakpoint commands are run,
14026 displays are printed, or the stack frame is printed.
14028 For example, to ignore @code{SIGALRM} signals while
14029 single-stepping, but treat them normally during normal execution,
14034 handle SIGALRM nopass
14038 handle SIGALRM pass
14041 define hook-continue
14042 handle SIGLARM pass
14046 As a further example, to hook at the begining and end of the @code{echo}
14047 command, and to add extra text to the beginning and end of the message,
14055 define hookpost-echo
14059 (@value{GDBP}) echo Hello World
14060 <<<---Hello World--->>>
14065 You can define a hook for any single-word command in @value{GDBN}, but
14066 not for command aliases; you should define a hook for the basic command
14067 name, e.g. @code{backtrace} rather than @code{bt}.
14068 @c FIXME! So how does Joe User discover whether a command is an alias
14070 If an error occurs during the execution of your hook, execution of
14071 @value{GDBN} commands stops and @value{GDBN} issues a prompt
14072 (before the command that you actually typed had a chance to run).
14074 If you try to define a hook which does not match any known command, you
14075 get a warning from the @code{define} command.
14077 @node Command Files
14078 @section Command files
14080 @cindex command files
14081 A command file for @value{GDBN} is a file of lines that are @value{GDBN}
14082 commands. Comments (lines starting with @kbd{#}) may also be included.
14083 An empty line in a command file does nothing; it does not mean to repeat
14084 the last command, as it would from the terminal.
14087 @cindex @file{.gdbinit}
14088 @cindex @file{gdb.ini}
14089 When you start @value{GDBN}, it automatically executes commands from its
14090 @dfn{init files}, normally called @file{.gdbinit}@footnote{The DJGPP
14091 port of @value{GDBN} uses the name @file{gdb.ini} instead, due to the
14092 limitations of file names imposed by DOS filesystems.}.
14093 During startup, @value{GDBN} does the following:
14097 Reads the init file (if any) in your home directory@footnote{On
14098 DOS/Windows systems, the home directory is the one pointed to by the
14099 @code{HOME} environment variable.}.
14102 Processes command line options and operands.
14105 Reads the init file (if any) in the current working directory.
14108 Reads command files specified by the @samp{-x} option.
14111 The init file in your home directory can set options (such as @samp{set
14112 complaints}) that affect subsequent processing of command line options
14113 and operands. Init files are not executed if you use the @samp{-nx}
14114 option (@pxref{Mode Options, ,Choosing modes}).
14116 @cindex init file name
14117 On some configurations of @value{GDBN}, the init file is known by a
14118 different name (these are typically environments where a specialized
14119 form of @value{GDBN} may need to coexist with other forms, hence a
14120 different name for the specialized version's init file). These are the
14121 environments with special init file names:
14123 @cindex @file{.vxgdbinit}
14126 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
14128 @cindex @file{.os68gdbinit}
14130 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
14132 @cindex @file{.esgdbinit}
14134 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
14137 You can also request the execution of a command file with the
14138 @code{source} command:
14142 @item source @var{filename}
14143 Execute the command file @var{filename}.
14146 The lines in a command file are executed sequentially. They are not
14147 printed as they are executed. An error in any command terminates
14148 execution of the command file and control is returned to the console.
14150 Commands that would ask for confirmation if used interactively proceed
14151 without asking when used in a command file. Many @value{GDBN} commands that
14152 normally print messages to say what they are doing omit the messages
14153 when called from command files.
14155 @value{GDBN} also accepts command input from standard input. In this
14156 mode, normal output goes to standard output and error output goes to
14157 standard error. Errors in a command file supplied on standard input do
14158 not terminate execution of the command file --- execution continues with
14162 gdb < cmds > log 2>&1
14165 (The syntax above will vary depending on the shell used.) This example
14166 will execute commands from the file @file{cmds}. All output and errors
14167 would be directed to @file{log}.
14170 @section Commands for controlled output
14172 During the execution of a command file or a user-defined command, normal
14173 @value{GDBN} output is suppressed; the only output that appears is what is
14174 explicitly printed by the commands in the definition. This section
14175 describes three commands useful for generating exactly the output you
14180 @item echo @var{text}
14181 @c I do not consider backslash-space a standard C escape sequence
14182 @c because it is not in ANSI.
14183 Print @var{text}. Nonprinting characters can be included in
14184 @var{text} using C escape sequences, such as @samp{\n} to print a
14185 newline. @strong{No newline is printed unless you specify one.}
14186 In addition to the standard C escape sequences, a backslash followed
14187 by a space stands for a space. This is useful for displaying a
14188 string with spaces at the beginning or the end, since leading and
14189 trailing spaces are otherwise trimmed from all arguments.
14190 To print @samp{@w{ }and foo =@w{ }}, use the command
14191 @samp{echo \@w{ }and foo = \@w{ }}.
14193 A backslash at the end of @var{text} can be used, as in C, to continue
14194 the command onto subsequent lines. For example,
14197 echo This is some text\n\
14198 which is continued\n\
14199 onto several lines.\n
14202 produces the same output as
14205 echo This is some text\n
14206 echo which is continued\n
14207 echo onto several lines.\n
14211 @item output @var{expression}
14212 Print the value of @var{expression} and nothing but that value: no
14213 newlines, no @samp{$@var{nn} = }. The value is not entered in the
14214 value history either. @xref{Expressions, ,Expressions}, for more information
14217 @item output/@var{fmt} @var{expression}
14218 Print the value of @var{expression} in format @var{fmt}. You can use
14219 the same formats as for @code{print}. @xref{Output Formats,,Output
14220 formats}, for more information.
14223 @item printf @var{string}, @var{expressions}@dots{}
14224 Print the values of the @var{expressions} under the control of
14225 @var{string}. The @var{expressions} are separated by commas and may be
14226 either numbers or pointers. Their values are printed as specified by
14227 @var{string}, exactly as if your program were to execute the C
14229 @c FIXME: the above implies that at least all ANSI C formats are
14230 @c supported, but it isn't true: %E and %G don't work (or so it seems).
14231 @c Either this is a bug, or the manual should document what formats are
14235 printf (@var{string}, @var{expressions}@dots{});
14238 For example, you can print two values in hex like this:
14241 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
14244 The only backslash-escape sequences that you can use in the format
14245 string are the simple ones that consist of backslash followed by a
14250 @chapter Command Interpreters
14251 @cindex command interpreters
14253 @value{GDBN} supports multiple command interpreters, and some command
14254 infrastructure to allow users or user interface writers to switch
14255 between interpreters or run commands in other interpreters.
14257 @value{GDBN} currently supports two command interpreters, the console
14258 interpreter (sometimes called the command-line interpreter or @sc{cli})
14259 and the machine interface interpreter (or @sc{gdb/mi}). This manual
14260 describes both of these interfaces in great detail.
14262 By default, @value{GDBN} will start with the console interpreter.
14263 However, the user may choose to start @value{GDBN} with another
14264 interpreter by specifying the @option{-i} or @option{--interpreter}
14265 startup options. Defined interpreters include:
14269 @cindex console interpreter
14270 The traditional console or command-line interpreter. This is the most often
14271 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
14272 @value{GDBN} will use this interpreter.
14275 @cindex mi interpreter
14276 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
14277 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
14278 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
14282 @cindex mi2 interpreter
14283 The current @sc{gdb/mi} interface.
14286 @cindex mi1 interpreter
14287 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
14291 @cindex invoke another interpreter
14292 The interpreter being used by @value{GDBN} may not be dynamically
14293 switched at runtime. Although possible, this could lead to a very
14294 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
14295 enters the command "interpreter-set console" in a console view,
14296 @value{GDBN} would switch to using the console interpreter, rendering
14297 the IDE inoperable!
14299 @kindex interpreter-exec
14300 Although you may only choose a single interpreter at startup, you may execute
14301 commands in any interpreter from the current interpreter using the appropriate
14302 command. If you are running the console interpreter, simply use the
14303 @code{interpreter-exec} command:
14306 interpreter-exec mi "-data-list-register-names"
14309 @sc{gdb/mi} has a similar command, although it is only available in versions of
14310 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
14313 @chapter @value{GDBN} Text User Interface
14315 @cindex Text User Interface
14318 * TUI Overview:: TUI overview
14319 * TUI Keys:: TUI key bindings
14320 * TUI Single Key Mode:: TUI single key mode
14321 * TUI Commands:: TUI specific commands
14322 * TUI Configuration:: TUI configuration variables
14325 The @value{GDBN} Text User Interface, TUI in short, is a terminal
14326 interface which uses the @code{curses} library to show the source
14327 file, the assembly output, the program registers and @value{GDBN}
14328 commands in separate text windows.
14330 The TUI is enabled by invoking @value{GDBN} using either
14332 @samp{gdbtui} or @samp{gdb -tui}.
14335 @section TUI overview
14337 The TUI has two display modes that can be switched while
14342 A curses (or TUI) mode in which it displays several text
14343 windows on the terminal.
14346 A standard mode which corresponds to the @value{GDBN} configured without
14350 In the TUI mode, @value{GDBN} can display several text window
14355 This window is the @value{GDBN} command window with the @value{GDBN}
14356 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
14357 managed using readline but through the TUI. The @emph{command}
14358 window is always visible.
14361 The source window shows the source file of the program. The current
14362 line as well as active breakpoints are displayed in this window.
14365 The assembly window shows the disassembly output of the program.
14368 This window shows the processor registers. It detects when
14369 a register is changed and when this is the case, registers that have
14370 changed are highlighted.
14374 The source and assembly windows show the current program position
14375 by highlighting the current line and marking them with the @samp{>} marker.
14376 Breakpoints are also indicated with two markers. A first one
14377 indicates the breakpoint type:
14381 Breakpoint which was hit at least once.
14384 Breakpoint which was never hit.
14387 Hardware breakpoint which was hit at least once.
14390 Hardware breakpoint which was never hit.
14394 The second marker indicates whether the breakpoint is enabled or not:
14398 Breakpoint is enabled.
14401 Breakpoint is disabled.
14405 The source, assembly and register windows are attached to the thread
14406 and the frame position. They are updated when the current thread
14407 changes, when the frame changes or when the program counter changes.
14408 These three windows are arranged by the TUI according to several
14409 layouts. The layout defines which of these three windows are visible.
14410 The following layouts are available:
14420 source and assembly
14423 source and registers
14426 assembly and registers
14430 On top of the command window a status line gives various information
14431 concerning the current process begin debugged. The status line is
14432 updated when the information it shows changes. The following fields
14437 Indicates the current gdb target
14438 (@pxref{Targets, ,Specifying a Debugging Target}).
14441 Gives information about the current process or thread number.
14442 When no process is being debugged, this field is set to @code{No process}.
14445 Gives the current function name for the selected frame.
14446 The name is demangled if demangling is turned on (@pxref{Print Settings}).
14447 When there is no symbol corresponding to the current program counter
14448 the string @code{??} is displayed.
14451 Indicates the current line number for the selected frame.
14452 When the current line number is not known the string @code{??} is displayed.
14455 Indicates the current program counter address.
14460 @section TUI Key Bindings
14461 @cindex TUI key bindings
14463 The TUI installs several key bindings in the readline keymaps
14464 (@pxref{Command Line Editing}).
14465 They allow to leave or enter in the TUI mode or they operate
14466 directly on the TUI layout and windows. The TUI also provides
14467 a @emph{SingleKey} keymap which binds several keys directly to
14468 @value{GDBN} commands. The following key bindings
14469 are installed for both TUI mode and the @value{GDBN} standard mode.
14478 Enter or leave the TUI mode. When the TUI mode is left,
14479 the curses window management is left and @value{GDBN} operates using
14480 its standard mode writing on the terminal directly. When the TUI
14481 mode is entered, the control is given back to the curses windows.
14482 The screen is then refreshed.
14486 Use a TUI layout with only one window. The layout will
14487 either be @samp{source} or @samp{assembly}. When the TUI mode
14488 is not active, it will switch to the TUI mode.
14490 Think of this key binding as the Emacs @kbd{C-x 1} binding.
14494 Use a TUI layout with at least two windows. When the current
14495 layout shows already two windows, a next layout with two windows is used.
14496 When a new layout is chosen, one window will always be common to the
14497 previous layout and the new one.
14499 Think of it as the Emacs @kbd{C-x 2} binding.
14503 Change the active window. The TUI associates several key bindings
14504 (like scrolling and arrow keys) to the active window. This command
14505 gives the focus to the next TUI window.
14507 Think of it as the Emacs @kbd{C-x o} binding.
14511 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
14512 (@pxref{TUI Single Key Mode}).
14516 The following key bindings are handled only by the TUI mode:
14521 Scroll the active window one page up.
14525 Scroll the active window one page down.
14529 Scroll the active window one line up.
14533 Scroll the active window one line down.
14537 Scroll the active window one column left.
14541 Scroll the active window one column right.
14545 Refresh the screen.
14549 In the TUI mode, the arrow keys are used by the active window
14550 for scrolling. This means they are available for readline when the
14551 active window is the command window. When the command window
14552 does not have the focus, it is necessary to use other readline
14553 key bindings such as @key{C-p}, @key{C-n}, @key{C-b} and @key{C-f}.
14555 @node TUI Single Key Mode
14556 @section TUI Single Key Mode
14557 @cindex TUI single key mode
14559 The TUI provides a @emph{SingleKey} mode in which it installs a particular
14560 key binding in the readline keymaps to connect single keys to
14564 @kindex c @r{(SingleKey TUI key)}
14568 @kindex d @r{(SingleKey TUI key)}
14572 @kindex f @r{(SingleKey TUI key)}
14576 @kindex n @r{(SingleKey TUI key)}
14580 @kindex q @r{(SingleKey TUI key)}
14582 exit the @emph{SingleKey} mode.
14584 @kindex r @r{(SingleKey TUI key)}
14588 @kindex s @r{(SingleKey TUI key)}
14592 @kindex u @r{(SingleKey TUI key)}
14596 @kindex v @r{(SingleKey TUI key)}
14600 @kindex w @r{(SingleKey TUI key)}
14606 Other keys temporarily switch to the @value{GDBN} command prompt.
14607 The key that was pressed is inserted in the editing buffer so that
14608 it is possible to type most @value{GDBN} commands without interaction
14609 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
14610 @emph{SingleKey} mode is restored. The only way to permanently leave
14611 this mode is by hitting @key{q} or @samp{@key{C-x} @key{s}}.
14615 @section TUI specific commands
14616 @cindex TUI commands
14618 The TUI has specific commands to control the text windows.
14619 These commands are always available, that is they do not depend on
14620 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
14621 is in the standard mode, using these commands will automatically switch
14627 List and give the size of all displayed windows.
14631 Display the next layout.
14634 Display the previous layout.
14637 Display the source window only.
14640 Display the assembly window only.
14643 Display the source and assembly window.
14646 Display the register window together with the source or assembly window.
14648 @item focus next | prev | src | asm | regs | split
14650 Set the focus to the named window.
14651 This command allows to change the active window so that scrolling keys
14652 can be affected to another window.
14656 Refresh the screen. This is similar to using @key{C-L} key.
14658 @item tui reg float
14660 Show the floating point registers in the register window.
14662 @item tui reg general
14663 Show the general registers in the register window.
14666 Show the next register group. The list of register groups as well as
14667 their order is target specific. The predefined register groups are the
14668 following: @code{general}, @code{float}, @code{system}, @code{vector},
14669 @code{all}, @code{save}, @code{restore}.
14671 @item tui reg system
14672 Show the system registers in the register window.
14676 Update the source window and the current execution point.
14678 @item winheight @var{name} +@var{count}
14679 @itemx winheight @var{name} -@var{count}
14681 Change the height of the window @var{name} by @var{count}
14682 lines. Positive counts increase the height, while negative counts
14687 @node TUI Configuration
14688 @section TUI configuration variables
14689 @cindex TUI configuration variables
14691 The TUI has several configuration variables that control the
14692 appearance of windows on the terminal.
14695 @item set tui border-kind @var{kind}
14696 @kindex set tui border-kind
14697 Select the border appearance for the source, assembly and register windows.
14698 The possible values are the following:
14701 Use a space character to draw the border.
14704 Use ascii characters + - and | to draw the border.
14707 Use the Alternate Character Set to draw the border. The border is
14708 drawn using character line graphics if the terminal supports them.
14712 @item set tui active-border-mode @var{mode}
14713 @kindex set tui active-border-mode
14714 Select the attributes to display the border of the active window.
14715 The possible values are @code{normal}, @code{standout}, @code{reverse},
14716 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
14718 @item set tui border-mode @var{mode}
14719 @kindex set tui border-mode
14720 Select the attributes to display the border of other windows.
14721 The @var{mode} can be one of the following:
14724 Use normal attributes to display the border.
14730 Use reverse video mode.
14733 Use half bright mode.
14735 @item half-standout
14736 Use half bright and standout mode.
14739 Use extra bright or bold mode.
14741 @item bold-standout
14742 Use extra bright or bold and standout mode.
14749 @chapter Using @value{GDBN} under @sc{gnu} Emacs
14752 @cindex @sc{gnu} Emacs
14753 A special interface allows you to use @sc{gnu} Emacs to view (and
14754 edit) the source files for the program you are debugging with
14757 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
14758 executable file you want to debug as an argument. This command starts
14759 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
14760 created Emacs buffer.
14761 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
14763 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
14768 All ``terminal'' input and output goes through the Emacs buffer.
14771 This applies both to @value{GDBN} commands and their output, and to the input
14772 and output done by the program you are debugging.
14774 This is useful because it means that you can copy the text of previous
14775 commands and input them again; you can even use parts of the output
14778 All the facilities of Emacs' Shell mode are available for interacting
14779 with your program. In particular, you can send signals the usual
14780 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
14785 @value{GDBN} displays source code through Emacs.
14788 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
14789 source file for that frame and puts an arrow (@samp{=>}) at the
14790 left margin of the current line. Emacs uses a separate buffer for
14791 source display, and splits the screen to show both your @value{GDBN} session
14794 Explicit @value{GDBN} @code{list} or search commands still produce output as
14795 usual, but you probably have no reason to use them from Emacs.
14797 If you specify an absolute file name when prompted for the @kbd{M-x
14798 gdb} argument, then Emacs sets your current working directory to where
14799 your program resides. If you only specify the file name, then Emacs
14800 sets your current working directory to to the directory associated
14801 with the previous buffer. In this case, @value{GDBN} may find your
14802 program by searching your environment's @code{PATH} variable, but on
14803 some operating systems it might not find the source. So, although the
14804 @value{GDBN} input and output session proceeds normally, the auxiliary
14805 buffer does not display the current source and line of execution.
14807 The initial working directory of @value{GDBN} is printed on the top
14808 line of the @value{GDBN} I/O buffer and this serves as a default for
14809 the commands that specify files for @value{GDBN} to operate
14810 on. @xref{Files, ,Commands to specify files}.
14812 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
14813 need to call @value{GDBN} by a different name (for example, if you
14814 keep several configurations around, with different names) you can
14815 customize the Emacs variable @code{gud-gdb-command-name} to run the
14818 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
14819 addition to the standard Shell mode commands:
14823 Describe the features of Emacs' @value{GDBN} Mode.
14826 Execute to another source line, like the @value{GDBN} @code{step} command; also
14827 update the display window to show the current file and location.
14830 Execute to next source line in this function, skipping all function
14831 calls, like the @value{GDBN} @code{next} command. Then update the display window
14832 to show the current file and location.
14835 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
14836 display window accordingly.
14839 Execute until exit from the selected stack frame, like the @value{GDBN}
14840 @code{finish} command.
14843 Continue execution of your program, like the @value{GDBN} @code{continue}
14847 Go up the number of frames indicated by the numeric argument
14848 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
14849 like the @value{GDBN} @code{up} command.
14852 Go down the number of frames indicated by the numeric argument, like the
14853 @value{GDBN} @code{down} command.
14856 In any source file, the Emacs command @kbd{C-x SPC} (@code{gud-break})
14857 tells @value{GDBN} to set a breakpoint on the source line point is on.
14859 If you type @kbd{M-x speedbar}, then Emacs displays a separate frame which
14860 shows a backtrace when the @value{GDBN} I/O buffer is current. Move
14861 point to any frame in the stack and type @key{RET} to make it become the
14862 current frame and display the associated source in the source buffer.
14863 Alternatively, click @kbd{Mouse-2} to make the selected frame become the
14866 If you accidentally delete the source-display buffer, an easy way to get
14867 it back is to type the command @code{f} in the @value{GDBN} buffer, to
14868 request a frame display; when you run under Emacs, this recreates
14869 the source buffer if necessary to show you the context of the current
14872 The source files displayed in Emacs are in ordinary Emacs buffers
14873 which are visiting the source files in the usual way. You can edit
14874 the files with these buffers if you wish; but keep in mind that @value{GDBN}
14875 communicates with Emacs in terms of line numbers. If you add or
14876 delete lines from the text, the line numbers that @value{GDBN} knows cease
14877 to correspond properly with the code.
14879 The description given here is for GNU Emacs version 21.3 and a more
14880 detailed description of its interaction with @value{GDBN} is given in
14881 the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu} Emacs Manual}).
14883 @c The following dropped because Epoch is nonstandard. Reactivate
14884 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
14886 @kindex Emacs Epoch environment
14890 Version 18 of @sc{gnu} Emacs has a built-in window system
14891 called the @code{epoch}
14892 environment. Users of this environment can use a new command,
14893 @code{inspect} which performs identically to @code{print} except that
14894 each value is printed in its own window.
14899 @chapter The @sc{gdb/mi} Interface
14901 @unnumberedsec Function and Purpose
14903 @cindex @sc{gdb/mi}, its purpose
14904 @sc{gdb/mi} is a line based machine oriented text interface to @value{GDBN}. It is
14905 specifically intended to support the development of systems which use
14906 the debugger as just one small component of a larger system.
14908 This chapter is a specification of the @sc{gdb/mi} interface. It is written
14909 in the form of a reference manual.
14911 Note that @sc{gdb/mi} is still under construction, so some of the
14912 features described below are incomplete and subject to change.
14914 @unnumberedsec Notation and Terminology
14916 @cindex notational conventions, for @sc{gdb/mi}
14917 This chapter uses the following notation:
14921 @code{|} separates two alternatives.
14924 @code{[ @var{something} ]} indicates that @var{something} is optional:
14925 it may or may not be given.
14928 @code{( @var{group} )*} means that @var{group} inside the parentheses
14929 may repeat zero or more times.
14932 @code{( @var{group} )+} means that @var{group} inside the parentheses
14933 may repeat one or more times.
14936 @code{"@var{string}"} means a literal @var{string}.
14940 @heading Dependencies
14943 @heading Acknowledgments
14945 In alphabetic order: Andrew Cagney, Fernando Nasser, Stan Shebs and
14949 * GDB/MI Command Syntax::
14950 * GDB/MI Compatibility with CLI::
14951 * GDB/MI Output Records::
14952 * GDB/MI Command Description Format::
14953 * GDB/MI Breakpoint Table Commands::
14954 * GDB/MI Data Manipulation::
14955 * GDB/MI Program Control::
14956 * GDB/MI Miscellaneous Commands::
14958 * GDB/MI Kod Commands::
14959 * GDB/MI Memory Overlay Commands::
14960 * GDB/MI Signal Handling Commands::
14962 * GDB/MI Stack Manipulation::
14963 * GDB/MI Symbol Query::
14964 * GDB/MI Target Manipulation::
14965 * GDB/MI Thread Commands::
14966 * GDB/MI Tracepoint Commands::
14967 * GDB/MI Variable Objects::
14970 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14971 @node GDB/MI Command Syntax
14972 @section @sc{gdb/mi} Command Syntax
14975 * GDB/MI Input Syntax::
14976 * GDB/MI Output Syntax::
14977 * GDB/MI Simple Examples::
14980 @node GDB/MI Input Syntax
14981 @subsection @sc{gdb/mi} Input Syntax
14983 @cindex input syntax for @sc{gdb/mi}
14984 @cindex @sc{gdb/mi}, input syntax
14986 @item @var{command} @expansion{}
14987 @code{@var{cli-command} | @var{mi-command}}
14989 @item @var{cli-command} @expansion{}
14990 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
14991 @var{cli-command} is any existing @value{GDBN} CLI command.
14993 @item @var{mi-command} @expansion{}
14994 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
14995 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
14997 @item @var{token} @expansion{}
14998 "any sequence of digits"
15000 @item @var{option} @expansion{}
15001 @code{"-" @var{parameter} [ " " @var{parameter} ]}
15003 @item @var{parameter} @expansion{}
15004 @code{@var{non-blank-sequence} | @var{c-string}}
15006 @item @var{operation} @expansion{}
15007 @emph{any of the operations described in this chapter}
15009 @item @var{non-blank-sequence} @expansion{}
15010 @emph{anything, provided it doesn't contain special characters such as
15011 "-", @var{nl}, """ and of course " "}
15013 @item @var{c-string} @expansion{}
15014 @code{""" @var{seven-bit-iso-c-string-content} """}
15016 @item @var{nl} @expansion{}
15025 The CLI commands are still handled by the @sc{mi} interpreter; their
15026 output is described below.
15029 The @code{@var{token}}, when present, is passed back when the command
15033 Some @sc{mi} commands accept optional arguments as part of the parameter
15034 list. Each option is identified by a leading @samp{-} (dash) and may be
15035 followed by an optional argument parameter. Options occur first in the
15036 parameter list and can be delimited from normal parameters using
15037 @samp{--} (this is useful when some parameters begin with a dash).
15044 We want easy access to the existing CLI syntax (for debugging).
15047 We want it to be easy to spot a @sc{mi} operation.
15050 @node GDB/MI Output Syntax
15051 @subsection @sc{gdb/mi} Output Syntax
15053 @cindex output syntax of @sc{gdb/mi}
15054 @cindex @sc{gdb/mi}, output syntax
15055 The output from @sc{gdb/mi} consists of zero or more out-of-band records
15056 followed, optionally, by a single result record. This result record
15057 is for the most recent command. The sequence of output records is
15058 terminated by @samp{(@value{GDBP})}.
15060 If an input command was prefixed with a @code{@var{token}} then the
15061 corresponding output for that command will also be prefixed by that same
15065 @item @var{output} @expansion{}
15066 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(@value{GDBP})" @var{nl}}
15068 @item @var{result-record} @expansion{}
15069 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
15071 @item @var{out-of-band-record} @expansion{}
15072 @code{@var{async-record} | @var{stream-record}}
15074 @item @var{async-record} @expansion{}
15075 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
15077 @item @var{exec-async-output} @expansion{}
15078 @code{[ @var{token} ] "*" @var{async-output}}
15080 @item @var{status-async-output} @expansion{}
15081 @code{[ @var{token} ] "+" @var{async-output}}
15083 @item @var{notify-async-output} @expansion{}
15084 @code{[ @var{token} ] "=" @var{async-output}}
15086 @item @var{async-output} @expansion{}
15087 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
15089 @item @var{result-class} @expansion{}
15090 @code{"done" | "running" | "connected" | "error" | "exit"}
15092 @item @var{async-class} @expansion{}
15093 @code{"stopped" | @var{others}} (where @var{others} will be added
15094 depending on the needs---this is still in development).
15096 @item @var{result} @expansion{}
15097 @code{ @var{variable} "=" @var{value}}
15099 @item @var{variable} @expansion{}
15100 @code{ @var{string} }
15102 @item @var{value} @expansion{}
15103 @code{ @var{const} | @var{tuple} | @var{list} }
15105 @item @var{const} @expansion{}
15106 @code{@var{c-string}}
15108 @item @var{tuple} @expansion{}
15109 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
15111 @item @var{list} @expansion{}
15112 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
15113 @var{result} ( "," @var{result} )* "]" }
15115 @item @var{stream-record} @expansion{}
15116 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
15118 @item @var{console-stream-output} @expansion{}
15119 @code{"~" @var{c-string}}
15121 @item @var{target-stream-output} @expansion{}
15122 @code{"@@" @var{c-string}}
15124 @item @var{log-stream-output} @expansion{}
15125 @code{"&" @var{c-string}}
15127 @item @var{nl} @expansion{}
15130 @item @var{token} @expansion{}
15131 @emph{any sequence of digits}.
15139 All output sequences end in a single line containing a period.
15142 The @code{@var{token}} is from the corresponding request. If an execution
15143 command is interrupted by the @samp{-exec-interrupt} command, the
15144 @var{token} associated with the @samp{*stopped} message is the one of the
15145 original execution command, not the one of the interrupt command.
15148 @cindex status output in @sc{gdb/mi}
15149 @var{status-async-output} contains on-going status information about the
15150 progress of a slow operation. It can be discarded. All status output is
15151 prefixed by @samp{+}.
15154 @cindex async output in @sc{gdb/mi}
15155 @var{exec-async-output} contains asynchronous state change on the target
15156 (stopped, started, disappeared). All async output is prefixed by
15160 @cindex notify output in @sc{gdb/mi}
15161 @var{notify-async-output} contains supplementary information that the
15162 client should handle (e.g., a new breakpoint information). All notify
15163 output is prefixed by @samp{=}.
15166 @cindex console output in @sc{gdb/mi}
15167 @var{console-stream-output} is output that should be displayed as is in the
15168 console. It is the textual response to a CLI command. All the console
15169 output is prefixed by @samp{~}.
15172 @cindex target output in @sc{gdb/mi}
15173 @var{target-stream-output} is the output produced by the target program.
15174 All the target output is prefixed by @samp{@@}.
15177 @cindex log output in @sc{gdb/mi}
15178 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
15179 instance messages that should be displayed as part of an error log. All
15180 the log output is prefixed by @samp{&}.
15183 @cindex list output in @sc{gdb/mi}
15184 New @sc{gdb/mi} commands should only output @var{lists} containing
15190 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
15191 details about the various output records.
15193 @node GDB/MI Simple Examples
15194 @subsection Simple Examples of @sc{gdb/mi} Interaction
15195 @cindex @sc{gdb/mi}, simple examples
15197 This subsection presents several simple examples of interaction using
15198 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
15199 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
15200 the output received from @sc{gdb/mi}.
15202 @subsubheading Target Stop
15203 @c Ummm... There is no "-stop" command. This assumes async, no?
15204 Here's an example of stopping the inferior process:
15215 <- *stop,reason="stop",address="0x123",source="a.c:123"
15219 @subsubheading Simple CLI Command
15221 Here's an example of a simple CLI command being passed through
15222 @sc{gdb/mi} and on to the CLI.
15232 @subsubheading Command With Side Effects
15235 -> -symbol-file xyz.exe
15236 <- *breakpoint,nr="3",address="0x123",source="a.c:123"
15240 @subsubheading A Bad Command
15242 Here's what happens if you pass a non-existent command:
15246 <- ^error,msg="Undefined MI command: rubbish"
15250 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15251 @node GDB/MI Compatibility with CLI
15252 @section @sc{gdb/mi} Compatibility with CLI
15254 @cindex compatibility, @sc{gdb/mi} and CLI
15255 @cindex @sc{gdb/mi}, compatibility with CLI
15256 To help users familiar with @value{GDBN}'s existing CLI interface, @sc{gdb/mi}
15257 accepts existing CLI commands. As specified by the syntax, such
15258 commands can be directly entered into the @sc{gdb/mi} interface and @value{GDBN} will
15261 This mechanism is provided as an aid to developers of @sc{gdb/mi}
15262 clients and not as a reliable interface into the CLI. Since the command
15263 is being interpreteted in an environment that assumes @sc{gdb/mi}
15264 behaviour, the exact output of such commands is likely to end up being
15265 an un-supported hybrid of @sc{gdb/mi} and CLI output.
15267 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15268 @node GDB/MI Output Records
15269 @section @sc{gdb/mi} Output Records
15272 * GDB/MI Result Records::
15273 * GDB/MI Stream Records::
15274 * GDB/MI Out-of-band Records::
15277 @node GDB/MI Result Records
15278 @subsection @sc{gdb/mi} Result Records
15280 @cindex result records in @sc{gdb/mi}
15281 @cindex @sc{gdb/mi}, result records
15282 In addition to a number of out-of-band notifications, the response to a
15283 @sc{gdb/mi} command includes one of the following result indications:
15287 @item "^done" [ "," @var{results} ]
15288 The synchronous operation was successful, @code{@var{results}} are the return
15293 @c Is this one correct? Should it be an out-of-band notification?
15294 The asynchronous operation was successfully started. The target is
15297 @item "^error" "," @var{c-string}
15299 The operation failed. The @code{@var{c-string}} contains the corresponding
15303 @node GDB/MI Stream Records
15304 @subsection @sc{gdb/mi} Stream Records
15306 @cindex @sc{gdb/mi}, stream records
15307 @cindex stream records in @sc{gdb/mi}
15308 @value{GDBN} internally maintains a number of output streams: the console, the
15309 target, and the log. The output intended for each of these streams is
15310 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
15312 Each stream record begins with a unique @dfn{prefix character} which
15313 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
15314 Syntax}). In addition to the prefix, each stream record contains a
15315 @code{@var{string-output}}. This is either raw text (with an implicit new
15316 line) or a quoted C string (which does not contain an implicit newline).
15319 @item "~" @var{string-output}
15320 The console output stream contains text that should be displayed in the
15321 CLI console window. It contains the textual responses to CLI commands.
15323 @item "@@" @var{string-output}
15324 The target output stream contains any textual output from the running
15327 @item "&" @var{string-output}
15328 The log stream contains debugging messages being produced by @value{GDBN}'s
15332 @node GDB/MI Out-of-band Records
15333 @subsection @sc{gdb/mi} Out-of-band Records
15335 @cindex out-of-band records in @sc{gdb/mi}
15336 @cindex @sc{gdb/mi}, out-of-band records
15337 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
15338 additional changes that have occurred. Those changes can either be a
15339 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
15340 target activity (e.g., target stopped).
15342 The following is a preliminary list of possible out-of-band records.
15349 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15350 @node GDB/MI Command Description Format
15351 @section @sc{gdb/mi} Command Description Format
15353 The remaining sections describe blocks of commands. Each block of
15354 commands is laid out in a fashion similar to this section.
15356 Note the the line breaks shown in the examples are here only for
15357 readability. They don't appear in the real output.
15358 Also note that the commands with a non-available example (N.A.@:) are
15359 not yet implemented.
15361 @subheading Motivation
15363 The motivation for this collection of commands.
15365 @subheading Introduction
15367 A brief introduction to this collection of commands as a whole.
15369 @subheading Commands
15371 For each command in the block, the following is described:
15373 @subsubheading Synopsis
15376 -command @var{args}@dots{}
15379 @subsubheading @value{GDBN} Command
15381 The corresponding @value{GDBN} CLI command.
15383 @subsubheading Result
15385 @subsubheading Out-of-band
15387 @subsubheading Notes
15389 @subsubheading Example
15392 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15393 @node GDB/MI Breakpoint Table Commands
15394 @section @sc{gdb/mi} Breakpoint table commands
15396 @cindex breakpoint commands for @sc{gdb/mi}
15397 @cindex @sc{gdb/mi}, breakpoint commands
15398 This section documents @sc{gdb/mi} commands for manipulating
15401 @subheading The @code{-break-after} Command
15402 @findex -break-after
15404 @subsubheading Synopsis
15407 -break-after @var{number} @var{count}
15410 The breakpoint number @var{number} is not in effect until it has been
15411 hit @var{count} times. To see how this is reflected in the output of
15412 the @samp{-break-list} command, see the description of the
15413 @samp{-break-list} command below.
15415 @subsubheading @value{GDBN} Command
15417 The corresponding @value{GDBN} command is @samp{ignore}.
15419 @subsubheading Example
15424 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",line="5"@}
15431 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15432 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15433 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15434 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15435 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15436 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15437 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15438 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15439 addr="0x000100d0",func="main",file="hello.c",line="5",times="0",
15445 @subheading The @code{-break-catch} Command
15446 @findex -break-catch
15448 @subheading The @code{-break-commands} Command
15449 @findex -break-commands
15453 @subheading The @code{-break-condition} Command
15454 @findex -break-condition
15456 @subsubheading Synopsis
15459 -break-condition @var{number} @var{expr}
15462 Breakpoint @var{number} will stop the program only if the condition in
15463 @var{expr} is true. The condition becomes part of the
15464 @samp{-break-list} output (see the description of the @samp{-break-list}
15467 @subsubheading @value{GDBN} Command
15469 The corresponding @value{GDBN} command is @samp{condition}.
15471 @subsubheading Example
15475 -break-condition 1 1
15479 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15480 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15481 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15482 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15483 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15484 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15485 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15486 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15487 addr="0x000100d0",func="main",file="hello.c",line="5",cond="1",
15488 times="0",ignore="3"@}]@}
15492 @subheading The @code{-break-delete} Command
15493 @findex -break-delete
15495 @subsubheading Synopsis
15498 -break-delete ( @var{breakpoint} )+
15501 Delete the breakpoint(s) whose number(s) are specified in the argument
15502 list. This is obviously reflected in the breakpoint list.
15504 @subsubheading @value{GDBN} command
15506 The corresponding @value{GDBN} command is @samp{delete}.
15508 @subsubheading Example
15516 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
15517 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15518 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15519 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15520 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15521 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15522 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15527 @subheading The @code{-break-disable} Command
15528 @findex -break-disable
15530 @subsubheading Synopsis
15533 -break-disable ( @var{breakpoint} )+
15536 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
15537 break list is now set to @samp{n} for the named @var{breakpoint}(s).
15539 @subsubheading @value{GDBN} Command
15541 The corresponding @value{GDBN} command is @samp{disable}.
15543 @subsubheading Example
15551 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15552 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15553 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15554 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15555 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15556 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15557 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15558 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
15559 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
15563 @subheading The @code{-break-enable} Command
15564 @findex -break-enable
15566 @subsubheading Synopsis
15569 -break-enable ( @var{breakpoint} )+
15572 Enable (previously disabled) @var{breakpoint}(s).
15574 @subsubheading @value{GDBN} Command
15576 The corresponding @value{GDBN} command is @samp{enable}.
15578 @subsubheading Example
15586 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15587 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15588 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15589 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15590 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15591 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15592 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15593 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
15594 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
15598 @subheading The @code{-break-info} Command
15599 @findex -break-info
15601 @subsubheading Synopsis
15604 -break-info @var{breakpoint}
15608 Get information about a single breakpoint.
15610 @subsubheading @value{GDBN} command
15612 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
15614 @subsubheading Example
15617 @subheading The @code{-break-insert} Command
15618 @findex -break-insert
15620 @subsubheading Synopsis
15623 -break-insert [ -t ] [ -h ] [ -r ]
15624 [ -c @var{condition} ] [ -i @var{ignore-count} ]
15625 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
15629 If specified, @var{line}, can be one of:
15636 @item filename:linenum
15637 @item filename:function
15641 The possible optional parameters of this command are:
15645 Insert a tempoary breakpoint.
15647 Insert a hardware breakpoint.
15648 @item -c @var{condition}
15649 Make the breakpoint conditional on @var{condition}.
15650 @item -i @var{ignore-count}
15651 Initialize the @var{ignore-count}.
15653 Insert a regular breakpoint in all the functions whose names match the
15654 given regular expression. Other flags are not applicable to regular
15658 @subsubheading Result
15660 The result is in the form:
15663 ^done,bkptno="@var{number}",func="@var{funcname}",
15664 file="@var{filename}",line="@var{lineno}"
15668 where @var{number} is the @value{GDBN} number for this breakpoint, @var{funcname}
15669 is the name of the function where the breakpoint was inserted,
15670 @var{filename} is the name of the source file which contains this
15671 function, and @var{lineno} is the source line number within that file.
15673 Note: this format is open to change.
15674 @c An out-of-band breakpoint instead of part of the result?
15676 @subsubheading @value{GDBN} Command
15678 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
15679 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
15681 @subsubheading Example
15686 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
15688 -break-insert -t foo
15689 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",line="11"@}
15692 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15693 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15694 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15695 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15696 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15697 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15698 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15699 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15700 addr="0x0001072c", func="main",file="recursive2.c",line="4",times="0"@},
15701 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
15702 addr="0x00010774",func="foo",file="recursive2.c",line="11",times="0"@}]@}
15704 -break-insert -r foo.*
15705 ~int foo(int, int);
15706 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c",line="11"@}
15710 @subheading The @code{-break-list} Command
15711 @findex -break-list
15713 @subsubheading Synopsis
15719 Displays the list of inserted breakpoints, showing the following fields:
15723 number of the breakpoint
15725 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
15727 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
15730 is the breakpoint enabled or no: @samp{y} or @samp{n}
15732 memory location at which the breakpoint is set
15734 logical location of the breakpoint, expressed by function name, file
15737 number of times the breakpoint has been hit
15740 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
15741 @code{body} field is an empty list.
15743 @subsubheading @value{GDBN} Command
15745 The corresponding @value{GDBN} command is @samp{info break}.
15747 @subsubheading Example
15752 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15753 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15754 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15755 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15756 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15757 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15758 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15759 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15760 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
15761 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
15762 addr="0x00010114",func="foo",file="hello.c",line="13",times="0"@}]@}
15766 Here's an example of the result when there are no breakpoints:
15771 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
15772 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15773 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15774 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15775 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15776 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15777 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15782 @subheading The @code{-break-watch} Command
15783 @findex -break-watch
15785 @subsubheading Synopsis
15788 -break-watch [ -a | -r ]
15791 Create a watchpoint. With the @samp{-a} option it will create an
15792 @dfn{access} watchpoint, i.e. a watchpoint that triggers either on a
15793 read from or on a write to the memory location. With the @samp{-r}
15794 option, the watchpoint created is a @dfn{read} watchpoint, i.e. it will
15795 trigger only when the memory location is accessed for reading. Without
15796 either of the options, the watchpoint created is a regular watchpoint,
15797 i.e. it will trigger when the memory location is accessed for writing.
15798 @xref{Set Watchpoints, , Setting watchpoints}.
15800 Note that @samp{-break-list} will report a single list of watchpoints and
15801 breakpoints inserted.
15803 @subsubheading @value{GDBN} Command
15805 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
15808 @subsubheading Example
15810 Setting a watchpoint on a variable in the @code{main} function:
15815 ^done,wpt=@{number="2",exp="x"@}
15819 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
15820 value=@{old="-268439212",new="55"@},
15821 frame=@{func="main",args=[],file="recursive2.c",line="5"@}
15825 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
15826 the program execution twice: first for the variable changing value, then
15827 for the watchpoint going out of scope.
15832 ^done,wpt=@{number="5",exp="C"@}
15836 ^done,reason="watchpoint-trigger",
15837 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
15838 frame=@{func="callee4",args=[],
15839 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
15843 ^done,reason="watchpoint-scope",wpnum="5",
15844 frame=@{func="callee3",args=[@{name="strarg",
15845 value="0x11940 \"A string argument.\""@}],
15846 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
15850 Listing breakpoints and watchpoints, at different points in the program
15851 execution. Note that once the watchpoint goes out of scope, it is
15857 ^done,wpt=@{number="2",exp="C"@}
15860 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15861 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15862 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15863 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15864 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15865 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15866 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15867 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15868 addr="0x00010734",func="callee4",
15869 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
15870 bkpt=@{number="2",type="watchpoint",disp="keep",
15871 enabled="y",addr="",what="C",times="0"@}]@}
15875 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
15876 value=@{old="-276895068",new="3"@},
15877 frame=@{func="callee4",args=[],
15878 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
15881 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15882 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15883 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15884 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15885 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15886 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15887 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15888 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15889 addr="0x00010734",func="callee4",
15890 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
15891 bkpt=@{number="2",type="watchpoint",disp="keep",
15892 enabled="y",addr="",what="C",times="-5"@}]@}
15896 ^done,reason="watchpoint-scope",wpnum="2",
15897 frame=@{func="callee3",args=[@{name="strarg",
15898 value="0x11940 \"A string argument.\""@}],
15899 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
15902 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15903 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15904 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15905 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15906 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15907 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15908 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15909 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15910 addr="0x00010734",func="callee4",
15911 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@}]@}
15915 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15916 @node GDB/MI Data Manipulation
15917 @section @sc{gdb/mi} Data Manipulation
15919 @cindex data manipulation, in @sc{gdb/mi}
15920 @cindex @sc{gdb/mi}, data manipulation
15921 This section describes the @sc{gdb/mi} commands that manipulate data:
15922 examine memory and registers, evaluate expressions, etc.
15924 @c REMOVED FROM THE INTERFACE.
15925 @c @subheading -data-assign
15926 @c Change the value of a program variable. Plenty of side effects.
15927 @c @subsubheading GDB command
15929 @c @subsubheading Example
15932 @subheading The @code{-data-disassemble} Command
15933 @findex -data-disassemble
15935 @subsubheading Synopsis
15939 [ -s @var{start-addr} -e @var{end-addr} ]
15940 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
15948 @item @var{start-addr}
15949 is the beginning address (or @code{$pc})
15950 @item @var{end-addr}
15952 @item @var{filename}
15953 is the name of the file to disassemble
15954 @item @var{linenum}
15955 is the line number to disassemble around
15957 is the the number of disassembly lines to be produced. If it is -1,
15958 the whole function will be disassembled, in case no @var{end-addr} is
15959 specified. If @var{end-addr} is specified as a non-zero value, and
15960 @var{lines} is lower than the number of disassembly lines between
15961 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
15962 displayed; if @var{lines} is higher than the number of lines between
15963 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
15966 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
15970 @subsubheading Result
15972 The output for each instruction is composed of four fields:
15981 Note that whatever included in the instruction field, is not manipulated
15982 directely by @sc{gdb/mi}, i.e. it is not possible to adjust its format.
15984 @subsubheading @value{GDBN} Command
15986 There's no direct mapping from this command to the CLI.
15988 @subsubheading Example
15990 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
15994 -data-disassemble -s $pc -e "$pc + 20" -- 0
15997 @{address="0x000107c0",func-name="main",offset="4",
15998 inst="mov 2, %o0"@},
15999 @{address="0x000107c4",func-name="main",offset="8",
16000 inst="sethi %hi(0x11800), %o2"@},
16001 @{address="0x000107c8",func-name="main",offset="12",
16002 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
16003 @{address="0x000107cc",func-name="main",offset="16",
16004 inst="sethi %hi(0x11800), %o2"@},
16005 @{address="0x000107d0",func-name="main",offset="20",
16006 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
16010 Disassemble the whole @code{main} function. Line 32 is part of
16014 -data-disassemble -f basics.c -l 32 -- 0
16016 @{address="0x000107bc",func-name="main",offset="0",
16017 inst="save %sp, -112, %sp"@},
16018 @{address="0x000107c0",func-name="main",offset="4",
16019 inst="mov 2, %o0"@},
16020 @{address="0x000107c4",func-name="main",offset="8",
16021 inst="sethi %hi(0x11800), %o2"@},
16023 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
16024 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
16028 Disassemble 3 instructions from the start of @code{main}:
16032 -data-disassemble -f basics.c -l 32 -n 3 -- 0
16034 @{address="0x000107bc",func-name="main",offset="0",
16035 inst="save %sp, -112, %sp"@},
16036 @{address="0x000107c0",func-name="main",offset="4",
16037 inst="mov 2, %o0"@},
16038 @{address="0x000107c4",func-name="main",offset="8",
16039 inst="sethi %hi(0x11800), %o2"@}]
16043 Disassemble 3 instructions from the start of @code{main} in mixed mode:
16047 -data-disassemble -f basics.c -l 32 -n 3 -- 1
16049 src_and_asm_line=@{line="31",
16050 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
16051 testsuite/gdb.mi/basics.c",line_asm_insn=[
16052 @{address="0x000107bc",func-name="main",offset="0",
16053 inst="save %sp, -112, %sp"@}]@},
16054 src_and_asm_line=@{line="32",
16055 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
16056 testsuite/gdb.mi/basics.c",line_asm_insn=[
16057 @{address="0x000107c0",func-name="main",offset="4",
16058 inst="mov 2, %o0"@},
16059 @{address="0x000107c4",func-name="main",offset="8",
16060 inst="sethi %hi(0x11800), %o2"@}]@}]
16065 @subheading The @code{-data-evaluate-expression} Command
16066 @findex -data-evaluate-expression
16068 @subsubheading Synopsis
16071 -data-evaluate-expression @var{expr}
16074 Evaluate @var{expr} as an expression. The expression could contain an
16075 inferior function call. The function call will execute synchronously.
16076 If the expression contains spaces, it must be enclosed in double quotes.
16078 @subsubheading @value{GDBN} Command
16080 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
16081 @samp{call}. In @code{gdbtk} only, there's a corresponding
16082 @samp{gdb_eval} command.
16084 @subsubheading Example
16086 In the following example, the numbers that precede the commands are the
16087 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
16088 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
16092 211-data-evaluate-expression A
16095 311-data-evaluate-expression &A
16096 311^done,value="0xefffeb7c"
16098 411-data-evaluate-expression A+3
16101 511-data-evaluate-expression "A + 3"
16107 @subheading The @code{-data-list-changed-registers} Command
16108 @findex -data-list-changed-registers
16110 @subsubheading Synopsis
16113 -data-list-changed-registers
16116 Display a list of the registers that have changed.
16118 @subsubheading @value{GDBN} Command
16120 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
16121 has the corresponding command @samp{gdb_changed_register_list}.
16123 @subsubheading Example
16125 On a PPC MBX board:
16133 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
16134 args=[],file="try.c",line="5"@}
16136 -data-list-changed-registers
16137 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
16138 "10","11","13","14","15","16","17","18","19","20","21","22","23",
16139 "24","25","26","27","28","30","31","64","65","66","67","69"]
16144 @subheading The @code{-data-list-register-names} Command
16145 @findex -data-list-register-names
16147 @subsubheading Synopsis
16150 -data-list-register-names [ ( @var{regno} )+ ]
16153 Show a list of register names for the current target. If no arguments
16154 are given, it shows a list of the names of all the registers. If
16155 integer numbers are given as arguments, it will print a list of the
16156 names of the registers corresponding to the arguments. To ensure
16157 consistency between a register name and its number, the output list may
16158 include empty register names.
16160 @subsubheading @value{GDBN} Command
16162 @value{GDBN} does not have a command which corresponds to
16163 @samp{-data-list-register-names}. In @code{gdbtk} there is a
16164 corresponding command @samp{gdb_regnames}.
16166 @subsubheading Example
16168 For the PPC MBX board:
16171 -data-list-register-names
16172 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
16173 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
16174 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
16175 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
16176 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
16177 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
16178 "", "pc","ps","cr","lr","ctr","xer"]
16180 -data-list-register-names 1 2 3
16181 ^done,register-names=["r1","r2","r3"]
16185 @subheading The @code{-data-list-register-values} Command
16186 @findex -data-list-register-values
16188 @subsubheading Synopsis
16191 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
16194 Display the registers' contents. @var{fmt} is the format according to
16195 which the registers' contents are to be returned, followed by an optional
16196 list of numbers specifying the registers to display. A missing list of
16197 numbers indicates that the contents of all the registers must be returned.
16199 Allowed formats for @var{fmt} are:
16216 @subsubheading @value{GDBN} Command
16218 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
16219 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
16221 @subsubheading Example
16223 For a PPC MBX board (note: line breaks are for readability only, they
16224 don't appear in the actual output):
16228 -data-list-register-values r 64 65
16229 ^done,register-values=[@{number="64",value="0xfe00a300"@},
16230 @{number="65",value="0x00029002"@}]
16232 -data-list-register-values x
16233 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
16234 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
16235 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
16236 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
16237 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
16238 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
16239 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
16240 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
16241 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
16242 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
16243 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
16244 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
16245 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
16246 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
16247 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
16248 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
16249 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
16250 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
16251 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
16252 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
16253 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
16254 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
16255 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
16256 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
16257 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
16258 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
16259 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
16260 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
16261 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
16262 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
16263 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
16264 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
16265 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
16266 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
16267 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
16268 @{number="69",value="0x20002b03"@}]
16273 @subheading The @code{-data-read-memory} Command
16274 @findex -data-read-memory
16276 @subsubheading Synopsis
16279 -data-read-memory [ -o @var{byte-offset} ]
16280 @var{address} @var{word-format} @var{word-size}
16281 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
16288 @item @var{address}
16289 An expression specifying the address of the first memory word to be
16290 read. Complex expressions containing embedded white space should be
16291 quoted using the C convention.
16293 @item @var{word-format}
16294 The format to be used to print the memory words. The notation is the
16295 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
16298 @item @var{word-size}
16299 The size of each memory word in bytes.
16301 @item @var{nr-rows}
16302 The number of rows in the output table.
16304 @item @var{nr-cols}
16305 The number of columns in the output table.
16308 If present, indicates that each row should include an @sc{ascii} dump. The
16309 value of @var{aschar} is used as a padding character when a byte is not a
16310 member of the printable @sc{ascii} character set (printable @sc{ascii}
16311 characters are those whose code is between 32 and 126, inclusively).
16313 @item @var{byte-offset}
16314 An offset to add to the @var{address} before fetching memory.
16317 This command displays memory contents as a table of @var{nr-rows} by
16318 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
16319 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
16320 (returned as @samp{total-bytes}). Should less than the requested number
16321 of bytes be returned by the target, the missing words are identified
16322 using @samp{N/A}. The number of bytes read from the target is returned
16323 in @samp{nr-bytes} and the starting address used to read memory in
16326 The address of the next/previous row or page is available in
16327 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
16330 @subsubheading @value{GDBN} Command
16332 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
16333 @samp{gdb_get_mem} memory read command.
16335 @subsubheading Example
16337 Read six bytes of memory starting at @code{bytes+6} but then offset by
16338 @code{-6} bytes. Format as three rows of two columns. One byte per
16339 word. Display each word in hex.
16343 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
16344 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
16345 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
16346 prev-page="0x0000138a",memory=[
16347 @{addr="0x00001390",data=["0x00","0x01"]@},
16348 @{addr="0x00001392",data=["0x02","0x03"]@},
16349 @{addr="0x00001394",data=["0x04","0x05"]@}]
16353 Read two bytes of memory starting at address @code{shorts + 64} and
16354 display as a single word formatted in decimal.
16358 5-data-read-memory shorts+64 d 2 1 1
16359 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
16360 next-row="0x00001512",prev-row="0x0000150e",
16361 next-page="0x00001512",prev-page="0x0000150e",memory=[
16362 @{addr="0x00001510",data=["128"]@}]
16366 Read thirty two bytes of memory starting at @code{bytes+16} and format
16367 as eight rows of four columns. Include a string encoding with @samp{x}
16368 used as the non-printable character.
16372 4-data-read-memory bytes+16 x 1 8 4 x
16373 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
16374 next-row="0x000013c0",prev-row="0x0000139c",
16375 next-page="0x000013c0",prev-page="0x00001380",memory=[
16376 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
16377 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
16378 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
16379 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
16380 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
16381 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
16382 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
16383 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
16387 @subheading The @code{-display-delete} Command
16388 @findex -display-delete
16390 @subsubheading Synopsis
16393 -display-delete @var{number}
16396 Delete the display @var{number}.
16398 @subsubheading @value{GDBN} Command
16400 The corresponding @value{GDBN} command is @samp{delete display}.
16402 @subsubheading Example
16406 @subheading The @code{-display-disable} Command
16407 @findex -display-disable
16409 @subsubheading Synopsis
16412 -display-disable @var{number}
16415 Disable display @var{number}.
16417 @subsubheading @value{GDBN} Command
16419 The corresponding @value{GDBN} command is @samp{disable display}.
16421 @subsubheading Example
16425 @subheading The @code{-display-enable} Command
16426 @findex -display-enable
16428 @subsubheading Synopsis
16431 -display-enable @var{number}
16434 Enable display @var{number}.
16436 @subsubheading @value{GDBN} Command
16438 The corresponding @value{GDBN} command is @samp{enable display}.
16440 @subsubheading Example
16444 @subheading The @code{-display-insert} Command
16445 @findex -display-insert
16447 @subsubheading Synopsis
16450 -display-insert @var{expression}
16453 Display @var{expression} every time the program stops.
16455 @subsubheading @value{GDBN} Command
16457 The corresponding @value{GDBN} command is @samp{display}.
16459 @subsubheading Example
16463 @subheading The @code{-display-list} Command
16464 @findex -display-list
16466 @subsubheading Synopsis
16472 List the displays. Do not show the current values.
16474 @subsubheading @value{GDBN} Command
16476 The corresponding @value{GDBN} command is @samp{info display}.
16478 @subsubheading Example
16482 @subheading The @code{-environment-cd} Command
16483 @findex -environment-cd
16485 @subsubheading Synopsis
16488 -environment-cd @var{pathdir}
16491 Set @value{GDBN}'s working directory.
16493 @subsubheading @value{GDBN} Command
16495 The corresponding @value{GDBN} command is @samp{cd}.
16497 @subsubheading Example
16501 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
16507 @subheading The @code{-environment-directory} Command
16508 @findex -environment-directory
16510 @subsubheading Synopsis
16513 -environment-directory [ -r ] [ @var{pathdir} ]+
16516 Add directories @var{pathdir} to beginning of search path for source files.
16517 If the @samp{-r} option is used, the search path is reset to the default
16518 search path. If directories @var{pathdir} are supplied in addition to the
16519 @samp{-r} option, the search path is first reset and then addition
16521 Multiple directories may be specified, separated by blanks. Specifying
16522 multiple directories in a single command
16523 results in the directories added to the beginning of the
16524 search path in the same order they were presented in the command.
16525 If blanks are needed as
16526 part of a directory name, double-quotes should be used around
16527 the name. In the command output, the path will show up separated
16528 by the system directory-separator character. The directory-seperator
16529 character must not be used
16530 in any directory name.
16531 If no directories are specified, the current search path is displayed.
16533 @subsubheading @value{GDBN} Command
16535 The corresponding @value{GDBN} command is @samp{dir}.
16537 @subsubheading Example
16541 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
16542 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
16544 -environment-directory ""
16545 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
16547 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
16548 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
16550 -environment-directory -r
16551 ^done,source-path="$cdir:$cwd"
16556 @subheading The @code{-environment-path} Command
16557 @findex -environment-path
16559 @subsubheading Synopsis
16562 -environment-path [ -r ] [ @var{pathdir} ]+
16565 Add directories @var{pathdir} to beginning of search path for object files.
16566 If the @samp{-r} option is used, the search path is reset to the original
16567 search path that existed at gdb start-up. If directories @var{pathdir} are
16568 supplied in addition to the
16569 @samp{-r} option, the search path is first reset and then addition
16571 Multiple directories may be specified, separated by blanks. Specifying
16572 multiple directories in a single command
16573 results in the directories added to the beginning of the
16574 search path in the same order they were presented in the command.
16575 If blanks are needed as
16576 part of a directory name, double-quotes should be used around
16577 the name. In the command output, the path will show up separated
16578 by the system directory-separator character. The directory-seperator
16579 character must not be used
16580 in any directory name.
16581 If no directories are specified, the current path is displayed.
16584 @subsubheading @value{GDBN} Command
16586 The corresponding @value{GDBN} command is @samp{path}.
16588 @subsubheading Example
16593 ^done,path="/usr/bin"
16595 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
16596 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
16598 -environment-path -r /usr/local/bin
16599 ^done,path="/usr/local/bin:/usr/bin"
16604 @subheading The @code{-environment-pwd} Command
16605 @findex -environment-pwd
16607 @subsubheading Synopsis
16613 Show the current working directory.
16615 @subsubheading @value{GDBN} command
16617 The corresponding @value{GDBN} command is @samp{pwd}.
16619 @subsubheading Example
16624 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
16628 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16629 @node GDB/MI Program Control
16630 @section @sc{gdb/mi} Program control
16632 @subsubheading Program termination
16634 As a result of execution, the inferior program can run to completion, if
16635 it doesn't encounter any breakpoints. In this case the output will
16636 include an exit code, if the program has exited exceptionally.
16638 @subsubheading Examples
16641 Program exited normally:
16649 *stopped,reason="exited-normally"
16654 Program exited exceptionally:
16662 *stopped,reason="exited",exit-code="01"
16666 Another way the program can terminate is if it receives a signal such as
16667 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
16671 *stopped,reason="exited-signalled",signal-name="SIGINT",
16672 signal-meaning="Interrupt"
16676 @subheading The @code{-exec-abort} Command
16677 @findex -exec-abort
16679 @subsubheading Synopsis
16685 Kill the inferior running program.
16687 @subsubheading @value{GDBN} Command
16689 The corresponding @value{GDBN} command is @samp{kill}.
16691 @subsubheading Example
16695 @subheading The @code{-exec-arguments} Command
16696 @findex -exec-arguments
16698 @subsubheading Synopsis
16701 -exec-arguments @var{args}
16704 Set the inferior program arguments, to be used in the next
16707 @subsubheading @value{GDBN} Command
16709 The corresponding @value{GDBN} command is @samp{set args}.
16711 @subsubheading Example
16714 Don't have one around.
16717 @subheading The @code{-exec-continue} Command
16718 @findex -exec-continue
16720 @subsubheading Synopsis
16726 Asynchronous command. Resumes the execution of the inferior program
16727 until a breakpoint is encountered, or until the inferior exits.
16729 @subsubheading @value{GDBN} Command
16731 The corresponding @value{GDBN} corresponding is @samp{continue}.
16733 @subsubheading Example
16740 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
16741 file="hello.c",line="13"@}
16746 @subheading The @code{-exec-finish} Command
16747 @findex -exec-finish
16749 @subsubheading Synopsis
16755 Asynchronous command. Resumes the execution of the inferior program
16756 until the current function is exited. Displays the results returned by
16759 @subsubheading @value{GDBN} Command
16761 The corresponding @value{GDBN} command is @samp{finish}.
16763 @subsubheading Example
16765 Function returning @code{void}.
16772 *stopped,reason="function-finished",frame=@{func="main",args=[],
16773 file="hello.c",line="7"@}
16777 Function returning other than @code{void}. The name of the internal
16778 @value{GDBN} variable storing the result is printed, together with the
16785 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
16786 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
16787 file="recursive2.c",line="14"@},
16788 gdb-result-var="$1",return-value="0"
16793 @subheading The @code{-exec-interrupt} Command
16794 @findex -exec-interrupt
16796 @subsubheading Synopsis
16802 Asynchronous command. Interrupts the background execution of the target.
16803 Note how the token associated with the stop message is the one for the
16804 execution command that has been interrupted. The token for the interrupt
16805 itself only appears in the @samp{^done} output. If the user is trying to
16806 interrupt a non-running program, an error message will be printed.
16808 @subsubheading @value{GDBN} Command
16810 The corresponding @value{GDBN} command is @samp{interrupt}.
16812 @subsubheading Example
16823 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
16824 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",line="13"@}
16829 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
16834 @subheading The @code{-exec-next} Command
16837 @subsubheading Synopsis
16843 Asynchronous command. Resumes execution of the inferior program, stopping
16844 when the beginning of the next source line is reached.
16846 @subsubheading @value{GDBN} Command
16848 The corresponding @value{GDBN} command is @samp{next}.
16850 @subsubheading Example
16856 *stopped,reason="end-stepping-range",line="8",file="hello.c"
16861 @subheading The @code{-exec-next-instruction} Command
16862 @findex -exec-next-instruction
16864 @subsubheading Synopsis
16867 -exec-next-instruction
16870 Asynchronous command. Executes one machine instruction. If the
16871 instruction is a function call continues until the function returns. If
16872 the program stops at an instruction in the middle of a source line, the
16873 address will be printed as well.
16875 @subsubheading @value{GDBN} Command
16877 The corresponding @value{GDBN} command is @samp{nexti}.
16879 @subsubheading Example
16883 -exec-next-instruction
16887 *stopped,reason="end-stepping-range",
16888 addr="0x000100d4",line="5",file="hello.c"
16893 @subheading The @code{-exec-return} Command
16894 @findex -exec-return
16896 @subsubheading Synopsis
16902 Makes current function return immediately. Doesn't execute the inferior.
16903 Displays the new current frame.
16905 @subsubheading @value{GDBN} Command
16907 The corresponding @value{GDBN} command is @samp{return}.
16909 @subsubheading Example
16913 200-break-insert callee4
16914 200^done,bkpt=@{number="1",addr="0x00010734",
16915 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
16920 000*stopped,reason="breakpoint-hit",bkptno="1",
16921 frame=@{func="callee4",args=[],
16922 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
16928 111^done,frame=@{level="0",func="callee3",
16929 args=[@{name="strarg",
16930 value="0x11940 \"A string argument.\""@}],
16931 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
16936 @subheading The @code{-exec-run} Command
16939 @subsubheading Synopsis
16945 Asynchronous command. Starts execution of the inferior from the
16946 beginning. The inferior executes until either a breakpoint is
16947 encountered or the program exits.
16949 @subsubheading @value{GDBN} Command
16951 The corresponding @value{GDBN} command is @samp{run}.
16953 @subsubheading Example
16958 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
16963 *stopped,reason="breakpoint-hit",bkptno="1",
16964 frame=@{func="main",args=[],file="recursive2.c",line="4"@}
16969 @subheading The @code{-exec-show-arguments} Command
16970 @findex -exec-show-arguments
16972 @subsubheading Synopsis
16975 -exec-show-arguments
16978 Print the arguments of the program.
16980 @subsubheading @value{GDBN} Command
16982 The corresponding @value{GDBN} command is @samp{show args}.
16984 @subsubheading Example
16987 @c @subheading -exec-signal
16989 @subheading The @code{-exec-step} Command
16992 @subsubheading Synopsis
16998 Asynchronous command. Resumes execution of the inferior program, stopping
16999 when the beginning of the next source line is reached, if the next
17000 source line is not a function call. If it is, stop at the first
17001 instruction of the called function.
17003 @subsubheading @value{GDBN} Command
17005 The corresponding @value{GDBN} command is @samp{step}.
17007 @subsubheading Example
17009 Stepping into a function:
17015 *stopped,reason="end-stepping-range",
17016 frame=@{func="foo",args=[@{name="a",value="10"@},
17017 @{name="b",value="0"@}],file="recursive2.c",line="11"@}
17027 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
17032 @subheading The @code{-exec-step-instruction} Command
17033 @findex -exec-step-instruction
17035 @subsubheading Synopsis
17038 -exec-step-instruction
17041 Asynchronous command. Resumes the inferior which executes one machine
17042 instruction. The output, once @value{GDBN} has stopped, will vary depending on
17043 whether we have stopped in the middle of a source line or not. In the
17044 former case, the address at which the program stopped will be printed as
17047 @subsubheading @value{GDBN} Command
17049 The corresponding @value{GDBN} command is @samp{stepi}.
17051 @subsubheading Example
17055 -exec-step-instruction
17059 *stopped,reason="end-stepping-range",
17060 frame=@{func="foo",args=[],file="try.c",line="10"@}
17062 -exec-step-instruction
17066 *stopped,reason="end-stepping-range",
17067 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",line="10"@}
17072 @subheading The @code{-exec-until} Command
17073 @findex -exec-until
17075 @subsubheading Synopsis
17078 -exec-until [ @var{location} ]
17081 Asynchronous command. Executes the inferior until the @var{location}
17082 specified in the argument is reached. If there is no argument, the inferior
17083 executes until a source line greater than the current one is reached.
17084 The reason for stopping in this case will be @samp{location-reached}.
17086 @subsubheading @value{GDBN} Command
17088 The corresponding @value{GDBN} command is @samp{until}.
17090 @subsubheading Example
17094 -exec-until recursive2.c:6
17098 *stopped,reason="location-reached",frame=@{func="main",args=[],
17099 file="recursive2.c",line="6"@}
17104 @subheading -file-clear
17105 Is this going away????
17109 @subheading The @code{-file-exec-and-symbols} Command
17110 @findex -file-exec-and-symbols
17112 @subsubheading Synopsis
17115 -file-exec-and-symbols @var{file}
17118 Specify the executable file to be debugged. This file is the one from
17119 which the symbol table is also read. If no file is specified, the
17120 command clears the executable and symbol information. If breakpoints
17121 are set when using this command with no arguments, @value{GDBN} will produce
17122 error messages. Otherwise, no output is produced, except a completion
17125 @subsubheading @value{GDBN} Command
17127 The corresponding @value{GDBN} command is @samp{file}.
17129 @subsubheading Example
17133 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
17139 @subheading The @code{-file-exec-file} Command
17140 @findex -file-exec-file
17142 @subsubheading Synopsis
17145 -file-exec-file @var{file}
17148 Specify the executable file to be debugged. Unlike
17149 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
17150 from this file. If used without argument, @value{GDBN} clears the information
17151 about the executable file. No output is produced, except a completion
17154 @subsubheading @value{GDBN} Command
17156 The corresponding @value{GDBN} command is @samp{exec-file}.
17158 @subsubheading Example
17162 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
17168 @subheading The @code{-file-list-exec-sections} Command
17169 @findex -file-list-exec-sections
17171 @subsubheading Synopsis
17174 -file-list-exec-sections
17177 List the sections of the current executable file.
17179 @subsubheading @value{GDBN} Command
17181 The @value{GDBN} command @samp{info file} shows, among the rest, the same
17182 information as this command. @code{gdbtk} has a corresponding command
17183 @samp{gdb_load_info}.
17185 @subsubheading Example
17189 @subheading The @code{-file-list-exec-source-file} Command
17190 @findex -file-list-exec-source-file
17192 @subsubheading Synopsis
17195 -file-list-exec-source-file
17198 List the line number, the current source file, and the absolute path
17199 to the current source file for the current executable.
17201 @subsubheading @value{GDBN} Command
17203 There's no @value{GDBN} command which directly corresponds to this one.
17205 @subsubheading Example
17209 123-file-list-exec-source-file
17210 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
17215 @subheading The @code{-file-list-exec-source-files} Command
17216 @findex -file-list-exec-source-files
17218 @subsubheading Synopsis
17221 -file-list-exec-source-files
17224 List the source files for the current executable.
17226 It will always output the filename, but only when GDB can find the absolute
17227 file name of a source file, will it output the fullname.
17229 @subsubheading @value{GDBN} Command
17231 There's no @value{GDBN} command which directly corresponds to this one.
17232 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
17234 @subsubheading Example
17237 -file-list-exec-source-files
17239 @{file=foo.c,fullname=/home/foo.c@},
17240 @{file=/home/bar.c,fullname=/home/bar.c@},
17241 @{file=gdb_could_not_find_fullpath.c@}]
17245 @subheading The @code{-file-list-shared-libraries} Command
17246 @findex -file-list-shared-libraries
17248 @subsubheading Synopsis
17251 -file-list-shared-libraries
17254 List the shared libraries in the program.
17256 @subsubheading @value{GDBN} Command
17258 The corresponding @value{GDBN} command is @samp{info shared}.
17260 @subsubheading Example
17264 @subheading The @code{-file-list-symbol-files} Command
17265 @findex -file-list-symbol-files
17267 @subsubheading Synopsis
17270 -file-list-symbol-files
17275 @subsubheading @value{GDBN} Command
17277 The corresponding @value{GDBN} command is @samp{info file} (part of it).
17279 @subsubheading Example
17283 @subheading The @code{-file-symbol-file} Command
17284 @findex -file-symbol-file
17286 @subsubheading Synopsis
17289 -file-symbol-file @var{file}
17292 Read symbol table info from the specified @var{file} argument. When
17293 used without arguments, clears @value{GDBN}'s symbol table info. No output is
17294 produced, except for a completion notification.
17296 @subsubheading @value{GDBN} Command
17298 The corresponding @value{GDBN} command is @samp{symbol-file}.
17300 @subsubheading Example
17304 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
17309 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17310 @node GDB/MI Miscellaneous Commands
17311 @section Miscellaneous @value{GDBN} commands in @sc{gdb/mi}
17313 @c @subheading -gdb-complete
17315 @subheading The @code{-gdb-exit} Command
17318 @subsubheading Synopsis
17324 Exit @value{GDBN} immediately.
17326 @subsubheading @value{GDBN} Command
17328 Approximately corresponds to @samp{quit}.
17330 @subsubheading Example
17337 @subheading The @code{-gdb-set} Command
17340 @subsubheading Synopsis
17346 Set an internal @value{GDBN} variable.
17347 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
17349 @subsubheading @value{GDBN} Command
17351 The corresponding @value{GDBN} command is @samp{set}.
17353 @subsubheading Example
17363 @subheading The @code{-gdb-show} Command
17366 @subsubheading Synopsis
17372 Show the current value of a @value{GDBN} variable.
17374 @subsubheading @value{GDBN} command
17376 The corresponding @value{GDBN} command is @samp{show}.
17378 @subsubheading Example
17387 @c @subheading -gdb-source
17390 @subheading The @code{-gdb-version} Command
17391 @findex -gdb-version
17393 @subsubheading Synopsis
17399 Show version information for @value{GDBN}. Used mostly in testing.
17401 @subsubheading @value{GDBN} Command
17403 There's no equivalent @value{GDBN} command. @value{GDBN} by default shows this
17404 information when you start an interactive session.
17406 @subsubheading Example
17408 @c This example modifies the actual output from GDB to avoid overfull
17414 ~Copyright 2000 Free Software Foundation, Inc.
17415 ~GDB is free software, covered by the GNU General Public License, and
17416 ~you are welcome to change it and/or distribute copies of it under
17417 ~ certain conditions.
17418 ~Type "show copying" to see the conditions.
17419 ~There is absolutely no warranty for GDB. Type "show warranty" for
17421 ~This GDB was configured as
17422 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
17427 @subheading The @code{-interpreter-exec} Command
17428 @findex -interpreter-exec
17430 @subheading Synopsis
17433 -interpreter-exec @var{interpreter} @var{command}
17436 Execute the specified @var{command} in the given @var{interpreter}.
17438 @subheading @value{GDBN} Command
17440 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
17442 @subheading Example
17446 -interpreter-exec console "break main"
17447 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
17448 &"During symbol reading, bad structure-type format.\n"
17449 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
17455 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17456 @node GDB/MI Kod Commands
17457 @section @sc{gdb/mi} Kod Commands
17459 The Kod commands are not implemented.
17461 @c @subheading -kod-info
17463 @c @subheading -kod-list
17465 @c @subheading -kod-list-object-types
17467 @c @subheading -kod-show
17469 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17470 @node GDB/MI Memory Overlay Commands
17471 @section @sc{gdb/mi} Memory Overlay Commands
17473 The memory overlay commands are not implemented.
17475 @c @subheading -overlay-auto
17477 @c @subheading -overlay-list-mapping-state
17479 @c @subheading -overlay-list-overlays
17481 @c @subheading -overlay-map
17483 @c @subheading -overlay-off
17485 @c @subheading -overlay-on
17487 @c @subheading -overlay-unmap
17489 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17490 @node GDB/MI Signal Handling Commands
17491 @section @sc{gdb/mi} Signal Handling Commands
17493 Signal handling commands are not implemented.
17495 @c @subheading -signal-handle
17497 @c @subheading -signal-list-handle-actions
17499 @c @subheading -signal-list-signal-types
17503 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17504 @node GDB/MI Stack Manipulation
17505 @section @sc{gdb/mi} Stack Manipulation Commands
17508 @subheading The @code{-stack-info-frame} Command
17509 @findex -stack-info-frame
17511 @subsubheading Synopsis
17517 Get info on the current frame.
17519 @subsubheading @value{GDBN} Command
17521 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
17522 (without arguments).
17524 @subsubheading Example
17527 @subheading The @code{-stack-info-depth} Command
17528 @findex -stack-info-depth
17530 @subsubheading Synopsis
17533 -stack-info-depth [ @var{max-depth} ]
17536 Return the depth of the stack. If the integer argument @var{max-depth}
17537 is specified, do not count beyond @var{max-depth} frames.
17539 @subsubheading @value{GDBN} Command
17541 There's no equivalent @value{GDBN} command.
17543 @subsubheading Example
17545 For a stack with frame levels 0 through 11:
17552 -stack-info-depth 4
17555 -stack-info-depth 12
17558 -stack-info-depth 11
17561 -stack-info-depth 13
17566 @subheading The @code{-stack-list-arguments} Command
17567 @findex -stack-list-arguments
17569 @subsubheading Synopsis
17572 -stack-list-arguments @var{show-values}
17573 [ @var{low-frame} @var{high-frame} ]
17576 Display a list of the arguments for the frames between @var{low-frame}
17577 and @var{high-frame} (inclusive). If @var{low-frame} and
17578 @var{high-frame} are not provided, list the arguments for the whole call
17581 The @var{show-values} argument must have a value of 0 or 1. A value of
17582 0 means that only the names of the arguments are listed, a value of 1
17583 means that both names and values of the arguments are printed.
17585 @subsubheading @value{GDBN} Command
17587 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
17588 @samp{gdb_get_args} command which partially overlaps with the
17589 functionality of @samp{-stack-list-arguments}.
17591 @subsubheading Example
17598 frame=@{level="0",addr="0x00010734",func="callee4",
17599 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
17600 frame=@{level="1",addr="0x0001076c",func="callee3",
17601 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
17602 frame=@{level="2",addr="0x0001078c",func="callee2",
17603 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
17604 frame=@{level="3",addr="0x000107b4",func="callee1",
17605 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
17606 frame=@{level="4",addr="0x000107e0",func="main",
17607 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
17609 -stack-list-arguments 0
17612 frame=@{level="0",args=[]@},
17613 frame=@{level="1",args=[name="strarg"]@},
17614 frame=@{level="2",args=[name="intarg",name="strarg"]@},
17615 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
17616 frame=@{level="4",args=[]@}]
17618 -stack-list-arguments 1
17621 frame=@{level="0",args=[]@},
17623 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
17624 frame=@{level="2",args=[
17625 @{name="intarg",value="2"@},
17626 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
17627 @{frame=@{level="3",args=[
17628 @{name="intarg",value="2"@},
17629 @{name="strarg",value="0x11940 \"A string argument.\""@},
17630 @{name="fltarg",value="3.5"@}]@},
17631 frame=@{level="4",args=[]@}]
17633 -stack-list-arguments 0 2 2
17634 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
17636 -stack-list-arguments 1 2 2
17637 ^done,stack-args=[frame=@{level="2",
17638 args=[@{name="intarg",value="2"@},
17639 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
17643 @c @subheading -stack-list-exception-handlers
17646 @subheading The @code{-stack-list-frames} Command
17647 @findex -stack-list-frames
17649 @subsubheading Synopsis
17652 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
17655 List the frames currently on the stack. For each frame it displays the
17660 The frame number, 0 being the topmost frame, i.e. the innermost function.
17662 The @code{$pc} value for that frame.
17666 File name of the source file where the function lives.
17668 Line number corresponding to the @code{$pc}.
17671 If invoked without arguments, this command prints a backtrace for the
17672 whole stack. If given two integer arguments, it shows the frames whose
17673 levels are between the two arguments (inclusive). If the two arguments
17674 are equal, it shows the single frame at the corresponding level.
17676 @subsubheading @value{GDBN} Command
17678 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
17680 @subsubheading Example
17682 Full stack backtrace:
17688 [frame=@{level="0",addr="0x0001076c",func="foo",
17689 file="recursive2.c",line="11"@},
17690 frame=@{level="1",addr="0x000107a4",func="foo",
17691 file="recursive2.c",line="14"@},
17692 frame=@{level="2",addr="0x000107a4",func="foo",
17693 file="recursive2.c",line="14"@},
17694 frame=@{level="3",addr="0x000107a4",func="foo",
17695 file="recursive2.c",line="14"@},
17696 frame=@{level="4",addr="0x000107a4",func="foo",
17697 file="recursive2.c",line="14"@},
17698 frame=@{level="5",addr="0x000107a4",func="foo",
17699 file="recursive2.c",line="14"@},
17700 frame=@{level="6",addr="0x000107a4",func="foo",
17701 file="recursive2.c",line="14"@},
17702 frame=@{level="7",addr="0x000107a4",func="foo",
17703 file="recursive2.c",line="14"@},
17704 frame=@{level="8",addr="0x000107a4",func="foo",
17705 file="recursive2.c",line="14"@},
17706 frame=@{level="9",addr="0x000107a4",func="foo",
17707 file="recursive2.c",line="14"@},
17708 frame=@{level="10",addr="0x000107a4",func="foo",
17709 file="recursive2.c",line="14"@},
17710 frame=@{level="11",addr="0x00010738",func="main",
17711 file="recursive2.c",line="4"@}]
17715 Show frames between @var{low_frame} and @var{high_frame}:
17719 -stack-list-frames 3 5
17721 [frame=@{level="3",addr="0x000107a4",func="foo",
17722 file="recursive2.c",line="14"@},
17723 frame=@{level="4",addr="0x000107a4",func="foo",
17724 file="recursive2.c",line="14"@},
17725 frame=@{level="5",addr="0x000107a4",func="foo",
17726 file="recursive2.c",line="14"@}]
17730 Show a single frame:
17734 -stack-list-frames 3 3
17736 [frame=@{level="3",addr="0x000107a4",func="foo",
17737 file="recursive2.c",line="14"@}]
17742 @subheading The @code{-stack-list-locals} Command
17743 @findex -stack-list-locals
17745 @subsubheading Synopsis
17748 -stack-list-locals @var{print-values}
17751 Display the local variable names for the current frame. With an
17752 argument of 0 or @code{--no-values}, prints only the names of the variables.
17753 With argument of 1 or @code{--all-values}, prints also their values. With
17754 argument of 2 or @code{--simple-values}, prints the name, type and value for
17755 simple data types and the name and type for arrays, structures and
17756 unions. In this last case, the idea is that the user can see the
17757 value of simple data types immediately and he can create variable
17758 objects for other data types if he wishes to explore their values in
17761 @subsubheading @value{GDBN} Command
17763 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
17765 @subsubheading Example
17769 -stack-list-locals 0
17770 ^done,locals=[name="A",name="B",name="C"]
17772 -stack-list-locals --all-values
17773 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
17774 @{name="C",value="@{1, 2, 3@}"@}]
17775 -stack-list-locals --simple-values
17776 ^done,locals=[@{name="A",type="int",value="1"@},
17777 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
17782 @subheading The @code{-stack-select-frame} Command
17783 @findex -stack-select-frame
17785 @subsubheading Synopsis
17788 -stack-select-frame @var{framenum}
17791 Change the current frame. Select a different frame @var{framenum} on
17794 @subsubheading @value{GDBN} Command
17796 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
17797 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
17799 @subsubheading Example
17803 -stack-select-frame 2
17808 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17809 @node GDB/MI Symbol Query
17810 @section @sc{gdb/mi} Symbol Query Commands
17813 @subheading The @code{-symbol-info-address} Command
17814 @findex -symbol-info-address
17816 @subsubheading Synopsis
17819 -symbol-info-address @var{symbol}
17822 Describe where @var{symbol} is stored.
17824 @subsubheading @value{GDBN} Command
17826 The corresponding @value{GDBN} command is @samp{info address}.
17828 @subsubheading Example
17832 @subheading The @code{-symbol-info-file} Command
17833 @findex -symbol-info-file
17835 @subsubheading Synopsis
17841 Show the file for the symbol.
17843 @subsubheading @value{GDBN} Command
17845 There's no equivalent @value{GDBN} command. @code{gdbtk} has
17846 @samp{gdb_find_file}.
17848 @subsubheading Example
17852 @subheading The @code{-symbol-info-function} Command
17853 @findex -symbol-info-function
17855 @subsubheading Synopsis
17858 -symbol-info-function
17861 Show which function the symbol lives in.
17863 @subsubheading @value{GDBN} Command
17865 @samp{gdb_get_function} in @code{gdbtk}.
17867 @subsubheading Example
17871 @subheading The @code{-symbol-info-line} Command
17872 @findex -symbol-info-line
17874 @subsubheading Synopsis
17880 Show the core addresses of the code for a source line.
17882 @subsubheading @value{GDBN} Command
17884 The corresponding @value{GDBN} command is @samp{info line}.
17885 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
17887 @subsubheading Example
17891 @subheading The @code{-symbol-info-symbol} Command
17892 @findex -symbol-info-symbol
17894 @subsubheading Synopsis
17897 -symbol-info-symbol @var{addr}
17900 Describe what symbol is at location @var{addr}.
17902 @subsubheading @value{GDBN} Command
17904 The corresponding @value{GDBN} command is @samp{info symbol}.
17906 @subsubheading Example
17910 @subheading The @code{-symbol-list-functions} Command
17911 @findex -symbol-list-functions
17913 @subsubheading Synopsis
17916 -symbol-list-functions
17919 List the functions in the executable.
17921 @subsubheading @value{GDBN} Command
17923 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
17924 @samp{gdb_search} in @code{gdbtk}.
17926 @subsubheading Example
17930 @subheading The @code{-symbol-list-lines} Command
17931 @findex -symbol-list-lines
17933 @subsubheading Synopsis
17936 -symbol-list-lines @var{filename}
17939 Print the list of lines that contain code and their associated program
17940 addresses for the given source filename. The entries are sorted in
17941 ascending PC order.
17943 @subsubheading @value{GDBN} Command
17945 There is no corresponding @value{GDBN} command.
17947 @subsubheading Example
17950 -symbol-list-lines basics.c
17951 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
17956 @subheading The @code{-symbol-list-types} Command
17957 @findex -symbol-list-types
17959 @subsubheading Synopsis
17965 List all the type names.
17967 @subsubheading @value{GDBN} Command
17969 The corresponding commands are @samp{info types} in @value{GDBN},
17970 @samp{gdb_search} in @code{gdbtk}.
17972 @subsubheading Example
17976 @subheading The @code{-symbol-list-variables} Command
17977 @findex -symbol-list-variables
17979 @subsubheading Synopsis
17982 -symbol-list-variables
17985 List all the global and static variable names.
17987 @subsubheading @value{GDBN} Command
17989 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
17991 @subsubheading Example
17995 @subheading The @code{-symbol-locate} Command
17996 @findex -symbol-locate
17998 @subsubheading Synopsis
18004 @subsubheading @value{GDBN} Command
18006 @samp{gdb_loc} in @code{gdbtk}.
18008 @subsubheading Example
18012 @subheading The @code{-symbol-type} Command
18013 @findex -symbol-type
18015 @subsubheading Synopsis
18018 -symbol-type @var{variable}
18021 Show type of @var{variable}.
18023 @subsubheading @value{GDBN} Command
18025 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
18026 @samp{gdb_obj_variable}.
18028 @subsubheading Example
18032 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18033 @node GDB/MI Target Manipulation
18034 @section @sc{gdb/mi} Target Manipulation Commands
18037 @subheading The @code{-target-attach} Command
18038 @findex -target-attach
18040 @subsubheading Synopsis
18043 -target-attach @var{pid} | @var{file}
18046 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
18048 @subsubheading @value{GDBN} command
18050 The corresponding @value{GDBN} command is @samp{attach}.
18052 @subsubheading Example
18056 @subheading The @code{-target-compare-sections} Command
18057 @findex -target-compare-sections
18059 @subsubheading Synopsis
18062 -target-compare-sections [ @var{section} ]
18065 Compare data of section @var{section} on target to the exec file.
18066 Without the argument, all sections are compared.
18068 @subsubheading @value{GDBN} Command
18070 The @value{GDBN} equivalent is @samp{compare-sections}.
18072 @subsubheading Example
18076 @subheading The @code{-target-detach} Command
18077 @findex -target-detach
18079 @subsubheading Synopsis
18085 Disconnect from the remote target. There's no output.
18087 @subsubheading @value{GDBN} command
18089 The corresponding @value{GDBN} command is @samp{detach}.
18091 @subsubheading Example
18101 @subheading The @code{-target-disconnect} Command
18102 @findex -target-disconnect
18104 @subsubheading Synopsis
18110 Disconnect from the remote target. There's no output.
18112 @subsubheading @value{GDBN} command
18114 The corresponding @value{GDBN} command is @samp{disconnect}.
18116 @subsubheading Example
18126 @subheading The @code{-target-download} Command
18127 @findex -target-download
18129 @subsubheading Synopsis
18135 Loads the executable onto the remote target.
18136 It prints out an update message every half second, which includes the fields:
18140 The name of the section.
18142 The size of what has been sent so far for that section.
18144 The size of the section.
18146 The total size of what was sent so far (the current and the previous sections).
18148 The size of the overall executable to download.
18152 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
18153 @sc{gdb/mi} Output Syntax}).
18155 In addition, it prints the name and size of the sections, as they are
18156 downloaded. These messages include the following fields:
18160 The name of the section.
18162 The size of the section.
18164 The size of the overall executable to download.
18168 At the end, a summary is printed.
18170 @subsubheading @value{GDBN} Command
18172 The corresponding @value{GDBN} command is @samp{load}.
18174 @subsubheading Example
18176 Note: each status message appears on a single line. Here the messages
18177 have been broken down so that they can fit onto a page.
18182 +download,@{section=".text",section-size="6668",total-size="9880"@}
18183 +download,@{section=".text",section-sent="512",section-size="6668",
18184 total-sent="512",total-size="9880"@}
18185 +download,@{section=".text",section-sent="1024",section-size="6668",
18186 total-sent="1024",total-size="9880"@}
18187 +download,@{section=".text",section-sent="1536",section-size="6668",
18188 total-sent="1536",total-size="9880"@}
18189 +download,@{section=".text",section-sent="2048",section-size="6668",
18190 total-sent="2048",total-size="9880"@}
18191 +download,@{section=".text",section-sent="2560",section-size="6668",
18192 total-sent="2560",total-size="9880"@}
18193 +download,@{section=".text",section-sent="3072",section-size="6668",
18194 total-sent="3072",total-size="9880"@}
18195 +download,@{section=".text",section-sent="3584",section-size="6668",
18196 total-sent="3584",total-size="9880"@}
18197 +download,@{section=".text",section-sent="4096",section-size="6668",
18198 total-sent="4096",total-size="9880"@}
18199 +download,@{section=".text",section-sent="4608",section-size="6668",
18200 total-sent="4608",total-size="9880"@}
18201 +download,@{section=".text",section-sent="5120",section-size="6668",
18202 total-sent="5120",total-size="9880"@}
18203 +download,@{section=".text",section-sent="5632",section-size="6668",
18204 total-sent="5632",total-size="9880"@}
18205 +download,@{section=".text",section-sent="6144",section-size="6668",
18206 total-sent="6144",total-size="9880"@}
18207 +download,@{section=".text",section-sent="6656",section-size="6668",
18208 total-sent="6656",total-size="9880"@}
18209 +download,@{section=".init",section-size="28",total-size="9880"@}
18210 +download,@{section=".fini",section-size="28",total-size="9880"@}
18211 +download,@{section=".data",section-size="3156",total-size="9880"@}
18212 +download,@{section=".data",section-sent="512",section-size="3156",
18213 total-sent="7236",total-size="9880"@}
18214 +download,@{section=".data",section-sent="1024",section-size="3156",
18215 total-sent="7748",total-size="9880"@}
18216 +download,@{section=".data",section-sent="1536",section-size="3156",
18217 total-sent="8260",total-size="9880"@}
18218 +download,@{section=".data",section-sent="2048",section-size="3156",
18219 total-sent="8772",total-size="9880"@}
18220 +download,@{section=".data",section-sent="2560",section-size="3156",
18221 total-sent="9284",total-size="9880"@}
18222 +download,@{section=".data",section-sent="3072",section-size="3156",
18223 total-sent="9796",total-size="9880"@}
18224 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
18230 @subheading The @code{-target-exec-status} Command
18231 @findex -target-exec-status
18233 @subsubheading Synopsis
18236 -target-exec-status
18239 Provide information on the state of the target (whether it is running or
18240 not, for instance).
18242 @subsubheading @value{GDBN} Command
18244 There's no equivalent @value{GDBN} command.
18246 @subsubheading Example
18250 @subheading The @code{-target-list-available-targets} Command
18251 @findex -target-list-available-targets
18253 @subsubheading Synopsis
18256 -target-list-available-targets
18259 List the possible targets to connect to.
18261 @subsubheading @value{GDBN} Command
18263 The corresponding @value{GDBN} command is @samp{help target}.
18265 @subsubheading Example
18269 @subheading The @code{-target-list-current-targets} Command
18270 @findex -target-list-current-targets
18272 @subsubheading Synopsis
18275 -target-list-current-targets
18278 Describe the current target.
18280 @subsubheading @value{GDBN} Command
18282 The corresponding information is printed by @samp{info file} (among
18285 @subsubheading Example
18289 @subheading The @code{-target-list-parameters} Command
18290 @findex -target-list-parameters
18292 @subsubheading Synopsis
18295 -target-list-parameters
18300 @subsubheading @value{GDBN} Command
18304 @subsubheading Example
18308 @subheading The @code{-target-select} Command
18309 @findex -target-select
18311 @subsubheading Synopsis
18314 -target-select @var{type} @var{parameters @dots{}}
18317 Connect @value{GDBN} to the remote target. This command takes two args:
18321 The type of target, for instance @samp{async}, @samp{remote}, etc.
18322 @item @var{parameters}
18323 Device names, host names and the like. @xref{Target Commands, ,
18324 Commands for managing targets}, for more details.
18327 The output is a connection notification, followed by the address at
18328 which the target program is, in the following form:
18331 ^connected,addr="@var{address}",func="@var{function name}",
18332 args=[@var{arg list}]
18335 @subsubheading @value{GDBN} Command
18337 The corresponding @value{GDBN} command is @samp{target}.
18339 @subsubheading Example
18343 -target-select async /dev/ttya
18344 ^connected,addr="0xfe00a300",func="??",args=[]
18348 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18349 @node GDB/MI Thread Commands
18350 @section @sc{gdb/mi} Thread Commands
18353 @subheading The @code{-thread-info} Command
18354 @findex -thread-info
18356 @subsubheading Synopsis
18362 @subsubheading @value{GDBN} command
18366 @subsubheading Example
18370 @subheading The @code{-thread-list-all-threads} Command
18371 @findex -thread-list-all-threads
18373 @subsubheading Synopsis
18376 -thread-list-all-threads
18379 @subsubheading @value{GDBN} Command
18381 The equivalent @value{GDBN} command is @samp{info threads}.
18383 @subsubheading Example
18387 @subheading The @code{-thread-list-ids} Command
18388 @findex -thread-list-ids
18390 @subsubheading Synopsis
18396 Produces a list of the currently known @value{GDBN} thread ids. At the
18397 end of the list it also prints the total number of such threads.
18399 @subsubheading @value{GDBN} Command
18401 Part of @samp{info threads} supplies the same information.
18403 @subsubheading Example
18405 No threads present, besides the main process:
18410 ^done,thread-ids=@{@},number-of-threads="0"
18420 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18421 number-of-threads="3"
18426 @subheading The @code{-thread-select} Command
18427 @findex -thread-select
18429 @subsubheading Synopsis
18432 -thread-select @var{threadnum}
18435 Make @var{threadnum} the current thread. It prints the number of the new
18436 current thread, and the topmost frame for that thread.
18438 @subsubheading @value{GDBN} Command
18440 The corresponding @value{GDBN} command is @samp{thread}.
18442 @subsubheading Example
18449 *stopped,reason="end-stepping-range",thread-id="2",line="187",
18450 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
18454 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18455 number-of-threads="3"
18458 ^done,new-thread-id="3",
18459 frame=@{level="0",func="vprintf",
18460 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
18461 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
18465 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18466 @node GDB/MI Tracepoint Commands
18467 @section @sc{gdb/mi} Tracepoint Commands
18469 The tracepoint commands are not yet implemented.
18471 @c @subheading -trace-actions
18473 @c @subheading -trace-delete
18475 @c @subheading -trace-disable
18477 @c @subheading -trace-dump
18479 @c @subheading -trace-enable
18481 @c @subheading -trace-exists
18483 @c @subheading -trace-find
18485 @c @subheading -trace-frame-number
18487 @c @subheading -trace-info
18489 @c @subheading -trace-insert
18491 @c @subheading -trace-list
18493 @c @subheading -trace-pass-count
18495 @c @subheading -trace-save
18497 @c @subheading -trace-start
18499 @c @subheading -trace-stop
18502 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18503 @node GDB/MI Variable Objects
18504 @section @sc{gdb/mi} Variable Objects
18507 @subheading Motivation for Variable Objects in @sc{gdb/mi}
18509 For the implementation of a variable debugger window (locals, watched
18510 expressions, etc.), we are proposing the adaptation of the existing code
18511 used by @code{Insight}.
18513 The two main reasons for that are:
18517 It has been proven in practice (it is already on its second generation).
18520 It will shorten development time (needless to say how important it is
18524 The original interface was designed to be used by Tcl code, so it was
18525 slightly changed so it could be used through @sc{gdb/mi}. This section
18526 describes the @sc{gdb/mi} operations that will be available and gives some
18527 hints about their use.
18529 @emph{Note}: In addition to the set of operations described here, we
18530 expect the @sc{gui} implementation of a variable window to require, at
18531 least, the following operations:
18534 @item @code{-gdb-show} @code{output-radix}
18535 @item @code{-stack-list-arguments}
18536 @item @code{-stack-list-locals}
18537 @item @code{-stack-select-frame}
18540 @subheading Introduction to Variable Objects in @sc{gdb/mi}
18542 @cindex variable objects in @sc{gdb/mi}
18543 The basic idea behind variable objects is the creation of a named object
18544 to represent a variable, an expression, a memory location or even a CPU
18545 register. For each object created, a set of operations is available for
18546 examining or changing its properties.
18548 Furthermore, complex data types, such as C structures, are represented
18549 in a tree format. For instance, the @code{struct} type variable is the
18550 root and the children will represent the struct members. If a child
18551 is itself of a complex type, it will also have children of its own.
18552 Appropriate language differences are handled for C, C@t{++} and Java.
18554 When returning the actual values of the objects, this facility allows
18555 for the individual selection of the display format used in the result
18556 creation. It can be chosen among: binary, decimal, hexadecimal, octal
18557 and natural. Natural refers to a default format automatically
18558 chosen based on the variable type (like decimal for an @code{int}, hex
18559 for pointers, etc.).
18561 The following is the complete set of @sc{gdb/mi} operations defined to
18562 access this functionality:
18564 @multitable @columnfractions .4 .6
18565 @item @strong{Operation}
18566 @tab @strong{Description}
18568 @item @code{-var-create}
18569 @tab create a variable object
18570 @item @code{-var-delete}
18571 @tab delete the variable object and its children
18572 @item @code{-var-set-format}
18573 @tab set the display format of this variable
18574 @item @code{-var-show-format}
18575 @tab show the display format of this variable
18576 @item @code{-var-info-num-children}
18577 @tab tells how many children this object has
18578 @item @code{-var-list-children}
18579 @tab return a list of the object's children
18580 @item @code{-var-info-type}
18581 @tab show the type of this variable object
18582 @item @code{-var-info-expression}
18583 @tab print what this variable object represents
18584 @item @code{-var-show-attributes}
18585 @tab is this variable editable? does it exist here?
18586 @item @code{-var-evaluate-expression}
18587 @tab get the value of this variable
18588 @item @code{-var-assign}
18589 @tab set the value of this variable
18590 @item @code{-var-update}
18591 @tab update the variable and its children
18594 In the next subsection we describe each operation in detail and suggest
18595 how it can be used.
18597 @subheading Description And Use of Operations on Variable Objects
18599 @subheading The @code{-var-create} Command
18600 @findex -var-create
18602 @subsubheading Synopsis
18605 -var-create @{@var{name} | "-"@}
18606 @{@var{frame-addr} | "*"@} @var{expression}
18609 This operation creates a variable object, which allows the monitoring of
18610 a variable, the result of an expression, a memory cell or a CPU
18613 The @var{name} parameter is the string by which the object can be
18614 referenced. It must be unique. If @samp{-} is specified, the varobj
18615 system will generate a string ``varNNNNNN'' automatically. It will be
18616 unique provided that one does not specify @var{name} on that format.
18617 The command fails if a duplicate name is found.
18619 The frame under which the expression should be evaluated can be
18620 specified by @var{frame-addr}. A @samp{*} indicates that the current
18621 frame should be used.
18623 @var{expression} is any expression valid on the current language set (must not
18624 begin with a @samp{*}), or one of the following:
18628 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
18631 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
18634 @samp{$@var{regname}} --- a CPU register name
18637 @subsubheading Result
18639 This operation returns the name, number of children and the type of the
18640 object created. Type is returned as a string as the ones generated by
18641 the @value{GDBN} CLI:
18644 name="@var{name}",numchild="N",type="@var{type}"
18648 @subheading The @code{-var-delete} Command
18649 @findex -var-delete
18651 @subsubheading Synopsis
18654 -var-delete @var{name}
18657 Deletes a previously created variable object and all of its children.
18659 Returns an error if the object @var{name} is not found.
18662 @subheading The @code{-var-set-format} Command
18663 @findex -var-set-format
18665 @subsubheading Synopsis
18668 -var-set-format @var{name} @var{format-spec}
18671 Sets the output format for the value of the object @var{name} to be
18674 The syntax for the @var{format-spec} is as follows:
18677 @var{format-spec} @expansion{}
18678 @{binary | decimal | hexadecimal | octal | natural@}
18682 @subheading The @code{-var-show-format} Command
18683 @findex -var-show-format
18685 @subsubheading Synopsis
18688 -var-show-format @var{name}
18691 Returns the format used to display the value of the object @var{name}.
18694 @var{format} @expansion{}
18699 @subheading The @code{-var-info-num-children} Command
18700 @findex -var-info-num-children
18702 @subsubheading Synopsis
18705 -var-info-num-children @var{name}
18708 Returns the number of children of a variable object @var{name}:
18715 @subheading The @code{-var-list-children} Command
18716 @findex -var-list-children
18718 @subsubheading Synopsis
18721 -var-list-children [@var{print-values}] @var{name}
18724 Returns a list of the children of the specified variable object. With
18725 just the variable object name as an argument or with an optional
18726 preceding argument of 0 or @code{--no-values}, prints only the names of the
18727 variables. With an optional preceding argument of 1 or @code{--all-values},
18728 also prints their values.
18730 @subsubheading Example
18734 -var-list-children n
18735 numchild=@var{n},children=[@{name=@var{name},
18736 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
18738 -var-list-children --all-values n
18739 numchild=@var{n},children=[@{name=@var{name},
18740 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
18744 @subheading The @code{-var-info-type} Command
18745 @findex -var-info-type
18747 @subsubheading Synopsis
18750 -var-info-type @var{name}
18753 Returns the type of the specified variable @var{name}. The type is
18754 returned as a string in the same format as it is output by the
18758 type=@var{typename}
18762 @subheading The @code{-var-info-expression} Command
18763 @findex -var-info-expression
18765 @subsubheading Synopsis
18768 -var-info-expression @var{name}
18771 Returns what is represented by the variable object @var{name}:
18774 lang=@var{lang-spec},exp=@var{expression}
18778 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
18780 @subheading The @code{-var-show-attributes} Command
18781 @findex -var-show-attributes
18783 @subsubheading Synopsis
18786 -var-show-attributes @var{name}
18789 List attributes of the specified variable object @var{name}:
18792 status=@var{attr} [ ( ,@var{attr} )* ]
18796 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
18798 @subheading The @code{-var-evaluate-expression} Command
18799 @findex -var-evaluate-expression
18801 @subsubheading Synopsis
18804 -var-evaluate-expression @var{name}
18807 Evaluates the expression that is represented by the specified variable
18808 object and returns its value as a string in the current format specified
18815 Note that one must invoke @code{-var-list-children} for a variable
18816 before the value of a child variable can be evaluated.
18818 @subheading The @code{-var-assign} Command
18819 @findex -var-assign
18821 @subsubheading Synopsis
18824 -var-assign @var{name} @var{expression}
18827 Assigns the value of @var{expression} to the variable object specified
18828 by @var{name}. The object must be @samp{editable}. If the variable's
18829 value is altered by the assign, the variable will show up in any
18830 subsequent @code{-var-update} list.
18832 @subsubheading Example
18840 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
18844 @subheading The @code{-var-update} Command
18845 @findex -var-update
18847 @subsubheading Synopsis
18850 -var-update @{@var{name} | "*"@}
18853 Update the value of the variable object @var{name} by evaluating its
18854 expression after fetching all the new values from memory or registers.
18855 A @samp{*} causes all existing variable objects to be updated.
18859 @chapter @value{GDBN} Annotations
18861 This chapter describes annotations in @value{GDBN}. Annotations were
18862 designed to interface @value{GDBN} to graphical user interfaces or other
18863 similar programs which want to interact with @value{GDBN} at a
18864 relatively high level.
18866 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
18870 This is Edition @value{EDITION}, @value{DATE}.
18874 * Annotations Overview:: What annotations are; the general syntax.
18875 * Server Prefix:: Issuing a command without affecting user state.
18876 * Prompting:: Annotations marking @value{GDBN}'s need for input.
18877 * Errors:: Annotations for error messages.
18878 * Invalidation:: Some annotations describe things now invalid.
18879 * Annotations for Running::
18880 Whether the program is running, how it stopped, etc.
18881 * Source Annotations:: Annotations describing source code.
18884 @node Annotations Overview
18885 @section What is an Annotation?
18886 @cindex annotations
18888 Annotations start with a newline character, two @samp{control-z}
18889 characters, and the name of the annotation. If there is no additional
18890 information associated with this annotation, the name of the annotation
18891 is followed immediately by a newline. If there is additional
18892 information, the name of the annotation is followed by a space, the
18893 additional information, and a newline. The additional information
18894 cannot contain newline characters.
18896 Any output not beginning with a newline and two @samp{control-z}
18897 characters denotes literal output from @value{GDBN}. Currently there is
18898 no need for @value{GDBN} to output a newline followed by two
18899 @samp{control-z} characters, but if there was such a need, the
18900 annotations could be extended with an @samp{escape} annotation which
18901 means those three characters as output.
18903 The annotation @var{level}, which is specified using the
18904 @option{--annotate} command line option (@pxref{Mode Options}), controls
18905 how much information @value{GDBN} prints together with its prompt,
18906 values of expressions, source lines, and other types of output. Level 0
18907 is for no anntations, level 1 is for use when @value{GDBN} is run as a
18908 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
18909 for programs that control @value{GDBN}, and level 2 annotations have
18910 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
18911 Interface, annotate, GDB's Obsolete Annotations}). This chapter
18912 describes level 3 annotations.
18914 A simple example of starting up @value{GDBN} with annotations is:
18917 $ @kbd{gdb --annotate=3}
18919 Copyright 2003 Free Software Foundation, Inc.
18920 GDB is free software, covered by the GNU General Public License,
18921 and you are welcome to change it and/or distribute copies of it
18922 under certain conditions.
18923 Type "show copying" to see the conditions.
18924 There is absolutely no warranty for GDB. Type "show warranty"
18926 This GDB was configured as "i386-pc-linux-gnu"
18937 Here @samp{quit} is input to @value{GDBN}; the rest is output from
18938 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
18939 denotes a @samp{control-z} character) are annotations; the rest is
18940 output from @value{GDBN}.
18942 @node Server Prefix
18943 @section The Server Prefix
18944 @cindex server prefix for annotations
18946 To issue a command to @value{GDBN} without affecting certain aspects of
18947 the state which is seen by users, prefix it with @samp{server }. This
18948 means that this command will not affect the command history, nor will it
18949 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
18950 pressed on a line by itself.
18952 The server prefix does not affect the recording of values into the value
18953 history; to print a value without recording it into the value history,
18954 use the @code{output} command instead of the @code{print} command.
18957 @section Annotation for @value{GDBN} Input
18959 @cindex annotations for prompts
18960 When @value{GDBN} prompts for input, it annotates this fact so it is possible
18961 to know when to send output, when the output from a given command is
18964 Different kinds of input each have a different @dfn{input type}. Each
18965 input type has three annotations: a @code{pre-} annotation, which
18966 denotes the beginning of any prompt which is being output, a plain
18967 annotation, which denotes the end of the prompt, and then a @code{post-}
18968 annotation which denotes the end of any echo which may (or may not) be
18969 associated with the input. For example, the @code{prompt} input type
18970 features the following annotations:
18978 The input types are
18983 @findex post-prompt
18985 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
18987 @findex pre-commands
18989 @findex post-commands
18991 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
18992 command. The annotations are repeated for each command which is input.
18994 @findex pre-overload-choice
18995 @findex overload-choice
18996 @findex post-overload-choice
18997 @item overload-choice
18998 When @value{GDBN} wants the user to select between various overloaded functions.
19004 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
19006 @findex pre-prompt-for-continue
19007 @findex prompt-for-continue
19008 @findex post-prompt-for-continue
19009 @item prompt-for-continue
19010 When @value{GDBN} is asking the user to press return to continue. Note: Don't
19011 expect this to work well; instead use @code{set height 0} to disable
19012 prompting. This is because the counting of lines is buggy in the
19013 presence of annotations.
19018 @cindex annotations for errors, warnings and interrupts
19025 This annotation occurs right before @value{GDBN} responds to an interrupt.
19032 This annotation occurs right before @value{GDBN} responds to an error.
19034 Quit and error annotations indicate that any annotations which @value{GDBN} was
19035 in the middle of may end abruptly. For example, if a
19036 @code{value-history-begin} annotation is followed by a @code{error}, one
19037 cannot expect to receive the matching @code{value-history-end}. One
19038 cannot expect not to receive it either, however; an error annotation
19039 does not necessarily mean that @value{GDBN} is immediately returning all the way
19042 @findex error-begin
19043 A quit or error annotation may be preceded by
19049 Any output between that and the quit or error annotation is the error
19052 Warning messages are not yet annotated.
19053 @c If we want to change that, need to fix warning(), type_error(),
19054 @c range_error(), and possibly other places.
19057 @section Invalidation Notices
19059 @cindex annotations for invalidation messages
19060 The following annotations say that certain pieces of state may have
19064 @findex frames-invalid
19065 @item ^Z^Zframes-invalid
19067 The frames (for example, output from the @code{backtrace} command) may
19070 @findex breakpoints-invalid
19071 @item ^Z^Zbreakpoints-invalid
19073 The breakpoints may have changed. For example, the user just added or
19074 deleted a breakpoint.
19077 @node Annotations for Running
19078 @section Running the Program
19079 @cindex annotations for running programs
19083 When the program starts executing due to a @value{GDBN} command such as
19084 @code{step} or @code{continue},
19090 is output. When the program stops,
19096 is output. Before the @code{stopped} annotation, a variety of
19097 annotations describe how the program stopped.
19101 @item ^Z^Zexited @var{exit-status}
19102 The program exited, and @var{exit-status} is the exit status (zero for
19103 successful exit, otherwise nonzero).
19106 @findex signal-name
19107 @findex signal-name-end
19108 @findex signal-string
19109 @findex signal-string-end
19110 @item ^Z^Zsignalled
19111 The program exited with a signal. After the @code{^Z^Zsignalled}, the
19112 annotation continues:
19118 ^Z^Zsignal-name-end
19122 ^Z^Zsignal-string-end
19127 where @var{name} is the name of the signal, such as @code{SIGILL} or
19128 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
19129 as @code{Illegal Instruction} or @code{Segmentation fault}.
19130 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
19131 user's benefit and have no particular format.
19135 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
19136 just saying that the program received the signal, not that it was
19137 terminated with it.
19140 @item ^Z^Zbreakpoint @var{number}
19141 The program hit breakpoint number @var{number}.
19144 @item ^Z^Zwatchpoint @var{number}
19145 The program hit watchpoint number @var{number}.
19148 @node Source Annotations
19149 @section Displaying Source
19150 @cindex annotations for source display
19153 The following annotation is used instead of displaying source code:
19156 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
19159 where @var{filename} is an absolute file name indicating which source
19160 file, @var{line} is the line number within that file (where 1 is the
19161 first line in the file), @var{character} is the character position
19162 within the file (where 0 is the first character in the file) (for most
19163 debug formats this will necessarily point to the beginning of a line),
19164 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
19165 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
19166 @var{addr} is the address in the target program associated with the
19167 source which is being displayed. @var{addr} is in the form @samp{0x}
19168 followed by one or more lowercase hex digits (note that this does not
19169 depend on the language).
19172 @chapter Reporting Bugs in @value{GDBN}
19173 @cindex bugs in @value{GDBN}
19174 @cindex reporting bugs in @value{GDBN}
19176 Your bug reports play an essential role in making @value{GDBN} reliable.
19178 Reporting a bug may help you by bringing a solution to your problem, or it
19179 may not. But in any case the principal function of a bug report is to help
19180 the entire community by making the next version of @value{GDBN} work better. Bug
19181 reports are your contribution to the maintenance of @value{GDBN}.
19183 In order for a bug report to serve its purpose, you must include the
19184 information that enables us to fix the bug.
19187 * Bug Criteria:: Have you found a bug?
19188 * Bug Reporting:: How to report bugs
19192 @section Have you found a bug?
19193 @cindex bug criteria
19195 If you are not sure whether you have found a bug, here are some guidelines:
19198 @cindex fatal signal
19199 @cindex debugger crash
19200 @cindex crash of debugger
19202 If the debugger gets a fatal signal, for any input whatever, that is a
19203 @value{GDBN} bug. Reliable debuggers never crash.
19205 @cindex error on valid input
19207 If @value{GDBN} produces an error message for valid input, that is a
19208 bug. (Note that if you're cross debugging, the problem may also be
19209 somewhere in the connection to the target.)
19211 @cindex invalid input
19213 If @value{GDBN} does not produce an error message for invalid input,
19214 that is a bug. However, you should note that your idea of
19215 ``invalid input'' might be our idea of ``an extension'' or ``support
19216 for traditional practice''.
19219 If you are an experienced user of debugging tools, your suggestions
19220 for improvement of @value{GDBN} are welcome in any case.
19223 @node Bug Reporting
19224 @section How to report bugs
19225 @cindex bug reports
19226 @cindex @value{GDBN} bugs, reporting
19228 A number of companies and individuals offer support for @sc{gnu} products.
19229 If you obtained @value{GDBN} from a support organization, we recommend you
19230 contact that organization first.
19232 You can find contact information for many support companies and
19233 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
19235 @c should add a web page ref...
19237 In any event, we also recommend that you submit bug reports for
19238 @value{GDBN}. The prefered method is to submit them directly using
19239 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
19240 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
19243 @strong{Do not send bug reports to @samp{info-gdb}, or to
19244 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
19245 not want to receive bug reports. Those that do have arranged to receive
19248 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
19249 serves as a repeater. The mailing list and the newsgroup carry exactly
19250 the same messages. Often people think of posting bug reports to the
19251 newsgroup instead of mailing them. This appears to work, but it has one
19252 problem which can be crucial: a newsgroup posting often lacks a mail
19253 path back to the sender. Thus, if we need to ask for more information,
19254 we may be unable to reach you. For this reason, it is better to send
19255 bug reports to the mailing list.
19257 The fundamental principle of reporting bugs usefully is this:
19258 @strong{report all the facts}. If you are not sure whether to state a
19259 fact or leave it out, state it!
19261 Often people omit facts because they think they know what causes the
19262 problem and assume that some details do not matter. Thus, you might
19263 assume that the name of the variable you use in an example does not matter.
19264 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
19265 stray memory reference which happens to fetch from the location where that
19266 name is stored in memory; perhaps, if the name were different, the contents
19267 of that location would fool the debugger into doing the right thing despite
19268 the bug. Play it safe and give a specific, complete example. That is the
19269 easiest thing for you to do, and the most helpful.
19271 Keep in mind that the purpose of a bug report is to enable us to fix the
19272 bug. It may be that the bug has been reported previously, but neither
19273 you nor we can know that unless your bug report is complete and
19276 Sometimes people give a few sketchy facts and ask, ``Does this ring a
19277 bell?'' Those bug reports are useless, and we urge everyone to
19278 @emph{refuse to respond to them} except to chide the sender to report
19281 To enable us to fix the bug, you should include all these things:
19285 The version of @value{GDBN}. @value{GDBN} announces it if you start
19286 with no arguments; you can also print it at any time using @code{show
19289 Without this, we will not know whether there is any point in looking for
19290 the bug in the current version of @value{GDBN}.
19293 The type of machine you are using, and the operating system name and
19297 What compiler (and its version) was used to compile @value{GDBN}---e.g.
19298 ``@value{GCC}--2.8.1''.
19301 What compiler (and its version) was used to compile the program you are
19302 debugging---e.g. ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
19303 C Compiler''. For GCC, you can say @code{gcc --version} to get this
19304 information; for other compilers, see the documentation for those
19308 The command arguments you gave the compiler to compile your example and
19309 observe the bug. For example, did you use @samp{-O}? To guarantee
19310 you will not omit something important, list them all. A copy of the
19311 Makefile (or the output from make) is sufficient.
19313 If we were to try to guess the arguments, we would probably guess wrong
19314 and then we might not encounter the bug.
19317 A complete input script, and all necessary source files, that will
19321 A description of what behavior you observe that you believe is
19322 incorrect. For example, ``It gets a fatal signal.''
19324 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
19325 will certainly notice it. But if the bug is incorrect output, we might
19326 not notice unless it is glaringly wrong. You might as well not give us
19327 a chance to make a mistake.
19329 Even if the problem you experience is a fatal signal, you should still
19330 say so explicitly. Suppose something strange is going on, such as, your
19331 copy of @value{GDBN} is out of synch, or you have encountered a bug in
19332 the C library on your system. (This has happened!) Your copy might
19333 crash and ours would not. If you told us to expect a crash, then when
19334 ours fails to crash, we would know that the bug was not happening for
19335 us. If you had not told us to expect a crash, then we would not be able
19336 to draw any conclusion from our observations.
19339 @cindex recording a session script
19340 To collect all this information, you can use a session recording program
19341 such as @command{script}, which is available on many Unix systems.
19342 Just run your @value{GDBN} session inside @command{script} and then
19343 include the @file{typescript} file with your bug report.
19345 Another way to record a @value{GDBN} session is to run @value{GDBN}
19346 inside Emacs and then save the entire buffer to a file.
19349 If you wish to suggest changes to the @value{GDBN} source, send us context
19350 diffs. If you even discuss something in the @value{GDBN} source, refer to
19351 it by context, not by line number.
19353 The line numbers in our development sources will not match those in your
19354 sources. Your line numbers would convey no useful information to us.
19358 Here are some things that are not necessary:
19362 A description of the envelope of the bug.
19364 Often people who encounter a bug spend a lot of time investigating
19365 which changes to the input file will make the bug go away and which
19366 changes will not affect it.
19368 This is often time consuming and not very useful, because the way we
19369 will find the bug is by running a single example under the debugger
19370 with breakpoints, not by pure deduction from a series of examples.
19371 We recommend that you save your time for something else.
19373 Of course, if you can find a simpler example to report @emph{instead}
19374 of the original one, that is a convenience for us. Errors in the
19375 output will be easier to spot, running under the debugger will take
19376 less time, and so on.
19378 However, simplification is not vital; if you do not want to do this,
19379 report the bug anyway and send us the entire test case you used.
19382 A patch for the bug.
19384 A patch for the bug does help us if it is a good one. But do not omit
19385 the necessary information, such as the test case, on the assumption that
19386 a patch is all we need. We might see problems with your patch and decide
19387 to fix the problem another way, or we might not understand it at all.
19389 Sometimes with a program as complicated as @value{GDBN} it is very hard to
19390 construct an example that will make the program follow a certain path
19391 through the code. If you do not send us the example, we will not be able
19392 to construct one, so we will not be able to verify that the bug is fixed.
19394 And if we cannot understand what bug you are trying to fix, or why your
19395 patch should be an improvement, we will not install it. A test case will
19396 help us to understand.
19399 A guess about what the bug is or what it depends on.
19401 Such guesses are usually wrong. Even we cannot guess right about such
19402 things without first using the debugger to find the facts.
19405 @c The readline documentation is distributed with the readline code
19406 @c and consists of the two following files:
19408 @c inc-hist.texinfo
19409 @c Use -I with makeinfo to point to the appropriate directory,
19410 @c environment var TEXINPUTS with TeX.
19411 @include rluser.texinfo
19412 @include inc-hist.texinfo
19415 @node Formatting Documentation
19416 @appendix Formatting Documentation
19418 @cindex @value{GDBN} reference card
19419 @cindex reference card
19420 The @value{GDBN} 4 release includes an already-formatted reference card, ready
19421 for printing with PostScript or Ghostscript, in the @file{gdb}
19422 subdirectory of the main source directory@footnote{In
19423 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
19424 release.}. If you can use PostScript or Ghostscript with your printer,
19425 you can print the reference card immediately with @file{refcard.ps}.
19427 The release also includes the source for the reference card. You
19428 can format it, using @TeX{}, by typing:
19434 The @value{GDBN} reference card is designed to print in @dfn{landscape}
19435 mode on US ``letter'' size paper;
19436 that is, on a sheet 11 inches wide by 8.5 inches
19437 high. You will need to specify this form of printing as an option to
19438 your @sc{dvi} output program.
19440 @cindex documentation
19442 All the documentation for @value{GDBN} comes as part of the machine-readable
19443 distribution. The documentation is written in Texinfo format, which is
19444 a documentation system that uses a single source file to produce both
19445 on-line information and a printed manual. You can use one of the Info
19446 formatting commands to create the on-line version of the documentation
19447 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
19449 @value{GDBN} includes an already formatted copy of the on-line Info
19450 version of this manual in the @file{gdb} subdirectory. The main Info
19451 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
19452 subordinate files matching @samp{gdb.info*} in the same directory. If
19453 necessary, you can print out these files, or read them with any editor;
19454 but they are easier to read using the @code{info} subsystem in @sc{gnu}
19455 Emacs or the standalone @code{info} program, available as part of the
19456 @sc{gnu} Texinfo distribution.
19458 If you want to format these Info files yourself, you need one of the
19459 Info formatting programs, such as @code{texinfo-format-buffer} or
19462 If you have @code{makeinfo} installed, and are in the top level
19463 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
19464 version @value{GDBVN}), you can make the Info file by typing:
19471 If you want to typeset and print copies of this manual, you need @TeX{},
19472 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
19473 Texinfo definitions file.
19475 @TeX{} is a typesetting program; it does not print files directly, but
19476 produces output files called @sc{dvi} files. To print a typeset
19477 document, you need a program to print @sc{dvi} files. If your system
19478 has @TeX{} installed, chances are it has such a program. The precise
19479 command to use depends on your system; @kbd{lpr -d} is common; another
19480 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
19481 require a file name without any extension or a @samp{.dvi} extension.
19483 @TeX{} also requires a macro definitions file called
19484 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
19485 written in Texinfo format. On its own, @TeX{} cannot either read or
19486 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
19487 and is located in the @file{gdb-@var{version-number}/texinfo}
19490 If you have @TeX{} and a @sc{dvi} printer program installed, you can
19491 typeset and print this manual. First switch to the the @file{gdb}
19492 subdirectory of the main source directory (for example, to
19493 @file{gdb-@value{GDBVN}/gdb}) and type:
19499 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
19501 @node Installing GDB
19502 @appendix Installing @value{GDBN}
19503 @cindex configuring @value{GDBN}
19504 @cindex installation
19505 @cindex configuring @value{GDBN}, and source tree subdirectories
19507 @value{GDBN} comes with a @code{configure} script that automates the process
19508 of preparing @value{GDBN} for installation; you can then use @code{make} to
19509 build the @code{gdb} program.
19511 @c irrelevant in info file; it's as current as the code it lives with.
19512 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
19513 look at the @file{README} file in the sources; we may have improved the
19514 installation procedures since publishing this manual.}
19517 The @value{GDBN} distribution includes all the source code you need for
19518 @value{GDBN} in a single directory, whose name is usually composed by
19519 appending the version number to @samp{gdb}.
19521 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
19522 @file{gdb-@value{GDBVN}} directory. That directory contains:
19525 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
19526 script for configuring @value{GDBN} and all its supporting libraries
19528 @item gdb-@value{GDBVN}/gdb
19529 the source specific to @value{GDBN} itself
19531 @item gdb-@value{GDBVN}/bfd
19532 source for the Binary File Descriptor library
19534 @item gdb-@value{GDBVN}/include
19535 @sc{gnu} include files
19537 @item gdb-@value{GDBVN}/libiberty
19538 source for the @samp{-liberty} free software library
19540 @item gdb-@value{GDBVN}/opcodes
19541 source for the library of opcode tables and disassemblers
19543 @item gdb-@value{GDBVN}/readline
19544 source for the @sc{gnu} command-line interface
19546 @item gdb-@value{GDBVN}/glob
19547 source for the @sc{gnu} filename pattern-matching subroutine
19549 @item gdb-@value{GDBVN}/mmalloc
19550 source for the @sc{gnu} memory-mapped malloc package
19553 The simplest way to configure and build @value{GDBN} is to run @code{configure}
19554 from the @file{gdb-@var{version-number}} source directory, which in
19555 this example is the @file{gdb-@value{GDBVN}} directory.
19557 First switch to the @file{gdb-@var{version-number}} source directory
19558 if you are not already in it; then run @code{configure}. Pass the
19559 identifier for the platform on which @value{GDBN} will run as an
19565 cd gdb-@value{GDBVN}
19566 ./configure @var{host}
19571 where @var{host} is an identifier such as @samp{sun4} or
19572 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
19573 (You can often leave off @var{host}; @code{configure} tries to guess the
19574 correct value by examining your system.)
19576 Running @samp{configure @var{host}} and then running @code{make} builds the
19577 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
19578 libraries, then @code{gdb} itself. The configured source files, and the
19579 binaries, are left in the corresponding source directories.
19582 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
19583 system does not recognize this automatically when you run a different
19584 shell, you may need to run @code{sh} on it explicitly:
19587 sh configure @var{host}
19590 If you run @code{configure} from a directory that contains source
19591 directories for multiple libraries or programs, such as the
19592 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
19593 creates configuration files for every directory level underneath (unless
19594 you tell it not to, with the @samp{--norecursion} option).
19596 You should run the @code{configure} script from the top directory in the
19597 source tree, the @file{gdb-@var{version-number}} directory. If you run
19598 @code{configure} from one of the subdirectories, you will configure only
19599 that subdirectory. That is usually not what you want. In particular,
19600 if you run the first @code{configure} from the @file{gdb} subdirectory
19601 of the @file{gdb-@var{version-number}} directory, you will omit the
19602 configuration of @file{bfd}, @file{readline}, and other sibling
19603 directories of the @file{gdb} subdirectory. This leads to build errors
19604 about missing include files such as @file{bfd/bfd.h}.
19606 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
19607 However, you should make sure that the shell on your path (named by
19608 the @samp{SHELL} environment variable) is publicly readable. Remember
19609 that @value{GDBN} uses the shell to start your program---some systems refuse to
19610 let @value{GDBN} debug child processes whose programs are not readable.
19613 * Separate Objdir:: Compiling @value{GDBN} in another directory
19614 * Config Names:: Specifying names for hosts and targets
19615 * Configure Options:: Summary of options for configure
19618 @node Separate Objdir
19619 @section Compiling @value{GDBN} in another directory
19621 If you want to run @value{GDBN} versions for several host or target machines,
19622 you need a different @code{gdb} compiled for each combination of
19623 host and target. @code{configure} is designed to make this easy by
19624 allowing you to generate each configuration in a separate subdirectory,
19625 rather than in the source directory. If your @code{make} program
19626 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
19627 @code{make} in each of these directories builds the @code{gdb}
19628 program specified there.
19630 To build @code{gdb} in a separate directory, run @code{configure}
19631 with the @samp{--srcdir} option to specify where to find the source.
19632 (You also need to specify a path to find @code{configure}
19633 itself from your working directory. If the path to @code{configure}
19634 would be the same as the argument to @samp{--srcdir}, you can leave out
19635 the @samp{--srcdir} option; it is assumed.)
19637 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
19638 separate directory for a Sun 4 like this:
19642 cd gdb-@value{GDBVN}
19645 ../gdb-@value{GDBVN}/configure sun4
19650 When @code{configure} builds a configuration using a remote source
19651 directory, it creates a tree for the binaries with the same structure
19652 (and using the same names) as the tree under the source directory. In
19653 the example, you'd find the Sun 4 library @file{libiberty.a} in the
19654 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
19655 @file{gdb-sun4/gdb}.
19657 Make sure that your path to the @file{configure} script has just one
19658 instance of @file{gdb} in it. If your path to @file{configure} looks
19659 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
19660 one subdirectory of @value{GDBN}, not the whole package. This leads to
19661 build errors about missing include files such as @file{bfd/bfd.h}.
19663 One popular reason to build several @value{GDBN} configurations in separate
19664 directories is to configure @value{GDBN} for cross-compiling (where
19665 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
19666 programs that run on another machine---the @dfn{target}).
19667 You specify a cross-debugging target by
19668 giving the @samp{--target=@var{target}} option to @code{configure}.
19670 When you run @code{make} to build a program or library, you must run
19671 it in a configured directory---whatever directory you were in when you
19672 called @code{configure} (or one of its subdirectories).
19674 The @code{Makefile} that @code{configure} generates in each source
19675 directory also runs recursively. If you type @code{make} in a source
19676 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
19677 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
19678 will build all the required libraries, and then build GDB.
19680 When you have multiple hosts or targets configured in separate
19681 directories, you can run @code{make} on them in parallel (for example,
19682 if they are NFS-mounted on each of the hosts); they will not interfere
19686 @section Specifying names for hosts and targets
19688 The specifications used for hosts and targets in the @code{configure}
19689 script are based on a three-part naming scheme, but some short predefined
19690 aliases are also supported. The full naming scheme encodes three pieces
19691 of information in the following pattern:
19694 @var{architecture}-@var{vendor}-@var{os}
19697 For example, you can use the alias @code{sun4} as a @var{host} argument,
19698 or as the value for @var{target} in a @code{--target=@var{target}}
19699 option. The equivalent full name is @samp{sparc-sun-sunos4}.
19701 The @code{configure} script accompanying @value{GDBN} does not provide
19702 any query facility to list all supported host and target names or
19703 aliases. @code{configure} calls the Bourne shell script
19704 @code{config.sub} to map abbreviations to full names; you can read the
19705 script, if you wish, or you can use it to test your guesses on
19706 abbreviations---for example:
19709 % sh config.sub i386-linux
19711 % sh config.sub alpha-linux
19712 alpha-unknown-linux-gnu
19713 % sh config.sub hp9k700
19715 % sh config.sub sun4
19716 sparc-sun-sunos4.1.1
19717 % sh config.sub sun3
19718 m68k-sun-sunos4.1.1
19719 % sh config.sub i986v
19720 Invalid configuration `i986v': machine `i986v' not recognized
19724 @code{config.sub} is also distributed in the @value{GDBN} source
19725 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
19727 @node Configure Options
19728 @section @code{configure} options
19730 Here is a summary of the @code{configure} options and arguments that
19731 are most often useful for building @value{GDBN}. @code{configure} also has
19732 several other options not listed here. @inforef{What Configure
19733 Does,,configure.info}, for a full explanation of @code{configure}.
19736 configure @r{[}--help@r{]}
19737 @r{[}--prefix=@var{dir}@r{]}
19738 @r{[}--exec-prefix=@var{dir}@r{]}
19739 @r{[}--srcdir=@var{dirname}@r{]}
19740 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
19741 @r{[}--target=@var{target}@r{]}
19746 You may introduce options with a single @samp{-} rather than
19747 @samp{--} if you prefer; but you may abbreviate option names if you use
19752 Display a quick summary of how to invoke @code{configure}.
19754 @item --prefix=@var{dir}
19755 Configure the source to install programs and files under directory
19758 @item --exec-prefix=@var{dir}
19759 Configure the source to install programs under directory
19762 @c avoid splitting the warning from the explanation:
19764 @item --srcdir=@var{dirname}
19765 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
19766 @code{make} that implements the @code{VPATH} feature.}@*
19767 Use this option to make configurations in directories separate from the
19768 @value{GDBN} source directories. Among other things, you can use this to
19769 build (or maintain) several configurations simultaneously, in separate
19770 directories. @code{configure} writes configuration specific files in
19771 the current directory, but arranges for them to use the source in the
19772 directory @var{dirname}. @code{configure} creates directories under
19773 the working directory in parallel to the source directories below
19776 @item --norecursion
19777 Configure only the directory level where @code{configure} is executed; do not
19778 propagate configuration to subdirectories.
19780 @item --target=@var{target}
19781 Configure @value{GDBN} for cross-debugging programs running on the specified
19782 @var{target}. Without this option, @value{GDBN} is configured to debug
19783 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
19785 There is no convenient way to generate a list of all available targets.
19787 @item @var{host} @dots{}
19788 Configure @value{GDBN} to run on the specified @var{host}.
19790 There is no convenient way to generate a list of all available hosts.
19793 There are many other options available as well, but they are generally
19794 needed for special purposes only.
19796 @node Maintenance Commands
19797 @appendix Maintenance Commands
19798 @cindex maintenance commands
19799 @cindex internal commands
19801 In addition to commands intended for @value{GDBN} users, @value{GDBN}
19802 includes a number of commands intended for @value{GDBN} developers.
19803 These commands are provided here for reference.
19806 @kindex maint info breakpoints
19807 @item @anchor{maint info breakpoints}maint info breakpoints
19808 Using the same format as @samp{info breakpoints}, display both the
19809 breakpoints you've set explicitly, and those @value{GDBN} is using for
19810 internal purposes. Internal breakpoints are shown with negative
19811 breakpoint numbers. The type column identifies what kind of breakpoint
19816 Normal, explicitly set breakpoint.
19819 Normal, explicitly set watchpoint.
19822 Internal breakpoint, used to handle correctly stepping through
19823 @code{longjmp} calls.
19825 @item longjmp resume
19826 Internal breakpoint at the target of a @code{longjmp}.
19829 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
19832 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
19835 Shared library events.
19839 @kindex maint internal-error
19840 @kindex maint internal-warning
19841 @item maint internal-error
19842 @itemx maint internal-warning
19843 Cause @value{GDBN} to call the internal function @code{internal_error}
19844 or @code{internal_warning} and hence behave as though an internal error
19845 or internal warning has been detected. In addition to reporting the
19846 internal problem, these functions give the user the opportunity to
19847 either quit @value{GDBN} or create a core file of the current
19848 @value{GDBN} session.
19851 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
19852 @dots{}/maint.c:121: internal-error: testing, 1, 2
19853 A problem internal to GDB has been detected. Further
19854 debugging may prove unreliable.
19855 Quit this debugging session? (y or n) @kbd{n}
19856 Create a core file? (y or n) @kbd{n}
19860 Takes an optional parameter that is used as the text of the error or
19863 @kindex maint print dummy-frames
19864 @item maint print dummy-frames
19866 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
19869 (@value{GDBP}) @kbd{b add}
19871 (@value{GDBP}) @kbd{print add(2,3)}
19872 Breakpoint 2, add (a=2, b=3) at @dots{}
19874 The program being debugged stopped while in a function called from GDB.
19876 (@value{GDBP}) @kbd{maint print dummy-frames}
19877 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
19878 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
19879 call_lo=0x01014000 call_hi=0x01014001
19883 Takes an optional file parameter.
19885 @kindex maint print registers
19886 @kindex maint print raw-registers
19887 @kindex maint print cooked-registers
19888 @kindex maint print register-groups
19889 @item maint print registers
19890 @itemx maint print raw-registers
19891 @itemx maint print cooked-registers
19892 @itemx maint print register-groups
19893 Print @value{GDBN}'s internal register data structures.
19895 The command @code{maint print raw-registers} includes the contents of
19896 the raw register cache; the command @code{maint print cooked-registers}
19897 includes the (cooked) value of all registers; and the command
19898 @code{maint print register-groups} includes the groups that each
19899 register is a member of. @xref{Registers,, Registers, gdbint,
19900 @value{GDBN} Internals}.
19902 Takes an optional file parameter.
19904 @kindex maint print reggroups
19905 @item maint print reggroups
19906 Print @value{GDBN}'s internal register group data structures.
19908 Takes an optional file parameter.
19911 (@value{GDBP}) @kbd{maint print reggroups}
19922 @kindex maint set profile
19923 @kindex maint show profile
19924 @cindex profiling GDB
19925 @item maint set profile
19926 @itemx maint show profile
19927 Control profiling of @value{GDBN}.
19929 Profiling will be disabled until you use the @samp{maint set profile}
19930 command to enable it. When you enable profiling, the system will begin
19931 collecting timing and execution count data; when you disable profiling or
19932 exit @value{GDBN}, the results will be written to a log file. Remember that
19933 if you use profiling, @value{GDBN} will overwrite the profiling log file
19934 (often called @file{gmon.out}). If you have a record of important profiling
19935 data in a @file{gmon.out} file, be sure to move it to a safe location.
19937 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
19938 compiled with the @samp{-pg} compiler option.
19940 @kindex maint set dwarf2 max-cache-age
19941 @kindex maint show dwarf2 max-cache-age
19942 @item maint set dwarf2 max-cache-age
19943 @itemx maint show dwarf2 max-cache-age
19944 Control the DWARF 2 compilation unit cache.
19946 In object files with inter-compilation-unit references, such as those
19947 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
19948 reader needs to frequently refer to previously read compilation units.
19949 This setting controls how long a compilation unit will remain in the cache
19950 if it is not referenced. Setting it to zero disables caching, which will
19951 slow down @value{GDBN} startup but reduce memory consumption.
19956 @node Remote Protocol
19957 @appendix @value{GDBN} Remote Serial Protocol
19962 * Stop Reply Packets::
19963 * General Query Packets::
19964 * Register Packet Format::
19966 * File-I/O remote protocol extension::
19972 There may be occasions when you need to know something about the
19973 protocol---for example, if there is only one serial port to your target
19974 machine, you might want your program to do something special if it
19975 recognizes a packet meant for @value{GDBN}.
19977 In the examples below, @samp{->} and @samp{<-} are used to indicate
19978 transmitted and received data respectfully.
19980 @cindex protocol, @value{GDBN} remote serial
19981 @cindex serial protocol, @value{GDBN} remote
19982 @cindex remote serial protocol
19983 All @value{GDBN} commands and responses (other than acknowledgments) are
19984 sent as a @var{packet}. A @var{packet} is introduced with the character
19985 @samp{$}, the actual @var{packet-data}, and the terminating character
19986 @samp{#} followed by a two-digit @var{checksum}:
19989 @code{$}@var{packet-data}@code{#}@var{checksum}
19993 @cindex checksum, for @value{GDBN} remote
19995 The two-digit @var{checksum} is computed as the modulo 256 sum of all
19996 characters between the leading @samp{$} and the trailing @samp{#} (an
19997 eight bit unsigned checksum).
19999 Implementors should note that prior to @value{GDBN} 5.0 the protocol
20000 specification also included an optional two-digit @var{sequence-id}:
20003 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
20006 @cindex sequence-id, for @value{GDBN} remote
20008 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
20009 has never output @var{sequence-id}s. Stubs that handle packets added
20010 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
20012 @cindex acknowledgment, for @value{GDBN} remote
20013 When either the host or the target machine receives a packet, the first
20014 response expected is an acknowledgment: either @samp{+} (to indicate
20015 the package was received correctly) or @samp{-} (to request
20019 -> @code{$}@var{packet-data}@code{#}@var{checksum}
20024 The host (@value{GDBN}) sends @var{command}s, and the target (the
20025 debugging stub incorporated in your program) sends a @var{response}. In
20026 the case of step and continue @var{command}s, the response is only sent
20027 when the operation has completed (the target has again stopped).
20029 @var{packet-data} consists of a sequence of characters with the
20030 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
20033 Fields within the packet should be separated using @samp{,} @samp{;} or
20034 @cindex remote protocol, field separator
20035 @samp{:}. Except where otherwise noted all numbers are represented in
20036 @sc{hex} with leading zeros suppressed.
20038 Implementors should note that prior to @value{GDBN} 5.0, the character
20039 @samp{:} could not appear as the third character in a packet (as it
20040 would potentially conflict with the @var{sequence-id}).
20042 Response @var{data} can be run-length encoded to save space. A @samp{*}
20043 means that the next character is an @sc{ascii} encoding giving a repeat count
20044 which stands for that many repetitions of the character preceding the
20045 @samp{*}. The encoding is @code{n+29}, yielding a printable character
20046 where @code{n >=3} (which is where rle starts to win). The printable
20047 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
20048 value greater than 126 should not be used.
20055 means the same as "0000".
20057 The error response returned for some packets includes a two character
20058 error number. That number is not well defined.
20060 For any @var{command} not supported by the stub, an empty response
20061 (@samp{$#00}) should be returned. That way it is possible to extend the
20062 protocol. A newer @value{GDBN} can tell if a packet is supported based
20065 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
20066 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
20072 The following table provides a complete list of all currently defined
20073 @var{command}s and their corresponding response @var{data}.
20077 @item @code{!} --- extended mode
20078 @cindex @code{!} packet
20080 Enable extended mode. In extended mode, the remote server is made
20081 persistent. The @samp{R} packet is used to restart the program being
20087 The remote target both supports and has enabled extended mode.
20090 @item @code{?} --- last signal
20091 @cindex @code{?} packet
20093 Indicate the reason the target halted. The reply is the same as for
20097 @xref{Stop Reply Packets}, for the reply specifications.
20099 @item @code{a} --- reserved
20101 Reserved for future use.
20103 @item @code{A}@var{arglen}@code{,}@var{argnum}@code{,}@var{arg}@code{,@dots{}} --- set program arguments @strong{(reserved)}
20104 @cindex @code{A} packet
20106 Initialized @samp{argv[]} array passed into program. @var{arglen}
20107 specifies the number of bytes in the hex encoded byte stream @var{arg}.
20108 See @code{gdbserver} for more details.
20116 @item @code{b}@var{baud} --- set baud @strong{(deprecated)}
20117 @cindex @code{b} packet
20119 Change the serial line speed to @var{baud}.
20121 JTC: @emph{When does the transport layer state change? When it's
20122 received, or after the ACK is transmitted. In either case, there are
20123 problems if the command or the acknowledgment packet is dropped.}
20125 Stan: @emph{If people really wanted to add something like this, and get
20126 it working for the first time, they ought to modify ser-unix.c to send
20127 some kind of out-of-band message to a specially-setup stub and have the
20128 switch happen "in between" packets, so that from remote protocol's point
20129 of view, nothing actually happened.}
20131 @item @code{B}@var{addr},@var{mode} --- set breakpoint @strong{(deprecated)}
20132 @cindex @code{B} packet
20134 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
20135 breakpoint at @var{addr}.
20137 This packet has been replaced by the @samp{Z} and @samp{z} packets
20138 (@pxref{insert breakpoint or watchpoint packet}).
20140 @item @code{c}@var{addr} --- continue
20141 @cindex @code{c} packet
20143 @var{addr} is address to resume. If @var{addr} is omitted, resume at
20147 @xref{Stop Reply Packets}, for the reply specifications.
20149 @item @code{C}@var{sig}@code{;}@var{addr} --- continue with signal
20150 @cindex @code{C} packet
20152 Continue with signal @var{sig} (hex signal number). If
20153 @code{;}@var{addr} is omitted, resume at same address.
20156 @xref{Stop Reply Packets}, for the reply specifications.
20158 @item @code{d} --- toggle debug @strong{(deprecated)}
20159 @cindex @code{d} packet
20163 @item @code{D} --- detach
20164 @cindex @code{D} packet
20166 Detach @value{GDBN} from the remote system. Sent to the remote target
20167 before @value{GDBN} disconnects via the @code{detach} command.
20171 @item @emph{no response}
20172 @value{GDBN} does not check for any response after sending this packet.
20175 @item @code{e} --- reserved
20177 Reserved for future use.
20179 @item @code{E} --- reserved
20181 Reserved for future use.
20183 @item @code{f} --- reserved
20185 Reserved for future use.
20187 @item @code{F}@var{RC}@code{,}@var{EE}@code{,}@var{CF}@code{;}@var{XX} --- Reply to target's F packet.
20188 @cindex @code{F} packet
20190 This packet is send by @value{GDBN} as reply to a @code{F} request packet
20191 sent by the target. This is part of the File-I/O protocol extension.
20192 @xref{File-I/O remote protocol extension}, for the specification.
20194 @item @code{g} --- read registers
20195 @anchor{read registers packet}
20196 @cindex @code{g} packet
20198 Read general registers.
20202 @item @var{XX@dots{}}
20203 Each byte of register data is described by two hex digits. The bytes
20204 with the register are transmitted in target byte order. The size of
20205 each register and their position within the @samp{g} @var{packet} are
20206 determined by the @value{GDBN} internal macros
20207 @var{DEPRECATED_REGISTER_RAW_SIZE} and @var{REGISTER_NAME} macros. The
20208 specification of several standard @code{g} packets is specified below.
20213 @item @code{G}@var{XX@dots{}} --- write regs
20214 @cindex @code{G} packet
20216 @xref{read registers packet}, for a description of the @var{XX@dots{}}
20227 @item @code{h} --- reserved
20229 Reserved for future use.
20231 @item @code{H}@var{c}@var{t@dots{}} --- set thread
20232 @cindex @code{H} packet
20234 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
20235 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
20236 should be @samp{c} for step and continue operations, @samp{g} for other
20237 operations. The thread designator @var{t@dots{}} may be -1, meaning all
20238 the threads, a thread number, or zero which means pick any thread.
20249 @c 'H': How restrictive (or permissive) is the thread model. If a
20250 @c thread is selected and stopped, are other threads allowed
20251 @c to continue to execute? As I mentioned above, I think the
20252 @c semantics of each command when a thread is selected must be
20253 @c described. For example:
20255 @c 'g': If the stub supports threads and a specific thread is
20256 @c selected, returns the register block from that thread;
20257 @c otherwise returns current registers.
20259 @c 'G' If the stub supports threads and a specific thread is
20260 @c selected, sets the registers of the register block of
20261 @c that thread; otherwise sets current registers.
20263 @item @code{i}@var{addr}@code{,}@var{nnn} --- cycle step @strong{(draft)}
20264 @anchor{cycle step packet}
20265 @cindex @code{i} packet
20267 Step the remote target by a single clock cycle. If @code{,}@var{nnn} is
20268 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
20269 step starting at that address.
20271 @item @code{I} --- signal then cycle step @strong{(reserved)}
20272 @cindex @code{I} packet
20274 @xref{step with signal packet}. @xref{cycle step packet}.
20276 @item @code{j} --- reserved
20278 Reserved for future use.
20280 @item @code{J} --- reserved
20282 Reserved for future use.
20284 @item @code{k} --- kill request
20285 @cindex @code{k} packet
20287 FIXME: @emph{There is no description of how to operate when a specific
20288 thread context has been selected (i.e.@: does 'k' kill only that
20291 @item @code{K} --- reserved
20293 Reserved for future use.
20295 @item @code{l} --- reserved
20297 Reserved for future use.
20299 @item @code{L} --- reserved
20301 Reserved for future use.
20303 @item @code{m}@var{addr}@code{,}@var{length} --- read memory
20304 @cindex @code{m} packet
20306 Read @var{length} bytes of memory starting at address @var{addr}.
20307 Neither @value{GDBN} nor the stub assume that sized memory transfers are
20308 assumed using word aligned accesses. FIXME: @emph{A word aligned memory
20309 transfer mechanism is needed.}
20313 @item @var{XX@dots{}}
20314 @var{XX@dots{}} is mem contents. Can be fewer bytes than requested if able
20315 to read only part of the data. Neither @value{GDBN} nor the stub assume
20316 that sized memory transfers are assumed using word aligned
20317 accesses. FIXME: @emph{A word aligned memory transfer mechanism is
20323 @item @code{M}@var{addr},@var{length}@code{:}@var{XX@dots{}} --- write mem
20324 @cindex @code{M} packet
20326 Write @var{length} bytes of memory starting at address @var{addr}.
20327 @var{XX@dots{}} is the data.
20334 for an error (this includes the case where only part of the data was
20338 @item @code{n} --- reserved
20340 Reserved for future use.
20342 @item @code{N} --- reserved
20344 Reserved for future use.
20346 @item @code{o} --- reserved
20348 Reserved for future use.
20350 @item @code{O} --- reserved
20352 @item @code{p}@var{hex number of register} --- read register packet
20353 @cindex @code{p} packet
20355 @xref{read registers packet}, for a description of how the returned
20356 register value is encoded.
20360 @item @var{XX@dots{}}
20361 the register's value
20365 Indicating an unrecognized @var{query}.
20368 @item @code{P}@var{n@dots{}}@code{=}@var{r@dots{}} --- write register
20369 @anchor{write register packet}
20370 @cindex @code{P} packet
20372 Write register @var{n@dots{}} with value @var{r@dots{}}, which contains two hex
20373 digits for each byte in the register (target byte order).
20383 @item @code{q}@var{query} --- general query
20384 @anchor{general query packet}
20385 @cindex @code{q} packet
20387 Request info about @var{query}. In general @value{GDBN} queries have a
20388 leading upper case letter. Custom vendor queries should use a company
20389 prefix (in lower case) ex: @samp{qfsf.var}. @var{query} may optionally
20390 be followed by a @samp{,} or @samp{;} separated list. Stubs must ensure
20391 that they match the full @var{query} name.
20395 @item @var{XX@dots{}}
20396 Hex encoded data from query. The reply can not be empty.
20400 Indicating an unrecognized @var{query}.
20403 @item @code{Q}@var{var}@code{=}@var{val} --- general set
20404 @cindex @code{Q} packet
20406 Set value of @var{var} to @var{val}.
20408 @xref{general query packet}, for a discussion of naming conventions.
20410 @item @code{r} --- reset @strong{(deprecated)}
20411 @cindex @code{r} packet
20413 Reset the entire system.
20415 @item @code{R}@var{XX} --- remote restart
20416 @cindex @code{R} packet
20418 Restart the program being debugged. @var{XX}, while needed, is ignored.
20419 This packet is only available in extended mode.
20423 @item @emph{no reply}
20424 The @samp{R} packet has no reply.
20427 @item @code{s}@var{addr} --- step
20428 @cindex @code{s} packet
20430 @var{addr} is address to resume. If @var{addr} is omitted, resume at
20434 @xref{Stop Reply Packets}, for the reply specifications.
20436 @item @code{S}@var{sig}@code{;}@var{addr} --- step with signal
20437 @anchor{step with signal packet}
20438 @cindex @code{S} packet
20440 Like @samp{C} but step not continue.
20443 @xref{Stop Reply Packets}, for the reply specifications.
20445 @item @code{t}@var{addr}@code{:}@var{PP}@code{,}@var{MM} --- search
20446 @cindex @code{t} packet
20448 Search backwards starting at address @var{addr} for a match with pattern
20449 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
20450 @var{addr} must be at least 3 digits.
20452 @item @code{T}@var{XX} --- thread alive
20453 @cindex @code{T} packet
20455 Find out if the thread XX is alive.
20460 thread is still alive
20465 @item @code{u} --- reserved
20467 Reserved for future use.
20469 @item @code{U} --- reserved
20471 Reserved for future use.
20473 @item @code{v} --- verbose packet prefix
20475 Packets starting with @code{v} are identified by a multi-letter name,
20476 up to the first @code{;} or @code{?} (or the end of the packet).
20478 @item @code{vCont}[;@var{action}[@code{:}@var{tid}]]... --- extended resume
20479 @cindex @code{vCont} packet
20481 Resume the inferior. Different actions may be specified for each thread.
20482 If an action is specified with no @var{tid}, then it is applied to any
20483 threads that don't have a specific action specified; if no default action is
20484 specified then other threads should remain stopped. Specifying multiple
20485 default actions is an error; specifying no actions is also an error.
20486 Thread IDs are specified in hexadecimal. Currently supported actions are:
20492 Continue with signal @var{sig}. @var{sig} should be two hex digits.
20496 Step with signal @var{sig}. @var{sig} should be two hex digits.
20499 The optional @var{addr} argument normally associated with these packets is
20500 not supported in @code{vCont}.
20503 @xref{Stop Reply Packets}, for the reply specifications.
20505 @item @code{vCont?} --- extended resume query
20506 @cindex @code{vCont?} packet
20508 Query support for the @code{vCont} packet.
20512 @item @code{vCont}[;@var{action}]...
20513 The @code{vCont} packet is supported. Each @var{action} is a supported
20514 command in the @code{vCont} packet.
20516 The @code{vCont} packet is not supported.
20519 @item @code{V} --- reserved
20521 Reserved for future use.
20523 @item @code{w} --- reserved
20525 Reserved for future use.
20527 @item @code{W} --- reserved
20529 Reserved for future use.
20531 @item @code{x} --- reserved
20533 Reserved for future use.
20535 @item @code{X}@var{addr}@code{,}@var{length}@var{:}@var{XX@dots{}} --- write mem (binary)
20536 @cindex @code{X} packet
20538 @var{addr} is address, @var{length} is number of bytes, @var{XX@dots{}}
20539 is binary data. The characters @code{$}, @code{#}, and @code{0x7d} are
20540 escaped using @code{0x7d}.
20550 @item @code{y} --- reserved
20552 Reserved for future use.
20554 @item @code{Y} reserved
20556 Reserved for future use.
20558 @item @code{z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- remove breakpoint or watchpoint @strong{(draft)}
20559 @itemx @code{Z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- insert breakpoint or watchpoint @strong{(draft)}
20560 @anchor{insert breakpoint or watchpoint packet}
20561 @cindex @code{z} packet
20562 @cindex @code{Z} packets
20564 Insert (@code{Z}) or remove (@code{z}) a @var{type} breakpoint or
20565 watchpoint starting at address @var{address} and covering the next
20566 @var{length} bytes.
20568 Each breakpoint and watchpoint packet @var{type} is documented
20571 @emph{Implementation notes: A remote target shall return an empty string
20572 for an unrecognized breakpoint or watchpoint packet @var{type}. A
20573 remote target shall support either both or neither of a given
20574 @code{Z}@var{type}@dots{} and @code{z}@var{type}@dots{} packet pair. To
20575 avoid potential problems with duplicate packets, the operations should
20576 be implemented in an idempotent way.}
20578 @item @code{z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- remove memory breakpoint @strong{(draft)}
20579 @item @code{Z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- insert memory breakpoint @strong{(draft)}
20580 @cindex @code{z0} packet
20581 @cindex @code{Z0} packet
20583 Insert (@code{Z0}) or remove (@code{z0}) a memory breakpoint at address
20584 @code{addr} of size @code{length}.
20586 A memory breakpoint is implemented by replacing the instruction at
20587 @var{addr} with a software breakpoint or trap instruction. The
20588 @code{length} is used by targets that indicates the size of the
20589 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
20590 @sc{mips} can insert either a 2 or 4 byte breakpoint).
20592 @emph{Implementation note: It is possible for a target to copy or move
20593 code that contains memory breakpoints (e.g., when implementing
20594 overlays). The behavior of this packet, in the presence of such a
20595 target, is not defined.}
20607 @item @code{z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- remove hardware breakpoint @strong{(draft)}
20608 @item @code{Z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- insert hardware breakpoint @strong{(draft)}
20609 @cindex @code{z1} packet
20610 @cindex @code{Z1} packet
20612 Insert (@code{Z1}) or remove (@code{z1}) a hardware breakpoint at
20613 address @code{addr} of size @code{length}.
20615 A hardware breakpoint is implemented using a mechanism that is not
20616 dependant on being able to modify the target's memory.
20618 @emph{Implementation note: A hardware breakpoint is not affected by code
20631 @item @code{z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- remove write watchpoint @strong{(draft)}
20632 @item @code{Z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- insert write watchpoint @strong{(draft)}
20633 @cindex @code{z2} packet
20634 @cindex @code{Z2} packet
20636 Insert (@code{Z2}) or remove (@code{z2}) a write watchpoint.
20648 @item @code{z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- remove read watchpoint @strong{(draft)}
20649 @item @code{Z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- insert read watchpoint @strong{(draft)}
20650 @cindex @code{z3} packet
20651 @cindex @code{Z3} packet
20653 Insert (@code{Z3}) or remove (@code{z3}) a read watchpoint.
20665 @item @code{z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- remove access watchpoint @strong{(draft)}
20666 @item @code{Z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- insert access watchpoint @strong{(draft)}
20667 @cindex @code{z4} packet
20668 @cindex @code{Z4} packet
20670 Insert (@code{Z4}) or remove (@code{z4}) an access watchpoint.
20684 @node Stop Reply Packets
20685 @section Stop Reply Packets
20686 @cindex stop reply packets
20688 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
20689 receive any of the below as a reply. In the case of the @samp{C},
20690 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
20691 when the target halts. In the below the exact meaning of @samp{signal
20692 number} is poorly defined. In general one of the UNIX signal numbering
20693 conventions is used.
20698 @var{AA} is the signal number
20700 @item @code{T}@var{AA}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}
20701 @cindex @code{T} packet reply
20703 @var{AA} = two hex digit signal number; @var{n...} = register number
20704 (hex), @var{r...} = target byte ordered register contents, size defined
20705 by @code{DEPRECATED_REGISTER_RAW_SIZE}; @var{n...} = @samp{thread},
20706 @var{r...} = thread process ID, this is a hex integer; @var{n...} =
20707 (@samp{watch} | @samp{rwatch} | @samp{awatch}, @var{r...} = data
20708 address, this is a hex integer; @var{n...} = other string not starting
20709 with valid hex digit. @value{GDBN} should ignore this @var{n...},
20710 @var{r...} pair and go on to the next. This way we can extend the
20715 The process exited, and @var{AA} is the exit status. This is only
20716 applicable to certain targets.
20720 The process terminated with signal @var{AA}.
20722 @item O@var{XX@dots{}}
20724 @var{XX@dots{}} is hex encoding of @sc{ascii} data. This can happen at
20725 any time while the program is running and the debugger should continue
20726 to wait for @samp{W}, @samp{T}, etc.
20728 @item F@var{call-id}@code{,}@var{parameter@dots{}}
20730 @var{call-id} is the identifier which says which host system call should
20731 be called. This is just the name of the function. Translation into the
20732 correct system call is only applicable as it's defined in @value{GDBN}.
20733 @xref{File-I/O remote protocol extension}, for a list of implemented
20736 @var{parameter@dots{}} is a list of parameters as defined for this very
20739 The target replies with this packet when it expects @value{GDBN} to call
20740 a host system call on behalf of the target. @value{GDBN} replies with
20741 an appropriate @code{F} packet and keeps up waiting for the next reply
20742 packet from the target. The latest @samp{C}, @samp{c}, @samp{S} or
20743 @samp{s} action is expected to be continued.
20744 @xref{File-I/O remote protocol extension}, for more details.
20748 @node General Query Packets
20749 @section General Query Packets
20751 The following set and query packets have already been defined.
20755 @item @code{q}@code{C} --- current thread
20757 Return the current thread id.
20761 @item @code{QC}@var{pid}
20762 Where @var{pid} is a HEX encoded 16 bit process id.
20764 Any other reply implies the old pid.
20767 @item @code{q}@code{fThreadInfo} -- all thread ids
20769 @code{q}@code{sThreadInfo}
20771 Obtain a list of active thread ids from the target (OS). Since there
20772 may be too many active threads to fit into one reply packet, this query
20773 works iteratively: it may require more than one query/reply sequence to
20774 obtain the entire list of threads. The first query of the sequence will
20775 be the @code{qf}@code{ThreadInfo} query; subsequent queries in the
20776 sequence will be the @code{qs}@code{ThreadInfo} query.
20778 NOTE: replaces the @code{qL} query (see below).
20782 @item @code{m}@var{id}
20784 @item @code{m}@var{id},@var{id}@dots{}
20785 a comma-separated list of thread ids
20787 (lower case 'el') denotes end of list.
20790 In response to each query, the target will reply with a list of one or
20791 more thread ids, in big-endian hex, separated by commas. @value{GDBN}
20792 will respond to each reply with a request for more thread ids (using the
20793 @code{qs} form of the query), until the target responds with @code{l}
20794 (lower-case el, for @code{'last'}).
20796 @item @code{q}@code{ThreadExtraInfo}@code{,}@var{id} --- extra thread info
20798 Where @var{id} is a thread-id in big-endian hex. Obtain a printable
20799 string description of a thread's attributes from the target OS. This
20800 string may contain anything that the target OS thinks is interesting for
20801 @value{GDBN} to tell the user about the thread. The string is displayed
20802 in @value{GDBN}'s @samp{info threads} display. Some examples of
20803 possible thread extra info strings are ``Runnable'', or ``Blocked on
20808 @item @var{XX@dots{}}
20809 Where @var{XX@dots{}} is a hex encoding of @sc{ascii} data, comprising
20810 the printable string containing the extra information about the thread's
20814 @item @code{q}@code{L}@var{startflag}@var{threadcount}@var{nextthread} --- query @var{LIST} or @var{threadLIST} @strong{(deprecated)}
20816 Obtain thread information from RTOS. Where: @var{startflag} (one hex
20817 digit) is one to indicate the first query and zero to indicate a
20818 subsequent query; @var{threadcount} (two hex digits) is the maximum
20819 number of threads the response packet can contain; and @var{nextthread}
20820 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
20821 returned in the response as @var{argthread}.
20823 NOTE: this query is replaced by the @code{q}@code{fThreadInfo} query
20828 @item @code{q}@code{M}@var{count}@var{done}@var{argthread}@var{thread@dots{}}
20829 Where: @var{count} (two hex digits) is the number of threads being
20830 returned; @var{done} (one hex digit) is zero to indicate more threads
20831 and one indicates no further threads; @var{argthreadid} (eight hex
20832 digits) is @var{nextthread} from the request packet; @var{thread@dots{}}
20833 is a sequence of thread IDs from the target. @var{threadid} (eight hex
20834 digits). See @code{remote.c:parse_threadlist_response()}.
20837 @item @code{q}@code{CRC:}@var{addr}@code{,}@var{length} --- compute CRC of memory block
20841 @item @code{E}@var{NN}
20842 An error (such as memory fault)
20843 @item @code{C}@var{CRC32}
20844 A 32 bit cyclic redundancy check of the specified memory region.
20847 @item @code{q}@code{Offsets} --- query sect offs
20849 Get section offsets that the target used when re-locating the downloaded
20850 image. @emph{Note: while a @code{Bss} offset is included in the
20851 response, @value{GDBN} ignores this and instead applies the @code{Data}
20852 offset to the @code{Bss} section.}
20856 @item @code{Text=}@var{xxx}@code{;Data=}@var{yyy}@code{;Bss=}@var{zzz}
20859 @item @code{q}@code{P}@var{mode}@var{threadid} --- thread info request
20861 Returns information on @var{threadid}. Where: @var{mode} is a hex
20862 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
20869 See @code{remote.c:remote_unpack_thread_info_response()}.
20871 @item @code{q}@code{Rcmd,}@var{command} --- remote command
20873 @var{command} (hex encoded) is passed to the local interpreter for
20874 execution. Invalid commands should be reported using the output string.
20875 Before the final result packet, the target may also respond with a
20876 number of intermediate @code{O}@var{output} console output packets.
20877 @emph{Implementors should note that providing access to a stubs's
20878 interpreter may have security implications}.
20883 A command response with no output.
20885 A command response with the hex encoded output string @var{OUTPUT}.
20886 @item @code{E}@var{NN}
20887 Indicate a badly formed request.
20889 When @samp{q}@samp{Rcmd} is not recognized.
20892 @item @code{qSymbol::} --- symbol lookup
20894 Notify the target that @value{GDBN} is prepared to serve symbol lookup
20895 requests. Accept requests from the target for the values of symbols.
20900 The target does not need to look up any (more) symbols.
20901 @item @code{qSymbol:}@var{sym_name}
20902 The target requests the value of symbol @var{sym_name} (hex encoded).
20903 @value{GDBN} may provide the value by using the
20904 @code{qSymbol:}@var{sym_value}:@var{sym_name} message, described below.
20907 @item @code{qSymbol:}@var{sym_value}:@var{sym_name} --- symbol value
20909 Set the value of @var{sym_name} to @var{sym_value}.
20911 @var{sym_name} (hex encoded) is the name of a symbol whose value the
20912 target has previously requested.
20914 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
20915 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
20921 The target does not need to look up any (more) symbols.
20922 @item @code{qSymbol:}@var{sym_name}
20923 The target requests the value of a new symbol @var{sym_name} (hex
20924 encoded). @value{GDBN} will continue to supply the values of symbols
20925 (if available), until the target ceases to request them.
20928 @item @code{qPart}:@var{object}:@code{read}:@var{annex}:@var{offset},@var{length} --- read special data
20930 Read uninterpreted bytes from the target's special data area
20931 identified by the keyword @code{object}.
20932 Request @var{length} bytes starting at @var{offset} bytes into the data.
20933 The content and encoding of @var{annex} is specific to the object;
20934 it can supply additional details about what data to access.
20936 Here are the specific requests of this form defined so far.
20937 All @samp{@code{qPart}:@var{object}:@code{read}:@dots{}}
20938 requests use the same reply formats, listed below.
20941 @item @code{qPart}:@code{auxv}:@code{read}::@var{offset},@var{length}
20942 Access the target's @dfn{auxiliary vector}. @xref{Auxiliary Vector}.
20943 Note @var{annex} must be empty.
20949 The @var{offset} in the request is at the end of the data.
20950 There is no more data to be read.
20952 @item @var{XX@dots{}}
20953 Hex encoded data bytes read.
20954 This may be fewer bytes than the @var{length} in the request.
20957 The request was malformed, or @var{annex} was invalid.
20959 @item @code{E}@var{nn}
20960 The offset was invalid, or there was an error encountered reading the data.
20961 @var{nn} is a hex-encoded @code{errno} value.
20963 @item @code{""} (empty)
20964 An empty reply indicates the @var{object} or @var{annex} string was not
20965 recognized by the stub.
20968 @item @code{qPart}:@var{object}:@code{write}:@var{annex}:@var{offset}:@var{data@dots{}}
20970 Write uninterpreted bytes into the target's special data area
20971 identified by the keyword @code{object},
20972 starting at @var{offset} bytes into the data.
20973 @var{data@dots{}} is the hex-encoded data to be written.
20974 The content and encoding of @var{annex} is specific to the object;
20975 it can supply additional details about what data to access.
20977 No requests of this form are presently in use. This specification
20978 serves as a placeholder to document the common format that new
20979 specific request specifications ought to use.
20984 @var{nn} (hex encoded) is the number of bytes written.
20985 This may be fewer bytes than supplied in the request.
20988 The request was malformed, or @var{annex} was invalid.
20990 @item @code{E}@var{nn}
20991 The offset was invalid, or there was an error encountered writing the data.
20992 @var{nn} is a hex-encoded @code{errno} value.
20994 @item @code{""} (empty)
20995 An empty reply indicates the @var{object} or @var{annex} string was not
20996 recognized by the stub, or that the object does not support writing.
20999 @item @code{qPart}:@var{object}:@var{operation}:@dots{}
21000 Requests of this form may be added in the future. When a stub does
21001 not recognize the @var{object} keyword, or its support for
21002 @var{object} does not recognize the @var{operation} keyword,
21003 the stub must respond with an empty packet.
21006 @node Register Packet Format
21007 @section Register Packet Format
21009 The following @samp{g}/@samp{G} packets have previously been defined.
21010 In the below, some thirty-two bit registers are transferred as
21011 sixty-four bits. Those registers should be zero/sign extended (which?)
21012 to fill the space allocated. Register bytes are transfered in target
21013 byte order. The two nibbles within a register byte are transfered
21014 most-significant - least-significant.
21020 All registers are transfered as thirty-two bit quantities in the order:
21021 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
21022 registers; fsr; fir; fp.
21026 All registers are transfered as sixty-four bit quantities (including
21027 thirty-two bit registers such as @code{sr}). The ordering is the same
21035 Example sequence of a target being re-started. Notice how the restart
21036 does not get any direct output:
21041 @emph{target restarts}
21044 <- @code{T001:1234123412341234}
21048 Example sequence of a target being stepped by a single instruction:
21051 -> @code{G1445@dots{}}
21056 <- @code{T001:1234123412341234}
21060 <- @code{1455@dots{}}
21064 @node File-I/O remote protocol extension
21065 @section File-I/O remote protocol extension
21066 @cindex File-I/O remote protocol extension
21069 * File-I/O Overview::
21070 * Protocol basics::
21071 * The F request packet::
21072 * The F reply packet::
21073 * Memory transfer::
21074 * The Ctrl-C message::
21076 * The isatty call::
21077 * The system call::
21078 * List of supported calls::
21079 * Protocol specific representation of datatypes::
21081 * File-I/O Examples::
21084 @node File-I/O Overview
21085 @subsection File-I/O Overview
21086 @cindex file-i/o overview
21088 The File I/O remote protocol extension (short: File-I/O) allows the
21089 target to use the hosts file system and console I/O when calling various
21090 system calls. System calls on the target system are translated into a
21091 remote protocol packet to the host system which then performs the needed
21092 actions and returns with an adequate response packet to the target system.
21093 This simulates file system operations even on targets that lack file systems.
21095 The protocol is defined host- and target-system independent. It uses
21096 it's own independent representation of datatypes and values. Both,
21097 @value{GDBN} and the target's @value{GDBN} stub are responsible for
21098 translating the system dependent values into the unified protocol values
21099 when data is transmitted.
21101 The communication is synchronous. A system call is possible only
21102 when GDB is waiting for the @samp{C}, @samp{c}, @samp{S} or @samp{s}
21103 packets. While @value{GDBN} handles the request for a system call,
21104 the target is stopped to allow deterministic access to the target's
21105 memory. Therefore File-I/O is not interuptible by target signals. It
21106 is possible to interrupt File-I/O by a user interrupt (Ctrl-C), though.
21108 The target's request to perform a host system call does not finish
21109 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
21110 after finishing the system call, the target returns to continuing the
21111 previous activity (continue, step). No additional continue or step
21112 request from @value{GDBN} is required.
21115 (@value{GDBP}) continue
21116 <- target requests 'system call X'
21117 target is stopped, @value{GDBN} executes system call
21118 -> GDB returns result
21119 ... target continues, GDB returns to wait for the target
21120 <- target hits breakpoint and sends a Txx packet
21123 The protocol is only used for files on the host file system and
21124 for I/O on the console. Character or block special devices, pipes,
21125 named pipes or sockets or any other communication method on the host
21126 system are not supported by this protocol.
21128 @node Protocol basics
21129 @subsection Protocol basics
21130 @cindex protocol basics, file-i/o
21132 The File-I/O protocol uses the @code{F} packet, as request as well
21133 as as reply packet. Since a File-I/O system call can only occur when
21134 @value{GDBN} is waiting for the continuing or stepping target, the
21135 File-I/O request is a reply that @value{GDBN} has to expect as a result
21136 of a former @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
21137 This @code{F} packet contains all information needed to allow @value{GDBN}
21138 to call the appropriate host system call:
21142 A unique identifier for the requested system call.
21145 All parameters to the system call. Pointers are given as addresses
21146 in the target memory address space. Pointers to strings are given as
21147 pointer/length pair. Numerical values are given as they are.
21148 Numerical control values are given in a protocol specific representation.
21152 At that point @value{GDBN} has to perform the following actions.
21156 If parameter pointer values are given, which point to data needed as input
21157 to a system call, @value{GDBN} requests this data from the target with a
21158 standard @code{m} packet request. This additional communication has to be
21159 expected by the target implementation and is handled as any other @code{m}
21163 @value{GDBN} translates all value from protocol representation to host
21164 representation as needed. Datatypes are coerced into the host types.
21167 @value{GDBN} calls the system call
21170 It then coerces datatypes back to protocol representation.
21173 If pointer parameters in the request packet point to buffer space in which
21174 a system call is expected to copy data to, the data is transmitted to the
21175 target using a @code{M} or @code{X} packet. This packet has to be expected
21176 by the target implementation and is handled as any other @code{M} or @code{X}
21181 Eventually @value{GDBN} replies with another @code{F} packet which contains all
21182 necessary information for the target to continue. This at least contains
21189 @code{errno}, if has been changed by the system call.
21196 After having done the needed type and value coercion, the target continues
21197 the latest continue or step action.
21199 @node The F request packet
21200 @subsection The @code{F} request packet
21201 @cindex file-i/o request packet
21202 @cindex @code{F} request packet
21204 The @code{F} request packet has the following format:
21209 @code{F}@var{call-id}@code{,}@var{parameter@dots{}}
21212 @var{call-id} is the identifier to indicate the host system call to be called.
21213 This is just the name of the function.
21215 @var{parameter@dots{}} are the parameters to the system call.
21219 Parameters are hexadecimal integer values, either the real values in case
21220 of scalar datatypes, as pointers to target buffer space in case of compound
21221 datatypes and unspecified memory areas or as pointer/length pairs in case
21222 of string parameters. These are appended to the call-id, each separated
21223 from its predecessor by a comma. All values are transmitted in ASCII
21224 string representation, pointer/length pairs separated by a slash.
21226 @node The F reply packet
21227 @subsection The @code{F} reply packet
21228 @cindex file-i/o reply packet
21229 @cindex @code{F} reply packet
21231 The @code{F} reply packet has the following format:
21236 @code{F}@var{retcode}@code{,}@var{errno}@code{,}@var{Ctrl-C flag}@code{;}@var{call specific attachment}
21239 @var{retcode} is the return code of the system call as hexadecimal value.
21241 @var{errno} is the errno set by the call, in protocol specific representation.
21242 This parameter can be omitted if the call was successful.
21244 @var{Ctrl-C flag} is only send if the user requested a break. In this
21245 case, @var{errno} must be send as well, even if the call was successful.
21246 The @var{Ctrl-C flag} itself consists of the character 'C':
21253 or, if the call was interupted before the host call has been performed:
21260 assuming 4 is the protocol specific representation of @code{EINTR}.
21264 @node Memory transfer
21265 @subsection Memory transfer
21266 @cindex memory transfer, in file-i/o protocol
21268 Structured data which is transferred using a memory read or write as e.g.@:
21269 a @code{struct stat} is expected to be in a protocol specific format with
21270 all scalar multibyte datatypes being big endian. This should be done by
21271 the target before the @code{F} packet is sent resp.@: by @value{GDBN} before
21272 it transfers memory to the target. Transferred pointers to structured
21273 data should point to the already coerced data at any time.
21275 @node The Ctrl-C message
21276 @subsection The Ctrl-C message
21277 @cindex ctrl-c message, in file-i/o protocol
21279 A special case is, if the @var{Ctrl-C flag} is set in the @value{GDBN}
21280 reply packet. In this case the target should behave, as if it had
21281 gotten a break message. The meaning for the target is ``system call
21282 interupted by @code{SIGINT}''. Consequentially, the target should actually stop
21283 (as with a break message) and return to @value{GDBN} with a @code{T02}
21284 packet. In this case, it's important for the target to know, in which
21285 state the system call was interrupted. Since this action is by design
21286 not an atomic operation, we have to differ between two cases:
21290 The system call hasn't been performed on the host yet.
21293 The system call on the host has been finished.
21297 These two states can be distinguished by the target by the value of the
21298 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
21299 call hasn't been performed. This is equivalent to the @code{EINTR} handling
21300 on POSIX systems. In any other case, the target may presume that the
21301 system call has been finished --- successful or not --- and should behave
21302 as if the break message arrived right after the system call.
21304 @value{GDBN} must behave reliable. If the system call has not been called
21305 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
21306 @code{errno} in the packet. If the system call on the host has been finished
21307 before the user requests a break, the full action must be finshed by
21308 @value{GDBN}. This requires sending @code{M} or @code{X} packets as they fit.
21309 The @code{F} packet may only be send when either nothing has happened
21310 or the full action has been completed.
21313 @subsection Console I/O
21314 @cindex console i/o as part of file-i/o
21316 By default and if not explicitely closed by the target system, the file
21317 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
21318 on the @value{GDBN} console is handled as any other file output operation
21319 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
21320 by @value{GDBN} so that after the target read request from file descriptor
21321 0 all following typing is buffered until either one of the following
21326 The user presses @kbd{Ctrl-C}. The behaviour is as explained above, the
21328 system call is treated as finished.
21331 The user presses @kbd{Enter}. This is treated as end of input with a trailing
21335 The user presses @kbd{Ctrl-D}. This is treated as end of input. No trailing
21336 character, especially no Ctrl-D is appended to the input.
21340 If the user has typed more characters as fit in the buffer given to
21341 the read call, the trailing characters are buffered in @value{GDBN} until
21342 either another @code{read(0, @dots{})} is requested by the target or debugging
21343 is stopped on users request.
21345 @node The isatty call
21346 @subsection The isatty(3) call
21347 @cindex isatty call, file-i/o protocol
21349 A special case in this protocol is the library call @code{isatty} which
21350 is implemented as it's own call inside of this protocol. It returns
21351 1 to the target if the file descriptor given as parameter is attached
21352 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
21353 would require implementing @code{ioctl} and would be more complex than
21356 @node The system call
21357 @subsection The system(3) call
21358 @cindex system call, file-i/o protocol
21360 The other special case in this protocol is the @code{system} call which
21361 is implemented as it's own call, too. @value{GDBN} is taking over the full
21362 task of calling the necessary host calls to perform the @code{system}
21363 call. The return value of @code{system} is simplified before it's returned
21364 to the target. Basically, the only signal transmitted back is @code{EINTR}
21365 in case the user pressed @kbd{Ctrl-C}. Otherwise the return value consists
21366 entirely of the exit status of the called command.
21368 Due to security concerns, the @code{system} call is refused to be called
21369 by @value{GDBN} by default. The user has to allow this call explicitly by
21373 @kindex set remote system-call-allowed 1
21374 @item @code{set remote system-call-allowed 1}
21377 Disabling the @code{system} call is done by
21380 @kindex set remote system-call-allowed 0
21381 @item @code{set remote system-call-allowed 0}
21384 The current setting is shown by typing
21387 @kindex show remote system-call-allowed
21388 @item @code{show remote system-call-allowed}
21391 @node List of supported calls
21392 @subsection List of supported calls
21393 @cindex list of supported file-i/o calls
21410 @unnumberedsubsubsec open
21411 @cindex open, file-i/o system call
21415 int open(const char *pathname, int flags);
21416 int open(const char *pathname, int flags, mode_t mode);
21419 Fopen,pathptr/len,flags,mode
21423 @code{flags} is the bitwise or of the following values:
21427 If the file does not exist it will be created. The host
21428 rules apply as far as file ownership and time stamps
21432 When used with O_CREAT, if the file already exists it is
21433 an error and open() fails.
21436 If the file already exists and the open mode allows
21437 writing (O_RDWR or O_WRONLY is given) it will be
21438 truncated to length 0.
21441 The file is opened in append mode.
21444 The file is opened for reading only.
21447 The file is opened for writing only.
21450 The file is opened for reading and writing.
21453 Each other bit is silently ignored.
21458 @code{mode} is the bitwise or of the following values:
21462 User has read permission.
21465 User has write permission.
21468 Group has read permission.
21471 Group has write permission.
21474 Others have read permission.
21477 Others have write permission.
21480 Each other bit is silently ignored.
21485 @exdent Return value:
21486 open returns the new file descriptor or -1 if an error
21494 pathname already exists and O_CREAT and O_EXCL were used.
21497 pathname refers to a directory.
21500 The requested access is not allowed.
21503 pathname was too long.
21506 A directory component in pathname does not exist.
21509 pathname refers to a device, pipe, named pipe or socket.
21512 pathname refers to a file on a read-only filesystem and
21513 write access was requested.
21516 pathname is an invalid pointer value.
21519 No space on device to create the file.
21522 The process already has the maximum number of files open.
21525 The limit on the total number of files open on the system
21529 The call was interrupted by the user.
21533 @unnumberedsubsubsec close
21534 @cindex close, file-i/o system call
21543 @exdent Return value:
21544 close returns zero on success, or -1 if an error occurred.
21551 fd isn't a valid open file descriptor.
21554 The call was interrupted by the user.
21558 @unnumberedsubsubsec read
21559 @cindex read, file-i/o system call
21563 int read(int fd, void *buf, unsigned int count);
21566 Fread,fd,bufptr,count
21568 @exdent Return value:
21569 On success, the number of bytes read is returned.
21570 Zero indicates end of file. If count is zero, read
21571 returns zero as well. On error, -1 is returned.
21578 fd is not a valid file descriptor or is not open for
21582 buf is an invalid pointer value.
21585 The call was interrupted by the user.
21589 @unnumberedsubsubsec write
21590 @cindex write, file-i/o system call
21594 int write(int fd, const void *buf, unsigned int count);
21597 Fwrite,fd,bufptr,count
21599 @exdent Return value:
21600 On success, the number of bytes written are returned.
21601 Zero indicates nothing was written. On error, -1
21609 fd is not a valid file descriptor or is not open for
21613 buf is an invalid pointer value.
21616 An attempt was made to write a file that exceeds the
21617 host specific maximum file size allowed.
21620 No space on device to write the data.
21623 The call was interrupted by the user.
21627 @unnumberedsubsubsec lseek
21628 @cindex lseek, file-i/o system call
21632 long lseek (int fd, long offset, int flag);
21635 Flseek,fd,offset,flag
21638 @code{flag} is one of:
21642 The offset is set to offset bytes.
21645 The offset is set to its current location plus offset
21649 The offset is set to the size of the file plus offset
21654 @exdent Return value:
21655 On success, the resulting unsigned offset in bytes from
21656 the beginning of the file is returned. Otherwise, a
21657 value of -1 is returned.
21664 fd is not a valid open file descriptor.
21667 fd is associated with the @value{GDBN} console.
21670 flag is not a proper value.
21673 The call was interrupted by the user.
21677 @unnumberedsubsubsec rename
21678 @cindex rename, file-i/o system call
21682 int rename(const char *oldpath, const char *newpath);
21685 Frename,oldpathptr/len,newpathptr/len
21687 @exdent Return value:
21688 On success, zero is returned. On error, -1 is returned.
21695 newpath is an existing directory, but oldpath is not a
21699 newpath is a non-empty directory.
21702 oldpath or newpath is a directory that is in use by some
21706 An attempt was made to make a directory a subdirectory
21710 A component used as a directory in oldpath or new
21711 path is not a directory. Or oldpath is a directory
21712 and newpath exists but is not a directory.
21715 oldpathptr or newpathptr are invalid pointer values.
21718 No access to the file or the path of the file.
21722 oldpath or newpath was too long.
21725 A directory component in oldpath or newpath does not exist.
21728 The file is on a read-only filesystem.
21731 The device containing the file has no room for the new
21735 The call was interrupted by the user.
21739 @unnumberedsubsubsec unlink
21740 @cindex unlink, file-i/o system call
21744 int unlink(const char *pathname);
21747 Funlink,pathnameptr/len
21749 @exdent Return value:
21750 On success, zero is returned. On error, -1 is returned.
21757 No access to the file or the path of the file.
21760 The system does not allow unlinking of directories.
21763 The file pathname cannot be unlinked because it's
21764 being used by another process.
21767 pathnameptr is an invalid pointer value.
21770 pathname was too long.
21773 A directory component in pathname does not exist.
21776 A component of the path is not a directory.
21779 The file is on a read-only filesystem.
21782 The call was interrupted by the user.
21786 @unnumberedsubsubsec stat/fstat
21787 @cindex fstat, file-i/o system call
21788 @cindex stat, file-i/o system call
21792 int stat(const char *pathname, struct stat *buf);
21793 int fstat(int fd, struct stat *buf);
21796 Fstat,pathnameptr/len,bufptr
21799 @exdent Return value:
21800 On success, zero is returned. On error, -1 is returned.
21807 fd is not a valid open file.
21810 A directory component in pathname does not exist or the
21811 path is an empty string.
21814 A component of the path is not a directory.
21817 pathnameptr is an invalid pointer value.
21820 No access to the file or the path of the file.
21823 pathname was too long.
21826 The call was interrupted by the user.
21830 @unnumberedsubsubsec gettimeofday
21831 @cindex gettimeofday, file-i/o system call
21835 int gettimeofday(struct timeval *tv, void *tz);
21838 Fgettimeofday,tvptr,tzptr
21840 @exdent Return value:
21841 On success, 0 is returned, -1 otherwise.
21848 tz is a non-NULL pointer.
21851 tvptr and/or tzptr is an invalid pointer value.
21855 @unnumberedsubsubsec isatty
21856 @cindex isatty, file-i/o system call
21860 int isatty(int fd);
21865 @exdent Return value:
21866 Returns 1 if fd refers to the @value{GDBN} console, 0 otherwise.
21873 The call was interrupted by the user.
21877 @unnumberedsubsubsec system
21878 @cindex system, file-i/o system call
21882 int system(const char *command);
21885 Fsystem,commandptr/len
21887 @exdent Return value:
21888 The value returned is -1 on error and the return status
21889 of the command otherwise. Only the exit status of the
21890 command is returned, which is extracted from the hosts
21891 system return value by calling WEXITSTATUS(retval).
21892 In case /bin/sh could not be executed, 127 is returned.
21899 The call was interrupted by the user.
21902 @node Protocol specific representation of datatypes
21903 @subsection Protocol specific representation of datatypes
21904 @cindex protocol specific representation of datatypes, in file-i/o protocol
21907 * Integral datatypes::
21913 @node Integral datatypes
21914 @unnumberedsubsubsec Integral datatypes
21915 @cindex integral datatypes, in file-i/o protocol
21917 The integral datatypes used in the system calls are
21920 int@r{,} unsigned int@r{,} long@r{,} unsigned long@r{,} mode_t @r{and} time_t
21923 @code{Int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
21924 implemented as 32 bit values in this protocol.
21926 @code{Long} and @code{unsigned long} are implemented as 64 bit types.
21928 @xref{Limits}, for corresponding MIN and MAX values (similar to those
21929 in @file{limits.h}) to allow range checking on host and target.
21931 @code{time_t} datatypes are defined as seconds since the Epoch.
21933 All integral datatypes transferred as part of a memory read or write of a
21934 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
21937 @node Pointer values
21938 @unnumberedsubsubsec Pointer values
21939 @cindex pointer values, in file-i/o protocol
21941 Pointers to target data are transmitted as they are. An exception
21942 is made for pointers to buffers for which the length isn't
21943 transmitted as part of the function call, namely strings. Strings
21944 are transmitted as a pointer/length pair, both as hex values, e.g.@:
21951 which is a pointer to data of length 18 bytes at position 0x1aaf.
21952 The length is defined as the full string length in bytes, including
21953 the trailing null byte. Example:
21956 ``hello, world'' at address 0x123456
21967 @unnumberedsubsubsec struct stat
21968 @cindex struct stat, in file-i/o protocol
21970 The buffer of type struct stat used by the target and @value{GDBN} is defined
21975 unsigned int st_dev; /* device */
21976 unsigned int st_ino; /* inode */
21977 mode_t st_mode; /* protection */
21978 unsigned int st_nlink; /* number of hard links */
21979 unsigned int st_uid; /* user ID of owner */
21980 unsigned int st_gid; /* group ID of owner */
21981 unsigned int st_rdev; /* device type (if inode device) */
21982 unsigned long st_size; /* total size, in bytes */
21983 unsigned long st_blksize; /* blocksize for filesystem I/O */
21984 unsigned long st_blocks; /* number of blocks allocated */
21985 time_t st_atime; /* time of last access */
21986 time_t st_mtime; /* time of last modification */
21987 time_t st_ctime; /* time of last change */
21991 The integral datatypes are conforming to the definitions given in the
21992 approriate section (see @ref{Integral datatypes}, for details) so this
21993 structure is of size 64 bytes.
21995 The values of several fields have a restricted meaning and/or
22002 st_ino: No valid meaning for the target. Transmitted unchanged.
22004 st_mode: Valid mode bits are described in Appendix C. Any other
22005 bits have currently no meaning for the target.
22007 st_uid: No valid meaning for the target. Transmitted unchanged.
22009 st_gid: No valid meaning for the target. Transmitted unchanged.
22011 st_rdev: No valid meaning for the target. Transmitted unchanged.
22013 st_atime, st_mtime, st_ctime:
22014 These values have a host and file system dependent
22015 accuracy. Especially on Windows hosts the file systems
22016 don't support exact timing values.
22019 The target gets a struct stat of the above representation and is
22020 responsible to coerce it to the target representation before
22023 Note that due to size differences between the host and target
22024 representation of stat members, these members could eventually
22025 get truncated on the target.
22027 @node struct timeval
22028 @unnumberedsubsubsec struct timeval
22029 @cindex struct timeval, in file-i/o protocol
22031 The buffer of type struct timeval used by the target and @value{GDBN}
22032 is defined as follows:
22036 time_t tv_sec; /* second */
22037 long tv_usec; /* microsecond */
22041 The integral datatypes are conforming to the definitions given in the
22042 approriate section (see @ref{Integral datatypes}, for details) so this
22043 structure is of size 8 bytes.
22046 @subsection Constants
22047 @cindex constants, in file-i/o protocol
22049 The following values are used for the constants inside of the
22050 protocol. @value{GDBN} and target are resposible to translate these
22051 values before and after the call as needed.
22062 @unnumberedsubsubsec Open flags
22063 @cindex open flags, in file-i/o protocol
22065 All values are given in hexadecimal representation.
22077 @node mode_t values
22078 @unnumberedsubsubsec mode_t values
22079 @cindex mode_t values, in file-i/o protocol
22081 All values are given in octal representation.
22098 @unnumberedsubsubsec Errno values
22099 @cindex errno values, in file-i/o protocol
22101 All values are given in decimal representation.
22126 EUNKNOWN is used as a fallback error value if a host system returns
22127 any error value not in the list of supported error numbers.
22130 @unnumberedsubsubsec Lseek flags
22131 @cindex lseek flags, in file-i/o protocol
22140 @unnumberedsubsubsec Limits
22141 @cindex limits, in file-i/o protocol
22143 All values are given in decimal representation.
22146 INT_MIN -2147483648
22148 UINT_MAX 4294967295
22149 LONG_MIN -9223372036854775808
22150 LONG_MAX 9223372036854775807
22151 ULONG_MAX 18446744073709551615
22154 @node File-I/O Examples
22155 @subsection File-I/O Examples
22156 @cindex file-i/o examples
22158 Example sequence of a write call, file descriptor 3, buffer is at target
22159 address 0x1234, 6 bytes should be written:
22162 <- @code{Fwrite,3,1234,6}
22163 @emph{request memory read from target}
22166 @emph{return "6 bytes written"}
22170 Example sequence of a read call, file descriptor 3, buffer is at target
22171 address 0x1234, 6 bytes should be read:
22174 <- @code{Fread,3,1234,6}
22175 @emph{request memory write to target}
22176 -> @code{X1234,6:XXXXXX}
22177 @emph{return "6 bytes read"}
22181 Example sequence of a read call, call fails on the host due to invalid
22182 file descriptor (EBADF):
22185 <- @code{Fread,3,1234,6}
22189 Example sequence of a read call, user presses Ctrl-C before syscall on
22193 <- @code{Fread,3,1234,6}
22198 Example sequence of a read call, user presses Ctrl-C after syscall on
22202 <- @code{Fread,3,1234,6}
22203 -> @code{X1234,6:XXXXXX}
22207 @include agentexpr.texi
22221 % I think something like @colophon should be in texinfo. In the
22223 \long\def\colophon{\hbox to0pt{}\vfill
22224 \centerline{The body of this manual is set in}
22225 \centerline{\fontname\tenrm,}
22226 \centerline{with headings in {\bf\fontname\tenbf}}
22227 \centerline{and examples in {\tt\fontname\tentt}.}
22228 \centerline{{\it\fontname\tenit\/},}
22229 \centerline{{\bf\fontname\tenbf}, and}
22230 \centerline{{\sl\fontname\tensl\/}}
22231 \centerline{are used for emphasis.}\vfill}
22233 % Blame: doc@cygnus.com, 1991.