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 @cindex elaboration phase
1764 Some programs contain an @dfn{elaboration} phase where some startup code is
1765 executed before the main procedure is called. This depends on the
1766 languages used to write your program. In C@t{++}, for instance,
1767 constructors for static and global objects are executed before
1768 @code{main} is called. It is therefore possible that the debugger stops
1769 before reaching the main procedure. However, the temporary breakpoint
1770 will remain to halt execution.
1772 Specify the arguments to give to your program as arguments to the
1773 @samp{start} command. These arguments will be given verbatim to the
1774 underlying @samp{run} command. Note that the same arguments will be
1775 reused if no argument is provided during subsequent calls to
1776 @samp{start} or @samp{run}.
1778 It is sometimes necessary to debug the program during elaboration. In
1779 these cases, using the @code{start} command would stop the execution of
1780 your program too late, as the program would have already completed the
1781 elaboration phase. Under these circumstances, insert breakpoints in your
1782 elaboration code before running your program.
1786 @section Your program's arguments
1788 @cindex arguments (to your program)
1789 The arguments to your program can be specified by the arguments of the
1791 They are passed to a shell, which expands wildcard characters and
1792 performs redirection of I/O, and thence to your program. Your
1793 @code{SHELL} environment variable (if it exists) specifies what shell
1794 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1795 the default shell (@file{/bin/sh} on Unix).
1797 On non-Unix systems, the program is usually invoked directly by
1798 @value{GDBN}, which emulates I/O redirection via the appropriate system
1799 calls, and the wildcard characters are expanded by the startup code of
1800 the program, not by the shell.
1802 @code{run} with no arguments uses the same arguments used by the previous
1803 @code{run}, or those set by the @code{set args} command.
1808 Specify the arguments to be used the next time your program is run. If
1809 @code{set args} has no arguments, @code{run} executes your program
1810 with no arguments. Once you have run your program with arguments,
1811 using @code{set args} before the next @code{run} is the only way to run
1812 it again without arguments.
1816 Show the arguments to give your program when it is started.
1820 @section Your program's environment
1822 @cindex environment (of your program)
1823 The @dfn{environment} consists of a set of environment variables and
1824 their values. Environment variables conventionally record such things as
1825 your user name, your home directory, your terminal type, and your search
1826 path for programs to run. Usually you set up environment variables with
1827 the shell and they are inherited by all the other programs you run. When
1828 debugging, it can be useful to try running your program with a modified
1829 environment without having to start @value{GDBN} over again.
1833 @item path @var{directory}
1834 Add @var{directory} to the front of the @code{PATH} environment variable
1835 (the search path for executables) that will be passed to your program.
1836 The value of @code{PATH} used by @value{GDBN} does not change.
1837 You may specify several directory names, separated by whitespace or by a
1838 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1839 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1840 is moved to the front, so it is searched sooner.
1842 You can use the string @samp{$cwd} to refer to whatever is the current
1843 working directory at the time @value{GDBN} searches the path. If you
1844 use @samp{.} instead, it refers to the directory where you executed the
1845 @code{path} command. @value{GDBN} replaces @samp{.} in the
1846 @var{directory} argument (with the current path) before adding
1847 @var{directory} to the search path.
1848 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1849 @c document that, since repeating it would be a no-op.
1853 Display the list of search paths for executables (the @code{PATH}
1854 environment variable).
1856 @kindex show environment
1857 @item show environment @r{[}@var{varname}@r{]}
1858 Print the value of environment variable @var{varname} to be given to
1859 your program when it starts. If you do not supply @var{varname},
1860 print the names and values of all environment variables to be given to
1861 your program. You can abbreviate @code{environment} as @code{env}.
1863 @kindex set environment
1864 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1865 Set environment variable @var{varname} to @var{value}. The value
1866 changes for your program only, not for @value{GDBN} itself. @var{value} may
1867 be any string; the values of environment variables are just strings, and
1868 any interpretation is supplied by your program itself. The @var{value}
1869 parameter is optional; if it is eliminated, the variable is set to a
1871 @c "any string" here does not include leading, trailing
1872 @c blanks. Gnu asks: does anyone care?
1874 For example, this command:
1881 tells the debugged program, when subsequently run, that its user is named
1882 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
1883 are not actually required.)
1885 @kindex unset environment
1886 @item unset environment @var{varname}
1887 Remove variable @var{varname} from the environment to be passed to your
1888 program. This is different from @samp{set env @var{varname} =};
1889 @code{unset environment} removes the variable from the environment,
1890 rather than assigning it an empty value.
1893 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
1895 by your @code{SHELL} environment variable if it exists (or
1896 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
1897 that runs an initialization file---such as @file{.cshrc} for C-shell, or
1898 @file{.bashrc} for BASH---any variables you set in that file affect
1899 your program. You may wish to move setting of environment variables to
1900 files that are only run when you sign on, such as @file{.login} or
1903 @node Working Directory
1904 @section Your program's working directory
1906 @cindex working directory (of your program)
1907 Each time you start your program with @code{run}, it inherits its
1908 working directory from the current working directory of @value{GDBN}.
1909 The @value{GDBN} working directory is initially whatever it inherited
1910 from its parent process (typically the shell), but you can specify a new
1911 working directory in @value{GDBN} with the @code{cd} command.
1913 The @value{GDBN} working directory also serves as a default for the commands
1914 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
1919 @item cd @var{directory}
1920 Set the @value{GDBN} working directory to @var{directory}.
1924 Print the @value{GDBN} working directory.
1927 It is generally impossible to find the current working directory of
1928 the process being debugged (since a program can change its directory
1929 during its run). If you work on a system where @value{GDBN} is
1930 configured with the @file{/proc} support, you can use the @code{info
1931 proc} command (@pxref{SVR4 Process Information}) to find out the
1932 current working directory of the debuggee.
1935 @section Your program's input and output
1940 By default, the program you run under @value{GDBN} does input and output to
1941 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
1942 to its own terminal modes to interact with you, but it records the terminal
1943 modes your program was using and switches back to them when you continue
1944 running your program.
1947 @kindex info terminal
1949 Displays information recorded by @value{GDBN} about the terminal modes your
1953 You can redirect your program's input and/or output using shell
1954 redirection with the @code{run} command. For example,
1961 starts your program, diverting its output to the file @file{outfile}.
1964 @cindex controlling terminal
1965 Another way to specify where your program should do input and output is
1966 with the @code{tty} command. This command accepts a file name as
1967 argument, and causes this file to be the default for future @code{run}
1968 commands. It also resets the controlling terminal for the child
1969 process, for future @code{run} commands. For example,
1976 directs that processes started with subsequent @code{run} commands
1977 default to do input and output on the terminal @file{/dev/ttyb} and have
1978 that as their controlling terminal.
1980 An explicit redirection in @code{run} overrides the @code{tty} command's
1981 effect on the input/output device, but not its effect on the controlling
1984 When you use the @code{tty} command or redirect input in the @code{run}
1985 command, only the input @emph{for your program} is affected. The input
1986 for @value{GDBN} still comes from your terminal.
1989 @section Debugging an already-running process
1994 @item attach @var{process-id}
1995 This command attaches to a running process---one that was started
1996 outside @value{GDBN}. (@code{info files} shows your active
1997 targets.) The command takes as argument a process ID. The usual way to
1998 find out the process-id of a Unix process is with the @code{ps} utility,
1999 or with the @samp{jobs -l} shell command.
2001 @code{attach} does not repeat if you press @key{RET} a second time after
2002 executing the command.
2005 To use @code{attach}, your program must be running in an environment
2006 which supports processes; for example, @code{attach} does not work for
2007 programs on bare-board targets that lack an operating system. You must
2008 also have permission to send the process a signal.
2010 When you use @code{attach}, the debugger finds the program running in
2011 the process first by looking in the current working directory, then (if
2012 the program is not found) by using the source file search path
2013 (@pxref{Source Path, ,Specifying source directories}). You can also use
2014 the @code{file} command to load the program. @xref{Files, ,Commands to
2017 The first thing @value{GDBN} does after arranging to debug the specified
2018 process is to stop it. You can examine and modify an attached process
2019 with all the @value{GDBN} commands that are ordinarily available when
2020 you start processes with @code{run}. You can insert breakpoints; you
2021 can step and continue; you can modify storage. If you would rather the
2022 process continue running, you may use the @code{continue} command after
2023 attaching @value{GDBN} to the process.
2028 When you have finished debugging the attached process, you can use the
2029 @code{detach} command to release it from @value{GDBN} control. Detaching
2030 the process continues its execution. After the @code{detach} command,
2031 that process and @value{GDBN} become completely independent once more, and you
2032 are ready to @code{attach} another process or start one with @code{run}.
2033 @code{detach} does not repeat if you press @key{RET} again after
2034 executing the command.
2037 If you exit @value{GDBN} or use the @code{run} command while you have an
2038 attached process, you kill that process. By default, @value{GDBN} asks
2039 for confirmation if you try to do either of these things; you can
2040 control whether or not you need to confirm by using the @code{set
2041 confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
2045 @section Killing the child process
2050 Kill the child process in which your program is running under @value{GDBN}.
2053 This command is useful if you wish to debug a core dump instead of a
2054 running process. @value{GDBN} ignores any core dump file while your program
2057 On some operating systems, a program cannot be executed outside @value{GDBN}
2058 while you have breakpoints set on it inside @value{GDBN}. You can use the
2059 @code{kill} command in this situation to permit running your program
2060 outside the debugger.
2062 The @code{kill} command is also useful if you wish to recompile and
2063 relink your program, since on many systems it is impossible to modify an
2064 executable file while it is running in a process. In this case, when you
2065 next type @code{run}, @value{GDBN} notices that the file has changed, and
2066 reads the symbol table again (while trying to preserve your current
2067 breakpoint settings).
2070 @section Debugging programs with multiple threads
2072 @cindex threads of execution
2073 @cindex multiple threads
2074 @cindex switching threads
2075 In some operating systems, such as HP-UX and Solaris, a single program
2076 may have more than one @dfn{thread} of execution. The precise semantics
2077 of threads differ from one operating system to another, but in general
2078 the threads of a single program are akin to multiple processes---except
2079 that they share one address space (that is, they can all examine and
2080 modify the same variables). On the other hand, each thread has its own
2081 registers and execution stack, and perhaps private memory.
2083 @value{GDBN} provides these facilities for debugging multi-thread
2087 @item automatic notification of new threads
2088 @item @samp{thread @var{threadno}}, a command to switch among threads
2089 @item @samp{info threads}, a command to inquire about existing threads
2090 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2091 a command to apply a command to a list of threads
2092 @item thread-specific breakpoints
2096 @emph{Warning:} These facilities are not yet available on every
2097 @value{GDBN} configuration where the operating system supports threads.
2098 If your @value{GDBN} does not support threads, these commands have no
2099 effect. For example, a system without thread support shows no output
2100 from @samp{info threads}, and always rejects the @code{thread} command,
2104 (@value{GDBP}) info threads
2105 (@value{GDBP}) thread 1
2106 Thread ID 1 not known. Use the "info threads" command to
2107 see the IDs of currently known threads.
2109 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2110 @c doesn't support threads"?
2113 @cindex focus of debugging
2114 @cindex current thread
2115 The @value{GDBN} thread debugging facility allows you to observe all
2116 threads while your program runs---but whenever @value{GDBN} takes
2117 control, one thread in particular is always the focus of debugging.
2118 This thread is called the @dfn{current thread}. Debugging commands show
2119 program information from the perspective of the current thread.
2121 @cindex @code{New} @var{systag} message
2122 @cindex thread identifier (system)
2123 @c FIXME-implementors!! It would be more helpful if the [New...] message
2124 @c included GDB's numeric thread handle, so you could just go to that
2125 @c thread without first checking `info threads'.
2126 Whenever @value{GDBN} detects a new thread in your program, it displays
2127 the target system's identification for the thread with a message in the
2128 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2129 whose form varies depending on the particular system. For example, on
2130 LynxOS, you might see
2133 [New process 35 thread 27]
2137 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2138 the @var{systag} is simply something like @samp{process 368}, with no
2141 @c FIXME!! (1) Does the [New...] message appear even for the very first
2142 @c thread of a program, or does it only appear for the
2143 @c second---i.e.@: when it becomes obvious we have a multithread
2145 @c (2) *Is* there necessarily a first thread always? Or do some
2146 @c multithread systems permit starting a program with multiple
2147 @c threads ab initio?
2149 @cindex thread number
2150 @cindex thread identifier (GDB)
2151 For debugging purposes, @value{GDBN} associates its own thread
2152 number---always a single integer---with each thread in your program.
2155 @kindex info threads
2157 Display a summary of all threads currently in your
2158 program. @value{GDBN} displays for each thread (in this order):
2161 @item the thread number assigned by @value{GDBN}
2163 @item the target system's thread identifier (@var{systag})
2165 @item the current stack frame summary for that thread
2169 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2170 indicates the current thread.
2174 @c end table here to get a little more width for example
2177 (@value{GDBP}) info threads
2178 3 process 35 thread 27 0x34e5 in sigpause ()
2179 2 process 35 thread 23 0x34e5 in sigpause ()
2180 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2186 @cindex debugging multithreaded programs (on HP-UX)
2187 @cindex thread identifier (GDB), on HP-UX
2188 For debugging purposes, @value{GDBN} associates its own thread
2189 number---a small integer assigned in thread-creation order---with each
2190 thread in your program.
2192 @cindex @code{New} @var{systag} message, on HP-UX
2193 @cindex thread identifier (system), on HP-UX
2194 @c FIXME-implementors!! It would be more helpful if the [New...] message
2195 @c included GDB's numeric thread handle, so you could just go to that
2196 @c thread without first checking `info threads'.
2197 Whenever @value{GDBN} detects a new thread in your program, it displays
2198 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2199 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2200 whose form varies depending on the particular system. For example, on
2204 [New thread 2 (system thread 26594)]
2208 when @value{GDBN} notices a new thread.
2211 @kindex info threads (HP-UX)
2213 Display a summary of all threads currently in your
2214 program. @value{GDBN} displays for each thread (in this order):
2217 @item the thread number assigned by @value{GDBN}
2219 @item the target system's thread identifier (@var{systag})
2221 @item the current stack frame summary for that thread
2225 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2226 indicates the current thread.
2230 @c end table here to get a little more width for example
2233 (@value{GDBP}) info threads
2234 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2236 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2237 from /usr/lib/libc.2
2238 1 system thread 27905 0x7b003498 in _brk () \@*
2239 from /usr/lib/libc.2
2243 @kindex thread @var{threadno}
2244 @item thread @var{threadno}
2245 Make thread number @var{threadno} the current thread. The command
2246 argument @var{threadno} is the internal @value{GDBN} thread number, as
2247 shown in the first field of the @samp{info threads} display.
2248 @value{GDBN} responds by displaying the system identifier of the thread
2249 you selected, and its current stack frame summary:
2252 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2253 (@value{GDBP}) thread 2
2254 [Switching to process 35 thread 23]
2255 0x34e5 in sigpause ()
2259 As with the @samp{[New @dots{}]} message, the form of the text after
2260 @samp{Switching to} depends on your system's conventions for identifying
2263 @item thread apply [@var{threadno}] [@var{all}] @var{args}
2264 The @code{thread apply} command allows you to apply a command to one or
2265 more threads. Specify the numbers of the threads that you want affected
2266 with the command argument @var{threadno}. @var{threadno} is the internal
2267 @value{GDBN} thread number, as shown in the first field of the @samp{info
2268 threads} display. To apply a command to all threads, use
2269 @code{thread apply all} @var{args}.
2272 @cindex automatic thread selection
2273 @cindex switching threads automatically
2274 @cindex threads, automatic switching
2275 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2276 signal, it automatically selects the thread where that breakpoint or
2277 signal happened. @value{GDBN} alerts you to the context switch with a
2278 message of the form @samp{[Switching to @var{systag}]} to identify the
2281 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2282 more information about how @value{GDBN} behaves when you stop and start
2283 programs with multiple threads.
2285 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2286 watchpoints in programs with multiple threads.
2289 @section Debugging programs with multiple processes
2291 @cindex fork, debugging programs which call
2292 @cindex multiple processes
2293 @cindex processes, multiple
2294 On most systems, @value{GDBN} has no special support for debugging
2295 programs which create additional processes using the @code{fork}
2296 function. When a program forks, @value{GDBN} will continue to debug the
2297 parent process and the child process will run unimpeded. If you have
2298 set a breakpoint in any code which the child then executes, the child
2299 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2300 will cause it to terminate.
2302 However, if you want to debug the child process there is a workaround
2303 which isn't too painful. Put a call to @code{sleep} in the code which
2304 the child process executes after the fork. It may be useful to sleep
2305 only if a certain environment variable is set, or a certain file exists,
2306 so that the delay need not occur when you don't want to run @value{GDBN}
2307 on the child. While the child is sleeping, use the @code{ps} program to
2308 get its process ID. Then tell @value{GDBN} (a new invocation of
2309 @value{GDBN} if you are also debugging the parent process) to attach to
2310 the child process (@pxref{Attach}). From that point on you can debug
2311 the child process just like any other process which you attached to.
2313 On some systems, @value{GDBN} provides support for debugging programs that
2314 create additional processes using the @code{fork} or @code{vfork} functions.
2315 Currently, the only platforms with this feature are HP-UX (11.x and later
2316 only?) and GNU/Linux (kernel version 2.5.60 and later).
2318 By default, when a program forks, @value{GDBN} will continue to debug
2319 the parent process and the child process will run unimpeded.
2321 If you want to follow the child process instead of the parent process,
2322 use the command @w{@code{set follow-fork-mode}}.
2325 @kindex set follow-fork-mode
2326 @item set follow-fork-mode @var{mode}
2327 Set the debugger response to a program call of @code{fork} or
2328 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2329 process. The @var{mode} can be:
2333 The original process is debugged after a fork. The child process runs
2334 unimpeded. This is the default.
2337 The new process is debugged after a fork. The parent process runs
2342 @item show follow-fork-mode
2343 Display the current debugger response to a @code{fork} or @code{vfork} call.
2346 If you ask to debug a child process and a @code{vfork} is followed by an
2347 @code{exec}, @value{GDBN} executes the new target up to the first
2348 breakpoint in the new target. If you have a breakpoint set on
2349 @code{main} in your original program, the breakpoint will also be set on
2350 the child process's @code{main}.
2352 When a child process is spawned by @code{vfork}, you cannot debug the
2353 child or parent until an @code{exec} call completes.
2355 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2356 call executes, the new target restarts. To restart the parent process,
2357 use the @code{file} command with the parent executable name as its
2360 You can use the @code{catch} command to make @value{GDBN} stop whenever
2361 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2362 Catchpoints, ,Setting catchpoints}.
2365 @chapter Stopping and Continuing
2367 The principal purposes of using a debugger are so that you can stop your
2368 program before it terminates; or so that, if your program runs into
2369 trouble, you can investigate and find out why.
2371 Inside @value{GDBN}, your program may stop for any of several reasons,
2372 such as a signal, a breakpoint, or reaching a new line after a
2373 @value{GDBN} command such as @code{step}. You may then examine and
2374 change variables, set new breakpoints or remove old ones, and then
2375 continue execution. Usually, the messages shown by @value{GDBN} provide
2376 ample explanation of the status of your program---but you can also
2377 explicitly request this information at any time.
2380 @kindex info program
2382 Display information about the status of your program: whether it is
2383 running or not, what process it is, and why it stopped.
2387 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2388 * Continuing and Stepping:: Resuming execution
2390 * Thread Stops:: Stopping and starting multi-thread programs
2394 @section Breakpoints, watchpoints, and catchpoints
2397 A @dfn{breakpoint} makes your program stop whenever a certain point in
2398 the program is reached. For each breakpoint, you can add conditions to
2399 control in finer detail whether your program stops. You can set
2400 breakpoints with the @code{break} command and its variants (@pxref{Set
2401 Breaks, ,Setting breakpoints}), to specify the place where your program
2402 should stop by line number, function name or exact address in the
2405 In HP-UX, SunOS 4.x, SVR4, and Alpha OSF/1 configurations, you can set
2406 breakpoints in shared libraries before the executable is run. There is
2407 a minor limitation on HP-UX systems: you must wait until the executable
2408 is run in order to set breakpoints in shared library routines that are
2409 not called directly by the program (for example, routines that are
2410 arguments in a @code{pthread_create} call).
2413 @cindex memory tracing
2414 @cindex breakpoint on memory address
2415 @cindex breakpoint on variable modification
2416 A @dfn{watchpoint} is a special breakpoint that stops your program
2417 when the value of an expression changes. You must use a different
2418 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
2419 watchpoints}), but aside from that, you can manage a watchpoint like
2420 any other breakpoint: you enable, disable, and delete both breakpoints
2421 and watchpoints using the same commands.
2423 You can arrange to have values from your program displayed automatically
2424 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2428 @cindex breakpoint on events
2429 A @dfn{catchpoint} is another special breakpoint that stops your program
2430 when a certain kind of event occurs, such as the throwing of a C@t{++}
2431 exception or the loading of a library. As with watchpoints, you use a
2432 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2433 catchpoints}), but aside from that, you can manage a catchpoint like any
2434 other breakpoint. (To stop when your program receives a signal, use the
2435 @code{handle} command; see @ref{Signals, ,Signals}.)
2437 @cindex breakpoint numbers
2438 @cindex numbers for breakpoints
2439 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2440 catchpoint when you create it; these numbers are successive integers
2441 starting with one. In many of the commands for controlling various
2442 features of breakpoints you use the breakpoint number to say which
2443 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2444 @dfn{disabled}; if disabled, it has no effect on your program until you
2447 @cindex breakpoint ranges
2448 @cindex ranges of breakpoints
2449 Some @value{GDBN} commands accept a range of breakpoints on which to
2450 operate. A breakpoint range is either a single breakpoint number, like
2451 @samp{5}, or two such numbers, in increasing order, separated by a
2452 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2453 all breakpoint in that range are operated on.
2456 * Set Breaks:: Setting breakpoints
2457 * Set Watchpoints:: Setting watchpoints
2458 * Set Catchpoints:: Setting catchpoints
2459 * Delete Breaks:: Deleting breakpoints
2460 * Disabling:: Disabling breakpoints
2461 * Conditions:: Break conditions
2462 * Break Commands:: Breakpoint command lists
2463 * Breakpoint Menus:: Breakpoint menus
2464 * Error in Breakpoints:: ``Cannot insert breakpoints''
2465 * Breakpoint related warnings:: ``Breakpoint address adjusted...''
2469 @subsection Setting breakpoints
2471 @c FIXME LMB what does GDB do if no code on line of breakpt?
2472 @c consider in particular declaration with/without initialization.
2474 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2477 @kindex b @r{(@code{break})}
2478 @vindex $bpnum@r{, convenience variable}
2479 @cindex latest breakpoint
2480 Breakpoints are set with the @code{break} command (abbreviated
2481 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2482 number of the breakpoint you've set most recently; see @ref{Convenience
2483 Vars,, Convenience variables}, for a discussion of what you can do with
2484 convenience variables.
2486 You have several ways to say where the breakpoint should go.
2489 @item break @var{function}
2490 Set a breakpoint at entry to function @var{function}.
2491 When using source languages that permit overloading of symbols, such as
2492 C@t{++}, @var{function} may refer to more than one possible place to break.
2493 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2495 @item break +@var{offset}
2496 @itemx break -@var{offset}
2497 Set a breakpoint some number of lines forward or back from the position
2498 at which execution stopped in the currently selected @dfn{stack frame}.
2499 (@xref{Frames, ,Frames}, for a description of stack frames.)
2501 @item break @var{linenum}
2502 Set a breakpoint at line @var{linenum} in the current source file.
2503 The current source file is the last file whose source text was printed.
2504 The breakpoint will stop your program just before it executes any of the
2507 @item break @var{filename}:@var{linenum}
2508 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2510 @item break @var{filename}:@var{function}
2511 Set a breakpoint at entry to function @var{function} found in file
2512 @var{filename}. Specifying a file name as well as a function name is
2513 superfluous except when multiple files contain similarly named
2516 @item break *@var{address}
2517 Set a breakpoint at address @var{address}. You can use this to set
2518 breakpoints in parts of your program which do not have debugging
2519 information or source files.
2522 When called without any arguments, @code{break} sets a breakpoint at
2523 the next instruction to be executed in the selected stack frame
2524 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2525 innermost, this makes your program stop as soon as control
2526 returns to that frame. This is similar to the effect of a
2527 @code{finish} command in the frame inside the selected frame---except
2528 that @code{finish} does not leave an active breakpoint. If you use
2529 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2530 the next time it reaches the current location; this may be useful
2533 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2534 least one instruction has been executed. If it did not do this, you
2535 would be unable to proceed past a breakpoint without first disabling the
2536 breakpoint. This rule applies whether or not the breakpoint already
2537 existed when your program stopped.
2539 @item break @dots{} if @var{cond}
2540 Set a breakpoint with condition @var{cond}; evaluate the expression
2541 @var{cond} each time the breakpoint is reached, and stop only if the
2542 value is nonzero---that is, if @var{cond} evaluates as true.
2543 @samp{@dots{}} stands for one of the possible arguments described
2544 above (or no argument) specifying where to break. @xref{Conditions,
2545 ,Break conditions}, for more information on breakpoint conditions.
2548 @item tbreak @var{args}
2549 Set a breakpoint enabled only for one stop. @var{args} are the
2550 same as for the @code{break} command, and the breakpoint is set in the same
2551 way, but the breakpoint is automatically deleted after the first time your
2552 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2555 @item hbreak @var{args}
2556 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2557 @code{break} command and the breakpoint is set in the same way, but the
2558 breakpoint requires hardware support and some target hardware may not
2559 have this support. The main purpose of this is EPROM/ROM code
2560 debugging, so you can set a breakpoint at an instruction without
2561 changing the instruction. This can be used with the new trap-generation
2562 provided by SPARClite DSU and some x86-based targets. These targets
2563 will generate traps when a program accesses some data or instruction
2564 address that is assigned to the debug registers. However the hardware
2565 breakpoint registers can take a limited number of breakpoints. For
2566 example, on the DSU, only two data breakpoints can be set at a time, and
2567 @value{GDBN} will reject this command if more than two are used. Delete
2568 or disable unused hardware breakpoints before setting new ones
2569 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2570 @xref{set remote hardware-breakpoint-limit}.
2574 @item thbreak @var{args}
2575 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2576 are the same as for the @code{hbreak} command and the breakpoint is set in
2577 the same way. However, like the @code{tbreak} command,
2578 the breakpoint is automatically deleted after the
2579 first time your program stops there. Also, like the @code{hbreak}
2580 command, the breakpoint requires hardware support and some target hardware
2581 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2582 See also @ref{Conditions, ,Break conditions}.
2585 @cindex regular expression
2586 @item rbreak @var{regex}
2587 Set breakpoints on all functions matching the regular expression
2588 @var{regex}. This command sets an unconditional breakpoint on all
2589 matches, printing a list of all breakpoints it set. Once these
2590 breakpoints are set, they are treated just like the breakpoints set with
2591 the @code{break} command. You can delete them, disable them, or make
2592 them conditional the same way as any other breakpoint.
2594 The syntax of the regular expression is the standard one used with tools
2595 like @file{grep}. Note that this is different from the syntax used by
2596 shells, so for instance @code{foo*} matches all functions that include
2597 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2598 @code{.*} leading and trailing the regular expression you supply, so to
2599 match only functions that begin with @code{foo}, use @code{^foo}.
2601 @cindex non-member C@t{++} functions, set breakpoint in
2602 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2603 breakpoints on overloaded functions that are not members of any special
2606 @cindex set breakpoints on all functions
2607 The @code{rbreak} command can be used to set breakpoints in
2608 @strong{all} the functions in a program, like this:
2611 (@value{GDBP}) rbreak .
2614 @kindex info breakpoints
2615 @cindex @code{$_} and @code{info breakpoints}
2616 @item info breakpoints @r{[}@var{n}@r{]}
2617 @itemx info break @r{[}@var{n}@r{]}
2618 @itemx info watchpoints @r{[}@var{n}@r{]}
2619 Print a table of all breakpoints, watchpoints, and catchpoints set and
2620 not deleted, with the following columns for each breakpoint:
2623 @item Breakpoint Numbers
2625 Breakpoint, watchpoint, or catchpoint.
2627 Whether the breakpoint is marked to be disabled or deleted when hit.
2628 @item Enabled or Disabled
2629 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2630 that are not enabled.
2632 Where the breakpoint is in your program, as a memory address. If the
2633 breakpoint is pending (see below for details) on a future load of a shared library, the address
2634 will be listed as @samp{<PENDING>}.
2636 Where the breakpoint is in the source for your program, as a file and
2637 line number. For a pending breakpoint, the original string passed to
2638 the breakpoint command will be listed as it cannot be resolved until
2639 the appropriate shared library is loaded in the future.
2643 If a breakpoint is conditional, @code{info break} shows the condition on
2644 the line following the affected breakpoint; breakpoint commands, if any,
2645 are listed after that. A pending breakpoint is allowed to have a condition
2646 specified for it. The condition is not parsed for validity until a shared
2647 library is loaded that allows the pending breakpoint to resolve to a
2651 @code{info break} with a breakpoint
2652 number @var{n} as argument lists only that breakpoint. The
2653 convenience variable @code{$_} and the default examining-address for
2654 the @code{x} command are set to the address of the last breakpoint
2655 listed (@pxref{Memory, ,Examining memory}).
2658 @code{info break} displays a count of the number of times the breakpoint
2659 has been hit. This is especially useful in conjunction with the
2660 @code{ignore} command. You can ignore a large number of breakpoint
2661 hits, look at the breakpoint info to see how many times the breakpoint
2662 was hit, and then run again, ignoring one less than that number. This
2663 will get you quickly to the last hit of that breakpoint.
2666 @value{GDBN} allows you to set any number of breakpoints at the same place in
2667 your program. There is nothing silly or meaningless about this. When
2668 the breakpoints are conditional, this is even useful
2669 (@pxref{Conditions, ,Break conditions}).
2671 @cindex pending breakpoints
2672 If a specified breakpoint location cannot be found, it may be due to the fact
2673 that the location is in a shared library that is yet to be loaded. In such
2674 a case, you may want @value{GDBN} to create a special breakpoint (known as
2675 a @dfn{pending breakpoint}) that
2676 attempts to resolve itself in the future when an appropriate shared library
2679 Pending breakpoints are useful to set at the start of your
2680 @value{GDBN} session for locations that you know will be dynamically loaded
2681 later by the program being debugged. When shared libraries are loaded,
2682 a check is made to see if the load resolves any pending breakpoint locations.
2683 If a pending breakpoint location gets resolved,
2684 a regular breakpoint is created and the original pending breakpoint is removed.
2686 @value{GDBN} provides some additional commands for controlling pending
2689 @kindex set breakpoint pending
2690 @kindex show breakpoint pending
2692 @item set breakpoint pending auto
2693 This is the default behavior. When @value{GDBN} cannot find the breakpoint
2694 location, it queries you whether a pending breakpoint should be created.
2696 @item set breakpoint pending on
2697 This indicates that an unrecognized breakpoint location should automatically
2698 result in a pending breakpoint being created.
2700 @item set breakpoint pending off
2701 This indicates that pending breakpoints are not to be created. Any
2702 unrecognized breakpoint location results in an error. This setting does
2703 not affect any pending breakpoints previously created.
2705 @item show breakpoint pending
2706 Show the current behavior setting for creating pending breakpoints.
2709 @cindex operations allowed on pending breakpoints
2710 Normal breakpoint operations apply to pending breakpoints as well. You may
2711 specify a condition for a pending breakpoint and/or commands to run when the
2712 breakpoint is reached. You can also enable or disable
2713 the pending breakpoint. When you specify a condition for a pending breakpoint,
2714 the parsing of the condition will be deferred until the point where the
2715 pending breakpoint location is resolved. Disabling a pending breakpoint
2716 tells @value{GDBN} to not attempt to resolve the breakpoint on any subsequent
2717 shared library load. When a pending breakpoint is re-enabled,
2718 @value{GDBN} checks to see if the location is already resolved.
2719 This is done because any number of shared library loads could have
2720 occurred since the time the breakpoint was disabled and one or more
2721 of these loads could resolve the location.
2723 @cindex negative breakpoint numbers
2724 @cindex internal @value{GDBN} breakpoints
2725 @value{GDBN} itself sometimes sets breakpoints in your program for
2726 special purposes, such as proper handling of @code{longjmp} (in C
2727 programs). These internal breakpoints are assigned negative numbers,
2728 starting with @code{-1}; @samp{info breakpoints} does not display them.
2729 You can see these breakpoints with the @value{GDBN} maintenance command
2730 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
2733 @node Set Watchpoints
2734 @subsection Setting watchpoints
2736 @cindex setting watchpoints
2737 @cindex software watchpoints
2738 @cindex hardware watchpoints
2739 You can use a watchpoint to stop execution whenever the value of an
2740 expression changes, without having to predict a particular place where
2743 Depending on your system, watchpoints may be implemented in software or
2744 hardware. @value{GDBN} does software watchpointing by single-stepping your
2745 program and testing the variable's value each time, which is hundreds of
2746 times slower than normal execution. (But this may still be worth it, to
2747 catch errors where you have no clue what part of your program is the
2750 On some systems, such as HP-UX, @sc{gnu}/Linux and some other x86-based targets,
2751 @value{GDBN} includes support for
2752 hardware watchpoints, which do not slow down the running of your
2757 @item watch @var{expr}
2758 Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
2759 is written into by the program and its value changes.
2762 @item rwatch @var{expr}
2763 Set a watchpoint that will break when watch @var{expr} is read by the program.
2766 @item awatch @var{expr}
2767 Set a watchpoint that will break when @var{expr} is either read or written into
2770 @kindex info watchpoints
2771 @item info watchpoints
2772 This command prints a list of watchpoints, breakpoints, and catchpoints;
2773 it is the same as @code{info break}.
2776 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
2777 watchpoints execute very quickly, and the debugger reports a change in
2778 value at the exact instruction where the change occurs. If @value{GDBN}
2779 cannot set a hardware watchpoint, it sets a software watchpoint, which
2780 executes more slowly and reports the change in value at the next
2781 statement, not the instruction, after the change occurs.
2783 When you issue the @code{watch} command, @value{GDBN} reports
2786 Hardware watchpoint @var{num}: @var{expr}
2790 if it was able to set a hardware watchpoint.
2792 Currently, the @code{awatch} and @code{rwatch} commands can only set
2793 hardware watchpoints, because accesses to data that don't change the
2794 value of the watched expression cannot be detected without examining
2795 every instruction as it is being executed, and @value{GDBN} does not do
2796 that currently. If @value{GDBN} finds that it is unable to set a
2797 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
2798 will print a message like this:
2801 Expression cannot be implemented with read/access watchpoint.
2804 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
2805 data type of the watched expression is wider than what a hardware
2806 watchpoint on the target machine can handle. For example, some systems
2807 can only watch regions that are up to 4 bytes wide; on such systems you
2808 cannot set hardware watchpoints for an expression that yields a
2809 double-precision floating-point number (which is typically 8 bytes
2810 wide). As a work-around, it might be possible to break the large region
2811 into a series of smaller ones and watch them with separate watchpoints.
2813 If you set too many hardware watchpoints, @value{GDBN} might be unable
2814 to insert all of them when you resume the execution of your program.
2815 Since the precise number of active watchpoints is unknown until such
2816 time as the program is about to be resumed, @value{GDBN} might not be
2817 able to warn you about this when you set the watchpoints, and the
2818 warning will be printed only when the program is resumed:
2821 Hardware watchpoint @var{num}: Could not insert watchpoint
2825 If this happens, delete or disable some of the watchpoints.
2827 The SPARClite DSU will generate traps when a program accesses some data
2828 or instruction address that is assigned to the debug registers. For the
2829 data addresses, DSU facilitates the @code{watch} command. However the
2830 hardware breakpoint registers can only take two data watchpoints, and
2831 both watchpoints must be the same kind. For example, you can set two
2832 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
2833 @strong{or} two with @code{awatch} commands, but you cannot set one
2834 watchpoint with one command and the other with a different command.
2835 @value{GDBN} will reject the command if you try to mix watchpoints.
2836 Delete or disable unused watchpoint commands before setting new ones.
2838 If you call a function interactively using @code{print} or @code{call},
2839 any watchpoints you have set will be inactive until @value{GDBN} reaches another
2840 kind of breakpoint or the call completes.
2842 @value{GDBN} automatically deletes watchpoints that watch local
2843 (automatic) variables, or expressions that involve such variables, when
2844 they go out of scope, that is, when the execution leaves the block in
2845 which these variables were defined. In particular, when the program
2846 being debugged terminates, @emph{all} local variables go out of scope,
2847 and so only watchpoints that watch global variables remain set. If you
2848 rerun the program, you will need to set all such watchpoints again. One
2849 way of doing that would be to set a code breakpoint at the entry to the
2850 @code{main} function and when it breaks, set all the watchpoints.
2853 @cindex watchpoints and threads
2854 @cindex threads and watchpoints
2855 @emph{Warning:} In multi-thread programs, watchpoints have only limited
2856 usefulness. With the current watchpoint implementation, @value{GDBN}
2857 can only watch the value of an expression @emph{in a single thread}. If
2858 you are confident that the expression can only change due to the current
2859 thread's activity (and if you are also confident that no other thread
2860 can become current), then you can use watchpoints as usual. However,
2861 @value{GDBN} may not notice when a non-current thread's activity changes
2864 @c FIXME: this is almost identical to the previous paragraph.
2865 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
2866 have only limited usefulness. If @value{GDBN} creates a software
2867 watchpoint, it can only watch the value of an expression @emph{in a
2868 single thread}. If you are confident that the expression can only
2869 change due to the current thread's activity (and if you are also
2870 confident that no other thread can become current), then you can use
2871 software watchpoints as usual. However, @value{GDBN} may not notice
2872 when a non-current thread's activity changes the expression. (Hardware
2873 watchpoints, in contrast, watch an expression in all threads.)
2876 @xref{set remote hardware-watchpoint-limit}.
2878 @node Set Catchpoints
2879 @subsection Setting catchpoints
2880 @cindex catchpoints, setting
2881 @cindex exception handlers
2882 @cindex event handling
2884 You can use @dfn{catchpoints} to cause the debugger to stop for certain
2885 kinds of program events, such as C@t{++} exceptions or the loading of a
2886 shared library. Use the @code{catch} command to set a catchpoint.
2890 @item catch @var{event}
2891 Stop when @var{event} occurs. @var{event} can be any of the following:
2894 @cindex stop on C@t{++} exceptions
2895 The throwing of a C@t{++} exception.
2898 The catching of a C@t{++} exception.
2901 @cindex break on fork/exec
2902 A call to @code{exec}. This is currently only available for HP-UX.
2905 A call to @code{fork}. This is currently only available for HP-UX.
2908 A call to @code{vfork}. This is currently only available for HP-UX.
2911 @itemx load @var{libname}
2912 @cindex break on load/unload of shared library
2913 The dynamic loading of any shared library, or the loading of the library
2914 @var{libname}. This is currently only available for HP-UX.
2917 @itemx unload @var{libname}
2918 The unloading of any dynamically loaded shared library, or the unloading
2919 of the library @var{libname}. This is currently only available for HP-UX.
2922 @item tcatch @var{event}
2923 Set a catchpoint that is enabled only for one stop. The catchpoint is
2924 automatically deleted after the first time the event is caught.
2928 Use the @code{info break} command to list the current catchpoints.
2930 There are currently some limitations to C@t{++} exception handling
2931 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
2935 If you call a function interactively, @value{GDBN} normally returns
2936 control to you when the function has finished executing. If the call
2937 raises an exception, however, the call may bypass the mechanism that
2938 returns control to you and cause your program either to abort or to
2939 simply continue running until it hits a breakpoint, catches a signal
2940 that @value{GDBN} is listening for, or exits. This is the case even if
2941 you set a catchpoint for the exception; catchpoints on exceptions are
2942 disabled within interactive calls.
2945 You cannot raise an exception interactively.
2948 You cannot install an exception handler interactively.
2951 @cindex raise exceptions
2952 Sometimes @code{catch} is not the best way to debug exception handling:
2953 if you need to know exactly where an exception is raised, it is better to
2954 stop @emph{before} the exception handler is called, since that way you
2955 can see the stack before any unwinding takes place. If you set a
2956 breakpoint in an exception handler instead, it may not be easy to find
2957 out where the exception was raised.
2959 To stop just before an exception handler is called, you need some
2960 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
2961 raised by calling a library function named @code{__raise_exception}
2962 which has the following ANSI C interface:
2965 /* @var{addr} is where the exception identifier is stored.
2966 @var{id} is the exception identifier. */
2967 void __raise_exception (void **addr, void *id);
2971 To make the debugger catch all exceptions before any stack
2972 unwinding takes place, set a breakpoint on @code{__raise_exception}
2973 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
2975 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
2976 that depends on the value of @var{id}, you can stop your program when
2977 a specific exception is raised. You can use multiple conditional
2978 breakpoints to stop your program when any of a number of exceptions are
2983 @subsection Deleting breakpoints
2985 @cindex clearing breakpoints, watchpoints, catchpoints
2986 @cindex deleting breakpoints, watchpoints, catchpoints
2987 It is often necessary to eliminate a breakpoint, watchpoint, or
2988 catchpoint once it has done its job and you no longer want your program
2989 to stop there. This is called @dfn{deleting} the breakpoint. A
2990 breakpoint that has been deleted no longer exists; it is forgotten.
2992 With the @code{clear} command you can delete breakpoints according to
2993 where they are in your program. With the @code{delete} command you can
2994 delete individual breakpoints, watchpoints, or catchpoints by specifying
2995 their breakpoint numbers.
2997 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
2998 automatically ignores breakpoints on the first instruction to be executed
2999 when you continue execution without changing the execution address.
3004 Delete any breakpoints at the next instruction to be executed in the
3005 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
3006 the innermost frame is selected, this is a good way to delete a
3007 breakpoint where your program just stopped.
3009 @item clear @var{function}
3010 @itemx clear @var{filename}:@var{function}
3011 Delete any breakpoints set at entry to the function @var{function}.
3013 @item clear @var{linenum}
3014 @itemx clear @var{filename}:@var{linenum}
3015 Delete any breakpoints set at or within the code of the specified line.
3017 @cindex delete breakpoints
3019 @kindex d @r{(@code{delete})}
3020 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3021 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3022 ranges specified as arguments. If no argument is specified, delete all
3023 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3024 confirm off}). You can abbreviate this command as @code{d}.
3028 @subsection Disabling breakpoints
3030 @cindex enable/disable a breakpoint
3031 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3032 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3033 it had been deleted, but remembers the information on the breakpoint so
3034 that you can @dfn{enable} it again later.
3036 You disable and enable breakpoints, watchpoints, and catchpoints with
3037 the @code{enable} and @code{disable} commands, optionally specifying one
3038 or more breakpoint numbers as arguments. Use @code{info break} or
3039 @code{info watch} to print a list of breakpoints, watchpoints, and
3040 catchpoints if you do not know which numbers to use.
3042 A breakpoint, watchpoint, or catchpoint can have any of four different
3043 states of enablement:
3047 Enabled. The breakpoint stops your program. A breakpoint set
3048 with the @code{break} command starts out in this state.
3050 Disabled. The breakpoint has no effect on your program.
3052 Enabled once. The breakpoint stops your program, but then becomes
3055 Enabled for deletion. The breakpoint stops your program, but
3056 immediately after it does so it is deleted permanently. A breakpoint
3057 set with the @code{tbreak} command starts out in this state.
3060 You can use the following commands to enable or disable breakpoints,
3061 watchpoints, and catchpoints:
3065 @kindex dis @r{(@code{disable})}
3066 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3067 Disable the specified breakpoints---or all breakpoints, if none are
3068 listed. A disabled breakpoint has no effect but is not forgotten. All
3069 options such as ignore-counts, conditions and commands are remembered in
3070 case the breakpoint is enabled again later. You may abbreviate
3071 @code{disable} as @code{dis}.
3074 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3075 Enable the specified breakpoints (or all defined breakpoints). They
3076 become effective once again in stopping your program.
3078 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3079 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3080 of these breakpoints immediately after stopping your program.
3082 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3083 Enable the specified breakpoints to work once, then die. @value{GDBN}
3084 deletes any of these breakpoints as soon as your program stops there.
3087 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3088 @c confusing: tbreak is also initially enabled.
3089 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3090 ,Setting breakpoints}), breakpoints that you set are initially enabled;
3091 subsequently, they become disabled or enabled only when you use one of
3092 the commands above. (The command @code{until} can set and delete a
3093 breakpoint of its own, but it does not change the state of your other
3094 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3098 @subsection Break conditions
3099 @cindex conditional breakpoints
3100 @cindex breakpoint conditions
3102 @c FIXME what is scope of break condition expr? Context where wanted?
3103 @c in particular for a watchpoint?
3104 The simplest sort of breakpoint breaks every time your program reaches a
3105 specified place. You can also specify a @dfn{condition} for a
3106 breakpoint. A condition is just a Boolean expression in your
3107 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3108 a condition evaluates the expression each time your program reaches it,
3109 and your program stops only if the condition is @emph{true}.
3111 This is the converse of using assertions for program validation; in that
3112 situation, you want to stop when the assertion is violated---that is,
3113 when the condition is false. In C, if you want to test an assertion expressed
3114 by the condition @var{assert}, you should set the condition
3115 @samp{! @var{assert}} on the appropriate breakpoint.
3117 Conditions are also accepted for watchpoints; you may not need them,
3118 since a watchpoint is inspecting the value of an expression anyhow---but
3119 it might be simpler, say, to just set a watchpoint on a variable name,
3120 and specify a condition that tests whether the new value is an interesting
3123 Break conditions can have side effects, and may even call functions in
3124 your program. This can be useful, for example, to activate functions
3125 that log program progress, or to use your own print functions to
3126 format special data structures. The effects are completely predictable
3127 unless there is another enabled breakpoint at the same address. (In
3128 that case, @value{GDBN} might see the other breakpoint first and stop your
3129 program without checking the condition of this one.) Note that
3130 breakpoint commands are usually more convenient and flexible than break
3132 purpose of performing side effects when a breakpoint is reached
3133 (@pxref{Break Commands, ,Breakpoint command lists}).
3135 Break conditions can be specified when a breakpoint is set, by using
3136 @samp{if} in the arguments to the @code{break} command. @xref{Set
3137 Breaks, ,Setting breakpoints}. They can also be changed at any time
3138 with the @code{condition} command.
3140 You can also use the @code{if} keyword with the @code{watch} command.
3141 The @code{catch} command does not recognize the @code{if} keyword;
3142 @code{condition} is the only way to impose a further condition on a
3147 @item condition @var{bnum} @var{expression}
3148 Specify @var{expression} as the break condition for breakpoint,
3149 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3150 breakpoint @var{bnum} stops your program only if the value of
3151 @var{expression} is true (nonzero, in C). When you use
3152 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3153 syntactic correctness, and to determine whether symbols in it have
3154 referents in the context of your breakpoint. If @var{expression} uses
3155 symbols not referenced in the context of the breakpoint, @value{GDBN}
3156 prints an error message:
3159 No symbol "foo" in current context.
3164 not actually evaluate @var{expression} at the time the @code{condition}
3165 command (or a command that sets a breakpoint with a condition, like
3166 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3168 @item condition @var{bnum}
3169 Remove the condition from breakpoint number @var{bnum}. It becomes
3170 an ordinary unconditional breakpoint.
3173 @cindex ignore count (of breakpoint)
3174 A special case of a breakpoint condition is to stop only when the
3175 breakpoint has been reached a certain number of times. This is so
3176 useful that there is a special way to do it, using the @dfn{ignore
3177 count} of the breakpoint. Every breakpoint has an ignore count, which
3178 is an integer. Most of the time, the ignore count is zero, and
3179 therefore has no effect. But if your program reaches a breakpoint whose
3180 ignore count is positive, then instead of stopping, it just decrements
3181 the ignore count by one and continues. As a result, if the ignore count
3182 value is @var{n}, the breakpoint does not stop the next @var{n} times
3183 your program reaches it.
3187 @item ignore @var{bnum} @var{count}
3188 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3189 The next @var{count} times the breakpoint is reached, your program's
3190 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3193 To make the breakpoint stop the next time it is reached, specify
3196 When you use @code{continue} to resume execution of your program from a
3197 breakpoint, you can specify an ignore count directly as an argument to
3198 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3199 Stepping,,Continuing and stepping}.
3201 If a breakpoint has a positive ignore count and a condition, the
3202 condition is not checked. Once the ignore count reaches zero,
3203 @value{GDBN} resumes checking the condition.
3205 You could achieve the effect of the ignore count with a condition such
3206 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3207 is decremented each time. @xref{Convenience Vars, ,Convenience
3211 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3214 @node Break Commands
3215 @subsection Breakpoint command lists
3217 @cindex breakpoint commands
3218 You can give any breakpoint (or watchpoint or catchpoint) a series of
3219 commands to execute when your program stops due to that breakpoint. For
3220 example, you might want to print the values of certain expressions, or
3221 enable other breakpoints.
3226 @item commands @r{[}@var{bnum}@r{]}
3227 @itemx @dots{} @var{command-list} @dots{}
3229 Specify a list of commands for breakpoint number @var{bnum}. The commands
3230 themselves appear on the following lines. Type a line containing just
3231 @code{end} to terminate the commands.
3233 To remove all commands from a breakpoint, type @code{commands} and
3234 follow it immediately with @code{end}; that is, give no commands.
3236 With no @var{bnum} argument, @code{commands} refers to the last
3237 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3238 recently encountered).
3241 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3242 disabled within a @var{command-list}.
3244 You can use breakpoint commands to start your program up again. Simply
3245 use the @code{continue} command, or @code{step}, or any other command
3246 that resumes execution.
3248 Any other commands in the command list, after a command that resumes
3249 execution, are ignored. This is because any time you resume execution
3250 (even with a simple @code{next} or @code{step}), you may encounter
3251 another breakpoint---which could have its own command list, leading to
3252 ambiguities about which list to execute.
3255 If the first command you specify in a command list is @code{silent}, the
3256 usual message about stopping at a breakpoint is not printed. This may
3257 be desirable for breakpoints that are to print a specific message and
3258 then continue. If none of the remaining commands print anything, you
3259 see no sign that the breakpoint was reached. @code{silent} is
3260 meaningful only at the beginning of a breakpoint command list.
3262 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3263 print precisely controlled output, and are often useful in silent
3264 breakpoints. @xref{Output, ,Commands for controlled output}.
3266 For example, here is how you could use breakpoint commands to print the
3267 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3273 printf "x is %d\n",x
3278 One application for breakpoint commands is to compensate for one bug so
3279 you can test for another. Put a breakpoint just after the erroneous line
3280 of code, give it a condition to detect the case in which something
3281 erroneous has been done, and give it commands to assign correct values
3282 to any variables that need them. End with the @code{continue} command
3283 so that your program does not stop, and start with the @code{silent}
3284 command so that no output is produced. Here is an example:
3295 @node Breakpoint Menus
3296 @subsection Breakpoint menus
3298 @cindex symbol overloading
3300 Some programming languages (notably C@t{++} and Objective-C) permit a
3301 single function name
3302 to be defined several times, for application in different contexts.
3303 This is called @dfn{overloading}. When a function name is overloaded,
3304 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3305 a breakpoint. If you realize this is a problem, you can use
3306 something like @samp{break @var{function}(@var{types})} to specify which
3307 particular version of the function you want. Otherwise, @value{GDBN} offers
3308 you a menu of numbered choices for different possible breakpoints, and
3309 waits for your selection with the prompt @samp{>}. The first two
3310 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3311 sets a breakpoint at each definition of @var{function}, and typing
3312 @kbd{0} aborts the @code{break} command without setting any new
3315 For example, the following session excerpt shows an attempt to set a
3316 breakpoint at the overloaded symbol @code{String::after}.
3317 We choose three particular definitions of that function name:
3319 @c FIXME! This is likely to change to show arg type lists, at least
3322 (@value{GDBP}) b String::after
3325 [2] file:String.cc; line number:867
3326 [3] file:String.cc; line number:860
3327 [4] file:String.cc; line number:875
3328 [5] file:String.cc; line number:853
3329 [6] file:String.cc; line number:846
3330 [7] file:String.cc; line number:735
3332 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3333 Breakpoint 2 at 0xb344: file String.cc, line 875.
3334 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3335 Multiple breakpoints were set.
3336 Use the "delete" command to delete unwanted
3342 @c @ifclear BARETARGET
3343 @node Error in Breakpoints
3344 @subsection ``Cannot insert breakpoints''
3346 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3348 Under some operating systems, breakpoints cannot be used in a program if
3349 any other process is running that program. In this situation,
3350 attempting to run or continue a program with a breakpoint causes
3351 @value{GDBN} to print an error message:
3354 Cannot insert breakpoints.
3355 The same program may be running in another process.
3358 When this happens, you have three ways to proceed:
3362 Remove or disable the breakpoints, then continue.
3365 Suspend @value{GDBN}, and copy the file containing your program to a new
3366 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3367 that @value{GDBN} should run your program under that name.
3368 Then start your program again.
3371 Relink your program so that the text segment is nonsharable, using the
3372 linker option @samp{-N}. The operating system limitation may not apply
3373 to nonsharable executables.
3377 A similar message can be printed if you request too many active
3378 hardware-assisted breakpoints and watchpoints:
3380 @c FIXME: the precise wording of this message may change; the relevant
3381 @c source change is not committed yet (Sep 3, 1999).
3383 Stopped; cannot insert breakpoints.
3384 You may have requested too many hardware breakpoints and watchpoints.
3388 This message is printed when you attempt to resume the program, since
3389 only then @value{GDBN} knows exactly how many hardware breakpoints and
3390 watchpoints it needs to insert.
3392 When this message is printed, you need to disable or remove some of the
3393 hardware-assisted breakpoints and watchpoints, and then continue.
3395 @node Breakpoint related warnings
3396 @subsection ``Breakpoint address adjusted...''
3397 @cindex breakpoint address adjusted
3399 Some processor architectures place constraints on the addresses at
3400 which breakpoints may be placed. For architectures thus constrained,
3401 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3402 with the constraints dictated by the architecture.
3404 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3405 a VLIW architecture in which a number of RISC-like instructions may be
3406 bundled together for parallel execution. The FR-V architecture
3407 constrains the location of a breakpoint instruction within such a
3408 bundle to the instruction with the lowest address. @value{GDBN}
3409 honors this constraint by adjusting a breakpoint's address to the
3410 first in the bundle.
3412 It is not uncommon for optimized code to have bundles which contain
3413 instructions from different source statements, thus it may happen that
3414 a breakpoint's address will be adjusted from one source statement to
3415 another. Since this adjustment may significantly alter @value{GDBN}'s
3416 breakpoint related behavior from what the user expects, a warning is
3417 printed when the breakpoint is first set and also when the breakpoint
3420 A warning like the one below is printed when setting a breakpoint
3421 that's been subject to address adjustment:
3424 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3427 Such warnings are printed both for user settable and @value{GDBN}'s
3428 internal breakpoints. If you see one of these warnings, you should
3429 verify that a breakpoint set at the adjusted address will have the
3430 desired affect. If not, the breakpoint in question may be removed and
3431 other breakpoints may be set which will have the desired behavior.
3432 E.g., it may be sufficient to place the breakpoint at a later
3433 instruction. A conditional breakpoint may also be useful in some
3434 cases to prevent the breakpoint from triggering too often.
3436 @value{GDBN} will also issue a warning when stopping at one of these
3437 adjusted breakpoints:
3440 warning: Breakpoint 1 address previously adjusted from 0x00010414
3444 When this warning is encountered, it may be too late to take remedial
3445 action except in cases where the breakpoint is hit earlier or more
3446 frequently than expected.
3448 @node Continuing and Stepping
3449 @section Continuing and stepping
3453 @cindex resuming execution
3454 @dfn{Continuing} means resuming program execution until your program
3455 completes normally. In contrast, @dfn{stepping} means executing just
3456 one more ``step'' of your program, where ``step'' may mean either one
3457 line of source code, or one machine instruction (depending on what
3458 particular command you use). Either when continuing or when stepping,
3459 your program may stop even sooner, due to a breakpoint or a signal. (If
3460 it stops due to a signal, you may want to use @code{handle}, or use
3461 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3465 @kindex c @r{(@code{continue})}
3466 @kindex fg @r{(resume foreground execution)}
3467 @item continue @r{[}@var{ignore-count}@r{]}
3468 @itemx c @r{[}@var{ignore-count}@r{]}
3469 @itemx fg @r{[}@var{ignore-count}@r{]}
3470 Resume program execution, at the address where your program last stopped;
3471 any breakpoints set at that address are bypassed. The optional argument
3472 @var{ignore-count} allows you to specify a further number of times to
3473 ignore a breakpoint at this location; its effect is like that of
3474 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3476 The argument @var{ignore-count} is meaningful only when your program
3477 stopped due to a breakpoint. At other times, the argument to
3478 @code{continue} is ignored.
3480 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3481 debugged program is deemed to be the foreground program) are provided
3482 purely for convenience, and have exactly the same behavior as
3486 To resume execution at a different place, you can use @code{return}
3487 (@pxref{Returning, ,Returning from a function}) to go back to the
3488 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3489 different address}) to go to an arbitrary location in your program.
3491 A typical technique for using stepping is to set a breakpoint
3492 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3493 beginning of the function or the section of your program where a problem
3494 is believed to lie, run your program until it stops at that breakpoint,
3495 and then step through the suspect area, examining the variables that are
3496 interesting, until you see the problem happen.
3500 @kindex s @r{(@code{step})}
3502 Continue running your program until control reaches a different source
3503 line, then stop it and return control to @value{GDBN}. This command is
3504 abbreviated @code{s}.
3507 @c "without debugging information" is imprecise; actually "without line
3508 @c numbers in the debugging information". (gcc -g1 has debugging info but
3509 @c not line numbers). But it seems complex to try to make that
3510 @c distinction here.
3511 @emph{Warning:} If you use the @code{step} command while control is
3512 within a function that was compiled without debugging information,
3513 execution proceeds until control reaches a function that does have
3514 debugging information. Likewise, it will not step into a function which
3515 is compiled without debugging information. To step through functions
3516 without debugging information, use the @code{stepi} command, described
3520 The @code{step} command only stops at the first instruction of a source
3521 line. This prevents the multiple stops that could otherwise occur in
3522 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3523 to stop if a function that has debugging information is called within
3524 the line. In other words, @code{step} @emph{steps inside} any functions
3525 called within the line.
3527 Also, the @code{step} command only enters a function if there is line
3528 number information for the function. Otherwise it acts like the
3529 @code{next} command. This avoids problems when using @code{cc -gl}
3530 on MIPS machines. Previously, @code{step} entered subroutines if there
3531 was any debugging information about the routine.
3533 @item step @var{count}
3534 Continue running as in @code{step}, but do so @var{count} times. If a
3535 breakpoint is reached, or a signal not related to stepping occurs before
3536 @var{count} steps, stepping stops right away.
3539 @kindex n @r{(@code{next})}
3540 @item next @r{[}@var{count}@r{]}
3541 Continue to the next source line in the current (innermost) stack frame.
3542 This is similar to @code{step}, but function calls that appear within
3543 the line of code are executed without stopping. Execution stops when
3544 control reaches a different line of code at the original stack level
3545 that was executing when you gave the @code{next} command. This command
3546 is abbreviated @code{n}.
3548 An argument @var{count} is a repeat count, as for @code{step}.
3551 @c FIX ME!! Do we delete this, or is there a way it fits in with
3552 @c the following paragraph? --- Vctoria
3554 @c @code{next} within a function that lacks debugging information acts like
3555 @c @code{step}, but any function calls appearing within the code of the
3556 @c function are executed without stopping.
3558 The @code{next} command only stops at the first instruction of a
3559 source line. This prevents multiple stops that could otherwise occur in
3560 @code{switch} statements, @code{for} loops, etc.
3562 @kindex set step-mode
3564 @cindex functions without line info, and stepping
3565 @cindex stepping into functions with no line info
3566 @itemx set step-mode on
3567 The @code{set step-mode on} command causes the @code{step} command to
3568 stop at the first instruction of a function which contains no debug line
3569 information rather than stepping over it.
3571 This is useful in cases where you may be interested in inspecting the
3572 machine instructions of a function which has no symbolic info and do not
3573 want @value{GDBN} to automatically skip over this function.
3575 @item set step-mode off
3576 Causes the @code{step} command to step over any functions which contains no
3577 debug information. This is the default.
3581 Continue running until just after function in the selected stack frame
3582 returns. Print the returned value (if any).
3584 Contrast this with the @code{return} command (@pxref{Returning,
3585 ,Returning from a function}).
3588 @kindex u @r{(@code{until})}
3591 Continue running until a source line past the current line, in the
3592 current stack frame, is reached. This command is used to avoid single
3593 stepping through a loop more than once. It is like the @code{next}
3594 command, except that when @code{until} encounters a jump, it
3595 automatically continues execution until the program counter is greater
3596 than the address of the jump.
3598 This means that when you reach the end of a loop after single stepping
3599 though it, @code{until} makes your program continue execution until it
3600 exits the loop. In contrast, a @code{next} command at the end of a loop
3601 simply steps back to the beginning of the loop, which forces you to step
3602 through the next iteration.
3604 @code{until} always stops your program if it attempts to exit the current
3607 @code{until} may produce somewhat counterintuitive results if the order
3608 of machine code does not match the order of the source lines. For
3609 example, in the following excerpt from a debugging session, the @code{f}
3610 (@code{frame}) command shows that execution is stopped at line
3611 @code{206}; yet when we use @code{until}, we get to line @code{195}:
3615 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
3617 (@value{GDBP}) until
3618 195 for ( ; argc > 0; NEXTARG) @{
3621 This happened because, for execution efficiency, the compiler had
3622 generated code for the loop closure test at the end, rather than the
3623 start, of the loop---even though the test in a C @code{for}-loop is
3624 written before the body of the loop. The @code{until} command appeared
3625 to step back to the beginning of the loop when it advanced to this
3626 expression; however, it has not really gone to an earlier
3627 statement---not in terms of the actual machine code.
3629 @code{until} with no argument works by means of single
3630 instruction stepping, and hence is slower than @code{until} with an
3633 @item until @var{location}
3634 @itemx u @var{location}
3635 Continue running your program until either the specified location is
3636 reached, or the current stack frame returns. @var{location} is any of
3637 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
3638 ,Setting breakpoints}). This form of the command uses breakpoints, and
3639 hence is quicker than @code{until} without an argument. The specified
3640 location is actually reached only if it is in the current frame. This
3641 implies that @code{until} can be used to skip over recursive function
3642 invocations. For instance in the code below, if the current location is
3643 line @code{96}, issuing @code{until 99} will execute the program up to
3644 line @code{99} in the same invocation of factorial, i.e. after the inner
3645 invocations have returned.
3648 94 int factorial (int value)
3650 96 if (value > 1) @{
3651 97 value *= factorial (value - 1);
3658 @kindex advance @var{location}
3659 @itemx advance @var{location}
3660 Continue running the program up to the given location. An argument is
3661 required, anything of the same form as arguments for the @code{break}
3662 command. Execution will also stop upon exit from the current stack
3663 frame. This command is similar to @code{until}, but @code{advance} will
3664 not skip over recursive function calls, and the target location doesn't
3665 have to be in the same frame as the current one.
3669 @kindex si @r{(@code{stepi})}
3671 @itemx stepi @var{arg}
3673 Execute one machine instruction, then stop and return to the debugger.
3675 It is often useful to do @samp{display/i $pc} when stepping by machine
3676 instructions. This makes @value{GDBN} automatically display the next
3677 instruction to be executed, each time your program stops. @xref{Auto
3678 Display,, Automatic display}.
3680 An argument is a repeat count, as in @code{step}.
3684 @kindex ni @r{(@code{nexti})}
3686 @itemx nexti @var{arg}
3688 Execute one machine instruction, but if it is a function call,
3689 proceed until the function returns.
3691 An argument is a repeat count, as in @code{next}.
3698 A signal is an asynchronous event that can happen in a program. The
3699 operating system defines the possible kinds of signals, and gives each
3700 kind a name and a number. For example, in Unix @code{SIGINT} is the
3701 signal a program gets when you type an interrupt character (often @kbd{C-c});
3702 @code{SIGSEGV} is the signal a program gets from referencing a place in
3703 memory far away from all the areas in use; @code{SIGALRM} occurs when
3704 the alarm clock timer goes off (which happens only if your program has
3705 requested an alarm).
3707 @cindex fatal signals
3708 Some signals, including @code{SIGALRM}, are a normal part of the
3709 functioning of your program. Others, such as @code{SIGSEGV}, indicate
3710 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
3711 program has not specified in advance some other way to handle the signal.
3712 @code{SIGINT} does not indicate an error in your program, but it is normally
3713 fatal so it can carry out the purpose of the interrupt: to kill the program.
3715 @value{GDBN} has the ability to detect any occurrence of a signal in your
3716 program. You can tell @value{GDBN} in advance what to do for each kind of
3719 @cindex handling signals
3720 Normally, @value{GDBN} is set up to let the non-erroneous signals like
3721 @code{SIGALRM} be silently passed to your program
3722 (so as not to interfere with their role in the program's functioning)
3723 but to stop your program immediately whenever an error signal happens.
3724 You can change these settings with the @code{handle} command.
3727 @kindex info signals
3730 Print a table of all the kinds of signals and how @value{GDBN} has been told to
3731 handle each one. You can use this to see the signal numbers of all
3732 the defined types of signals.
3734 @code{info handle} is an alias for @code{info signals}.
3737 @item handle @var{signal} @var{keywords}@dots{}
3738 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
3739 can be the number of a signal or its name (with or without the
3740 @samp{SIG} at the beginning); a list of signal numbers of the form
3741 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
3742 known signals. The @var{keywords} say what change to make.
3746 The keywords allowed by the @code{handle} command can be abbreviated.
3747 Their full names are:
3751 @value{GDBN} should not stop your program when this signal happens. It may
3752 still print a message telling you that the signal has come in.
3755 @value{GDBN} should stop your program when this signal happens. This implies
3756 the @code{print} keyword as well.
3759 @value{GDBN} should print a message when this signal happens.
3762 @value{GDBN} should not mention the occurrence of the signal at all. This
3763 implies the @code{nostop} keyword as well.
3767 @value{GDBN} should allow your program to see this signal; your program
3768 can handle the signal, or else it may terminate if the signal is fatal
3769 and not handled. @code{pass} and @code{noignore} are synonyms.
3773 @value{GDBN} should not allow your program to see this signal.
3774 @code{nopass} and @code{ignore} are synonyms.
3778 When a signal stops your program, the signal is not visible to the
3780 continue. Your program sees the signal then, if @code{pass} is in
3781 effect for the signal in question @emph{at that time}. In other words,
3782 after @value{GDBN} reports a signal, you can use the @code{handle}
3783 command with @code{pass} or @code{nopass} to control whether your
3784 program sees that signal when you continue.
3786 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
3787 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
3788 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
3791 You can also use the @code{signal} command to prevent your program from
3792 seeing a signal, or cause it to see a signal it normally would not see,
3793 or to give it any signal at any time. For example, if your program stopped
3794 due to some sort of memory reference error, you might store correct
3795 values into the erroneous variables and continue, hoping to see more
3796 execution; but your program would probably terminate immediately as
3797 a result of the fatal signal once it saw the signal. To prevent this,
3798 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
3802 @section Stopping and starting multi-thread programs
3804 When your program has multiple threads (@pxref{Threads,, Debugging
3805 programs with multiple threads}), you can choose whether to set
3806 breakpoints on all threads, or on a particular thread.
3809 @cindex breakpoints and threads
3810 @cindex thread breakpoints
3811 @kindex break @dots{} thread @var{threadno}
3812 @item break @var{linespec} thread @var{threadno}
3813 @itemx break @var{linespec} thread @var{threadno} if @dots{}
3814 @var{linespec} specifies source lines; there are several ways of
3815 writing them, but the effect is always to specify some source line.
3817 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
3818 to specify that you only want @value{GDBN} to stop the program when a
3819 particular thread reaches this breakpoint. @var{threadno} is one of the
3820 numeric thread identifiers assigned by @value{GDBN}, shown in the first
3821 column of the @samp{info threads} display.
3823 If you do not specify @samp{thread @var{threadno}} when you set a
3824 breakpoint, the breakpoint applies to @emph{all} threads of your
3827 You can use the @code{thread} qualifier on conditional breakpoints as
3828 well; in this case, place @samp{thread @var{threadno}} before the
3829 breakpoint condition, like this:
3832 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
3837 @cindex stopped threads
3838 @cindex threads, stopped
3839 Whenever your program stops under @value{GDBN} for any reason,
3840 @emph{all} threads of execution stop, not just the current thread. This
3841 allows you to examine the overall state of the program, including
3842 switching between threads, without worrying that things may change
3845 @cindex thread breakpoints and system calls
3846 @cindex system calls and thread breakpoints
3847 @cindex premature return from system calls
3848 There is an unfortunate side effect. If one thread stops for a
3849 breakpoint, or for some other reason, and another thread is blocked in a
3850 system call, then the system call may return prematurely. This is a
3851 consequence of the interaction between multiple threads and the signals
3852 that @value{GDBN} uses to implement breakpoints and other events that
3855 To handle this problem, your program should check the return value of
3856 each system call and react appropriately. This is good programming
3859 For example, do not write code like this:
3865 The call to @code{sleep} will return early if a different thread stops
3866 at a breakpoint or for some other reason.
3868 Instead, write this:
3873 unslept = sleep (unslept);
3876 A system call is allowed to return early, so the system is still
3877 conforming to its specification. But @value{GDBN} does cause your
3878 multi-threaded program to behave differently than it would without
3881 Also, @value{GDBN} uses internal breakpoints in the thread library to
3882 monitor certain events such as thread creation and thread destruction.
3883 When such an event happens, a system call in another thread may return
3884 prematurely, even though your program does not appear to stop.
3886 @cindex continuing threads
3887 @cindex threads, continuing
3888 Conversely, whenever you restart the program, @emph{all} threads start
3889 executing. @emph{This is true even when single-stepping} with commands
3890 like @code{step} or @code{next}.
3892 In particular, @value{GDBN} cannot single-step all threads in lockstep.
3893 Since thread scheduling is up to your debugging target's operating
3894 system (not controlled by @value{GDBN}), other threads may
3895 execute more than one statement while the current thread completes a
3896 single step. Moreover, in general other threads stop in the middle of a
3897 statement, rather than at a clean statement boundary, when the program
3900 You might even find your program stopped in another thread after
3901 continuing or even single-stepping. This happens whenever some other
3902 thread runs into a breakpoint, a signal, or an exception before the
3903 first thread completes whatever you requested.
3905 On some OSes, you can lock the OS scheduler and thus allow only a single
3909 @item set scheduler-locking @var{mode}
3910 Set the scheduler locking mode. If it is @code{off}, then there is no
3911 locking and any thread may run at any time. If @code{on}, then only the
3912 current thread may run when the inferior is resumed. The @code{step}
3913 mode optimizes for single-stepping. It stops other threads from
3914 ``seizing the prompt'' by preempting the current thread while you are
3915 stepping. Other threads will only rarely (or never) get a chance to run
3916 when you step. They are more likely to run when you @samp{next} over a
3917 function call, and they are completely free to run when you use commands
3918 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
3919 thread hits a breakpoint during its timeslice, they will never steal the
3920 @value{GDBN} prompt away from the thread that you are debugging.
3922 @item show scheduler-locking
3923 Display the current scheduler locking mode.
3928 @chapter Examining the Stack
3930 When your program has stopped, the first thing you need to know is where it
3931 stopped and how it got there.
3934 Each time your program performs a function call, information about the call
3936 That information includes the location of the call in your program,
3937 the arguments of the call,
3938 and the local variables of the function being called.
3939 The information is saved in a block of data called a @dfn{stack frame}.
3940 The stack frames are allocated in a region of memory called the @dfn{call
3943 When your program stops, the @value{GDBN} commands for examining the
3944 stack allow you to see all of this information.
3946 @cindex selected frame
3947 One of the stack frames is @dfn{selected} by @value{GDBN} and many
3948 @value{GDBN} commands refer implicitly to the selected frame. In
3949 particular, whenever you ask @value{GDBN} for the value of a variable in
3950 your program, the value is found in the selected frame. There are
3951 special @value{GDBN} commands to select whichever frame you are
3952 interested in. @xref{Selection, ,Selecting a frame}.
3954 When your program stops, @value{GDBN} automatically selects the
3955 currently executing frame and describes it briefly, similar to the
3956 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
3959 * Frames:: Stack frames
3960 * Backtrace:: Backtraces
3961 * Selection:: Selecting a frame
3962 * Frame Info:: Information on a frame
3967 @section Stack frames
3969 @cindex frame, definition
3971 The call stack is divided up into contiguous pieces called @dfn{stack
3972 frames}, or @dfn{frames} for short; each frame is the data associated
3973 with one call to one function. The frame contains the arguments given
3974 to the function, the function's local variables, and the address at
3975 which the function is executing.
3977 @cindex initial frame
3978 @cindex outermost frame
3979 @cindex innermost frame
3980 When your program is started, the stack has only one frame, that of the
3981 function @code{main}. This is called the @dfn{initial} frame or the
3982 @dfn{outermost} frame. Each time a function is called, a new frame is
3983 made. Each time a function returns, the frame for that function invocation
3984 is eliminated. If a function is recursive, there can be many frames for
3985 the same function. The frame for the function in which execution is
3986 actually occurring is called the @dfn{innermost} frame. This is the most
3987 recently created of all the stack frames that still exist.
3989 @cindex frame pointer
3990 Inside your program, stack frames are identified by their addresses. A
3991 stack frame consists of many bytes, each of which has its own address; each
3992 kind of computer has a convention for choosing one byte whose
3993 address serves as the address of the frame. Usually this address is kept
3994 in a register called the @dfn{frame pointer register} while execution is
3995 going on in that frame.
3997 @cindex frame number
3998 @value{GDBN} assigns numbers to all existing stack frames, starting with
3999 zero for the innermost frame, one for the frame that called it,
4000 and so on upward. These numbers do not really exist in your program;
4001 they are assigned by @value{GDBN} to give you a way of designating stack
4002 frames in @value{GDBN} commands.
4004 @c The -fomit-frame-pointer below perennially causes hbox overflow
4005 @c underflow problems.
4006 @cindex frameless execution
4007 Some compilers provide a way to compile functions so that they operate
4008 without stack frames. (For example, the @value{GCC} option
4010 @samp{-fomit-frame-pointer}
4012 generates functions without a frame.)
4013 This is occasionally done with heavily used library functions to save
4014 the frame setup time. @value{GDBN} has limited facilities for dealing
4015 with these function invocations. If the innermost function invocation
4016 has no stack frame, @value{GDBN} nevertheless regards it as though
4017 it had a separate frame, which is numbered zero as usual, allowing
4018 correct tracing of the function call chain. However, @value{GDBN} has
4019 no provision for frameless functions elsewhere in the stack.
4022 @kindex frame@r{, command}
4023 @cindex current stack frame
4024 @item frame @var{args}
4025 The @code{frame} command allows you to move from one stack frame to another,
4026 and to print the stack frame you select. @var{args} may be either the
4027 address of the frame or the stack frame number. Without an argument,
4028 @code{frame} prints the current stack frame.
4030 @kindex select-frame
4031 @cindex selecting frame silently
4033 The @code{select-frame} command allows you to move from one stack frame
4034 to another without printing the frame. This is the silent version of
4043 @cindex stack traces
4044 A backtrace is a summary of how your program got where it is. It shows one
4045 line per frame, for many frames, starting with the currently executing
4046 frame (frame zero), followed by its caller (frame one), and on up the
4051 @kindex bt @r{(@code{backtrace})}
4054 Print a backtrace of the entire stack: one line per frame for all
4055 frames in the stack.
4057 You can stop the backtrace at any time by typing the system interrupt
4058 character, normally @kbd{C-c}.
4060 @item backtrace @var{n}
4062 Similar, but print only the innermost @var{n} frames.
4064 @item backtrace -@var{n}
4066 Similar, but print only the outermost @var{n} frames.
4071 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4072 are additional aliases for @code{backtrace}.
4074 Each line in the backtrace shows the frame number and the function name.
4075 The program counter value is also shown---unless you use @code{set
4076 print address off}. The backtrace also shows the source file name and
4077 line number, as well as the arguments to the function. The program
4078 counter value is omitted if it is at the beginning of the code for that
4081 Here is an example of a backtrace. It was made with the command
4082 @samp{bt 3}, so it shows the innermost three frames.
4086 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4088 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4089 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4091 (More stack frames follow...)
4096 The display for frame zero does not begin with a program counter
4097 value, indicating that your program has stopped at the beginning of the
4098 code for line @code{993} of @code{builtin.c}.
4100 Most programs have a standard user entry point---a place where system
4101 libraries and startup code transition into user code. For C this is
4102 @code{main}. When @value{GDBN} finds the entry function in a backtrace
4103 it will terminate the backtrace, to avoid tracing into highly
4104 system-specific (and generally uninteresting) code.
4106 If you need to examine the startup code, or limit the number of levels
4107 in a backtrace, you can change this behavior:
4110 @item set backtrace past-main
4111 @itemx set backtrace past-main on
4112 @kindex set backtrace
4113 Backtraces will continue past the user entry point.
4115 @item set backtrace past-main off
4116 Backtraces will stop when they encounter the user entry point. This is the
4119 @item show backtrace past-main
4120 @kindex show backtrace
4121 Display the current user entry point backtrace policy.
4123 @item set backtrace limit @var{n}
4124 @itemx set backtrace limit 0
4125 @cindex backtrace limit
4126 Limit the backtrace to @var{n} levels. A value of zero means
4129 @item show backtrace limit
4130 Display the current limit on backtrace levels.
4134 @section Selecting a frame
4136 Most commands for examining the stack and other data in your program work on
4137 whichever stack frame is selected at the moment. Here are the commands for
4138 selecting a stack frame; all of them finish by printing a brief description
4139 of the stack frame just selected.
4142 @kindex frame@r{, selecting}
4143 @kindex f @r{(@code{frame})}
4146 Select frame number @var{n}. Recall that frame zero is the innermost
4147 (currently executing) frame, frame one is the frame that called the
4148 innermost one, and so on. The highest-numbered frame is the one for
4151 @item frame @var{addr}
4153 Select the frame at address @var{addr}. This is useful mainly if the
4154 chaining of stack frames has been damaged by a bug, making it
4155 impossible for @value{GDBN} to assign numbers properly to all frames. In
4156 addition, this can be useful when your program has multiple stacks and
4157 switches between them.
4159 On the SPARC architecture, @code{frame} needs two addresses to
4160 select an arbitrary frame: a frame pointer and a stack pointer.
4162 On the MIPS and Alpha architecture, it needs two addresses: a stack
4163 pointer and a program counter.
4165 On the 29k architecture, it needs three addresses: a register stack
4166 pointer, a program counter, and a memory stack pointer.
4167 @c note to future updaters: this is conditioned on a flag
4168 @c SETUP_ARBITRARY_FRAME in the tm-*.h files. The above is up to date
4169 @c as of 27 Jan 1994.
4173 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4174 advances toward the outermost frame, to higher frame numbers, to frames
4175 that have existed longer. @var{n} defaults to one.
4178 @kindex do @r{(@code{down})}
4180 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4181 advances toward the innermost frame, to lower frame numbers, to frames
4182 that were created more recently. @var{n} defaults to one. You may
4183 abbreviate @code{down} as @code{do}.
4186 All of these commands end by printing two lines of output describing the
4187 frame. The first line shows the frame number, the function name, the
4188 arguments, and the source file and line number of execution in that
4189 frame. The second line shows the text of that source line.
4197 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4199 10 read_input_file (argv[i]);
4203 After such a printout, the @code{list} command with no arguments
4204 prints ten lines centered on the point of execution in the frame.
4205 You can also edit the program at the point of execution with your favorite
4206 editing program by typing @code{edit}.
4207 @xref{List, ,Printing source lines},
4211 @kindex down-silently
4213 @item up-silently @var{n}
4214 @itemx down-silently @var{n}
4215 These two commands are variants of @code{up} and @code{down},
4216 respectively; they differ in that they do their work silently, without
4217 causing display of the new frame. They are intended primarily for use
4218 in @value{GDBN} command scripts, where the output might be unnecessary and
4223 @section Information about a frame
4225 There are several other commands to print information about the selected
4231 When used without any argument, this command does not change which
4232 frame is selected, but prints a brief description of the currently
4233 selected stack frame. It can be abbreviated @code{f}. With an
4234 argument, this command is used to select a stack frame.
4235 @xref{Selection, ,Selecting a frame}.
4238 @kindex info f @r{(@code{info frame})}
4241 This command prints a verbose description of the selected stack frame,
4246 the address of the frame
4248 the address of the next frame down (called by this frame)
4250 the address of the next frame up (caller of this frame)
4252 the language in which the source code corresponding to this frame is written
4254 the address of the frame's arguments
4256 the address of the frame's local variables
4258 the program counter saved in it (the address of execution in the caller frame)
4260 which registers were saved in the frame
4263 @noindent The verbose description is useful when
4264 something has gone wrong that has made the stack format fail to fit
4265 the usual conventions.
4267 @item info frame @var{addr}
4268 @itemx info f @var{addr}
4269 Print a verbose description of the frame at address @var{addr}, without
4270 selecting that frame. The selected frame remains unchanged by this
4271 command. This requires the same kind of address (more than one for some
4272 architectures) that you specify in the @code{frame} command.
4273 @xref{Selection, ,Selecting a frame}.
4277 Print the arguments of the selected frame, each on a separate line.
4281 Print the local variables of the selected frame, each on a separate
4282 line. These are all variables (declared either static or automatic)
4283 accessible at the point of execution of the selected frame.
4286 @cindex catch exceptions, list active handlers
4287 @cindex exception handlers, how to list
4289 Print a list of all the exception handlers that are active in the
4290 current stack frame at the current point of execution. To see other
4291 exception handlers, visit the associated frame (using the @code{up},
4292 @code{down}, or @code{frame} commands); then type @code{info catch}.
4293 @xref{Set Catchpoints, , Setting catchpoints}.
4299 @chapter Examining Source Files
4301 @value{GDBN} can print parts of your program's source, since the debugging
4302 information recorded in the program tells @value{GDBN} what source files were
4303 used to build it. When your program stops, @value{GDBN} spontaneously prints
4304 the line where it stopped. Likewise, when you select a stack frame
4305 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4306 execution in that frame has stopped. You can print other portions of
4307 source files by explicit command.
4309 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4310 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4311 @value{GDBN} under @sc{gnu} Emacs}.
4314 * List:: Printing source lines
4315 * Edit:: Editing source files
4316 * Search:: Searching source files
4317 * Source Path:: Specifying source directories
4318 * Machine Code:: Source and machine code
4322 @section Printing source lines
4325 @kindex l @r{(@code{list})}
4326 To print lines from a source file, use the @code{list} command
4327 (abbreviated @code{l}). By default, ten lines are printed.
4328 There are several ways to specify what part of the file you want to print.
4330 Here are the forms of the @code{list} command most commonly used:
4333 @item list @var{linenum}
4334 Print lines centered around line number @var{linenum} in the
4335 current source file.
4337 @item list @var{function}
4338 Print lines centered around the beginning of function
4342 Print more lines. If the last lines printed were printed with a
4343 @code{list} command, this prints lines following the last lines
4344 printed; however, if the last line printed was a solitary line printed
4345 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4346 Stack}), this prints lines centered around that line.
4349 Print lines just before the lines last printed.
4352 By default, @value{GDBN} prints ten source lines with any of these forms of
4353 the @code{list} command. You can change this using @code{set listsize}:
4356 @kindex set listsize
4357 @item set listsize @var{count}
4358 Make the @code{list} command display @var{count} source lines (unless
4359 the @code{list} argument explicitly specifies some other number).
4361 @kindex show listsize
4363 Display the number of lines that @code{list} prints.
4366 Repeating a @code{list} command with @key{RET} discards the argument,
4367 so it is equivalent to typing just @code{list}. This is more useful
4368 than listing the same lines again. An exception is made for an
4369 argument of @samp{-}; that argument is preserved in repetition so that
4370 each repetition moves up in the source file.
4373 In general, the @code{list} command expects you to supply zero, one or two
4374 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4375 of writing them, but the effect is always to specify some source line.
4376 Here is a complete description of the possible arguments for @code{list}:
4379 @item list @var{linespec}
4380 Print lines centered around the line specified by @var{linespec}.
4382 @item list @var{first},@var{last}
4383 Print lines from @var{first} to @var{last}. Both arguments are
4386 @item list ,@var{last}
4387 Print lines ending with @var{last}.
4389 @item list @var{first},
4390 Print lines starting with @var{first}.
4393 Print lines just after the lines last printed.
4396 Print lines just before the lines last printed.
4399 As described in the preceding table.
4402 Here are the ways of specifying a single source line---all the
4407 Specifies line @var{number} of the current source file.
4408 When a @code{list} command has two linespecs, this refers to
4409 the same source file as the first linespec.
4412 Specifies the line @var{offset} lines after the last line printed.
4413 When used as the second linespec in a @code{list} command that has
4414 two, this specifies the line @var{offset} lines down from the
4418 Specifies the line @var{offset} lines before the last line printed.
4420 @item @var{filename}:@var{number}
4421 Specifies line @var{number} in the source file @var{filename}.
4423 @item @var{function}
4424 Specifies the line that begins the body of the function @var{function}.
4425 For example: in C, this is the line with the open brace.
4427 @item @var{filename}:@var{function}
4428 Specifies the line of the open-brace that begins the body of the
4429 function @var{function} in the file @var{filename}. You only need the
4430 file name with a function name to avoid ambiguity when there are
4431 identically named functions in different source files.
4433 @item *@var{address}
4434 Specifies the line containing the program address @var{address}.
4435 @var{address} may be any expression.
4439 @section Editing source files
4440 @cindex editing source files
4443 @kindex e @r{(@code{edit})}
4444 To edit the lines in a source file, use the @code{edit} command.
4445 The editing program of your choice
4446 is invoked with the current line set to
4447 the active line in the program.
4448 Alternatively, there are several ways to specify what part of the file you
4449 want to print if you want to see other parts of the program.
4451 Here are the forms of the @code{edit} command most commonly used:
4455 Edit the current source file at the active line number in the program.
4457 @item edit @var{number}
4458 Edit the current source file with @var{number} as the active line number.
4460 @item edit @var{function}
4461 Edit the file containing @var{function} at the beginning of its definition.
4463 @item edit @var{filename}:@var{number}
4464 Specifies line @var{number} in the source file @var{filename}.
4466 @item edit @var{filename}:@var{function}
4467 Specifies the line that begins the body of the
4468 function @var{function} in the file @var{filename}. You only need the
4469 file name with a function name to avoid ambiguity when there are
4470 identically named functions in different source files.
4472 @item edit *@var{address}
4473 Specifies the line containing the program address @var{address}.
4474 @var{address} may be any expression.
4477 @subsection Choosing your editor
4478 You can customize @value{GDBN} to use any editor you want
4480 The only restriction is that your editor (say @code{ex}), recognizes the
4481 following command-line syntax:
4483 ex +@var{number} file
4485 The optional numeric value +@var{number} specifies the number of the line in
4486 the file where to start editing.}.
4487 By default, it is @file{@value{EDITOR}}, but you can change this
4488 by setting the environment variable @code{EDITOR} before using
4489 @value{GDBN}. For example, to configure @value{GDBN} to use the
4490 @code{vi} editor, you could use these commands with the @code{sh} shell:
4496 or in the @code{csh} shell,
4498 setenv EDITOR /usr/bin/vi
4503 @section Searching source files
4504 @cindex searching source files
4505 @kindex reverse-search
4507 There are two commands for searching through the current source file for a
4512 @kindex forward-search
4513 @item forward-search @var{regexp}
4514 @itemx search @var{regexp}
4515 The command @samp{forward-search @var{regexp}} checks each line,
4516 starting with the one following the last line listed, for a match for
4517 @var{regexp}. It lists the line that is found. You can use the
4518 synonym @samp{search @var{regexp}} or abbreviate the command name as
4521 @item reverse-search @var{regexp}
4522 The command @samp{reverse-search @var{regexp}} checks each line, starting
4523 with the one before the last line listed and going backward, for a match
4524 for @var{regexp}. It lists the line that is found. You can abbreviate
4525 this command as @code{rev}.
4529 @section Specifying source directories
4532 @cindex directories for source files
4533 Executable programs sometimes do not record the directories of the source
4534 files from which they were compiled, just the names. Even when they do,
4535 the directories could be moved between the compilation and your debugging
4536 session. @value{GDBN} has a list of directories to search for source files;
4537 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
4538 it tries all the directories in the list, in the order they are present
4539 in the list, until it finds a file with the desired name.
4541 For example, suppose an executable references the file
4542 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
4543 @file{/mnt/cross}. The file is first looked up literally; if this
4544 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
4545 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
4546 message is printed. @value{GDBN} does not look up the parts of the
4547 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
4548 Likewise, the subdirectories of the source path are not searched: if
4549 the source path is @file{/mnt/cross}, and the binary refers to
4550 @file{foo.c}, @value{GDBN} would not find it under
4551 @file{/mnt/cross/usr/src/foo-1.0/lib}.
4553 Plain file names, relative file names with leading directories, file
4554 names containing dots, etc.@: are all treated as described above; for
4555 instance, if the source path is @file{/mnt/cross}, and the source file
4556 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
4557 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
4558 that---@file{/mnt/cross/foo.c}.
4560 Note that the executable search path is @emph{not} used to locate the
4561 source files. Neither is the current working directory, unless it
4562 happens to be in the source path.
4564 Whenever you reset or rearrange the source path, @value{GDBN} clears out
4565 any information it has cached about where source files are found and where
4566 each line is in the file.
4570 When you start @value{GDBN}, its source path includes only @samp{cdir}
4571 and @samp{cwd}, in that order.
4572 To add other directories, use the @code{directory} command.
4575 @item directory @var{dirname} @dots{}
4576 @item dir @var{dirname} @dots{}
4577 Add directory @var{dirname} to the front of the source path. Several
4578 directory names may be given to this command, separated by @samp{:}
4579 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
4580 part of absolute file names) or
4581 whitespace. You may specify a directory that is already in the source
4582 path; this moves it forward, so @value{GDBN} searches it sooner.
4586 @vindex $cdir@r{, convenience variable}
4587 @vindex $cwdr@r{, convenience variable}
4588 @cindex compilation directory
4589 @cindex current directory
4590 @cindex working directory
4591 @cindex directory, current
4592 @cindex directory, compilation
4593 You can use the string @samp{$cdir} to refer to the compilation
4594 directory (if one is recorded), and @samp{$cwd} to refer to the current
4595 working directory. @samp{$cwd} is not the same as @samp{.}---the former
4596 tracks the current working directory as it changes during your @value{GDBN}
4597 session, while the latter is immediately expanded to the current
4598 directory at the time you add an entry to the source path.
4601 Reset the source path to empty again. This requires confirmation.
4603 @c RET-repeat for @code{directory} is explicitly disabled, but since
4604 @c repeating it would be a no-op we do not say that. (thanks to RMS)
4606 @item show directories
4607 @kindex show directories
4608 Print the source path: show which directories it contains.
4611 If your source path is cluttered with directories that are no longer of
4612 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
4613 versions of source. You can correct the situation as follows:
4617 Use @code{directory} with no argument to reset the source path to empty.
4620 Use @code{directory} with suitable arguments to reinstall the
4621 directories you want in the source path. You can add all the
4622 directories in one command.
4626 @section Source and machine code
4627 @cindex source line and its code address
4629 You can use the command @code{info line} to map source lines to program
4630 addresses (and vice versa), and the command @code{disassemble} to display
4631 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
4632 mode, the @code{info line} command causes the arrow to point to the
4633 line specified. Also, @code{info line} prints addresses in symbolic form as
4638 @item info line @var{linespec}
4639 Print the starting and ending addresses of the compiled code for
4640 source line @var{linespec}. You can specify source lines in any of
4641 the ways understood by the @code{list} command (@pxref{List, ,Printing
4645 For example, we can use @code{info line} to discover the location of
4646 the object code for the first line of function
4647 @code{m4_changequote}:
4649 @c FIXME: I think this example should also show the addresses in
4650 @c symbolic form, as they usually would be displayed.
4652 (@value{GDBP}) info line m4_changequote
4653 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
4657 @cindex code address and its source line
4658 We can also inquire (using @code{*@var{addr}} as the form for
4659 @var{linespec}) what source line covers a particular address:
4661 (@value{GDBP}) info line *0x63ff
4662 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
4665 @cindex @code{$_} and @code{info line}
4666 @cindex @code{x} command, default address
4667 @kindex x@r{(examine), and} info line
4668 After @code{info line}, the default address for the @code{x} command
4669 is changed to the starting address of the line, so that @samp{x/i} is
4670 sufficient to begin examining the machine code (@pxref{Memory,
4671 ,Examining memory}). Also, this address is saved as the value of the
4672 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
4677 @cindex assembly instructions
4678 @cindex instructions, assembly
4679 @cindex machine instructions
4680 @cindex listing machine instructions
4682 This specialized command dumps a range of memory as machine
4683 instructions. The default memory range is the function surrounding the
4684 program counter of the selected frame. A single argument to this
4685 command is a program counter value; @value{GDBN} dumps the function
4686 surrounding this value. Two arguments specify a range of addresses
4687 (first inclusive, second exclusive) to dump.
4690 The following example shows the disassembly of a range of addresses of
4691 HP PA-RISC 2.0 code:
4694 (@value{GDBP}) disas 0x32c4 0x32e4
4695 Dump of assembler code from 0x32c4 to 0x32e4:
4696 0x32c4 <main+204>: addil 0,dp
4697 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
4698 0x32cc <main+212>: ldil 0x3000,r31
4699 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
4700 0x32d4 <main+220>: ldo 0(r31),rp
4701 0x32d8 <main+224>: addil -0x800,dp
4702 0x32dc <main+228>: ldo 0x588(r1),r26
4703 0x32e0 <main+232>: ldil 0x3000,r31
4704 End of assembler dump.
4707 Some architectures have more than one commonly-used set of instruction
4708 mnemonics or other syntax.
4711 @kindex set disassembly-flavor
4712 @cindex Intel disassembly flavor
4713 @cindex AT&T disassembly flavor
4714 @item set disassembly-flavor @var{instruction-set}
4715 Select the instruction set to use when disassembling the
4716 program via the @code{disassemble} or @code{x/i} commands.
4718 Currently this command is only defined for the Intel x86 family. You
4719 can set @var{instruction-set} to either @code{intel} or @code{att}.
4720 The default is @code{att}, the AT&T flavor used by default by Unix
4721 assemblers for x86-based targets.
4726 @chapter Examining Data
4728 @cindex printing data
4729 @cindex examining data
4732 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
4733 @c document because it is nonstandard... Under Epoch it displays in a
4734 @c different window or something like that.
4735 The usual way to examine data in your program is with the @code{print}
4736 command (abbreviated @code{p}), or its synonym @code{inspect}. It
4737 evaluates and prints the value of an expression of the language your
4738 program is written in (@pxref{Languages, ,Using @value{GDBN} with
4739 Different Languages}).
4742 @item print @var{expr}
4743 @itemx print /@var{f} @var{expr}
4744 @var{expr} is an expression (in the source language). By default the
4745 value of @var{expr} is printed in a format appropriate to its data type;
4746 you can choose a different format by specifying @samp{/@var{f}}, where
4747 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
4751 @itemx print /@var{f}
4752 @cindex reprint the last value
4753 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
4754 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
4755 conveniently inspect the same value in an alternative format.
4758 A more low-level way of examining data is with the @code{x} command.
4759 It examines data in memory at a specified address and prints it in a
4760 specified format. @xref{Memory, ,Examining memory}.
4762 If you are interested in information about types, or about how the
4763 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
4764 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
4768 * Expressions:: Expressions
4769 * Variables:: Program variables
4770 * Arrays:: Artificial arrays
4771 * Output Formats:: Output formats
4772 * Memory:: Examining memory
4773 * Auto Display:: Automatic display
4774 * Print Settings:: Print settings
4775 * Value History:: Value history
4776 * Convenience Vars:: Convenience variables
4777 * Registers:: Registers
4778 * Floating Point Hardware:: Floating point hardware
4779 * Vector Unit:: Vector Unit
4780 * Auxiliary Vector:: Auxiliary data provided by operating system
4781 * Memory Region Attributes:: Memory region attributes
4782 * Dump/Restore Files:: Copy between memory and a file
4783 * Core File Generation:: Cause a program dump its core
4784 * Character Sets:: Debugging programs that use a different
4785 character set than GDB does
4789 @section Expressions
4792 @code{print} and many other @value{GDBN} commands accept an expression and
4793 compute its value. Any kind of constant, variable or operator defined
4794 by the programming language you are using is valid in an expression in
4795 @value{GDBN}. This includes conditional expressions, function calls,
4796 casts, and string constants. It also includes preprocessor macros, if
4797 you compiled your program to include this information; see
4800 @cindex arrays in expressions
4801 @value{GDBN} supports array constants in expressions input by
4802 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
4803 you can use the command @code{print @{1, 2, 3@}} to build up an array in
4804 memory that is @code{malloc}ed in the target program.
4806 Because C is so widespread, most of the expressions shown in examples in
4807 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
4808 Languages}, for information on how to use expressions in other
4811 In this section, we discuss operators that you can use in @value{GDBN}
4812 expressions regardless of your programming language.
4814 @cindex casts, in expressions
4815 Casts are supported in all languages, not just in C, because it is so
4816 useful to cast a number into a pointer in order to examine a structure
4817 at that address in memory.
4818 @c FIXME: casts supported---Mod2 true?
4820 @value{GDBN} supports these operators, in addition to those common
4821 to programming languages:
4825 @samp{@@} is a binary operator for treating parts of memory as arrays.
4826 @xref{Arrays, ,Artificial arrays}, for more information.
4829 @samp{::} allows you to specify a variable in terms of the file or
4830 function where it is defined. @xref{Variables, ,Program variables}.
4832 @cindex @{@var{type}@}
4833 @cindex type casting memory
4834 @cindex memory, viewing as typed object
4835 @cindex casts, to view memory
4836 @item @{@var{type}@} @var{addr}
4837 Refers to an object of type @var{type} stored at address @var{addr} in
4838 memory. @var{addr} may be any expression whose value is an integer or
4839 pointer (but parentheses are required around binary operators, just as in
4840 a cast). This construct is allowed regardless of what kind of data is
4841 normally supposed to reside at @var{addr}.
4845 @section Program variables
4847 The most common kind of expression to use is the name of a variable
4850 Variables in expressions are understood in the selected stack frame
4851 (@pxref{Selection, ,Selecting a frame}); they must be either:
4855 global (or file-static)
4862 visible according to the scope rules of the
4863 programming language from the point of execution in that frame
4866 @noindent This means that in the function
4881 you can examine and use the variable @code{a} whenever your program is
4882 executing within the function @code{foo}, but you can only use or
4883 examine the variable @code{b} while your program is executing inside
4884 the block where @code{b} is declared.
4886 @cindex variable name conflict
4887 There is an exception: you can refer to a variable or function whose
4888 scope is a single source file even if the current execution point is not
4889 in this file. But it is possible to have more than one such variable or
4890 function with the same name (in different source files). If that
4891 happens, referring to that name has unpredictable effects. If you wish,
4892 you can specify a static variable in a particular function or file,
4893 using the colon-colon (@code{::}) notation:
4895 @cindex colon-colon, context for variables/functions
4897 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
4898 @cindex @code{::}, context for variables/functions
4901 @var{file}::@var{variable}
4902 @var{function}::@var{variable}
4906 Here @var{file} or @var{function} is the name of the context for the
4907 static @var{variable}. In the case of file names, you can use quotes to
4908 make sure @value{GDBN} parses the file name as a single word---for example,
4909 to print a global value of @code{x} defined in @file{f2.c}:
4912 (@value{GDBP}) p 'f2.c'::x
4915 @cindex C@t{++} scope resolution
4916 This use of @samp{::} is very rarely in conflict with the very similar
4917 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
4918 scope resolution operator in @value{GDBN} expressions.
4919 @c FIXME: Um, so what happens in one of those rare cases where it's in
4922 @cindex wrong values
4923 @cindex variable values, wrong
4924 @cindex function entry/exit, wrong values of variables
4925 @cindex optimized code, wrong values of variables
4927 @emph{Warning:} Occasionally, a local variable may appear to have the
4928 wrong value at certain points in a function---just after entry to a new
4929 scope, and just before exit.
4931 You may see this problem when you are stepping by machine instructions.
4932 This is because, on most machines, it takes more than one instruction to
4933 set up a stack frame (including local variable definitions); if you are
4934 stepping by machine instructions, variables may appear to have the wrong
4935 values until the stack frame is completely built. On exit, it usually
4936 also takes more than one machine instruction to destroy a stack frame;
4937 after you begin stepping through that group of instructions, local
4938 variable definitions may be gone.
4940 This may also happen when the compiler does significant optimizations.
4941 To be sure of always seeing accurate values, turn off all optimization
4944 @cindex ``No symbol "foo" in current context''
4945 Another possible effect of compiler optimizations is to optimize
4946 unused variables out of existence, or assign variables to registers (as
4947 opposed to memory addresses). Depending on the support for such cases
4948 offered by the debug info format used by the compiler, @value{GDBN}
4949 might not be able to display values for such local variables. If that
4950 happens, @value{GDBN} will print a message like this:
4953 No symbol "foo" in current context.
4956 To solve such problems, either recompile without optimizations, or use a
4957 different debug info format, if the compiler supports several such
4958 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
4959 usually supports the @option{-gstabs+} option. @option{-gstabs+}
4960 produces debug info in a format that is superior to formats such as
4961 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
4962 an effective form for debug info. @xref{Debugging Options,,Options
4963 for Debugging Your Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}.
4964 @xref{C, , Debugging C++}, for more info about debug info formats
4965 that are best suited to C@t{++} programs.
4968 @section Artificial arrays
4970 @cindex artificial array
4972 @kindex @@@r{, referencing memory as an array}
4973 It is often useful to print out several successive objects of the
4974 same type in memory; a section of an array, or an array of
4975 dynamically determined size for which only a pointer exists in the
4978 You can do this by referring to a contiguous span of memory as an
4979 @dfn{artificial array}, using the binary operator @samp{@@}. The left
4980 operand of @samp{@@} should be the first element of the desired array
4981 and be an individual object. The right operand should be the desired length
4982 of the array. The result is an array value whose elements are all of
4983 the type of the left argument. The first element is actually the left
4984 argument; the second element comes from bytes of memory immediately
4985 following those that hold the first element, and so on. Here is an
4986 example. If a program says
4989 int *array = (int *) malloc (len * sizeof (int));
4993 you can print the contents of @code{array} with
4999 The left operand of @samp{@@} must reside in memory. Array values made
5000 with @samp{@@} in this way behave just like other arrays in terms of
5001 subscripting, and are coerced to pointers when used in expressions.
5002 Artificial arrays most often appear in expressions via the value history
5003 (@pxref{Value History, ,Value history}), after printing one out.
5005 Another way to create an artificial array is to use a cast.
5006 This re-interprets a value as if it were an array.
5007 The value need not be in memory:
5009 (@value{GDBP}) p/x (short[2])0x12345678
5010 $1 = @{0x1234, 0x5678@}
5013 As a convenience, if you leave the array length out (as in
5014 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5015 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5017 (@value{GDBP}) p/x (short[])0x12345678
5018 $2 = @{0x1234, 0x5678@}
5021 Sometimes the artificial array mechanism is not quite enough; in
5022 moderately complex data structures, the elements of interest may not
5023 actually be adjacent---for example, if you are interested in the values
5024 of pointers in an array. One useful work-around in this situation is
5025 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5026 variables}) as a counter in an expression that prints the first
5027 interesting value, and then repeat that expression via @key{RET}. For
5028 instance, suppose you have an array @code{dtab} of pointers to
5029 structures, and you are interested in the values of a field @code{fv}
5030 in each structure. Here is an example of what you might type:
5040 @node Output Formats
5041 @section Output formats
5043 @cindex formatted output
5044 @cindex output formats
5045 By default, @value{GDBN} prints a value according to its data type. Sometimes
5046 this is not what you want. For example, you might want to print a number
5047 in hex, or a pointer in decimal. Or you might want to view data in memory
5048 at a certain address as a character string or as an instruction. To do
5049 these things, specify an @dfn{output format} when you print a value.
5051 The simplest use of output formats is to say how to print a value
5052 already computed. This is done by starting the arguments of the
5053 @code{print} command with a slash and a format letter. The format
5054 letters supported are:
5058 Regard the bits of the value as an integer, and print the integer in
5062 Print as integer in signed decimal.
5065 Print as integer in unsigned decimal.
5068 Print as integer in octal.
5071 Print as integer in binary. The letter @samp{t} stands for ``two''.
5072 @footnote{@samp{b} cannot be used because these format letters are also
5073 used with the @code{x} command, where @samp{b} stands for ``byte'';
5074 see @ref{Memory,,Examining memory}.}
5077 @cindex unknown address, locating
5078 @cindex locate address
5079 Print as an address, both absolute in hexadecimal and as an offset from
5080 the nearest preceding symbol. You can use this format used to discover
5081 where (in what function) an unknown address is located:
5084 (@value{GDBP}) p/a 0x54320
5085 $3 = 0x54320 <_initialize_vx+396>
5089 The command @code{info symbol 0x54320} yields similar results.
5090 @xref{Symbols, info symbol}.
5093 Regard as an integer and print it as a character constant.
5096 Regard the bits of the value as a floating point number and print
5097 using typical floating point syntax.
5100 For example, to print the program counter in hex (@pxref{Registers}), type
5107 Note that no space is required before the slash; this is because command
5108 names in @value{GDBN} cannot contain a slash.
5110 To reprint the last value in the value history with a different format,
5111 you can use the @code{print} command with just a format and no
5112 expression. For example, @samp{p/x} reprints the last value in hex.
5115 @section Examining memory
5117 You can use the command @code{x} (for ``examine'') to examine memory in
5118 any of several formats, independently of your program's data types.
5120 @cindex examining memory
5122 @kindex x @r{(examine memory)}
5123 @item x/@var{nfu} @var{addr}
5126 Use the @code{x} command to examine memory.
5129 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5130 much memory to display and how to format it; @var{addr} is an
5131 expression giving the address where you want to start displaying memory.
5132 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5133 Several commands set convenient defaults for @var{addr}.
5136 @item @var{n}, the repeat count
5137 The repeat count is a decimal integer; the default is 1. It specifies
5138 how much memory (counting by units @var{u}) to display.
5139 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5142 @item @var{f}, the display format
5143 The display format is one of the formats used by @code{print},
5144 @samp{s} (null-terminated string), or @samp{i} (machine instruction).
5145 The default is @samp{x} (hexadecimal) initially.
5146 The default changes each time you use either @code{x} or @code{print}.
5148 @item @var{u}, the unit size
5149 The unit size is any of
5155 Halfwords (two bytes).
5157 Words (four bytes). This is the initial default.
5159 Giant words (eight bytes).
5162 Each time you specify a unit size with @code{x}, that size becomes the
5163 default unit the next time you use @code{x}. (For the @samp{s} and
5164 @samp{i} formats, the unit size is ignored and is normally not written.)
5166 @item @var{addr}, starting display address
5167 @var{addr} is the address where you want @value{GDBN} to begin displaying
5168 memory. The expression need not have a pointer value (though it may);
5169 it is always interpreted as an integer address of a byte of memory.
5170 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5171 @var{addr} is usually just after the last address examined---but several
5172 other commands also set the default address: @code{info breakpoints} (to
5173 the address of the last breakpoint listed), @code{info line} (to the
5174 starting address of a line), and @code{print} (if you use it to display
5175 a value from memory).
5178 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5179 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5180 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5181 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5182 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5184 Since the letters indicating unit sizes are all distinct from the
5185 letters specifying output formats, you do not have to remember whether
5186 unit size or format comes first; either order works. The output
5187 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5188 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5190 Even though the unit size @var{u} is ignored for the formats @samp{s}
5191 and @samp{i}, you might still want to use a count @var{n}; for example,
5192 @samp{3i} specifies that you want to see three machine instructions,
5193 including any operands. The command @code{disassemble} gives an
5194 alternative way of inspecting machine instructions; see @ref{Machine
5195 Code,,Source and machine code}.
5197 All the defaults for the arguments to @code{x} are designed to make it
5198 easy to continue scanning memory with minimal specifications each time
5199 you use @code{x}. For example, after you have inspected three machine
5200 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5201 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5202 the repeat count @var{n} is used again; the other arguments default as
5203 for successive uses of @code{x}.
5205 @cindex @code{$_}, @code{$__}, and value history
5206 The addresses and contents printed by the @code{x} command are not saved
5207 in the value history because there is often too much of them and they
5208 would get in the way. Instead, @value{GDBN} makes these values available for
5209 subsequent use in expressions as values of the convenience variables
5210 @code{$_} and @code{$__}. After an @code{x} command, the last address
5211 examined is available for use in expressions in the convenience variable
5212 @code{$_}. The contents of that address, as examined, are available in
5213 the convenience variable @code{$__}.
5215 If the @code{x} command has a repeat count, the address and contents saved
5216 are from the last memory unit printed; this is not the same as the last
5217 address printed if several units were printed on the last line of output.
5220 @section Automatic display
5221 @cindex automatic display
5222 @cindex display of expressions
5224 If you find that you want to print the value of an expression frequently
5225 (to see how it changes), you might want to add it to the @dfn{automatic
5226 display list} so that @value{GDBN} prints its value each time your program stops.
5227 Each expression added to the list is given a number to identify it;
5228 to remove an expression from the list, you specify that number.
5229 The automatic display looks like this:
5233 3: bar[5] = (struct hack *) 0x3804
5237 This display shows item numbers, expressions and their current values. As with
5238 displays you request manually using @code{x} or @code{print}, you can
5239 specify the output format you prefer; in fact, @code{display} decides
5240 whether to use @code{print} or @code{x} depending on how elaborate your
5241 format specification is---it uses @code{x} if you specify a unit size,
5242 or one of the two formats (@samp{i} and @samp{s}) that are only
5243 supported by @code{x}; otherwise it uses @code{print}.
5247 @item display @var{expr}
5248 Add the expression @var{expr} to the list of expressions to display
5249 each time your program stops. @xref{Expressions, ,Expressions}.
5251 @code{display} does not repeat if you press @key{RET} again after using it.
5253 @item display/@var{fmt} @var{expr}
5254 For @var{fmt} specifying only a display format and not a size or
5255 count, add the expression @var{expr} to the auto-display list but
5256 arrange to display it each time in the specified format @var{fmt}.
5257 @xref{Output Formats,,Output formats}.
5259 @item display/@var{fmt} @var{addr}
5260 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5261 number of units, add the expression @var{addr} as a memory address to
5262 be examined each time your program stops. Examining means in effect
5263 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5266 For example, @samp{display/i $pc} can be helpful, to see the machine
5267 instruction about to be executed each time execution stops (@samp{$pc}
5268 is a common name for the program counter; @pxref{Registers, ,Registers}).
5271 @kindex delete display
5273 @item undisplay @var{dnums}@dots{}
5274 @itemx delete display @var{dnums}@dots{}
5275 Remove item numbers @var{dnums} from the list of expressions to display.
5277 @code{undisplay} does not repeat if you press @key{RET} after using it.
5278 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5280 @kindex disable display
5281 @item disable display @var{dnums}@dots{}
5282 Disable the display of item numbers @var{dnums}. A disabled display
5283 item is not printed automatically, but is not forgotten. It may be
5284 enabled again later.
5286 @kindex enable display
5287 @item enable display @var{dnums}@dots{}
5288 Enable display of item numbers @var{dnums}. It becomes effective once
5289 again in auto display of its expression, until you specify otherwise.
5292 Display the current values of the expressions on the list, just as is
5293 done when your program stops.
5295 @kindex info display
5297 Print the list of expressions previously set up to display
5298 automatically, each one with its item number, but without showing the
5299 values. This includes disabled expressions, which are marked as such.
5300 It also includes expressions which would not be displayed right now
5301 because they refer to automatic variables not currently available.
5304 @cindex display disabled out of scope
5305 If a display expression refers to local variables, then it does not make
5306 sense outside the lexical context for which it was set up. Such an
5307 expression is disabled when execution enters a context where one of its
5308 variables is not defined. For example, if you give the command
5309 @code{display last_char} while inside a function with an argument
5310 @code{last_char}, @value{GDBN} displays this argument while your program
5311 continues to stop inside that function. When it stops elsewhere---where
5312 there is no variable @code{last_char}---the display is disabled
5313 automatically. The next time your program stops where @code{last_char}
5314 is meaningful, you can enable the display expression once again.
5316 @node Print Settings
5317 @section Print settings
5319 @cindex format options
5320 @cindex print settings
5321 @value{GDBN} provides the following ways to control how arrays, structures,
5322 and symbols are printed.
5325 These settings are useful for debugging programs in any language:
5329 @item set print address
5330 @itemx set print address on
5331 @cindex print/don't print memory addresses
5332 @value{GDBN} prints memory addresses showing the location of stack
5333 traces, structure values, pointer values, breakpoints, and so forth,
5334 even when it also displays the contents of those addresses. The default
5335 is @code{on}. For example, this is what a stack frame display looks like with
5336 @code{set print address on}:
5341 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
5343 530 if (lquote != def_lquote)
5347 @item set print address off
5348 Do not print addresses when displaying their contents. For example,
5349 this is the same stack frame displayed with @code{set print address off}:
5353 (@value{GDBP}) set print addr off
5355 #0 set_quotes (lq="<<", rq=">>") at input.c:530
5356 530 if (lquote != def_lquote)
5360 You can use @samp{set print address off} to eliminate all machine
5361 dependent displays from the @value{GDBN} interface. For example, with
5362 @code{print address off}, you should get the same text for backtraces on
5363 all machines---whether or not they involve pointer arguments.
5366 @item show print address
5367 Show whether or not addresses are to be printed.
5370 When @value{GDBN} prints a symbolic address, it normally prints the
5371 closest earlier symbol plus an offset. If that symbol does not uniquely
5372 identify the address (for example, it is a name whose scope is a single
5373 source file), you may need to clarify. One way to do this is with
5374 @code{info line}, for example @samp{info line *0x4537}. Alternately,
5375 you can set @value{GDBN} to print the source file and line number when
5376 it prints a symbolic address:
5379 @item set print symbol-filename on
5380 @cindex closest symbol and offset for an address
5381 Tell @value{GDBN} to print the source file name and line number of a
5382 symbol in the symbolic form of an address.
5384 @item set print symbol-filename off
5385 Do not print source file name and line number of a symbol. This is the
5388 @item show print symbol-filename
5389 Show whether or not @value{GDBN} will print the source file name and
5390 line number of a symbol in the symbolic form of an address.
5393 Another situation where it is helpful to show symbol filenames and line
5394 numbers is when disassembling code; @value{GDBN} shows you the line
5395 number and source file that corresponds to each instruction.
5397 Also, you may wish to see the symbolic form only if the address being
5398 printed is reasonably close to the closest earlier symbol:
5401 @item set print max-symbolic-offset @var{max-offset}
5402 @cindex maximum value for offset of closest symbol
5403 Tell @value{GDBN} to only display the symbolic form of an address if the
5404 offset between the closest earlier symbol and the address is less than
5405 @var{max-offset}. The default is 0, which tells @value{GDBN}
5406 to always print the symbolic form of an address if any symbol precedes it.
5408 @item show print max-symbolic-offset
5409 Ask how large the maximum offset is that @value{GDBN} prints in a
5413 @cindex wild pointer, interpreting
5414 @cindex pointer, finding referent
5415 If you have a pointer and you are not sure where it points, try
5416 @samp{set print symbol-filename on}. Then you can determine the name
5417 and source file location of the variable where it points, using
5418 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
5419 For example, here @value{GDBN} shows that a variable @code{ptt} points
5420 at another variable @code{t}, defined in @file{hi2.c}:
5423 (@value{GDBP}) set print symbol-filename on
5424 (@value{GDBP}) p/a ptt
5425 $4 = 0xe008 <t in hi2.c>
5429 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
5430 does not show the symbol name and filename of the referent, even with
5431 the appropriate @code{set print} options turned on.
5434 Other settings control how different kinds of objects are printed:
5437 @item set print array
5438 @itemx set print array on
5439 @cindex pretty print arrays
5440 Pretty print arrays. This format is more convenient to read,
5441 but uses more space. The default is off.
5443 @item set print array off
5444 Return to compressed format for arrays.
5446 @item show print array
5447 Show whether compressed or pretty format is selected for displaying
5450 @item set print elements @var{number-of-elements}
5451 @cindex number of array elements to print
5452 Set a limit on how many elements of an array @value{GDBN} will print.
5453 If @value{GDBN} is printing a large array, it stops printing after it has
5454 printed the number of elements set by the @code{set print elements} command.
5455 This limit also applies to the display of strings.
5456 When @value{GDBN} starts, this limit is set to 200.
5457 Setting @var{number-of-elements} to zero means that the printing is unlimited.
5459 @item show print elements
5460 Display the number of elements of a large array that @value{GDBN} will print.
5461 If the number is 0, then the printing is unlimited.
5463 @item set print null-stop
5464 @cindex @sc{null} elements in arrays
5465 Cause @value{GDBN} to stop printing the characters of an array when the first
5466 @sc{null} is encountered. This is useful when large arrays actually
5467 contain only short strings.
5470 @item set print pretty on
5471 Cause @value{GDBN} to print structures in an indented format with one member
5472 per line, like this:
5487 @item set print pretty off
5488 Cause @value{GDBN} to print structures in a compact format, like this:
5492 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
5493 meat = 0x54 "Pork"@}
5498 This is the default format.
5500 @item show print pretty
5501 Show which format @value{GDBN} is using to print structures.
5503 @item set print sevenbit-strings on
5504 @cindex eight-bit characters in strings
5505 @cindex octal escapes in strings
5506 Print using only seven-bit characters; if this option is set,
5507 @value{GDBN} displays any eight-bit characters (in strings or
5508 character values) using the notation @code{\}@var{nnn}. This setting is
5509 best if you are working in English (@sc{ascii}) and you use the
5510 high-order bit of characters as a marker or ``meta'' bit.
5512 @item set print sevenbit-strings off
5513 Print full eight-bit characters. This allows the use of more
5514 international character sets, and is the default.
5516 @item show print sevenbit-strings
5517 Show whether or not @value{GDBN} is printing only seven-bit characters.
5519 @item set print union on
5520 @cindex unions in structures, printing
5521 Tell @value{GDBN} to print unions which are contained in structures. This
5522 is the default setting.
5524 @item set print union off
5525 Tell @value{GDBN} not to print unions which are contained in structures.
5527 @item show print union
5528 Ask @value{GDBN} whether or not it will print unions which are contained in
5531 For example, given the declarations
5534 typedef enum @{Tree, Bug@} Species;
5535 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
5536 typedef enum @{Caterpillar, Cocoon, Butterfly@}
5547 struct thing foo = @{Tree, @{Acorn@}@};
5551 with @code{set print union on} in effect @samp{p foo} would print
5554 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
5558 and with @code{set print union off} in effect it would print
5561 $1 = @{it = Tree, form = @{...@}@}
5567 These settings are of interest when debugging C@t{++} programs:
5570 @cindex demangling C@t{++} names
5571 @item set print demangle
5572 @itemx set print demangle on
5573 Print C@t{++} names in their source form rather than in the encoded
5574 (``mangled'') form passed to the assembler and linker for type-safe
5575 linkage. The default is on.
5577 @item show print demangle
5578 Show whether C@t{++} names are printed in mangled or demangled form.
5580 @item set print asm-demangle
5581 @itemx set print asm-demangle on
5582 Print C@t{++} names in their source form rather than their mangled form, even
5583 in assembler code printouts such as instruction disassemblies.
5586 @item show print asm-demangle
5587 Show whether C@t{++} names in assembly listings are printed in mangled
5590 @cindex C@t{++} symbol decoding style
5591 @cindex symbol decoding style, C@t{++}
5592 @item set demangle-style @var{style}
5593 Choose among several encoding schemes used by different compilers to
5594 represent C@t{++} names. The choices for @var{style} are currently:
5598 Allow @value{GDBN} to choose a decoding style by inspecting your program.
5601 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
5602 This is the default.
5605 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
5608 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
5611 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
5612 @strong{Warning:} this setting alone is not sufficient to allow
5613 debugging @code{cfront}-generated executables. @value{GDBN} would
5614 require further enhancement to permit that.
5617 If you omit @var{style}, you will see a list of possible formats.
5619 @item show demangle-style
5620 Display the encoding style currently in use for decoding C@t{++} symbols.
5622 @item set print object
5623 @itemx set print object on
5624 @cindex derived type of an object, printing
5625 When displaying a pointer to an object, identify the @emph{actual}
5626 (derived) type of the object rather than the @emph{declared} type, using
5627 the virtual function table.
5629 @item set print object off
5630 Display only the declared type of objects, without reference to the
5631 virtual function table. This is the default setting.
5633 @item show print object
5634 Show whether actual, or declared, object types are displayed.
5636 @item set print static-members
5637 @itemx set print static-members on
5638 @cindex static members of C@t{++} objects
5639 Print static members when displaying a C@t{++} object. The default is on.
5641 @item set print static-members off
5642 Do not print static members when displaying a C@t{++} object.
5644 @item show print static-members
5645 Show whether C@t{++} static members are printed, or not.
5647 @c These don't work with HP ANSI C++ yet.
5648 @item set print vtbl
5649 @itemx set print vtbl on
5650 @cindex pretty print C@t{++} virtual function tables
5651 Pretty print C@t{++} virtual function tables. The default is off.
5652 (The @code{vtbl} commands do not work on programs compiled with the HP
5653 ANSI C@t{++} compiler (@code{aCC}).)
5655 @item set print vtbl off
5656 Do not pretty print C@t{++} virtual function tables.
5658 @item show print vtbl
5659 Show whether C@t{++} virtual function tables are pretty printed, or not.
5663 @section Value history
5665 @cindex value history
5666 Values printed by the @code{print} command are saved in the @value{GDBN}
5667 @dfn{value history}. This allows you to refer to them in other expressions.
5668 Values are kept until the symbol table is re-read or discarded
5669 (for example with the @code{file} or @code{symbol-file} commands).
5670 When the symbol table changes, the value history is discarded,
5671 since the values may contain pointers back to the types defined in the
5676 @cindex history number
5677 The values printed are given @dfn{history numbers} by which you can
5678 refer to them. These are successive integers starting with one.
5679 @code{print} shows you the history number assigned to a value by
5680 printing @samp{$@var{num} = } before the value; here @var{num} is the
5683 To refer to any previous value, use @samp{$} followed by the value's
5684 history number. The way @code{print} labels its output is designed to
5685 remind you of this. Just @code{$} refers to the most recent value in
5686 the history, and @code{$$} refers to the value before that.
5687 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
5688 is the value just prior to @code{$$}, @code{$$1} is equivalent to
5689 @code{$$}, and @code{$$0} is equivalent to @code{$}.
5691 For example, suppose you have just printed a pointer to a structure and
5692 want to see the contents of the structure. It suffices to type
5698 If you have a chain of structures where the component @code{next} points
5699 to the next one, you can print the contents of the next one with this:
5706 You can print successive links in the chain by repeating this
5707 command---which you can do by just typing @key{RET}.
5709 Note that the history records values, not expressions. If the value of
5710 @code{x} is 4 and you type these commands:
5718 then the value recorded in the value history by the @code{print} command
5719 remains 4 even though the value of @code{x} has changed.
5724 Print the last ten values in the value history, with their item numbers.
5725 This is like @samp{p@ $$9} repeated ten times, except that @code{show
5726 values} does not change the history.
5728 @item show values @var{n}
5729 Print ten history values centered on history item number @var{n}.
5732 Print ten history values just after the values last printed. If no more
5733 values are available, @code{show values +} produces no display.
5736 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
5737 same effect as @samp{show values +}.
5739 @node Convenience Vars
5740 @section Convenience variables
5742 @cindex convenience variables
5743 @value{GDBN} provides @dfn{convenience variables} that you can use within
5744 @value{GDBN} to hold on to a value and refer to it later. These variables
5745 exist entirely within @value{GDBN}; they are not part of your program, and
5746 setting a convenience variable has no direct effect on further execution
5747 of your program. That is why you can use them freely.
5749 Convenience variables are prefixed with @samp{$}. Any name preceded by
5750 @samp{$} can be used for a convenience variable, unless it is one of
5751 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
5752 (Value history references, in contrast, are @emph{numbers} preceded
5753 by @samp{$}. @xref{Value History, ,Value history}.)
5755 You can save a value in a convenience variable with an assignment
5756 expression, just as you would set a variable in your program.
5760 set $foo = *object_ptr
5764 would save in @code{$foo} the value contained in the object pointed to by
5767 Using a convenience variable for the first time creates it, but its
5768 value is @code{void} until you assign a new value. You can alter the
5769 value with another assignment at any time.
5771 Convenience variables have no fixed types. You can assign a convenience
5772 variable any type of value, including structures and arrays, even if
5773 that variable already has a value of a different type. The convenience
5774 variable, when used as an expression, has the type of its current value.
5777 @kindex show convenience
5778 @item show convenience
5779 Print a list of convenience variables used so far, and their values.
5780 Abbreviated @code{show conv}.
5783 One of the ways to use a convenience variable is as a counter to be
5784 incremented or a pointer to be advanced. For example, to print
5785 a field from successive elements of an array of structures:
5789 print bar[$i++]->contents
5793 Repeat that command by typing @key{RET}.
5795 Some convenience variables are created automatically by @value{GDBN} and given
5796 values likely to be useful.
5799 @vindex $_@r{, convenience variable}
5801 The variable @code{$_} is automatically set by the @code{x} command to
5802 the last address examined (@pxref{Memory, ,Examining memory}). Other
5803 commands which provide a default address for @code{x} to examine also
5804 set @code{$_} to that address; these commands include @code{info line}
5805 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
5806 except when set by the @code{x} command, in which case it is a pointer
5807 to the type of @code{$__}.
5809 @vindex $__@r{, convenience variable}
5811 The variable @code{$__} is automatically set by the @code{x} command
5812 to the value found in the last address examined. Its type is chosen
5813 to match the format in which the data was printed.
5816 @vindex $_exitcode@r{, convenience variable}
5817 The variable @code{$_exitcode} is automatically set to the exit code when
5818 the program being debugged terminates.
5821 On HP-UX systems, if you refer to a function or variable name that
5822 begins with a dollar sign, @value{GDBN} searches for a user or system
5823 name first, before it searches for a convenience variable.
5829 You can refer to machine register contents, in expressions, as variables
5830 with names starting with @samp{$}. The names of registers are different
5831 for each machine; use @code{info registers} to see the names used on
5835 @kindex info registers
5836 @item info registers
5837 Print the names and values of all registers except floating-point
5838 and vector registers (in the selected stack frame).
5840 @kindex info all-registers
5841 @cindex floating point registers
5842 @item info all-registers
5843 Print the names and values of all registers, including floating-point
5844 and vector registers (in the selected stack frame).
5846 @item info registers @var{regname} @dots{}
5847 Print the @dfn{relativized} value of each specified register @var{regname}.
5848 As discussed in detail below, register values are normally relative to
5849 the selected stack frame. @var{regname} may be any register name valid on
5850 the machine you are using, with or without the initial @samp{$}.
5853 @value{GDBN} has four ``standard'' register names that are available (in
5854 expressions) on most machines---whenever they do not conflict with an
5855 architecture's canonical mnemonics for registers. The register names
5856 @code{$pc} and @code{$sp} are used for the program counter register and
5857 the stack pointer. @code{$fp} is used for a register that contains a
5858 pointer to the current stack frame, and @code{$ps} is used for a
5859 register that contains the processor status. For example,
5860 you could print the program counter in hex with
5867 or print the instruction to be executed next with
5874 or add four to the stack pointer@footnote{This is a way of removing
5875 one word from the stack, on machines where stacks grow downward in
5876 memory (most machines, nowadays). This assumes that the innermost
5877 stack frame is selected; setting @code{$sp} is not allowed when other
5878 stack frames are selected. To pop entire frames off the stack,
5879 regardless of machine architecture, use @code{return};
5880 see @ref{Returning, ,Returning from a function}.} with
5886 Whenever possible, these four standard register names are available on
5887 your machine even though the machine has different canonical mnemonics,
5888 so long as there is no conflict. The @code{info registers} command
5889 shows the canonical names. For example, on the SPARC, @code{info
5890 registers} displays the processor status register as @code{$psr} but you
5891 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
5892 is an alias for the @sc{eflags} register.
5894 @value{GDBN} always considers the contents of an ordinary register as an
5895 integer when the register is examined in this way. Some machines have
5896 special registers which can hold nothing but floating point; these
5897 registers are considered to have floating point values. There is no way
5898 to refer to the contents of an ordinary register as floating point value
5899 (although you can @emph{print} it as a floating point value with
5900 @samp{print/f $@var{regname}}).
5902 Some registers have distinct ``raw'' and ``virtual'' data formats. This
5903 means that the data format in which the register contents are saved by
5904 the operating system is not the same one that your program normally
5905 sees. For example, the registers of the 68881 floating point
5906 coprocessor are always saved in ``extended'' (raw) format, but all C
5907 programs expect to work with ``double'' (virtual) format. In such
5908 cases, @value{GDBN} normally works with the virtual format only (the format
5909 that makes sense for your program), but the @code{info registers} command
5910 prints the data in both formats.
5912 Normally, register values are relative to the selected stack frame
5913 (@pxref{Selection, ,Selecting a frame}). This means that you get the
5914 value that the register would contain if all stack frames farther in
5915 were exited and their saved registers restored. In order to see the
5916 true contents of hardware registers, you must select the innermost
5917 frame (with @samp{frame 0}).
5919 However, @value{GDBN} must deduce where registers are saved, from the machine
5920 code generated by your compiler. If some registers are not saved, or if
5921 @value{GDBN} is unable to locate the saved registers, the selected stack
5922 frame makes no difference.
5924 @node Floating Point Hardware
5925 @section Floating point hardware
5926 @cindex floating point
5928 Depending on the configuration, @value{GDBN} may be able to give
5929 you more information about the status of the floating point hardware.
5934 Display hardware-dependent information about the floating
5935 point unit. The exact contents and layout vary depending on the
5936 floating point chip. Currently, @samp{info float} is supported on
5937 the ARM and x86 machines.
5941 @section Vector Unit
5944 Depending on the configuration, @value{GDBN} may be able to give you
5945 more information about the status of the vector unit.
5950 Display information about the vector unit. The exact contents and
5951 layout vary depending on the hardware.
5954 @node Auxiliary Vector
5955 @section Operating system auxiliary vector
5956 @cindex auxiliary vector
5957 @cindex vector, auxiliary
5959 Some operating systems supply an @dfn{auxiliary vector} to programs at
5960 startup. This is akin to the arguments and environment that you
5961 specify for a program, but contains a system-dependent variety of
5962 binary values that tell system libraries important details about the
5963 hardware, operating system, and process. Each value's purpose is
5964 identified by an integer tag; the meanings are well-known but system-specific.
5965 Depending on the configuration and operating system facilities,
5966 @value{GDBN} may be able to show you this information.
5971 Display the auxiliary vector of the inferior, which can be either a
5972 live process or a core dump file. @value{GDBN} prints each tag value
5973 numerically, and also shows names and text descriptions for recognized
5974 tags. Some values in the vector are numbers, some bit masks, and some
5975 pointers to strings or other data. @value{GDBN} displays each value in the
5976 most appropriate form for a recognized tag, and in hexadecimal for
5977 an unrecognized tag.
5980 @node Memory Region Attributes
5981 @section Memory region attributes
5982 @cindex memory region attributes
5984 @dfn{Memory region attributes} allow you to describe special handling
5985 required by regions of your target's memory. @value{GDBN} uses attributes
5986 to determine whether to allow certain types of memory accesses; whether to
5987 use specific width accesses; and whether to cache target memory.
5989 Defined memory regions can be individually enabled and disabled. When a
5990 memory region is disabled, @value{GDBN} uses the default attributes when
5991 accessing memory in that region. Similarly, if no memory regions have
5992 been defined, @value{GDBN} uses the default attributes when accessing
5995 When a memory region is defined, it is given a number to identify it;
5996 to enable, disable, or remove a memory region, you specify that number.
6000 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
6001 Define memory region bounded by @var{lower} and @var{upper} with
6002 attributes @var{attributes}@dots{}. Note that @var{upper} == 0 is a
6003 special case: it is treated as the the target's maximum memory address.
6004 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
6007 @item delete mem @var{nums}@dots{}
6008 Remove memory regions @var{nums}@dots{}.
6011 @item disable mem @var{nums}@dots{}
6012 Disable memory regions @var{nums}@dots{}.
6013 A disabled memory region is not forgotten.
6014 It may be enabled again later.
6017 @item enable mem @var{nums}@dots{}
6018 Enable memory regions @var{nums}@dots{}.
6022 Print a table of all defined memory regions, with the following columns
6026 @item Memory Region Number
6027 @item Enabled or Disabled.
6028 Enabled memory regions are marked with @samp{y}.
6029 Disabled memory regions are marked with @samp{n}.
6032 The address defining the inclusive lower bound of the memory region.
6035 The address defining the exclusive upper bound of the memory region.
6038 The list of attributes set for this memory region.
6043 @subsection Attributes
6045 @subsubsection Memory Access Mode
6046 The access mode attributes set whether @value{GDBN} may make read or
6047 write accesses to a memory region.
6049 While these attributes prevent @value{GDBN} from performing invalid
6050 memory accesses, they do nothing to prevent the target system, I/O DMA,
6051 etc. from accessing memory.
6055 Memory is read only.
6057 Memory is write only.
6059 Memory is read/write. This is the default.
6062 @subsubsection Memory Access Size
6063 The acccess size attributes tells @value{GDBN} to use specific sized
6064 accesses in the memory region. Often memory mapped device registers
6065 require specific sized accesses. If no access size attribute is
6066 specified, @value{GDBN} may use accesses of any size.
6070 Use 8 bit memory accesses.
6072 Use 16 bit memory accesses.
6074 Use 32 bit memory accesses.
6076 Use 64 bit memory accesses.
6079 @c @subsubsection Hardware/Software Breakpoints
6080 @c The hardware/software breakpoint attributes set whether @value{GDBN}
6081 @c will use hardware or software breakpoints for the internal breakpoints
6082 @c used by the step, next, finish, until, etc. commands.
6086 @c Always use hardware breakpoints
6087 @c @item swbreak (default)
6090 @subsubsection Data Cache
6091 The data cache attributes set whether @value{GDBN} will cache target
6092 memory. While this generally improves performance by reducing debug
6093 protocol overhead, it can lead to incorrect results because @value{GDBN}
6094 does not know about volatile variables or memory mapped device
6099 Enable @value{GDBN} to cache target memory.
6101 Disable @value{GDBN} from caching target memory. This is the default.
6104 @c @subsubsection Memory Write Verification
6105 @c The memory write verification attributes set whether @value{GDBN}
6106 @c will re-reads data after each write to verify the write was successful.
6110 @c @item noverify (default)
6113 @node Dump/Restore Files
6114 @section Copy between memory and a file
6115 @cindex dump/restore files
6116 @cindex append data to a file
6117 @cindex dump data to a file
6118 @cindex restore data from a file
6120 You can use the commands @code{dump}, @code{append}, and
6121 @code{restore} to copy data between target memory and a file. The
6122 @code{dump} and @code{append} commands write data to a file, and the
6123 @code{restore} command reads data from a file back into the inferior's
6124 memory. Files may be in binary, Motorola S-record, Intel hex, or
6125 Tektronix Hex format; however, @value{GDBN} can only append to binary
6131 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6132 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
6133 Dump the contents of memory from @var{start_addr} to @var{end_addr},
6134 or the value of @var{expr}, to @var{filename} in the given format.
6136 The @var{format} parameter may be any one of:
6143 Motorola S-record format.
6145 Tektronix Hex format.
6148 @value{GDBN} uses the same definitions of these formats as the
6149 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
6150 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
6154 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6155 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
6156 Append the contents of memory from @var{start_addr} to @var{end_addr},
6157 or the value of @var{expr}, to @var{filename}, in raw binary form.
6158 (@value{GDBN} can only append data to files in raw binary form.)
6161 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
6162 Restore the contents of file @var{filename} into memory. The
6163 @code{restore} command can automatically recognize any known @sc{bfd}
6164 file format, except for raw binary. To restore a raw binary file you
6165 must specify the optional keyword @code{binary} after the filename.
6167 If @var{bias} is non-zero, its value will be added to the addresses
6168 contained in the file. Binary files always start at address zero, so
6169 they will be restored at address @var{bias}. Other bfd files have
6170 a built-in location; they will be restored at offset @var{bias}
6173 If @var{start} and/or @var{end} are non-zero, then only data between
6174 file offset @var{start} and file offset @var{end} will be restored.
6175 These offsets are relative to the addresses in the file, before
6176 the @var{bias} argument is applied.
6180 @node Core File Generation
6181 @section How to Produce a Core File from Your Program
6182 @cindex dump core from inferior
6184 A @dfn{core file} or @dfn{core dump} is a file that records the memory
6185 image of a running process and its process status (register values
6186 etc.). Its primary use is post-mortem debugging of a program that
6187 crashed while it ran outside a debugger. A program that crashes
6188 automatically produces a core file, unless this feature is disabled by
6189 the user. @xref{Files}, for information on invoking @value{GDBN} in
6190 the post-mortem debugging mode.
6192 Occasionally, you may wish to produce a core file of the program you
6193 are debugging in order to preserve a snapshot of its state.
6194 @value{GDBN} has a special command for that.
6198 @kindex generate-core-file
6199 @item generate-core-file [@var{file}]
6200 @itemx gcore [@var{file}]
6201 Produce a core dump of the inferior process. The optional argument
6202 @var{file} specifies the file name where to put the core dump. If not
6203 specified, the file name defaults to @file{core.@var{pid}}, where
6204 @var{pid} is the inferior process ID.
6206 Note that this command is implemented only for some systems (as of
6207 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
6210 @node Character Sets
6211 @section Character Sets
6212 @cindex character sets
6214 @cindex translating between character sets
6215 @cindex host character set
6216 @cindex target character set
6218 If the program you are debugging uses a different character set to
6219 represent characters and strings than the one @value{GDBN} uses itself,
6220 @value{GDBN} can automatically translate between the character sets for
6221 you. The character set @value{GDBN} uses we call the @dfn{host
6222 character set}; the one the inferior program uses we call the
6223 @dfn{target character set}.
6225 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
6226 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
6227 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
6228 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
6229 then the host character set is Latin-1, and the target character set is
6230 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
6231 target-charset EBCDIC-US}, then @value{GDBN} translates between
6232 @sc{ebcdic} and Latin 1 as you print character or string values, or use
6233 character and string literals in expressions.
6235 @value{GDBN} has no way to automatically recognize which character set
6236 the inferior program uses; you must tell it, using the @code{set
6237 target-charset} command, described below.
6239 Here are the commands for controlling @value{GDBN}'s character set
6243 @item set target-charset @var{charset}
6244 @kindex set target-charset
6245 Set the current target character set to @var{charset}. We list the
6246 character set names @value{GDBN} recognizes below, but if you type
6247 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6248 list the target character sets it supports.
6252 @item set host-charset @var{charset}
6253 @kindex set host-charset
6254 Set the current host character set to @var{charset}.
6256 By default, @value{GDBN} uses a host character set appropriate to the
6257 system it is running on; you can override that default using the
6258 @code{set host-charset} command.
6260 @value{GDBN} can only use certain character sets as its host character
6261 set. We list the character set names @value{GDBN} recognizes below, and
6262 indicate which can be host character sets, but if you type
6263 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6264 list the host character sets it supports.
6266 @item set charset @var{charset}
6268 Set the current host and target character sets to @var{charset}. As
6269 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
6270 @value{GDBN} will list the name of the character sets that can be used
6271 for both host and target.
6275 @kindex show charset
6276 Show the names of the current host and target charsets.
6278 @itemx show host-charset
6279 @kindex show host-charset
6280 Show the name of the current host charset.
6282 @itemx show target-charset
6283 @kindex show target-charset
6284 Show the name of the current target charset.
6288 @value{GDBN} currently includes support for the following character
6294 @cindex ASCII character set
6295 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
6299 @cindex ISO 8859-1 character set
6300 @cindex ISO Latin 1 character set
6301 The ISO Latin 1 character set. This extends @sc{ascii} with accented
6302 characters needed for French, German, and Spanish. @value{GDBN} can use
6303 this as its host character set.
6307 @cindex EBCDIC character set
6308 @cindex IBM1047 character set
6309 Variants of the @sc{ebcdic} character set, used on some of IBM's
6310 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
6311 @value{GDBN} cannot use these as its host character set.
6315 Note that these are all single-byte character sets. More work inside
6316 GDB is needed to support multi-byte or variable-width character
6317 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
6319 Here is an example of @value{GDBN}'s character set support in action.
6320 Assume that the following source code has been placed in the file
6321 @file{charset-test.c}:
6327 = @{72, 101, 108, 108, 111, 44, 32, 119,
6328 111, 114, 108, 100, 33, 10, 0@};
6329 char ibm1047_hello[]
6330 = @{200, 133, 147, 147, 150, 107, 64, 166,
6331 150, 153, 147, 132, 90, 37, 0@};
6335 printf ("Hello, world!\n");
6339 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
6340 containing the string @samp{Hello, world!} followed by a newline,
6341 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
6343 We compile the program, and invoke the debugger on it:
6346 $ gcc -g charset-test.c -o charset-test
6347 $ gdb -nw charset-test
6348 GNU gdb 2001-12-19-cvs
6349 Copyright 2001 Free Software Foundation, Inc.
6354 We can use the @code{show charset} command to see what character sets
6355 @value{GDBN} is currently using to interpret and display characters and
6359 (@value{GDBP}) show charset
6360 The current host and target character set is `ISO-8859-1'.
6364 For the sake of printing this manual, let's use @sc{ascii} as our
6365 initial character set:
6367 (@value{GDBP}) set charset ASCII
6368 (@value{GDBP}) show charset
6369 The current host and target character set is `ASCII'.
6373 Let's assume that @sc{ascii} is indeed the correct character set for our
6374 host system --- in other words, let's assume that if @value{GDBN} prints
6375 characters using the @sc{ascii} character set, our terminal will display
6376 them properly. Since our current target character set is also
6377 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
6380 (@value{GDBP}) print ascii_hello
6381 $1 = 0x401698 "Hello, world!\n"
6382 (@value{GDBP}) print ascii_hello[0]
6387 @value{GDBN} uses the target character set for character and string
6388 literals you use in expressions:
6391 (@value{GDBP}) print '+'
6396 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
6399 @value{GDBN} relies on the user to tell it which character set the
6400 target program uses. If we print @code{ibm1047_hello} while our target
6401 character set is still @sc{ascii}, we get jibberish:
6404 (@value{GDBP}) print ibm1047_hello
6405 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
6406 (@value{GDBP}) print ibm1047_hello[0]
6411 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
6412 @value{GDBN} tells us the character sets it supports:
6415 (@value{GDBP}) set target-charset
6416 ASCII EBCDIC-US IBM1047 ISO-8859-1
6417 (@value{GDBP}) set target-charset
6420 We can select @sc{ibm1047} as our target character set, and examine the
6421 program's strings again. Now the @sc{ascii} string is wrong, but
6422 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
6423 target character set, @sc{ibm1047}, to the host character set,
6424 @sc{ascii}, and they display correctly:
6427 (@value{GDBP}) set target-charset IBM1047
6428 (@value{GDBP}) show charset
6429 The current host character set is `ASCII'.
6430 The current target character set is `IBM1047'.
6431 (@value{GDBP}) print ascii_hello
6432 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
6433 (@value{GDBP}) print ascii_hello[0]
6435 (@value{GDBP}) print ibm1047_hello
6436 $8 = 0x4016a8 "Hello, world!\n"
6437 (@value{GDBP}) print ibm1047_hello[0]
6442 As above, @value{GDBN} uses the target character set for character and
6443 string literals you use in expressions:
6446 (@value{GDBP}) print '+'
6451 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
6456 @chapter C Preprocessor Macros
6458 Some languages, such as C and C@t{++}, provide a way to define and invoke
6459 ``preprocessor macros'' which expand into strings of tokens.
6460 @value{GDBN} can evaluate expressions containing macro invocations, show
6461 the result of macro expansion, and show a macro's definition, including
6462 where it was defined.
6464 You may need to compile your program specially to provide @value{GDBN}
6465 with information about preprocessor macros. Most compilers do not
6466 include macros in their debugging information, even when you compile
6467 with the @option{-g} flag. @xref{Compilation}.
6469 A program may define a macro at one point, remove that definition later,
6470 and then provide a different definition after that. Thus, at different
6471 points in the program, a macro may have different definitions, or have
6472 no definition at all. If there is a current stack frame, @value{GDBN}
6473 uses the macros in scope at that frame's source code line. Otherwise,
6474 @value{GDBN} uses the macros in scope at the current listing location;
6477 At the moment, @value{GDBN} does not support the @code{##}
6478 token-splicing operator, the @code{#} stringification operator, or
6479 variable-arity macros.
6481 Whenever @value{GDBN} evaluates an expression, it always expands any
6482 macro invocations present in the expression. @value{GDBN} also provides
6483 the following commands for working with macros explicitly.
6487 @kindex macro expand
6488 @cindex macro expansion, showing the results of preprocessor
6489 @cindex preprocessor macro expansion, showing the results of
6490 @cindex expanding preprocessor macros
6491 @item macro expand @var{expression}
6492 @itemx macro exp @var{expression}
6493 Show the results of expanding all preprocessor macro invocations in
6494 @var{expression}. Since @value{GDBN} simply expands macros, but does
6495 not parse the result, @var{expression} need not be a valid expression;
6496 it can be any string of tokens.
6498 @item macro expand-once @var{expression}
6499 @itemx macro exp1 @var{expression}
6500 @cindex expand macro once
6501 @i{(This command is not yet implemented.)} Show the results of
6502 expanding those preprocessor macro invocations that appear explicitly in
6503 @var{expression}. Macro invocations appearing in that expansion are
6504 left unchanged. This command allows you to see the effect of a
6505 particular macro more clearly, without being confused by further
6506 expansions. Since @value{GDBN} simply expands macros, but does not
6507 parse the result, @var{expression} need not be a valid expression; it
6508 can be any string of tokens.
6511 @cindex macro definition, showing
6512 @cindex definition, showing a macro's
6513 @item info macro @var{macro}
6514 Show the definition of the macro named @var{macro}, and describe the
6515 source location where that definition was established.
6517 @kindex macro define
6518 @cindex user-defined macros
6519 @cindex defining macros interactively
6520 @cindex macros, user-defined
6521 @item macro define @var{macro} @var{replacement-list}
6522 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
6523 @i{(This command is not yet implemented.)} Introduce a definition for a
6524 preprocessor macro named @var{macro}, invocations of which are replaced
6525 by the tokens given in @var{replacement-list}. The first form of this
6526 command defines an ``object-like'' macro, which takes no arguments; the
6527 second form defines a ``function-like'' macro, which takes the arguments
6528 given in @var{arglist}.
6530 A definition introduced by this command is in scope in every expression
6531 evaluated in @value{GDBN}, until it is removed with the @command{macro
6532 undef} command, described below. The definition overrides all
6533 definitions for @var{macro} present in the program being debugged, as
6534 well as any previous user-supplied definition.
6537 @item macro undef @var{macro}
6538 @i{(This command is not yet implemented.)} Remove any user-supplied
6539 definition for the macro named @var{macro}. This command only affects
6540 definitions provided with the @command{macro define} command, described
6541 above; it cannot remove definitions present in the program being
6546 @cindex macros, example of debugging with
6547 Here is a transcript showing the above commands in action. First, we
6548 show our source files:
6556 #define ADD(x) (M + x)
6561 printf ("Hello, world!\n");
6563 printf ("We're so creative.\n");
6565 printf ("Goodbye, world!\n");
6572 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
6573 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
6574 compiler includes information about preprocessor macros in the debugging
6578 $ gcc -gdwarf-2 -g3 sample.c -o sample
6582 Now, we start @value{GDBN} on our sample program:
6586 GNU gdb 2002-05-06-cvs
6587 Copyright 2002 Free Software Foundation, Inc.
6588 GDB is free software, @dots{}
6592 We can expand macros and examine their definitions, even when the
6593 program is not running. @value{GDBN} uses the current listing position
6594 to decide which macro definitions are in scope:
6597 (@value{GDBP}) list main
6600 5 #define ADD(x) (M + x)
6605 10 printf ("Hello, world!\n");
6607 12 printf ("We're so creative.\n");
6608 (@value{GDBP}) info macro ADD
6609 Defined at /home/jimb/gdb/macros/play/sample.c:5
6610 #define ADD(x) (M + x)
6611 (@value{GDBP}) info macro Q
6612 Defined at /home/jimb/gdb/macros/play/sample.h:1
6613 included at /home/jimb/gdb/macros/play/sample.c:2
6615 (@value{GDBP}) macro expand ADD(1)
6616 expands to: (42 + 1)
6617 (@value{GDBP}) macro expand-once ADD(1)
6618 expands to: once (M + 1)
6622 In the example above, note that @command{macro expand-once} expands only
6623 the macro invocation explicit in the original text --- the invocation of
6624 @code{ADD} --- but does not expand the invocation of the macro @code{M},
6625 which was introduced by @code{ADD}.
6627 Once the program is running, GDB uses the macro definitions in force at
6628 the source line of the current stack frame:
6631 (@value{GDBP}) break main
6632 Breakpoint 1 at 0x8048370: file sample.c, line 10.
6634 Starting program: /home/jimb/gdb/macros/play/sample
6636 Breakpoint 1, main () at sample.c:10
6637 10 printf ("Hello, world!\n");
6641 At line 10, the definition of the macro @code{N} at line 9 is in force:
6644 (@value{GDBP}) info macro N
6645 Defined at /home/jimb/gdb/macros/play/sample.c:9
6647 (@value{GDBP}) macro expand N Q M
6649 (@value{GDBP}) print N Q M
6654 As we step over directives that remove @code{N}'s definition, and then
6655 give it a new definition, @value{GDBN} finds the definition (or lack
6656 thereof) in force at each point:
6661 12 printf ("We're so creative.\n");
6662 (@value{GDBP}) info macro N
6663 The symbol `N' has no definition as a C/C++ preprocessor macro
6664 at /home/jimb/gdb/macros/play/sample.c:12
6667 14 printf ("Goodbye, world!\n");
6668 (@value{GDBP}) info macro N
6669 Defined at /home/jimb/gdb/macros/play/sample.c:13
6671 (@value{GDBP}) macro expand N Q M
6672 expands to: 1729 < 42
6673 (@value{GDBP}) print N Q M
6680 @chapter Tracepoints
6681 @c This chapter is based on the documentation written by Michael
6682 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
6685 In some applications, it is not feasible for the debugger to interrupt
6686 the program's execution long enough for the developer to learn
6687 anything helpful about its behavior. If the program's correctness
6688 depends on its real-time behavior, delays introduced by a debugger
6689 might cause the program to change its behavior drastically, or perhaps
6690 fail, even when the code itself is correct. It is useful to be able
6691 to observe the program's behavior without interrupting it.
6693 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
6694 specify locations in the program, called @dfn{tracepoints}, and
6695 arbitrary expressions to evaluate when those tracepoints are reached.
6696 Later, using the @code{tfind} command, you can examine the values
6697 those expressions had when the program hit the tracepoints. The
6698 expressions may also denote objects in memory---structures or arrays,
6699 for example---whose values @value{GDBN} should record; while visiting
6700 a particular tracepoint, you may inspect those objects as if they were
6701 in memory at that moment. However, because @value{GDBN} records these
6702 values without interacting with you, it can do so quickly and
6703 unobtrusively, hopefully not disturbing the program's behavior.
6705 The tracepoint facility is currently available only for remote
6706 targets. @xref{Targets}. In addition, your remote target must know how
6707 to collect trace data. This functionality is implemented in the remote
6708 stub; however, none of the stubs distributed with @value{GDBN} support
6709 tracepoints as of this writing.
6711 This chapter describes the tracepoint commands and features.
6715 * Analyze Collected Data::
6716 * Tracepoint Variables::
6719 @node Set Tracepoints
6720 @section Commands to Set Tracepoints
6722 Before running such a @dfn{trace experiment}, an arbitrary number of
6723 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
6724 tracepoint has a number assigned to it by @value{GDBN}. Like with
6725 breakpoints, tracepoint numbers are successive integers starting from
6726 one. Many of the commands associated with tracepoints take the
6727 tracepoint number as their argument, to identify which tracepoint to
6730 For each tracepoint, you can specify, in advance, some arbitrary set
6731 of data that you want the target to collect in the trace buffer when
6732 it hits that tracepoint. The collected data can include registers,
6733 local variables, or global data. Later, you can use @value{GDBN}
6734 commands to examine the values these data had at the time the
6737 This section describes commands to set tracepoints and associated
6738 conditions and actions.
6741 * Create and Delete Tracepoints::
6742 * Enable and Disable Tracepoints::
6743 * Tracepoint Passcounts::
6744 * Tracepoint Actions::
6745 * Listing Tracepoints::
6746 * Starting and Stopping Trace Experiment::
6749 @node Create and Delete Tracepoints
6750 @subsection Create and Delete Tracepoints
6753 @cindex set tracepoint
6756 The @code{trace} command is very similar to the @code{break} command.
6757 Its argument can be a source line, a function name, or an address in
6758 the target program. @xref{Set Breaks}. The @code{trace} command
6759 defines a tracepoint, which is a point in the target program where the
6760 debugger will briefly stop, collect some data, and then allow the
6761 program to continue. Setting a tracepoint or changing its commands
6762 doesn't take effect until the next @code{tstart} command; thus, you
6763 cannot change the tracepoint attributes once a trace experiment is
6766 Here are some examples of using the @code{trace} command:
6769 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
6771 (@value{GDBP}) @b{trace +2} // 2 lines forward
6773 (@value{GDBP}) @b{trace my_function} // first source line of function
6775 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
6777 (@value{GDBP}) @b{trace *0x2117c4} // an address
6781 You can abbreviate @code{trace} as @code{tr}.
6784 @cindex last tracepoint number
6785 @cindex recent tracepoint number
6786 @cindex tracepoint number
6787 The convenience variable @code{$tpnum} records the tracepoint number
6788 of the most recently set tracepoint.
6790 @kindex delete tracepoint
6791 @cindex tracepoint deletion
6792 @item delete tracepoint @r{[}@var{num}@r{]}
6793 Permanently delete one or more tracepoints. With no argument, the
6794 default is to delete all tracepoints.
6799 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
6801 (@value{GDBP}) @b{delete trace} // remove all tracepoints
6805 You can abbreviate this command as @code{del tr}.
6808 @node Enable and Disable Tracepoints
6809 @subsection Enable and Disable Tracepoints
6812 @kindex disable tracepoint
6813 @item disable tracepoint @r{[}@var{num}@r{]}
6814 Disable tracepoint @var{num}, or all tracepoints if no argument
6815 @var{num} is given. A disabled tracepoint will have no effect during
6816 the next trace experiment, but it is not forgotten. You can re-enable
6817 a disabled tracepoint using the @code{enable tracepoint} command.
6819 @kindex enable tracepoint
6820 @item enable tracepoint @r{[}@var{num}@r{]}
6821 Enable tracepoint @var{num}, or all tracepoints. The enabled
6822 tracepoints will become effective the next time a trace experiment is
6826 @node Tracepoint Passcounts
6827 @subsection Tracepoint Passcounts
6831 @cindex tracepoint pass count
6832 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
6833 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
6834 automatically stop a trace experiment. If a tracepoint's passcount is
6835 @var{n}, then the trace experiment will be automatically stopped on
6836 the @var{n}'th time that tracepoint is hit. If the tracepoint number
6837 @var{num} is not specified, the @code{passcount} command sets the
6838 passcount of the most recently defined tracepoint. If no passcount is
6839 given, the trace experiment will run until stopped explicitly by the
6845 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
6846 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
6848 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
6849 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
6850 (@value{GDBP}) @b{trace foo}
6851 (@value{GDBP}) @b{pass 3}
6852 (@value{GDBP}) @b{trace bar}
6853 (@value{GDBP}) @b{pass 2}
6854 (@value{GDBP}) @b{trace baz}
6855 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
6856 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
6857 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
6858 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
6862 @node Tracepoint Actions
6863 @subsection Tracepoint Action Lists
6867 @cindex tracepoint actions
6868 @item actions @r{[}@var{num}@r{]}
6869 This command will prompt for a list of actions to be taken when the
6870 tracepoint is hit. If the tracepoint number @var{num} is not
6871 specified, this command sets the actions for the one that was most
6872 recently defined (so that you can define a tracepoint and then say
6873 @code{actions} without bothering about its number). You specify the
6874 actions themselves on the following lines, one action at a time, and
6875 terminate the actions list with a line containing just @code{end}. So
6876 far, the only defined actions are @code{collect} and
6877 @code{while-stepping}.
6879 @cindex remove actions from a tracepoint
6880 To remove all actions from a tracepoint, type @samp{actions @var{num}}
6881 and follow it immediately with @samp{end}.
6884 (@value{GDBP}) @b{collect @var{data}} // collect some data
6886 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
6888 (@value{GDBP}) @b{end} // signals the end of actions.
6891 In the following example, the action list begins with @code{collect}
6892 commands indicating the things to be collected when the tracepoint is
6893 hit. Then, in order to single-step and collect additional data
6894 following the tracepoint, a @code{while-stepping} command is used,
6895 followed by the list of things to be collected while stepping. The
6896 @code{while-stepping} command is terminated by its own separate
6897 @code{end} command. Lastly, the action list is terminated by an
6901 (@value{GDBP}) @b{trace foo}
6902 (@value{GDBP}) @b{actions}
6903 Enter actions for tracepoint 1, one per line:
6912 @kindex collect @r{(tracepoints)}
6913 @item collect @var{expr1}, @var{expr2}, @dots{}
6914 Collect values of the given expressions when the tracepoint is hit.
6915 This command accepts a comma-separated list of any valid expressions.
6916 In addition to global, static, or local variables, the following
6917 special arguments are supported:
6921 collect all registers
6924 collect all function arguments
6927 collect all local variables.
6930 You can give several consecutive @code{collect} commands, each one
6931 with a single argument, or one @code{collect} command with several
6932 arguments separated by commas: the effect is the same.
6934 The command @code{info scope} (@pxref{Symbols, info scope}) is
6935 particularly useful for figuring out what data to collect.
6937 @kindex while-stepping @r{(tracepoints)}
6938 @item while-stepping @var{n}
6939 Perform @var{n} single-step traces after the tracepoint, collecting
6940 new data at each step. The @code{while-stepping} command is
6941 followed by the list of what to collect while stepping (followed by
6942 its own @code{end} command):
6946 > collect $regs, myglobal
6952 You may abbreviate @code{while-stepping} as @code{ws} or
6956 @node Listing Tracepoints
6957 @subsection Listing Tracepoints
6960 @kindex info tracepoints
6961 @cindex information about tracepoints
6962 @item info tracepoints @r{[}@var{num}@r{]}
6963 Display information about the tracepoint @var{num}. If you don't specify
6964 a tracepoint number, displays information about all the tracepoints
6965 defined so far. For each tracepoint, the following information is
6972 whether it is enabled or disabled
6976 its passcount as given by the @code{passcount @var{n}} command
6978 its step count as given by the @code{while-stepping @var{n}} command
6980 where in the source files is the tracepoint set
6982 its action list as given by the @code{actions} command
6986 (@value{GDBP}) @b{info trace}
6987 Num Enb Address PassC StepC What
6988 1 y 0x002117c4 0 0 <gdb_asm>
6989 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
6990 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
6995 This command can be abbreviated @code{info tp}.
6998 @node Starting and Stopping Trace Experiment
6999 @subsection Starting and Stopping Trace Experiment
7003 @cindex start a new trace experiment
7004 @cindex collected data discarded
7006 This command takes no arguments. It starts the trace experiment, and
7007 begins collecting data. This has the side effect of discarding all
7008 the data collected in the trace buffer during the previous trace
7012 @cindex stop a running trace experiment
7014 This command takes no arguments. It ends the trace experiment, and
7015 stops collecting data.
7017 @strong{Note:} a trace experiment and data collection may stop
7018 automatically if any tracepoint's passcount is reached
7019 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
7022 @cindex status of trace data collection
7023 @cindex trace experiment, status of
7025 This command displays the status of the current trace data
7029 Here is an example of the commands we described so far:
7032 (@value{GDBP}) @b{trace gdb_c_test}
7033 (@value{GDBP}) @b{actions}
7034 Enter actions for tracepoint #1, one per line.
7035 > collect $regs,$locals,$args
7040 (@value{GDBP}) @b{tstart}
7041 [time passes @dots{}]
7042 (@value{GDBP}) @b{tstop}
7046 @node Analyze Collected Data
7047 @section Using the collected data
7049 After the tracepoint experiment ends, you use @value{GDBN} commands
7050 for examining the trace data. The basic idea is that each tracepoint
7051 collects a trace @dfn{snapshot} every time it is hit and another
7052 snapshot every time it single-steps. All these snapshots are
7053 consecutively numbered from zero and go into a buffer, and you can
7054 examine them later. The way you examine them is to @dfn{focus} on a
7055 specific trace snapshot. When the remote stub is focused on a trace
7056 snapshot, it will respond to all @value{GDBN} requests for memory and
7057 registers by reading from the buffer which belongs to that snapshot,
7058 rather than from @emph{real} memory or registers of the program being
7059 debugged. This means that @strong{all} @value{GDBN} commands
7060 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
7061 behave as if we were currently debugging the program state as it was
7062 when the tracepoint occurred. Any requests for data that are not in
7063 the buffer will fail.
7066 * tfind:: How to select a trace snapshot
7067 * tdump:: How to display all data for a snapshot
7068 * save-tracepoints:: How to save tracepoints for a future run
7072 @subsection @code{tfind @var{n}}
7075 @cindex select trace snapshot
7076 @cindex find trace snapshot
7077 The basic command for selecting a trace snapshot from the buffer is
7078 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
7079 counting from zero. If no argument @var{n} is given, the next
7080 snapshot is selected.
7082 Here are the various forms of using the @code{tfind} command.
7086 Find the first snapshot in the buffer. This is a synonym for
7087 @code{tfind 0} (since 0 is the number of the first snapshot).
7090 Stop debugging trace snapshots, resume @emph{live} debugging.
7093 Same as @samp{tfind none}.
7096 No argument means find the next trace snapshot.
7099 Find the previous trace snapshot before the current one. This permits
7100 retracing earlier steps.
7102 @item tfind tracepoint @var{num}
7103 Find the next snapshot associated with tracepoint @var{num}. Search
7104 proceeds forward from the last examined trace snapshot. If no
7105 argument @var{num} is given, it means find the next snapshot collected
7106 for the same tracepoint as the current snapshot.
7108 @item tfind pc @var{addr}
7109 Find the next snapshot associated with the value @var{addr} of the
7110 program counter. Search proceeds forward from the last examined trace
7111 snapshot. If no argument @var{addr} is given, it means find the next
7112 snapshot with the same value of PC as the current snapshot.
7114 @item tfind outside @var{addr1}, @var{addr2}
7115 Find the next snapshot whose PC is outside the given range of
7118 @item tfind range @var{addr1}, @var{addr2}
7119 Find the next snapshot whose PC is between @var{addr1} and
7120 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
7122 @item tfind line @r{[}@var{file}:@r{]}@var{n}
7123 Find the next snapshot associated with the source line @var{n}. If
7124 the optional argument @var{file} is given, refer to line @var{n} in
7125 that source file. Search proceeds forward from the last examined
7126 trace snapshot. If no argument @var{n} is given, it means find the
7127 next line other than the one currently being examined; thus saying
7128 @code{tfind line} repeatedly can appear to have the same effect as
7129 stepping from line to line in a @emph{live} debugging session.
7132 The default arguments for the @code{tfind} commands are specifically
7133 designed to make it easy to scan through the trace buffer. For
7134 instance, @code{tfind} with no argument selects the next trace
7135 snapshot, and @code{tfind -} with no argument selects the previous
7136 trace snapshot. So, by giving one @code{tfind} command, and then
7137 simply hitting @key{RET} repeatedly you can examine all the trace
7138 snapshots in order. Or, by saying @code{tfind -} and then hitting
7139 @key{RET} repeatedly you can examine the snapshots in reverse order.
7140 The @code{tfind line} command with no argument selects the snapshot
7141 for the next source line executed. The @code{tfind pc} command with
7142 no argument selects the next snapshot with the same program counter
7143 (PC) as the current frame. The @code{tfind tracepoint} command with
7144 no argument selects the next trace snapshot collected by the same
7145 tracepoint as the current one.
7147 In addition to letting you scan through the trace buffer manually,
7148 these commands make it easy to construct @value{GDBN} scripts that
7149 scan through the trace buffer and print out whatever collected data
7150 you are interested in. Thus, if we want to examine the PC, FP, and SP
7151 registers from each trace frame in the buffer, we can say this:
7154 (@value{GDBP}) @b{tfind start}
7155 (@value{GDBP}) @b{while ($trace_frame != -1)}
7156 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
7157 $trace_frame, $pc, $sp, $fp
7161 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
7162 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
7163 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
7164 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
7165 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
7166 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
7167 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
7168 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
7169 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
7170 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
7171 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
7174 Or, if we want to examine the variable @code{X} at each source line in
7178 (@value{GDBP}) @b{tfind start}
7179 (@value{GDBP}) @b{while ($trace_frame != -1)}
7180 > printf "Frame %d, X == %d\n", $trace_frame, X
7190 @subsection @code{tdump}
7192 @cindex dump all data collected at tracepoint
7193 @cindex tracepoint data, display
7195 This command takes no arguments. It prints all the data collected at
7196 the current trace snapshot.
7199 (@value{GDBP}) @b{trace 444}
7200 (@value{GDBP}) @b{actions}
7201 Enter actions for tracepoint #2, one per line:
7202 > collect $regs, $locals, $args, gdb_long_test
7205 (@value{GDBP}) @b{tstart}
7207 (@value{GDBP}) @b{tfind line 444}
7208 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
7210 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
7212 (@value{GDBP}) @b{tdump}
7213 Data collected at tracepoint 2, trace frame 1:
7214 d0 0xc4aa0085 -995491707
7218 d4 0x71aea3d 119204413
7223 a1 0x3000668 50333288
7226 a4 0x3000698 50333336
7228 fp 0x30bf3c 0x30bf3c
7229 sp 0x30bf34 0x30bf34
7231 pc 0x20b2c8 0x20b2c8
7235 p = 0x20e5b4 "gdb-test"
7242 gdb_long_test = 17 '\021'
7247 @node save-tracepoints
7248 @subsection @code{save-tracepoints @var{filename}}
7249 @kindex save-tracepoints
7250 @cindex save tracepoints for future sessions
7252 This command saves all current tracepoint definitions together with
7253 their actions and passcounts, into a file @file{@var{filename}}
7254 suitable for use in a later debugging session. To read the saved
7255 tracepoint definitions, use the @code{source} command (@pxref{Command
7258 @node Tracepoint Variables
7259 @section Convenience Variables for Tracepoints
7260 @cindex tracepoint variables
7261 @cindex convenience variables for tracepoints
7264 @vindex $trace_frame
7265 @item (int) $trace_frame
7266 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
7267 snapshot is selected.
7270 @item (int) $tracepoint
7271 The tracepoint for the current trace snapshot.
7274 @item (int) $trace_line
7275 The line number for the current trace snapshot.
7278 @item (char []) $trace_file
7279 The source file for the current trace snapshot.
7282 @item (char []) $trace_func
7283 The name of the function containing @code{$tracepoint}.
7286 Note: @code{$trace_file} is not suitable for use in @code{printf},
7287 use @code{output} instead.
7289 Here's a simple example of using these convenience variables for
7290 stepping through all the trace snapshots and printing some of their
7294 (@value{GDBP}) @b{tfind start}
7296 (@value{GDBP}) @b{while $trace_frame != -1}
7297 > output $trace_file
7298 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
7304 @chapter Debugging Programs That Use Overlays
7307 If your program is too large to fit completely in your target system's
7308 memory, you can sometimes use @dfn{overlays} to work around this
7309 problem. @value{GDBN} provides some support for debugging programs that
7313 * How Overlays Work:: A general explanation of overlays.
7314 * Overlay Commands:: Managing overlays in @value{GDBN}.
7315 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
7316 mapped by asking the inferior.
7317 * Overlay Sample Program:: A sample program using overlays.
7320 @node How Overlays Work
7321 @section How Overlays Work
7322 @cindex mapped overlays
7323 @cindex unmapped overlays
7324 @cindex load address, overlay's
7325 @cindex mapped address
7326 @cindex overlay area
7328 Suppose you have a computer whose instruction address space is only 64
7329 kilobytes long, but which has much more memory which can be accessed by
7330 other means: special instructions, segment registers, or memory
7331 management hardware, for example. Suppose further that you want to
7332 adapt a program which is larger than 64 kilobytes to run on this system.
7334 One solution is to identify modules of your program which are relatively
7335 independent, and need not call each other directly; call these modules
7336 @dfn{overlays}. Separate the overlays from the main program, and place
7337 their machine code in the larger memory. Place your main program in
7338 instruction memory, but leave at least enough space there to hold the
7339 largest overlay as well.
7341 Now, to call a function located in an overlay, you must first copy that
7342 overlay's machine code from the large memory into the space set aside
7343 for it in the instruction memory, and then jump to its entry point
7346 @c NB: In the below the mapped area's size is greater or equal to the
7347 @c size of all overlays. This is intentional to remind the developer
7348 @c that overlays don't necessarily need to be the same size.
7352 Data Instruction Larger
7353 Address Space Address Space Address Space
7354 +-----------+ +-----------+ +-----------+
7356 +-----------+ +-----------+ +-----------+<-- overlay 1
7357 | program | | main | .----| overlay 1 | load address
7358 | variables | | program | | +-----------+
7359 | and heap | | | | | |
7360 +-----------+ | | | +-----------+<-- overlay 2
7361 | | +-----------+ | | | load address
7362 +-----------+ | | | .-| overlay 2 |
7364 mapped --->+-----------+ | | +-----------+
7366 | overlay | <-' | | |
7367 | area | <---' +-----------+<-- overlay 3
7368 | | <---. | | load address
7369 +-----------+ `--| overlay 3 |
7376 @anchor{A code overlay}A code overlay
7380 The diagram (@pxref{A code overlay}) shows a system with separate data
7381 and instruction address spaces. To map an overlay, the program copies
7382 its code from the larger address space to the instruction address space.
7383 Since the overlays shown here all use the same mapped address, only one
7384 may be mapped at a time. For a system with a single address space for
7385 data and instructions, the diagram would be similar, except that the
7386 program variables and heap would share an address space with the main
7387 program and the overlay area.
7389 An overlay loaded into instruction memory and ready for use is called a
7390 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
7391 instruction memory. An overlay not present (or only partially present)
7392 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
7393 is its address in the larger memory. The mapped address is also called
7394 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
7395 called the @dfn{load memory address}, or @dfn{LMA}.
7397 Unfortunately, overlays are not a completely transparent way to adapt a
7398 program to limited instruction memory. They introduce a new set of
7399 global constraints you must keep in mind as you design your program:
7404 Before calling or returning to a function in an overlay, your program
7405 must make sure that overlay is actually mapped. Otherwise, the call or
7406 return will transfer control to the right address, but in the wrong
7407 overlay, and your program will probably crash.
7410 If the process of mapping an overlay is expensive on your system, you
7411 will need to choose your overlays carefully to minimize their effect on
7412 your program's performance.
7415 The executable file you load onto your system must contain each
7416 overlay's instructions, appearing at the overlay's load address, not its
7417 mapped address. However, each overlay's instructions must be relocated
7418 and its symbols defined as if the overlay were at its mapped address.
7419 You can use GNU linker scripts to specify different load and relocation
7420 addresses for pieces of your program; see @ref{Overlay Description,,,
7421 ld.info, Using ld: the GNU linker}.
7424 The procedure for loading executable files onto your system must be able
7425 to load their contents into the larger address space as well as the
7426 instruction and data spaces.
7430 The overlay system described above is rather simple, and could be
7431 improved in many ways:
7436 If your system has suitable bank switch registers or memory management
7437 hardware, you could use those facilities to make an overlay's load area
7438 contents simply appear at their mapped address in instruction space.
7439 This would probably be faster than copying the overlay to its mapped
7440 area in the usual way.
7443 If your overlays are small enough, you could set aside more than one
7444 overlay area, and have more than one overlay mapped at a time.
7447 You can use overlays to manage data, as well as instructions. In
7448 general, data overlays are even less transparent to your design than
7449 code overlays: whereas code overlays only require care when you call or
7450 return to functions, data overlays require care every time you access
7451 the data. Also, if you change the contents of a data overlay, you
7452 must copy its contents back out to its load address before you can copy a
7453 different data overlay into the same mapped area.
7458 @node Overlay Commands
7459 @section Overlay Commands
7461 To use @value{GDBN}'s overlay support, each overlay in your program must
7462 correspond to a separate section of the executable file. The section's
7463 virtual memory address and load memory address must be the overlay's
7464 mapped and load addresses. Identifying overlays with sections allows
7465 @value{GDBN} to determine the appropriate address of a function or
7466 variable, depending on whether the overlay is mapped or not.
7468 @value{GDBN}'s overlay commands all start with the word @code{overlay};
7469 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
7474 Disable @value{GDBN}'s overlay support. When overlay support is
7475 disabled, @value{GDBN} assumes that all functions and variables are
7476 always present at their mapped addresses. By default, @value{GDBN}'s
7477 overlay support is disabled.
7479 @item overlay manual
7480 @cindex manual overlay debugging
7481 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
7482 relies on you to tell it which overlays are mapped, and which are not,
7483 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
7484 commands described below.
7486 @item overlay map-overlay @var{overlay}
7487 @itemx overlay map @var{overlay}
7488 @cindex map an overlay
7489 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
7490 be the name of the object file section containing the overlay. When an
7491 overlay is mapped, @value{GDBN} assumes it can find the overlay's
7492 functions and variables at their mapped addresses. @value{GDBN} assumes
7493 that any other overlays whose mapped ranges overlap that of
7494 @var{overlay} are now unmapped.
7496 @item overlay unmap-overlay @var{overlay}
7497 @itemx overlay unmap @var{overlay}
7498 @cindex unmap an overlay
7499 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
7500 must be the name of the object file section containing the overlay.
7501 When an overlay is unmapped, @value{GDBN} assumes it can find the
7502 overlay's functions and variables at their load addresses.
7505 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
7506 consults a data structure the overlay manager maintains in the inferior
7507 to see which overlays are mapped. For details, see @ref{Automatic
7510 @item overlay load-target
7512 @cindex reloading the overlay table
7513 Re-read the overlay table from the inferior. Normally, @value{GDBN}
7514 re-reads the table @value{GDBN} automatically each time the inferior
7515 stops, so this command should only be necessary if you have changed the
7516 overlay mapping yourself using @value{GDBN}. This command is only
7517 useful when using automatic overlay debugging.
7519 @item overlay list-overlays
7521 @cindex listing mapped overlays
7522 Display a list of the overlays currently mapped, along with their mapped
7523 addresses, load addresses, and sizes.
7527 Normally, when @value{GDBN} prints a code address, it includes the name
7528 of the function the address falls in:
7531 (@value{GDBP}) print main
7532 $3 = @{int ()@} 0x11a0 <main>
7535 When overlay debugging is enabled, @value{GDBN} recognizes code in
7536 unmapped overlays, and prints the names of unmapped functions with
7537 asterisks around them. For example, if @code{foo} is a function in an
7538 unmapped overlay, @value{GDBN} prints it this way:
7541 (@value{GDBP}) overlay list
7542 No sections are mapped.
7543 (@value{GDBP}) print foo
7544 $5 = @{int (int)@} 0x100000 <*foo*>
7547 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
7551 (@value{GDBP}) overlay list
7552 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
7553 mapped at 0x1016 - 0x104a
7554 (@value{GDBP}) print foo
7555 $6 = @{int (int)@} 0x1016 <foo>
7558 When overlay debugging is enabled, @value{GDBN} can find the correct
7559 address for functions and variables in an overlay, whether or not the
7560 overlay is mapped. This allows most @value{GDBN} commands, like
7561 @code{break} and @code{disassemble}, to work normally, even on unmapped
7562 code. However, @value{GDBN}'s breakpoint support has some limitations:
7566 @cindex breakpoints in overlays
7567 @cindex overlays, setting breakpoints in
7568 You can set breakpoints in functions in unmapped overlays, as long as
7569 @value{GDBN} can write to the overlay at its load address.
7571 @value{GDBN} can not set hardware or simulator-based breakpoints in
7572 unmapped overlays. However, if you set a breakpoint at the end of your
7573 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
7574 you are using manual overlay management), @value{GDBN} will re-set its
7575 breakpoints properly.
7579 @node Automatic Overlay Debugging
7580 @section Automatic Overlay Debugging
7581 @cindex automatic overlay debugging
7583 @value{GDBN} can automatically track which overlays are mapped and which
7584 are not, given some simple co-operation from the overlay manager in the
7585 inferior. If you enable automatic overlay debugging with the
7586 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
7587 looks in the inferior's memory for certain variables describing the
7588 current state of the overlays.
7590 Here are the variables your overlay manager must define to support
7591 @value{GDBN}'s automatic overlay debugging:
7595 @item @code{_ovly_table}:
7596 This variable must be an array of the following structures:
7601 /* The overlay's mapped address. */
7604 /* The size of the overlay, in bytes. */
7607 /* The overlay's load address. */
7610 /* Non-zero if the overlay is currently mapped;
7612 unsigned long mapped;
7616 @item @code{_novlys}:
7617 This variable must be a four-byte signed integer, holding the total
7618 number of elements in @code{_ovly_table}.
7622 To decide whether a particular overlay is mapped or not, @value{GDBN}
7623 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
7624 @code{lma} members equal the VMA and LMA of the overlay's section in the
7625 executable file. When @value{GDBN} finds a matching entry, it consults
7626 the entry's @code{mapped} member to determine whether the overlay is
7629 In addition, your overlay manager may define a function called
7630 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
7631 will silently set a breakpoint there. If the overlay manager then
7632 calls this function whenever it has changed the overlay table, this
7633 will enable @value{GDBN} to accurately keep track of which overlays
7634 are in program memory, and update any breakpoints that may be set
7635 in overlays. This will allow breakpoints to work even if the
7636 overlays are kept in ROM or other non-writable memory while they
7637 are not being executed.
7639 @node Overlay Sample Program
7640 @section Overlay Sample Program
7641 @cindex overlay example program
7643 When linking a program which uses overlays, you must place the overlays
7644 at their load addresses, while relocating them to run at their mapped
7645 addresses. To do this, you must write a linker script (@pxref{Overlay
7646 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
7647 since linker scripts are specific to a particular host system, target
7648 architecture, and target memory layout, this manual cannot provide
7649 portable sample code demonstrating @value{GDBN}'s overlay support.
7651 However, the @value{GDBN} source distribution does contain an overlaid
7652 program, with linker scripts for a few systems, as part of its test
7653 suite. The program consists of the following files from
7654 @file{gdb/testsuite/gdb.base}:
7658 The main program file.
7660 A simple overlay manager, used by @file{overlays.c}.
7665 Overlay modules, loaded and used by @file{overlays.c}.
7668 Linker scripts for linking the test program on the @code{d10v-elf}
7669 and @code{m32r-elf} targets.
7672 You can build the test program using the @code{d10v-elf} GCC
7673 cross-compiler like this:
7676 $ d10v-elf-gcc -g -c overlays.c
7677 $ d10v-elf-gcc -g -c ovlymgr.c
7678 $ d10v-elf-gcc -g -c foo.c
7679 $ d10v-elf-gcc -g -c bar.c
7680 $ d10v-elf-gcc -g -c baz.c
7681 $ d10v-elf-gcc -g -c grbx.c
7682 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
7683 baz.o grbx.o -Wl,-Td10v.ld -o overlays
7686 The build process is identical for any other architecture, except that
7687 you must substitute the appropriate compiler and linker script for the
7688 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
7692 @chapter Using @value{GDBN} with Different Languages
7695 Although programming languages generally have common aspects, they are
7696 rarely expressed in the same manner. For instance, in ANSI C,
7697 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
7698 Modula-2, it is accomplished by @code{p^}. Values can also be
7699 represented (and displayed) differently. Hex numbers in C appear as
7700 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
7702 @cindex working language
7703 Language-specific information is built into @value{GDBN} for some languages,
7704 allowing you to express operations like the above in your program's
7705 native language, and allowing @value{GDBN} to output values in a manner
7706 consistent with the syntax of your program's native language. The
7707 language you use to build expressions is called the @dfn{working
7711 * Setting:: Switching between source languages
7712 * Show:: Displaying the language
7713 * Checks:: Type and range checks
7714 * Support:: Supported languages
7715 * Unsupported languages:: Unsupported languages
7719 @section Switching between source languages
7721 There are two ways to control the working language---either have @value{GDBN}
7722 set it automatically, or select it manually yourself. You can use the
7723 @code{set language} command for either purpose. On startup, @value{GDBN}
7724 defaults to setting the language automatically. The working language is
7725 used to determine how expressions you type are interpreted, how values
7728 In addition to the working language, every source file that
7729 @value{GDBN} knows about has its own working language. For some object
7730 file formats, the compiler might indicate which language a particular
7731 source file is in. However, most of the time @value{GDBN} infers the
7732 language from the name of the file. The language of a source file
7733 controls whether C@t{++} names are demangled---this way @code{backtrace} can
7734 show each frame appropriately for its own language. There is no way to
7735 set the language of a source file from within @value{GDBN}, but you can
7736 set the language associated with a filename extension. @xref{Show, ,
7737 Displaying the language}.
7739 This is most commonly a problem when you use a program, such
7740 as @code{cfront} or @code{f2c}, that generates C but is written in
7741 another language. In that case, make the
7742 program use @code{#line} directives in its C output; that way
7743 @value{GDBN} will know the correct language of the source code of the original
7744 program, and will display that source code, not the generated C code.
7747 * Filenames:: Filename extensions and languages.
7748 * Manually:: Setting the working language manually
7749 * Automatically:: Having @value{GDBN} infer the source language
7753 @subsection List of filename extensions and languages
7755 If a source file name ends in one of the following extensions, then
7756 @value{GDBN} infers that its language is the one indicated.
7777 Objective-C source file
7784 Modula-2 source file
7788 Assembler source file. This actually behaves almost like C, but
7789 @value{GDBN} does not skip over function prologues when stepping.
7792 In addition, you may set the language associated with a filename
7793 extension. @xref{Show, , Displaying the language}.
7796 @subsection Setting the working language
7798 If you allow @value{GDBN} to set the language automatically,
7799 expressions are interpreted the same way in your debugging session and
7802 @kindex set language
7803 If you wish, you may set the language manually. To do this, issue the
7804 command @samp{set language @var{lang}}, where @var{lang} is the name of
7806 @code{c} or @code{modula-2}.
7807 For a list of the supported languages, type @samp{set language}.
7809 Setting the language manually prevents @value{GDBN} from updating the working
7810 language automatically. This can lead to confusion if you try
7811 to debug a program when the working language is not the same as the
7812 source language, when an expression is acceptable to both
7813 languages---but means different things. For instance, if the current
7814 source file were written in C, and @value{GDBN} was parsing Modula-2, a
7822 might not have the effect you intended. In C, this means to add
7823 @code{b} and @code{c} and place the result in @code{a}. The result
7824 printed would be the value of @code{a}. In Modula-2, this means to compare
7825 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
7828 @subsection Having @value{GDBN} infer the source language
7830 To have @value{GDBN} set the working language automatically, use
7831 @samp{set language local} or @samp{set language auto}. @value{GDBN}
7832 then infers the working language. That is, when your program stops in a
7833 frame (usually by encountering a breakpoint), @value{GDBN} sets the
7834 working language to the language recorded for the function in that
7835 frame. If the language for a frame is unknown (that is, if the function
7836 or block corresponding to the frame was defined in a source file that
7837 does not have a recognized extension), the current working language is
7838 not changed, and @value{GDBN} issues a warning.
7840 This may not seem necessary for most programs, which are written
7841 entirely in one source language. However, program modules and libraries
7842 written in one source language can be used by a main program written in
7843 a different source language. Using @samp{set language auto} in this
7844 case frees you from having to set the working language manually.
7847 @section Displaying the language
7849 The following commands help you find out which language is the
7850 working language, and also what language source files were written in.
7852 @kindex show language
7855 Display the current working language. This is the
7856 language you can use with commands such as @code{print} to
7857 build and compute expressions that may involve variables in your program.
7860 @kindex info frame@r{, show the source language}
7861 Display the source language for this frame. This language becomes the
7862 working language if you use an identifier from this frame.
7863 @xref{Frame Info, ,Information about a frame}, to identify the other
7864 information listed here.
7867 @kindex info source@r{, show the source language}
7868 Display the source language of this source file.
7869 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
7870 information listed here.
7873 In unusual circumstances, you may have source files with extensions
7874 not in the standard list. You can then set the extension associated
7875 with a language explicitly:
7877 @kindex set extension-language
7878 @kindex info extensions
7880 @item set extension-language @var{.ext} @var{language}
7881 Set source files with extension @var{.ext} to be assumed to be in
7882 the source language @var{language}.
7884 @item info extensions
7885 List all the filename extensions and the associated languages.
7889 @section Type and range checking
7892 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
7893 checking are included, but they do not yet have any effect. This
7894 section documents the intended facilities.
7896 @c FIXME remove warning when type/range code added
7898 Some languages are designed to guard you against making seemingly common
7899 errors through a series of compile- and run-time checks. These include
7900 checking the type of arguments to functions and operators, and making
7901 sure mathematical overflows are caught at run time. Checks such as
7902 these help to ensure a program's correctness once it has been compiled
7903 by eliminating type mismatches, and providing active checks for range
7904 errors when your program is running.
7906 @value{GDBN} can check for conditions like the above if you wish.
7907 Although @value{GDBN} does not check the statements in your program, it
7908 can check expressions entered directly into @value{GDBN} for evaluation via
7909 the @code{print} command, for example. As with the working language,
7910 @value{GDBN} can also decide whether or not to check automatically based on
7911 your program's source language. @xref{Support, ,Supported languages},
7912 for the default settings of supported languages.
7915 * Type Checking:: An overview of type checking
7916 * Range Checking:: An overview of range checking
7919 @cindex type checking
7920 @cindex checks, type
7922 @subsection An overview of type checking
7924 Some languages, such as Modula-2, are strongly typed, meaning that the
7925 arguments to operators and functions have to be of the correct type,
7926 otherwise an error occurs. These checks prevent type mismatch
7927 errors from ever causing any run-time problems. For example,
7935 The second example fails because the @code{CARDINAL} 1 is not
7936 type-compatible with the @code{REAL} 2.3.
7938 For the expressions you use in @value{GDBN} commands, you can tell the
7939 @value{GDBN} type checker to skip checking;
7940 to treat any mismatches as errors and abandon the expression;
7941 or to only issue warnings when type mismatches occur,
7942 but evaluate the expression anyway. When you choose the last of
7943 these, @value{GDBN} evaluates expressions like the second example above, but
7944 also issues a warning.
7946 Even if you turn type checking off, there may be other reasons
7947 related to type that prevent @value{GDBN} from evaluating an expression.
7948 For instance, @value{GDBN} does not know how to add an @code{int} and
7949 a @code{struct foo}. These particular type errors have nothing to do
7950 with the language in use, and usually arise from expressions, such as
7951 the one described above, which make little sense to evaluate anyway.
7953 Each language defines to what degree it is strict about type. For
7954 instance, both Modula-2 and C require the arguments to arithmetical
7955 operators to be numbers. In C, enumerated types and pointers can be
7956 represented as numbers, so that they are valid arguments to mathematical
7957 operators. @xref{Support, ,Supported languages}, for further
7958 details on specific languages.
7960 @value{GDBN} provides some additional commands for controlling the type checker:
7962 @kindex set check type
7963 @kindex show check type
7965 @item set check type auto
7966 Set type checking on or off based on the current working language.
7967 @xref{Support, ,Supported languages}, for the default settings for
7970 @item set check type on
7971 @itemx set check type off
7972 Set type checking on or off, overriding the default setting for the
7973 current working language. Issue a warning if the setting does not
7974 match the language default. If any type mismatches occur in
7975 evaluating an expression while type checking is on, @value{GDBN} prints a
7976 message and aborts evaluation of the expression.
7978 @item set check type warn
7979 Cause the type checker to issue warnings, but to always attempt to
7980 evaluate the expression. Evaluating the expression may still
7981 be impossible for other reasons. For example, @value{GDBN} cannot add
7982 numbers and structures.
7985 Show the current setting of the type checker, and whether or not @value{GDBN}
7986 is setting it automatically.
7989 @cindex range checking
7990 @cindex checks, range
7991 @node Range Checking
7992 @subsection An overview of range checking
7994 In some languages (such as Modula-2), it is an error to exceed the
7995 bounds of a type; this is enforced with run-time checks. Such range
7996 checking is meant to ensure program correctness by making sure
7997 computations do not overflow, or indices on an array element access do
7998 not exceed the bounds of the array.
8000 For expressions you use in @value{GDBN} commands, you can tell
8001 @value{GDBN} to treat range errors in one of three ways: ignore them,
8002 always treat them as errors and abandon the expression, or issue
8003 warnings but evaluate the expression anyway.
8005 A range error can result from numerical overflow, from exceeding an
8006 array index bound, or when you type a constant that is not a member
8007 of any type. Some languages, however, do not treat overflows as an
8008 error. In many implementations of C, mathematical overflow causes the
8009 result to ``wrap around'' to lower values---for example, if @var{m} is
8010 the largest integer value, and @var{s} is the smallest, then
8013 @var{m} + 1 @result{} @var{s}
8016 This, too, is specific to individual languages, and in some cases
8017 specific to individual compilers or machines. @xref{Support, ,
8018 Supported languages}, for further details on specific languages.
8020 @value{GDBN} provides some additional commands for controlling the range checker:
8022 @kindex set check range
8023 @kindex show check range
8025 @item set check range auto
8026 Set range checking on or off based on the current working language.
8027 @xref{Support, ,Supported languages}, for the default settings for
8030 @item set check range on
8031 @itemx set check range off
8032 Set range checking on or off, overriding the default setting for the
8033 current working language. A warning is issued if the setting does not
8034 match the language default. If a range error occurs and range checking is on,
8035 then a message is printed and evaluation of the expression is aborted.
8037 @item set check range warn
8038 Output messages when the @value{GDBN} range checker detects a range error,
8039 but attempt to evaluate the expression anyway. Evaluating the
8040 expression may still be impossible for other reasons, such as accessing
8041 memory that the process does not own (a typical example from many Unix
8045 Show the current setting of the range checker, and whether or not it is
8046 being set automatically by @value{GDBN}.
8050 @section Supported languages
8052 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, assembly, Modula-2, and Ada.
8053 @c This is false ...
8054 Some @value{GDBN} features may be used in expressions regardless of the
8055 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
8056 and the @samp{@{type@}addr} construct (@pxref{Expressions,
8057 ,Expressions}) can be used with the constructs of any supported
8060 The following sections detail to what degree each source language is
8061 supported by @value{GDBN}. These sections are not meant to be language
8062 tutorials or references, but serve only as a reference guide to what the
8063 @value{GDBN} expression parser accepts, and what input and output
8064 formats should look like for different languages. There are many good
8065 books written on each of these languages; please look to these for a
8066 language reference or tutorial.
8070 * Objective-C:: Objective-C
8071 * Modula-2:: Modula-2
8076 @subsection C and C@t{++}
8078 @cindex C and C@t{++}
8079 @cindex expressions in C or C@t{++}
8081 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
8082 to both languages. Whenever this is the case, we discuss those languages
8086 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
8087 @cindex @sc{gnu} C@t{++}
8088 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
8089 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
8090 effectively, you must compile your C@t{++} programs with a supported
8091 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
8092 compiler (@code{aCC}).
8094 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
8095 format; if it doesn't work on your system, try the stabs+ debugging
8096 format. You can select those formats explicitly with the @code{g++}
8097 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
8098 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
8099 CC, gcc.info, Using @sc{gnu} CC}.
8102 * C Operators:: C and C@t{++} operators
8103 * C Constants:: C and C@t{++} constants
8104 * C plus plus expressions:: C@t{++} expressions
8105 * C Defaults:: Default settings for C and C@t{++}
8106 * C Checks:: C and C@t{++} type and range checks
8107 * Debugging C:: @value{GDBN} and C
8108 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
8112 @subsubsection C and C@t{++} operators
8114 @cindex C and C@t{++} operators
8116 Operators must be defined on values of specific types. For instance,
8117 @code{+} is defined on numbers, but not on structures. Operators are
8118 often defined on groups of types.
8120 For the purposes of C and C@t{++}, the following definitions hold:
8125 @emph{Integral types} include @code{int} with any of its storage-class
8126 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
8129 @emph{Floating-point types} include @code{float}, @code{double}, and
8130 @code{long double} (if supported by the target platform).
8133 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
8136 @emph{Scalar types} include all of the above.
8141 The following operators are supported. They are listed here
8142 in order of increasing precedence:
8146 The comma or sequencing operator. Expressions in a comma-separated list
8147 are evaluated from left to right, with the result of the entire
8148 expression being the last expression evaluated.
8151 Assignment. The value of an assignment expression is the value
8152 assigned. Defined on scalar types.
8155 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
8156 and translated to @w{@code{@var{a} = @var{a op b}}}.
8157 @w{@code{@var{op}=}} and @code{=} have the same precedence.
8158 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
8159 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
8162 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
8163 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
8167 Logical @sc{or}. Defined on integral types.
8170 Logical @sc{and}. Defined on integral types.
8173 Bitwise @sc{or}. Defined on integral types.
8176 Bitwise exclusive-@sc{or}. Defined on integral types.
8179 Bitwise @sc{and}. Defined on integral types.
8182 Equality and inequality. Defined on scalar types. The value of these
8183 expressions is 0 for false and non-zero for true.
8185 @item <@r{, }>@r{, }<=@r{, }>=
8186 Less than, greater than, less than or equal, greater than or equal.
8187 Defined on scalar types. The value of these expressions is 0 for false
8188 and non-zero for true.
8191 left shift, and right shift. Defined on integral types.
8194 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8197 Addition and subtraction. Defined on integral types, floating-point types and
8200 @item *@r{, }/@r{, }%
8201 Multiplication, division, and modulus. Multiplication and division are
8202 defined on integral and floating-point types. Modulus is defined on
8206 Increment and decrement. When appearing before a variable, the
8207 operation is performed before the variable is used in an expression;
8208 when appearing after it, the variable's value is used before the
8209 operation takes place.
8212 Pointer dereferencing. Defined on pointer types. Same precedence as
8216 Address operator. Defined on variables. Same precedence as @code{++}.
8218 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
8219 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
8220 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
8221 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
8225 Negative. Defined on integral and floating-point types. Same
8226 precedence as @code{++}.
8229 Logical negation. Defined on integral types. Same precedence as
8233 Bitwise complement operator. Defined on integral types. Same precedence as
8238 Structure member, and pointer-to-structure member. For convenience,
8239 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
8240 pointer based on the stored type information.
8241 Defined on @code{struct} and @code{union} data.
8244 Dereferences of pointers to members.
8247 Array indexing. @code{@var{a}[@var{i}]} is defined as
8248 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
8251 Function parameter list. Same precedence as @code{->}.
8254 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
8255 and @code{class} types.
8258 Doubled colons also represent the @value{GDBN} scope operator
8259 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
8263 If an operator is redefined in the user code, @value{GDBN} usually
8264 attempts to invoke the redefined version instead of using the operator's
8272 @subsubsection C and C@t{++} constants
8274 @cindex C and C@t{++} constants
8276 @value{GDBN} allows you to express the constants of C and C@t{++} in the
8281 Integer constants are a sequence of digits. Octal constants are
8282 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
8283 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
8284 @samp{l}, specifying that the constant should be treated as a
8288 Floating point constants are a sequence of digits, followed by a decimal
8289 point, followed by a sequence of digits, and optionally followed by an
8290 exponent. An exponent is of the form:
8291 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
8292 sequence of digits. The @samp{+} is optional for positive exponents.
8293 A floating-point constant may also end with a letter @samp{f} or
8294 @samp{F}, specifying that the constant should be treated as being of
8295 the @code{float} (as opposed to the default @code{double}) type; or with
8296 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
8300 Enumerated constants consist of enumerated identifiers, or their
8301 integral equivalents.
8304 Character constants are a single character surrounded by single quotes
8305 (@code{'}), or a number---the ordinal value of the corresponding character
8306 (usually its @sc{ascii} value). Within quotes, the single character may
8307 be represented by a letter or by @dfn{escape sequences}, which are of
8308 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
8309 of the character's ordinal value; or of the form @samp{\@var{x}}, where
8310 @samp{@var{x}} is a predefined special character---for example,
8311 @samp{\n} for newline.
8314 String constants are a sequence of character constants surrounded by
8315 double quotes (@code{"}). Any valid character constant (as described
8316 above) may appear. Double quotes within the string must be preceded by
8317 a backslash, so for instance @samp{"a\"b'c"} is a string of five
8321 Pointer constants are an integral value. You can also write pointers
8322 to constants using the C operator @samp{&}.
8325 Array constants are comma-separated lists surrounded by braces @samp{@{}
8326 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
8327 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
8328 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
8332 * C plus plus expressions::
8339 @node C plus plus expressions
8340 @subsubsection C@t{++} expressions
8342 @cindex expressions in C@t{++}
8343 @value{GDBN} expression handling can interpret most C@t{++} expressions.
8345 @cindex debugging C@t{++} programs
8346 @cindex C@t{++} compilers
8347 @cindex debug formats and C@t{++}
8348 @cindex @value{NGCC} and C@t{++}
8350 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
8351 proper compiler and the proper debug format. Currently, @value{GDBN}
8352 works best when debugging C@t{++} code that is compiled with
8353 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
8354 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
8355 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
8356 stabs+ as their default debug format, so you usually don't need to
8357 specify a debug format explicitly. Other compilers and/or debug formats
8358 are likely to work badly or not at all when using @value{GDBN} to debug
8364 @cindex member functions
8366 Member function calls are allowed; you can use expressions like
8369 count = aml->GetOriginal(x, y)
8372 @vindex this@r{, inside C@t{++} member functions}
8373 @cindex namespace in C@t{++}
8375 While a member function is active (in the selected stack frame), your
8376 expressions have the same namespace available as the member function;
8377 that is, @value{GDBN} allows implicit references to the class instance
8378 pointer @code{this} following the same rules as C@t{++}.
8380 @cindex call overloaded functions
8381 @cindex overloaded functions, calling
8382 @cindex type conversions in C@t{++}
8384 You can call overloaded functions; @value{GDBN} resolves the function
8385 call to the right definition, with some restrictions. @value{GDBN} does not
8386 perform overload resolution involving user-defined type conversions,
8387 calls to constructors, or instantiations of templates that do not exist
8388 in the program. It also cannot handle ellipsis argument lists or
8391 It does perform integral conversions and promotions, floating-point
8392 promotions, arithmetic conversions, pointer conversions, conversions of
8393 class objects to base classes, and standard conversions such as those of
8394 functions or arrays to pointers; it requires an exact match on the
8395 number of function arguments.
8397 Overload resolution is always performed, unless you have specified
8398 @code{set overload-resolution off}. @xref{Debugging C plus plus,
8399 ,@value{GDBN} features for C@t{++}}.
8401 You must specify @code{set overload-resolution off} in order to use an
8402 explicit function signature to call an overloaded function, as in
8404 p 'foo(char,int)'('x', 13)
8407 The @value{GDBN} command-completion facility can simplify this;
8408 see @ref{Completion, ,Command completion}.
8410 @cindex reference declarations
8412 @value{GDBN} understands variables declared as C@t{++} references; you can use
8413 them in expressions just as you do in C@t{++} source---they are automatically
8416 In the parameter list shown when @value{GDBN} displays a frame, the values of
8417 reference variables are not displayed (unlike other variables); this
8418 avoids clutter, since references are often used for large structures.
8419 The @emph{address} of a reference variable is always shown, unless
8420 you have specified @samp{set print address off}.
8423 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
8424 expressions can use it just as expressions in your program do. Since
8425 one scope may be defined in another, you can use @code{::} repeatedly if
8426 necessary, for example in an expression like
8427 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
8428 resolving name scope by reference to source files, in both C and C@t{++}
8429 debugging (@pxref{Variables, ,Program variables}).
8432 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
8433 calling virtual functions correctly, printing out virtual bases of
8434 objects, calling functions in a base subobject, casting objects, and
8435 invoking user-defined operators.
8438 @subsubsection C and C@t{++} defaults
8440 @cindex C and C@t{++} defaults
8442 If you allow @value{GDBN} to set type and range checking automatically, they
8443 both default to @code{off} whenever the working language changes to
8444 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
8445 selects the working language.
8447 If you allow @value{GDBN} to set the language automatically, it
8448 recognizes source files whose names end with @file{.c}, @file{.C}, or
8449 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
8450 these files, it sets the working language to C or C@t{++}.
8451 @xref{Automatically, ,Having @value{GDBN} infer the source language},
8452 for further details.
8454 @c Type checking is (a) primarily motivated by Modula-2, and (b)
8455 @c unimplemented. If (b) changes, it might make sense to let this node
8456 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
8459 @subsubsection C and C@t{++} type and range checks
8461 @cindex C and C@t{++} checks
8463 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
8464 is not used. However, if you turn type checking on, @value{GDBN}
8465 considers two variables type equivalent if:
8469 The two variables are structured and have the same structure, union, or
8473 The two variables have the same type name, or types that have been
8474 declared equivalent through @code{typedef}.
8477 @c leaving this out because neither J Gilmore nor R Pesch understand it.
8480 The two @code{struct}, @code{union}, or @code{enum} variables are
8481 declared in the same declaration. (Note: this may not be true for all C
8486 Range checking, if turned on, is done on mathematical operations. Array
8487 indices are not checked, since they are often used to index a pointer
8488 that is not itself an array.
8491 @subsubsection @value{GDBN} and C
8493 The @code{set print union} and @code{show print union} commands apply to
8494 the @code{union} type. When set to @samp{on}, any @code{union} that is
8495 inside a @code{struct} or @code{class} is also printed. Otherwise, it
8496 appears as @samp{@{...@}}.
8498 The @code{@@} operator aids in the debugging of dynamic arrays, formed
8499 with pointers and a memory allocation function. @xref{Expressions,
8503 * Debugging C plus plus::
8506 @node Debugging C plus plus
8507 @subsubsection @value{GDBN} features for C@t{++}
8509 @cindex commands for C@t{++}
8511 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
8512 designed specifically for use with C@t{++}. Here is a summary:
8515 @cindex break in overloaded functions
8516 @item @r{breakpoint menus}
8517 When you want a breakpoint in a function whose name is overloaded,
8518 @value{GDBN} breakpoint menus help you specify which function definition
8519 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
8521 @cindex overloading in C@t{++}
8522 @item rbreak @var{regex}
8523 Setting breakpoints using regular expressions is helpful for setting
8524 breakpoints on overloaded functions that are not members of any special
8526 @xref{Set Breaks, ,Setting breakpoints}.
8528 @cindex C@t{++} exception handling
8531 Debug C@t{++} exception handling using these commands. @xref{Set
8532 Catchpoints, , Setting catchpoints}.
8535 @item ptype @var{typename}
8536 Print inheritance relationships as well as other information for type
8538 @xref{Symbols, ,Examining the Symbol Table}.
8540 @cindex C@t{++} symbol display
8541 @item set print demangle
8542 @itemx show print demangle
8543 @itemx set print asm-demangle
8544 @itemx show print asm-demangle
8545 Control whether C@t{++} symbols display in their source form, both when
8546 displaying code as C@t{++} source and when displaying disassemblies.
8547 @xref{Print Settings, ,Print settings}.
8549 @item set print object
8550 @itemx show print object
8551 Choose whether to print derived (actual) or declared types of objects.
8552 @xref{Print Settings, ,Print settings}.
8554 @item set print vtbl
8555 @itemx show print vtbl
8556 Control the format for printing virtual function tables.
8557 @xref{Print Settings, ,Print settings}.
8558 (The @code{vtbl} commands do not work on programs compiled with the HP
8559 ANSI C@t{++} compiler (@code{aCC}).)
8561 @kindex set overload-resolution
8562 @cindex overloaded functions, overload resolution
8563 @item set overload-resolution on
8564 Enable overload resolution for C@t{++} expression evaluation. The default
8565 is on. For overloaded functions, @value{GDBN} evaluates the arguments
8566 and searches for a function whose signature matches the argument types,
8567 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
8568 expressions}, for details). If it cannot find a match, it emits a
8571 @item set overload-resolution off
8572 Disable overload resolution for C@t{++} expression evaluation. For
8573 overloaded functions that are not class member functions, @value{GDBN}
8574 chooses the first function of the specified name that it finds in the
8575 symbol table, whether or not its arguments are of the correct type. For
8576 overloaded functions that are class member functions, @value{GDBN}
8577 searches for a function whose signature @emph{exactly} matches the
8580 @item @r{Overloaded symbol names}
8581 You can specify a particular definition of an overloaded symbol, using
8582 the same notation that is used to declare such symbols in C@t{++}: type
8583 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
8584 also use the @value{GDBN} command-line word completion facilities to list the
8585 available choices, or to finish the type list for you.
8586 @xref{Completion,, Command completion}, for details on how to do this.
8590 @subsection Objective-C
8593 This section provides information about some commands and command
8594 options that are useful for debugging Objective-C code.
8597 * Method Names in Commands::
8598 * The Print Command with Objective-C::
8601 @node Method Names in Commands, The Print Command with Objective-C, Objective-C, Objective-C
8602 @subsubsection Method Names in Commands
8604 The following commands have been extended to accept Objective-C method
8605 names as line specifications:
8607 @kindex clear@r{, and Objective-C}
8608 @kindex break@r{, and Objective-C}
8609 @kindex info line@r{, and Objective-C}
8610 @kindex jump@r{, and Objective-C}
8611 @kindex list@r{, and Objective-C}
8615 @item @code{info line}
8620 A fully qualified Objective-C method name is specified as
8623 -[@var{Class} @var{methodName}]
8626 where the minus sign is used to indicate an instance method and a
8627 plus sign (not shown) is used to indicate a class method. The class
8628 name @var{Class} and method name @var{methodName} are enclosed in
8629 brackets, similar to the way messages are specified in Objective-C
8630 source code. For example, to set a breakpoint at the @code{create}
8631 instance method of class @code{Fruit} in the program currently being
8635 break -[Fruit create]
8638 To list ten program lines around the @code{initialize} class method,
8642 list +[NSText initialize]
8645 In the current version of @value{GDBN}, the plus or minus sign is
8646 required. In future versions of @value{GDBN}, the plus or minus
8647 sign will be optional, but you can use it to narrow the search. It
8648 is also possible to specify just a method name:
8654 You must specify the complete method name, including any colons. If
8655 your program's source files contain more than one @code{create} method,
8656 you'll be presented with a numbered list of classes that implement that
8657 method. Indicate your choice by number, or type @samp{0} to exit if
8660 As another example, to clear a breakpoint established at the
8661 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
8664 clear -[NSWindow makeKeyAndOrderFront:]
8667 @node The Print Command with Objective-C
8668 @subsubsection The Print Command With Objective-C
8669 @kindex print-object
8670 @kindex po @r{(@code{print-object})}
8672 The print command has also been extended to accept methods. For example:
8675 print -[@var{object} hash]
8678 @cindex print an Objective-C object description
8679 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
8681 will tell @value{GDBN} to send the @code{hash} message to @var{object}
8682 and print the result. Also, an additional command has been added,
8683 @code{print-object} or @code{po} for short, which is meant to print
8684 the description of an object. However, this command may only work
8685 with certain Objective-C libraries that have a particular hook
8686 function, @code{_NSPrintForDebugger}, defined.
8688 @node Modula-2, Ada, Objective-C, Support
8689 @subsection Modula-2
8691 @cindex Modula-2, @value{GDBN} support
8693 The extensions made to @value{GDBN} to support Modula-2 only support
8694 output from the @sc{gnu} Modula-2 compiler (which is currently being
8695 developed). Other Modula-2 compilers are not currently supported, and
8696 attempting to debug executables produced by them is most likely
8697 to give an error as @value{GDBN} reads in the executable's symbol
8700 @cindex expressions in Modula-2
8702 * M2 Operators:: Built-in operators
8703 * Built-In Func/Proc:: Built-in functions and procedures
8704 * M2 Constants:: Modula-2 constants
8705 * M2 Defaults:: Default settings for Modula-2
8706 * Deviations:: Deviations from standard Modula-2
8707 * M2 Checks:: Modula-2 type and range checks
8708 * M2 Scope:: The scope operators @code{::} and @code{.}
8709 * GDB/M2:: @value{GDBN} and Modula-2
8713 @subsubsection Operators
8714 @cindex Modula-2 operators
8716 Operators must be defined on values of specific types. For instance,
8717 @code{+} is defined on numbers, but not on structures. Operators are
8718 often defined on groups of types. For the purposes of Modula-2, the
8719 following definitions hold:
8724 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
8728 @emph{Character types} consist of @code{CHAR} and its subranges.
8731 @emph{Floating-point types} consist of @code{REAL}.
8734 @emph{Pointer types} consist of anything declared as @code{POINTER TO
8738 @emph{Scalar types} consist of all of the above.
8741 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
8744 @emph{Boolean types} consist of @code{BOOLEAN}.
8748 The following operators are supported, and appear in order of
8749 increasing precedence:
8753 Function argument or array index separator.
8756 Assignment. The value of @var{var} @code{:=} @var{value} is
8760 Less than, greater than on integral, floating-point, or enumerated
8764 Less than or equal to, greater than or equal to
8765 on integral, floating-point and enumerated types, or set inclusion on
8766 set types. Same precedence as @code{<}.
8768 @item =@r{, }<>@r{, }#
8769 Equality and two ways of expressing inequality, valid on scalar types.
8770 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
8771 available for inequality, since @code{#} conflicts with the script
8775 Set membership. Defined on set types and the types of their members.
8776 Same precedence as @code{<}.
8779 Boolean disjunction. Defined on boolean types.
8782 Boolean conjunction. Defined on boolean types.
8785 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8788 Addition and subtraction on integral and floating-point types, or union
8789 and difference on set types.
8792 Multiplication on integral and floating-point types, or set intersection
8796 Division on floating-point types, or symmetric set difference on set
8797 types. Same precedence as @code{*}.
8800 Integer division and remainder. Defined on integral types. Same
8801 precedence as @code{*}.
8804 Negative. Defined on @code{INTEGER} and @code{REAL} data.
8807 Pointer dereferencing. Defined on pointer types.
8810 Boolean negation. Defined on boolean types. Same precedence as
8814 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
8815 precedence as @code{^}.
8818 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
8821 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
8825 @value{GDBN} and Modula-2 scope operators.
8829 @emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
8830 treats the use of the operator @code{IN}, or the use of operators
8831 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
8832 @code{<=}, and @code{>=} on sets as an error.
8836 @node Built-In Func/Proc
8837 @subsubsection Built-in functions and procedures
8838 @cindex Modula-2 built-ins
8840 Modula-2 also makes available several built-in procedures and functions.
8841 In describing these, the following metavariables are used:
8846 represents an @code{ARRAY} variable.
8849 represents a @code{CHAR} constant or variable.
8852 represents a variable or constant of integral type.
8855 represents an identifier that belongs to a set. Generally used in the
8856 same function with the metavariable @var{s}. The type of @var{s} should
8857 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
8860 represents a variable or constant of integral or floating-point type.
8863 represents a variable or constant of floating-point type.
8869 represents a variable.
8872 represents a variable or constant of one of many types. See the
8873 explanation of the function for details.
8876 All Modula-2 built-in procedures also return a result, described below.
8880 Returns the absolute value of @var{n}.
8883 If @var{c} is a lower case letter, it returns its upper case
8884 equivalent, otherwise it returns its argument.
8887 Returns the character whose ordinal value is @var{i}.
8890 Decrements the value in the variable @var{v} by one. Returns the new value.
8892 @item DEC(@var{v},@var{i})
8893 Decrements the value in the variable @var{v} by @var{i}. Returns the
8896 @item EXCL(@var{m},@var{s})
8897 Removes the element @var{m} from the set @var{s}. Returns the new
8900 @item FLOAT(@var{i})
8901 Returns the floating point equivalent of the integer @var{i}.
8904 Returns the index of the last member of @var{a}.
8907 Increments the value in the variable @var{v} by one. Returns the new value.
8909 @item INC(@var{v},@var{i})
8910 Increments the value in the variable @var{v} by @var{i}. Returns the
8913 @item INCL(@var{m},@var{s})
8914 Adds the element @var{m} to the set @var{s} if it is not already
8915 there. Returns the new set.
8918 Returns the maximum value of the type @var{t}.
8921 Returns the minimum value of the type @var{t}.
8924 Returns boolean TRUE if @var{i} is an odd number.
8927 Returns the ordinal value of its argument. For example, the ordinal
8928 value of a character is its @sc{ascii} value (on machines supporting the
8929 @sc{ascii} character set). @var{x} must be of an ordered type, which include
8930 integral, character and enumerated types.
8933 Returns the size of its argument. @var{x} can be a variable or a type.
8935 @item TRUNC(@var{r})
8936 Returns the integral part of @var{r}.
8938 @item VAL(@var{t},@var{i})
8939 Returns the member of the type @var{t} whose ordinal value is @var{i}.
8943 @emph{Warning:} Sets and their operations are not yet supported, so
8944 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
8948 @cindex Modula-2 constants
8950 @subsubsection Constants
8952 @value{GDBN} allows you to express the constants of Modula-2 in the following
8958 Integer constants are simply a sequence of digits. When used in an
8959 expression, a constant is interpreted to be type-compatible with the
8960 rest of the expression. Hexadecimal integers are specified by a
8961 trailing @samp{H}, and octal integers by a trailing @samp{B}.
8964 Floating point constants appear as a sequence of digits, followed by a
8965 decimal point and another sequence of digits. An optional exponent can
8966 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
8967 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
8968 digits of the floating point constant must be valid decimal (base 10)
8972 Character constants consist of a single character enclosed by a pair of
8973 like quotes, either single (@code{'}) or double (@code{"}). They may
8974 also be expressed by their ordinal value (their @sc{ascii} value, usually)
8975 followed by a @samp{C}.
8978 String constants consist of a sequence of characters enclosed by a
8979 pair of like quotes, either single (@code{'}) or double (@code{"}).
8980 Escape sequences in the style of C are also allowed. @xref{C
8981 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
8985 Enumerated constants consist of an enumerated identifier.
8988 Boolean constants consist of the identifiers @code{TRUE} and
8992 Pointer constants consist of integral values only.
8995 Set constants are not yet supported.
8999 @subsubsection Modula-2 defaults
9000 @cindex Modula-2 defaults
9002 If type and range checking are set automatically by @value{GDBN}, they
9003 both default to @code{on} whenever the working language changes to
9004 Modula-2. This happens regardless of whether you or @value{GDBN}
9005 selected the working language.
9007 If you allow @value{GDBN} to set the language automatically, then entering
9008 code compiled from a file whose name ends with @file{.mod} sets the
9009 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
9010 the language automatically}, for further details.
9013 @subsubsection Deviations from standard Modula-2
9014 @cindex Modula-2, deviations from
9016 A few changes have been made to make Modula-2 programs easier to debug.
9017 This is done primarily via loosening its type strictness:
9021 Unlike in standard Modula-2, pointer constants can be formed by
9022 integers. This allows you to modify pointer variables during
9023 debugging. (In standard Modula-2, the actual address contained in a
9024 pointer variable is hidden from you; it can only be modified
9025 through direct assignment to another pointer variable or expression that
9026 returned a pointer.)
9029 C escape sequences can be used in strings and characters to represent
9030 non-printable characters. @value{GDBN} prints out strings with these
9031 escape sequences embedded. Single non-printable characters are
9032 printed using the @samp{CHR(@var{nnn})} format.
9035 The assignment operator (@code{:=}) returns the value of its right-hand
9039 All built-in procedures both modify @emph{and} return their argument.
9043 @subsubsection Modula-2 type and range checks
9044 @cindex Modula-2 checks
9047 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
9050 @c FIXME remove warning when type/range checks added
9052 @value{GDBN} considers two Modula-2 variables type equivalent if:
9056 They are of types that have been declared equivalent via a @code{TYPE
9057 @var{t1} = @var{t2}} statement
9060 They have been declared on the same line. (Note: This is true of the
9061 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
9064 As long as type checking is enabled, any attempt to combine variables
9065 whose types are not equivalent is an error.
9067 Range checking is done on all mathematical operations, assignment, array
9068 index bounds, and all built-in functions and procedures.
9071 @subsubsection The scope operators @code{::} and @code{.}
9073 @cindex @code{.}, Modula-2 scope operator
9074 @cindex colon, doubled as scope operator
9076 @vindex colon-colon@r{, in Modula-2}
9077 @c Info cannot handle :: but TeX can.
9080 @vindex ::@r{, in Modula-2}
9083 There are a few subtle differences between the Modula-2 scope operator
9084 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
9089 @var{module} . @var{id}
9090 @var{scope} :: @var{id}
9094 where @var{scope} is the name of a module or a procedure,
9095 @var{module} the name of a module, and @var{id} is any declared
9096 identifier within your program, except another module.
9098 Using the @code{::} operator makes @value{GDBN} search the scope
9099 specified by @var{scope} for the identifier @var{id}. If it is not
9100 found in the specified scope, then @value{GDBN} searches all scopes
9101 enclosing the one specified by @var{scope}.
9103 Using the @code{.} operator makes @value{GDBN} search the current scope for
9104 the identifier specified by @var{id} that was imported from the
9105 definition module specified by @var{module}. With this operator, it is
9106 an error if the identifier @var{id} was not imported from definition
9107 module @var{module}, or if @var{id} is not an identifier in
9111 @subsubsection @value{GDBN} and Modula-2
9113 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
9114 Five subcommands of @code{set print} and @code{show print} apply
9115 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
9116 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
9117 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
9118 analogue in Modula-2.
9120 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
9121 with any language, is not useful with Modula-2. Its
9122 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
9123 created in Modula-2 as they can in C or C@t{++}. However, because an
9124 address can be specified by an integral constant, the construct
9125 @samp{@{@var{type}@}@var{adrexp}} is still useful.
9127 @cindex @code{#} in Modula-2
9128 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
9129 interpreted as the beginning of a comment. Use @code{<>} instead.
9135 The extensions made to @value{GDBN} for Ada only support
9136 output from the @sc{gnu} Ada (GNAT) compiler.
9137 Other Ada compilers are not currently supported, and
9138 attempting to debug executables produced by them is most likely
9142 @cindex expressions in Ada
9144 * Ada Mode Intro:: General remarks on the Ada syntax
9145 and semantics supported by Ada mode
9147 * Omissions from Ada:: Restrictions on the Ada expression syntax.
9148 * Additions to Ada:: Extensions of the Ada expression syntax.
9149 * Stopping Before Main Program:: Debugging the program during elaboration.
9150 * Ada Glitches:: Known peculiarities of Ada mode.
9153 @node Ada Mode Intro
9154 @subsubsection Introduction
9155 @cindex Ada mode, general
9157 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
9158 syntax, with some extensions.
9159 The philosophy behind the design of this subset is
9163 That @value{GDBN} should provide basic literals and access to operations for
9164 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
9165 leaving more sophisticated computations to subprograms written into the
9166 program (which therefore may be called from @value{GDBN}).
9169 That type safety and strict adherence to Ada language restrictions
9170 are not particularly important to the @value{GDBN} user.
9173 That brevity is important to the @value{GDBN} user.
9176 Thus, for brevity, the debugger acts as if there were
9177 implicit @code{with} and @code{use} clauses in effect for all user-written
9178 packages, making it unnecessary to fully qualify most names with
9179 their packages, regardless of context. Where this causes ambiguity,
9180 @value{GDBN} asks the user's intent.
9182 The debugger will start in Ada mode if it detects an Ada main program.
9183 As for other languages, it will enter Ada mode when stopped in a program that
9184 was translated from an Ada source file.
9186 While in Ada mode, you may use `@t{--}' for comments. This is useful
9187 mostly for documenting command files. The standard @value{GDBN} comment
9188 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
9189 middle (to allow based literals).
9191 The debugger supports limited overloading. Given a subprogram call in which
9192 the function symbol has multiple definitions, it will use the number of
9193 actual parameters and some information about their types to attempt to narrow
9194 the set of definitions. It also makes very limited use of context, preferring
9195 procedures to functions in the context of the @code{call} command, and
9196 functions to procedures elsewhere.
9198 @node Omissions from Ada
9199 @subsubsection Omissions from Ada
9200 @cindex Ada, omissions from
9202 Here are the notable omissions from the subset:
9206 Only a subset of the attributes are supported:
9210 @t{'First}, @t{'Last}, and @t{'Length}
9211 on array objects (not on types and subtypes).
9214 @t{'Min} and @t{'Max}.
9217 @t{'Pos} and @t{'Val}.
9223 @t{'Range} on array objects (not subtypes), but only as the right
9224 operand of the membership (@code{in}) operator.
9227 @t{'Access}, @t{'Unchecked_Access}, and
9228 @t{'Unrestricted_Access} (a GNAT extension).
9236 @code{Characters.Latin_1} are not available and
9237 concatenation is not implemented. Thus, escape characters in strings are
9238 not currently available.
9241 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
9242 equality of representations. They will generally work correctly
9243 for strings and arrays whose elements have integer or enumeration types.
9244 They may not work correctly for arrays whose element
9245 types have user-defined equality, for arrays of real values
9246 (in particular, IEEE-conformant floating point, because of negative
9247 zeroes and NaNs), and for arrays whose elements contain unused bits with
9248 indeterminate values.
9251 The other component-by-component array operations (@code{and}, @code{or},
9252 @code{xor}, @code{not}, and relational tests other than equality)
9253 are not implemented.
9256 There are no record or array aggregates.
9259 Calls to dispatching subprograms are not implemented.
9262 The overloading algorithm is much more limited (i.e., less selective)
9263 than that of real Ada. It makes only limited use of the context in which a subexpression
9264 appears to resolve its meaning, and it is much looser in its rules for allowing
9265 type matches. As a result, some function calls will be ambiguous, and the user
9266 will be asked to choose the proper resolution.
9269 The @code{new} operator is not implemented.
9272 Entry calls are not implemented.
9275 Aside from printing, arithmetic operations on the native VAX floating-point
9276 formats are not supported.
9279 It is not possible to slice a packed array.
9282 @node Additions to Ada
9283 @subsubsection Additions to Ada
9284 @cindex Ada, deviations from
9286 As it does for other languages, @value{GDBN} makes certain generic
9287 extensions to Ada (@pxref{Expressions}):
9291 If the expression @var{E} is a variable residing in memory
9292 (typically a local variable or array element) and @var{N} is
9293 a positive integer, then @code{@var{E}@@@var{N}} displays the values of
9294 @var{E} and the @var{N}-1 adjacent variables following it in memory as an array.
9295 In Ada, this operator is generally not necessary, since its prime use
9296 is in displaying parts of an array, and slicing will usually do this in Ada.
9297 However, there are occasional uses when debugging programs
9298 in which certain debugging information has been optimized away.
9301 @code{@var{B}::@var{var}} means ``the variable named @var{var} that appears
9302 in function or file @var{B}.'' When @var{B} is a file name, you must typically
9303 surround it in single quotes.
9306 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
9307 @var{type} that appears at address @var{addr}.''
9310 A name starting with @samp{$} is a convenience variable
9311 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
9314 In addition, @value{GDBN} provides a few other shortcuts and outright additions specific
9319 The assignment statement is allowed as an expression, returning
9320 its right-hand operand as its value. Thus, you may enter
9324 print A(tmp := y + 1)
9328 The semicolon is allowed as an ``operator,'' returning as its value
9329 the value of its right-hand operand.
9330 This allows, for example,
9331 complex conditional breaks:
9335 condition 1 (report(i); k += 1; A(k) > 100)
9339 Rather than use catenation and symbolic character names to introduce special
9340 characters into strings, one may instead use a special bracket notation,
9341 which is also used to print strings. A sequence of characters of the form
9342 @samp{["@var{XX}"]} within a string or character literal denotes the
9343 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
9344 sequence of characters @samp{["""]} also denotes a single quotation mark
9345 in strings. For example,
9347 "One line.["0a"]Next line.["0a"]"
9350 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF}) after each
9354 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
9355 @t{'Max} is optional (and is ignored in any case). For example, it is valid
9363 When printing arrays, @value{GDBN} uses positional notation when the
9364 array has a lower bound of 1, and uses a modified named notation otherwise.
9365 For example, a one-dimensional array of three integers with a lower bound of 3 might print as
9372 That is, in contrast to valid Ada, only the first component has a @code{=>}
9376 You may abbreviate attributes in expressions with any unique,
9377 multi-character subsequence of
9378 their names (an exact match gets preference).
9379 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
9380 in place of @t{a'length}.
9383 @cindex quoting Ada internal identifiers
9384 Since Ada is case-insensitive, the debugger normally maps identifiers you type
9385 to lower case. The GNAT compiler uses upper-case characters for
9386 some of its internal identifiers, which are normally of no interest to users.
9387 For the rare occasions when you actually have to look at them,
9388 enclose them in angle brackets to avoid the lower-case mapping.
9391 @value{GDBP} print <JMPBUF_SAVE>[0]
9395 Printing an object of class-wide type or dereferencing an
9396 access-to-class-wide value will display all the components of the object's
9397 specific type (as indicated by its run-time tag). Likewise, component
9398 selection on such a value will operate on the specific type of the
9403 @node Stopping Before Main Program
9404 @subsubsection Stopping at the Very Beginning
9406 @cindex breakpointing Ada elaboration code
9407 It is sometimes necessary to debug the program during elaboration, and
9408 before reaching the main procedure.
9409 As defined in the Ada Reference
9410 Manual, the elaboration code is invoked from a procedure called
9411 @code{adainit}. To run your program up to the beginning of
9412 elaboration, simply use the following two commands:
9413 @code{tbreak adainit} and @code{run}.
9416 @subsubsection Known Peculiarities of Ada Mode
9417 @cindex Ada, problems
9419 Besides the omissions listed previously (@pxref{Omissions from Ada}),
9420 we know of several problems with and limitations of Ada mode in
9422 some of which will be fixed with planned future releases of the debugger
9423 and the GNU Ada compiler.
9427 Currently, the debugger
9428 has insufficient information to determine whether certain pointers represent
9429 pointers to objects or the objects themselves.
9430 Thus, the user may have to tack an extra @code{.all} after an expression
9431 to get it printed properly.
9434 Static constants that the compiler chooses not to materialize as objects in
9435 storage are invisible to the debugger.
9438 Named parameter associations in function argument lists are ignored (the
9439 argument lists are treated as positional).
9442 Many useful library packages are currently invisible to the debugger.
9445 Fixed-point arithmetic, conversions, input, and output is carried out using
9446 floating-point arithmetic, and may give results that only approximate those on
9450 The type of the @t{'Address} attribute may not be @code{System.Address}.
9453 The GNAT compiler never generates the prefix @code{Standard} for any of
9454 the standard symbols defined by the Ada language. @value{GDBN} knows about
9455 this: it will strip the prefix from names when you use it, and will never
9456 look for a name you have so qualified among local symbols, nor match against
9457 symbols in other packages or subprograms. If you have
9458 defined entities anywhere in your program other than parameters and
9459 local variables whose simple names match names in @code{Standard},
9460 GNAT's lack of qualification here can cause confusion. When this happens,
9461 you can usually resolve the confusion
9462 by qualifying the problematic names with package
9463 @code{Standard} explicitly.
9466 @node Unsupported languages
9467 @section Unsupported languages
9469 @cindex unsupported languages
9470 @cindex minimal language
9471 In addition to the other fully-supported programming languages,
9472 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
9473 It does not represent a real programming language, but provides a set
9474 of capabilities close to what the C or assembly languages provide.
9475 This should allow most simple operations to be performed while debugging
9476 an application that uses a language currently not supported by @value{GDBN}.
9478 If the language is set to @code{auto}, @value{GDBN} will automatically
9479 select this language if the current frame corresponds to an unsupported
9483 @chapter Examining the Symbol Table
9485 The commands described in this chapter allow you to inquire about the
9486 symbols (names of variables, functions and types) defined in your
9487 program. This information is inherent in the text of your program and
9488 does not change as your program executes. @value{GDBN} finds it in your
9489 program's symbol table, in the file indicated when you started @value{GDBN}
9490 (@pxref{File Options, ,Choosing files}), or by one of the
9491 file-management commands (@pxref{Files, ,Commands to specify files}).
9493 @cindex symbol names
9494 @cindex names of symbols
9495 @cindex quoting names
9496 Occasionally, you may need to refer to symbols that contain unusual
9497 characters, which @value{GDBN} ordinarily treats as word delimiters. The
9498 most frequent case is in referring to static variables in other
9499 source files (@pxref{Variables,,Program variables}). File names
9500 are recorded in object files as debugging symbols, but @value{GDBN} would
9501 ordinarily parse a typical file name, like @file{foo.c}, as the three words
9502 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
9503 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
9510 looks up the value of @code{x} in the scope of the file @file{foo.c}.
9513 @kindex info address
9514 @cindex address of a symbol
9515 @item info address @var{symbol}
9516 Describe where the data for @var{symbol} is stored. For a register
9517 variable, this says which register it is kept in. For a non-register
9518 local variable, this prints the stack-frame offset at which the variable
9521 Note the contrast with @samp{print &@var{symbol}}, which does not work
9522 at all for a register variable, and for a stack local variable prints
9523 the exact address of the current instantiation of the variable.
9526 @cindex symbol from address
9527 @item info symbol @var{addr}
9528 Print the name of a symbol which is stored at the address @var{addr}.
9529 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
9530 nearest symbol and an offset from it:
9533 (@value{GDBP}) info symbol 0x54320
9534 _initialize_vx + 396 in section .text
9538 This is the opposite of the @code{info address} command. You can use
9539 it to find out the name of a variable or a function given its address.
9542 @item whatis @var{expr}
9543 Print the data type of expression @var{expr}. @var{expr} is not
9544 actually evaluated, and any side-effecting operations (such as
9545 assignments or function calls) inside it do not take place.
9546 @xref{Expressions, ,Expressions}.
9549 Print the data type of @code{$}, the last value in the value history.
9552 @item ptype @var{typename}
9553 Print a description of data type @var{typename}. @var{typename} may be
9554 the name of a type, or for C code it may have the form @samp{class
9555 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
9556 @var{union-tag}} or @samp{enum @var{enum-tag}}.
9558 @item ptype @var{expr}
9560 Print a description of the type of expression @var{expr}. @code{ptype}
9561 differs from @code{whatis} by printing a detailed description, instead
9562 of just the name of the type.
9564 For example, for this variable declaration:
9567 struct complex @{double real; double imag;@} v;
9571 the two commands give this output:
9575 (@value{GDBP}) whatis v
9576 type = struct complex
9577 (@value{GDBP}) ptype v
9578 type = struct complex @{
9586 As with @code{whatis}, using @code{ptype} without an argument refers to
9587 the type of @code{$}, the last value in the value history.
9590 @item info types @var{regexp}
9592 Print a brief description of all types whose names match @var{regexp}
9593 (or all types in your program, if you supply no argument). Each
9594 complete typename is matched as though it were a complete line; thus,
9595 @samp{i type value} gives information on all types in your program whose
9596 names include the string @code{value}, but @samp{i type ^value$} gives
9597 information only on types whose complete name is @code{value}.
9599 This command differs from @code{ptype} in two ways: first, like
9600 @code{whatis}, it does not print a detailed description; second, it
9601 lists all source files where a type is defined.
9604 @cindex local variables
9605 @item info scope @var{addr}
9606 List all the variables local to a particular scope. This command
9607 accepts a location---a function name, a source line, or an address
9608 preceded by a @samp{*}, and prints all the variables local to the
9609 scope defined by that location. For example:
9612 (@value{GDBP}) @b{info scope command_line_handler}
9613 Scope for command_line_handler:
9614 Symbol rl is an argument at stack/frame offset 8, length 4.
9615 Symbol linebuffer is in static storage at address 0x150a18, length 4.
9616 Symbol linelength is in static storage at address 0x150a1c, length 4.
9617 Symbol p is a local variable in register $esi, length 4.
9618 Symbol p1 is a local variable in register $ebx, length 4.
9619 Symbol nline is a local variable in register $edx, length 4.
9620 Symbol repeat is a local variable at frame offset -8, length 4.
9624 This command is especially useful for determining what data to collect
9625 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
9630 Show information about the current source file---that is, the source file for
9631 the function containing the current point of execution:
9634 the name of the source file, and the directory containing it,
9636 the directory it was compiled in,
9638 its length, in lines,
9640 which programming language it is written in,
9642 whether the executable includes debugging information for that file, and
9643 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
9645 whether the debugging information includes information about
9646 preprocessor macros.
9650 @kindex info sources
9652 Print the names of all source files in your program for which there is
9653 debugging information, organized into two lists: files whose symbols
9654 have already been read, and files whose symbols will be read when needed.
9656 @kindex info functions
9657 @item info functions
9658 Print the names and data types of all defined functions.
9660 @item info functions @var{regexp}
9661 Print the names and data types of all defined functions
9662 whose names contain a match for regular expression @var{regexp}.
9663 Thus, @samp{info fun step} finds all functions whose names
9664 include @code{step}; @samp{info fun ^step} finds those whose names
9665 start with @code{step}. If a function name contains characters
9666 that conflict with the regular expression language (eg.
9667 @samp{operator*()}), they may be quoted with a backslash.
9669 @kindex info variables
9670 @item info variables
9671 Print the names and data types of all variables that are declared
9672 outside of functions (i.e.@: excluding local variables).
9674 @item info variables @var{regexp}
9675 Print the names and data types of all variables (except for local
9676 variables) whose names contain a match for regular expression
9679 @kindex info classes
9681 @itemx info classes @var{regexp}
9682 Display all Objective-C classes in your program, or
9683 (with the @var{regexp} argument) all those matching a particular regular
9686 @kindex info selectors
9687 @item info selectors
9688 @itemx info selectors @var{regexp}
9689 Display all Objective-C selectors in your program, or
9690 (with the @var{regexp} argument) all those matching a particular regular
9694 This was never implemented.
9695 @kindex info methods
9697 @itemx info methods @var{regexp}
9698 The @code{info methods} command permits the user to examine all defined
9699 methods within C@t{++} program, or (with the @var{regexp} argument) a
9700 specific set of methods found in the various C@t{++} classes. Many
9701 C@t{++} classes provide a large number of methods. Thus, the output
9702 from the @code{ptype} command can be overwhelming and hard to use. The
9703 @code{info-methods} command filters the methods, printing only those
9704 which match the regular-expression @var{regexp}.
9707 @cindex reloading symbols
9708 Some systems allow individual object files that make up your program to
9709 be replaced without stopping and restarting your program. For example,
9710 in VxWorks you can simply recompile a defective object file and keep on
9711 running. If you are running on one of these systems, you can allow
9712 @value{GDBN} to reload the symbols for automatically relinked modules:
9715 @kindex set symbol-reloading
9716 @item set symbol-reloading on
9717 Replace symbol definitions for the corresponding source file when an
9718 object file with a particular name is seen again.
9720 @item set symbol-reloading off
9721 Do not replace symbol definitions when encountering object files of the
9722 same name more than once. This is the default state; if you are not
9723 running on a system that permits automatic relinking of modules, you
9724 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
9725 may discard symbols when linking large programs, that may contain
9726 several modules (from different directories or libraries) with the same
9729 @kindex show symbol-reloading
9730 @item show symbol-reloading
9731 Show the current @code{on} or @code{off} setting.
9734 @kindex set opaque-type-resolution
9735 @item set opaque-type-resolution on
9736 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
9737 declared as a pointer to a @code{struct}, @code{class}, or
9738 @code{union}---for example, @code{struct MyType *}---that is used in one
9739 source file although the full declaration of @code{struct MyType} is in
9740 another source file. The default is on.
9742 A change in the setting of this subcommand will not take effect until
9743 the next time symbols for a file are loaded.
9745 @item set opaque-type-resolution off
9746 Tell @value{GDBN} not to resolve opaque types. In this case, the type
9747 is printed as follows:
9749 @{<no data fields>@}
9752 @kindex show opaque-type-resolution
9753 @item show opaque-type-resolution
9754 Show whether opaque types are resolved or not.
9756 @kindex maint print symbols
9758 @kindex maint print psymbols
9759 @cindex partial symbol dump
9760 @item maint print symbols @var{filename}
9761 @itemx maint print psymbols @var{filename}
9762 @itemx maint print msymbols @var{filename}
9763 Write a dump of debugging symbol data into the file @var{filename}.
9764 These commands are used to debug the @value{GDBN} symbol-reading code. Only
9765 symbols with debugging data are included. If you use @samp{maint print
9766 symbols}, @value{GDBN} includes all the symbols for which it has already
9767 collected full details: that is, @var{filename} reflects symbols for
9768 only those files whose symbols @value{GDBN} has read. You can use the
9769 command @code{info sources} to find out which files these are. If you
9770 use @samp{maint print psymbols} instead, the dump shows information about
9771 symbols that @value{GDBN} only knows partially---that is, symbols defined in
9772 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
9773 @samp{maint print msymbols} dumps just the minimal symbol information
9774 required for each object file from which @value{GDBN} has read some symbols.
9775 @xref{Files, ,Commands to specify files}, for a discussion of how
9776 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
9778 @kindex maint info symtabs
9779 @kindex maint info psymtabs
9780 @cindex listing @value{GDBN}'s internal symbol tables
9781 @cindex symbol tables, listing @value{GDBN}'s internal
9782 @cindex full symbol tables, listing @value{GDBN}'s internal
9783 @cindex partial symbol tables, listing @value{GDBN}'s internal
9784 @item maint info symtabs @r{[} @var{regexp} @r{]}
9785 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
9787 List the @code{struct symtab} or @code{struct partial_symtab}
9788 structures whose names match @var{regexp}. If @var{regexp} is not
9789 given, list them all. The output includes expressions which you can
9790 copy into a @value{GDBN} debugging this one to examine a particular
9791 structure in more detail. For example:
9794 (@value{GDBP}) maint info psymtabs dwarf2read
9795 @{ objfile /home/gnu/build/gdb/gdb
9796 ((struct objfile *) 0x82e69d0)
9797 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
9798 ((struct partial_symtab *) 0x8474b10)
9801 text addresses 0x814d3c8 -- 0x8158074
9802 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
9803 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
9807 (@value{GDBP}) maint info symtabs
9811 We see that there is one partial symbol table whose filename contains
9812 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
9813 and we see that @value{GDBN} has not read in any symtabs yet at all.
9814 If we set a breakpoint on a function, that will cause @value{GDBN} to
9815 read the symtab for the compilation unit containing that function:
9818 (@value{GDBP}) break dwarf2_psymtab_to_symtab
9819 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
9821 (@value{GDBP}) maint info symtabs
9822 @{ objfile /home/gnu/build/gdb/gdb
9823 ((struct objfile *) 0x82e69d0)
9824 @{ symtab /home/gnu/src/gdb/dwarf2read.c
9825 ((struct symtab *) 0x86c1f38)
9828 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
9838 @chapter Altering Execution
9840 Once you think you have found an error in your program, you might want to
9841 find out for certain whether correcting the apparent error would lead to
9842 correct results in the rest of the run. You can find the answer by
9843 experiment, using the @value{GDBN} features for altering execution of the
9846 For example, you can store new values into variables or memory
9847 locations, give your program a signal, restart it at a different
9848 address, or even return prematurely from a function.
9851 * Assignment:: Assignment to variables
9852 * Jumping:: Continuing at a different address
9853 * Signaling:: Giving your program a signal
9854 * Returning:: Returning from a function
9855 * Calling:: Calling your program's functions
9856 * Patching:: Patching your program
9860 @section Assignment to variables
9863 @cindex setting variables
9864 To alter the value of a variable, evaluate an assignment expression.
9865 @xref{Expressions, ,Expressions}. For example,
9872 stores the value 4 into the variable @code{x}, and then prints the
9873 value of the assignment expression (which is 4).
9874 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
9875 information on operators in supported languages.
9877 @kindex set variable
9878 @cindex variables, setting
9879 If you are not interested in seeing the value of the assignment, use the
9880 @code{set} command instead of the @code{print} command. @code{set} is
9881 really the same as @code{print} except that the expression's value is
9882 not printed and is not put in the value history (@pxref{Value History,
9883 ,Value history}). The expression is evaluated only for its effects.
9885 If the beginning of the argument string of the @code{set} command
9886 appears identical to a @code{set} subcommand, use the @code{set
9887 variable} command instead of just @code{set}. This command is identical
9888 to @code{set} except for its lack of subcommands. For example, if your
9889 program has a variable @code{width}, you get an error if you try to set
9890 a new value with just @samp{set width=13}, because @value{GDBN} has the
9891 command @code{set width}:
9894 (@value{GDBP}) whatis width
9896 (@value{GDBP}) p width
9898 (@value{GDBP}) set width=47
9899 Invalid syntax in expression.
9903 The invalid expression, of course, is @samp{=47}. In
9904 order to actually set the program's variable @code{width}, use
9907 (@value{GDBP}) set var width=47
9910 Because the @code{set} command has many subcommands that can conflict
9911 with the names of program variables, it is a good idea to use the
9912 @code{set variable} command instead of just @code{set}. For example, if
9913 your program has a variable @code{g}, you run into problems if you try
9914 to set a new value with just @samp{set g=4}, because @value{GDBN} has
9915 the command @code{set gnutarget}, abbreviated @code{set g}:
9919 (@value{GDBP}) whatis g
9923 (@value{GDBP}) set g=4
9927 The program being debugged has been started already.
9928 Start it from the beginning? (y or n) y
9929 Starting program: /home/smith/cc_progs/a.out
9930 "/home/smith/cc_progs/a.out": can't open to read symbols:
9932 (@value{GDBP}) show g
9933 The current BFD target is "=4".
9938 The program variable @code{g} did not change, and you silently set the
9939 @code{gnutarget} to an invalid value. In order to set the variable
9943 (@value{GDBP}) set var g=4
9946 @value{GDBN} allows more implicit conversions in assignments than C; you can
9947 freely store an integer value into a pointer variable or vice versa,
9948 and you can convert any structure to any other structure that is the
9949 same length or shorter.
9950 @comment FIXME: how do structs align/pad in these conversions?
9951 @comment /doc@cygnus.com 18dec1990
9953 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
9954 construct to generate a value of specified type at a specified address
9955 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
9956 to memory location @code{0x83040} as an integer (which implies a certain size
9957 and representation in memory), and
9960 set @{int@}0x83040 = 4
9964 stores the value 4 into that memory location.
9967 @section Continuing at a different address
9969 Ordinarily, when you continue your program, you do so at the place where
9970 it stopped, with the @code{continue} command. You can instead continue at
9971 an address of your own choosing, with the following commands:
9975 @item jump @var{linespec}
9976 Resume execution at line @var{linespec}. Execution stops again
9977 immediately if there is a breakpoint there. @xref{List, ,Printing
9978 source lines}, for a description of the different forms of
9979 @var{linespec}. It is common practice to use the @code{tbreak} command
9980 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
9983 The @code{jump} command does not change the current stack frame, or
9984 the stack pointer, or the contents of any memory location or any
9985 register other than the program counter. If line @var{linespec} is in
9986 a different function from the one currently executing, the results may
9987 be bizarre if the two functions expect different patterns of arguments or
9988 of local variables. For this reason, the @code{jump} command requests
9989 confirmation if the specified line is not in the function currently
9990 executing. However, even bizarre results are predictable if you are
9991 well acquainted with the machine-language code of your program.
9993 @item jump *@var{address}
9994 Resume execution at the instruction at address @var{address}.
9997 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
9998 On many systems, you can get much the same effect as the @code{jump}
9999 command by storing a new value into the register @code{$pc}. The
10000 difference is that this does not start your program running; it only
10001 changes the address of where it @emph{will} run when you continue. For
10009 makes the next @code{continue} command or stepping command execute at
10010 address @code{0x485}, rather than at the address where your program stopped.
10011 @xref{Continuing and Stepping, ,Continuing and stepping}.
10013 The most common occasion to use the @code{jump} command is to back
10014 up---perhaps with more breakpoints set---over a portion of a program
10015 that has already executed, in order to examine its execution in more
10020 @section Giving your program a signal
10024 @item signal @var{signal}
10025 Resume execution where your program stopped, but immediately give it the
10026 signal @var{signal}. @var{signal} can be the name or the number of a
10027 signal. For example, on many systems @code{signal 2} and @code{signal
10028 SIGINT} are both ways of sending an interrupt signal.
10030 Alternatively, if @var{signal} is zero, continue execution without
10031 giving a signal. This is useful when your program stopped on account of
10032 a signal and would ordinary see the signal when resumed with the
10033 @code{continue} command; @samp{signal 0} causes it to resume without a
10036 @code{signal} does not repeat when you press @key{RET} a second time
10037 after executing the command.
10041 Invoking the @code{signal} command is not the same as invoking the
10042 @code{kill} utility from the shell. Sending a signal with @code{kill}
10043 causes @value{GDBN} to decide what to do with the signal depending on
10044 the signal handling tables (@pxref{Signals}). The @code{signal} command
10045 passes the signal directly to your program.
10049 @section Returning from a function
10052 @cindex returning from a function
10055 @itemx return @var{expression}
10056 You can cancel execution of a function call with the @code{return}
10057 command. If you give an
10058 @var{expression} argument, its value is used as the function's return
10062 When you use @code{return}, @value{GDBN} discards the selected stack frame
10063 (and all frames within it). You can think of this as making the
10064 discarded frame return prematurely. If you wish to specify a value to
10065 be returned, give that value as the argument to @code{return}.
10067 This pops the selected stack frame (@pxref{Selection, ,Selecting a
10068 frame}), and any other frames inside of it, leaving its caller as the
10069 innermost remaining frame. That frame becomes selected. The
10070 specified value is stored in the registers used for returning values
10073 The @code{return} command does not resume execution; it leaves the
10074 program stopped in the state that would exist if the function had just
10075 returned. In contrast, the @code{finish} command (@pxref{Continuing
10076 and Stepping, ,Continuing and stepping}) resumes execution until the
10077 selected stack frame returns naturally.
10080 @section Calling program functions
10083 @cindex calling functions
10084 @cindex inferior functions, calling
10085 @item print @var{expr}
10086 Evaluate the expression @var{expr} and displaying the resuling value.
10087 @var{expr} may include calls to functions in the program being
10091 @item call @var{expr}
10092 Evaluate the expression @var{expr} without displaying @code{void}
10095 You can use this variant of the @code{print} command if you want to
10096 execute a function from your program that does not return anything
10097 (a.k.a.@: @dfn{a void function}), but without cluttering the output
10098 with @code{void} returned values that @value{GDBN} will otherwise
10099 print. If the result is not void, it is printed and saved in the
10103 @cindex weak alias functions
10104 Sometimes, a function you wish to call is actually a @dfn{weak alias}
10105 for another function. In such case, @value{GDBN} might not pick up
10106 the type information, including the types of the function arguments,
10107 which causes @value{GDBN} to call the inferior function incorrectly.
10108 As a result, the called function will function erroneously and may
10109 even crash. A solution to that is to use the name of the aliased
10113 @section Patching programs
10115 @cindex patching binaries
10116 @cindex writing into executables
10117 @cindex writing into corefiles
10119 By default, @value{GDBN} opens the file containing your program's
10120 executable code (or the corefile) read-only. This prevents accidental
10121 alterations to machine code; but it also prevents you from intentionally
10122 patching your program's binary.
10124 If you'd like to be able to patch the binary, you can specify that
10125 explicitly with the @code{set write} command. For example, you might
10126 want to turn on internal debugging flags, or even to make emergency
10132 @itemx set write off
10133 If you specify @samp{set write on}, @value{GDBN} opens executable and
10134 core files for both reading and writing; if you specify @samp{set write
10135 off} (the default), @value{GDBN} opens them read-only.
10137 If you have already loaded a file, you must load it again (using the
10138 @code{exec-file} or @code{core-file} command) after changing @code{set
10139 write}, for your new setting to take effect.
10143 Display whether executable files and core files are opened for writing
10144 as well as reading.
10148 @chapter @value{GDBN} Files
10150 @value{GDBN} needs to know the file name of the program to be debugged,
10151 both in order to read its symbol table and in order to start your
10152 program. To debug a core dump of a previous run, you must also tell
10153 @value{GDBN} the name of the core dump file.
10156 * Files:: Commands to specify files
10157 * Separate Debug Files:: Debugging information in separate files
10158 * Symbol Errors:: Errors reading symbol files
10162 @section Commands to specify files
10164 @cindex symbol table
10165 @cindex core dump file
10167 You may want to specify executable and core dump file names. The usual
10168 way to do this is at start-up time, using the arguments to
10169 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
10170 Out of @value{GDBN}}).
10172 Occasionally it is necessary to change to a different file during a
10173 @value{GDBN} session. Or you may run @value{GDBN} and forget to specify
10174 a file you want to use. In these situations the @value{GDBN} commands
10175 to specify new files are useful.
10178 @cindex executable file
10180 @item file @var{filename}
10181 Use @var{filename} as the program to be debugged. It is read for its
10182 symbols and for the contents of pure memory. It is also the program
10183 executed when you use the @code{run} command. If you do not specify a
10184 directory and the file is not found in the @value{GDBN} working directory,
10185 @value{GDBN} uses the environment variable @code{PATH} as a list of
10186 directories to search, just as the shell does when looking for a program
10187 to run. You can change the value of this variable, for both @value{GDBN}
10188 and your program, using the @code{path} command.
10190 On systems with memory-mapped files, an auxiliary file named
10191 @file{@var{filename}.syms} may hold symbol table information for
10192 @var{filename}. If so, @value{GDBN} maps in the symbol table from
10193 @file{@var{filename}.syms}, starting up more quickly. See the
10194 descriptions of the file options @samp{-mapped} and @samp{-readnow}
10195 (available on the command line, and with the commands @code{file},
10196 @code{symbol-file}, or @code{add-symbol-file}, described below),
10197 for more information.
10200 @code{file} with no argument makes @value{GDBN} discard any information it
10201 has on both executable file and the symbol table.
10204 @item exec-file @r{[} @var{filename} @r{]}
10205 Specify that the program to be run (but not the symbol table) is found
10206 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
10207 if necessary to locate your program. Omitting @var{filename} means to
10208 discard information on the executable file.
10210 @kindex symbol-file
10211 @item symbol-file @r{[} @var{filename} @r{]}
10212 Read symbol table information from file @var{filename}. @code{PATH} is
10213 searched when necessary. Use the @code{file} command to get both symbol
10214 table and program to run from the same file.
10216 @code{symbol-file} with no argument clears out @value{GDBN} information on your
10217 program's symbol table.
10219 The @code{symbol-file} command causes @value{GDBN} to forget the contents
10220 of its convenience variables, the value history, and all breakpoints and
10221 auto-display expressions. This is because they may contain pointers to
10222 the internal data recording symbols and data types, which are part of
10223 the old symbol table data being discarded inside @value{GDBN}.
10225 @code{symbol-file} does not repeat if you press @key{RET} again after
10228 When @value{GDBN} is configured for a particular environment, it
10229 understands debugging information in whatever format is the standard
10230 generated for that environment; you may use either a @sc{gnu} compiler, or
10231 other compilers that adhere to the local conventions.
10232 Best results are usually obtained from @sc{gnu} compilers; for example,
10233 using @code{@value{GCC}} you can generate debugging information for
10236 For most kinds of object files, with the exception of old SVR3 systems
10237 using COFF, the @code{symbol-file} command does not normally read the
10238 symbol table in full right away. Instead, it scans the symbol table
10239 quickly to find which source files and which symbols are present. The
10240 details are read later, one source file at a time, as they are needed.
10242 The purpose of this two-stage reading strategy is to make @value{GDBN}
10243 start up faster. For the most part, it is invisible except for
10244 occasional pauses while the symbol table details for a particular source
10245 file are being read. (The @code{set verbose} command can turn these
10246 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
10247 warnings and messages}.)
10249 We have not implemented the two-stage strategy for COFF yet. When the
10250 symbol table is stored in COFF format, @code{symbol-file} reads the
10251 symbol table data in full right away. Note that ``stabs-in-COFF''
10252 still does the two-stage strategy, since the debug info is actually
10256 @cindex reading symbols immediately
10257 @cindex symbols, reading immediately
10259 @cindex memory-mapped symbol file
10260 @cindex saving symbol table
10261 @item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10262 @itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10263 You can override the @value{GDBN} two-stage strategy for reading symbol
10264 tables by using the @samp{-readnow} option with any of the commands that
10265 load symbol table information, if you want to be sure @value{GDBN} has the
10266 entire symbol table available.
10268 If memory-mapped files are available on your system through the
10269 @code{mmap} system call, you can use another option, @samp{-mapped}, to
10270 cause @value{GDBN} to write the symbols for your program into a reusable
10271 file. Future @value{GDBN} debugging sessions map in symbol information
10272 from this auxiliary symbol file (if the program has not changed), rather
10273 than spending time reading the symbol table from the executable
10274 program. Using the @samp{-mapped} option has the same effect as
10275 starting @value{GDBN} with the @samp{-mapped} command-line option.
10277 You can use both options together, to make sure the auxiliary symbol
10278 file has all the symbol information for your program.
10280 The auxiliary symbol file for a program called @var{myprog} is called
10281 @samp{@var{myprog}.syms}. Once this file exists (so long as it is newer
10282 than the corresponding executable), @value{GDBN} always attempts to use
10283 it when you debug @var{myprog}; no special options or commands are
10286 The @file{.syms} file is specific to the host machine where you run
10287 @value{GDBN}. It holds an exact image of the internal @value{GDBN}
10288 symbol table. It cannot be shared across multiple host platforms.
10290 @c FIXME: for now no mention of directories, since this seems to be in
10291 @c flux. 13mar1992 status is that in theory GDB would look either in
10292 @c current dir or in same dir as myprog; but issues like competing
10293 @c GDB's, or clutter in system dirs, mean that in practice right now
10294 @c only current dir is used. FFish says maybe a special GDB hierarchy
10295 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
10299 @item core-file @r{[} @var{filename} @r{]}
10301 Specify the whereabouts of a core dump file to be used as the ``contents
10302 of memory''. Traditionally, core files contain only some parts of the
10303 address space of the process that generated them; @value{GDBN} can access the
10304 executable file itself for other parts.
10306 @code{core-file} with no argument specifies that no core file is
10309 Note that the core file is ignored when your program is actually running
10310 under @value{GDBN}. So, if you have been running your program and you
10311 wish to debug a core file instead, you must kill the subprocess in which
10312 the program is running. To do this, use the @code{kill} command
10313 (@pxref{Kill Process, ,Killing the child process}).
10315 @kindex add-symbol-file
10316 @cindex dynamic linking
10317 @item add-symbol-file @var{filename} @var{address}
10318 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10319 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
10320 The @code{add-symbol-file} command reads additional symbol table
10321 information from the file @var{filename}. You would use this command
10322 when @var{filename} has been dynamically loaded (by some other means)
10323 into the program that is running. @var{address} should be the memory
10324 address at which the file has been loaded; @value{GDBN} cannot figure
10325 this out for itself. You can additionally specify an arbitrary number
10326 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
10327 section name and base address for that section. You can specify any
10328 @var{address} as an expression.
10330 The symbol table of the file @var{filename} is added to the symbol table
10331 originally read with the @code{symbol-file} command. You can use the
10332 @code{add-symbol-file} command any number of times; the new symbol data
10333 thus read keeps adding to the old. To discard all old symbol data
10334 instead, use the @code{symbol-file} command without any arguments.
10336 @cindex relocatable object files, reading symbols from
10337 @cindex object files, relocatable, reading symbols from
10338 @cindex reading symbols from relocatable object files
10339 @cindex symbols, reading from relocatable object files
10340 @cindex @file{.o} files, reading symbols from
10341 Although @var{filename} is typically a shared library file, an
10342 executable file, or some other object file which has been fully
10343 relocated for loading into a process, you can also load symbolic
10344 information from relocatable @file{.o} files, as long as:
10348 the file's symbolic information refers only to linker symbols defined in
10349 that file, not to symbols defined by other object files,
10351 every section the file's symbolic information refers to has actually
10352 been loaded into the inferior, as it appears in the file, and
10354 you can determine the address at which every section was loaded, and
10355 provide these to the @code{add-symbol-file} command.
10359 Some embedded operating systems, like Sun Chorus and VxWorks, can load
10360 relocatable files into an already running program; such systems
10361 typically make the requirements above easy to meet. However, it's
10362 important to recognize that many native systems use complex link
10363 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
10364 assembly, for example) that make the requirements difficult to meet. In
10365 general, one cannot assume that using @code{add-symbol-file} to read a
10366 relocatable object file's symbolic information will have the same effect
10367 as linking the relocatable object file into the program in the normal
10370 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
10372 You can use the @samp{-mapped} and @samp{-readnow} options just as with
10373 the @code{symbol-file} command, to change how @value{GDBN} manages the symbol
10374 table information for @var{filename}.
10376 @kindex add-shared-symbol-file
10377 @item add-shared-symbol-file
10378 The @code{add-shared-symbol-file} command can be used only under Harris' CXUX
10379 operating system for the Motorola 88k. @value{GDBN} automatically looks for
10380 shared libraries, however if @value{GDBN} does not find yours, you can run
10381 @code{add-shared-symbol-file}. It takes no arguments.
10385 The @code{section} command changes the base address of section SECTION of
10386 the exec file to ADDR. This can be used if the exec file does not contain
10387 section addresses, (such as in the a.out format), or when the addresses
10388 specified in the file itself are wrong. Each section must be changed
10389 separately. The @code{info files} command, described below, lists all
10390 the sections and their addresses.
10393 @kindex info target
10396 @code{info files} and @code{info target} are synonymous; both print the
10397 current target (@pxref{Targets, ,Specifying a Debugging Target}),
10398 including the names of the executable and core dump files currently in
10399 use by @value{GDBN}, and the files from which symbols were loaded. The
10400 command @code{help target} lists all possible targets rather than
10403 @kindex maint info sections
10404 @item maint info sections
10405 Another command that can give you extra information about program sections
10406 is @code{maint info sections}. In addition to the section information
10407 displayed by @code{info files}, this command displays the flags and file
10408 offset of each section in the executable and core dump files. In addition,
10409 @code{maint info sections} provides the following command options (which
10410 may be arbitrarily combined):
10414 Display sections for all loaded object files, including shared libraries.
10415 @item @var{sections}
10416 Display info only for named @var{sections}.
10417 @item @var{section-flags}
10418 Display info only for sections for which @var{section-flags} are true.
10419 The section flags that @value{GDBN} currently knows about are:
10422 Section will have space allocated in the process when loaded.
10423 Set for all sections except those containing debug information.
10425 Section will be loaded from the file into the child process memory.
10426 Set for pre-initialized code and data, clear for @code{.bss} sections.
10428 Section needs to be relocated before loading.
10430 Section cannot be modified by the child process.
10432 Section contains executable code only.
10434 Section contains data only (no executable code).
10436 Section will reside in ROM.
10438 Section contains data for constructor/destructor lists.
10440 Section is not empty.
10442 An instruction to the linker to not output the section.
10443 @item COFF_SHARED_LIBRARY
10444 A notification to the linker that the section contains
10445 COFF shared library information.
10447 Section contains common symbols.
10450 @kindex set trust-readonly-sections
10451 @item set trust-readonly-sections on
10452 Tell @value{GDBN} that readonly sections in your object file
10453 really are read-only (i.e.@: that their contents will not change).
10454 In that case, @value{GDBN} can fetch values from these sections
10455 out of the object file, rather than from the target program.
10456 For some targets (notably embedded ones), this can be a significant
10457 enhancement to debugging performance.
10459 The default is off.
10461 @item set trust-readonly-sections off
10462 Tell @value{GDBN} not to trust readonly sections. This means that
10463 the contents of the section might change while the program is running,
10464 and must therefore be fetched from the target when needed.
10467 All file-specifying commands allow both absolute and relative file names
10468 as arguments. @value{GDBN} always converts the file name to an absolute file
10469 name and remembers it that way.
10471 @cindex shared libraries
10472 @value{GDBN} supports HP-UX, SunOS, SVr4, Irix 5, and IBM RS/6000 shared
10475 @value{GDBN} automatically loads symbol definitions from shared libraries
10476 when you use the @code{run} command, or when you examine a core file.
10477 (Before you issue the @code{run} command, @value{GDBN} does not understand
10478 references to a function in a shared library, however---unless you are
10479 debugging a core file).
10481 On HP-UX, if the program loads a library explicitly, @value{GDBN}
10482 automatically loads the symbols at the time of the @code{shl_load} call.
10484 @c FIXME: some @value{GDBN} release may permit some refs to undef
10485 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
10486 @c FIXME...lib; check this from time to time when updating manual
10488 There are times, however, when you may wish to not automatically load
10489 symbol definitions from shared libraries, such as when they are
10490 particularly large or there are many of them.
10492 To control the automatic loading of shared library symbols, use the
10496 @kindex set auto-solib-add
10497 @item set auto-solib-add @var{mode}
10498 If @var{mode} is @code{on}, symbols from all shared object libraries
10499 will be loaded automatically when the inferior begins execution, you
10500 attach to an independently started inferior, or when the dynamic linker
10501 informs @value{GDBN} that a new library has been loaded. If @var{mode}
10502 is @code{off}, symbols must be loaded manually, using the
10503 @code{sharedlibrary} command. The default value is @code{on}.
10505 @cindex memory used for symbol tables
10506 If your program uses lots of shared libraries with debug info that
10507 takes large amounts of memory, you can decrease the @value{GDBN}
10508 memory footprint by preventing it from automatically loading the
10509 symbols from shared libraries. To that end, type @kbd{set
10510 auto-solib-add off} before running the inferior, then load each
10511 library whose debug symbols you do need with @kbd{sharedlibrary
10512 @var{regexp}}, where @var{regexp} is a regular expresion that matches
10513 the libraries whose symbols you want to be loaded.
10515 @kindex show auto-solib-add
10516 @item show auto-solib-add
10517 Display the current autoloading mode.
10520 To explicitly load shared library symbols, use the @code{sharedlibrary}
10524 @kindex info sharedlibrary
10527 @itemx info sharedlibrary
10528 Print the names of the shared libraries which are currently loaded.
10530 @kindex sharedlibrary
10532 @item sharedlibrary @var{regex}
10533 @itemx share @var{regex}
10534 Load shared object library symbols for files matching a
10535 Unix regular expression.
10536 As with files loaded automatically, it only loads shared libraries
10537 required by your program for a core file or after typing @code{run}. If
10538 @var{regex} is omitted all shared libraries required by your program are
10542 On some systems, such as HP-UX systems, @value{GDBN} supports
10543 autoloading shared library symbols until a limiting threshold size is
10544 reached. This provides the benefit of allowing autoloading to remain on
10545 by default, but avoids autoloading excessively large shared libraries,
10546 up to a threshold that is initially set, but which you can modify if you
10549 Beyond that threshold, symbols from shared libraries must be explicitly
10550 loaded. To load these symbols, use the command @code{sharedlibrary
10551 @var{filename}}. The base address of the shared library is determined
10552 automatically by @value{GDBN} and need not be specified.
10554 To display or set the threshold, use the commands:
10557 @kindex set auto-solib-limit
10558 @item set auto-solib-limit @var{threshold}
10559 Set the autoloading size threshold, in an integral number of megabytes.
10560 If @var{threshold} is nonzero and shared library autoloading is enabled,
10561 symbols from all shared object libraries will be loaded until the total
10562 size of the loaded shared library symbols exceeds this threshold.
10563 Otherwise, symbols must be loaded manually, using the
10564 @code{sharedlibrary} command. The default threshold is 100 (i.e.@: 100
10567 @kindex show auto-solib-limit
10568 @item show auto-solib-limit
10569 Display the current autoloading size threshold, in megabytes.
10572 Shared libraries are also supported in many cross or remote debugging
10573 configurations. A copy of the target's libraries need to be present on the
10574 host system; they need to be the same as the target libraries, although the
10575 copies on the target can be stripped as long as the copies on the host are
10578 You need to tell @value{GDBN} where the target libraries are, so that it can
10579 load the correct copies---otherwise, it may try to load the host's libraries.
10580 @value{GDBN} has two variables to specify the search directories for target
10584 @kindex set solib-absolute-prefix
10585 @item set solib-absolute-prefix @var{path}
10586 If this variable is set, @var{path} will be used as a prefix for any
10587 absolute shared library paths; many runtime loaders store the absolute
10588 paths to the shared library in the target program's memory. If you use
10589 @samp{solib-absolute-prefix} to find shared libraries, they need to be laid
10590 out in the same way that they are on the target, with e.g.@: a
10591 @file{/usr/lib} hierarchy under @var{path}.
10593 You can set the default value of @samp{solib-absolute-prefix} by using the
10594 configure-time @samp{--with-sysroot} option.
10596 @kindex show solib-absolute-prefix
10597 @item show solib-absolute-prefix
10598 Display the current shared library prefix.
10600 @kindex set solib-search-path
10601 @item set solib-search-path @var{path}
10602 If this variable is set, @var{path} is a colon-separated list of directories
10603 to search for shared libraries. @samp{solib-search-path} is used after
10604 @samp{solib-absolute-prefix} fails to locate the library, or if the path to
10605 the library is relative instead of absolute. If you want to use
10606 @samp{solib-search-path} instead of @samp{solib-absolute-prefix}, be sure to
10607 set @samp{solib-absolute-prefix} to a nonexistant directory to prevent
10608 @value{GDBN} from finding your host's libraries.
10610 @kindex show solib-search-path
10611 @item show solib-search-path
10612 Display the current shared library search path.
10616 @node Separate Debug Files
10617 @section Debugging Information in Separate Files
10618 @cindex separate debugging information files
10619 @cindex debugging information in separate files
10620 @cindex @file{.debug} subdirectories
10621 @cindex debugging information directory, global
10622 @cindex global debugging information directory
10624 @value{GDBN} allows you to put a program's debugging information in a
10625 file separate from the executable itself, in a way that allows
10626 @value{GDBN} to find and load the debugging information automatically.
10627 Since debugging information can be very large --- sometimes larger
10628 than the executable code itself --- some systems distribute debugging
10629 information for their executables in separate files, which users can
10630 install only when they need to debug a problem.
10632 If an executable's debugging information has been extracted to a
10633 separate file, the executable should contain a @dfn{debug link} giving
10634 the name of the debugging information file (with no directory
10635 components), and a checksum of its contents. (The exact form of a
10636 debug link is described below.) If the full name of the directory
10637 containing the executable is @var{execdir}, and the executable has a
10638 debug link that specifies the name @var{debugfile}, then @value{GDBN}
10639 will automatically search for the debugging information file in three
10644 the directory containing the executable file (that is, it will look
10645 for a file named @file{@var{execdir}/@var{debugfile}},
10647 a subdirectory of that directory named @file{.debug} (that is, the
10648 file @file{@var{execdir}/.debug/@var{debugfile}}, and
10650 a subdirectory of the global debug file directory that includes the
10651 executable's full path, and the name from the link (that is, the file
10652 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
10653 @var{globaldebugdir} is the global debug file directory, and
10654 @var{execdir} has been turned into a relative path).
10657 @value{GDBN} checks under each of these names for a debugging
10658 information file whose checksum matches that given in the link, and
10659 reads the debugging information from the first one it finds.
10661 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
10662 which has a link containing the name @file{ls.debug}, and the global
10663 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
10664 for debug information in @file{/usr/bin/ls.debug},
10665 @file{/usr/bin/.debug/ls.debug}, and
10666 @file{/usr/lib/debug/usr/bin/ls.debug}.
10668 You can set the global debugging info directory's name, and view the
10669 name @value{GDBN} is currently using.
10673 @kindex set debug-file-directory
10674 @item set debug-file-directory @var{directory}
10675 Set the directory which @value{GDBN} searches for separate debugging
10676 information files to @var{directory}.
10678 @kindex show debug-file-directory
10679 @item show debug-file-directory
10680 Show the directory @value{GDBN} searches for separate debugging
10685 @cindex @code{.gnu_debuglink} sections
10686 @cindex debug links
10687 A debug link is a special section of the executable file named
10688 @code{.gnu_debuglink}. The section must contain:
10692 A filename, with any leading directory components removed, followed by
10695 zero to three bytes of padding, as needed to reach the next four-byte
10696 boundary within the section, and
10698 a four-byte CRC checksum, stored in the same endianness used for the
10699 executable file itself. The checksum is computed on the debugging
10700 information file's full contents by the function given below, passing
10701 zero as the @var{crc} argument.
10704 Any executable file format can carry a debug link, as long as it can
10705 contain a section named @code{.gnu_debuglink} with the contents
10708 The debugging information file itself should be an ordinary
10709 executable, containing a full set of linker symbols, sections, and
10710 debugging information. The sections of the debugging information file
10711 should have the same names, addresses and sizes as the original file,
10712 but they need not contain any data --- much like a @code{.bss} section
10713 in an ordinary executable.
10715 As of December 2002, there is no standard GNU utility to produce
10716 separated executable / debugging information file pairs. Ulrich
10717 Drepper's @file{elfutils} package, starting with version 0.53,
10718 contains a version of the @code{strip} command such that the command
10719 @kbd{strip foo -f foo.debug} removes the debugging information from
10720 the executable file @file{foo}, places it in the file
10721 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
10723 Since there are many different ways to compute CRC's (different
10724 polynomials, reversals, byte ordering, etc.), the simplest way to
10725 describe the CRC used in @code{.gnu_debuglink} sections is to give the
10726 complete code for a function that computes it:
10728 @kindex gnu_debuglink_crc32
10731 gnu_debuglink_crc32 (unsigned long crc,
10732 unsigned char *buf, size_t len)
10734 static const unsigned long crc32_table[256] =
10736 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
10737 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
10738 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
10739 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
10740 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
10741 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
10742 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
10743 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
10744 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
10745 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
10746 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
10747 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
10748 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
10749 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
10750 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
10751 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
10752 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
10753 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
10754 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
10755 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
10756 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
10757 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
10758 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
10759 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
10760 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
10761 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
10762 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
10763 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
10764 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
10765 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
10766 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
10767 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
10768 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
10769 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
10770 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
10771 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
10772 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
10773 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
10774 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
10775 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
10776 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
10777 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
10778 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
10779 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
10780 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
10781 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
10782 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
10783 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
10784 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
10785 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
10786 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
10789 unsigned char *end;
10791 crc = ~crc & 0xffffffff;
10792 for (end = buf + len; buf < end; ++buf)
10793 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
10794 return ~crc & 0xffffffff;
10799 @node Symbol Errors
10800 @section Errors reading symbol files
10802 While reading a symbol file, @value{GDBN} occasionally encounters problems,
10803 such as symbol types it does not recognize, or known bugs in compiler
10804 output. By default, @value{GDBN} does not notify you of such problems, since
10805 they are relatively common and primarily of interest to people
10806 debugging compilers. If you are interested in seeing information
10807 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
10808 only one message about each such type of problem, no matter how many
10809 times the problem occurs; or you can ask @value{GDBN} to print more messages,
10810 to see how many times the problems occur, with the @code{set
10811 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
10814 The messages currently printed, and their meanings, include:
10817 @item inner block not inside outer block in @var{symbol}
10819 The symbol information shows where symbol scopes begin and end
10820 (such as at the start of a function or a block of statements). This
10821 error indicates that an inner scope block is not fully contained
10822 in its outer scope blocks.
10824 @value{GDBN} circumvents the problem by treating the inner block as if it had
10825 the same scope as the outer block. In the error message, @var{symbol}
10826 may be shown as ``@code{(don't know)}'' if the outer block is not a
10829 @item block at @var{address} out of order
10831 The symbol information for symbol scope blocks should occur in
10832 order of increasing addresses. This error indicates that it does not
10835 @value{GDBN} does not circumvent this problem, and has trouble
10836 locating symbols in the source file whose symbols it is reading. (You
10837 can often determine what source file is affected by specifying
10838 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
10841 @item bad block start address patched
10843 The symbol information for a symbol scope block has a start address
10844 smaller than the address of the preceding source line. This is known
10845 to occur in the SunOS 4.1.1 (and earlier) C compiler.
10847 @value{GDBN} circumvents the problem by treating the symbol scope block as
10848 starting on the previous source line.
10850 @item bad string table offset in symbol @var{n}
10853 Symbol number @var{n} contains a pointer into the string table which is
10854 larger than the size of the string table.
10856 @value{GDBN} circumvents the problem by considering the symbol to have the
10857 name @code{foo}, which may cause other problems if many symbols end up
10860 @item unknown symbol type @code{0x@var{nn}}
10862 The symbol information contains new data types that @value{GDBN} does
10863 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
10864 uncomprehended information, in hexadecimal.
10866 @value{GDBN} circumvents the error by ignoring this symbol information.
10867 This usually allows you to debug your program, though certain symbols
10868 are not accessible. If you encounter such a problem and feel like
10869 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
10870 on @code{complain}, then go up to the function @code{read_dbx_symtab}
10871 and examine @code{*bufp} to see the symbol.
10873 @item stub type has NULL name
10875 @value{GDBN} could not find the full definition for a struct or class.
10877 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
10878 The symbol information for a C@t{++} member function is missing some
10879 information that recent versions of the compiler should have output for
10882 @item info mismatch between compiler and debugger
10884 @value{GDBN} could not parse a type specification output by the compiler.
10889 @chapter Specifying a Debugging Target
10891 @cindex debugging target
10894 A @dfn{target} is the execution environment occupied by your program.
10896 Often, @value{GDBN} runs in the same host environment as your program;
10897 in that case, the debugging target is specified as a side effect when
10898 you use the @code{file} or @code{core} commands. When you need more
10899 flexibility---for example, running @value{GDBN} on a physically separate
10900 host, or controlling a standalone system over a serial port or a
10901 realtime system over a TCP/IP connection---you can use the @code{target}
10902 command to specify one of the target types configured for @value{GDBN}
10903 (@pxref{Target Commands, ,Commands for managing targets}).
10906 * Active Targets:: Active targets
10907 * Target Commands:: Commands for managing targets
10908 * Byte Order:: Choosing target byte order
10909 * Remote:: Remote debugging
10910 * KOD:: Kernel Object Display
10914 @node Active Targets
10915 @section Active targets
10917 @cindex stacking targets
10918 @cindex active targets
10919 @cindex multiple targets
10921 There are three classes of targets: processes, core files, and
10922 executable files. @value{GDBN} can work concurrently on up to three
10923 active targets, one in each class. This allows you to (for example)
10924 start a process and inspect its activity without abandoning your work on
10927 For example, if you execute @samp{gdb a.out}, then the executable file
10928 @code{a.out} is the only active target. If you designate a core file as
10929 well---presumably from a prior run that crashed and coredumped---then
10930 @value{GDBN} has two active targets and uses them in tandem, looking
10931 first in the corefile target, then in the executable file, to satisfy
10932 requests for memory addresses. (Typically, these two classes of target
10933 are complementary, since core files contain only a program's
10934 read-write memory---variables and so on---plus machine status, while
10935 executable files contain only the program text and initialized data.)
10937 When you type @code{run}, your executable file becomes an active process
10938 target as well. When a process target is active, all @value{GDBN}
10939 commands requesting memory addresses refer to that target; addresses in
10940 an active core file or executable file target are obscured while the
10941 process target is active.
10943 Use the @code{core-file} and @code{exec-file} commands to select a new
10944 core file or executable target (@pxref{Files, ,Commands to specify
10945 files}). To specify as a target a process that is already running, use
10946 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
10949 @node Target Commands
10950 @section Commands for managing targets
10953 @item target @var{type} @var{parameters}
10954 Connects the @value{GDBN} host environment to a target machine or
10955 process. A target is typically a protocol for talking to debugging
10956 facilities. You use the argument @var{type} to specify the type or
10957 protocol of the target machine.
10959 Further @var{parameters} are interpreted by the target protocol, but
10960 typically include things like device names or host names to connect
10961 with, process numbers, and baud rates.
10963 The @code{target} command does not repeat if you press @key{RET} again
10964 after executing the command.
10966 @kindex help target
10968 Displays the names of all targets available. To display targets
10969 currently selected, use either @code{info target} or @code{info files}
10970 (@pxref{Files, ,Commands to specify files}).
10972 @item help target @var{name}
10973 Describe a particular target, including any parameters necessary to
10976 @kindex set gnutarget
10977 @item set gnutarget @var{args}
10978 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
10979 knows whether it is reading an @dfn{executable},
10980 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
10981 with the @code{set gnutarget} command. Unlike most @code{target} commands,
10982 with @code{gnutarget} the @code{target} refers to a program, not a machine.
10985 @emph{Warning:} To specify a file format with @code{set gnutarget},
10986 you must know the actual BFD name.
10990 @xref{Files, , Commands to specify files}.
10992 @kindex show gnutarget
10993 @item show gnutarget
10994 Use the @code{show gnutarget} command to display what file format
10995 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
10996 @value{GDBN} will determine the file format for each file automatically,
10997 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
11000 @cindex common targets
11001 Here are some common targets (available, or not, depending on the GDB
11006 @item target exec @var{program}
11007 @cindex executable file target
11008 An executable file. @samp{target exec @var{program}} is the same as
11009 @samp{exec-file @var{program}}.
11011 @item target core @var{filename}
11012 @cindex core dump file target
11013 A core dump file. @samp{target core @var{filename}} is the same as
11014 @samp{core-file @var{filename}}.
11016 @item target remote @var{dev}
11017 @cindex remote target
11018 Remote serial target in GDB-specific protocol. The argument @var{dev}
11019 specifies what serial device to use for the connection (e.g.
11020 @file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote}
11021 supports the @code{load} command. This is only useful if you have
11022 some other way of getting the stub to the target system, and you can put
11023 it somewhere in memory where it won't get clobbered by the download.
11026 @cindex built-in simulator target
11027 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
11035 works; however, you cannot assume that a specific memory map, device
11036 drivers, or even basic I/O is available, although some simulators do
11037 provide these. For info about any processor-specific simulator details,
11038 see the appropriate section in @ref{Embedded Processors, ,Embedded
11043 Some configurations may include these targets as well:
11047 @item target nrom @var{dev}
11048 @cindex NetROM ROM emulator target
11049 NetROM ROM emulator. This target only supports downloading.
11053 Different targets are available on different configurations of @value{GDBN};
11054 your configuration may have more or fewer targets.
11056 Many remote targets require you to download the executable's code
11057 once you've successfully established a connection.
11061 @kindex load @var{filename}
11062 @item load @var{filename}
11063 Depending on what remote debugging facilities are configured into
11064 @value{GDBN}, the @code{load} command may be available. Where it exists, it
11065 is meant to make @var{filename} (an executable) available for debugging
11066 on the remote system---by downloading, or dynamic linking, for example.
11067 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
11068 the @code{add-symbol-file} command.
11070 If your @value{GDBN} does not have a @code{load} command, attempting to
11071 execute it gets the error message ``@code{You can't do that when your
11072 target is @dots{}}''
11074 The file is loaded at whatever address is specified in the executable.
11075 For some object file formats, you can specify the load address when you
11076 link the program; for other formats, like a.out, the object file format
11077 specifies a fixed address.
11078 @c FIXME! This would be a good place for an xref to the GNU linker doc.
11080 @code{load} does not repeat if you press @key{RET} again after using it.
11084 @section Choosing target byte order
11086 @cindex choosing target byte order
11087 @cindex target byte order
11089 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
11090 offer the ability to run either big-endian or little-endian byte
11091 orders. Usually the executable or symbol will include a bit to
11092 designate the endian-ness, and you will not need to worry about
11093 which to use. However, you may still find it useful to adjust
11094 @value{GDBN}'s idea of processor endian-ness manually.
11098 @item set endian big
11099 Instruct @value{GDBN} to assume the target is big-endian.
11101 @item set endian little
11102 Instruct @value{GDBN} to assume the target is little-endian.
11104 @item set endian auto
11105 Instruct @value{GDBN} to use the byte order associated with the
11109 Display @value{GDBN}'s current idea of the target byte order.
11113 Note that these commands merely adjust interpretation of symbolic
11114 data on the host, and that they have absolutely no effect on the
11118 @section Remote debugging
11119 @cindex remote debugging
11121 If you are trying to debug a program running on a machine that cannot run
11122 @value{GDBN} in the usual way, it is often useful to use remote debugging.
11123 For example, you might use remote debugging on an operating system kernel,
11124 or on a small system which does not have a general purpose operating system
11125 powerful enough to run a full-featured debugger.
11127 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
11128 to make this work with particular debugging targets. In addition,
11129 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
11130 but not specific to any particular target system) which you can use if you
11131 write the remote stubs---the code that runs on the remote system to
11132 communicate with @value{GDBN}.
11134 Other remote targets may be available in your
11135 configuration of @value{GDBN}; use @code{help target} to list them.
11138 @section Kernel Object Display
11139 @cindex kernel object display
11142 Some targets support kernel object display. Using this facility,
11143 @value{GDBN} communicates specially with the underlying operating system
11144 and can display information about operating system-level objects such as
11145 mutexes and other synchronization objects. Exactly which objects can be
11146 displayed is determined on a per-OS basis.
11149 Use the @code{set os} command to set the operating system. This tells
11150 @value{GDBN} which kernel object display module to initialize:
11153 (@value{GDBP}) set os cisco
11157 The associated command @code{show os} displays the operating system
11158 set with the @code{set os} command; if no operating system has been
11159 set, @code{show os} will display an empty string @samp{""}.
11161 If @code{set os} succeeds, @value{GDBN} will display some information
11162 about the operating system, and will create a new @code{info} command
11163 which can be used to query the target. The @code{info} command is named
11164 after the operating system:
11168 (@value{GDBP}) info cisco
11169 List of Cisco Kernel Objects
11171 any Any and all objects
11174 Further subcommands can be used to query about particular objects known
11177 There is currently no way to determine whether a given operating
11178 system is supported other than to try setting it with @kbd{set os
11179 @var{name}}, where @var{name} is the name of the operating system you
11183 @node Remote Debugging
11184 @chapter Debugging remote programs
11187 * Connecting:: Connecting to a remote target
11188 * Server:: Using the gdbserver program
11189 * NetWare:: Using the gdbserve.nlm program
11190 * Remote configuration:: Remote configuration
11191 * remote stub:: Implementing a remote stub
11195 @section Connecting to a remote target
11197 On the @value{GDBN} host machine, you will need an unstripped copy of
11198 your program, since @value{GDBN} needs symobl and debugging information.
11199 Start up @value{GDBN} as usual, using the name of the local copy of your
11200 program as the first argument.
11202 @cindex serial line, @code{target remote}
11203 If you're using a serial line, you may want to give @value{GDBN} the
11204 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
11205 before the @code{target} command.
11207 After that, use @code{target remote} to establish communications with
11208 the target machine. Its argument specifies how to communicate---either
11209 via a devicename attached to a direct serial line, or a TCP or UDP port
11210 (possibly to a terminal server which in turn has a serial line to the
11211 target). For example, to use a serial line connected to the device
11212 named @file{/dev/ttyb}:
11215 target remote /dev/ttyb
11218 @cindex TCP port, @code{target remote}
11219 To use a TCP connection, use an argument of the form
11220 @code{@var{host}:@var{port}} or @code{tcp:@var{host}:@var{port}}.
11221 For example, to connect to port 2828 on a
11222 terminal server named @code{manyfarms}:
11225 target remote manyfarms:2828
11228 If your remote target is actually running on the same machine as
11229 your debugger session (e.g.@: a simulator of your target running on
11230 the same host), you can omit the hostname. For example, to connect
11231 to port 1234 on your local machine:
11234 target remote :1234
11238 Note that the colon is still required here.
11240 @cindex UDP port, @code{target remote}
11241 To use a UDP connection, use an argument of the form
11242 @code{udp:@var{host}:@var{port}}. For example, to connect to UDP port 2828
11243 on a terminal server named @code{manyfarms}:
11246 target remote udp:manyfarms:2828
11249 When using a UDP connection for remote debugging, you should keep in mind
11250 that the `U' stands for ``Unreliable''. UDP can silently drop packets on
11251 busy or unreliable networks, which will cause havoc with your debugging
11254 Now you can use all the usual commands to examine and change data and to
11255 step and continue the remote program.
11257 @cindex interrupting remote programs
11258 @cindex remote programs, interrupting
11259 Whenever @value{GDBN} is waiting for the remote program, if you type the
11260 interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
11261 program. This may or may not succeed, depending in part on the hardware
11262 and the serial drivers the remote system uses. If you type the
11263 interrupt character once again, @value{GDBN} displays this prompt:
11266 Interrupted while waiting for the program.
11267 Give up (and stop debugging it)? (y or n)
11270 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
11271 (If you decide you want to try again later, you can use @samp{target
11272 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
11273 goes back to waiting.
11276 @kindex detach (remote)
11278 When you have finished debugging the remote program, you can use the
11279 @code{detach} command to release it from @value{GDBN} control.
11280 Detaching from the target normally resumes its execution, but the results
11281 will depend on your particular remote stub. After the @code{detach}
11282 command, @value{GDBN} is free to connect to another target.
11286 The @code{disconnect} command behaves like @code{detach}, except that
11287 the target is generally not resumed. It will wait for @value{GDBN}
11288 (this instance or another one) to connect and continue debugging. After
11289 the @code{disconnect} command, @value{GDBN} is again free to connect to
11294 @section Using the @code{gdbserver} program
11297 @cindex remote connection without stubs
11298 @code{gdbserver} is a control program for Unix-like systems, which
11299 allows you to connect your program with a remote @value{GDBN} via
11300 @code{target remote}---but without linking in the usual debugging stub.
11302 @code{gdbserver} is not a complete replacement for the debugging stubs,
11303 because it requires essentially the same operating-system facilities
11304 that @value{GDBN} itself does. In fact, a system that can run
11305 @code{gdbserver} to connect to a remote @value{GDBN} could also run
11306 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
11307 because it is a much smaller program than @value{GDBN} itself. It is
11308 also easier to port than all of @value{GDBN}, so you may be able to get
11309 started more quickly on a new system by using @code{gdbserver}.
11310 Finally, if you develop code for real-time systems, you may find that
11311 the tradeoffs involved in real-time operation make it more convenient to
11312 do as much development work as possible on another system, for example
11313 by cross-compiling. You can use @code{gdbserver} to make a similar
11314 choice for debugging.
11316 @value{GDBN} and @code{gdbserver} communicate via either a serial line
11317 or a TCP connection, using the standard @value{GDBN} remote serial
11321 @item On the target machine,
11322 you need to have a copy of the program you want to debug.
11323 @code{gdbserver} does not need your program's symbol table, so you can
11324 strip the program if necessary to save space. @value{GDBN} on the host
11325 system does all the symbol handling.
11327 To use the server, you must tell it how to communicate with @value{GDBN};
11328 the name of your program; and the arguments for your program. The usual
11332 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
11335 @var{comm} is either a device name (to use a serial line) or a TCP
11336 hostname and portnumber. For example, to debug Emacs with the argument
11337 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
11341 target> gdbserver /dev/com1 emacs foo.txt
11344 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
11347 To use a TCP connection instead of a serial line:
11350 target> gdbserver host:2345 emacs foo.txt
11353 The only difference from the previous example is the first argument,
11354 specifying that you are communicating with the host @value{GDBN} via
11355 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
11356 expect a TCP connection from machine @samp{host} to local TCP port 2345.
11357 (Currently, the @samp{host} part is ignored.) You can choose any number
11358 you want for the port number as long as it does not conflict with any
11359 TCP ports already in use on the target system (for example, @code{23} is
11360 reserved for @code{telnet}).@footnote{If you choose a port number that
11361 conflicts with another service, @code{gdbserver} prints an error message
11362 and exits.} You must use the same port number with the host @value{GDBN}
11363 @code{target remote} command.
11365 On some targets, @code{gdbserver} can also attach to running programs.
11366 This is accomplished via the @code{--attach} argument. The syntax is:
11369 target> gdbserver @var{comm} --attach @var{pid}
11372 @var{pid} is the process ID of a currently running process. It isn't necessary
11373 to point @code{gdbserver} at a binary for the running process.
11376 @cindex attach to a program by name
11377 You can debug processes by name instead of process ID if your target has the
11378 @code{pidof} utility:
11381 target> gdbserver @var{comm} --attach `pidof @var{PROGRAM}`
11384 In case more than one copy of @var{PROGRAM} is running, or @var{PROGRAM}
11385 has multiple threads, most versions of @code{pidof} support the
11386 @code{-s} option to only return the first process ID.
11388 @item On the host machine,
11389 connect to your target (@pxref{Connecting,,Connecting to a remote target}).
11390 For TCP connections, you must start up @code{gdbserver} prior to using
11391 the @code{target remote} command. Otherwise you may get an error whose
11392 text depends on the host system, but which usually looks something like
11393 @samp{Connection refused}. You don't need to use the @code{load}
11394 command in @value{GDBN} when using gdbserver, since the program is
11395 already on the target.
11400 @section Using the @code{gdbserve.nlm} program
11402 @kindex gdbserve.nlm
11403 @code{gdbserve.nlm} is a control program for NetWare systems, which
11404 allows you to connect your program with a remote @value{GDBN} via
11405 @code{target remote}.
11407 @value{GDBN} and @code{gdbserve.nlm} communicate via a serial line,
11408 using the standard @value{GDBN} remote serial protocol.
11411 @item On the target machine,
11412 you need to have a copy of the program you want to debug.
11413 @code{gdbserve.nlm} does not need your program's symbol table, so you
11414 can strip the program if necessary to save space. @value{GDBN} on the
11415 host system does all the symbol handling.
11417 To use the server, you must tell it how to communicate with
11418 @value{GDBN}; the name of your program; and the arguments for your
11419 program. The syntax is:
11422 load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ]
11423 [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ]
11426 @var{board} and @var{port} specify the serial line; @var{baud} specifies
11427 the baud rate used by the connection. @var{port} and @var{node} default
11428 to 0, @var{baud} defaults to 9600@dmn{bps}.
11430 For example, to debug Emacs with the argument @samp{foo.txt}and
11431 communicate with @value{GDBN} over serial port number 2 or board 1
11432 using a 19200@dmn{bps} connection:
11435 load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
11439 On the @value{GDBN} host machine, connect to your target (@pxref{Connecting,,
11440 Connecting to a remote target}).
11444 @node Remote configuration
11445 @section Remote configuration
11447 The following configuration options are available when debugging remote
11451 @kindex set remote hardware-watchpoint-limit
11452 @kindex set remote hardware-breakpoint-limit
11453 @anchor{set remote hardware-watchpoint-limit}
11454 @anchor{set remote hardware-breakpoint-limit}
11455 @item set remote hardware-watchpoint-limit @var{limit}
11456 @itemx set remote hardware-breakpoint-limit @var{limit}
11457 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
11458 watchpoints. A limit of -1, the default, is treated as unlimited.
11462 @section Implementing a remote stub
11464 @cindex debugging stub, example
11465 @cindex remote stub, example
11466 @cindex stub example, remote debugging
11467 The stub files provided with @value{GDBN} implement the target side of the
11468 communication protocol, and the @value{GDBN} side is implemented in the
11469 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
11470 these subroutines to communicate, and ignore the details. (If you're
11471 implementing your own stub file, you can still ignore the details: start
11472 with one of the existing stub files. @file{sparc-stub.c} is the best
11473 organized, and therefore the easiest to read.)
11475 @cindex remote serial debugging, overview
11476 To debug a program running on another machine (the debugging
11477 @dfn{target} machine), you must first arrange for all the usual
11478 prerequisites for the program to run by itself. For example, for a C
11483 A startup routine to set up the C runtime environment; these usually
11484 have a name like @file{crt0}. The startup routine may be supplied by
11485 your hardware supplier, or you may have to write your own.
11488 A C subroutine library to support your program's
11489 subroutine calls, notably managing input and output.
11492 A way of getting your program to the other machine---for example, a
11493 download program. These are often supplied by the hardware
11494 manufacturer, but you may have to write your own from hardware
11498 The next step is to arrange for your program to use a serial port to
11499 communicate with the machine where @value{GDBN} is running (the @dfn{host}
11500 machine). In general terms, the scheme looks like this:
11504 @value{GDBN} already understands how to use this protocol; when everything
11505 else is set up, you can simply use the @samp{target remote} command
11506 (@pxref{Targets,,Specifying a Debugging Target}).
11508 @item On the target,
11509 you must link with your program a few special-purpose subroutines that
11510 implement the @value{GDBN} remote serial protocol. The file containing these
11511 subroutines is called a @dfn{debugging stub}.
11513 On certain remote targets, you can use an auxiliary program
11514 @code{gdbserver} instead of linking a stub into your program.
11515 @xref{Server,,Using the @code{gdbserver} program}, for details.
11518 The debugging stub is specific to the architecture of the remote
11519 machine; for example, use @file{sparc-stub.c} to debug programs on
11522 @cindex remote serial stub list
11523 These working remote stubs are distributed with @value{GDBN}:
11528 @cindex @file{i386-stub.c}
11531 For Intel 386 and compatible architectures.
11534 @cindex @file{m68k-stub.c}
11535 @cindex Motorola 680x0
11537 For Motorola 680x0 architectures.
11540 @cindex @file{sh-stub.c}
11543 For Renesas SH architectures.
11546 @cindex @file{sparc-stub.c}
11548 For @sc{sparc} architectures.
11550 @item sparcl-stub.c
11551 @cindex @file{sparcl-stub.c}
11554 For Fujitsu @sc{sparclite} architectures.
11558 The @file{README} file in the @value{GDBN} distribution may list other
11559 recently added stubs.
11562 * Stub Contents:: What the stub can do for you
11563 * Bootstrapping:: What you must do for the stub
11564 * Debug Session:: Putting it all together
11567 @node Stub Contents
11568 @subsection What the stub can do for you
11570 @cindex remote serial stub
11571 The debugging stub for your architecture supplies these three
11575 @item set_debug_traps
11576 @findex set_debug_traps
11577 @cindex remote serial stub, initialization
11578 This routine arranges for @code{handle_exception} to run when your
11579 program stops. You must call this subroutine explicitly near the
11580 beginning of your program.
11582 @item handle_exception
11583 @findex handle_exception
11584 @cindex remote serial stub, main routine
11585 This is the central workhorse, but your program never calls it
11586 explicitly---the setup code arranges for @code{handle_exception} to
11587 run when a trap is triggered.
11589 @code{handle_exception} takes control when your program stops during
11590 execution (for example, on a breakpoint), and mediates communications
11591 with @value{GDBN} on the host machine. This is where the communications
11592 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
11593 representative on the target machine. It begins by sending summary
11594 information on the state of your program, then continues to execute,
11595 retrieving and transmitting any information @value{GDBN} needs, until you
11596 execute a @value{GDBN} command that makes your program resume; at that point,
11597 @code{handle_exception} returns control to your own code on the target
11601 @cindex @code{breakpoint} subroutine, remote
11602 Use this auxiliary subroutine to make your program contain a
11603 breakpoint. Depending on the particular situation, this may be the only
11604 way for @value{GDBN} to get control. For instance, if your target
11605 machine has some sort of interrupt button, you won't need to call this;
11606 pressing the interrupt button transfers control to
11607 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
11608 simply receiving characters on the serial port may also trigger a trap;
11609 again, in that situation, you don't need to call @code{breakpoint} from
11610 your own program---simply running @samp{target remote} from the host
11611 @value{GDBN} session gets control.
11613 Call @code{breakpoint} if none of these is true, or if you simply want
11614 to make certain your program stops at a predetermined point for the
11615 start of your debugging session.
11618 @node Bootstrapping
11619 @subsection What you must do for the stub
11621 @cindex remote stub, support routines
11622 The debugging stubs that come with @value{GDBN} are set up for a particular
11623 chip architecture, but they have no information about the rest of your
11624 debugging target machine.
11626 First of all you need to tell the stub how to communicate with the
11630 @item int getDebugChar()
11631 @findex getDebugChar
11632 Write this subroutine to read a single character from the serial port.
11633 It may be identical to @code{getchar} for your target system; a
11634 different name is used to allow you to distinguish the two if you wish.
11636 @item void putDebugChar(int)
11637 @findex putDebugChar
11638 Write this subroutine to write a single character to the serial port.
11639 It may be identical to @code{putchar} for your target system; a
11640 different name is used to allow you to distinguish the two if you wish.
11643 @cindex control C, and remote debugging
11644 @cindex interrupting remote targets
11645 If you want @value{GDBN} to be able to stop your program while it is
11646 running, you need to use an interrupt-driven serial driver, and arrange
11647 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
11648 character). That is the character which @value{GDBN} uses to tell the
11649 remote system to stop.
11651 Getting the debugging target to return the proper status to @value{GDBN}
11652 probably requires changes to the standard stub; one quick and dirty way
11653 is to just execute a breakpoint instruction (the ``dirty'' part is that
11654 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
11656 Other routines you need to supply are:
11659 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
11660 @findex exceptionHandler
11661 Write this function to install @var{exception_address} in the exception
11662 handling tables. You need to do this because the stub does not have any
11663 way of knowing what the exception handling tables on your target system
11664 are like (for example, the processor's table might be in @sc{rom},
11665 containing entries which point to a table in @sc{ram}).
11666 @var{exception_number} is the exception number which should be changed;
11667 its meaning is architecture-dependent (for example, different numbers
11668 might represent divide by zero, misaligned access, etc). When this
11669 exception occurs, control should be transferred directly to
11670 @var{exception_address}, and the processor state (stack, registers,
11671 and so on) should be just as it is when a processor exception occurs. So if
11672 you want to use a jump instruction to reach @var{exception_address}, it
11673 should be a simple jump, not a jump to subroutine.
11675 For the 386, @var{exception_address} should be installed as an interrupt
11676 gate so that interrupts are masked while the handler runs. The gate
11677 should be at privilege level 0 (the most privileged level). The
11678 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
11679 help from @code{exceptionHandler}.
11681 @item void flush_i_cache()
11682 @findex flush_i_cache
11683 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
11684 instruction cache, if any, on your target machine. If there is no
11685 instruction cache, this subroutine may be a no-op.
11687 On target machines that have instruction caches, @value{GDBN} requires this
11688 function to make certain that the state of your program is stable.
11692 You must also make sure this library routine is available:
11695 @item void *memset(void *, int, int)
11697 This is the standard library function @code{memset} that sets an area of
11698 memory to a known value. If you have one of the free versions of
11699 @code{libc.a}, @code{memset} can be found there; otherwise, you must
11700 either obtain it from your hardware manufacturer, or write your own.
11703 If you do not use the GNU C compiler, you may need other standard
11704 library subroutines as well; this varies from one stub to another,
11705 but in general the stubs are likely to use any of the common library
11706 subroutines which @code{@value{GCC}} generates as inline code.
11709 @node Debug Session
11710 @subsection Putting it all together
11712 @cindex remote serial debugging summary
11713 In summary, when your program is ready to debug, you must follow these
11718 Make sure you have defined the supporting low-level routines
11719 (@pxref{Bootstrapping,,What you must do for the stub}):
11721 @code{getDebugChar}, @code{putDebugChar},
11722 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
11726 Insert these lines near the top of your program:
11734 For the 680x0 stub only, you need to provide a variable called
11735 @code{exceptionHook}. Normally you just use:
11738 void (*exceptionHook)() = 0;
11742 but if before calling @code{set_debug_traps}, you set it to point to a
11743 function in your program, that function is called when
11744 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
11745 error). The function indicated by @code{exceptionHook} is called with
11746 one parameter: an @code{int} which is the exception number.
11749 Compile and link together: your program, the @value{GDBN} debugging stub for
11750 your target architecture, and the supporting subroutines.
11753 Make sure you have a serial connection between your target machine and
11754 the @value{GDBN} host, and identify the serial port on the host.
11757 @c The "remote" target now provides a `load' command, so we should
11758 @c document that. FIXME.
11759 Download your program to your target machine (or get it there by
11760 whatever means the manufacturer provides), and start it.
11763 Start @value{GDBN} on the host, and connect to the target
11764 (@pxref{Connecting,,Connecting to a remote target}).
11768 @node Configurations
11769 @chapter Configuration-Specific Information
11771 While nearly all @value{GDBN} commands are available for all native and
11772 cross versions of the debugger, there are some exceptions. This chapter
11773 describes things that are only available in certain configurations.
11775 There are three major categories of configurations: native
11776 configurations, where the host and target are the same, embedded
11777 operating system configurations, which are usually the same for several
11778 different processor architectures, and bare embedded processors, which
11779 are quite different from each other.
11784 * Embedded Processors::
11791 This section describes details specific to particular native
11796 * BSD libkvm Interface:: Debugging BSD kernel memory images
11797 * SVR4 Process Information:: SVR4 process information
11798 * DJGPP Native:: Features specific to the DJGPP port
11799 * Cygwin Native:: Features specific to the Cygwin port
11805 On HP-UX systems, if you refer to a function or variable name that
11806 begins with a dollar sign, @value{GDBN} searches for a user or system
11807 name first, before it searches for a convenience variable.
11809 @node BSD libkvm Interface
11810 @subsection BSD libkvm Interface
11813 @cindex kernel memory image
11814 @cindex kernel crash dump
11816 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
11817 interface that provides a uniform interface for accessing kernel virtual
11818 memory images, including live systems and crash dumps. @value{GDBN}
11819 uses this interface to allow you to debug live kernels and kernel crash
11820 dumps on many native BSD configurations. This is implemented as a
11821 special @code{kvm} debugging target. For debugging a live system, load
11822 the currently running kernel into @value{GDBN} and connect to the
11826 (@value{GDBP}) @b{target kvm}
11829 For debugging crash dumps, provide the file name of the crash dump as an
11833 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
11836 Once connected to the @code{kvm} target, the following commands are
11842 Set current context from pcb address.
11845 Set current context from proc address. This command isn't available on
11846 modern FreeBSD systems.
11849 @node SVR4 Process Information
11850 @subsection SVR4 process information
11852 @cindex examine process image
11853 @cindex process info via @file{/proc}
11855 Many versions of SVR4 and compatible systems provide a facility called
11856 @samp{/proc} that can be used to examine the image of a running
11857 process using file-system subroutines. If @value{GDBN} is configured
11858 for an operating system with this facility, the command @code{info
11859 proc} is available to report information about the process running
11860 your program, or about any process running on your system. @code{info
11861 proc} works only on SVR4 systems that include the @code{procfs} code.
11862 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
11863 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
11869 @itemx info proc @var{process-id}
11870 Summarize available information about any running process. If a
11871 process ID is specified by @var{process-id}, display information about
11872 that process; otherwise display information about the program being
11873 debugged. The summary includes the debugged process ID, the command
11874 line used to invoke it, its current working directory, and its
11875 executable file's absolute file name.
11877 On some systems, @var{process-id} can be of the form
11878 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
11879 within a process. If the optional @var{pid} part is missing, it means
11880 a thread from the process being debugged (the leading @samp{/} still
11881 needs to be present, or else @value{GDBN} will interpret the number as
11882 a process ID rather than a thread ID).
11884 @item info proc mappings
11885 @cindex memory address space mappings
11886 Report the memory address space ranges accessible in the program, with
11887 information on whether the process has read, write, or execute access
11888 rights to each range. On @sc{gnu}/Linux systems, each memory range
11889 includes the object file which is mapped to that range, instead of the
11890 memory access rights to that range.
11892 @item info proc stat
11893 @itemx info proc status
11894 @cindex process detailed status information
11895 These subcommands are specific to @sc{gnu}/Linux systems. They show
11896 the process-related information, including the user ID and group ID;
11897 how many threads are there in the process; its virtual memory usage;
11898 the signals that are pending, blocked, and ignored; its TTY; its
11899 consumption of system and user time; its stack size; its @samp{nice}
11900 value; etc. For more information, see the @samp{proc(5)} man page
11901 (type @kbd{man 5 proc} from your shell prompt).
11903 @item info proc all
11904 Show all the information about the process described under all of the
11905 above @code{info proc} subcommands.
11908 @comment These sub-options of 'info proc' were not included when
11909 @comment procfs.c was re-written. Keep their descriptions around
11910 @comment against the day when someone finds the time to put them back in.
11911 @kindex info proc times
11912 @item info proc times
11913 Starting time, user CPU time, and system CPU time for your program and
11916 @kindex info proc id
11918 Report on the process IDs related to your program: its own process ID,
11919 the ID of its parent, the process group ID, and the session ID.
11924 @subsection Features for Debugging @sc{djgpp} Programs
11925 @cindex @sc{djgpp} debugging
11926 @cindex native @sc{djgpp} debugging
11927 @cindex MS-DOS-specific commands
11929 @sc{djgpp} is the port of @sc{gnu} development tools to MS-DOS and
11930 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
11931 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
11932 top of real-mode DOS systems and their emulations.
11934 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
11935 defines a few commands specific to the @sc{djgpp} port. This
11936 subsection describes those commands.
11941 This is a prefix of @sc{djgpp}-specific commands which print
11942 information about the target system and important OS structures.
11945 @cindex MS-DOS system info
11946 @cindex free memory information (MS-DOS)
11947 @item info dos sysinfo
11948 This command displays assorted information about the underlying
11949 platform: the CPU type and features, the OS version and flavor, the
11950 DPMI version, and the available conventional and DPMI memory.
11955 @cindex segment descriptor tables
11956 @cindex descriptor tables display
11958 @itemx info dos ldt
11959 @itemx info dos idt
11960 These 3 commands display entries from, respectively, Global, Local,
11961 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
11962 tables are data structures which store a descriptor for each segment
11963 that is currently in use. The segment's selector is an index into a
11964 descriptor table; the table entry for that index holds the
11965 descriptor's base address and limit, and its attributes and access
11968 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
11969 segment (used for both data and the stack), and a DOS segment (which
11970 allows access to DOS/BIOS data structures and absolute addresses in
11971 conventional memory). However, the DPMI host will usually define
11972 additional segments in order to support the DPMI environment.
11974 @cindex garbled pointers
11975 These commands allow to display entries from the descriptor tables.
11976 Without an argument, all entries from the specified table are
11977 displayed. An argument, which should be an integer expression, means
11978 display a single entry whose index is given by the argument. For
11979 example, here's a convenient way to display information about the
11980 debugged program's data segment:
11983 @exdent @code{(@value{GDBP}) info dos ldt $ds}
11984 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
11988 This comes in handy when you want to see whether a pointer is outside
11989 the data segment's limit (i.e.@: @dfn{garbled}).
11991 @cindex page tables display (MS-DOS)
11993 @itemx info dos pte
11994 These two commands display entries from, respectively, the Page
11995 Directory and the Page Tables. Page Directories and Page Tables are
11996 data structures which control how virtual memory addresses are mapped
11997 into physical addresses. A Page Table includes an entry for every
11998 page of memory that is mapped into the program's address space; there
11999 may be several Page Tables, each one holding up to 4096 entries. A
12000 Page Directory has up to 4096 entries, one each for every Page Table
12001 that is currently in use.
12003 Without an argument, @kbd{info dos pde} displays the entire Page
12004 Directory, and @kbd{info dos pte} displays all the entries in all of
12005 the Page Tables. An argument, an integer expression, given to the
12006 @kbd{info dos pde} command means display only that entry from the Page
12007 Directory table. An argument given to the @kbd{info dos pte} command
12008 means display entries from a single Page Table, the one pointed to by
12009 the specified entry in the Page Directory.
12011 @cindex direct memory access (DMA) on MS-DOS
12012 These commands are useful when your program uses @dfn{DMA} (Direct
12013 Memory Access), which needs physical addresses to program the DMA
12016 These commands are supported only with some DPMI servers.
12018 @cindex physical address from linear address
12019 @item info dos address-pte @var{addr}
12020 This command displays the Page Table entry for a specified linear
12021 address. The argument linear address @var{addr} should already have the
12022 appropriate segment's base address added to it, because this command
12023 accepts addresses which may belong to @emph{any} segment. For
12024 example, here's how to display the Page Table entry for the page where
12025 the variable @code{i} is stored:
12028 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
12029 @exdent @code{Page Table entry for address 0x11a00d30:}
12030 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
12034 This says that @code{i} is stored at offset @code{0xd30} from the page
12035 whose physical base address is @code{0x02698000}, and prints all the
12036 attributes of that page.
12038 Note that you must cast the addresses of variables to a @code{char *},
12039 since otherwise the value of @code{__djgpp_base_address}, the base
12040 address of all variables and functions in a @sc{djgpp} program, will
12041 be added using the rules of C pointer arithmetics: if @code{i} is
12042 declared an @code{int}, @value{GDBN} will add 4 times the value of
12043 @code{__djgpp_base_address} to the address of @code{i}.
12045 Here's another example, it displays the Page Table entry for the
12049 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
12050 @exdent @code{Page Table entry for address 0x29110:}
12051 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
12055 (The @code{+ 3} offset is because the transfer buffer's address is the
12056 3rd member of the @code{_go32_info_block} structure.) The output of
12057 this command clearly shows that addresses in conventional memory are
12058 mapped 1:1, i.e.@: the physical and linear addresses are identical.
12060 This command is supported only with some DPMI servers.
12063 @node Cygwin Native
12064 @subsection Features for Debugging MS Windows PE executables
12065 @cindex MS Windows debugging
12066 @cindex native Cygwin debugging
12067 @cindex Cygwin-specific commands
12069 @value{GDBN} supports native debugging of MS Windows programs, including
12070 DLLs with and without symbolic debugging information. There are various
12071 additional Cygwin-specific commands, described in this subsection. The
12072 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
12073 that have no debugging symbols.
12079 This is a prefix of MS Windows specific commands which print
12080 information about the target system and important OS structures.
12082 @item info w32 selector
12083 This command displays information returned by
12084 the Win32 API @code{GetThreadSelectorEntry} function.
12085 It takes an optional argument that is evaluated to
12086 a long value to give the information about this given selector.
12087 Without argument, this command displays information
12088 about the the six segment registers.
12092 This is a Cygwin specific alias of info shared.
12094 @kindex dll-symbols
12096 This command loads symbols from a dll similarly to
12097 add-sym command but without the need to specify a base address.
12099 @kindex set new-console
12100 @item set new-console @var{mode}
12101 If @var{mode} is @code{on} the debuggee will
12102 be started in a new console on next start.
12103 If @var{mode} is @code{off}i, the debuggee will
12104 be started in the same console as the debugger.
12106 @kindex show new-console
12107 @item show new-console
12108 Displays whether a new console is used
12109 when the debuggee is started.
12111 @kindex set new-group
12112 @item set new-group @var{mode}
12113 This boolean value controls whether the debuggee should
12114 start a new group or stay in the same group as the debugger.
12115 This affects the way the Windows OS handles
12118 @kindex show new-group
12119 @item show new-group
12120 Displays current value of new-group boolean.
12122 @kindex set debugevents
12123 @item set debugevents
12124 This boolean value adds debug output concerning events seen by the debugger.
12126 @kindex set debugexec
12127 @item set debugexec
12128 This boolean value adds debug output concerning execute events
12129 seen by the debugger.
12131 @kindex set debugexceptions
12132 @item set debugexceptions
12133 This boolean value adds debug ouptut concerning exception events
12134 seen by the debugger.
12136 @kindex set debugmemory
12137 @item set debugmemory
12138 This boolean value adds debug ouptut concerning memory events
12139 seen by the debugger.
12143 This boolean values specifies whether the debuggee is called
12144 via a shell or directly (default value is on).
12148 Displays if the debuggee will be started with a shell.
12153 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
12156 @node Non-debug DLL symbols
12157 @subsubsection Support for DLLs without debugging symbols
12158 @cindex DLLs with no debugging symbols
12159 @cindex Minimal symbols and DLLs
12161 Very often on windows, some of the DLLs that your program relies on do
12162 not include symbolic debugging information (for example,
12163 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
12164 symbols in a DLL, it relies on the minimal amount of symbolic
12165 information contained in the DLL's export table. This subsubsection
12166 describes working with such symbols, known internally to @value{GDBN} as
12167 ``minimal symbols''.
12169 Note that before the debugged program has started execution, no DLLs
12170 will have been loaded. The easiest way around this problem is simply to
12171 start the program --- either by setting a breakpoint or letting the
12172 program run once to completion. It is also possible to force
12173 @value{GDBN} to load a particular DLL before starting the executable ---
12174 see the shared library information in @pxref{Files} or the
12175 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
12176 explicitly loading symbols from a DLL with no debugging information will
12177 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
12178 which may adversely affect symbol lookup performance.
12180 @subsubsection DLL name prefixes
12182 In keeping with the naming conventions used by the Microsoft debugging
12183 tools, DLL export symbols are made available with a prefix based on the
12184 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
12185 also entered into the symbol table, so @code{CreateFileA} is often
12186 sufficient. In some cases there will be name clashes within a program
12187 (particularly if the executable itself includes full debugging symbols)
12188 necessitating the use of the fully qualified name when referring to the
12189 contents of the DLL. Use single-quotes around the name to avoid the
12190 exclamation mark (``!'') being interpreted as a language operator.
12192 Note that the internal name of the DLL may be all upper-case, even
12193 though the file name of the DLL is lower-case, or vice-versa. Since
12194 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
12195 some confusion. If in doubt, try the @code{info functions} and
12196 @code{info variables} commands or even @code{maint print msymbols} (see
12197 @pxref{Symbols}). Here's an example:
12200 (@value{GDBP}) info function CreateFileA
12201 All functions matching regular expression "CreateFileA":
12203 Non-debugging symbols:
12204 0x77e885f4 CreateFileA
12205 0x77e885f4 KERNEL32!CreateFileA
12209 (@value{GDBP}) info function !
12210 All functions matching regular expression "!":
12212 Non-debugging symbols:
12213 0x6100114c cygwin1!__assert
12214 0x61004034 cygwin1!_dll_crt0@@0
12215 0x61004240 cygwin1!dll_crt0(per_process *)
12219 @subsubsection Working with minimal symbols
12221 Symbols extracted from a DLL's export table do not contain very much
12222 type information. All that @value{GDBN} can do is guess whether a symbol
12223 refers to a function or variable depending on the linker section that
12224 contains the symbol. Also note that the actual contents of the memory
12225 contained in a DLL are not available unless the program is running. This
12226 means that you cannot examine the contents of a variable or disassemble
12227 a function within a DLL without a running program.
12229 Variables are generally treated as pointers and dereferenced
12230 automatically. For this reason, it is often necessary to prefix a
12231 variable name with the address-of operator (``&'') and provide explicit
12232 type information in the command. Here's an example of the type of
12236 (@value{GDBP}) print 'cygwin1!__argv'
12241 (@value{GDBP}) x 'cygwin1!__argv'
12242 0x10021610: "\230y\""
12245 And two possible solutions:
12248 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
12249 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
12253 (@value{GDBP}) x/2x &'cygwin1!__argv'
12254 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
12255 (@value{GDBP}) x/x 0x10021608
12256 0x10021608: 0x0022fd98
12257 (@value{GDBP}) x/s 0x0022fd98
12258 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
12261 Setting a break point within a DLL is possible even before the program
12262 starts execution. However, under these circumstances, @value{GDBN} can't
12263 examine the initial instructions of the function in order to skip the
12264 function's frame set-up code. You can work around this by using ``*&''
12265 to set the breakpoint at a raw memory address:
12268 (@value{GDBP}) break *&'python22!PyOS_Readline'
12269 Breakpoint 1 at 0x1e04eff0
12272 The author of these extensions is not entirely convinced that setting a
12273 break point within a shared DLL like @file{kernel32.dll} is completely
12277 @section Embedded Operating Systems
12279 This section describes configurations involving the debugging of
12280 embedded operating systems that are available for several different
12284 * VxWorks:: Using @value{GDBN} with VxWorks
12287 @value{GDBN} includes the ability to debug programs running on
12288 various real-time operating systems.
12291 @subsection Using @value{GDBN} with VxWorks
12297 @kindex target vxworks
12298 @item target vxworks @var{machinename}
12299 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
12300 is the target system's machine name or IP address.
12304 On VxWorks, @code{load} links @var{filename} dynamically on the
12305 current target system as well as adding its symbols in @value{GDBN}.
12307 @value{GDBN} enables developers to spawn and debug tasks running on networked
12308 VxWorks targets from a Unix host. Already-running tasks spawned from
12309 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
12310 both the Unix host and on the VxWorks target. The program
12311 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
12312 installed with the name @code{vxgdb}, to distinguish it from a
12313 @value{GDBN} for debugging programs on the host itself.)
12316 @item VxWorks-timeout @var{args}
12317 @kindex vxworks-timeout
12318 All VxWorks-based targets now support the option @code{vxworks-timeout}.
12319 This option is set by the user, and @var{args} represents the number of
12320 seconds @value{GDBN} waits for responses to rpc's. You might use this if
12321 your VxWorks target is a slow software simulator or is on the far side
12322 of a thin network line.
12325 The following information on connecting to VxWorks was current when
12326 this manual was produced; newer releases of VxWorks may use revised
12329 @findex INCLUDE_RDB
12330 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
12331 to include the remote debugging interface routines in the VxWorks
12332 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
12333 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
12334 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
12335 source debugging task @code{tRdbTask} when VxWorks is booted. For more
12336 information on configuring and remaking VxWorks, see the manufacturer's
12338 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
12340 Once you have included @file{rdb.a} in your VxWorks system image and set
12341 your Unix execution search path to find @value{GDBN}, you are ready to
12342 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
12343 @code{vxgdb}, depending on your installation).
12345 @value{GDBN} comes up showing the prompt:
12352 * VxWorks Connection:: Connecting to VxWorks
12353 * VxWorks Download:: VxWorks download
12354 * VxWorks Attach:: Running tasks
12357 @node VxWorks Connection
12358 @subsubsection Connecting to VxWorks
12360 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
12361 network. To connect to a target whose host name is ``@code{tt}'', type:
12364 (vxgdb) target vxworks tt
12368 @value{GDBN} displays messages like these:
12371 Attaching remote machine across net...
12376 @value{GDBN} then attempts to read the symbol tables of any object modules
12377 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
12378 these files by searching the directories listed in the command search
12379 path (@pxref{Environment, ,Your program's environment}); if it fails
12380 to find an object file, it displays a message such as:
12383 prog.o: No such file or directory.
12386 When this happens, add the appropriate directory to the search path with
12387 the @value{GDBN} command @code{path}, and execute the @code{target}
12390 @node VxWorks Download
12391 @subsubsection VxWorks download
12393 @cindex download to VxWorks
12394 If you have connected to the VxWorks target and you want to debug an
12395 object that has not yet been loaded, you can use the @value{GDBN}
12396 @code{load} command to download a file from Unix to VxWorks
12397 incrementally. The object file given as an argument to the @code{load}
12398 command is actually opened twice: first by the VxWorks target in order
12399 to download the code, then by @value{GDBN} in order to read the symbol
12400 table. This can lead to problems if the current working directories on
12401 the two systems differ. If both systems have NFS mounted the same
12402 filesystems, you can avoid these problems by using absolute paths.
12403 Otherwise, it is simplest to set the working directory on both systems
12404 to the directory in which the object file resides, and then to reference
12405 the file by its name, without any path. For instance, a program
12406 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
12407 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
12408 program, type this on VxWorks:
12411 -> cd "@var{vxpath}/vw/demo/rdb"
12415 Then, in @value{GDBN}, type:
12418 (vxgdb) cd @var{hostpath}/vw/demo/rdb
12419 (vxgdb) load prog.o
12422 @value{GDBN} displays a response similar to this:
12425 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
12428 You can also use the @code{load} command to reload an object module
12429 after editing and recompiling the corresponding source file. Note that
12430 this makes @value{GDBN} delete all currently-defined breakpoints,
12431 auto-displays, and convenience variables, and to clear the value
12432 history. (This is necessary in order to preserve the integrity of
12433 debugger's data structures that reference the target system's symbol
12436 @node VxWorks Attach
12437 @subsubsection Running tasks
12439 @cindex running VxWorks tasks
12440 You can also attach to an existing task using the @code{attach} command as
12444 (vxgdb) attach @var{task}
12448 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
12449 or suspended when you attach to it. Running tasks are suspended at
12450 the time of attachment.
12452 @node Embedded Processors
12453 @section Embedded Processors
12455 This section goes into details specific to particular embedded
12461 * H8/300:: Renesas H8/300
12462 * H8/500:: Renesas H8/500
12463 * M32R/D:: Renesas M32R/D
12464 * M68K:: Motorola M68K
12465 * MIPS Embedded:: MIPS Embedded
12466 * OpenRISC 1000:: OpenRisc 1000
12467 * PA:: HP PA Embedded
12470 * Sparclet:: Tsqware Sparclet
12471 * Sparclite:: Fujitsu Sparclite
12472 * ST2000:: Tandem ST2000
12473 * Z8000:: Zilog Z8000
12482 @item target rdi @var{dev}
12483 ARM Angel monitor, via RDI library interface to ADP protocol. You may
12484 use this target to communicate with both boards running the Angel
12485 monitor, or with the EmbeddedICE JTAG debug device.
12488 @item target rdp @var{dev}
12494 @subsection Renesas H8/300
12498 @kindex target hms@r{, with H8/300}
12499 @item target hms @var{dev}
12500 A Renesas SH, H8/300, or H8/500 board, attached via serial line to your host.
12501 Use special commands @code{device} and @code{speed} to control the serial
12502 line and the communications speed used.
12504 @kindex target e7000@r{, with H8/300}
12505 @item target e7000 @var{dev}
12506 E7000 emulator for Renesas H8 and SH.
12508 @kindex target sh3@r{, with H8/300}
12509 @kindex target sh3e@r{, with H8/300}
12510 @item target sh3 @var{dev}
12511 @itemx target sh3e @var{dev}
12512 Renesas SH-3 and SH-3E target systems.
12516 @cindex download to H8/300 or H8/500
12517 @cindex H8/300 or H8/500 download
12518 @cindex download to Renesas SH
12519 @cindex Renesas SH download
12520 When you select remote debugging to a Renesas SH, H8/300, or H8/500
12521 board, the @code{load} command downloads your program to the Renesas
12522 board and also opens it as the current executable target for
12523 @value{GDBN} on your host (like the @code{file} command).
12525 @value{GDBN} needs to know these things to talk to your
12526 Renesas SH, H8/300, or H8/500:
12530 that you want to use @samp{target hms}, the remote debugging interface
12531 for Renesas microprocessors, or @samp{target e7000}, the in-circuit
12532 emulator for the Renesas SH and the Renesas 300H. (@samp{target hms} is
12533 the default when @value{GDBN} is configured specifically for the Renesas SH,
12534 H8/300, or H8/500.)
12537 what serial device connects your host to your Renesas board (the first
12538 serial device available on your host is the default).
12541 what speed to use over the serial device.
12545 * Renesas Boards:: Connecting to Renesas boards.
12546 * Renesas ICE:: Using the E7000 In-Circuit Emulator.
12547 * Renesas Special:: Special @value{GDBN} commands for Renesas micros.
12550 @node Renesas Boards
12551 @subsubsection Connecting to Renesas boards
12553 @c only for Unix hosts
12555 @cindex serial device, Renesas micros
12556 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
12557 need to explicitly set the serial device. The default @var{port} is the
12558 first available port on your host. This is only necessary on Unix
12559 hosts, where it is typically something like @file{/dev/ttya}.
12562 @cindex serial line speed, Renesas micros
12563 @code{@value{GDBN}} has another special command to set the communications
12564 speed: @samp{speed @var{bps}}. This command also is only used from Unix
12565 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
12566 the DOS @code{mode} command (for instance,
12567 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
12569 The @samp{device} and @samp{speed} commands are available only when you
12570 use a Unix host to debug your Renesas microprocessor programs. If you
12572 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
12573 called @code{asynctsr} to communicate with the development board
12574 through a PC serial port. You must also use the DOS @code{mode} command
12575 to set up the serial port on the DOS side.
12577 The following sample session illustrates the steps needed to start a
12578 program under @value{GDBN} control on an H8/300. The example uses a
12579 sample H8/300 program called @file{t.x}. The procedure is the same for
12580 the Renesas SH and the H8/500.
12582 First hook up your development board. In this example, we use a
12583 board attached to serial port @code{COM2}; if you use a different serial
12584 port, substitute its name in the argument of the @code{mode} command.
12585 When you call @code{asynctsr}, the auxiliary comms program used by the
12586 debugger, you give it just the numeric part of the serial port's name;
12587 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
12591 C:\H8300\TEST> asynctsr 2
12592 C:\H8300\TEST> mode com2:9600,n,8,1,p
12594 Resident portion of MODE loaded
12596 COM2: 9600, n, 8, 1, p
12601 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
12602 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
12603 disable it, or even boot without it, to use @code{asynctsr} to control
12604 your development board.
12607 @kindex target hms@r{, and serial protocol}
12608 Now that serial communications are set up, and the development board is
12609 connected, you can start up @value{GDBN}. Call @code{@value{GDBP}} with
12610 the name of your program as the argument. @code{@value{GDBN}} prompts
12611 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
12612 commands to begin your debugging session: @samp{target hms} to specify
12613 cross-debugging to the Renesas board, and the @code{load} command to
12614 download your program to the board. @code{load} displays the names of
12615 the program's sections, and a @samp{*} for each 2K of data downloaded.
12616 (If you want to refresh @value{GDBN} data on symbols or on the
12617 executable file without downloading, use the @value{GDBN} commands
12618 @code{file} or @code{symbol-file}. These commands, and @code{load}
12619 itself, are described in @ref{Files,,Commands to specify files}.)
12622 (eg-C:\H8300\TEST) @value{GDBP} t.x
12623 @value{GDBN} is free software and you are welcome to distribute copies
12624 of it under certain conditions; type "show copying" to see
12626 There is absolutely no warranty for @value{GDBN}; type "show warranty"
12628 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
12629 (@value{GDBP}) target hms
12630 Connected to remote H8/300 HMS system.
12631 (@value{GDBP}) load t.x
12632 .text : 0x8000 .. 0xabde ***********
12633 .data : 0xabde .. 0xad30 *
12634 .stack : 0xf000 .. 0xf014 *
12637 At this point, you're ready to run or debug your program. From here on,
12638 you can use all the usual @value{GDBN} commands. The @code{break} command
12639 sets breakpoints; the @code{run} command starts your program;
12640 @code{print} or @code{x} display data; the @code{continue} command
12641 resumes execution after stopping at a breakpoint. You can use the
12642 @code{help} command at any time to find out more about @value{GDBN} commands.
12644 Remember, however, that @emph{operating system} facilities aren't
12645 available on your development board; for example, if your program hangs,
12646 you can't send an interrupt---but you can press the @sc{reset} switch!
12648 Use the @sc{reset} button on the development board
12651 to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
12652 no way to pass an interrupt signal to the development board); and
12655 to return to the @value{GDBN} command prompt after your program finishes
12656 normally. The communications protocol provides no other way for @value{GDBN}
12657 to detect program completion.
12660 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
12661 development board as a ``normal exit'' of your program.
12664 @subsubsection Using the E7000 in-circuit emulator
12666 @kindex target e7000@r{, with Renesas ICE}
12667 You can use the E7000 in-circuit emulator to develop code for either the
12668 Renesas SH or the H8/300H. Use one of these forms of the @samp{target
12669 e7000} command to connect @value{GDBN} to your E7000:
12672 @item target e7000 @var{port} @var{speed}
12673 Use this form if your E7000 is connected to a serial port. The
12674 @var{port} argument identifies what serial port to use (for example,
12675 @samp{com2}). The third argument is the line speed in bits per second
12676 (for example, @samp{9600}).
12678 @item target e7000 @var{hostname}
12679 If your E7000 is installed as a host on a TCP/IP network, you can just
12680 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
12683 @node Renesas Special
12684 @subsubsection Special @value{GDBN} commands for Renesas micros
12686 Some @value{GDBN} commands are available only for the H8/300:
12690 @kindex set machine
12691 @kindex show machine
12692 @item set machine h8300
12693 @itemx set machine h8300h
12694 Condition @value{GDBN} for one of the two variants of the H8/300
12695 architecture with @samp{set machine}. You can use @samp{show machine}
12696 to check which variant is currently in effect.
12705 @kindex set memory @var{mod}
12706 @cindex memory models, H8/500
12707 @item set memory @var{mod}
12709 Specify which H8/500 memory model (@var{mod}) you are using with
12710 @samp{set memory}; check which memory model is in effect with @samp{show
12711 memory}. The accepted values for @var{mod} are @code{small},
12712 @code{big}, @code{medium}, and @code{compact}.
12717 @subsection Renesas M32R/D
12721 @kindex target m32r
12722 @item target m32r @var{dev}
12723 Renesas M32R/D ROM monitor.
12725 @kindex target m32rsdi
12726 @item target m32rsdi @var{dev}
12727 Renesas M32R SDI server, connected via parallel port to the board.
12734 The Motorola m68k configuration includes ColdFire support, and
12735 target command for the following ROM monitors.
12739 @kindex target abug
12740 @item target abug @var{dev}
12741 ABug ROM monitor for M68K.
12743 @kindex target cpu32bug
12744 @item target cpu32bug @var{dev}
12745 CPU32BUG monitor, running on a CPU32 (M68K) board.
12747 @kindex target dbug
12748 @item target dbug @var{dev}
12749 dBUG ROM monitor for Motorola ColdFire.
12752 @item target est @var{dev}
12753 EST-300 ICE monitor, running on a CPU32 (M68K) board.
12755 @kindex target rom68k
12756 @item target rom68k @var{dev}
12757 ROM 68K monitor, running on an M68K IDP board.
12763 @kindex target rombug
12764 @item target rombug @var{dev}
12765 ROMBUG ROM monitor for OS/9000.
12769 @node MIPS Embedded
12770 @subsection MIPS Embedded
12772 @cindex MIPS boards
12773 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
12774 MIPS board attached to a serial line. This is available when
12775 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
12778 Use these @value{GDBN} commands to specify the connection to your target board:
12781 @item target mips @var{port}
12782 @kindex target mips @var{port}
12783 To run a program on the board, start up @code{@value{GDBP}} with the
12784 name of your program as the argument. To connect to the board, use the
12785 command @samp{target mips @var{port}}, where @var{port} is the name of
12786 the serial port connected to the board. If the program has not already
12787 been downloaded to the board, you may use the @code{load} command to
12788 download it. You can then use all the usual @value{GDBN} commands.
12790 For example, this sequence connects to the target board through a serial
12791 port, and loads and runs a program called @var{prog} through the
12795 host$ @value{GDBP} @var{prog}
12796 @value{GDBN} is free software and @dots{}
12797 (@value{GDBP}) target mips /dev/ttyb
12798 (@value{GDBP}) load @var{prog}
12802 @item target mips @var{hostname}:@var{portnumber}
12803 On some @value{GDBN} host configurations, you can specify a TCP
12804 connection (for instance, to a serial line managed by a terminal
12805 concentrator) instead of a serial port, using the syntax
12806 @samp{@var{hostname}:@var{portnumber}}.
12808 @item target pmon @var{port}
12809 @kindex target pmon @var{port}
12812 @item target ddb @var{port}
12813 @kindex target ddb @var{port}
12814 NEC's DDB variant of PMON for Vr4300.
12816 @item target lsi @var{port}
12817 @kindex target lsi @var{port}
12818 LSI variant of PMON.
12820 @kindex target r3900
12821 @item target r3900 @var{dev}
12822 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
12824 @kindex target array
12825 @item target array @var{dev}
12826 Array Tech LSI33K RAID controller board.
12832 @value{GDBN} also supports these special commands for MIPS targets:
12835 @item set processor @var{args}
12836 @itemx show processor
12837 @kindex set processor @var{args}
12838 @kindex show processor
12839 Use the @code{set processor} command to set the type of MIPS
12840 processor when you want to access processor-type-specific registers.
12841 For example, @code{set processor @var{r3041}} tells @value{GDBN}
12842 to use the CPU registers appropriate for the 3041 chip.
12843 Use the @code{show processor} command to see what MIPS processor @value{GDBN}
12844 is using. Use the @code{info reg} command to see what registers
12845 @value{GDBN} is using.
12847 @item set mipsfpu double
12848 @itemx set mipsfpu single
12849 @itemx set mipsfpu none
12850 @itemx show mipsfpu
12851 @kindex set mipsfpu
12852 @kindex show mipsfpu
12853 @cindex MIPS remote floating point
12854 @cindex floating point, MIPS remote
12855 If your target board does not support the MIPS floating point
12856 coprocessor, you should use the command @samp{set mipsfpu none} (if you
12857 need this, you may wish to put the command in your @value{GDBN} init
12858 file). This tells @value{GDBN} how to find the return value of
12859 functions which return floating point values. It also allows
12860 @value{GDBN} to avoid saving the floating point registers when calling
12861 functions on the board. If you are using a floating point coprocessor
12862 with only single precision floating point support, as on the @sc{r4650}
12863 processor, use the command @samp{set mipsfpu single}. The default
12864 double precision floating point coprocessor may be selected using
12865 @samp{set mipsfpu double}.
12867 In previous versions the only choices were double precision or no
12868 floating point, so @samp{set mipsfpu on} will select double precision
12869 and @samp{set mipsfpu off} will select no floating point.
12871 As usual, you can inquire about the @code{mipsfpu} variable with
12872 @samp{show mipsfpu}.
12874 @item set remotedebug @var{n}
12875 @itemx show remotedebug
12876 @kindex set remotedebug@r{, MIPS protocol}
12877 @kindex show remotedebug@r{, MIPS protocol}
12878 @cindex @code{remotedebug}, MIPS protocol
12879 @cindex MIPS @code{remotedebug} protocol
12880 @c FIXME! For this to be useful, you must know something about the MIPS
12881 @c FIXME...protocol. Where is it described?
12882 You can see some debugging information about communications with the board
12883 by setting the @code{remotedebug} variable. If you set it to @code{1} using
12884 @samp{set remotedebug 1}, every packet is displayed. If you set it
12885 to @code{2}, every character is displayed. You can check the current value
12886 at any time with the command @samp{show remotedebug}.
12888 @item set timeout @var{seconds}
12889 @itemx set retransmit-timeout @var{seconds}
12890 @itemx show timeout
12891 @itemx show retransmit-timeout
12892 @cindex @code{timeout}, MIPS protocol
12893 @cindex @code{retransmit-timeout}, MIPS protocol
12894 @kindex set timeout
12895 @kindex show timeout
12896 @kindex set retransmit-timeout
12897 @kindex show retransmit-timeout
12898 You can control the timeout used while waiting for a packet, in the MIPS
12899 remote protocol, with the @code{set timeout @var{seconds}} command. The
12900 default is 5 seconds. Similarly, you can control the timeout used while
12901 waiting for an acknowledgement of a packet with the @code{set
12902 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
12903 You can inspect both values with @code{show timeout} and @code{show
12904 retransmit-timeout}. (These commands are @emph{only} available when
12905 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
12907 The timeout set by @code{set timeout} does not apply when @value{GDBN}
12908 is waiting for your program to stop. In that case, @value{GDBN} waits
12909 forever because it has no way of knowing how long the program is going
12910 to run before stopping.
12913 @node OpenRISC 1000
12914 @subsection OpenRISC 1000
12915 @cindex OpenRISC 1000
12917 @cindex or1k boards
12918 See OR1k Architecture document (@uref{www.opencores.org}) for more information
12919 about platform and commands.
12923 @kindex target jtag
12924 @item target jtag jtag://@var{host}:@var{port}
12926 Connects to remote JTAG server.
12927 JTAG remote server can be either an or1ksim or JTAG server,
12928 connected via parallel port to the board.
12930 Example: @code{target jtag jtag://localhost:9999}
12933 @item or1ksim @var{command}
12934 If connected to @code{or1ksim} OpenRISC 1000 Architectural
12935 Simulator, proprietary commands can be executed.
12937 @kindex info or1k spr
12938 @item info or1k spr
12939 Displays spr groups.
12941 @item info or1k spr @var{group}
12942 @itemx info or1k spr @var{groupno}
12943 Displays register names in selected group.
12945 @item info or1k spr @var{group} @var{register}
12946 @itemx info or1k spr @var{register}
12947 @itemx info or1k spr @var{groupno} @var{registerno}
12948 @itemx info or1k spr @var{registerno}
12949 Shows information about specified spr register.
12952 @item spr @var{group} @var{register} @var{value}
12953 @itemx spr @var{register @var{value}}
12954 @itemx spr @var{groupno} @var{registerno @var{value}}
12955 @itemx spr @var{registerno @var{value}}
12956 Writes @var{value} to specified spr register.
12959 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
12960 It is very similar to @value{GDBN} trace, except it does not interfere with normal
12961 program execution and is thus much faster. Hardware breakpoints/watchpoint
12962 triggers can be set using:
12965 Load effective address/data
12967 Store effective address/data
12969 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
12974 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
12975 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
12977 @code{htrace} commands:
12978 @cindex OpenRISC 1000 htrace
12981 @item hwatch @var{conditional}
12982 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
12983 or Data. For example:
12985 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
12987 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
12991 Display information about current HW trace configuration.
12993 @item htrace trigger @var{conditional}
12994 Set starting criteria for HW trace.
12996 @item htrace qualifier @var{conditional}
12997 Set acquisition qualifier for HW trace.
12999 @item htrace stop @var{conditional}
13000 Set HW trace stopping criteria.
13002 @item htrace record [@var{data}]*
13003 Selects the data to be recorded, when qualifier is met and HW trace was
13006 @item htrace enable
13007 @itemx htrace disable
13008 Enables/disables the HW trace.
13010 @item htrace rewind [@var{filename}]
13011 Clears currently recorded trace data.
13013 If filename is specified, new trace file is made and any newly collected data
13014 will be written there.
13016 @item htrace print [@var{start} [@var{len}]]
13017 Prints trace buffer, using current record configuration.
13019 @item htrace mode continuous
13020 Set continuous trace mode.
13022 @item htrace mode suspend
13023 Set suspend trace mode.
13028 @subsection PowerPC
13032 @kindex target dink32
13033 @item target dink32 @var{dev}
13034 DINK32 ROM monitor.
13036 @kindex target ppcbug
13037 @item target ppcbug @var{dev}
13038 @kindex target ppcbug1
13039 @item target ppcbug1 @var{dev}
13040 PPCBUG ROM monitor for PowerPC.
13043 @item target sds @var{dev}
13044 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
13049 @subsection HP PA Embedded
13053 @kindex target op50n
13054 @item target op50n @var{dev}
13055 OP50N monitor, running on an OKI HPPA board.
13057 @kindex target w89k
13058 @item target w89k @var{dev}
13059 W89K monitor, running on a Winbond HPPA board.
13064 @subsection Renesas SH
13068 @kindex target hms@r{, with Renesas SH}
13069 @item target hms @var{dev}
13070 A Renesas SH board attached via serial line to your host. Use special
13071 commands @code{device} and @code{speed} to control the serial line and
13072 the communications speed used.
13074 @kindex target e7000@r{, with Renesas SH}
13075 @item target e7000 @var{dev}
13076 E7000 emulator for Renesas SH.
13078 @kindex target sh3@r{, with SH}
13079 @kindex target sh3e@r{, with SH}
13080 @item target sh3 @var{dev}
13081 @item target sh3e @var{dev}
13082 Renesas SH-3 and SH-3E target systems.
13087 @subsection Tsqware Sparclet
13091 @value{GDBN} enables developers to debug tasks running on
13092 Sparclet targets from a Unix host.
13093 @value{GDBN} uses code that runs on
13094 both the Unix host and on the Sparclet target. The program
13095 @code{@value{GDBP}} is installed and executed on the Unix host.
13098 @item remotetimeout @var{args}
13099 @kindex remotetimeout
13100 @value{GDBN} supports the option @code{remotetimeout}.
13101 This option is set by the user, and @var{args} represents the number of
13102 seconds @value{GDBN} waits for responses.
13105 @cindex compiling, on Sparclet
13106 When compiling for debugging, include the options @samp{-g} to get debug
13107 information and @samp{-Ttext} to relocate the program to where you wish to
13108 load it on the target. You may also want to add the options @samp{-n} or
13109 @samp{-N} in order to reduce the size of the sections. Example:
13112 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
13115 You can use @code{objdump} to verify that the addresses are what you intended:
13118 sparclet-aout-objdump --headers --syms prog
13121 @cindex running, on Sparclet
13123 your Unix execution search path to find @value{GDBN}, you are ready to
13124 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
13125 (or @code{sparclet-aout-gdb}, depending on your installation).
13127 @value{GDBN} comes up showing the prompt:
13134 * Sparclet File:: Setting the file to debug
13135 * Sparclet Connection:: Connecting to Sparclet
13136 * Sparclet Download:: Sparclet download
13137 * Sparclet Execution:: Running and debugging
13140 @node Sparclet File
13141 @subsubsection Setting file to debug
13143 The @value{GDBN} command @code{file} lets you choose with program to debug.
13146 (gdbslet) file prog
13150 @value{GDBN} then attempts to read the symbol table of @file{prog}.
13151 @value{GDBN} locates
13152 the file by searching the directories listed in the command search
13154 If the file was compiled with debug information (option "-g"), source
13155 files will be searched as well.
13156 @value{GDBN} locates
13157 the source files by searching the directories listed in the directory search
13158 path (@pxref{Environment, ,Your program's environment}).
13160 to find a file, it displays a message such as:
13163 prog: No such file or directory.
13166 When this happens, add the appropriate directories to the search paths with
13167 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
13168 @code{target} command again.
13170 @node Sparclet Connection
13171 @subsubsection Connecting to Sparclet
13173 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
13174 To connect to a target on serial port ``@code{ttya}'', type:
13177 (gdbslet) target sparclet /dev/ttya
13178 Remote target sparclet connected to /dev/ttya
13179 main () at ../prog.c:3
13183 @value{GDBN} displays messages like these:
13189 @node Sparclet Download
13190 @subsubsection Sparclet download
13192 @cindex download to Sparclet
13193 Once connected to the Sparclet target,
13194 you can use the @value{GDBN}
13195 @code{load} command to download the file from the host to the target.
13196 The file name and load offset should be given as arguments to the @code{load}
13198 Since the file format is aout, the program must be loaded to the starting
13199 address. You can use @code{objdump} to find out what this value is. The load
13200 offset is an offset which is added to the VMA (virtual memory address)
13201 of each of the file's sections.
13202 For instance, if the program
13203 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
13204 and bss at 0x12010170, in @value{GDBN}, type:
13207 (gdbslet) load prog 0x12010000
13208 Loading section .text, size 0xdb0 vma 0x12010000
13211 If the code is loaded at a different address then what the program was linked
13212 to, you may need to use the @code{section} and @code{add-symbol-file} commands
13213 to tell @value{GDBN} where to map the symbol table.
13215 @node Sparclet Execution
13216 @subsubsection Running and debugging
13218 @cindex running and debugging Sparclet programs
13219 You can now begin debugging the task using @value{GDBN}'s execution control
13220 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
13221 manual for the list of commands.
13225 Breakpoint 1 at 0x12010000: file prog.c, line 3.
13227 Starting program: prog
13228 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
13229 3 char *symarg = 0;
13231 4 char *execarg = "hello!";
13236 @subsection Fujitsu Sparclite
13240 @kindex target sparclite
13241 @item target sparclite @var{dev}
13242 Fujitsu sparclite boards, used only for the purpose of loading.
13243 You must use an additional command to debug the program.
13244 For example: target remote @var{dev} using @value{GDBN} standard
13250 @subsection Tandem ST2000
13252 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
13255 To connect your ST2000 to the host system, see the manufacturer's
13256 manual. Once the ST2000 is physically attached, you can run:
13259 target st2000 @var{dev} @var{speed}
13263 to establish it as your debugging environment. @var{dev} is normally
13264 the name of a serial device, such as @file{/dev/ttya}, connected to the
13265 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
13266 connection (for example, to a serial line attached via a terminal
13267 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
13269 The @code{load} and @code{attach} commands are @emph{not} defined for
13270 this target; you must load your program into the ST2000 as you normally
13271 would for standalone operation. @value{GDBN} reads debugging information
13272 (such as symbols) from a separate, debugging version of the program
13273 available on your host computer.
13274 @c FIXME!! This is terribly vague; what little content is here is
13275 @c basically hearsay.
13277 @cindex ST2000 auxiliary commands
13278 These auxiliary @value{GDBN} commands are available to help you with the ST2000
13282 @item st2000 @var{command}
13283 @kindex st2000 @var{cmd}
13284 @cindex STDBUG commands (ST2000)
13285 @cindex commands to STDBUG (ST2000)
13286 Send a @var{command} to the STDBUG monitor. See the manufacturer's
13287 manual for available commands.
13290 @cindex connect (to STDBUG)
13291 Connect the controlling terminal to the STDBUG command monitor. When
13292 you are done interacting with STDBUG, typing either of two character
13293 sequences gets you back to the @value{GDBN} command prompt:
13294 @kbd{@key{RET}~.} (Return, followed by tilde and period) or
13295 @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
13299 @subsection Zilog Z8000
13302 @cindex simulator, Z8000
13303 @cindex Zilog Z8000 simulator
13305 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
13308 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
13309 unsegmented variant of the Z8000 architecture) or the Z8001 (the
13310 segmented variant). The simulator recognizes which architecture is
13311 appropriate by inspecting the object code.
13314 @item target sim @var{args}
13316 @kindex target sim@r{, with Z8000}
13317 Debug programs on a simulated CPU. If the simulator supports setup
13318 options, specify them via @var{args}.
13322 After specifying this target, you can debug programs for the simulated
13323 CPU in the same style as programs for your host computer; use the
13324 @code{file} command to load a new program image, the @code{run} command
13325 to run your program, and so on.
13327 As well as making available all the usual machine registers
13328 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
13329 additional items of information as specially named registers:
13334 Counts clock-ticks in the simulator.
13337 Counts instructions run in the simulator.
13340 Execution time in 60ths of a second.
13344 You can refer to these values in @value{GDBN} expressions with the usual
13345 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
13346 conditional breakpoint that suspends only after at least 5000
13347 simulated clock ticks.
13349 @node Architectures
13350 @section Architectures
13352 This section describes characteristics of architectures that affect
13353 all uses of @value{GDBN} with the architecture, both native and cross.
13366 @kindex set rstack_high_address
13367 @cindex AMD 29K register stack
13368 @cindex register stack, AMD29K
13369 @item set rstack_high_address @var{address}
13370 On AMD 29000 family processors, registers are saved in a separate
13371 @dfn{register stack}. There is no way for @value{GDBN} to determine the
13372 extent of this stack. Normally, @value{GDBN} just assumes that the
13373 stack is ``large enough''. This may result in @value{GDBN} referencing
13374 memory locations that do not exist. If necessary, you can get around
13375 this problem by specifying the ending address of the register stack with
13376 the @code{set rstack_high_address} command. The argument should be an
13377 address, which you probably want to precede with @samp{0x} to specify in
13380 @kindex show rstack_high_address
13381 @item show rstack_high_address
13382 Display the current limit of the register stack, on AMD 29000 family
13390 See the following section.
13395 @cindex stack on Alpha
13396 @cindex stack on MIPS
13397 @cindex Alpha stack
13399 Alpha- and MIPS-based computers use an unusual stack frame, which
13400 sometimes requires @value{GDBN} to search backward in the object code to
13401 find the beginning of a function.
13403 @cindex response time, MIPS debugging
13404 To improve response time (especially for embedded applications, where
13405 @value{GDBN} may be restricted to a slow serial line for this search)
13406 you may want to limit the size of this search, using one of these
13410 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
13411 @item set heuristic-fence-post @var{limit}
13412 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
13413 search for the beginning of a function. A value of @var{0} (the
13414 default) means there is no limit. However, except for @var{0}, the
13415 larger the limit the more bytes @code{heuristic-fence-post} must search
13416 and therefore the longer it takes to run.
13418 @item show heuristic-fence-post
13419 Display the current limit.
13423 These commands are available @emph{only} when @value{GDBN} is configured
13424 for debugging programs on Alpha or MIPS processors.
13427 @node Controlling GDB
13428 @chapter Controlling @value{GDBN}
13430 You can alter the way @value{GDBN} interacts with you by using the
13431 @code{set} command. For commands controlling how @value{GDBN} displays
13432 data, see @ref{Print Settings, ,Print settings}. Other settings are
13437 * Editing:: Command editing
13438 * History:: Command history
13439 * Screen Size:: Screen size
13440 * Numbers:: Numbers
13441 * ABI:: Configuring the current ABI
13442 * Messages/Warnings:: Optional warnings and messages
13443 * Debugging Output:: Optional messages about internal happenings
13451 @value{GDBN} indicates its readiness to read a command by printing a string
13452 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
13453 can change the prompt string with the @code{set prompt} command. For
13454 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
13455 the prompt in one of the @value{GDBN} sessions so that you can always tell
13456 which one you are talking to.
13458 @emph{Note:} @code{set prompt} does not add a space for you after the
13459 prompt you set. This allows you to set a prompt which ends in a space
13460 or a prompt that does not.
13464 @item set prompt @var{newprompt}
13465 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
13467 @kindex show prompt
13469 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
13473 @section Command editing
13475 @cindex command line editing
13477 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
13478 @sc{gnu} library provides consistent behavior for programs which provide a
13479 command line interface to the user. Advantages are @sc{gnu} Emacs-style
13480 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
13481 substitution, and a storage and recall of command history across
13482 debugging sessions.
13484 You may control the behavior of command line editing in @value{GDBN} with the
13485 command @code{set}.
13488 @kindex set editing
13491 @itemx set editing on
13492 Enable command line editing (enabled by default).
13494 @item set editing off
13495 Disable command line editing.
13497 @kindex show editing
13499 Show whether command line editing is enabled.
13502 @xref{Command Line Editing}, for more details about the Readline
13503 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
13504 encouraged to read that chapter.
13507 @section Command history
13508 @cindex command history
13510 @value{GDBN} can keep track of the commands you type during your
13511 debugging sessions, so that you can be certain of precisely what
13512 happened. Use these commands to manage the @value{GDBN} command
13515 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
13516 package, to provide the history facility. @xref{Using History
13517 Interactively}, for the detailed description of the History library.
13519 Here is the description of @value{GDBN} commands related to command
13523 @cindex history substitution
13524 @cindex history file
13525 @kindex set history filename
13526 @cindex @env{GDBHISTFILE}, environment variable
13527 @item set history filename @var{fname}
13528 Set the name of the @value{GDBN} command history file to @var{fname}.
13529 This is the file where @value{GDBN} reads an initial command history
13530 list, and where it writes the command history from this session when it
13531 exits. You can access this list through history expansion or through
13532 the history command editing characters listed below. This file defaults
13533 to the value of the environment variable @code{GDBHISTFILE}, or to
13534 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
13537 @cindex history save
13538 @kindex set history
13539 @item set history save
13540 @itemx set history save on
13541 Record command history in a file, whose name may be specified with the
13542 @code{set history filename} command. By default, this option is disabled.
13544 @item set history save off
13545 Stop recording command history in a file.
13547 @cindex history size
13548 @item set history size @var{size}
13549 Set the number of commands which @value{GDBN} keeps in its history list.
13550 This defaults to the value of the environment variable
13551 @code{HISTSIZE}, or to 256 if this variable is not set.
13554 History expansion assigns special meaning to the character @kbd{!}.
13555 @xref{Event Designators}, for more details.
13557 @cindex history expansion, turn on/off
13558 Since @kbd{!} is also the logical not operator in C, history expansion
13559 is off by default. If you decide to enable history expansion with the
13560 @code{set history expansion on} command, you may sometimes need to
13561 follow @kbd{!} (when it is used as logical not, in an expression) with
13562 a space or a tab to prevent it from being expanded. The readline
13563 history facilities do not attempt substitution on the strings
13564 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
13566 The commands to control history expansion are:
13569 @item set history expansion on
13570 @itemx set history expansion
13571 @kindex set history expansion
13572 Enable history expansion. History expansion is off by default.
13574 @item set history expansion off
13575 Disable history expansion.
13578 @kindex show history
13580 @itemx show history filename
13581 @itemx show history save
13582 @itemx show history size
13583 @itemx show history expansion
13584 These commands display the state of the @value{GDBN} history parameters.
13585 @code{show history} by itself displays all four states.
13591 @item show commands
13592 Display the last ten commands in the command history.
13594 @item show commands @var{n}
13595 Print ten commands centered on command number @var{n}.
13597 @item show commands +
13598 Print ten commands just after the commands last printed.
13602 @section Screen size
13603 @cindex size of screen
13604 @cindex pauses in output
13606 Certain commands to @value{GDBN} may produce large amounts of
13607 information output to the screen. To help you read all of it,
13608 @value{GDBN} pauses and asks you for input at the end of each page of
13609 output. Type @key{RET} when you want to continue the output, or @kbd{q}
13610 to discard the remaining output. Also, the screen width setting
13611 determines when to wrap lines of output. Depending on what is being
13612 printed, @value{GDBN} tries to break the line at a readable place,
13613 rather than simply letting it overflow onto the following line.
13615 Normally @value{GDBN} knows the size of the screen from the terminal
13616 driver software. For example, on Unix @value{GDBN} uses the termcap data base
13617 together with the value of the @code{TERM} environment variable and the
13618 @code{stty rows} and @code{stty cols} settings. If this is not correct,
13619 you can override it with the @code{set height} and @code{set
13626 @kindex show height
13627 @item set height @var{lpp}
13629 @itemx set width @var{cpl}
13631 These @code{set} commands specify a screen height of @var{lpp} lines and
13632 a screen width of @var{cpl} characters. The associated @code{show}
13633 commands display the current settings.
13635 If you specify a height of zero lines, @value{GDBN} does not pause during
13636 output no matter how long the output is. This is useful if output is to a
13637 file or to an editor buffer.
13639 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
13640 from wrapping its output.
13645 @cindex number representation
13646 @cindex entering numbers
13648 You can always enter numbers in octal, decimal, or hexadecimal in
13649 @value{GDBN} by the usual conventions: octal numbers begin with
13650 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
13651 begin with @samp{0x}. Numbers that begin with none of these are, by
13652 default, entered in base 10; likewise, the default display for
13653 numbers---when no particular format is specified---is base 10. You can
13654 change the default base for both input and output with the @code{set
13658 @kindex set input-radix
13659 @item set input-radix @var{base}
13660 Set the default base for numeric input. Supported choices
13661 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
13662 specified either unambiguously or using the current default radix; for
13672 sets the base to decimal. On the other hand, @samp{set radix 10}
13673 leaves the radix unchanged no matter what it was.
13675 @kindex set output-radix
13676 @item set output-radix @var{base}
13677 Set the default base for numeric display. Supported choices
13678 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
13679 specified either unambiguously or using the current default radix.
13681 @kindex show input-radix
13682 @item show input-radix
13683 Display the current default base for numeric input.
13685 @kindex show output-radix
13686 @item show output-radix
13687 Display the current default base for numeric display.
13691 @section Configuring the current ABI
13693 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
13694 application automatically. However, sometimes you need to override its
13695 conclusions. Use these commands to manage @value{GDBN}'s view of the
13702 One @value{GDBN} configuration can debug binaries for multiple operating
13703 system targets, either via remote debugging or native emulation.
13704 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
13705 but you can override its conclusion using the @code{set osabi} command.
13706 One example where this is useful is in debugging of binaries which use
13707 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
13708 not have the same identifying marks that the standard C library for your
13713 Show the OS ABI currently in use.
13716 With no argument, show the list of registered available OS ABI's.
13718 @item set osabi @var{abi}
13719 Set the current OS ABI to @var{abi}.
13722 @cindex float promotion
13723 @kindex set coerce-float-to-double
13725 Generally, the way that an argument of type @code{float} is passed to a
13726 function depends on whether the function is prototyped. For a prototyped
13727 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
13728 according to the architecture's convention for @code{float}. For unprototyped
13729 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
13730 @code{double} and then passed.
13732 Unfortunately, some forms of debug information do not reliably indicate whether
13733 a function is prototyped. If @value{GDBN} calls a function that is not marked
13734 as prototyped, it consults @kbd{set coerce-float-to-double}.
13737 @item set coerce-float-to-double
13738 @itemx set coerce-float-to-double on
13739 Arguments of type @code{float} will be promoted to @code{double} when passed
13740 to an unprototyped function. This is the default setting.
13742 @item set coerce-float-to-double off
13743 Arguments of type @code{float} will be passed directly to unprototyped
13748 @kindex show cp-abi
13749 @value{GDBN} needs to know the ABI used for your program's C@t{++}
13750 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
13751 used to build your application. @value{GDBN} only fully supports
13752 programs with a single C@t{++} ABI; if your program contains code using
13753 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
13754 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
13755 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
13756 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
13757 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
13758 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
13763 Show the C@t{++} ABI currently in use.
13766 With no argument, show the list of supported C@t{++} ABI's.
13768 @item set cp-abi @var{abi}
13769 @itemx set cp-abi auto
13770 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
13773 @node Messages/Warnings
13774 @section Optional warnings and messages
13776 By default, @value{GDBN} is silent about its inner workings. If you are
13777 running on a slow machine, you may want to use the @code{set verbose}
13778 command. This makes @value{GDBN} tell you when it does a lengthy
13779 internal operation, so you will not think it has crashed.
13781 Currently, the messages controlled by @code{set verbose} are those
13782 which announce that the symbol table for a source file is being read;
13783 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
13786 @kindex set verbose
13787 @item set verbose on
13788 Enables @value{GDBN} output of certain informational messages.
13790 @item set verbose off
13791 Disables @value{GDBN} output of certain informational messages.
13793 @kindex show verbose
13795 Displays whether @code{set verbose} is on or off.
13798 By default, if @value{GDBN} encounters bugs in the symbol table of an
13799 object file, it is silent; but if you are debugging a compiler, you may
13800 find this information useful (@pxref{Symbol Errors, ,Errors reading
13805 @kindex set complaints
13806 @item set complaints @var{limit}
13807 Permits @value{GDBN} to output @var{limit} complaints about each type of
13808 unusual symbols before becoming silent about the problem. Set
13809 @var{limit} to zero to suppress all complaints; set it to a large number
13810 to prevent complaints from being suppressed.
13812 @kindex show complaints
13813 @item show complaints
13814 Displays how many symbol complaints @value{GDBN} is permitted to produce.
13818 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
13819 lot of stupid questions to confirm certain commands. For example, if
13820 you try to run a program which is already running:
13824 The program being debugged has been started already.
13825 Start it from the beginning? (y or n)
13828 If you are willing to unflinchingly face the consequences of your own
13829 commands, you can disable this ``feature'':
13833 @kindex set confirm
13835 @cindex confirmation
13836 @cindex stupid questions
13837 @item set confirm off
13838 Disables confirmation requests.
13840 @item set confirm on
13841 Enables confirmation requests (the default).
13843 @kindex show confirm
13845 Displays state of confirmation requests.
13849 @node Debugging Output
13850 @section Optional messages about internal happenings
13851 @cindex optional debugging messages
13855 @cindex gdbarch debugging info
13856 @item set debug arch
13857 Turns on or off display of gdbarch debugging info. The default is off
13859 @item show debug arch
13860 Displays the current state of displaying gdbarch debugging info.
13861 @item set debug event
13862 @cindex event debugging info
13863 Turns on or off display of @value{GDBN} event debugging info. The
13865 @item show debug event
13866 Displays the current state of displaying @value{GDBN} event debugging
13868 @item set debug expression
13869 @cindex expression debugging info
13870 Turns on or off display of @value{GDBN} expression debugging info. The
13872 @item show debug expression
13873 Displays the current state of displaying @value{GDBN} expression
13875 @item set debug frame
13876 @cindex frame debugging info
13877 Turns on or off display of @value{GDBN} frame debugging info. The
13879 @item show debug frame
13880 Displays the current state of displaying @value{GDBN} frame debugging
13882 @item set debug infrun
13883 @cindex inferior debugging info
13884 Turns on or off display of @value{GDBN} debugging info for running the inferior.
13885 The default is off. @file{infrun.c} contains GDB's runtime state machine used
13886 for implementing operations such as single-stepping the inferior.
13887 @item show debug infrun
13888 Displays the current state of @value{GDBN} inferior debugging.
13889 @item set debug observer
13890 @cindex observer debugging info
13891 Turns on or off display of @value{GDBN} observer debugging. This
13892 includes info such as the notification of observable events.
13893 @item show debug observer
13894 Displays the current state of observer debugging.
13895 @item set debug overload
13896 @cindex C@t{++} overload debugging info
13897 Turns on or off display of @value{GDBN} C@t{++} overload debugging
13898 info. This includes info such as ranking of functions, etc. The default
13900 @item show debug overload
13901 Displays the current state of displaying @value{GDBN} C@t{++} overload
13903 @cindex packets, reporting on stdout
13904 @cindex serial connections, debugging
13905 @item set debug remote
13906 Turns on or off display of reports on all packets sent back and forth across
13907 the serial line to the remote machine. The info is printed on the
13908 @value{GDBN} standard output stream. The default is off.
13909 @item show debug remote
13910 Displays the state of display of remote packets.
13911 @item set debug serial
13912 Turns on or off display of @value{GDBN} serial debugging info. The
13914 @item show debug serial
13915 Displays the current state of displaying @value{GDBN} serial debugging
13917 @item set debug target
13918 @cindex target debugging info
13919 Turns on or off display of @value{GDBN} target debugging info. This info
13920 includes what is going on at the target level of GDB, as it happens. The
13921 default is 0. Set it to 1 to track events, and to 2 to also track the
13922 value of large memory transfers. Changes to this flag do not take effect
13923 until the next time you connect to a target or use the @code{run} command.
13924 @item show debug target
13925 Displays the current state of displaying @value{GDBN} target debugging
13927 @item set debug varobj
13928 @cindex variable object debugging info
13929 Turns on or off display of @value{GDBN} variable object debugging
13930 info. The default is off.
13931 @item show debug varobj
13932 Displays the current state of displaying @value{GDBN} variable object
13937 @chapter Canned Sequences of Commands
13939 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
13940 command lists}), @value{GDBN} provides two ways to store sequences of
13941 commands for execution as a unit: user-defined commands and command
13945 * Define:: User-defined commands
13946 * Hooks:: User-defined command hooks
13947 * Command Files:: Command files
13948 * Output:: Commands for controlled output
13952 @section User-defined commands
13954 @cindex user-defined command
13955 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
13956 which you assign a new name as a command. This is done with the
13957 @code{define} command. User commands may accept up to 10 arguments
13958 separated by whitespace. Arguments are accessed within the user command
13959 via @var{$arg0@dots{}$arg9}. A trivial example:
13963 print $arg0 + $arg1 + $arg2
13967 To execute the command use:
13974 This defines the command @code{adder}, which prints the sum of
13975 its three arguments. Note the arguments are text substitutions, so they may
13976 reference variables, use complex expressions, or even perform inferior
13982 @item define @var{commandname}
13983 Define a command named @var{commandname}. If there is already a command
13984 by that name, you are asked to confirm that you want to redefine it.
13986 The definition of the command is made up of other @value{GDBN} command lines,
13987 which are given following the @code{define} command. The end of these
13988 commands is marked by a line containing @code{end}.
13993 Takes a single argument, which is an expression to evaluate.
13994 It is followed by a series of commands that are executed
13995 only if the expression is true (nonzero).
13996 There can then optionally be a line @code{else}, followed
13997 by a series of commands that are only executed if the expression
13998 was false. The end of the list is marked by a line containing @code{end}.
14002 The syntax is similar to @code{if}: the command takes a single argument,
14003 which is an expression to evaluate, and must be followed by the commands to
14004 execute, one per line, terminated by an @code{end}.
14005 The commands are executed repeatedly as long as the expression
14009 @item document @var{commandname}
14010 Document the user-defined command @var{commandname}, so that it can be
14011 accessed by @code{help}. The command @var{commandname} must already be
14012 defined. This command reads lines of documentation just as @code{define}
14013 reads the lines of the command definition, ending with @code{end}.
14014 After the @code{document} command is finished, @code{help} on command
14015 @var{commandname} displays the documentation you have written.
14017 You may use the @code{document} command again to change the
14018 documentation of a command. Redefining the command with @code{define}
14019 does not change the documentation.
14021 @kindex help user-defined
14022 @item help user-defined
14023 List all user-defined commands, with the first line of the documentation
14028 @itemx show user @var{commandname}
14029 Display the @value{GDBN} commands used to define @var{commandname} (but
14030 not its documentation). If no @var{commandname} is given, display the
14031 definitions for all user-defined commands.
14033 @kindex show max-user-call-depth
14034 @kindex set max-user-call-depth
14035 @item show max-user-call-depth
14036 @itemx set max-user-call-depth
14037 The value of @code{max-user-call-depth} controls how many recursion
14038 levels are allowed in user-defined commands before GDB suspects an
14039 infinite recursion and aborts the command.
14043 When user-defined commands are executed, the
14044 commands of the definition are not printed. An error in any command
14045 stops execution of the user-defined command.
14047 If used interactively, commands that would ask for confirmation proceed
14048 without asking when used inside a user-defined command. Many @value{GDBN}
14049 commands that normally print messages to say what they are doing omit the
14050 messages when used in a user-defined command.
14053 @section User-defined command hooks
14054 @cindex command hooks
14055 @cindex hooks, for commands
14056 @cindex hooks, pre-command
14059 You may define @dfn{hooks}, which are a special kind of user-defined
14060 command. Whenever you run the command @samp{foo}, if the user-defined
14061 command @samp{hook-foo} exists, it is executed (with no arguments)
14062 before that command.
14064 @cindex hooks, post-command
14066 A hook may also be defined which is run after the command you executed.
14067 Whenever you run the command @samp{foo}, if the user-defined command
14068 @samp{hookpost-foo} exists, it is executed (with no arguments) after
14069 that command. Post-execution hooks may exist simultaneously with
14070 pre-execution hooks, for the same command.
14072 It is valid for a hook to call the command which it hooks. If this
14073 occurs, the hook is not re-executed, thereby avoiding infinte recursion.
14075 @c It would be nice if hookpost could be passed a parameter indicating
14076 @c if the command it hooks executed properly or not. FIXME!
14078 @kindex stop@r{, a pseudo-command}
14079 In addition, a pseudo-command, @samp{stop} exists. Defining
14080 (@samp{hook-stop}) makes the associated commands execute every time
14081 execution stops in your program: before breakpoint commands are run,
14082 displays are printed, or the stack frame is printed.
14084 For example, to ignore @code{SIGALRM} signals while
14085 single-stepping, but treat them normally during normal execution,
14090 handle SIGALRM nopass
14094 handle SIGALRM pass
14097 define hook-continue
14098 handle SIGLARM pass
14102 As a further example, to hook at the begining and end of the @code{echo}
14103 command, and to add extra text to the beginning and end of the message,
14111 define hookpost-echo
14115 (@value{GDBP}) echo Hello World
14116 <<<---Hello World--->>>
14121 You can define a hook for any single-word command in @value{GDBN}, but
14122 not for command aliases; you should define a hook for the basic command
14123 name, e.g. @code{backtrace} rather than @code{bt}.
14124 @c FIXME! So how does Joe User discover whether a command is an alias
14126 If an error occurs during the execution of your hook, execution of
14127 @value{GDBN} commands stops and @value{GDBN} issues a prompt
14128 (before the command that you actually typed had a chance to run).
14130 If you try to define a hook which does not match any known command, you
14131 get a warning from the @code{define} command.
14133 @node Command Files
14134 @section Command files
14136 @cindex command files
14137 A command file for @value{GDBN} is a file of lines that are @value{GDBN}
14138 commands. Comments (lines starting with @kbd{#}) may also be included.
14139 An empty line in a command file does nothing; it does not mean to repeat
14140 the last command, as it would from the terminal.
14143 @cindex @file{.gdbinit}
14144 @cindex @file{gdb.ini}
14145 When you start @value{GDBN}, it automatically executes commands from its
14146 @dfn{init files}, normally called @file{.gdbinit}@footnote{The DJGPP
14147 port of @value{GDBN} uses the name @file{gdb.ini} instead, due to the
14148 limitations of file names imposed by DOS filesystems.}.
14149 During startup, @value{GDBN} does the following:
14153 Reads the init file (if any) in your home directory@footnote{On
14154 DOS/Windows systems, the home directory is the one pointed to by the
14155 @code{HOME} environment variable.}.
14158 Processes command line options and operands.
14161 Reads the init file (if any) in the current working directory.
14164 Reads command files specified by the @samp{-x} option.
14167 The init file in your home directory can set options (such as @samp{set
14168 complaints}) that affect subsequent processing of command line options
14169 and operands. Init files are not executed if you use the @samp{-nx}
14170 option (@pxref{Mode Options, ,Choosing modes}).
14172 @cindex init file name
14173 On some configurations of @value{GDBN}, the init file is known by a
14174 different name (these are typically environments where a specialized
14175 form of @value{GDBN} may need to coexist with other forms, hence a
14176 different name for the specialized version's init file). These are the
14177 environments with special init file names:
14179 @cindex @file{.vxgdbinit}
14182 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
14184 @cindex @file{.os68gdbinit}
14186 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
14188 @cindex @file{.esgdbinit}
14190 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
14193 You can also request the execution of a command file with the
14194 @code{source} command:
14198 @item source @var{filename}
14199 Execute the command file @var{filename}.
14202 The lines in a command file are executed sequentially. They are not
14203 printed as they are executed. An error in any command terminates
14204 execution of the command file and control is returned to the console.
14206 Commands that would ask for confirmation if used interactively proceed
14207 without asking when used in a command file. Many @value{GDBN} commands that
14208 normally print messages to say what they are doing omit the messages
14209 when called from command files.
14211 @value{GDBN} also accepts command input from standard input. In this
14212 mode, normal output goes to standard output and error output goes to
14213 standard error. Errors in a command file supplied on standard input do
14214 not terminate execution of the command file --- execution continues with
14218 gdb < cmds > log 2>&1
14221 (The syntax above will vary depending on the shell used.) This example
14222 will execute commands from the file @file{cmds}. All output and errors
14223 would be directed to @file{log}.
14226 @section Commands for controlled output
14228 During the execution of a command file or a user-defined command, normal
14229 @value{GDBN} output is suppressed; the only output that appears is what is
14230 explicitly printed by the commands in the definition. This section
14231 describes three commands useful for generating exactly the output you
14236 @item echo @var{text}
14237 @c I do not consider backslash-space a standard C escape sequence
14238 @c because it is not in ANSI.
14239 Print @var{text}. Nonprinting characters can be included in
14240 @var{text} using C escape sequences, such as @samp{\n} to print a
14241 newline. @strong{No newline is printed unless you specify one.}
14242 In addition to the standard C escape sequences, a backslash followed
14243 by a space stands for a space. This is useful for displaying a
14244 string with spaces at the beginning or the end, since leading and
14245 trailing spaces are otherwise trimmed from all arguments.
14246 To print @samp{@w{ }and foo =@w{ }}, use the command
14247 @samp{echo \@w{ }and foo = \@w{ }}.
14249 A backslash at the end of @var{text} can be used, as in C, to continue
14250 the command onto subsequent lines. For example,
14253 echo This is some text\n\
14254 which is continued\n\
14255 onto several lines.\n
14258 produces the same output as
14261 echo This is some text\n
14262 echo which is continued\n
14263 echo onto several lines.\n
14267 @item output @var{expression}
14268 Print the value of @var{expression} and nothing but that value: no
14269 newlines, no @samp{$@var{nn} = }. The value is not entered in the
14270 value history either. @xref{Expressions, ,Expressions}, for more information
14273 @item output/@var{fmt} @var{expression}
14274 Print the value of @var{expression} in format @var{fmt}. You can use
14275 the same formats as for @code{print}. @xref{Output Formats,,Output
14276 formats}, for more information.
14279 @item printf @var{string}, @var{expressions}@dots{}
14280 Print the values of the @var{expressions} under the control of
14281 @var{string}. The @var{expressions} are separated by commas and may be
14282 either numbers or pointers. Their values are printed as specified by
14283 @var{string}, exactly as if your program were to execute the C
14285 @c FIXME: the above implies that at least all ANSI C formats are
14286 @c supported, but it isn't true: %E and %G don't work (or so it seems).
14287 @c Either this is a bug, or the manual should document what formats are
14291 printf (@var{string}, @var{expressions}@dots{});
14294 For example, you can print two values in hex like this:
14297 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
14300 The only backslash-escape sequences that you can use in the format
14301 string are the simple ones that consist of backslash followed by a
14306 @chapter Command Interpreters
14307 @cindex command interpreters
14309 @value{GDBN} supports multiple command interpreters, and some command
14310 infrastructure to allow users or user interface writers to switch
14311 between interpreters or run commands in other interpreters.
14313 @value{GDBN} currently supports two command interpreters, the console
14314 interpreter (sometimes called the command-line interpreter or @sc{cli})
14315 and the machine interface interpreter (or @sc{gdb/mi}). This manual
14316 describes both of these interfaces in great detail.
14318 By default, @value{GDBN} will start with the console interpreter.
14319 However, the user may choose to start @value{GDBN} with another
14320 interpreter by specifying the @option{-i} or @option{--interpreter}
14321 startup options. Defined interpreters include:
14325 @cindex console interpreter
14326 The traditional console or command-line interpreter. This is the most often
14327 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
14328 @value{GDBN} will use this interpreter.
14331 @cindex mi interpreter
14332 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
14333 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
14334 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
14338 @cindex mi2 interpreter
14339 The current @sc{gdb/mi} interface.
14342 @cindex mi1 interpreter
14343 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
14347 @cindex invoke another interpreter
14348 The interpreter being used by @value{GDBN} may not be dynamically
14349 switched at runtime. Although possible, this could lead to a very
14350 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
14351 enters the command "interpreter-set console" in a console view,
14352 @value{GDBN} would switch to using the console interpreter, rendering
14353 the IDE inoperable!
14355 @kindex interpreter-exec
14356 Although you may only choose a single interpreter at startup, you may execute
14357 commands in any interpreter from the current interpreter using the appropriate
14358 command. If you are running the console interpreter, simply use the
14359 @code{interpreter-exec} command:
14362 interpreter-exec mi "-data-list-register-names"
14365 @sc{gdb/mi} has a similar command, although it is only available in versions of
14366 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
14369 @chapter @value{GDBN} Text User Interface
14371 @cindex Text User Interface
14374 * TUI Overview:: TUI overview
14375 * TUI Keys:: TUI key bindings
14376 * TUI Single Key Mode:: TUI single key mode
14377 * TUI Commands:: TUI specific commands
14378 * TUI Configuration:: TUI configuration variables
14381 The @value{GDBN} Text User Interface, TUI in short, is a terminal
14382 interface which uses the @code{curses} library to show the source
14383 file, the assembly output, the program registers and @value{GDBN}
14384 commands in separate text windows.
14386 The TUI is enabled by invoking @value{GDBN} using either
14388 @samp{gdbtui} or @samp{gdb -tui}.
14391 @section TUI overview
14393 The TUI has two display modes that can be switched while
14398 A curses (or TUI) mode in which it displays several text
14399 windows on the terminal.
14402 A standard mode which corresponds to the @value{GDBN} configured without
14406 In the TUI mode, @value{GDBN} can display several text window
14411 This window is the @value{GDBN} command window with the @value{GDBN}
14412 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
14413 managed using readline but through the TUI. The @emph{command}
14414 window is always visible.
14417 The source window shows the source file of the program. The current
14418 line as well as active breakpoints are displayed in this window.
14421 The assembly window shows the disassembly output of the program.
14424 This window shows the processor registers. It detects when
14425 a register is changed and when this is the case, registers that have
14426 changed are highlighted.
14430 The source and assembly windows show the current program position
14431 by highlighting the current line and marking them with the @samp{>} marker.
14432 Breakpoints are also indicated with two markers. A first one
14433 indicates the breakpoint type:
14437 Breakpoint which was hit at least once.
14440 Breakpoint which was never hit.
14443 Hardware breakpoint which was hit at least once.
14446 Hardware breakpoint which was never hit.
14450 The second marker indicates whether the breakpoint is enabled or not:
14454 Breakpoint is enabled.
14457 Breakpoint is disabled.
14461 The source, assembly and register windows are attached to the thread
14462 and the frame position. They are updated when the current thread
14463 changes, when the frame changes or when the program counter changes.
14464 These three windows are arranged by the TUI according to several
14465 layouts. The layout defines which of these three windows are visible.
14466 The following layouts are available:
14476 source and assembly
14479 source and registers
14482 assembly and registers
14486 On top of the command window a status line gives various information
14487 concerning the current process begin debugged. The status line is
14488 updated when the information it shows changes. The following fields
14493 Indicates the current gdb target
14494 (@pxref{Targets, ,Specifying a Debugging Target}).
14497 Gives information about the current process or thread number.
14498 When no process is being debugged, this field is set to @code{No process}.
14501 Gives the current function name for the selected frame.
14502 The name is demangled if demangling is turned on (@pxref{Print Settings}).
14503 When there is no symbol corresponding to the current program counter
14504 the string @code{??} is displayed.
14507 Indicates the current line number for the selected frame.
14508 When the current line number is not known the string @code{??} is displayed.
14511 Indicates the current program counter address.
14516 @section TUI Key Bindings
14517 @cindex TUI key bindings
14519 The TUI installs several key bindings in the readline keymaps
14520 (@pxref{Command Line Editing}).
14521 They allow to leave or enter in the TUI mode or they operate
14522 directly on the TUI layout and windows. The TUI also provides
14523 a @emph{SingleKey} keymap which binds several keys directly to
14524 @value{GDBN} commands. The following key bindings
14525 are installed for both TUI mode and the @value{GDBN} standard mode.
14534 Enter or leave the TUI mode. When the TUI mode is left,
14535 the curses window management is left and @value{GDBN} operates using
14536 its standard mode writing on the terminal directly. When the TUI
14537 mode is entered, the control is given back to the curses windows.
14538 The screen is then refreshed.
14542 Use a TUI layout with only one window. The layout will
14543 either be @samp{source} or @samp{assembly}. When the TUI mode
14544 is not active, it will switch to the TUI mode.
14546 Think of this key binding as the Emacs @kbd{C-x 1} binding.
14550 Use a TUI layout with at least two windows. When the current
14551 layout shows already two windows, a next layout with two windows is used.
14552 When a new layout is chosen, one window will always be common to the
14553 previous layout and the new one.
14555 Think of it as the Emacs @kbd{C-x 2} binding.
14559 Change the active window. The TUI associates several key bindings
14560 (like scrolling and arrow keys) to the active window. This command
14561 gives the focus to the next TUI window.
14563 Think of it as the Emacs @kbd{C-x o} binding.
14567 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
14568 (@pxref{TUI Single Key Mode}).
14572 The following key bindings are handled only by the TUI mode:
14577 Scroll the active window one page up.
14581 Scroll the active window one page down.
14585 Scroll the active window one line up.
14589 Scroll the active window one line down.
14593 Scroll the active window one column left.
14597 Scroll the active window one column right.
14601 Refresh the screen.
14605 In the TUI mode, the arrow keys are used by the active window
14606 for scrolling. This means they are available for readline when the
14607 active window is the command window. When the command window
14608 does not have the focus, it is necessary to use other readline
14609 key bindings such as @key{C-p}, @key{C-n}, @key{C-b} and @key{C-f}.
14611 @node TUI Single Key Mode
14612 @section TUI Single Key Mode
14613 @cindex TUI single key mode
14615 The TUI provides a @emph{SingleKey} mode in which it installs a particular
14616 key binding in the readline keymaps to connect single keys to
14620 @kindex c @r{(SingleKey TUI key)}
14624 @kindex d @r{(SingleKey TUI key)}
14628 @kindex f @r{(SingleKey TUI key)}
14632 @kindex n @r{(SingleKey TUI key)}
14636 @kindex q @r{(SingleKey TUI key)}
14638 exit the @emph{SingleKey} mode.
14640 @kindex r @r{(SingleKey TUI key)}
14644 @kindex s @r{(SingleKey TUI key)}
14648 @kindex u @r{(SingleKey TUI key)}
14652 @kindex v @r{(SingleKey TUI key)}
14656 @kindex w @r{(SingleKey TUI key)}
14662 Other keys temporarily switch to the @value{GDBN} command prompt.
14663 The key that was pressed is inserted in the editing buffer so that
14664 it is possible to type most @value{GDBN} commands without interaction
14665 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
14666 @emph{SingleKey} mode is restored. The only way to permanently leave
14667 this mode is by hitting @key{q} or @samp{@key{C-x} @key{s}}.
14671 @section TUI specific commands
14672 @cindex TUI commands
14674 The TUI has specific commands to control the text windows.
14675 These commands are always available, that is they do not depend on
14676 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
14677 is in the standard mode, using these commands will automatically switch
14683 List and give the size of all displayed windows.
14687 Display the next layout.
14690 Display the previous layout.
14693 Display the source window only.
14696 Display the assembly window only.
14699 Display the source and assembly window.
14702 Display the register window together with the source or assembly window.
14704 @item focus next | prev | src | asm | regs | split
14706 Set the focus to the named window.
14707 This command allows to change the active window so that scrolling keys
14708 can be affected to another window.
14712 Refresh the screen. This is similar to using @key{C-L} key.
14714 @item tui reg float
14716 Show the floating point registers in the register window.
14718 @item tui reg general
14719 Show the general registers in the register window.
14722 Show the next register group. The list of register groups as well as
14723 their order is target specific. The predefined register groups are the
14724 following: @code{general}, @code{float}, @code{system}, @code{vector},
14725 @code{all}, @code{save}, @code{restore}.
14727 @item tui reg system
14728 Show the system registers in the register window.
14732 Update the source window and the current execution point.
14734 @item winheight @var{name} +@var{count}
14735 @itemx winheight @var{name} -@var{count}
14737 Change the height of the window @var{name} by @var{count}
14738 lines. Positive counts increase the height, while negative counts
14743 @node TUI Configuration
14744 @section TUI configuration variables
14745 @cindex TUI configuration variables
14747 The TUI has several configuration variables that control the
14748 appearance of windows on the terminal.
14751 @item set tui border-kind @var{kind}
14752 @kindex set tui border-kind
14753 Select the border appearance for the source, assembly and register windows.
14754 The possible values are the following:
14757 Use a space character to draw the border.
14760 Use ascii characters + - and | to draw the border.
14763 Use the Alternate Character Set to draw the border. The border is
14764 drawn using character line graphics if the terminal supports them.
14768 @item set tui active-border-mode @var{mode}
14769 @kindex set tui active-border-mode
14770 Select the attributes to display the border of the active window.
14771 The possible values are @code{normal}, @code{standout}, @code{reverse},
14772 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
14774 @item set tui border-mode @var{mode}
14775 @kindex set tui border-mode
14776 Select the attributes to display the border of other windows.
14777 The @var{mode} can be one of the following:
14780 Use normal attributes to display the border.
14786 Use reverse video mode.
14789 Use half bright mode.
14791 @item half-standout
14792 Use half bright and standout mode.
14795 Use extra bright or bold mode.
14797 @item bold-standout
14798 Use extra bright or bold and standout mode.
14805 @chapter Using @value{GDBN} under @sc{gnu} Emacs
14808 @cindex @sc{gnu} Emacs
14809 A special interface allows you to use @sc{gnu} Emacs to view (and
14810 edit) the source files for the program you are debugging with
14813 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
14814 executable file you want to debug as an argument. This command starts
14815 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
14816 created Emacs buffer.
14817 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
14819 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
14824 All ``terminal'' input and output goes through the Emacs buffer.
14827 This applies both to @value{GDBN} commands and their output, and to the input
14828 and output done by the program you are debugging.
14830 This is useful because it means that you can copy the text of previous
14831 commands and input them again; you can even use parts of the output
14834 All the facilities of Emacs' Shell mode are available for interacting
14835 with your program. In particular, you can send signals the usual
14836 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
14841 @value{GDBN} displays source code through Emacs.
14844 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
14845 source file for that frame and puts an arrow (@samp{=>}) at the
14846 left margin of the current line. Emacs uses a separate buffer for
14847 source display, and splits the screen to show both your @value{GDBN} session
14850 Explicit @value{GDBN} @code{list} or search commands still produce output as
14851 usual, but you probably have no reason to use them from Emacs.
14853 If you specify an absolute file name when prompted for the @kbd{M-x
14854 gdb} argument, then Emacs sets your current working directory to where
14855 your program resides. If you only specify the file name, then Emacs
14856 sets your current working directory to to the directory associated
14857 with the previous buffer. In this case, @value{GDBN} may find your
14858 program by searching your environment's @code{PATH} variable, but on
14859 some operating systems it might not find the source. So, although the
14860 @value{GDBN} input and output session proceeds normally, the auxiliary
14861 buffer does not display the current source and line of execution.
14863 The initial working directory of @value{GDBN} is printed on the top
14864 line of the @value{GDBN} I/O buffer and this serves as a default for
14865 the commands that specify files for @value{GDBN} to operate
14866 on. @xref{Files, ,Commands to specify files}.
14868 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
14869 need to call @value{GDBN} by a different name (for example, if you
14870 keep several configurations around, with different names) you can
14871 customize the Emacs variable @code{gud-gdb-command-name} to run the
14874 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
14875 addition to the standard Shell mode commands:
14879 Describe the features of Emacs' @value{GDBN} Mode.
14882 Execute to another source line, like the @value{GDBN} @code{step} command; also
14883 update the display window to show the current file and location.
14886 Execute to next source line in this function, skipping all function
14887 calls, like the @value{GDBN} @code{next} command. Then update the display window
14888 to show the current file and location.
14891 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
14892 display window accordingly.
14895 Execute until exit from the selected stack frame, like the @value{GDBN}
14896 @code{finish} command.
14899 Continue execution of your program, like the @value{GDBN} @code{continue}
14903 Go up the number of frames indicated by the numeric argument
14904 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
14905 like the @value{GDBN} @code{up} command.
14908 Go down the number of frames indicated by the numeric argument, like the
14909 @value{GDBN} @code{down} command.
14912 In any source file, the Emacs command @kbd{C-x SPC} (@code{gud-break})
14913 tells @value{GDBN} to set a breakpoint on the source line point is on.
14915 If you type @kbd{M-x speedbar}, then Emacs displays a separate frame which
14916 shows a backtrace when the @value{GDBN} I/O buffer is current. Move
14917 point to any frame in the stack and type @key{RET} to make it become the
14918 current frame and display the associated source in the source buffer.
14919 Alternatively, click @kbd{Mouse-2} to make the selected frame become the
14922 If you accidentally delete the source-display buffer, an easy way to get
14923 it back is to type the command @code{f} in the @value{GDBN} buffer, to
14924 request a frame display; when you run under Emacs, this recreates
14925 the source buffer if necessary to show you the context of the current
14928 The source files displayed in Emacs are in ordinary Emacs buffers
14929 which are visiting the source files in the usual way. You can edit
14930 the files with these buffers if you wish; but keep in mind that @value{GDBN}
14931 communicates with Emacs in terms of line numbers. If you add or
14932 delete lines from the text, the line numbers that @value{GDBN} knows cease
14933 to correspond properly with the code.
14935 The description given here is for GNU Emacs version 21.3 and a more
14936 detailed description of its interaction with @value{GDBN} is given in
14937 the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu} Emacs Manual}).
14939 @c The following dropped because Epoch is nonstandard. Reactivate
14940 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
14942 @kindex Emacs Epoch environment
14946 Version 18 of @sc{gnu} Emacs has a built-in window system
14947 called the @code{epoch}
14948 environment. Users of this environment can use a new command,
14949 @code{inspect} which performs identically to @code{print} except that
14950 each value is printed in its own window.
14955 @chapter The @sc{gdb/mi} Interface
14957 @unnumberedsec Function and Purpose
14959 @cindex @sc{gdb/mi}, its purpose
14960 @sc{gdb/mi} is a line based machine oriented text interface to @value{GDBN}. It is
14961 specifically intended to support the development of systems which use
14962 the debugger as just one small component of a larger system.
14964 This chapter is a specification of the @sc{gdb/mi} interface. It is written
14965 in the form of a reference manual.
14967 Note that @sc{gdb/mi} is still under construction, so some of the
14968 features described below are incomplete and subject to change.
14970 @unnumberedsec Notation and Terminology
14972 @cindex notational conventions, for @sc{gdb/mi}
14973 This chapter uses the following notation:
14977 @code{|} separates two alternatives.
14980 @code{[ @var{something} ]} indicates that @var{something} is optional:
14981 it may or may not be given.
14984 @code{( @var{group} )*} means that @var{group} inside the parentheses
14985 may repeat zero or more times.
14988 @code{( @var{group} )+} means that @var{group} inside the parentheses
14989 may repeat one or more times.
14992 @code{"@var{string}"} means a literal @var{string}.
14996 @heading Dependencies
14999 @heading Acknowledgments
15001 In alphabetic order: Andrew Cagney, Fernando Nasser, Stan Shebs and
15005 * GDB/MI Command Syntax::
15006 * GDB/MI Compatibility with CLI::
15007 * GDB/MI Output Records::
15008 * GDB/MI Command Description Format::
15009 * GDB/MI Breakpoint Table Commands::
15010 * GDB/MI Data Manipulation::
15011 * GDB/MI Program Control::
15012 * GDB/MI Miscellaneous Commands::
15014 * GDB/MI Kod Commands::
15015 * GDB/MI Memory Overlay Commands::
15016 * GDB/MI Signal Handling Commands::
15018 * GDB/MI Stack Manipulation::
15019 * GDB/MI Symbol Query::
15020 * GDB/MI Target Manipulation::
15021 * GDB/MI Thread Commands::
15022 * GDB/MI Tracepoint Commands::
15023 * GDB/MI Variable Objects::
15026 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15027 @node GDB/MI Command Syntax
15028 @section @sc{gdb/mi} Command Syntax
15031 * GDB/MI Input Syntax::
15032 * GDB/MI Output Syntax::
15033 * GDB/MI Simple Examples::
15036 @node GDB/MI Input Syntax
15037 @subsection @sc{gdb/mi} Input Syntax
15039 @cindex input syntax for @sc{gdb/mi}
15040 @cindex @sc{gdb/mi}, input syntax
15042 @item @var{command} @expansion{}
15043 @code{@var{cli-command} | @var{mi-command}}
15045 @item @var{cli-command} @expansion{}
15046 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
15047 @var{cli-command} is any existing @value{GDBN} CLI command.
15049 @item @var{mi-command} @expansion{}
15050 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
15051 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
15053 @item @var{token} @expansion{}
15054 "any sequence of digits"
15056 @item @var{option} @expansion{}
15057 @code{"-" @var{parameter} [ " " @var{parameter} ]}
15059 @item @var{parameter} @expansion{}
15060 @code{@var{non-blank-sequence} | @var{c-string}}
15062 @item @var{operation} @expansion{}
15063 @emph{any of the operations described in this chapter}
15065 @item @var{non-blank-sequence} @expansion{}
15066 @emph{anything, provided it doesn't contain special characters such as
15067 "-", @var{nl}, """ and of course " "}
15069 @item @var{c-string} @expansion{}
15070 @code{""" @var{seven-bit-iso-c-string-content} """}
15072 @item @var{nl} @expansion{}
15081 The CLI commands are still handled by the @sc{mi} interpreter; their
15082 output is described below.
15085 The @code{@var{token}}, when present, is passed back when the command
15089 Some @sc{mi} commands accept optional arguments as part of the parameter
15090 list. Each option is identified by a leading @samp{-} (dash) and may be
15091 followed by an optional argument parameter. Options occur first in the
15092 parameter list and can be delimited from normal parameters using
15093 @samp{--} (this is useful when some parameters begin with a dash).
15100 We want easy access to the existing CLI syntax (for debugging).
15103 We want it to be easy to spot a @sc{mi} operation.
15106 @node GDB/MI Output Syntax
15107 @subsection @sc{gdb/mi} Output Syntax
15109 @cindex output syntax of @sc{gdb/mi}
15110 @cindex @sc{gdb/mi}, output syntax
15111 The output from @sc{gdb/mi} consists of zero or more out-of-band records
15112 followed, optionally, by a single result record. This result record
15113 is for the most recent command. The sequence of output records is
15114 terminated by @samp{(@value{GDBP})}.
15116 If an input command was prefixed with a @code{@var{token}} then the
15117 corresponding output for that command will also be prefixed by that same
15121 @item @var{output} @expansion{}
15122 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(@value{GDBP})" @var{nl}}
15124 @item @var{result-record} @expansion{}
15125 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
15127 @item @var{out-of-band-record} @expansion{}
15128 @code{@var{async-record} | @var{stream-record}}
15130 @item @var{async-record} @expansion{}
15131 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
15133 @item @var{exec-async-output} @expansion{}
15134 @code{[ @var{token} ] "*" @var{async-output}}
15136 @item @var{status-async-output} @expansion{}
15137 @code{[ @var{token} ] "+" @var{async-output}}
15139 @item @var{notify-async-output} @expansion{}
15140 @code{[ @var{token} ] "=" @var{async-output}}
15142 @item @var{async-output} @expansion{}
15143 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
15145 @item @var{result-class} @expansion{}
15146 @code{"done" | "running" | "connected" | "error" | "exit"}
15148 @item @var{async-class} @expansion{}
15149 @code{"stopped" | @var{others}} (where @var{others} will be added
15150 depending on the needs---this is still in development).
15152 @item @var{result} @expansion{}
15153 @code{ @var{variable} "=" @var{value}}
15155 @item @var{variable} @expansion{}
15156 @code{ @var{string} }
15158 @item @var{value} @expansion{}
15159 @code{ @var{const} | @var{tuple} | @var{list} }
15161 @item @var{const} @expansion{}
15162 @code{@var{c-string}}
15164 @item @var{tuple} @expansion{}
15165 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
15167 @item @var{list} @expansion{}
15168 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
15169 @var{result} ( "," @var{result} )* "]" }
15171 @item @var{stream-record} @expansion{}
15172 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
15174 @item @var{console-stream-output} @expansion{}
15175 @code{"~" @var{c-string}}
15177 @item @var{target-stream-output} @expansion{}
15178 @code{"@@" @var{c-string}}
15180 @item @var{log-stream-output} @expansion{}
15181 @code{"&" @var{c-string}}
15183 @item @var{nl} @expansion{}
15186 @item @var{token} @expansion{}
15187 @emph{any sequence of digits}.
15195 All output sequences end in a single line containing a period.
15198 The @code{@var{token}} is from the corresponding request. If an execution
15199 command is interrupted by the @samp{-exec-interrupt} command, the
15200 @var{token} associated with the @samp{*stopped} message is the one of the
15201 original execution command, not the one of the interrupt command.
15204 @cindex status output in @sc{gdb/mi}
15205 @var{status-async-output} contains on-going status information about the
15206 progress of a slow operation. It can be discarded. All status output is
15207 prefixed by @samp{+}.
15210 @cindex async output in @sc{gdb/mi}
15211 @var{exec-async-output} contains asynchronous state change on the target
15212 (stopped, started, disappeared). All async output is prefixed by
15216 @cindex notify output in @sc{gdb/mi}
15217 @var{notify-async-output} contains supplementary information that the
15218 client should handle (e.g., a new breakpoint information). All notify
15219 output is prefixed by @samp{=}.
15222 @cindex console output in @sc{gdb/mi}
15223 @var{console-stream-output} is output that should be displayed as is in the
15224 console. It is the textual response to a CLI command. All the console
15225 output is prefixed by @samp{~}.
15228 @cindex target output in @sc{gdb/mi}
15229 @var{target-stream-output} is the output produced by the target program.
15230 All the target output is prefixed by @samp{@@}.
15233 @cindex log output in @sc{gdb/mi}
15234 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
15235 instance messages that should be displayed as part of an error log. All
15236 the log output is prefixed by @samp{&}.
15239 @cindex list output in @sc{gdb/mi}
15240 New @sc{gdb/mi} commands should only output @var{lists} containing
15246 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
15247 details about the various output records.
15249 @node GDB/MI Simple Examples
15250 @subsection Simple Examples of @sc{gdb/mi} Interaction
15251 @cindex @sc{gdb/mi}, simple examples
15253 This subsection presents several simple examples of interaction using
15254 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
15255 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
15256 the output received from @sc{gdb/mi}.
15258 @subsubheading Target Stop
15259 @c Ummm... There is no "-stop" command. This assumes async, no?
15260 Here's an example of stopping the inferior process:
15271 <- *stop,reason="stop",address="0x123",source="a.c:123"
15275 @subsubheading Simple CLI Command
15277 Here's an example of a simple CLI command being passed through
15278 @sc{gdb/mi} and on to the CLI.
15288 @subsubheading Command With Side Effects
15291 -> -symbol-file xyz.exe
15292 <- *breakpoint,nr="3",address="0x123",source="a.c:123"
15296 @subsubheading A Bad Command
15298 Here's what happens if you pass a non-existent command:
15302 <- ^error,msg="Undefined MI command: rubbish"
15306 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15307 @node GDB/MI Compatibility with CLI
15308 @section @sc{gdb/mi} Compatibility with CLI
15310 @cindex compatibility, @sc{gdb/mi} and CLI
15311 @cindex @sc{gdb/mi}, compatibility with CLI
15312 To help users familiar with @value{GDBN}'s existing CLI interface, @sc{gdb/mi}
15313 accepts existing CLI commands. As specified by the syntax, such
15314 commands can be directly entered into the @sc{gdb/mi} interface and @value{GDBN} will
15317 This mechanism is provided as an aid to developers of @sc{gdb/mi}
15318 clients and not as a reliable interface into the CLI. Since the command
15319 is being interpreteted in an environment that assumes @sc{gdb/mi}
15320 behaviour, the exact output of such commands is likely to end up being
15321 an un-supported hybrid of @sc{gdb/mi} and CLI output.
15323 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15324 @node GDB/MI Output Records
15325 @section @sc{gdb/mi} Output Records
15328 * GDB/MI Result Records::
15329 * GDB/MI Stream Records::
15330 * GDB/MI Out-of-band Records::
15333 @node GDB/MI Result Records
15334 @subsection @sc{gdb/mi} Result Records
15336 @cindex result records in @sc{gdb/mi}
15337 @cindex @sc{gdb/mi}, result records
15338 In addition to a number of out-of-band notifications, the response to a
15339 @sc{gdb/mi} command includes one of the following result indications:
15343 @item "^done" [ "," @var{results} ]
15344 The synchronous operation was successful, @code{@var{results}} are the return
15349 @c Is this one correct? Should it be an out-of-band notification?
15350 The asynchronous operation was successfully started. The target is
15353 @item "^error" "," @var{c-string}
15355 The operation failed. The @code{@var{c-string}} contains the corresponding
15359 @node GDB/MI Stream Records
15360 @subsection @sc{gdb/mi} Stream Records
15362 @cindex @sc{gdb/mi}, stream records
15363 @cindex stream records in @sc{gdb/mi}
15364 @value{GDBN} internally maintains a number of output streams: the console, the
15365 target, and the log. The output intended for each of these streams is
15366 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
15368 Each stream record begins with a unique @dfn{prefix character} which
15369 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
15370 Syntax}). In addition to the prefix, each stream record contains a
15371 @code{@var{string-output}}. This is either raw text (with an implicit new
15372 line) or a quoted C string (which does not contain an implicit newline).
15375 @item "~" @var{string-output}
15376 The console output stream contains text that should be displayed in the
15377 CLI console window. It contains the textual responses to CLI commands.
15379 @item "@@" @var{string-output}
15380 The target output stream contains any textual output from the running
15383 @item "&" @var{string-output}
15384 The log stream contains debugging messages being produced by @value{GDBN}'s
15388 @node GDB/MI Out-of-band Records
15389 @subsection @sc{gdb/mi} Out-of-band Records
15391 @cindex out-of-band records in @sc{gdb/mi}
15392 @cindex @sc{gdb/mi}, out-of-band records
15393 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
15394 additional changes that have occurred. Those changes can either be a
15395 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
15396 target activity (e.g., target stopped).
15398 The following is a preliminary list of possible out-of-band records.
15405 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15406 @node GDB/MI Command Description Format
15407 @section @sc{gdb/mi} Command Description Format
15409 The remaining sections describe blocks of commands. Each block of
15410 commands is laid out in a fashion similar to this section.
15412 Note the the line breaks shown in the examples are here only for
15413 readability. They don't appear in the real output.
15414 Also note that the commands with a non-available example (N.A.@:) are
15415 not yet implemented.
15417 @subheading Motivation
15419 The motivation for this collection of commands.
15421 @subheading Introduction
15423 A brief introduction to this collection of commands as a whole.
15425 @subheading Commands
15427 For each command in the block, the following is described:
15429 @subsubheading Synopsis
15432 -command @var{args}@dots{}
15435 @subsubheading @value{GDBN} Command
15437 The corresponding @value{GDBN} CLI command.
15439 @subsubheading Result
15441 @subsubheading Out-of-band
15443 @subsubheading Notes
15445 @subsubheading Example
15448 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15449 @node GDB/MI Breakpoint Table Commands
15450 @section @sc{gdb/mi} Breakpoint table commands
15452 @cindex breakpoint commands for @sc{gdb/mi}
15453 @cindex @sc{gdb/mi}, breakpoint commands
15454 This section documents @sc{gdb/mi} commands for manipulating
15457 @subheading The @code{-break-after} Command
15458 @findex -break-after
15460 @subsubheading Synopsis
15463 -break-after @var{number} @var{count}
15466 The breakpoint number @var{number} is not in effect until it has been
15467 hit @var{count} times. To see how this is reflected in the output of
15468 the @samp{-break-list} command, see the description of the
15469 @samp{-break-list} command below.
15471 @subsubheading @value{GDBN} Command
15473 The corresponding @value{GDBN} command is @samp{ignore}.
15475 @subsubheading Example
15480 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",line="5"@}
15487 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15488 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15489 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15490 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15491 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15492 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15493 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15494 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15495 addr="0x000100d0",func="main",file="hello.c",line="5",times="0",
15501 @subheading The @code{-break-catch} Command
15502 @findex -break-catch
15504 @subheading The @code{-break-commands} Command
15505 @findex -break-commands
15509 @subheading The @code{-break-condition} Command
15510 @findex -break-condition
15512 @subsubheading Synopsis
15515 -break-condition @var{number} @var{expr}
15518 Breakpoint @var{number} will stop the program only if the condition in
15519 @var{expr} is true. The condition becomes part of the
15520 @samp{-break-list} output (see the description of the @samp{-break-list}
15523 @subsubheading @value{GDBN} Command
15525 The corresponding @value{GDBN} command is @samp{condition}.
15527 @subsubheading Example
15531 -break-condition 1 1
15535 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15536 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15537 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15538 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15539 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15540 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15541 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15542 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15543 addr="0x000100d0",func="main",file="hello.c",line="5",cond="1",
15544 times="0",ignore="3"@}]@}
15548 @subheading The @code{-break-delete} Command
15549 @findex -break-delete
15551 @subsubheading Synopsis
15554 -break-delete ( @var{breakpoint} )+
15557 Delete the breakpoint(s) whose number(s) are specified in the argument
15558 list. This is obviously reflected in the breakpoint list.
15560 @subsubheading @value{GDBN} command
15562 The corresponding @value{GDBN} command is @samp{delete}.
15564 @subsubheading Example
15572 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
15573 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15574 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15575 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15576 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15577 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15578 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15583 @subheading The @code{-break-disable} Command
15584 @findex -break-disable
15586 @subsubheading Synopsis
15589 -break-disable ( @var{breakpoint} )+
15592 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
15593 break list is now set to @samp{n} for the named @var{breakpoint}(s).
15595 @subsubheading @value{GDBN} Command
15597 The corresponding @value{GDBN} command is @samp{disable}.
15599 @subsubheading Example
15607 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15608 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15609 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15610 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15611 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15612 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15613 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15614 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
15615 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
15619 @subheading The @code{-break-enable} Command
15620 @findex -break-enable
15622 @subsubheading Synopsis
15625 -break-enable ( @var{breakpoint} )+
15628 Enable (previously disabled) @var{breakpoint}(s).
15630 @subsubheading @value{GDBN} Command
15632 The corresponding @value{GDBN} command is @samp{enable}.
15634 @subsubheading Example
15642 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15643 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15644 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15645 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15646 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15647 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15648 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15649 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
15650 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
15654 @subheading The @code{-break-info} Command
15655 @findex -break-info
15657 @subsubheading Synopsis
15660 -break-info @var{breakpoint}
15664 Get information about a single breakpoint.
15666 @subsubheading @value{GDBN} command
15668 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
15670 @subsubheading Example
15673 @subheading The @code{-break-insert} Command
15674 @findex -break-insert
15676 @subsubheading Synopsis
15679 -break-insert [ -t ] [ -h ] [ -r ]
15680 [ -c @var{condition} ] [ -i @var{ignore-count} ]
15681 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
15685 If specified, @var{line}, can be one of:
15692 @item filename:linenum
15693 @item filename:function
15697 The possible optional parameters of this command are:
15701 Insert a tempoary breakpoint.
15703 Insert a hardware breakpoint.
15704 @item -c @var{condition}
15705 Make the breakpoint conditional on @var{condition}.
15706 @item -i @var{ignore-count}
15707 Initialize the @var{ignore-count}.
15709 Insert a regular breakpoint in all the functions whose names match the
15710 given regular expression. Other flags are not applicable to regular
15714 @subsubheading Result
15716 The result is in the form:
15719 ^done,bkptno="@var{number}",func="@var{funcname}",
15720 file="@var{filename}",line="@var{lineno}"
15724 where @var{number} is the @value{GDBN} number for this breakpoint, @var{funcname}
15725 is the name of the function where the breakpoint was inserted,
15726 @var{filename} is the name of the source file which contains this
15727 function, and @var{lineno} is the source line number within that file.
15729 Note: this format is open to change.
15730 @c An out-of-band breakpoint instead of part of the result?
15732 @subsubheading @value{GDBN} Command
15734 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
15735 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
15737 @subsubheading Example
15742 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
15744 -break-insert -t foo
15745 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",line="11"@}
15748 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15749 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15750 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15751 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15752 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15753 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15754 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15755 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15756 addr="0x0001072c", func="main",file="recursive2.c",line="4",times="0"@},
15757 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
15758 addr="0x00010774",func="foo",file="recursive2.c",line="11",times="0"@}]@}
15760 -break-insert -r foo.*
15761 ~int foo(int, int);
15762 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c",line="11"@}
15766 @subheading The @code{-break-list} Command
15767 @findex -break-list
15769 @subsubheading Synopsis
15775 Displays the list of inserted breakpoints, showing the following fields:
15779 number of the breakpoint
15781 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
15783 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
15786 is the breakpoint enabled or no: @samp{y} or @samp{n}
15788 memory location at which the breakpoint is set
15790 logical location of the breakpoint, expressed by function name, file
15793 number of times the breakpoint has been hit
15796 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
15797 @code{body} field is an empty list.
15799 @subsubheading @value{GDBN} Command
15801 The corresponding @value{GDBN} command is @samp{info break}.
15803 @subsubheading Example
15808 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15809 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15810 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15811 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15812 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15813 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15814 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15815 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15816 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
15817 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
15818 addr="0x00010114",func="foo",file="hello.c",line="13",times="0"@}]@}
15822 Here's an example of the result when there are no breakpoints:
15827 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
15828 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15829 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15830 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15831 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15832 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15833 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15838 @subheading The @code{-break-watch} Command
15839 @findex -break-watch
15841 @subsubheading Synopsis
15844 -break-watch [ -a | -r ]
15847 Create a watchpoint. With the @samp{-a} option it will create an
15848 @dfn{access} watchpoint, i.e. a watchpoint that triggers either on a
15849 read from or on a write to the memory location. With the @samp{-r}
15850 option, the watchpoint created is a @dfn{read} watchpoint, i.e. it will
15851 trigger only when the memory location is accessed for reading. Without
15852 either of the options, the watchpoint created is a regular watchpoint,
15853 i.e. it will trigger when the memory location is accessed for writing.
15854 @xref{Set Watchpoints, , Setting watchpoints}.
15856 Note that @samp{-break-list} will report a single list of watchpoints and
15857 breakpoints inserted.
15859 @subsubheading @value{GDBN} Command
15861 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
15864 @subsubheading Example
15866 Setting a watchpoint on a variable in the @code{main} function:
15871 ^done,wpt=@{number="2",exp="x"@}
15875 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
15876 value=@{old="-268439212",new="55"@},
15877 frame=@{func="main",args=[],file="recursive2.c",line="5"@}
15881 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
15882 the program execution twice: first for the variable changing value, then
15883 for the watchpoint going out of scope.
15888 ^done,wpt=@{number="5",exp="C"@}
15892 ^done,reason="watchpoint-trigger",
15893 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
15894 frame=@{func="callee4",args=[],
15895 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
15899 ^done,reason="watchpoint-scope",wpnum="5",
15900 frame=@{func="callee3",args=[@{name="strarg",
15901 value="0x11940 \"A string argument.\""@}],
15902 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
15906 Listing breakpoints and watchpoints, at different points in the program
15907 execution. Note that once the watchpoint goes out of scope, it is
15913 ^done,wpt=@{number="2",exp="C"@}
15916 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15917 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15918 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15919 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15920 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15921 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15922 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15923 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15924 addr="0x00010734",func="callee4",
15925 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
15926 bkpt=@{number="2",type="watchpoint",disp="keep",
15927 enabled="y",addr="",what="C",times="0"@}]@}
15931 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
15932 value=@{old="-276895068",new="3"@},
15933 frame=@{func="callee4",args=[],
15934 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
15937 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15938 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15939 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15940 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15941 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15942 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15943 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15944 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15945 addr="0x00010734",func="callee4",
15946 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
15947 bkpt=@{number="2",type="watchpoint",disp="keep",
15948 enabled="y",addr="",what="C",times="-5"@}]@}
15952 ^done,reason="watchpoint-scope",wpnum="2",
15953 frame=@{func="callee3",args=[@{name="strarg",
15954 value="0x11940 \"A string argument.\""@}],
15955 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
15958 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15959 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15960 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15961 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15962 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15963 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15964 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15965 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15966 addr="0x00010734",func="callee4",
15967 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@}]@}
15971 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15972 @node GDB/MI Data Manipulation
15973 @section @sc{gdb/mi} Data Manipulation
15975 @cindex data manipulation, in @sc{gdb/mi}
15976 @cindex @sc{gdb/mi}, data manipulation
15977 This section describes the @sc{gdb/mi} commands that manipulate data:
15978 examine memory and registers, evaluate expressions, etc.
15980 @c REMOVED FROM THE INTERFACE.
15981 @c @subheading -data-assign
15982 @c Change the value of a program variable. Plenty of side effects.
15983 @c @subsubheading GDB command
15985 @c @subsubheading Example
15988 @subheading The @code{-data-disassemble} Command
15989 @findex -data-disassemble
15991 @subsubheading Synopsis
15995 [ -s @var{start-addr} -e @var{end-addr} ]
15996 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
16004 @item @var{start-addr}
16005 is the beginning address (or @code{$pc})
16006 @item @var{end-addr}
16008 @item @var{filename}
16009 is the name of the file to disassemble
16010 @item @var{linenum}
16011 is the line number to disassemble around
16013 is the the number of disassembly lines to be produced. If it is -1,
16014 the whole function will be disassembled, in case no @var{end-addr} is
16015 specified. If @var{end-addr} is specified as a non-zero value, and
16016 @var{lines} is lower than the number of disassembly lines between
16017 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
16018 displayed; if @var{lines} is higher than the number of lines between
16019 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
16022 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
16026 @subsubheading Result
16028 The output for each instruction is composed of four fields:
16037 Note that whatever included in the instruction field, is not manipulated
16038 directely by @sc{gdb/mi}, i.e. it is not possible to adjust its format.
16040 @subsubheading @value{GDBN} Command
16042 There's no direct mapping from this command to the CLI.
16044 @subsubheading Example
16046 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
16050 -data-disassemble -s $pc -e "$pc + 20" -- 0
16053 @{address="0x000107c0",func-name="main",offset="4",
16054 inst="mov 2, %o0"@},
16055 @{address="0x000107c4",func-name="main",offset="8",
16056 inst="sethi %hi(0x11800), %o2"@},
16057 @{address="0x000107c8",func-name="main",offset="12",
16058 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
16059 @{address="0x000107cc",func-name="main",offset="16",
16060 inst="sethi %hi(0x11800), %o2"@},
16061 @{address="0x000107d0",func-name="main",offset="20",
16062 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
16066 Disassemble the whole @code{main} function. Line 32 is part of
16070 -data-disassemble -f basics.c -l 32 -- 0
16072 @{address="0x000107bc",func-name="main",offset="0",
16073 inst="save %sp, -112, %sp"@},
16074 @{address="0x000107c0",func-name="main",offset="4",
16075 inst="mov 2, %o0"@},
16076 @{address="0x000107c4",func-name="main",offset="8",
16077 inst="sethi %hi(0x11800), %o2"@},
16079 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
16080 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
16084 Disassemble 3 instructions from the start of @code{main}:
16088 -data-disassemble -f basics.c -l 32 -n 3 -- 0
16090 @{address="0x000107bc",func-name="main",offset="0",
16091 inst="save %sp, -112, %sp"@},
16092 @{address="0x000107c0",func-name="main",offset="4",
16093 inst="mov 2, %o0"@},
16094 @{address="0x000107c4",func-name="main",offset="8",
16095 inst="sethi %hi(0x11800), %o2"@}]
16099 Disassemble 3 instructions from the start of @code{main} in mixed mode:
16103 -data-disassemble -f basics.c -l 32 -n 3 -- 1
16105 src_and_asm_line=@{line="31",
16106 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
16107 testsuite/gdb.mi/basics.c",line_asm_insn=[
16108 @{address="0x000107bc",func-name="main",offset="0",
16109 inst="save %sp, -112, %sp"@}]@},
16110 src_and_asm_line=@{line="32",
16111 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
16112 testsuite/gdb.mi/basics.c",line_asm_insn=[
16113 @{address="0x000107c0",func-name="main",offset="4",
16114 inst="mov 2, %o0"@},
16115 @{address="0x000107c4",func-name="main",offset="8",
16116 inst="sethi %hi(0x11800), %o2"@}]@}]
16121 @subheading The @code{-data-evaluate-expression} Command
16122 @findex -data-evaluate-expression
16124 @subsubheading Synopsis
16127 -data-evaluate-expression @var{expr}
16130 Evaluate @var{expr} as an expression. The expression could contain an
16131 inferior function call. The function call will execute synchronously.
16132 If the expression contains spaces, it must be enclosed in double quotes.
16134 @subsubheading @value{GDBN} Command
16136 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
16137 @samp{call}. In @code{gdbtk} only, there's a corresponding
16138 @samp{gdb_eval} command.
16140 @subsubheading Example
16142 In the following example, the numbers that precede the commands are the
16143 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
16144 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
16148 211-data-evaluate-expression A
16151 311-data-evaluate-expression &A
16152 311^done,value="0xefffeb7c"
16154 411-data-evaluate-expression A+3
16157 511-data-evaluate-expression "A + 3"
16163 @subheading The @code{-data-list-changed-registers} Command
16164 @findex -data-list-changed-registers
16166 @subsubheading Synopsis
16169 -data-list-changed-registers
16172 Display a list of the registers that have changed.
16174 @subsubheading @value{GDBN} Command
16176 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
16177 has the corresponding command @samp{gdb_changed_register_list}.
16179 @subsubheading Example
16181 On a PPC MBX board:
16189 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
16190 args=[],file="try.c",line="5"@}
16192 -data-list-changed-registers
16193 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
16194 "10","11","13","14","15","16","17","18","19","20","21","22","23",
16195 "24","25","26","27","28","30","31","64","65","66","67","69"]
16200 @subheading The @code{-data-list-register-names} Command
16201 @findex -data-list-register-names
16203 @subsubheading Synopsis
16206 -data-list-register-names [ ( @var{regno} )+ ]
16209 Show a list of register names for the current target. If no arguments
16210 are given, it shows a list of the names of all the registers. If
16211 integer numbers are given as arguments, it will print a list of the
16212 names of the registers corresponding to the arguments. To ensure
16213 consistency between a register name and its number, the output list may
16214 include empty register names.
16216 @subsubheading @value{GDBN} Command
16218 @value{GDBN} does not have a command which corresponds to
16219 @samp{-data-list-register-names}. In @code{gdbtk} there is a
16220 corresponding command @samp{gdb_regnames}.
16222 @subsubheading Example
16224 For the PPC MBX board:
16227 -data-list-register-names
16228 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
16229 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
16230 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
16231 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
16232 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
16233 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
16234 "", "pc","ps","cr","lr","ctr","xer"]
16236 -data-list-register-names 1 2 3
16237 ^done,register-names=["r1","r2","r3"]
16241 @subheading The @code{-data-list-register-values} Command
16242 @findex -data-list-register-values
16244 @subsubheading Synopsis
16247 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
16250 Display the registers' contents. @var{fmt} is the format according to
16251 which the registers' contents are to be returned, followed by an optional
16252 list of numbers specifying the registers to display. A missing list of
16253 numbers indicates that the contents of all the registers must be returned.
16255 Allowed formats for @var{fmt} are:
16272 @subsubheading @value{GDBN} Command
16274 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
16275 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
16277 @subsubheading Example
16279 For a PPC MBX board (note: line breaks are for readability only, they
16280 don't appear in the actual output):
16284 -data-list-register-values r 64 65
16285 ^done,register-values=[@{number="64",value="0xfe00a300"@},
16286 @{number="65",value="0x00029002"@}]
16288 -data-list-register-values x
16289 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
16290 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
16291 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
16292 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
16293 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
16294 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
16295 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
16296 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
16297 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
16298 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
16299 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
16300 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
16301 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
16302 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
16303 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
16304 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
16305 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
16306 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
16307 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
16308 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
16309 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
16310 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
16311 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
16312 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
16313 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
16314 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
16315 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
16316 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
16317 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
16318 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
16319 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
16320 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
16321 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
16322 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
16323 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
16324 @{number="69",value="0x20002b03"@}]
16329 @subheading The @code{-data-read-memory} Command
16330 @findex -data-read-memory
16332 @subsubheading Synopsis
16335 -data-read-memory [ -o @var{byte-offset} ]
16336 @var{address} @var{word-format} @var{word-size}
16337 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
16344 @item @var{address}
16345 An expression specifying the address of the first memory word to be
16346 read. Complex expressions containing embedded white space should be
16347 quoted using the C convention.
16349 @item @var{word-format}
16350 The format to be used to print the memory words. The notation is the
16351 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
16354 @item @var{word-size}
16355 The size of each memory word in bytes.
16357 @item @var{nr-rows}
16358 The number of rows in the output table.
16360 @item @var{nr-cols}
16361 The number of columns in the output table.
16364 If present, indicates that each row should include an @sc{ascii} dump. The
16365 value of @var{aschar} is used as a padding character when a byte is not a
16366 member of the printable @sc{ascii} character set (printable @sc{ascii}
16367 characters are those whose code is between 32 and 126, inclusively).
16369 @item @var{byte-offset}
16370 An offset to add to the @var{address} before fetching memory.
16373 This command displays memory contents as a table of @var{nr-rows} by
16374 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
16375 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
16376 (returned as @samp{total-bytes}). Should less than the requested number
16377 of bytes be returned by the target, the missing words are identified
16378 using @samp{N/A}. The number of bytes read from the target is returned
16379 in @samp{nr-bytes} and the starting address used to read memory in
16382 The address of the next/previous row or page is available in
16383 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
16386 @subsubheading @value{GDBN} Command
16388 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
16389 @samp{gdb_get_mem} memory read command.
16391 @subsubheading Example
16393 Read six bytes of memory starting at @code{bytes+6} but then offset by
16394 @code{-6} bytes. Format as three rows of two columns. One byte per
16395 word. Display each word in hex.
16399 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
16400 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
16401 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
16402 prev-page="0x0000138a",memory=[
16403 @{addr="0x00001390",data=["0x00","0x01"]@},
16404 @{addr="0x00001392",data=["0x02","0x03"]@},
16405 @{addr="0x00001394",data=["0x04","0x05"]@}]
16409 Read two bytes of memory starting at address @code{shorts + 64} and
16410 display as a single word formatted in decimal.
16414 5-data-read-memory shorts+64 d 2 1 1
16415 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
16416 next-row="0x00001512",prev-row="0x0000150e",
16417 next-page="0x00001512",prev-page="0x0000150e",memory=[
16418 @{addr="0x00001510",data=["128"]@}]
16422 Read thirty two bytes of memory starting at @code{bytes+16} and format
16423 as eight rows of four columns. Include a string encoding with @samp{x}
16424 used as the non-printable character.
16428 4-data-read-memory bytes+16 x 1 8 4 x
16429 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
16430 next-row="0x000013c0",prev-row="0x0000139c",
16431 next-page="0x000013c0",prev-page="0x00001380",memory=[
16432 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
16433 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
16434 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
16435 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
16436 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
16437 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
16438 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
16439 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
16443 @subheading The @code{-display-delete} Command
16444 @findex -display-delete
16446 @subsubheading Synopsis
16449 -display-delete @var{number}
16452 Delete the display @var{number}.
16454 @subsubheading @value{GDBN} Command
16456 The corresponding @value{GDBN} command is @samp{delete display}.
16458 @subsubheading Example
16462 @subheading The @code{-display-disable} Command
16463 @findex -display-disable
16465 @subsubheading Synopsis
16468 -display-disable @var{number}
16471 Disable display @var{number}.
16473 @subsubheading @value{GDBN} Command
16475 The corresponding @value{GDBN} command is @samp{disable display}.
16477 @subsubheading Example
16481 @subheading The @code{-display-enable} Command
16482 @findex -display-enable
16484 @subsubheading Synopsis
16487 -display-enable @var{number}
16490 Enable display @var{number}.
16492 @subsubheading @value{GDBN} Command
16494 The corresponding @value{GDBN} command is @samp{enable display}.
16496 @subsubheading Example
16500 @subheading The @code{-display-insert} Command
16501 @findex -display-insert
16503 @subsubheading Synopsis
16506 -display-insert @var{expression}
16509 Display @var{expression} every time the program stops.
16511 @subsubheading @value{GDBN} Command
16513 The corresponding @value{GDBN} command is @samp{display}.
16515 @subsubheading Example
16519 @subheading The @code{-display-list} Command
16520 @findex -display-list
16522 @subsubheading Synopsis
16528 List the displays. Do not show the current values.
16530 @subsubheading @value{GDBN} Command
16532 The corresponding @value{GDBN} command is @samp{info display}.
16534 @subsubheading Example
16538 @subheading The @code{-environment-cd} Command
16539 @findex -environment-cd
16541 @subsubheading Synopsis
16544 -environment-cd @var{pathdir}
16547 Set @value{GDBN}'s working directory.
16549 @subsubheading @value{GDBN} Command
16551 The corresponding @value{GDBN} command is @samp{cd}.
16553 @subsubheading Example
16557 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
16563 @subheading The @code{-environment-directory} Command
16564 @findex -environment-directory
16566 @subsubheading Synopsis
16569 -environment-directory [ -r ] [ @var{pathdir} ]+
16572 Add directories @var{pathdir} to beginning of search path for source files.
16573 If the @samp{-r} option is used, the search path is reset to the default
16574 search path. If directories @var{pathdir} are supplied in addition to the
16575 @samp{-r} option, the search path is first reset and then addition
16577 Multiple directories may be specified, separated by blanks. Specifying
16578 multiple directories in a single command
16579 results in the directories added to the beginning of the
16580 search path in the same order they were presented in the command.
16581 If blanks are needed as
16582 part of a directory name, double-quotes should be used around
16583 the name. In the command output, the path will show up separated
16584 by the system directory-separator character. The directory-seperator
16585 character must not be used
16586 in any directory name.
16587 If no directories are specified, the current search path is displayed.
16589 @subsubheading @value{GDBN} Command
16591 The corresponding @value{GDBN} command is @samp{dir}.
16593 @subsubheading Example
16597 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
16598 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
16600 -environment-directory ""
16601 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
16603 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
16604 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
16606 -environment-directory -r
16607 ^done,source-path="$cdir:$cwd"
16612 @subheading The @code{-environment-path} Command
16613 @findex -environment-path
16615 @subsubheading Synopsis
16618 -environment-path [ -r ] [ @var{pathdir} ]+
16621 Add directories @var{pathdir} to beginning of search path for object files.
16622 If the @samp{-r} option is used, the search path is reset to the original
16623 search path that existed at gdb start-up. If directories @var{pathdir} are
16624 supplied in addition to the
16625 @samp{-r} option, the search path is first reset and then addition
16627 Multiple directories may be specified, separated by blanks. Specifying
16628 multiple directories in a single command
16629 results in the directories added to the beginning of the
16630 search path in the same order they were presented in the command.
16631 If blanks are needed as
16632 part of a directory name, double-quotes should be used around
16633 the name. In the command output, the path will show up separated
16634 by the system directory-separator character. The directory-seperator
16635 character must not be used
16636 in any directory name.
16637 If no directories are specified, the current path is displayed.
16640 @subsubheading @value{GDBN} Command
16642 The corresponding @value{GDBN} command is @samp{path}.
16644 @subsubheading Example
16649 ^done,path="/usr/bin"
16651 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
16652 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
16654 -environment-path -r /usr/local/bin
16655 ^done,path="/usr/local/bin:/usr/bin"
16660 @subheading The @code{-environment-pwd} Command
16661 @findex -environment-pwd
16663 @subsubheading Synopsis
16669 Show the current working directory.
16671 @subsubheading @value{GDBN} command
16673 The corresponding @value{GDBN} command is @samp{pwd}.
16675 @subsubheading Example
16680 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
16684 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16685 @node GDB/MI Program Control
16686 @section @sc{gdb/mi} Program control
16688 @subsubheading Program termination
16690 As a result of execution, the inferior program can run to completion, if
16691 it doesn't encounter any breakpoints. In this case the output will
16692 include an exit code, if the program has exited exceptionally.
16694 @subsubheading Examples
16697 Program exited normally:
16705 *stopped,reason="exited-normally"
16710 Program exited exceptionally:
16718 *stopped,reason="exited",exit-code="01"
16722 Another way the program can terminate is if it receives a signal such as
16723 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
16727 *stopped,reason="exited-signalled",signal-name="SIGINT",
16728 signal-meaning="Interrupt"
16732 @subheading The @code{-exec-abort} Command
16733 @findex -exec-abort
16735 @subsubheading Synopsis
16741 Kill the inferior running program.
16743 @subsubheading @value{GDBN} Command
16745 The corresponding @value{GDBN} command is @samp{kill}.
16747 @subsubheading Example
16751 @subheading The @code{-exec-arguments} Command
16752 @findex -exec-arguments
16754 @subsubheading Synopsis
16757 -exec-arguments @var{args}
16760 Set the inferior program arguments, to be used in the next
16763 @subsubheading @value{GDBN} Command
16765 The corresponding @value{GDBN} command is @samp{set args}.
16767 @subsubheading Example
16770 Don't have one around.
16773 @subheading The @code{-exec-continue} Command
16774 @findex -exec-continue
16776 @subsubheading Synopsis
16782 Asynchronous command. Resumes the execution of the inferior program
16783 until a breakpoint is encountered, or until the inferior exits.
16785 @subsubheading @value{GDBN} Command
16787 The corresponding @value{GDBN} corresponding is @samp{continue}.
16789 @subsubheading Example
16796 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
16797 file="hello.c",line="13"@}
16802 @subheading The @code{-exec-finish} Command
16803 @findex -exec-finish
16805 @subsubheading Synopsis
16811 Asynchronous command. Resumes the execution of the inferior program
16812 until the current function is exited. Displays the results returned by
16815 @subsubheading @value{GDBN} Command
16817 The corresponding @value{GDBN} command is @samp{finish}.
16819 @subsubheading Example
16821 Function returning @code{void}.
16828 *stopped,reason="function-finished",frame=@{func="main",args=[],
16829 file="hello.c",line="7"@}
16833 Function returning other than @code{void}. The name of the internal
16834 @value{GDBN} variable storing the result is printed, together with the
16841 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
16842 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
16843 file="recursive2.c",line="14"@},
16844 gdb-result-var="$1",return-value="0"
16849 @subheading The @code{-exec-interrupt} Command
16850 @findex -exec-interrupt
16852 @subsubheading Synopsis
16858 Asynchronous command. Interrupts the background execution of the target.
16859 Note how the token associated with the stop message is the one for the
16860 execution command that has been interrupted. The token for the interrupt
16861 itself only appears in the @samp{^done} output. If the user is trying to
16862 interrupt a non-running program, an error message will be printed.
16864 @subsubheading @value{GDBN} Command
16866 The corresponding @value{GDBN} command is @samp{interrupt}.
16868 @subsubheading Example
16879 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
16880 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",line="13"@}
16885 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
16890 @subheading The @code{-exec-next} Command
16893 @subsubheading Synopsis
16899 Asynchronous command. Resumes execution of the inferior program, stopping
16900 when the beginning of the next source line is reached.
16902 @subsubheading @value{GDBN} Command
16904 The corresponding @value{GDBN} command is @samp{next}.
16906 @subsubheading Example
16912 *stopped,reason="end-stepping-range",line="8",file="hello.c"
16917 @subheading The @code{-exec-next-instruction} Command
16918 @findex -exec-next-instruction
16920 @subsubheading Synopsis
16923 -exec-next-instruction
16926 Asynchronous command. Executes one machine instruction. If the
16927 instruction is a function call continues until the function returns. If
16928 the program stops at an instruction in the middle of a source line, the
16929 address will be printed as well.
16931 @subsubheading @value{GDBN} Command
16933 The corresponding @value{GDBN} command is @samp{nexti}.
16935 @subsubheading Example
16939 -exec-next-instruction
16943 *stopped,reason="end-stepping-range",
16944 addr="0x000100d4",line="5",file="hello.c"
16949 @subheading The @code{-exec-return} Command
16950 @findex -exec-return
16952 @subsubheading Synopsis
16958 Makes current function return immediately. Doesn't execute the inferior.
16959 Displays the new current frame.
16961 @subsubheading @value{GDBN} Command
16963 The corresponding @value{GDBN} command is @samp{return}.
16965 @subsubheading Example
16969 200-break-insert callee4
16970 200^done,bkpt=@{number="1",addr="0x00010734",
16971 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
16976 000*stopped,reason="breakpoint-hit",bkptno="1",
16977 frame=@{func="callee4",args=[],
16978 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
16984 111^done,frame=@{level="0",func="callee3",
16985 args=[@{name="strarg",
16986 value="0x11940 \"A string argument.\""@}],
16987 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
16992 @subheading The @code{-exec-run} Command
16995 @subsubheading Synopsis
17001 Asynchronous command. Starts execution of the inferior from the
17002 beginning. The inferior executes until either a breakpoint is
17003 encountered or the program exits.
17005 @subsubheading @value{GDBN} Command
17007 The corresponding @value{GDBN} command is @samp{run}.
17009 @subsubheading Example
17014 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
17019 *stopped,reason="breakpoint-hit",bkptno="1",
17020 frame=@{func="main",args=[],file="recursive2.c",line="4"@}
17025 @subheading The @code{-exec-show-arguments} Command
17026 @findex -exec-show-arguments
17028 @subsubheading Synopsis
17031 -exec-show-arguments
17034 Print the arguments of the program.
17036 @subsubheading @value{GDBN} Command
17038 The corresponding @value{GDBN} command is @samp{show args}.
17040 @subsubheading Example
17043 @c @subheading -exec-signal
17045 @subheading The @code{-exec-step} Command
17048 @subsubheading Synopsis
17054 Asynchronous command. Resumes execution of the inferior program, stopping
17055 when the beginning of the next source line is reached, if the next
17056 source line is not a function call. If it is, stop at the first
17057 instruction of the called function.
17059 @subsubheading @value{GDBN} Command
17061 The corresponding @value{GDBN} command is @samp{step}.
17063 @subsubheading Example
17065 Stepping into a function:
17071 *stopped,reason="end-stepping-range",
17072 frame=@{func="foo",args=[@{name="a",value="10"@},
17073 @{name="b",value="0"@}],file="recursive2.c",line="11"@}
17083 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
17088 @subheading The @code{-exec-step-instruction} Command
17089 @findex -exec-step-instruction
17091 @subsubheading Synopsis
17094 -exec-step-instruction
17097 Asynchronous command. Resumes the inferior which executes one machine
17098 instruction. The output, once @value{GDBN} has stopped, will vary depending on
17099 whether we have stopped in the middle of a source line or not. In the
17100 former case, the address at which the program stopped will be printed as
17103 @subsubheading @value{GDBN} Command
17105 The corresponding @value{GDBN} command is @samp{stepi}.
17107 @subsubheading Example
17111 -exec-step-instruction
17115 *stopped,reason="end-stepping-range",
17116 frame=@{func="foo",args=[],file="try.c",line="10"@}
17118 -exec-step-instruction
17122 *stopped,reason="end-stepping-range",
17123 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",line="10"@}
17128 @subheading The @code{-exec-until} Command
17129 @findex -exec-until
17131 @subsubheading Synopsis
17134 -exec-until [ @var{location} ]
17137 Asynchronous command. Executes the inferior until the @var{location}
17138 specified in the argument is reached. If there is no argument, the inferior
17139 executes until a source line greater than the current one is reached.
17140 The reason for stopping in this case will be @samp{location-reached}.
17142 @subsubheading @value{GDBN} Command
17144 The corresponding @value{GDBN} command is @samp{until}.
17146 @subsubheading Example
17150 -exec-until recursive2.c:6
17154 *stopped,reason="location-reached",frame=@{func="main",args=[],
17155 file="recursive2.c",line="6"@}
17160 @subheading -file-clear
17161 Is this going away????
17165 @subheading The @code{-file-exec-and-symbols} Command
17166 @findex -file-exec-and-symbols
17168 @subsubheading Synopsis
17171 -file-exec-and-symbols @var{file}
17174 Specify the executable file to be debugged. This file is the one from
17175 which the symbol table is also read. If no file is specified, the
17176 command clears the executable and symbol information. If breakpoints
17177 are set when using this command with no arguments, @value{GDBN} will produce
17178 error messages. Otherwise, no output is produced, except a completion
17181 @subsubheading @value{GDBN} Command
17183 The corresponding @value{GDBN} command is @samp{file}.
17185 @subsubheading Example
17189 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
17195 @subheading The @code{-file-exec-file} Command
17196 @findex -file-exec-file
17198 @subsubheading Synopsis
17201 -file-exec-file @var{file}
17204 Specify the executable file to be debugged. Unlike
17205 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
17206 from this file. If used without argument, @value{GDBN} clears the information
17207 about the executable file. No output is produced, except a completion
17210 @subsubheading @value{GDBN} Command
17212 The corresponding @value{GDBN} command is @samp{exec-file}.
17214 @subsubheading Example
17218 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
17224 @subheading The @code{-file-list-exec-sections} Command
17225 @findex -file-list-exec-sections
17227 @subsubheading Synopsis
17230 -file-list-exec-sections
17233 List the sections of the current executable file.
17235 @subsubheading @value{GDBN} Command
17237 The @value{GDBN} command @samp{info file} shows, among the rest, the same
17238 information as this command. @code{gdbtk} has a corresponding command
17239 @samp{gdb_load_info}.
17241 @subsubheading Example
17245 @subheading The @code{-file-list-exec-source-file} Command
17246 @findex -file-list-exec-source-file
17248 @subsubheading Synopsis
17251 -file-list-exec-source-file
17254 List the line number, the current source file, and the absolute path
17255 to the current source file for the current executable.
17257 @subsubheading @value{GDBN} Command
17259 There's no @value{GDBN} command which directly corresponds to this one.
17261 @subsubheading Example
17265 123-file-list-exec-source-file
17266 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
17271 @subheading The @code{-file-list-exec-source-files} Command
17272 @findex -file-list-exec-source-files
17274 @subsubheading Synopsis
17277 -file-list-exec-source-files
17280 List the source files for the current executable.
17282 It will always output the filename, but only when GDB can find the absolute
17283 file name of a source file, will it output the fullname.
17285 @subsubheading @value{GDBN} Command
17287 There's no @value{GDBN} command which directly corresponds to this one.
17288 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
17290 @subsubheading Example
17293 -file-list-exec-source-files
17295 @{file=foo.c,fullname=/home/foo.c@},
17296 @{file=/home/bar.c,fullname=/home/bar.c@},
17297 @{file=gdb_could_not_find_fullpath.c@}]
17301 @subheading The @code{-file-list-shared-libraries} Command
17302 @findex -file-list-shared-libraries
17304 @subsubheading Synopsis
17307 -file-list-shared-libraries
17310 List the shared libraries in the program.
17312 @subsubheading @value{GDBN} Command
17314 The corresponding @value{GDBN} command is @samp{info shared}.
17316 @subsubheading Example
17320 @subheading The @code{-file-list-symbol-files} Command
17321 @findex -file-list-symbol-files
17323 @subsubheading Synopsis
17326 -file-list-symbol-files
17331 @subsubheading @value{GDBN} Command
17333 The corresponding @value{GDBN} command is @samp{info file} (part of it).
17335 @subsubheading Example
17339 @subheading The @code{-file-symbol-file} Command
17340 @findex -file-symbol-file
17342 @subsubheading Synopsis
17345 -file-symbol-file @var{file}
17348 Read symbol table info from the specified @var{file} argument. When
17349 used without arguments, clears @value{GDBN}'s symbol table info. No output is
17350 produced, except for a completion notification.
17352 @subsubheading @value{GDBN} Command
17354 The corresponding @value{GDBN} command is @samp{symbol-file}.
17356 @subsubheading Example
17360 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
17365 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17366 @node GDB/MI Miscellaneous Commands
17367 @section Miscellaneous @value{GDBN} commands in @sc{gdb/mi}
17369 @c @subheading -gdb-complete
17371 @subheading The @code{-gdb-exit} Command
17374 @subsubheading Synopsis
17380 Exit @value{GDBN} immediately.
17382 @subsubheading @value{GDBN} Command
17384 Approximately corresponds to @samp{quit}.
17386 @subsubheading Example
17393 @subheading The @code{-gdb-set} Command
17396 @subsubheading Synopsis
17402 Set an internal @value{GDBN} variable.
17403 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
17405 @subsubheading @value{GDBN} Command
17407 The corresponding @value{GDBN} command is @samp{set}.
17409 @subsubheading Example
17419 @subheading The @code{-gdb-show} Command
17422 @subsubheading Synopsis
17428 Show the current value of a @value{GDBN} variable.
17430 @subsubheading @value{GDBN} command
17432 The corresponding @value{GDBN} command is @samp{show}.
17434 @subsubheading Example
17443 @c @subheading -gdb-source
17446 @subheading The @code{-gdb-version} Command
17447 @findex -gdb-version
17449 @subsubheading Synopsis
17455 Show version information for @value{GDBN}. Used mostly in testing.
17457 @subsubheading @value{GDBN} Command
17459 There's no equivalent @value{GDBN} command. @value{GDBN} by default shows this
17460 information when you start an interactive session.
17462 @subsubheading Example
17464 @c This example modifies the actual output from GDB to avoid overfull
17470 ~Copyright 2000 Free Software Foundation, Inc.
17471 ~GDB is free software, covered by the GNU General Public License, and
17472 ~you are welcome to change it and/or distribute copies of it under
17473 ~ certain conditions.
17474 ~Type "show copying" to see the conditions.
17475 ~There is absolutely no warranty for GDB. Type "show warranty" for
17477 ~This GDB was configured as
17478 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
17483 @subheading The @code{-interpreter-exec} Command
17484 @findex -interpreter-exec
17486 @subheading Synopsis
17489 -interpreter-exec @var{interpreter} @var{command}
17492 Execute the specified @var{command} in the given @var{interpreter}.
17494 @subheading @value{GDBN} Command
17496 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
17498 @subheading Example
17502 -interpreter-exec console "break main"
17503 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
17504 &"During symbol reading, bad structure-type format.\n"
17505 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
17511 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17512 @node GDB/MI Kod Commands
17513 @section @sc{gdb/mi} Kod Commands
17515 The Kod commands are not implemented.
17517 @c @subheading -kod-info
17519 @c @subheading -kod-list
17521 @c @subheading -kod-list-object-types
17523 @c @subheading -kod-show
17525 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17526 @node GDB/MI Memory Overlay Commands
17527 @section @sc{gdb/mi} Memory Overlay Commands
17529 The memory overlay commands are not implemented.
17531 @c @subheading -overlay-auto
17533 @c @subheading -overlay-list-mapping-state
17535 @c @subheading -overlay-list-overlays
17537 @c @subheading -overlay-map
17539 @c @subheading -overlay-off
17541 @c @subheading -overlay-on
17543 @c @subheading -overlay-unmap
17545 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17546 @node GDB/MI Signal Handling Commands
17547 @section @sc{gdb/mi} Signal Handling Commands
17549 Signal handling commands are not implemented.
17551 @c @subheading -signal-handle
17553 @c @subheading -signal-list-handle-actions
17555 @c @subheading -signal-list-signal-types
17559 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17560 @node GDB/MI Stack Manipulation
17561 @section @sc{gdb/mi} Stack Manipulation Commands
17564 @subheading The @code{-stack-info-frame} Command
17565 @findex -stack-info-frame
17567 @subsubheading Synopsis
17573 Get info on the current frame.
17575 @subsubheading @value{GDBN} Command
17577 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
17578 (without arguments).
17580 @subsubheading Example
17583 @subheading The @code{-stack-info-depth} Command
17584 @findex -stack-info-depth
17586 @subsubheading Synopsis
17589 -stack-info-depth [ @var{max-depth} ]
17592 Return the depth of the stack. If the integer argument @var{max-depth}
17593 is specified, do not count beyond @var{max-depth} frames.
17595 @subsubheading @value{GDBN} Command
17597 There's no equivalent @value{GDBN} command.
17599 @subsubheading Example
17601 For a stack with frame levels 0 through 11:
17608 -stack-info-depth 4
17611 -stack-info-depth 12
17614 -stack-info-depth 11
17617 -stack-info-depth 13
17622 @subheading The @code{-stack-list-arguments} Command
17623 @findex -stack-list-arguments
17625 @subsubheading Synopsis
17628 -stack-list-arguments @var{show-values}
17629 [ @var{low-frame} @var{high-frame} ]
17632 Display a list of the arguments for the frames between @var{low-frame}
17633 and @var{high-frame} (inclusive). If @var{low-frame} and
17634 @var{high-frame} are not provided, list the arguments for the whole call
17637 The @var{show-values} argument must have a value of 0 or 1. A value of
17638 0 means that only the names of the arguments are listed, a value of 1
17639 means that both names and values of the arguments are printed.
17641 @subsubheading @value{GDBN} Command
17643 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
17644 @samp{gdb_get_args} command which partially overlaps with the
17645 functionality of @samp{-stack-list-arguments}.
17647 @subsubheading Example
17654 frame=@{level="0",addr="0x00010734",func="callee4",
17655 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
17656 frame=@{level="1",addr="0x0001076c",func="callee3",
17657 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
17658 frame=@{level="2",addr="0x0001078c",func="callee2",
17659 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
17660 frame=@{level="3",addr="0x000107b4",func="callee1",
17661 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
17662 frame=@{level="4",addr="0x000107e0",func="main",
17663 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
17665 -stack-list-arguments 0
17668 frame=@{level="0",args=[]@},
17669 frame=@{level="1",args=[name="strarg"]@},
17670 frame=@{level="2",args=[name="intarg",name="strarg"]@},
17671 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
17672 frame=@{level="4",args=[]@}]
17674 -stack-list-arguments 1
17677 frame=@{level="0",args=[]@},
17679 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
17680 frame=@{level="2",args=[
17681 @{name="intarg",value="2"@},
17682 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
17683 @{frame=@{level="3",args=[
17684 @{name="intarg",value="2"@},
17685 @{name="strarg",value="0x11940 \"A string argument.\""@},
17686 @{name="fltarg",value="3.5"@}]@},
17687 frame=@{level="4",args=[]@}]
17689 -stack-list-arguments 0 2 2
17690 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
17692 -stack-list-arguments 1 2 2
17693 ^done,stack-args=[frame=@{level="2",
17694 args=[@{name="intarg",value="2"@},
17695 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
17699 @c @subheading -stack-list-exception-handlers
17702 @subheading The @code{-stack-list-frames} Command
17703 @findex -stack-list-frames
17705 @subsubheading Synopsis
17708 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
17711 List the frames currently on the stack. For each frame it displays the
17716 The frame number, 0 being the topmost frame, i.e. the innermost function.
17718 The @code{$pc} value for that frame.
17722 File name of the source file where the function lives.
17724 Line number corresponding to the @code{$pc}.
17727 If invoked without arguments, this command prints a backtrace for the
17728 whole stack. If given two integer arguments, it shows the frames whose
17729 levels are between the two arguments (inclusive). If the two arguments
17730 are equal, it shows the single frame at the corresponding level.
17732 @subsubheading @value{GDBN} Command
17734 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
17736 @subsubheading Example
17738 Full stack backtrace:
17744 [frame=@{level="0",addr="0x0001076c",func="foo",
17745 file="recursive2.c",line="11"@},
17746 frame=@{level="1",addr="0x000107a4",func="foo",
17747 file="recursive2.c",line="14"@},
17748 frame=@{level="2",addr="0x000107a4",func="foo",
17749 file="recursive2.c",line="14"@},
17750 frame=@{level="3",addr="0x000107a4",func="foo",
17751 file="recursive2.c",line="14"@},
17752 frame=@{level="4",addr="0x000107a4",func="foo",
17753 file="recursive2.c",line="14"@},
17754 frame=@{level="5",addr="0x000107a4",func="foo",
17755 file="recursive2.c",line="14"@},
17756 frame=@{level="6",addr="0x000107a4",func="foo",
17757 file="recursive2.c",line="14"@},
17758 frame=@{level="7",addr="0x000107a4",func="foo",
17759 file="recursive2.c",line="14"@},
17760 frame=@{level="8",addr="0x000107a4",func="foo",
17761 file="recursive2.c",line="14"@},
17762 frame=@{level="9",addr="0x000107a4",func="foo",
17763 file="recursive2.c",line="14"@},
17764 frame=@{level="10",addr="0x000107a4",func="foo",
17765 file="recursive2.c",line="14"@},
17766 frame=@{level="11",addr="0x00010738",func="main",
17767 file="recursive2.c",line="4"@}]
17771 Show frames between @var{low_frame} and @var{high_frame}:
17775 -stack-list-frames 3 5
17777 [frame=@{level="3",addr="0x000107a4",func="foo",
17778 file="recursive2.c",line="14"@},
17779 frame=@{level="4",addr="0x000107a4",func="foo",
17780 file="recursive2.c",line="14"@},
17781 frame=@{level="5",addr="0x000107a4",func="foo",
17782 file="recursive2.c",line="14"@}]
17786 Show a single frame:
17790 -stack-list-frames 3 3
17792 [frame=@{level="3",addr="0x000107a4",func="foo",
17793 file="recursive2.c",line="14"@}]
17798 @subheading The @code{-stack-list-locals} Command
17799 @findex -stack-list-locals
17801 @subsubheading Synopsis
17804 -stack-list-locals @var{print-values}
17807 Display the local variable names for the current frame. With an
17808 argument of 0 or @code{--no-values}, prints only the names of the variables.
17809 With argument of 1 or @code{--all-values}, prints also their values. With
17810 argument of 2 or @code{--simple-values}, prints the name, type and value for
17811 simple data types and the name and type for arrays, structures and
17812 unions. In this last case, the idea is that the user can see the
17813 value of simple data types immediately and he can create variable
17814 objects for other data types if he wishes to explore their values in
17817 @subsubheading @value{GDBN} Command
17819 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
17821 @subsubheading Example
17825 -stack-list-locals 0
17826 ^done,locals=[name="A",name="B",name="C"]
17828 -stack-list-locals --all-values
17829 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
17830 @{name="C",value="@{1, 2, 3@}"@}]
17831 -stack-list-locals --simple-values
17832 ^done,locals=[@{name="A",type="int",value="1"@},
17833 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
17838 @subheading The @code{-stack-select-frame} Command
17839 @findex -stack-select-frame
17841 @subsubheading Synopsis
17844 -stack-select-frame @var{framenum}
17847 Change the current frame. Select a different frame @var{framenum} on
17850 @subsubheading @value{GDBN} Command
17852 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
17853 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
17855 @subsubheading Example
17859 -stack-select-frame 2
17864 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17865 @node GDB/MI Symbol Query
17866 @section @sc{gdb/mi} Symbol Query Commands
17869 @subheading The @code{-symbol-info-address} Command
17870 @findex -symbol-info-address
17872 @subsubheading Synopsis
17875 -symbol-info-address @var{symbol}
17878 Describe where @var{symbol} is stored.
17880 @subsubheading @value{GDBN} Command
17882 The corresponding @value{GDBN} command is @samp{info address}.
17884 @subsubheading Example
17888 @subheading The @code{-symbol-info-file} Command
17889 @findex -symbol-info-file
17891 @subsubheading Synopsis
17897 Show the file for the symbol.
17899 @subsubheading @value{GDBN} Command
17901 There's no equivalent @value{GDBN} command. @code{gdbtk} has
17902 @samp{gdb_find_file}.
17904 @subsubheading Example
17908 @subheading The @code{-symbol-info-function} Command
17909 @findex -symbol-info-function
17911 @subsubheading Synopsis
17914 -symbol-info-function
17917 Show which function the symbol lives in.
17919 @subsubheading @value{GDBN} Command
17921 @samp{gdb_get_function} in @code{gdbtk}.
17923 @subsubheading Example
17927 @subheading The @code{-symbol-info-line} Command
17928 @findex -symbol-info-line
17930 @subsubheading Synopsis
17936 Show the core addresses of the code for a source line.
17938 @subsubheading @value{GDBN} Command
17940 The corresponding @value{GDBN} command is @samp{info line}.
17941 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
17943 @subsubheading Example
17947 @subheading The @code{-symbol-info-symbol} Command
17948 @findex -symbol-info-symbol
17950 @subsubheading Synopsis
17953 -symbol-info-symbol @var{addr}
17956 Describe what symbol is at location @var{addr}.
17958 @subsubheading @value{GDBN} Command
17960 The corresponding @value{GDBN} command is @samp{info symbol}.
17962 @subsubheading Example
17966 @subheading The @code{-symbol-list-functions} Command
17967 @findex -symbol-list-functions
17969 @subsubheading Synopsis
17972 -symbol-list-functions
17975 List the functions in the executable.
17977 @subsubheading @value{GDBN} Command
17979 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
17980 @samp{gdb_search} in @code{gdbtk}.
17982 @subsubheading Example
17986 @subheading The @code{-symbol-list-lines} Command
17987 @findex -symbol-list-lines
17989 @subsubheading Synopsis
17992 -symbol-list-lines @var{filename}
17995 Print the list of lines that contain code and their associated program
17996 addresses for the given source filename. The entries are sorted in
17997 ascending PC order.
17999 @subsubheading @value{GDBN} Command
18001 There is no corresponding @value{GDBN} command.
18003 @subsubheading Example
18006 -symbol-list-lines basics.c
18007 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
18012 @subheading The @code{-symbol-list-types} Command
18013 @findex -symbol-list-types
18015 @subsubheading Synopsis
18021 List all the type names.
18023 @subsubheading @value{GDBN} Command
18025 The corresponding commands are @samp{info types} in @value{GDBN},
18026 @samp{gdb_search} in @code{gdbtk}.
18028 @subsubheading Example
18032 @subheading The @code{-symbol-list-variables} Command
18033 @findex -symbol-list-variables
18035 @subsubheading Synopsis
18038 -symbol-list-variables
18041 List all the global and static variable names.
18043 @subsubheading @value{GDBN} Command
18045 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
18047 @subsubheading Example
18051 @subheading The @code{-symbol-locate} Command
18052 @findex -symbol-locate
18054 @subsubheading Synopsis
18060 @subsubheading @value{GDBN} Command
18062 @samp{gdb_loc} in @code{gdbtk}.
18064 @subsubheading Example
18068 @subheading The @code{-symbol-type} Command
18069 @findex -symbol-type
18071 @subsubheading Synopsis
18074 -symbol-type @var{variable}
18077 Show type of @var{variable}.
18079 @subsubheading @value{GDBN} Command
18081 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
18082 @samp{gdb_obj_variable}.
18084 @subsubheading Example
18088 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18089 @node GDB/MI Target Manipulation
18090 @section @sc{gdb/mi} Target Manipulation Commands
18093 @subheading The @code{-target-attach} Command
18094 @findex -target-attach
18096 @subsubheading Synopsis
18099 -target-attach @var{pid} | @var{file}
18102 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
18104 @subsubheading @value{GDBN} command
18106 The corresponding @value{GDBN} command is @samp{attach}.
18108 @subsubheading Example
18112 @subheading The @code{-target-compare-sections} Command
18113 @findex -target-compare-sections
18115 @subsubheading Synopsis
18118 -target-compare-sections [ @var{section} ]
18121 Compare data of section @var{section} on target to the exec file.
18122 Without the argument, all sections are compared.
18124 @subsubheading @value{GDBN} Command
18126 The @value{GDBN} equivalent is @samp{compare-sections}.
18128 @subsubheading Example
18132 @subheading The @code{-target-detach} Command
18133 @findex -target-detach
18135 @subsubheading Synopsis
18141 Disconnect from the remote target. There's no output.
18143 @subsubheading @value{GDBN} command
18145 The corresponding @value{GDBN} command is @samp{detach}.
18147 @subsubheading Example
18157 @subheading The @code{-target-disconnect} Command
18158 @findex -target-disconnect
18160 @subsubheading Synopsis
18166 Disconnect from the remote target. There's no output.
18168 @subsubheading @value{GDBN} command
18170 The corresponding @value{GDBN} command is @samp{disconnect}.
18172 @subsubheading Example
18182 @subheading The @code{-target-download} Command
18183 @findex -target-download
18185 @subsubheading Synopsis
18191 Loads the executable onto the remote target.
18192 It prints out an update message every half second, which includes the fields:
18196 The name of the section.
18198 The size of what has been sent so far for that section.
18200 The size of the section.
18202 The total size of what was sent so far (the current and the previous sections).
18204 The size of the overall executable to download.
18208 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
18209 @sc{gdb/mi} Output Syntax}).
18211 In addition, it prints the name and size of the sections, as they are
18212 downloaded. These messages include the following fields:
18216 The name of the section.
18218 The size of the section.
18220 The size of the overall executable to download.
18224 At the end, a summary is printed.
18226 @subsubheading @value{GDBN} Command
18228 The corresponding @value{GDBN} command is @samp{load}.
18230 @subsubheading Example
18232 Note: each status message appears on a single line. Here the messages
18233 have been broken down so that they can fit onto a page.
18238 +download,@{section=".text",section-size="6668",total-size="9880"@}
18239 +download,@{section=".text",section-sent="512",section-size="6668",
18240 total-sent="512",total-size="9880"@}
18241 +download,@{section=".text",section-sent="1024",section-size="6668",
18242 total-sent="1024",total-size="9880"@}
18243 +download,@{section=".text",section-sent="1536",section-size="6668",
18244 total-sent="1536",total-size="9880"@}
18245 +download,@{section=".text",section-sent="2048",section-size="6668",
18246 total-sent="2048",total-size="9880"@}
18247 +download,@{section=".text",section-sent="2560",section-size="6668",
18248 total-sent="2560",total-size="9880"@}
18249 +download,@{section=".text",section-sent="3072",section-size="6668",
18250 total-sent="3072",total-size="9880"@}
18251 +download,@{section=".text",section-sent="3584",section-size="6668",
18252 total-sent="3584",total-size="9880"@}
18253 +download,@{section=".text",section-sent="4096",section-size="6668",
18254 total-sent="4096",total-size="9880"@}
18255 +download,@{section=".text",section-sent="4608",section-size="6668",
18256 total-sent="4608",total-size="9880"@}
18257 +download,@{section=".text",section-sent="5120",section-size="6668",
18258 total-sent="5120",total-size="9880"@}
18259 +download,@{section=".text",section-sent="5632",section-size="6668",
18260 total-sent="5632",total-size="9880"@}
18261 +download,@{section=".text",section-sent="6144",section-size="6668",
18262 total-sent="6144",total-size="9880"@}
18263 +download,@{section=".text",section-sent="6656",section-size="6668",
18264 total-sent="6656",total-size="9880"@}
18265 +download,@{section=".init",section-size="28",total-size="9880"@}
18266 +download,@{section=".fini",section-size="28",total-size="9880"@}
18267 +download,@{section=".data",section-size="3156",total-size="9880"@}
18268 +download,@{section=".data",section-sent="512",section-size="3156",
18269 total-sent="7236",total-size="9880"@}
18270 +download,@{section=".data",section-sent="1024",section-size="3156",
18271 total-sent="7748",total-size="9880"@}
18272 +download,@{section=".data",section-sent="1536",section-size="3156",
18273 total-sent="8260",total-size="9880"@}
18274 +download,@{section=".data",section-sent="2048",section-size="3156",
18275 total-sent="8772",total-size="9880"@}
18276 +download,@{section=".data",section-sent="2560",section-size="3156",
18277 total-sent="9284",total-size="9880"@}
18278 +download,@{section=".data",section-sent="3072",section-size="3156",
18279 total-sent="9796",total-size="9880"@}
18280 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
18286 @subheading The @code{-target-exec-status} Command
18287 @findex -target-exec-status
18289 @subsubheading Synopsis
18292 -target-exec-status
18295 Provide information on the state of the target (whether it is running or
18296 not, for instance).
18298 @subsubheading @value{GDBN} Command
18300 There's no equivalent @value{GDBN} command.
18302 @subsubheading Example
18306 @subheading The @code{-target-list-available-targets} Command
18307 @findex -target-list-available-targets
18309 @subsubheading Synopsis
18312 -target-list-available-targets
18315 List the possible targets to connect to.
18317 @subsubheading @value{GDBN} Command
18319 The corresponding @value{GDBN} command is @samp{help target}.
18321 @subsubheading Example
18325 @subheading The @code{-target-list-current-targets} Command
18326 @findex -target-list-current-targets
18328 @subsubheading Synopsis
18331 -target-list-current-targets
18334 Describe the current target.
18336 @subsubheading @value{GDBN} Command
18338 The corresponding information is printed by @samp{info file} (among
18341 @subsubheading Example
18345 @subheading The @code{-target-list-parameters} Command
18346 @findex -target-list-parameters
18348 @subsubheading Synopsis
18351 -target-list-parameters
18356 @subsubheading @value{GDBN} Command
18360 @subsubheading Example
18364 @subheading The @code{-target-select} Command
18365 @findex -target-select
18367 @subsubheading Synopsis
18370 -target-select @var{type} @var{parameters @dots{}}
18373 Connect @value{GDBN} to the remote target. This command takes two args:
18377 The type of target, for instance @samp{async}, @samp{remote}, etc.
18378 @item @var{parameters}
18379 Device names, host names and the like. @xref{Target Commands, ,
18380 Commands for managing targets}, for more details.
18383 The output is a connection notification, followed by the address at
18384 which the target program is, in the following form:
18387 ^connected,addr="@var{address}",func="@var{function name}",
18388 args=[@var{arg list}]
18391 @subsubheading @value{GDBN} Command
18393 The corresponding @value{GDBN} command is @samp{target}.
18395 @subsubheading Example
18399 -target-select async /dev/ttya
18400 ^connected,addr="0xfe00a300",func="??",args=[]
18404 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18405 @node GDB/MI Thread Commands
18406 @section @sc{gdb/mi} Thread Commands
18409 @subheading The @code{-thread-info} Command
18410 @findex -thread-info
18412 @subsubheading Synopsis
18418 @subsubheading @value{GDBN} command
18422 @subsubheading Example
18426 @subheading The @code{-thread-list-all-threads} Command
18427 @findex -thread-list-all-threads
18429 @subsubheading Synopsis
18432 -thread-list-all-threads
18435 @subsubheading @value{GDBN} Command
18437 The equivalent @value{GDBN} command is @samp{info threads}.
18439 @subsubheading Example
18443 @subheading The @code{-thread-list-ids} Command
18444 @findex -thread-list-ids
18446 @subsubheading Synopsis
18452 Produces a list of the currently known @value{GDBN} thread ids. At the
18453 end of the list it also prints the total number of such threads.
18455 @subsubheading @value{GDBN} Command
18457 Part of @samp{info threads} supplies the same information.
18459 @subsubheading Example
18461 No threads present, besides the main process:
18466 ^done,thread-ids=@{@},number-of-threads="0"
18476 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18477 number-of-threads="3"
18482 @subheading The @code{-thread-select} Command
18483 @findex -thread-select
18485 @subsubheading Synopsis
18488 -thread-select @var{threadnum}
18491 Make @var{threadnum} the current thread. It prints the number of the new
18492 current thread, and the topmost frame for that thread.
18494 @subsubheading @value{GDBN} Command
18496 The corresponding @value{GDBN} command is @samp{thread}.
18498 @subsubheading Example
18505 *stopped,reason="end-stepping-range",thread-id="2",line="187",
18506 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
18510 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18511 number-of-threads="3"
18514 ^done,new-thread-id="3",
18515 frame=@{level="0",func="vprintf",
18516 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
18517 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
18521 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18522 @node GDB/MI Tracepoint Commands
18523 @section @sc{gdb/mi} Tracepoint Commands
18525 The tracepoint commands are not yet implemented.
18527 @c @subheading -trace-actions
18529 @c @subheading -trace-delete
18531 @c @subheading -trace-disable
18533 @c @subheading -trace-dump
18535 @c @subheading -trace-enable
18537 @c @subheading -trace-exists
18539 @c @subheading -trace-find
18541 @c @subheading -trace-frame-number
18543 @c @subheading -trace-info
18545 @c @subheading -trace-insert
18547 @c @subheading -trace-list
18549 @c @subheading -trace-pass-count
18551 @c @subheading -trace-save
18553 @c @subheading -trace-start
18555 @c @subheading -trace-stop
18558 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18559 @node GDB/MI Variable Objects
18560 @section @sc{gdb/mi} Variable Objects
18563 @subheading Motivation for Variable Objects in @sc{gdb/mi}
18565 For the implementation of a variable debugger window (locals, watched
18566 expressions, etc.), we are proposing the adaptation of the existing code
18567 used by @code{Insight}.
18569 The two main reasons for that are:
18573 It has been proven in practice (it is already on its second generation).
18576 It will shorten development time (needless to say how important it is
18580 The original interface was designed to be used by Tcl code, so it was
18581 slightly changed so it could be used through @sc{gdb/mi}. This section
18582 describes the @sc{gdb/mi} operations that will be available and gives some
18583 hints about their use.
18585 @emph{Note}: In addition to the set of operations described here, we
18586 expect the @sc{gui} implementation of a variable window to require, at
18587 least, the following operations:
18590 @item @code{-gdb-show} @code{output-radix}
18591 @item @code{-stack-list-arguments}
18592 @item @code{-stack-list-locals}
18593 @item @code{-stack-select-frame}
18596 @subheading Introduction to Variable Objects in @sc{gdb/mi}
18598 @cindex variable objects in @sc{gdb/mi}
18599 The basic idea behind variable objects is the creation of a named object
18600 to represent a variable, an expression, a memory location or even a CPU
18601 register. For each object created, a set of operations is available for
18602 examining or changing its properties.
18604 Furthermore, complex data types, such as C structures, are represented
18605 in a tree format. For instance, the @code{struct} type variable is the
18606 root and the children will represent the struct members. If a child
18607 is itself of a complex type, it will also have children of its own.
18608 Appropriate language differences are handled for C, C@t{++} and Java.
18610 When returning the actual values of the objects, this facility allows
18611 for the individual selection of the display format used in the result
18612 creation. It can be chosen among: binary, decimal, hexadecimal, octal
18613 and natural. Natural refers to a default format automatically
18614 chosen based on the variable type (like decimal for an @code{int}, hex
18615 for pointers, etc.).
18617 The following is the complete set of @sc{gdb/mi} operations defined to
18618 access this functionality:
18620 @multitable @columnfractions .4 .6
18621 @item @strong{Operation}
18622 @tab @strong{Description}
18624 @item @code{-var-create}
18625 @tab create a variable object
18626 @item @code{-var-delete}
18627 @tab delete the variable object and its children
18628 @item @code{-var-set-format}
18629 @tab set the display format of this variable
18630 @item @code{-var-show-format}
18631 @tab show the display format of this variable
18632 @item @code{-var-info-num-children}
18633 @tab tells how many children this object has
18634 @item @code{-var-list-children}
18635 @tab return a list of the object's children
18636 @item @code{-var-info-type}
18637 @tab show the type of this variable object
18638 @item @code{-var-info-expression}
18639 @tab print what this variable object represents
18640 @item @code{-var-show-attributes}
18641 @tab is this variable editable? does it exist here?
18642 @item @code{-var-evaluate-expression}
18643 @tab get the value of this variable
18644 @item @code{-var-assign}
18645 @tab set the value of this variable
18646 @item @code{-var-update}
18647 @tab update the variable and its children
18650 In the next subsection we describe each operation in detail and suggest
18651 how it can be used.
18653 @subheading Description And Use of Operations on Variable Objects
18655 @subheading The @code{-var-create} Command
18656 @findex -var-create
18658 @subsubheading Synopsis
18661 -var-create @{@var{name} | "-"@}
18662 @{@var{frame-addr} | "*"@} @var{expression}
18665 This operation creates a variable object, which allows the monitoring of
18666 a variable, the result of an expression, a memory cell or a CPU
18669 The @var{name} parameter is the string by which the object can be
18670 referenced. It must be unique. If @samp{-} is specified, the varobj
18671 system will generate a string ``varNNNNNN'' automatically. It will be
18672 unique provided that one does not specify @var{name} on that format.
18673 The command fails if a duplicate name is found.
18675 The frame under which the expression should be evaluated can be
18676 specified by @var{frame-addr}. A @samp{*} indicates that the current
18677 frame should be used.
18679 @var{expression} is any expression valid on the current language set (must not
18680 begin with a @samp{*}), or one of the following:
18684 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
18687 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
18690 @samp{$@var{regname}} --- a CPU register name
18693 @subsubheading Result
18695 This operation returns the name, number of children and the type of the
18696 object created. Type is returned as a string as the ones generated by
18697 the @value{GDBN} CLI:
18700 name="@var{name}",numchild="N",type="@var{type}"
18704 @subheading The @code{-var-delete} Command
18705 @findex -var-delete
18707 @subsubheading Synopsis
18710 -var-delete @var{name}
18713 Deletes a previously created variable object and all of its children.
18715 Returns an error if the object @var{name} is not found.
18718 @subheading The @code{-var-set-format} Command
18719 @findex -var-set-format
18721 @subsubheading Synopsis
18724 -var-set-format @var{name} @var{format-spec}
18727 Sets the output format for the value of the object @var{name} to be
18730 The syntax for the @var{format-spec} is as follows:
18733 @var{format-spec} @expansion{}
18734 @{binary | decimal | hexadecimal | octal | natural@}
18738 @subheading The @code{-var-show-format} Command
18739 @findex -var-show-format
18741 @subsubheading Synopsis
18744 -var-show-format @var{name}
18747 Returns the format used to display the value of the object @var{name}.
18750 @var{format} @expansion{}
18755 @subheading The @code{-var-info-num-children} Command
18756 @findex -var-info-num-children
18758 @subsubheading Synopsis
18761 -var-info-num-children @var{name}
18764 Returns the number of children of a variable object @var{name}:
18771 @subheading The @code{-var-list-children} Command
18772 @findex -var-list-children
18774 @subsubheading Synopsis
18777 -var-list-children [@var{print-values}] @var{name}
18780 Returns a list of the children of the specified variable object. With
18781 just the variable object name as an argument or with an optional
18782 preceding argument of 0 or @code{--no-values}, prints only the names of the
18783 variables. With an optional preceding argument of 1 or @code{--all-values},
18784 also prints their values.
18786 @subsubheading Example
18790 -var-list-children n
18791 numchild=@var{n},children=[@{name=@var{name},
18792 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
18794 -var-list-children --all-values n
18795 numchild=@var{n},children=[@{name=@var{name},
18796 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
18800 @subheading The @code{-var-info-type} Command
18801 @findex -var-info-type
18803 @subsubheading Synopsis
18806 -var-info-type @var{name}
18809 Returns the type of the specified variable @var{name}. The type is
18810 returned as a string in the same format as it is output by the
18814 type=@var{typename}
18818 @subheading The @code{-var-info-expression} Command
18819 @findex -var-info-expression
18821 @subsubheading Synopsis
18824 -var-info-expression @var{name}
18827 Returns what is represented by the variable object @var{name}:
18830 lang=@var{lang-spec},exp=@var{expression}
18834 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
18836 @subheading The @code{-var-show-attributes} Command
18837 @findex -var-show-attributes
18839 @subsubheading Synopsis
18842 -var-show-attributes @var{name}
18845 List attributes of the specified variable object @var{name}:
18848 status=@var{attr} [ ( ,@var{attr} )* ]
18852 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
18854 @subheading The @code{-var-evaluate-expression} Command
18855 @findex -var-evaluate-expression
18857 @subsubheading Synopsis
18860 -var-evaluate-expression @var{name}
18863 Evaluates the expression that is represented by the specified variable
18864 object and returns its value as a string in the current format specified
18871 Note that one must invoke @code{-var-list-children} for a variable
18872 before the value of a child variable can be evaluated.
18874 @subheading The @code{-var-assign} Command
18875 @findex -var-assign
18877 @subsubheading Synopsis
18880 -var-assign @var{name} @var{expression}
18883 Assigns the value of @var{expression} to the variable object specified
18884 by @var{name}. The object must be @samp{editable}. If the variable's
18885 value is altered by the assign, the variable will show up in any
18886 subsequent @code{-var-update} list.
18888 @subsubheading Example
18896 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
18900 @subheading The @code{-var-update} Command
18901 @findex -var-update
18903 @subsubheading Synopsis
18906 -var-update @{@var{name} | "*"@}
18909 Update the value of the variable object @var{name} by evaluating its
18910 expression after fetching all the new values from memory or registers.
18911 A @samp{*} causes all existing variable objects to be updated.
18915 @chapter @value{GDBN} Annotations
18917 This chapter describes annotations in @value{GDBN}. Annotations were
18918 designed to interface @value{GDBN} to graphical user interfaces or other
18919 similar programs which want to interact with @value{GDBN} at a
18920 relatively high level.
18922 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
18926 This is Edition @value{EDITION}, @value{DATE}.
18930 * Annotations Overview:: What annotations are; the general syntax.
18931 * Server Prefix:: Issuing a command without affecting user state.
18932 * Prompting:: Annotations marking @value{GDBN}'s need for input.
18933 * Errors:: Annotations for error messages.
18934 * Invalidation:: Some annotations describe things now invalid.
18935 * Annotations for Running::
18936 Whether the program is running, how it stopped, etc.
18937 * Source Annotations:: Annotations describing source code.
18940 @node Annotations Overview
18941 @section What is an Annotation?
18942 @cindex annotations
18944 Annotations start with a newline character, two @samp{control-z}
18945 characters, and the name of the annotation. If there is no additional
18946 information associated with this annotation, the name of the annotation
18947 is followed immediately by a newline. If there is additional
18948 information, the name of the annotation is followed by a space, the
18949 additional information, and a newline. The additional information
18950 cannot contain newline characters.
18952 Any output not beginning with a newline and two @samp{control-z}
18953 characters denotes literal output from @value{GDBN}. Currently there is
18954 no need for @value{GDBN} to output a newline followed by two
18955 @samp{control-z} characters, but if there was such a need, the
18956 annotations could be extended with an @samp{escape} annotation which
18957 means those three characters as output.
18959 The annotation @var{level}, which is specified using the
18960 @option{--annotate} command line option (@pxref{Mode Options}), controls
18961 how much information @value{GDBN} prints together with its prompt,
18962 values of expressions, source lines, and other types of output. Level 0
18963 is for no anntations, level 1 is for use when @value{GDBN} is run as a
18964 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
18965 for programs that control @value{GDBN}, and level 2 annotations have
18966 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
18967 Interface, annotate, GDB's Obsolete Annotations}). This chapter
18968 describes level 3 annotations.
18970 A simple example of starting up @value{GDBN} with annotations is:
18973 $ @kbd{gdb --annotate=3}
18975 Copyright 2003 Free Software Foundation, Inc.
18976 GDB is free software, covered by the GNU General Public License,
18977 and you are welcome to change it and/or distribute copies of it
18978 under certain conditions.
18979 Type "show copying" to see the conditions.
18980 There is absolutely no warranty for GDB. Type "show warranty"
18982 This GDB was configured as "i386-pc-linux-gnu"
18993 Here @samp{quit} is input to @value{GDBN}; the rest is output from
18994 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
18995 denotes a @samp{control-z} character) are annotations; the rest is
18996 output from @value{GDBN}.
18998 @node Server Prefix
18999 @section The Server Prefix
19000 @cindex server prefix for annotations
19002 To issue a command to @value{GDBN} without affecting certain aspects of
19003 the state which is seen by users, prefix it with @samp{server }. This
19004 means that this command will not affect the command history, nor will it
19005 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
19006 pressed on a line by itself.
19008 The server prefix does not affect the recording of values into the value
19009 history; to print a value without recording it into the value history,
19010 use the @code{output} command instead of the @code{print} command.
19013 @section Annotation for @value{GDBN} Input
19015 @cindex annotations for prompts
19016 When @value{GDBN} prompts for input, it annotates this fact so it is possible
19017 to know when to send output, when the output from a given command is
19020 Different kinds of input each have a different @dfn{input type}. Each
19021 input type has three annotations: a @code{pre-} annotation, which
19022 denotes the beginning of any prompt which is being output, a plain
19023 annotation, which denotes the end of the prompt, and then a @code{post-}
19024 annotation which denotes the end of any echo which may (or may not) be
19025 associated with the input. For example, the @code{prompt} input type
19026 features the following annotations:
19034 The input types are
19039 @findex post-prompt
19041 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
19043 @findex pre-commands
19045 @findex post-commands
19047 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
19048 command. The annotations are repeated for each command which is input.
19050 @findex pre-overload-choice
19051 @findex overload-choice
19052 @findex post-overload-choice
19053 @item overload-choice
19054 When @value{GDBN} wants the user to select between various overloaded functions.
19060 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
19062 @findex pre-prompt-for-continue
19063 @findex prompt-for-continue
19064 @findex post-prompt-for-continue
19065 @item prompt-for-continue
19066 When @value{GDBN} is asking the user to press return to continue. Note: Don't
19067 expect this to work well; instead use @code{set height 0} to disable
19068 prompting. This is because the counting of lines is buggy in the
19069 presence of annotations.
19074 @cindex annotations for errors, warnings and interrupts
19081 This annotation occurs right before @value{GDBN} responds to an interrupt.
19088 This annotation occurs right before @value{GDBN} responds to an error.
19090 Quit and error annotations indicate that any annotations which @value{GDBN} was
19091 in the middle of may end abruptly. For example, if a
19092 @code{value-history-begin} annotation is followed by a @code{error}, one
19093 cannot expect to receive the matching @code{value-history-end}. One
19094 cannot expect not to receive it either, however; an error annotation
19095 does not necessarily mean that @value{GDBN} is immediately returning all the way
19098 @findex error-begin
19099 A quit or error annotation may be preceded by
19105 Any output between that and the quit or error annotation is the error
19108 Warning messages are not yet annotated.
19109 @c If we want to change that, need to fix warning(), type_error(),
19110 @c range_error(), and possibly other places.
19113 @section Invalidation Notices
19115 @cindex annotations for invalidation messages
19116 The following annotations say that certain pieces of state may have
19120 @findex frames-invalid
19121 @item ^Z^Zframes-invalid
19123 The frames (for example, output from the @code{backtrace} command) may
19126 @findex breakpoints-invalid
19127 @item ^Z^Zbreakpoints-invalid
19129 The breakpoints may have changed. For example, the user just added or
19130 deleted a breakpoint.
19133 @node Annotations for Running
19134 @section Running the Program
19135 @cindex annotations for running programs
19139 When the program starts executing due to a @value{GDBN} command such as
19140 @code{step} or @code{continue},
19146 is output. When the program stops,
19152 is output. Before the @code{stopped} annotation, a variety of
19153 annotations describe how the program stopped.
19157 @item ^Z^Zexited @var{exit-status}
19158 The program exited, and @var{exit-status} is the exit status (zero for
19159 successful exit, otherwise nonzero).
19162 @findex signal-name
19163 @findex signal-name-end
19164 @findex signal-string
19165 @findex signal-string-end
19166 @item ^Z^Zsignalled
19167 The program exited with a signal. After the @code{^Z^Zsignalled}, the
19168 annotation continues:
19174 ^Z^Zsignal-name-end
19178 ^Z^Zsignal-string-end
19183 where @var{name} is the name of the signal, such as @code{SIGILL} or
19184 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
19185 as @code{Illegal Instruction} or @code{Segmentation fault}.
19186 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
19187 user's benefit and have no particular format.
19191 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
19192 just saying that the program received the signal, not that it was
19193 terminated with it.
19196 @item ^Z^Zbreakpoint @var{number}
19197 The program hit breakpoint number @var{number}.
19200 @item ^Z^Zwatchpoint @var{number}
19201 The program hit watchpoint number @var{number}.
19204 @node Source Annotations
19205 @section Displaying Source
19206 @cindex annotations for source display
19209 The following annotation is used instead of displaying source code:
19212 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
19215 where @var{filename} is an absolute file name indicating which source
19216 file, @var{line} is the line number within that file (where 1 is the
19217 first line in the file), @var{character} is the character position
19218 within the file (where 0 is the first character in the file) (for most
19219 debug formats this will necessarily point to the beginning of a line),
19220 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
19221 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
19222 @var{addr} is the address in the target program associated with the
19223 source which is being displayed. @var{addr} is in the form @samp{0x}
19224 followed by one or more lowercase hex digits (note that this does not
19225 depend on the language).
19228 @chapter Reporting Bugs in @value{GDBN}
19229 @cindex bugs in @value{GDBN}
19230 @cindex reporting bugs in @value{GDBN}
19232 Your bug reports play an essential role in making @value{GDBN} reliable.
19234 Reporting a bug may help you by bringing a solution to your problem, or it
19235 may not. But in any case the principal function of a bug report is to help
19236 the entire community by making the next version of @value{GDBN} work better. Bug
19237 reports are your contribution to the maintenance of @value{GDBN}.
19239 In order for a bug report to serve its purpose, you must include the
19240 information that enables us to fix the bug.
19243 * Bug Criteria:: Have you found a bug?
19244 * Bug Reporting:: How to report bugs
19248 @section Have you found a bug?
19249 @cindex bug criteria
19251 If you are not sure whether you have found a bug, here are some guidelines:
19254 @cindex fatal signal
19255 @cindex debugger crash
19256 @cindex crash of debugger
19258 If the debugger gets a fatal signal, for any input whatever, that is a
19259 @value{GDBN} bug. Reliable debuggers never crash.
19261 @cindex error on valid input
19263 If @value{GDBN} produces an error message for valid input, that is a
19264 bug. (Note that if you're cross debugging, the problem may also be
19265 somewhere in the connection to the target.)
19267 @cindex invalid input
19269 If @value{GDBN} does not produce an error message for invalid input,
19270 that is a bug. However, you should note that your idea of
19271 ``invalid input'' might be our idea of ``an extension'' or ``support
19272 for traditional practice''.
19275 If you are an experienced user of debugging tools, your suggestions
19276 for improvement of @value{GDBN} are welcome in any case.
19279 @node Bug Reporting
19280 @section How to report bugs
19281 @cindex bug reports
19282 @cindex @value{GDBN} bugs, reporting
19284 A number of companies and individuals offer support for @sc{gnu} products.
19285 If you obtained @value{GDBN} from a support organization, we recommend you
19286 contact that organization first.
19288 You can find contact information for many support companies and
19289 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
19291 @c should add a web page ref...
19293 In any event, we also recommend that you submit bug reports for
19294 @value{GDBN}. The prefered method is to submit them directly using
19295 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
19296 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
19299 @strong{Do not send bug reports to @samp{info-gdb}, or to
19300 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
19301 not want to receive bug reports. Those that do have arranged to receive
19304 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
19305 serves as a repeater. The mailing list and the newsgroup carry exactly
19306 the same messages. Often people think of posting bug reports to the
19307 newsgroup instead of mailing them. This appears to work, but it has one
19308 problem which can be crucial: a newsgroup posting often lacks a mail
19309 path back to the sender. Thus, if we need to ask for more information,
19310 we may be unable to reach you. For this reason, it is better to send
19311 bug reports to the mailing list.
19313 The fundamental principle of reporting bugs usefully is this:
19314 @strong{report all the facts}. If you are not sure whether to state a
19315 fact or leave it out, state it!
19317 Often people omit facts because they think they know what causes the
19318 problem and assume that some details do not matter. Thus, you might
19319 assume that the name of the variable you use in an example does not matter.
19320 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
19321 stray memory reference which happens to fetch from the location where that
19322 name is stored in memory; perhaps, if the name were different, the contents
19323 of that location would fool the debugger into doing the right thing despite
19324 the bug. Play it safe and give a specific, complete example. That is the
19325 easiest thing for you to do, and the most helpful.
19327 Keep in mind that the purpose of a bug report is to enable us to fix the
19328 bug. It may be that the bug has been reported previously, but neither
19329 you nor we can know that unless your bug report is complete and
19332 Sometimes people give a few sketchy facts and ask, ``Does this ring a
19333 bell?'' Those bug reports are useless, and we urge everyone to
19334 @emph{refuse to respond to them} except to chide the sender to report
19337 To enable us to fix the bug, you should include all these things:
19341 The version of @value{GDBN}. @value{GDBN} announces it if you start
19342 with no arguments; you can also print it at any time using @code{show
19345 Without this, we will not know whether there is any point in looking for
19346 the bug in the current version of @value{GDBN}.
19349 The type of machine you are using, and the operating system name and
19353 What compiler (and its version) was used to compile @value{GDBN}---e.g.
19354 ``@value{GCC}--2.8.1''.
19357 What compiler (and its version) was used to compile the program you are
19358 debugging---e.g. ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
19359 C Compiler''. For GCC, you can say @code{gcc --version} to get this
19360 information; for other compilers, see the documentation for those
19364 The command arguments you gave the compiler to compile your example and
19365 observe the bug. For example, did you use @samp{-O}? To guarantee
19366 you will not omit something important, list them all. A copy of the
19367 Makefile (or the output from make) is sufficient.
19369 If we were to try to guess the arguments, we would probably guess wrong
19370 and then we might not encounter the bug.
19373 A complete input script, and all necessary source files, that will
19377 A description of what behavior you observe that you believe is
19378 incorrect. For example, ``It gets a fatal signal.''
19380 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
19381 will certainly notice it. But if the bug is incorrect output, we might
19382 not notice unless it is glaringly wrong. You might as well not give us
19383 a chance to make a mistake.
19385 Even if the problem you experience is a fatal signal, you should still
19386 say so explicitly. Suppose something strange is going on, such as, your
19387 copy of @value{GDBN} is out of synch, or you have encountered a bug in
19388 the C library on your system. (This has happened!) Your copy might
19389 crash and ours would not. If you told us to expect a crash, then when
19390 ours fails to crash, we would know that the bug was not happening for
19391 us. If you had not told us to expect a crash, then we would not be able
19392 to draw any conclusion from our observations.
19395 @cindex recording a session script
19396 To collect all this information, you can use a session recording program
19397 such as @command{script}, which is available on many Unix systems.
19398 Just run your @value{GDBN} session inside @command{script} and then
19399 include the @file{typescript} file with your bug report.
19401 Another way to record a @value{GDBN} session is to run @value{GDBN}
19402 inside Emacs and then save the entire buffer to a file.
19405 If you wish to suggest changes to the @value{GDBN} source, send us context
19406 diffs. If you even discuss something in the @value{GDBN} source, refer to
19407 it by context, not by line number.
19409 The line numbers in our development sources will not match those in your
19410 sources. Your line numbers would convey no useful information to us.
19414 Here are some things that are not necessary:
19418 A description of the envelope of the bug.
19420 Often people who encounter a bug spend a lot of time investigating
19421 which changes to the input file will make the bug go away and which
19422 changes will not affect it.
19424 This is often time consuming and not very useful, because the way we
19425 will find the bug is by running a single example under the debugger
19426 with breakpoints, not by pure deduction from a series of examples.
19427 We recommend that you save your time for something else.
19429 Of course, if you can find a simpler example to report @emph{instead}
19430 of the original one, that is a convenience for us. Errors in the
19431 output will be easier to spot, running under the debugger will take
19432 less time, and so on.
19434 However, simplification is not vital; if you do not want to do this,
19435 report the bug anyway and send us the entire test case you used.
19438 A patch for the bug.
19440 A patch for the bug does help us if it is a good one. But do not omit
19441 the necessary information, such as the test case, on the assumption that
19442 a patch is all we need. We might see problems with your patch and decide
19443 to fix the problem another way, or we might not understand it at all.
19445 Sometimes with a program as complicated as @value{GDBN} it is very hard to
19446 construct an example that will make the program follow a certain path
19447 through the code. If you do not send us the example, we will not be able
19448 to construct one, so we will not be able to verify that the bug is fixed.
19450 And if we cannot understand what bug you are trying to fix, or why your
19451 patch should be an improvement, we will not install it. A test case will
19452 help us to understand.
19455 A guess about what the bug is or what it depends on.
19457 Such guesses are usually wrong. Even we cannot guess right about such
19458 things without first using the debugger to find the facts.
19461 @c The readline documentation is distributed with the readline code
19462 @c and consists of the two following files:
19464 @c inc-hist.texinfo
19465 @c Use -I with makeinfo to point to the appropriate directory,
19466 @c environment var TEXINPUTS with TeX.
19467 @include rluser.texinfo
19468 @include inc-hist.texinfo
19471 @node Formatting Documentation
19472 @appendix Formatting Documentation
19474 @cindex @value{GDBN} reference card
19475 @cindex reference card
19476 The @value{GDBN} 4 release includes an already-formatted reference card, ready
19477 for printing with PostScript or Ghostscript, in the @file{gdb}
19478 subdirectory of the main source directory@footnote{In
19479 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
19480 release.}. If you can use PostScript or Ghostscript with your printer,
19481 you can print the reference card immediately with @file{refcard.ps}.
19483 The release also includes the source for the reference card. You
19484 can format it, using @TeX{}, by typing:
19490 The @value{GDBN} reference card is designed to print in @dfn{landscape}
19491 mode on US ``letter'' size paper;
19492 that is, on a sheet 11 inches wide by 8.5 inches
19493 high. You will need to specify this form of printing as an option to
19494 your @sc{dvi} output program.
19496 @cindex documentation
19498 All the documentation for @value{GDBN} comes as part of the machine-readable
19499 distribution. The documentation is written in Texinfo format, which is
19500 a documentation system that uses a single source file to produce both
19501 on-line information and a printed manual. You can use one of the Info
19502 formatting commands to create the on-line version of the documentation
19503 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
19505 @value{GDBN} includes an already formatted copy of the on-line Info
19506 version of this manual in the @file{gdb} subdirectory. The main Info
19507 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
19508 subordinate files matching @samp{gdb.info*} in the same directory. If
19509 necessary, you can print out these files, or read them with any editor;
19510 but they are easier to read using the @code{info} subsystem in @sc{gnu}
19511 Emacs or the standalone @code{info} program, available as part of the
19512 @sc{gnu} Texinfo distribution.
19514 If you want to format these Info files yourself, you need one of the
19515 Info formatting programs, such as @code{texinfo-format-buffer} or
19518 If you have @code{makeinfo} installed, and are in the top level
19519 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
19520 version @value{GDBVN}), you can make the Info file by typing:
19527 If you want to typeset and print copies of this manual, you need @TeX{},
19528 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
19529 Texinfo definitions file.
19531 @TeX{} is a typesetting program; it does not print files directly, but
19532 produces output files called @sc{dvi} files. To print a typeset
19533 document, you need a program to print @sc{dvi} files. If your system
19534 has @TeX{} installed, chances are it has such a program. The precise
19535 command to use depends on your system; @kbd{lpr -d} is common; another
19536 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
19537 require a file name without any extension or a @samp{.dvi} extension.
19539 @TeX{} also requires a macro definitions file called
19540 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
19541 written in Texinfo format. On its own, @TeX{} cannot either read or
19542 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
19543 and is located in the @file{gdb-@var{version-number}/texinfo}
19546 If you have @TeX{} and a @sc{dvi} printer program installed, you can
19547 typeset and print this manual. First switch to the the @file{gdb}
19548 subdirectory of the main source directory (for example, to
19549 @file{gdb-@value{GDBVN}/gdb}) and type:
19555 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
19557 @node Installing GDB
19558 @appendix Installing @value{GDBN}
19559 @cindex configuring @value{GDBN}
19560 @cindex installation
19561 @cindex configuring @value{GDBN}, and source tree subdirectories
19563 @value{GDBN} comes with a @code{configure} script that automates the process
19564 of preparing @value{GDBN} for installation; you can then use @code{make} to
19565 build the @code{gdb} program.
19567 @c irrelevant in info file; it's as current as the code it lives with.
19568 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
19569 look at the @file{README} file in the sources; we may have improved the
19570 installation procedures since publishing this manual.}
19573 The @value{GDBN} distribution includes all the source code you need for
19574 @value{GDBN} in a single directory, whose name is usually composed by
19575 appending the version number to @samp{gdb}.
19577 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
19578 @file{gdb-@value{GDBVN}} directory. That directory contains:
19581 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
19582 script for configuring @value{GDBN} and all its supporting libraries
19584 @item gdb-@value{GDBVN}/gdb
19585 the source specific to @value{GDBN} itself
19587 @item gdb-@value{GDBVN}/bfd
19588 source for the Binary File Descriptor library
19590 @item gdb-@value{GDBVN}/include
19591 @sc{gnu} include files
19593 @item gdb-@value{GDBVN}/libiberty
19594 source for the @samp{-liberty} free software library
19596 @item gdb-@value{GDBVN}/opcodes
19597 source for the library of opcode tables and disassemblers
19599 @item gdb-@value{GDBVN}/readline
19600 source for the @sc{gnu} command-line interface
19602 @item gdb-@value{GDBVN}/glob
19603 source for the @sc{gnu} filename pattern-matching subroutine
19605 @item gdb-@value{GDBVN}/mmalloc
19606 source for the @sc{gnu} memory-mapped malloc package
19609 The simplest way to configure and build @value{GDBN} is to run @code{configure}
19610 from the @file{gdb-@var{version-number}} source directory, which in
19611 this example is the @file{gdb-@value{GDBVN}} directory.
19613 First switch to the @file{gdb-@var{version-number}} source directory
19614 if you are not already in it; then run @code{configure}. Pass the
19615 identifier for the platform on which @value{GDBN} will run as an
19621 cd gdb-@value{GDBVN}
19622 ./configure @var{host}
19627 where @var{host} is an identifier such as @samp{sun4} or
19628 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
19629 (You can often leave off @var{host}; @code{configure} tries to guess the
19630 correct value by examining your system.)
19632 Running @samp{configure @var{host}} and then running @code{make} builds the
19633 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
19634 libraries, then @code{gdb} itself. The configured source files, and the
19635 binaries, are left in the corresponding source directories.
19638 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
19639 system does not recognize this automatically when you run a different
19640 shell, you may need to run @code{sh} on it explicitly:
19643 sh configure @var{host}
19646 If you run @code{configure} from a directory that contains source
19647 directories for multiple libraries or programs, such as the
19648 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
19649 creates configuration files for every directory level underneath (unless
19650 you tell it not to, with the @samp{--norecursion} option).
19652 You should run the @code{configure} script from the top directory in the
19653 source tree, the @file{gdb-@var{version-number}} directory. If you run
19654 @code{configure} from one of the subdirectories, you will configure only
19655 that subdirectory. That is usually not what you want. In particular,
19656 if you run the first @code{configure} from the @file{gdb} subdirectory
19657 of the @file{gdb-@var{version-number}} directory, you will omit the
19658 configuration of @file{bfd}, @file{readline}, and other sibling
19659 directories of the @file{gdb} subdirectory. This leads to build errors
19660 about missing include files such as @file{bfd/bfd.h}.
19662 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
19663 However, you should make sure that the shell on your path (named by
19664 the @samp{SHELL} environment variable) is publicly readable. Remember
19665 that @value{GDBN} uses the shell to start your program---some systems refuse to
19666 let @value{GDBN} debug child processes whose programs are not readable.
19669 * Separate Objdir:: Compiling @value{GDBN} in another directory
19670 * Config Names:: Specifying names for hosts and targets
19671 * Configure Options:: Summary of options for configure
19674 @node Separate Objdir
19675 @section Compiling @value{GDBN} in another directory
19677 If you want to run @value{GDBN} versions for several host or target machines,
19678 you need a different @code{gdb} compiled for each combination of
19679 host and target. @code{configure} is designed to make this easy by
19680 allowing you to generate each configuration in a separate subdirectory,
19681 rather than in the source directory. If your @code{make} program
19682 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
19683 @code{make} in each of these directories builds the @code{gdb}
19684 program specified there.
19686 To build @code{gdb} in a separate directory, run @code{configure}
19687 with the @samp{--srcdir} option to specify where to find the source.
19688 (You also need to specify a path to find @code{configure}
19689 itself from your working directory. If the path to @code{configure}
19690 would be the same as the argument to @samp{--srcdir}, you can leave out
19691 the @samp{--srcdir} option; it is assumed.)
19693 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
19694 separate directory for a Sun 4 like this:
19698 cd gdb-@value{GDBVN}
19701 ../gdb-@value{GDBVN}/configure sun4
19706 When @code{configure} builds a configuration using a remote source
19707 directory, it creates a tree for the binaries with the same structure
19708 (and using the same names) as the tree under the source directory. In
19709 the example, you'd find the Sun 4 library @file{libiberty.a} in the
19710 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
19711 @file{gdb-sun4/gdb}.
19713 Make sure that your path to the @file{configure} script has just one
19714 instance of @file{gdb} in it. If your path to @file{configure} looks
19715 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
19716 one subdirectory of @value{GDBN}, not the whole package. This leads to
19717 build errors about missing include files such as @file{bfd/bfd.h}.
19719 One popular reason to build several @value{GDBN} configurations in separate
19720 directories is to configure @value{GDBN} for cross-compiling (where
19721 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
19722 programs that run on another machine---the @dfn{target}).
19723 You specify a cross-debugging target by
19724 giving the @samp{--target=@var{target}} option to @code{configure}.
19726 When you run @code{make} to build a program or library, you must run
19727 it in a configured directory---whatever directory you were in when you
19728 called @code{configure} (or one of its subdirectories).
19730 The @code{Makefile} that @code{configure} generates in each source
19731 directory also runs recursively. If you type @code{make} in a source
19732 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
19733 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
19734 will build all the required libraries, and then build GDB.
19736 When you have multiple hosts or targets configured in separate
19737 directories, you can run @code{make} on them in parallel (for example,
19738 if they are NFS-mounted on each of the hosts); they will not interfere
19742 @section Specifying names for hosts and targets
19744 The specifications used for hosts and targets in the @code{configure}
19745 script are based on a three-part naming scheme, but some short predefined
19746 aliases are also supported. The full naming scheme encodes three pieces
19747 of information in the following pattern:
19750 @var{architecture}-@var{vendor}-@var{os}
19753 For example, you can use the alias @code{sun4} as a @var{host} argument,
19754 or as the value for @var{target} in a @code{--target=@var{target}}
19755 option. The equivalent full name is @samp{sparc-sun-sunos4}.
19757 The @code{configure} script accompanying @value{GDBN} does not provide
19758 any query facility to list all supported host and target names or
19759 aliases. @code{configure} calls the Bourne shell script
19760 @code{config.sub} to map abbreviations to full names; you can read the
19761 script, if you wish, or you can use it to test your guesses on
19762 abbreviations---for example:
19765 % sh config.sub i386-linux
19767 % sh config.sub alpha-linux
19768 alpha-unknown-linux-gnu
19769 % sh config.sub hp9k700
19771 % sh config.sub sun4
19772 sparc-sun-sunos4.1.1
19773 % sh config.sub sun3
19774 m68k-sun-sunos4.1.1
19775 % sh config.sub i986v
19776 Invalid configuration `i986v': machine `i986v' not recognized
19780 @code{config.sub} is also distributed in the @value{GDBN} source
19781 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
19783 @node Configure Options
19784 @section @code{configure} options
19786 Here is a summary of the @code{configure} options and arguments that
19787 are most often useful for building @value{GDBN}. @code{configure} also has
19788 several other options not listed here. @inforef{What Configure
19789 Does,,configure.info}, for a full explanation of @code{configure}.
19792 configure @r{[}--help@r{]}
19793 @r{[}--prefix=@var{dir}@r{]}
19794 @r{[}--exec-prefix=@var{dir}@r{]}
19795 @r{[}--srcdir=@var{dirname}@r{]}
19796 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
19797 @r{[}--target=@var{target}@r{]}
19802 You may introduce options with a single @samp{-} rather than
19803 @samp{--} if you prefer; but you may abbreviate option names if you use
19808 Display a quick summary of how to invoke @code{configure}.
19810 @item --prefix=@var{dir}
19811 Configure the source to install programs and files under directory
19814 @item --exec-prefix=@var{dir}
19815 Configure the source to install programs under directory
19818 @c avoid splitting the warning from the explanation:
19820 @item --srcdir=@var{dirname}
19821 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
19822 @code{make} that implements the @code{VPATH} feature.}@*
19823 Use this option to make configurations in directories separate from the
19824 @value{GDBN} source directories. Among other things, you can use this to
19825 build (or maintain) several configurations simultaneously, in separate
19826 directories. @code{configure} writes configuration specific files in
19827 the current directory, but arranges for them to use the source in the
19828 directory @var{dirname}. @code{configure} creates directories under
19829 the working directory in parallel to the source directories below
19832 @item --norecursion
19833 Configure only the directory level where @code{configure} is executed; do not
19834 propagate configuration to subdirectories.
19836 @item --target=@var{target}
19837 Configure @value{GDBN} for cross-debugging programs running on the specified
19838 @var{target}. Without this option, @value{GDBN} is configured to debug
19839 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
19841 There is no convenient way to generate a list of all available targets.
19843 @item @var{host} @dots{}
19844 Configure @value{GDBN} to run on the specified @var{host}.
19846 There is no convenient way to generate a list of all available hosts.
19849 There are many other options available as well, but they are generally
19850 needed for special purposes only.
19852 @node Maintenance Commands
19853 @appendix Maintenance Commands
19854 @cindex maintenance commands
19855 @cindex internal commands
19857 In addition to commands intended for @value{GDBN} users, @value{GDBN}
19858 includes a number of commands intended for @value{GDBN} developers.
19859 These commands are provided here for reference.
19862 @kindex maint info breakpoints
19863 @item @anchor{maint info breakpoints}maint info breakpoints
19864 Using the same format as @samp{info breakpoints}, display both the
19865 breakpoints you've set explicitly, and those @value{GDBN} is using for
19866 internal purposes. Internal breakpoints are shown with negative
19867 breakpoint numbers. The type column identifies what kind of breakpoint
19872 Normal, explicitly set breakpoint.
19875 Normal, explicitly set watchpoint.
19878 Internal breakpoint, used to handle correctly stepping through
19879 @code{longjmp} calls.
19881 @item longjmp resume
19882 Internal breakpoint at the target of a @code{longjmp}.
19885 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
19888 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
19891 Shared library events.
19895 @kindex maint internal-error
19896 @kindex maint internal-warning
19897 @item maint internal-error
19898 @itemx maint internal-warning
19899 Cause @value{GDBN} to call the internal function @code{internal_error}
19900 or @code{internal_warning} and hence behave as though an internal error
19901 or internal warning has been detected. In addition to reporting the
19902 internal problem, these functions give the user the opportunity to
19903 either quit @value{GDBN} or create a core file of the current
19904 @value{GDBN} session.
19907 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
19908 @dots{}/maint.c:121: internal-error: testing, 1, 2
19909 A problem internal to GDB has been detected. Further
19910 debugging may prove unreliable.
19911 Quit this debugging session? (y or n) @kbd{n}
19912 Create a core file? (y or n) @kbd{n}
19916 Takes an optional parameter that is used as the text of the error or
19919 @kindex maint print dummy-frames
19920 @item maint print dummy-frames
19922 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
19925 (@value{GDBP}) @kbd{b add}
19927 (@value{GDBP}) @kbd{print add(2,3)}
19928 Breakpoint 2, add (a=2, b=3) at @dots{}
19930 The program being debugged stopped while in a function called from GDB.
19932 (@value{GDBP}) @kbd{maint print dummy-frames}
19933 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
19934 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
19935 call_lo=0x01014000 call_hi=0x01014001
19939 Takes an optional file parameter.
19941 @kindex maint print registers
19942 @kindex maint print raw-registers
19943 @kindex maint print cooked-registers
19944 @kindex maint print register-groups
19945 @item maint print registers
19946 @itemx maint print raw-registers
19947 @itemx maint print cooked-registers
19948 @itemx maint print register-groups
19949 Print @value{GDBN}'s internal register data structures.
19951 The command @code{maint print raw-registers} includes the contents of
19952 the raw register cache; the command @code{maint print cooked-registers}
19953 includes the (cooked) value of all registers; and the command
19954 @code{maint print register-groups} includes the groups that each
19955 register is a member of. @xref{Registers,, Registers, gdbint,
19956 @value{GDBN} Internals}.
19958 Takes an optional file parameter.
19960 @kindex maint print reggroups
19961 @item maint print reggroups
19962 Print @value{GDBN}'s internal register group data structures.
19964 Takes an optional file parameter.
19967 (@value{GDBP}) @kbd{maint print reggroups}
19978 @kindex maint set profile
19979 @kindex maint show profile
19980 @cindex profiling GDB
19981 @item maint set profile
19982 @itemx maint show profile
19983 Control profiling of @value{GDBN}.
19985 Profiling will be disabled until you use the @samp{maint set profile}
19986 command to enable it. When you enable profiling, the system will begin
19987 collecting timing and execution count data; when you disable profiling or
19988 exit @value{GDBN}, the results will be written to a log file. Remember that
19989 if you use profiling, @value{GDBN} will overwrite the profiling log file
19990 (often called @file{gmon.out}). If you have a record of important profiling
19991 data in a @file{gmon.out} file, be sure to move it to a safe location.
19993 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
19994 compiled with the @samp{-pg} compiler option.
19996 @kindex maint set dwarf2 max-cache-age
19997 @kindex maint show dwarf2 max-cache-age
19998 @item maint set dwarf2 max-cache-age
19999 @itemx maint show dwarf2 max-cache-age
20000 Control the DWARF 2 compilation unit cache.
20002 In object files with inter-compilation-unit references, such as those
20003 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
20004 reader needs to frequently refer to previously read compilation units.
20005 This setting controls how long a compilation unit will remain in the cache
20006 if it is not referenced. Setting it to zero disables caching, which will
20007 slow down @value{GDBN} startup but reduce memory consumption.
20012 @node Remote Protocol
20013 @appendix @value{GDBN} Remote Serial Protocol
20018 * Stop Reply Packets::
20019 * General Query Packets::
20020 * Register Packet Format::
20022 * File-I/O remote protocol extension::
20028 There may be occasions when you need to know something about the
20029 protocol---for example, if there is only one serial port to your target
20030 machine, you might want your program to do something special if it
20031 recognizes a packet meant for @value{GDBN}.
20033 In the examples below, @samp{->} and @samp{<-} are used to indicate
20034 transmitted and received data respectfully.
20036 @cindex protocol, @value{GDBN} remote serial
20037 @cindex serial protocol, @value{GDBN} remote
20038 @cindex remote serial protocol
20039 All @value{GDBN} commands and responses (other than acknowledgments) are
20040 sent as a @var{packet}. A @var{packet} is introduced with the character
20041 @samp{$}, the actual @var{packet-data}, and the terminating character
20042 @samp{#} followed by a two-digit @var{checksum}:
20045 @code{$}@var{packet-data}@code{#}@var{checksum}
20049 @cindex checksum, for @value{GDBN} remote
20051 The two-digit @var{checksum} is computed as the modulo 256 sum of all
20052 characters between the leading @samp{$} and the trailing @samp{#} (an
20053 eight bit unsigned checksum).
20055 Implementors should note that prior to @value{GDBN} 5.0 the protocol
20056 specification also included an optional two-digit @var{sequence-id}:
20059 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
20062 @cindex sequence-id, for @value{GDBN} remote
20064 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
20065 has never output @var{sequence-id}s. Stubs that handle packets added
20066 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
20068 @cindex acknowledgment, for @value{GDBN} remote
20069 When either the host or the target machine receives a packet, the first
20070 response expected is an acknowledgment: either @samp{+} (to indicate
20071 the package was received correctly) or @samp{-} (to request
20075 -> @code{$}@var{packet-data}@code{#}@var{checksum}
20080 The host (@value{GDBN}) sends @var{command}s, and the target (the
20081 debugging stub incorporated in your program) sends a @var{response}. In
20082 the case of step and continue @var{command}s, the response is only sent
20083 when the operation has completed (the target has again stopped).
20085 @var{packet-data} consists of a sequence of characters with the
20086 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
20089 Fields within the packet should be separated using @samp{,} @samp{;} or
20090 @cindex remote protocol, field separator
20091 @samp{:}. Except where otherwise noted all numbers are represented in
20092 @sc{hex} with leading zeros suppressed.
20094 Implementors should note that prior to @value{GDBN} 5.0, the character
20095 @samp{:} could not appear as the third character in a packet (as it
20096 would potentially conflict with the @var{sequence-id}).
20098 Response @var{data} can be run-length encoded to save space. A @samp{*}
20099 means that the next character is an @sc{ascii} encoding giving a repeat count
20100 which stands for that many repetitions of the character preceding the
20101 @samp{*}. The encoding is @code{n+29}, yielding a printable character
20102 where @code{n >=3} (which is where rle starts to win). The printable
20103 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
20104 value greater than 126 should not be used.
20111 means the same as "0000".
20113 The error response returned for some packets includes a two character
20114 error number. That number is not well defined.
20116 For any @var{command} not supported by the stub, an empty response
20117 (@samp{$#00}) should be returned. That way it is possible to extend the
20118 protocol. A newer @value{GDBN} can tell if a packet is supported based
20121 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
20122 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
20128 The following table provides a complete list of all currently defined
20129 @var{command}s and their corresponding response @var{data}.
20133 @item @code{!} --- extended mode
20134 @cindex @code{!} packet
20136 Enable extended mode. In extended mode, the remote server is made
20137 persistent. The @samp{R} packet is used to restart the program being
20143 The remote target both supports and has enabled extended mode.
20146 @item @code{?} --- last signal
20147 @cindex @code{?} packet
20149 Indicate the reason the target halted. The reply is the same as for
20153 @xref{Stop Reply Packets}, for the reply specifications.
20155 @item @code{a} --- reserved
20157 Reserved for future use.
20159 @item @code{A}@var{arglen}@code{,}@var{argnum}@code{,}@var{arg}@code{,@dots{}} --- set program arguments @strong{(reserved)}
20160 @cindex @code{A} packet
20162 Initialized @samp{argv[]} array passed into program. @var{arglen}
20163 specifies the number of bytes in the hex encoded byte stream @var{arg}.
20164 See @code{gdbserver} for more details.
20172 @item @code{b}@var{baud} --- set baud @strong{(deprecated)}
20173 @cindex @code{b} packet
20175 Change the serial line speed to @var{baud}.
20177 JTC: @emph{When does the transport layer state change? When it's
20178 received, or after the ACK is transmitted. In either case, there are
20179 problems if the command or the acknowledgment packet is dropped.}
20181 Stan: @emph{If people really wanted to add something like this, and get
20182 it working for the first time, they ought to modify ser-unix.c to send
20183 some kind of out-of-band message to a specially-setup stub and have the
20184 switch happen "in between" packets, so that from remote protocol's point
20185 of view, nothing actually happened.}
20187 @item @code{B}@var{addr},@var{mode} --- set breakpoint @strong{(deprecated)}
20188 @cindex @code{B} packet
20190 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
20191 breakpoint at @var{addr}.
20193 This packet has been replaced by the @samp{Z} and @samp{z} packets
20194 (@pxref{insert breakpoint or watchpoint packet}).
20196 @item @code{c}@var{addr} --- continue
20197 @cindex @code{c} packet
20199 @var{addr} is address to resume. If @var{addr} is omitted, resume at
20203 @xref{Stop Reply Packets}, for the reply specifications.
20205 @item @code{C}@var{sig}@code{;}@var{addr} --- continue with signal
20206 @cindex @code{C} packet
20208 Continue with signal @var{sig} (hex signal number). If
20209 @code{;}@var{addr} is omitted, resume at same address.
20212 @xref{Stop Reply Packets}, for the reply specifications.
20214 @item @code{d} --- toggle debug @strong{(deprecated)}
20215 @cindex @code{d} packet
20219 @item @code{D} --- detach
20220 @cindex @code{D} packet
20222 Detach @value{GDBN} from the remote system. Sent to the remote target
20223 before @value{GDBN} disconnects via the @code{detach} command.
20227 @item @emph{no response}
20228 @value{GDBN} does not check for any response after sending this packet.
20231 @item @code{e} --- reserved
20233 Reserved for future use.
20235 @item @code{E} --- reserved
20237 Reserved for future use.
20239 @item @code{f} --- reserved
20241 Reserved for future use.
20243 @item @code{F}@var{RC}@code{,}@var{EE}@code{,}@var{CF}@code{;}@var{XX} --- Reply to target's F packet.
20244 @cindex @code{F} packet
20246 This packet is send by @value{GDBN} as reply to a @code{F} request packet
20247 sent by the target. This is part of the File-I/O protocol extension.
20248 @xref{File-I/O remote protocol extension}, for the specification.
20250 @item @code{g} --- read registers
20251 @anchor{read registers packet}
20252 @cindex @code{g} packet
20254 Read general registers.
20258 @item @var{XX@dots{}}
20259 Each byte of register data is described by two hex digits. The bytes
20260 with the register are transmitted in target byte order. The size of
20261 each register and their position within the @samp{g} @var{packet} are
20262 determined by the @value{GDBN} internal macros
20263 @var{DEPRECATED_REGISTER_RAW_SIZE} and @var{REGISTER_NAME} macros. The
20264 specification of several standard @code{g} packets is specified below.
20269 @item @code{G}@var{XX@dots{}} --- write regs
20270 @cindex @code{G} packet
20272 @xref{read registers packet}, for a description of the @var{XX@dots{}}
20283 @item @code{h} --- reserved
20285 Reserved for future use.
20287 @item @code{H}@var{c}@var{t@dots{}} --- set thread
20288 @cindex @code{H} packet
20290 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
20291 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
20292 should be @samp{c} for step and continue operations, @samp{g} for other
20293 operations. The thread designator @var{t@dots{}} may be -1, meaning all
20294 the threads, a thread number, or zero which means pick any thread.
20305 @c 'H': How restrictive (or permissive) is the thread model. If a
20306 @c thread is selected and stopped, are other threads allowed
20307 @c to continue to execute? As I mentioned above, I think the
20308 @c semantics of each command when a thread is selected must be
20309 @c described. For example:
20311 @c 'g': If the stub supports threads and a specific thread is
20312 @c selected, returns the register block from that thread;
20313 @c otherwise returns current registers.
20315 @c 'G' If the stub supports threads and a specific thread is
20316 @c selected, sets the registers of the register block of
20317 @c that thread; otherwise sets current registers.
20319 @item @code{i}@var{addr}@code{,}@var{nnn} --- cycle step @strong{(draft)}
20320 @anchor{cycle step packet}
20321 @cindex @code{i} packet
20323 Step the remote target by a single clock cycle. If @code{,}@var{nnn} is
20324 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
20325 step starting at that address.
20327 @item @code{I} --- signal then cycle step @strong{(reserved)}
20328 @cindex @code{I} packet
20330 @xref{step with signal packet}. @xref{cycle step packet}.
20332 @item @code{j} --- reserved
20334 Reserved for future use.
20336 @item @code{J} --- reserved
20338 Reserved for future use.
20340 @item @code{k} --- kill request
20341 @cindex @code{k} packet
20343 FIXME: @emph{There is no description of how to operate when a specific
20344 thread context has been selected (i.e.@: does 'k' kill only that
20347 @item @code{K} --- reserved
20349 Reserved for future use.
20351 @item @code{l} --- reserved
20353 Reserved for future use.
20355 @item @code{L} --- reserved
20357 Reserved for future use.
20359 @item @code{m}@var{addr}@code{,}@var{length} --- read memory
20360 @cindex @code{m} packet
20362 Read @var{length} bytes of memory starting at address @var{addr}.
20363 Neither @value{GDBN} nor the stub assume that sized memory transfers are
20364 assumed using word aligned accesses. FIXME: @emph{A word aligned memory
20365 transfer mechanism is needed.}
20369 @item @var{XX@dots{}}
20370 @var{XX@dots{}} is mem contents. Can be fewer bytes than requested if able
20371 to read only part of the data. Neither @value{GDBN} nor the stub assume
20372 that sized memory transfers are assumed using word aligned
20373 accesses. FIXME: @emph{A word aligned memory transfer mechanism is
20379 @item @code{M}@var{addr},@var{length}@code{:}@var{XX@dots{}} --- write mem
20380 @cindex @code{M} packet
20382 Write @var{length} bytes of memory starting at address @var{addr}.
20383 @var{XX@dots{}} is the data.
20390 for an error (this includes the case where only part of the data was
20394 @item @code{n} --- reserved
20396 Reserved for future use.
20398 @item @code{N} --- reserved
20400 Reserved for future use.
20402 @item @code{o} --- reserved
20404 Reserved for future use.
20406 @item @code{O} --- reserved
20408 @item @code{p}@var{hex number of register} --- read register packet
20409 @cindex @code{p} packet
20411 @xref{read registers packet}, for a description of how the returned
20412 register value is encoded.
20416 @item @var{XX@dots{}}
20417 the register's value
20421 Indicating an unrecognized @var{query}.
20424 @item @code{P}@var{n@dots{}}@code{=}@var{r@dots{}} --- write register
20425 @anchor{write register packet}
20426 @cindex @code{P} packet
20428 Write register @var{n@dots{}} with value @var{r@dots{}}, which contains two hex
20429 digits for each byte in the register (target byte order).
20439 @item @code{q}@var{query} --- general query
20440 @anchor{general query packet}
20441 @cindex @code{q} packet
20443 Request info about @var{query}. In general @value{GDBN} queries have a
20444 leading upper case letter. Custom vendor queries should use a company
20445 prefix (in lower case) ex: @samp{qfsf.var}. @var{query} may optionally
20446 be followed by a @samp{,} or @samp{;} separated list. Stubs must ensure
20447 that they match the full @var{query} name.
20451 @item @var{XX@dots{}}
20452 Hex encoded data from query. The reply can not be empty.
20456 Indicating an unrecognized @var{query}.
20459 @item @code{Q}@var{var}@code{=}@var{val} --- general set
20460 @cindex @code{Q} packet
20462 Set value of @var{var} to @var{val}.
20464 @xref{general query packet}, for a discussion of naming conventions.
20466 @item @code{r} --- reset @strong{(deprecated)}
20467 @cindex @code{r} packet
20469 Reset the entire system.
20471 @item @code{R}@var{XX} --- remote restart
20472 @cindex @code{R} packet
20474 Restart the program being debugged. @var{XX}, while needed, is ignored.
20475 This packet is only available in extended mode.
20479 @item @emph{no reply}
20480 The @samp{R} packet has no reply.
20483 @item @code{s}@var{addr} --- step
20484 @cindex @code{s} packet
20486 @var{addr} is address to resume. If @var{addr} is omitted, resume at
20490 @xref{Stop Reply Packets}, for the reply specifications.
20492 @item @code{S}@var{sig}@code{;}@var{addr} --- step with signal
20493 @anchor{step with signal packet}
20494 @cindex @code{S} packet
20496 Like @samp{C} but step not continue.
20499 @xref{Stop Reply Packets}, for the reply specifications.
20501 @item @code{t}@var{addr}@code{:}@var{PP}@code{,}@var{MM} --- search
20502 @cindex @code{t} packet
20504 Search backwards starting at address @var{addr} for a match with pattern
20505 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
20506 @var{addr} must be at least 3 digits.
20508 @item @code{T}@var{XX} --- thread alive
20509 @cindex @code{T} packet
20511 Find out if the thread XX is alive.
20516 thread is still alive
20521 @item @code{u} --- reserved
20523 Reserved for future use.
20525 @item @code{U} --- reserved
20527 Reserved for future use.
20529 @item @code{v} --- verbose packet prefix
20531 Packets starting with @code{v} are identified by a multi-letter name,
20532 up to the first @code{;} or @code{?} (or the end of the packet).
20534 @item @code{vCont}[;@var{action}[@code{:}@var{tid}]]... --- extended resume
20535 @cindex @code{vCont} packet
20537 Resume the inferior. Different actions may be specified for each thread.
20538 If an action is specified with no @var{tid}, then it is applied to any
20539 threads that don't have a specific action specified; if no default action is
20540 specified then other threads should remain stopped. Specifying multiple
20541 default actions is an error; specifying no actions is also an error.
20542 Thread IDs are specified in hexadecimal. Currently supported actions are:
20548 Continue with signal @var{sig}. @var{sig} should be two hex digits.
20552 Step with signal @var{sig}. @var{sig} should be two hex digits.
20555 The optional @var{addr} argument normally associated with these packets is
20556 not supported in @code{vCont}.
20559 @xref{Stop Reply Packets}, for the reply specifications.
20561 @item @code{vCont?} --- extended resume query
20562 @cindex @code{vCont?} packet
20564 Query support for the @code{vCont} packet.
20568 @item @code{vCont}[;@var{action}]...
20569 The @code{vCont} packet is supported. Each @var{action} is a supported
20570 command in the @code{vCont} packet.
20572 The @code{vCont} packet is not supported.
20575 @item @code{V} --- reserved
20577 Reserved for future use.
20579 @item @code{w} --- reserved
20581 Reserved for future use.
20583 @item @code{W} --- reserved
20585 Reserved for future use.
20587 @item @code{x} --- reserved
20589 Reserved for future use.
20591 @item @code{X}@var{addr}@code{,}@var{length}@var{:}@var{XX@dots{}} --- write mem (binary)
20592 @cindex @code{X} packet
20594 @var{addr} is address, @var{length} is number of bytes, @var{XX@dots{}}
20595 is binary data. The characters @code{$}, @code{#}, and @code{0x7d} are
20596 escaped using @code{0x7d}, and then XORed with @code{0x20}.
20597 For example, @code{0x7d} would be transmitted as @code{0x7d 0x5d}.
20607 @item @code{y} --- reserved
20609 Reserved for future use.
20611 @item @code{Y} reserved
20613 Reserved for future use.
20615 @item @code{z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- remove breakpoint or watchpoint @strong{(draft)}
20616 @itemx @code{Z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- insert breakpoint or watchpoint @strong{(draft)}
20617 @anchor{insert breakpoint or watchpoint packet}
20618 @cindex @code{z} packet
20619 @cindex @code{Z} packets
20621 Insert (@code{Z}) or remove (@code{z}) a @var{type} breakpoint or
20622 watchpoint starting at address @var{address} and covering the next
20623 @var{length} bytes.
20625 Each breakpoint and watchpoint packet @var{type} is documented
20628 @emph{Implementation notes: A remote target shall return an empty string
20629 for an unrecognized breakpoint or watchpoint packet @var{type}. A
20630 remote target shall support either both or neither of a given
20631 @code{Z}@var{type}@dots{} and @code{z}@var{type}@dots{} packet pair. To
20632 avoid potential problems with duplicate packets, the operations should
20633 be implemented in an idempotent way.}
20635 @item @code{z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- remove memory breakpoint @strong{(draft)}
20636 @item @code{Z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- insert memory breakpoint @strong{(draft)}
20637 @cindex @code{z0} packet
20638 @cindex @code{Z0} packet
20640 Insert (@code{Z0}) or remove (@code{z0}) a memory breakpoint at address
20641 @code{addr} of size @code{length}.
20643 A memory breakpoint is implemented by replacing the instruction at
20644 @var{addr} with a software breakpoint or trap instruction. The
20645 @code{length} is used by targets that indicates the size of the
20646 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
20647 @sc{mips} can insert either a 2 or 4 byte breakpoint).
20649 @emph{Implementation note: It is possible for a target to copy or move
20650 code that contains memory breakpoints (e.g., when implementing
20651 overlays). The behavior of this packet, in the presence of such a
20652 target, is not defined.}
20664 @item @code{z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- remove hardware breakpoint @strong{(draft)}
20665 @item @code{Z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- insert hardware breakpoint @strong{(draft)}
20666 @cindex @code{z1} packet
20667 @cindex @code{Z1} packet
20669 Insert (@code{Z1}) or remove (@code{z1}) a hardware breakpoint at
20670 address @code{addr} of size @code{length}.
20672 A hardware breakpoint is implemented using a mechanism that is not
20673 dependant on being able to modify the target's memory.
20675 @emph{Implementation note: A hardware breakpoint is not affected by code
20688 @item @code{z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- remove write watchpoint @strong{(draft)}
20689 @item @code{Z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- insert write watchpoint @strong{(draft)}
20690 @cindex @code{z2} packet
20691 @cindex @code{Z2} packet
20693 Insert (@code{Z2}) or remove (@code{z2}) a write watchpoint.
20705 @item @code{z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- remove read watchpoint @strong{(draft)}
20706 @item @code{Z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- insert read watchpoint @strong{(draft)}
20707 @cindex @code{z3} packet
20708 @cindex @code{Z3} packet
20710 Insert (@code{Z3}) or remove (@code{z3}) a read watchpoint.
20722 @item @code{z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- remove access watchpoint @strong{(draft)}
20723 @item @code{Z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- insert access watchpoint @strong{(draft)}
20724 @cindex @code{z4} packet
20725 @cindex @code{Z4} packet
20727 Insert (@code{Z4}) or remove (@code{z4}) an access watchpoint.
20741 @node Stop Reply Packets
20742 @section Stop Reply Packets
20743 @cindex stop reply packets
20745 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
20746 receive any of the below as a reply. In the case of the @samp{C},
20747 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
20748 when the target halts. In the below the exact meaning of @samp{signal
20749 number} is poorly defined. In general one of the UNIX signal numbering
20750 conventions is used.
20755 @var{AA} is the signal number
20757 @item @code{T}@var{AA}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}
20758 @cindex @code{T} packet reply
20760 @var{AA} = two hex digit signal number; @var{n...} = register number
20761 (hex), @var{r...} = target byte ordered register contents, size defined
20762 by @code{DEPRECATED_REGISTER_RAW_SIZE}; @var{n...} = @samp{thread},
20763 @var{r...} = thread process ID, this is a hex integer; @var{n...} =
20764 (@samp{watch} | @samp{rwatch} | @samp{awatch}, @var{r...} = data
20765 address, this is a hex integer; @var{n...} = other string not starting
20766 with valid hex digit. @value{GDBN} should ignore this @var{n...},
20767 @var{r...} pair and go on to the next. This way we can extend the
20772 The process exited, and @var{AA} is the exit status. This is only
20773 applicable to certain targets.
20777 The process terminated with signal @var{AA}.
20779 @item O@var{XX@dots{}}
20781 @var{XX@dots{}} is hex encoding of @sc{ascii} data. This can happen at
20782 any time while the program is running and the debugger should continue
20783 to wait for @samp{W}, @samp{T}, etc.
20785 @item F@var{call-id}@code{,}@var{parameter@dots{}}
20787 @var{call-id} is the identifier which says which host system call should
20788 be called. This is just the name of the function. Translation into the
20789 correct system call is only applicable as it's defined in @value{GDBN}.
20790 @xref{File-I/O remote protocol extension}, for a list of implemented
20793 @var{parameter@dots{}} is a list of parameters as defined for this very
20796 The target replies with this packet when it expects @value{GDBN} to call
20797 a host system call on behalf of the target. @value{GDBN} replies with
20798 an appropriate @code{F} packet and keeps up waiting for the next reply
20799 packet from the target. The latest @samp{C}, @samp{c}, @samp{S} or
20800 @samp{s} action is expected to be continued.
20801 @xref{File-I/O remote protocol extension}, for more details.
20805 @node General Query Packets
20806 @section General Query Packets
20808 The following set and query packets have already been defined.
20812 @item @code{q}@code{C} --- current thread
20814 Return the current thread id.
20818 @item @code{QC}@var{pid}
20819 Where @var{pid} is a HEX encoded 16 bit process id.
20821 Any other reply implies the old pid.
20824 @item @code{q}@code{fThreadInfo} -- all thread ids
20826 @code{q}@code{sThreadInfo}
20828 Obtain a list of active thread ids from the target (OS). Since there
20829 may be too many active threads to fit into one reply packet, this query
20830 works iteratively: it may require more than one query/reply sequence to
20831 obtain the entire list of threads. The first query of the sequence will
20832 be the @code{qf}@code{ThreadInfo} query; subsequent queries in the
20833 sequence will be the @code{qs}@code{ThreadInfo} query.
20835 NOTE: replaces the @code{qL} query (see below).
20839 @item @code{m}@var{id}
20841 @item @code{m}@var{id},@var{id}@dots{}
20842 a comma-separated list of thread ids
20844 (lower case 'el') denotes end of list.
20847 In response to each query, the target will reply with a list of one or
20848 more thread ids, in big-endian hex, separated by commas. @value{GDBN}
20849 will respond to each reply with a request for more thread ids (using the
20850 @code{qs} form of the query), until the target responds with @code{l}
20851 (lower-case el, for @code{'last'}).
20853 @item @code{q}@code{ThreadExtraInfo}@code{,}@var{id} --- extra thread info
20855 Where @var{id} is a thread-id in big-endian hex. Obtain a printable
20856 string description of a thread's attributes from the target OS. This
20857 string may contain anything that the target OS thinks is interesting for
20858 @value{GDBN} to tell the user about the thread. The string is displayed
20859 in @value{GDBN}'s @samp{info threads} display. Some examples of
20860 possible thread extra info strings are ``Runnable'', or ``Blocked on
20865 @item @var{XX@dots{}}
20866 Where @var{XX@dots{}} is a hex encoding of @sc{ascii} data, comprising
20867 the printable string containing the extra information about the thread's
20871 @item @code{q}@code{L}@var{startflag}@var{threadcount}@var{nextthread} --- query @var{LIST} or @var{threadLIST} @strong{(deprecated)}
20873 Obtain thread information from RTOS. Where: @var{startflag} (one hex
20874 digit) is one to indicate the first query and zero to indicate a
20875 subsequent query; @var{threadcount} (two hex digits) is the maximum
20876 number of threads the response packet can contain; and @var{nextthread}
20877 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
20878 returned in the response as @var{argthread}.
20880 NOTE: this query is replaced by the @code{q}@code{fThreadInfo} query
20885 @item @code{q}@code{M}@var{count}@var{done}@var{argthread}@var{thread@dots{}}
20886 Where: @var{count} (two hex digits) is the number of threads being
20887 returned; @var{done} (one hex digit) is zero to indicate more threads
20888 and one indicates no further threads; @var{argthreadid} (eight hex
20889 digits) is @var{nextthread} from the request packet; @var{thread@dots{}}
20890 is a sequence of thread IDs from the target. @var{threadid} (eight hex
20891 digits). See @code{remote.c:parse_threadlist_response()}.
20894 @item @code{q}@code{CRC:}@var{addr}@code{,}@var{length} --- compute CRC of memory block
20898 @item @code{E}@var{NN}
20899 An error (such as memory fault)
20900 @item @code{C}@var{CRC32}
20901 A 32 bit cyclic redundancy check of the specified memory region.
20904 @item @code{q}@code{Offsets} --- query sect offs
20906 Get section offsets that the target used when re-locating the downloaded
20907 image. @emph{Note: while a @code{Bss} offset is included in the
20908 response, @value{GDBN} ignores this and instead applies the @code{Data}
20909 offset to the @code{Bss} section.}
20913 @item @code{Text=}@var{xxx}@code{;Data=}@var{yyy}@code{;Bss=}@var{zzz}
20916 @item @code{q}@code{P}@var{mode}@var{threadid} --- thread info request
20918 Returns information on @var{threadid}. Where: @var{mode} is a hex
20919 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
20926 See @code{remote.c:remote_unpack_thread_info_response()}.
20928 @item @code{q}@code{Rcmd,}@var{command} --- remote command
20930 @var{command} (hex encoded) is passed to the local interpreter for
20931 execution. Invalid commands should be reported using the output string.
20932 Before the final result packet, the target may also respond with a
20933 number of intermediate @code{O}@var{output} console output packets.
20934 @emph{Implementors should note that providing access to a stubs's
20935 interpreter may have security implications}.
20940 A command response with no output.
20942 A command response with the hex encoded output string @var{OUTPUT}.
20943 @item @code{E}@var{NN}
20944 Indicate a badly formed request.
20946 When @samp{q}@samp{Rcmd} is not recognized.
20949 @item @code{qSymbol::} --- symbol lookup
20951 Notify the target that @value{GDBN} is prepared to serve symbol lookup
20952 requests. Accept requests from the target for the values of symbols.
20957 The target does not need to look up any (more) symbols.
20958 @item @code{qSymbol:}@var{sym_name}
20959 The target requests the value of symbol @var{sym_name} (hex encoded).
20960 @value{GDBN} may provide the value by using the
20961 @code{qSymbol:}@var{sym_value}:@var{sym_name} message, described below.
20964 @item @code{qSymbol:}@var{sym_value}:@var{sym_name} --- symbol value
20966 Set the value of @var{sym_name} to @var{sym_value}.
20968 @var{sym_name} (hex encoded) is the name of a symbol whose value the
20969 target has previously requested.
20971 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
20972 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
20978 The target does not need to look up any (more) symbols.
20979 @item @code{qSymbol:}@var{sym_name}
20980 The target requests the value of a new symbol @var{sym_name} (hex
20981 encoded). @value{GDBN} will continue to supply the values of symbols
20982 (if available), until the target ceases to request them.
20985 @item @code{qPart}:@var{object}:@code{read}:@var{annex}:@var{offset},@var{length} --- read special data
20987 Read uninterpreted bytes from the target's special data area
20988 identified by the keyword @code{object}.
20989 Request @var{length} bytes starting at @var{offset} bytes into the data.
20990 The content and encoding of @var{annex} is specific to the object;
20991 it can supply additional details about what data to access.
20993 Here are the specific requests of this form defined so far.
20994 All @samp{@code{qPart}:@var{object}:@code{read}:@dots{}}
20995 requests use the same reply formats, listed below.
20998 @item @code{qPart}:@code{auxv}:@code{read}::@var{offset},@var{length}
20999 Access the target's @dfn{auxiliary vector}. @xref{Auxiliary Vector}.
21000 Note @var{annex} must be empty.
21006 The @var{offset} in the request is at the end of the data.
21007 There is no more data to be read.
21009 @item @var{XX@dots{}}
21010 Hex encoded data bytes read.
21011 This may be fewer bytes than the @var{length} in the request.
21014 The request was malformed, or @var{annex} was invalid.
21016 @item @code{E}@var{nn}
21017 The offset was invalid, or there was an error encountered reading the data.
21018 @var{nn} is a hex-encoded @code{errno} value.
21020 @item @code{""} (empty)
21021 An empty reply indicates the @var{object} or @var{annex} string was not
21022 recognized by the stub.
21025 @item @code{qPart}:@var{object}:@code{write}:@var{annex}:@var{offset}:@var{data@dots{}}
21027 Write uninterpreted bytes into the target's special data area
21028 identified by the keyword @code{object},
21029 starting at @var{offset} bytes into the data.
21030 @var{data@dots{}} is the hex-encoded data to be written.
21031 The content and encoding of @var{annex} is specific to the object;
21032 it can supply additional details about what data to access.
21034 No requests of this form are presently in use. This specification
21035 serves as a placeholder to document the common format that new
21036 specific request specifications ought to use.
21041 @var{nn} (hex encoded) is the number of bytes written.
21042 This may be fewer bytes than supplied in the request.
21045 The request was malformed, or @var{annex} was invalid.
21047 @item @code{E}@var{nn}
21048 The offset was invalid, or there was an error encountered writing the data.
21049 @var{nn} is a hex-encoded @code{errno} value.
21051 @item @code{""} (empty)
21052 An empty reply indicates the @var{object} or @var{annex} string was not
21053 recognized by the stub, or that the object does not support writing.
21056 @item @code{qPart}:@var{object}:@var{operation}:@dots{}
21057 Requests of this form may be added in the future. When a stub does
21058 not recognize the @var{object} keyword, or its support for
21059 @var{object} does not recognize the @var{operation} keyword,
21060 the stub must respond with an empty packet.
21063 @node Register Packet Format
21064 @section Register Packet Format
21066 The following @samp{g}/@samp{G} packets have previously been defined.
21067 In the below, some thirty-two bit registers are transferred as
21068 sixty-four bits. Those registers should be zero/sign extended (which?)
21069 to fill the space allocated. Register bytes are transfered in target
21070 byte order. The two nibbles within a register byte are transfered
21071 most-significant - least-significant.
21077 All registers are transfered as thirty-two bit quantities in the order:
21078 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
21079 registers; fsr; fir; fp.
21083 All registers are transfered as sixty-four bit quantities (including
21084 thirty-two bit registers such as @code{sr}). The ordering is the same
21092 Example sequence of a target being re-started. Notice how the restart
21093 does not get any direct output:
21098 @emph{target restarts}
21101 <- @code{T001:1234123412341234}
21105 Example sequence of a target being stepped by a single instruction:
21108 -> @code{G1445@dots{}}
21113 <- @code{T001:1234123412341234}
21117 <- @code{1455@dots{}}
21121 @node File-I/O remote protocol extension
21122 @section File-I/O remote protocol extension
21123 @cindex File-I/O remote protocol extension
21126 * File-I/O Overview::
21127 * Protocol basics::
21128 * The F request packet::
21129 * The F reply packet::
21130 * Memory transfer::
21131 * The Ctrl-C message::
21133 * The isatty call::
21134 * The system call::
21135 * List of supported calls::
21136 * Protocol specific representation of datatypes::
21138 * File-I/O Examples::
21141 @node File-I/O Overview
21142 @subsection File-I/O Overview
21143 @cindex file-i/o overview
21145 The File I/O remote protocol extension (short: File-I/O) allows the
21146 target to use the hosts file system and console I/O when calling various
21147 system calls. System calls on the target system are translated into a
21148 remote protocol packet to the host system which then performs the needed
21149 actions and returns with an adequate response packet to the target system.
21150 This simulates file system operations even on targets that lack file systems.
21152 The protocol is defined host- and target-system independent. It uses
21153 it's own independent representation of datatypes and values. Both,
21154 @value{GDBN} and the target's @value{GDBN} stub are responsible for
21155 translating the system dependent values into the unified protocol values
21156 when data is transmitted.
21158 The communication is synchronous. A system call is possible only
21159 when GDB is waiting for the @samp{C}, @samp{c}, @samp{S} or @samp{s}
21160 packets. While @value{GDBN} handles the request for a system call,
21161 the target is stopped to allow deterministic access to the target's
21162 memory. Therefore File-I/O is not interuptible by target signals. It
21163 is possible to interrupt File-I/O by a user interrupt (Ctrl-C), though.
21165 The target's request to perform a host system call does not finish
21166 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
21167 after finishing the system call, the target returns to continuing the
21168 previous activity (continue, step). No additional continue or step
21169 request from @value{GDBN} is required.
21172 (@value{GDBP}) continue
21173 <- target requests 'system call X'
21174 target is stopped, @value{GDBN} executes system call
21175 -> GDB returns result
21176 ... target continues, GDB returns to wait for the target
21177 <- target hits breakpoint and sends a Txx packet
21180 The protocol is only used for files on the host file system and
21181 for I/O on the console. Character or block special devices, pipes,
21182 named pipes or sockets or any other communication method on the host
21183 system are not supported by this protocol.
21185 @node Protocol basics
21186 @subsection Protocol basics
21187 @cindex protocol basics, file-i/o
21189 The File-I/O protocol uses the @code{F} packet, as request as well
21190 as as reply packet. Since a File-I/O system call can only occur when
21191 @value{GDBN} is waiting for the continuing or stepping target, the
21192 File-I/O request is a reply that @value{GDBN} has to expect as a result
21193 of a former @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
21194 This @code{F} packet contains all information needed to allow @value{GDBN}
21195 to call the appropriate host system call:
21199 A unique identifier for the requested system call.
21202 All parameters to the system call. Pointers are given as addresses
21203 in the target memory address space. Pointers to strings are given as
21204 pointer/length pair. Numerical values are given as they are.
21205 Numerical control values are given in a protocol specific representation.
21209 At that point @value{GDBN} has to perform the following actions.
21213 If parameter pointer values are given, which point to data needed as input
21214 to a system call, @value{GDBN} requests this data from the target with a
21215 standard @code{m} packet request. This additional communication has to be
21216 expected by the target implementation and is handled as any other @code{m}
21220 @value{GDBN} translates all value from protocol representation to host
21221 representation as needed. Datatypes are coerced into the host types.
21224 @value{GDBN} calls the system call
21227 It then coerces datatypes back to protocol representation.
21230 If pointer parameters in the request packet point to buffer space in which
21231 a system call is expected to copy data to, the data is transmitted to the
21232 target using a @code{M} or @code{X} packet. This packet has to be expected
21233 by the target implementation and is handled as any other @code{M} or @code{X}
21238 Eventually @value{GDBN} replies with another @code{F} packet which contains all
21239 necessary information for the target to continue. This at least contains
21246 @code{errno}, if has been changed by the system call.
21253 After having done the needed type and value coercion, the target continues
21254 the latest continue or step action.
21256 @node The F request packet
21257 @subsection The @code{F} request packet
21258 @cindex file-i/o request packet
21259 @cindex @code{F} request packet
21261 The @code{F} request packet has the following format:
21266 @code{F}@var{call-id}@code{,}@var{parameter@dots{}}
21269 @var{call-id} is the identifier to indicate the host system call to be called.
21270 This is just the name of the function.
21272 @var{parameter@dots{}} are the parameters to the system call.
21276 Parameters are hexadecimal integer values, either the real values in case
21277 of scalar datatypes, as pointers to target buffer space in case of compound
21278 datatypes and unspecified memory areas or as pointer/length pairs in case
21279 of string parameters. These are appended to the call-id, each separated
21280 from its predecessor by a comma. All values are transmitted in ASCII
21281 string representation, pointer/length pairs separated by a slash.
21283 @node The F reply packet
21284 @subsection The @code{F} reply packet
21285 @cindex file-i/o reply packet
21286 @cindex @code{F} reply packet
21288 The @code{F} reply packet has the following format:
21293 @code{F}@var{retcode}@code{,}@var{errno}@code{,}@var{Ctrl-C flag}@code{;}@var{call specific attachment}
21296 @var{retcode} is the return code of the system call as hexadecimal value.
21298 @var{errno} is the errno set by the call, in protocol specific representation.
21299 This parameter can be omitted if the call was successful.
21301 @var{Ctrl-C flag} is only send if the user requested a break. In this
21302 case, @var{errno} must be send as well, even if the call was successful.
21303 The @var{Ctrl-C flag} itself consists of the character 'C':
21310 or, if the call was interupted before the host call has been performed:
21317 assuming 4 is the protocol specific representation of @code{EINTR}.
21321 @node Memory transfer
21322 @subsection Memory transfer
21323 @cindex memory transfer, in file-i/o protocol
21325 Structured data which is transferred using a memory read or write as e.g.@:
21326 a @code{struct stat} is expected to be in a protocol specific format with
21327 all scalar multibyte datatypes being big endian. This should be done by
21328 the target before the @code{F} packet is sent resp.@: by @value{GDBN} before
21329 it transfers memory to the target. Transferred pointers to structured
21330 data should point to the already coerced data at any time.
21332 @node The Ctrl-C message
21333 @subsection The Ctrl-C message
21334 @cindex ctrl-c message, in file-i/o protocol
21336 A special case is, if the @var{Ctrl-C flag} is set in the @value{GDBN}
21337 reply packet. In this case the target should behave, as if it had
21338 gotten a break message. The meaning for the target is ``system call
21339 interupted by @code{SIGINT}''. Consequentially, the target should actually stop
21340 (as with a break message) and return to @value{GDBN} with a @code{T02}
21341 packet. In this case, it's important for the target to know, in which
21342 state the system call was interrupted. Since this action is by design
21343 not an atomic operation, we have to differ between two cases:
21347 The system call hasn't been performed on the host yet.
21350 The system call on the host has been finished.
21354 These two states can be distinguished by the target by the value of the
21355 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
21356 call hasn't been performed. This is equivalent to the @code{EINTR} handling
21357 on POSIX systems. In any other case, the target may presume that the
21358 system call has been finished --- successful or not --- and should behave
21359 as if the break message arrived right after the system call.
21361 @value{GDBN} must behave reliable. If the system call has not been called
21362 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
21363 @code{errno} in the packet. If the system call on the host has been finished
21364 before the user requests a break, the full action must be finshed by
21365 @value{GDBN}. This requires sending @code{M} or @code{X} packets as they fit.
21366 The @code{F} packet may only be send when either nothing has happened
21367 or the full action has been completed.
21370 @subsection Console I/O
21371 @cindex console i/o as part of file-i/o
21373 By default and if not explicitely closed by the target system, the file
21374 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
21375 on the @value{GDBN} console is handled as any other file output operation
21376 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
21377 by @value{GDBN} so that after the target read request from file descriptor
21378 0 all following typing is buffered until either one of the following
21383 The user presses @kbd{Ctrl-C}. The behaviour is as explained above, the
21385 system call is treated as finished.
21388 The user presses @kbd{Enter}. This is treated as end of input with a trailing
21392 The user presses @kbd{Ctrl-D}. This is treated as end of input. No trailing
21393 character, especially no Ctrl-D is appended to the input.
21397 If the user has typed more characters as fit in the buffer given to
21398 the read call, the trailing characters are buffered in @value{GDBN} until
21399 either another @code{read(0, @dots{})} is requested by the target or debugging
21400 is stopped on users request.
21402 @node The isatty call
21403 @subsection The isatty(3) call
21404 @cindex isatty call, file-i/o protocol
21406 A special case in this protocol is the library call @code{isatty} which
21407 is implemented as it's own call inside of this protocol. It returns
21408 1 to the target if the file descriptor given as parameter is attached
21409 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
21410 would require implementing @code{ioctl} and would be more complex than
21413 @node The system call
21414 @subsection The system(3) call
21415 @cindex system call, file-i/o protocol
21417 The other special case in this protocol is the @code{system} call which
21418 is implemented as it's own call, too. @value{GDBN} is taking over the full
21419 task of calling the necessary host calls to perform the @code{system}
21420 call. The return value of @code{system} is simplified before it's returned
21421 to the target. Basically, the only signal transmitted back is @code{EINTR}
21422 in case the user pressed @kbd{Ctrl-C}. Otherwise the return value consists
21423 entirely of the exit status of the called command.
21425 Due to security concerns, the @code{system} call is refused to be called
21426 by @value{GDBN} by default. The user has to allow this call explicitly by
21430 @kindex set remote system-call-allowed 1
21431 @item @code{set remote system-call-allowed 1}
21434 Disabling the @code{system} call is done by
21437 @kindex set remote system-call-allowed 0
21438 @item @code{set remote system-call-allowed 0}
21441 The current setting is shown by typing
21444 @kindex show remote system-call-allowed
21445 @item @code{show remote system-call-allowed}
21448 @node List of supported calls
21449 @subsection List of supported calls
21450 @cindex list of supported file-i/o calls
21467 @unnumberedsubsubsec open
21468 @cindex open, file-i/o system call
21472 int open(const char *pathname, int flags);
21473 int open(const char *pathname, int flags, mode_t mode);
21476 Fopen,pathptr/len,flags,mode
21480 @code{flags} is the bitwise or of the following values:
21484 If the file does not exist it will be created. The host
21485 rules apply as far as file ownership and time stamps
21489 When used with O_CREAT, if the file already exists it is
21490 an error and open() fails.
21493 If the file already exists and the open mode allows
21494 writing (O_RDWR or O_WRONLY is given) it will be
21495 truncated to length 0.
21498 The file is opened in append mode.
21501 The file is opened for reading only.
21504 The file is opened for writing only.
21507 The file is opened for reading and writing.
21510 Each other bit is silently ignored.
21515 @code{mode} is the bitwise or of the following values:
21519 User has read permission.
21522 User has write permission.
21525 Group has read permission.
21528 Group has write permission.
21531 Others have read permission.
21534 Others have write permission.
21537 Each other bit is silently ignored.
21542 @exdent Return value:
21543 open returns the new file descriptor or -1 if an error
21551 pathname already exists and O_CREAT and O_EXCL were used.
21554 pathname refers to a directory.
21557 The requested access is not allowed.
21560 pathname was too long.
21563 A directory component in pathname does not exist.
21566 pathname refers to a device, pipe, named pipe or socket.
21569 pathname refers to a file on a read-only filesystem and
21570 write access was requested.
21573 pathname is an invalid pointer value.
21576 No space on device to create the file.
21579 The process already has the maximum number of files open.
21582 The limit on the total number of files open on the system
21586 The call was interrupted by the user.
21590 @unnumberedsubsubsec close
21591 @cindex close, file-i/o system call
21600 @exdent Return value:
21601 close returns zero on success, or -1 if an error occurred.
21608 fd isn't a valid open file descriptor.
21611 The call was interrupted by the user.
21615 @unnumberedsubsubsec read
21616 @cindex read, file-i/o system call
21620 int read(int fd, void *buf, unsigned int count);
21623 Fread,fd,bufptr,count
21625 @exdent Return value:
21626 On success, the number of bytes read is returned.
21627 Zero indicates end of file. If count is zero, read
21628 returns zero as well. On error, -1 is returned.
21635 fd is not a valid file descriptor or is not open for
21639 buf is an invalid pointer value.
21642 The call was interrupted by the user.
21646 @unnumberedsubsubsec write
21647 @cindex write, file-i/o system call
21651 int write(int fd, const void *buf, unsigned int count);
21654 Fwrite,fd,bufptr,count
21656 @exdent Return value:
21657 On success, the number of bytes written are returned.
21658 Zero indicates nothing was written. On error, -1
21666 fd is not a valid file descriptor or is not open for
21670 buf is an invalid pointer value.
21673 An attempt was made to write a file that exceeds the
21674 host specific maximum file size allowed.
21677 No space on device to write the data.
21680 The call was interrupted by the user.
21684 @unnumberedsubsubsec lseek
21685 @cindex lseek, file-i/o system call
21689 long lseek (int fd, long offset, int flag);
21692 Flseek,fd,offset,flag
21695 @code{flag} is one of:
21699 The offset is set to offset bytes.
21702 The offset is set to its current location plus offset
21706 The offset is set to the size of the file plus offset
21711 @exdent Return value:
21712 On success, the resulting unsigned offset in bytes from
21713 the beginning of the file is returned. Otherwise, a
21714 value of -1 is returned.
21721 fd is not a valid open file descriptor.
21724 fd is associated with the @value{GDBN} console.
21727 flag is not a proper value.
21730 The call was interrupted by the user.
21734 @unnumberedsubsubsec rename
21735 @cindex rename, file-i/o system call
21739 int rename(const char *oldpath, const char *newpath);
21742 Frename,oldpathptr/len,newpathptr/len
21744 @exdent Return value:
21745 On success, zero is returned. On error, -1 is returned.
21752 newpath is an existing directory, but oldpath is not a
21756 newpath is a non-empty directory.
21759 oldpath or newpath is a directory that is in use by some
21763 An attempt was made to make a directory a subdirectory
21767 A component used as a directory in oldpath or new
21768 path is not a directory. Or oldpath is a directory
21769 and newpath exists but is not a directory.
21772 oldpathptr or newpathptr are invalid pointer values.
21775 No access to the file or the path of the file.
21779 oldpath or newpath was too long.
21782 A directory component in oldpath or newpath does not exist.
21785 The file is on a read-only filesystem.
21788 The device containing the file has no room for the new
21792 The call was interrupted by the user.
21796 @unnumberedsubsubsec unlink
21797 @cindex unlink, file-i/o system call
21801 int unlink(const char *pathname);
21804 Funlink,pathnameptr/len
21806 @exdent Return value:
21807 On success, zero is returned. On error, -1 is returned.
21814 No access to the file or the path of the file.
21817 The system does not allow unlinking of directories.
21820 The file pathname cannot be unlinked because it's
21821 being used by another process.
21824 pathnameptr is an invalid pointer value.
21827 pathname was too long.
21830 A directory component in pathname does not exist.
21833 A component of the path is not a directory.
21836 The file is on a read-only filesystem.
21839 The call was interrupted by the user.
21843 @unnumberedsubsubsec stat/fstat
21844 @cindex fstat, file-i/o system call
21845 @cindex stat, file-i/o system call
21849 int stat(const char *pathname, struct stat *buf);
21850 int fstat(int fd, struct stat *buf);
21853 Fstat,pathnameptr/len,bufptr
21856 @exdent Return value:
21857 On success, zero is returned. On error, -1 is returned.
21864 fd is not a valid open file.
21867 A directory component in pathname does not exist or the
21868 path is an empty string.
21871 A component of the path is not a directory.
21874 pathnameptr is an invalid pointer value.
21877 No access to the file or the path of the file.
21880 pathname was too long.
21883 The call was interrupted by the user.
21887 @unnumberedsubsubsec gettimeofday
21888 @cindex gettimeofday, file-i/o system call
21892 int gettimeofday(struct timeval *tv, void *tz);
21895 Fgettimeofday,tvptr,tzptr
21897 @exdent Return value:
21898 On success, 0 is returned, -1 otherwise.
21905 tz is a non-NULL pointer.
21908 tvptr and/or tzptr is an invalid pointer value.
21912 @unnumberedsubsubsec isatty
21913 @cindex isatty, file-i/o system call
21917 int isatty(int fd);
21922 @exdent Return value:
21923 Returns 1 if fd refers to the @value{GDBN} console, 0 otherwise.
21930 The call was interrupted by the user.
21934 @unnumberedsubsubsec system
21935 @cindex system, file-i/o system call
21939 int system(const char *command);
21942 Fsystem,commandptr/len
21944 @exdent Return value:
21945 The value returned is -1 on error and the return status
21946 of the command otherwise. Only the exit status of the
21947 command is returned, which is extracted from the hosts
21948 system return value by calling WEXITSTATUS(retval).
21949 In case /bin/sh could not be executed, 127 is returned.
21956 The call was interrupted by the user.
21959 @node Protocol specific representation of datatypes
21960 @subsection Protocol specific representation of datatypes
21961 @cindex protocol specific representation of datatypes, in file-i/o protocol
21964 * Integral datatypes::
21970 @node Integral datatypes
21971 @unnumberedsubsubsec Integral datatypes
21972 @cindex integral datatypes, in file-i/o protocol
21974 The integral datatypes used in the system calls are
21977 int@r{,} unsigned int@r{,} long@r{,} unsigned long@r{,} mode_t @r{and} time_t
21980 @code{Int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
21981 implemented as 32 bit values in this protocol.
21983 @code{Long} and @code{unsigned long} are implemented as 64 bit types.
21985 @xref{Limits}, for corresponding MIN and MAX values (similar to those
21986 in @file{limits.h}) to allow range checking on host and target.
21988 @code{time_t} datatypes are defined as seconds since the Epoch.
21990 All integral datatypes transferred as part of a memory read or write of a
21991 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
21994 @node Pointer values
21995 @unnumberedsubsubsec Pointer values
21996 @cindex pointer values, in file-i/o protocol
21998 Pointers to target data are transmitted as they are. An exception
21999 is made for pointers to buffers for which the length isn't
22000 transmitted as part of the function call, namely strings. Strings
22001 are transmitted as a pointer/length pair, both as hex values, e.g.@:
22008 which is a pointer to data of length 18 bytes at position 0x1aaf.
22009 The length is defined as the full string length in bytes, including
22010 the trailing null byte. Example:
22013 ``hello, world'' at address 0x123456
22024 @unnumberedsubsubsec struct stat
22025 @cindex struct stat, in file-i/o protocol
22027 The buffer of type struct stat used by the target and @value{GDBN} is defined
22032 unsigned int st_dev; /* device */
22033 unsigned int st_ino; /* inode */
22034 mode_t st_mode; /* protection */
22035 unsigned int st_nlink; /* number of hard links */
22036 unsigned int st_uid; /* user ID of owner */
22037 unsigned int st_gid; /* group ID of owner */
22038 unsigned int st_rdev; /* device type (if inode device) */
22039 unsigned long st_size; /* total size, in bytes */
22040 unsigned long st_blksize; /* blocksize for filesystem I/O */
22041 unsigned long st_blocks; /* number of blocks allocated */
22042 time_t st_atime; /* time of last access */
22043 time_t st_mtime; /* time of last modification */
22044 time_t st_ctime; /* time of last change */
22048 The integral datatypes are conforming to the definitions given in the
22049 approriate section (see @ref{Integral datatypes}, for details) so this
22050 structure is of size 64 bytes.
22052 The values of several fields have a restricted meaning and/or
22059 st_ino: No valid meaning for the target. Transmitted unchanged.
22061 st_mode: Valid mode bits are described in Appendix C. Any other
22062 bits have currently no meaning for the target.
22064 st_uid: No valid meaning for the target. Transmitted unchanged.
22066 st_gid: No valid meaning for the target. Transmitted unchanged.
22068 st_rdev: No valid meaning for the target. Transmitted unchanged.
22070 st_atime, st_mtime, st_ctime:
22071 These values have a host and file system dependent
22072 accuracy. Especially on Windows hosts the file systems
22073 don't support exact timing values.
22076 The target gets a struct stat of the above representation and is
22077 responsible to coerce it to the target representation before
22080 Note that due to size differences between the host and target
22081 representation of stat members, these members could eventually
22082 get truncated on the target.
22084 @node struct timeval
22085 @unnumberedsubsubsec struct timeval
22086 @cindex struct timeval, in file-i/o protocol
22088 The buffer of type struct timeval used by the target and @value{GDBN}
22089 is defined as follows:
22093 time_t tv_sec; /* second */
22094 long tv_usec; /* microsecond */
22098 The integral datatypes are conforming to the definitions given in the
22099 approriate section (see @ref{Integral datatypes}, for details) so this
22100 structure is of size 8 bytes.
22103 @subsection Constants
22104 @cindex constants, in file-i/o protocol
22106 The following values are used for the constants inside of the
22107 protocol. @value{GDBN} and target are resposible to translate these
22108 values before and after the call as needed.
22119 @unnumberedsubsubsec Open flags
22120 @cindex open flags, in file-i/o protocol
22122 All values are given in hexadecimal representation.
22134 @node mode_t values
22135 @unnumberedsubsubsec mode_t values
22136 @cindex mode_t values, in file-i/o protocol
22138 All values are given in octal representation.
22155 @unnumberedsubsubsec Errno values
22156 @cindex errno values, in file-i/o protocol
22158 All values are given in decimal representation.
22183 EUNKNOWN is used as a fallback error value if a host system returns
22184 any error value not in the list of supported error numbers.
22187 @unnumberedsubsubsec Lseek flags
22188 @cindex lseek flags, in file-i/o protocol
22197 @unnumberedsubsubsec Limits
22198 @cindex limits, in file-i/o protocol
22200 All values are given in decimal representation.
22203 INT_MIN -2147483648
22205 UINT_MAX 4294967295
22206 LONG_MIN -9223372036854775808
22207 LONG_MAX 9223372036854775807
22208 ULONG_MAX 18446744073709551615
22211 @node File-I/O Examples
22212 @subsection File-I/O Examples
22213 @cindex file-i/o examples
22215 Example sequence of a write call, file descriptor 3, buffer is at target
22216 address 0x1234, 6 bytes should be written:
22219 <- @code{Fwrite,3,1234,6}
22220 @emph{request memory read from target}
22223 @emph{return "6 bytes written"}
22227 Example sequence of a read call, file descriptor 3, buffer is at target
22228 address 0x1234, 6 bytes should be read:
22231 <- @code{Fread,3,1234,6}
22232 @emph{request memory write to target}
22233 -> @code{X1234,6:XXXXXX}
22234 @emph{return "6 bytes read"}
22238 Example sequence of a read call, call fails on the host due to invalid
22239 file descriptor (EBADF):
22242 <- @code{Fread,3,1234,6}
22246 Example sequence of a read call, user presses Ctrl-C before syscall on
22250 <- @code{Fread,3,1234,6}
22255 Example sequence of a read call, user presses Ctrl-C after syscall on
22259 <- @code{Fread,3,1234,6}
22260 -> @code{X1234,6:XXXXXX}
22264 @include agentexpr.texi
22278 % I think something like @colophon should be in texinfo. In the
22280 \long\def\colophon{\hbox to0pt{}\vfill
22281 \centerline{The body of this manual is set in}
22282 \centerline{\fontname\tenrm,}
22283 \centerline{with headings in {\bf\fontname\tenbf}}
22284 \centerline{and examples in {\tt\fontname\tentt}.}
22285 \centerline{{\it\fontname\tenit\/},}
22286 \centerline{{\bf\fontname\tenbf}, and}
22287 \centerline{{\sl\fontname\tensl\/}}
22288 \centerline{are used for emphasis.}\vfill}
22290 % Blame: doc@cygnus.com, 1991.