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 -l @var{timeout}
1083 Set the timeout (in seconds) of any communication used by @value{GDBN}
1084 for remote debugging.
1086 @item -tty @var{device}
1087 @itemx -t @var{device}
1088 @cindex @code{--tty}
1090 Run using @var{device} for your program's standard input and output.
1091 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1093 @c resolve the situation of these eventually
1095 @cindex @code{--tui}
1096 Activate the @dfn{Text User Interface} when starting. The Text User
1097 Interface manages several text windows on the terminal, showing
1098 source, assembly, registers and @value{GDBN} command outputs
1099 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1100 Text User Interface can be enabled by invoking the program
1101 @samp{gdbtui}. Do not use this option if you run @value{GDBN} from
1102 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1105 @c @cindex @code{--xdb}
1106 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1107 @c For information, see the file @file{xdb_trans.html}, which is usually
1108 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1111 @item -interpreter @var{interp}
1112 @cindex @code{--interpreter}
1113 Use the interpreter @var{interp} for interface with the controlling
1114 program or device. This option is meant to be set by programs which
1115 communicate with @value{GDBN} using it as a back end.
1116 @xref{Interpreters, , Command Interpreters}.
1118 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1119 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1120 The @sc{gdb/mi} Interface}) included since @var{GDBN} version 6.0. The
1121 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1122 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1123 @sc{gdb/mi} interfaces are no longer supported.
1126 @cindex @code{--write}
1127 Open the executable and core files for both reading and writing. This
1128 is equivalent to the @samp{set write on} command inside @value{GDBN}
1132 @cindex @code{--statistics}
1133 This option causes @value{GDBN} to print statistics about time and
1134 memory usage after it completes each command and returns to the prompt.
1137 @cindex @code{--version}
1138 This option causes @value{GDBN} to print its version number and
1139 no-warranty blurb, and exit.
1144 @section Quitting @value{GDBN}
1145 @cindex exiting @value{GDBN}
1146 @cindex leaving @value{GDBN}
1149 @kindex quit @r{[}@var{expression}@r{]}
1150 @kindex q @r{(@code{quit})}
1151 @item quit @r{[}@var{expression}@r{]}
1153 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1154 @code{q}), or type an end-of-file character (usually @kbd{C-d}). If you
1155 do not supply @var{expression}, @value{GDBN} will terminate normally;
1156 otherwise it will terminate using the result of @var{expression} as the
1161 An interrupt (often @kbd{C-c}) does not exit from @value{GDBN}, but rather
1162 terminates the action of any @value{GDBN} command that is in progress and
1163 returns to @value{GDBN} command level. It is safe to type the interrupt
1164 character at any time because @value{GDBN} does not allow it to take effect
1165 until a time when it is safe.
1167 If you have been using @value{GDBN} to control an attached process or
1168 device, you can release it with the @code{detach} command
1169 (@pxref{Attach, ,Debugging an already-running process}).
1171 @node Shell Commands
1172 @section Shell commands
1174 If you need to execute occasional shell commands during your
1175 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1176 just use the @code{shell} command.
1180 @cindex shell escape
1181 @item shell @var{command string}
1182 Invoke a standard shell to execute @var{command string}.
1183 If it exists, the environment variable @code{SHELL} determines which
1184 shell to run. Otherwise @value{GDBN} uses the default shell
1185 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1188 The utility @code{make} is often needed in development environments.
1189 You do not have to use the @code{shell} command for this purpose in
1194 @cindex calling make
1195 @item make @var{make-args}
1196 Execute the @code{make} program with the specified
1197 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1200 @node Logging output
1201 @section Logging output
1202 @cindex logging @value{GDBN} output
1204 You may want to save the output of @value{GDBN} commands to a file.
1205 There are several commands to control @value{GDBN}'s logging.
1209 @item set logging on
1211 @item set logging off
1213 @item set logging file @var{file}
1214 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1215 @item set logging overwrite [on|off]
1216 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1217 you want @code{set logging on} to overwrite the logfile instead.
1218 @item set logging redirect [on|off]
1219 By default, @value{GDBN} output will go to both the terminal and the logfile.
1220 Set @code{redirect} if you want output to go only to the log file.
1221 @kindex show logging
1223 Show the current values of the logging settings.
1227 @chapter @value{GDBN} Commands
1229 You can abbreviate a @value{GDBN} command to the first few letters of the command
1230 name, if that abbreviation is unambiguous; and you can repeat certain
1231 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1232 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1233 show you the alternatives available, if there is more than one possibility).
1236 * Command Syntax:: How to give commands to @value{GDBN}
1237 * Completion:: Command completion
1238 * Help:: How to ask @value{GDBN} for help
1241 @node Command Syntax
1242 @section Command syntax
1244 A @value{GDBN} command is a single line of input. There is no limit on
1245 how long it can be. It starts with a command name, which is followed by
1246 arguments whose meaning depends on the command name. For example, the
1247 command @code{step} accepts an argument which is the number of times to
1248 step, as in @samp{step 5}. You can also use the @code{step} command
1249 with no arguments. Some commands do not allow any arguments.
1251 @cindex abbreviation
1252 @value{GDBN} command names may always be truncated if that abbreviation is
1253 unambiguous. Other possible command abbreviations are listed in the
1254 documentation for individual commands. In some cases, even ambiguous
1255 abbreviations are allowed; for example, @code{s} is specially defined as
1256 equivalent to @code{step} even though there are other commands whose
1257 names start with @code{s}. You can test abbreviations by using them as
1258 arguments to the @code{help} command.
1260 @cindex repeating commands
1261 @kindex RET @r{(repeat last command)}
1262 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1263 repeat the previous command. Certain commands (for example, @code{run})
1264 will not repeat this way; these are commands whose unintentional
1265 repetition might cause trouble and which you are unlikely to want to
1268 The @code{list} and @code{x} commands, when you repeat them with
1269 @key{RET}, construct new arguments rather than repeating
1270 exactly as typed. This permits easy scanning of source or memory.
1272 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1273 output, in a way similar to the common utility @code{more}
1274 (@pxref{Screen Size,,Screen size}). Since it is easy to press one
1275 @key{RET} too many in this situation, @value{GDBN} disables command
1276 repetition after any command that generates this sort of display.
1278 @kindex # @r{(a comment)}
1280 Any text from a @kbd{#} to the end of the line is a comment; it does
1281 nothing. This is useful mainly in command files (@pxref{Command
1282 Files,,Command files}).
1284 @cindex repeating command sequences
1285 @kindex C-o @r{(operate-and-get-next)}
1286 The @kbd{C-o} binding is useful for repeating a complex sequence of
1287 commands. This command accepts the current line, like @kbd{RET}, and
1288 then fetches the next line relative to the current line from the history
1292 @section Command completion
1295 @cindex word completion
1296 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1297 only one possibility; it can also show you what the valid possibilities
1298 are for the next word in a command, at any time. This works for @value{GDBN}
1299 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1301 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1302 of a word. If there is only one possibility, @value{GDBN} fills in the
1303 word, and waits for you to finish the command (or press @key{RET} to
1304 enter it). For example, if you type
1306 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1307 @c complete accuracy in these examples; space introduced for clarity.
1308 @c If texinfo enhancements make it unnecessary, it would be nice to
1309 @c replace " @key" by "@key" in the following...
1311 (@value{GDBP}) info bre @key{TAB}
1315 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1316 the only @code{info} subcommand beginning with @samp{bre}:
1319 (@value{GDBP}) info breakpoints
1323 You can either press @key{RET} at this point, to run the @code{info
1324 breakpoints} command, or backspace and enter something else, if
1325 @samp{breakpoints} does not look like the command you expected. (If you
1326 were sure you wanted @code{info breakpoints} in the first place, you
1327 might as well just type @key{RET} immediately after @samp{info bre},
1328 to exploit command abbreviations rather than command completion).
1330 If there is more than one possibility for the next word when you press
1331 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1332 characters and try again, or just press @key{TAB} a second time;
1333 @value{GDBN} displays all the possible completions for that word. For
1334 example, you might want to set a breakpoint on a subroutine whose name
1335 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1336 just sounds the bell. Typing @key{TAB} again displays all the
1337 function names in your program that begin with those characters, for
1341 (@value{GDBP}) b make_ @key{TAB}
1342 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1343 make_a_section_from_file make_environ
1344 make_abs_section make_function_type
1345 make_blockvector make_pointer_type
1346 make_cleanup make_reference_type
1347 make_command make_symbol_completion_list
1348 (@value{GDBP}) b make_
1352 After displaying the available possibilities, @value{GDBN} copies your
1353 partial input (@samp{b make_} in the example) so you can finish the
1356 If you just want to see the list of alternatives in the first place, you
1357 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1358 means @kbd{@key{META} ?}. You can type this either by holding down a
1359 key designated as the @key{META} shift on your keyboard (if there is
1360 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1362 @cindex quotes in commands
1363 @cindex completion of quoted strings
1364 Sometimes the string you need, while logically a ``word'', may contain
1365 parentheses or other characters that @value{GDBN} normally excludes from
1366 its notion of a word. To permit word completion to work in this
1367 situation, you may enclose words in @code{'} (single quote marks) in
1368 @value{GDBN} commands.
1370 The most likely situation where you might need this is in typing the
1371 name of a C@t{++} function. This is because C@t{++} allows function
1372 overloading (multiple definitions of the same function, distinguished
1373 by argument type). For example, when you want to set a breakpoint you
1374 may need to distinguish whether you mean the version of @code{name}
1375 that takes an @code{int} parameter, @code{name(int)}, or the version
1376 that takes a @code{float} parameter, @code{name(float)}. To use the
1377 word-completion facilities in this situation, type a single quote
1378 @code{'} at the beginning of the function name. This alerts
1379 @value{GDBN} that it may need to consider more information than usual
1380 when you press @key{TAB} or @kbd{M-?} to request word completion:
1383 (@value{GDBP}) b 'bubble( @kbd{M-?}
1384 bubble(double,double) bubble(int,int)
1385 (@value{GDBP}) b 'bubble(
1388 In some cases, @value{GDBN} can tell that completing a name requires using
1389 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1390 completing as much as it can) if you do not type the quote in the first
1394 (@value{GDBP}) b bub @key{TAB}
1395 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1396 (@value{GDBP}) b 'bubble(
1400 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1401 you have not yet started typing the argument list when you ask for
1402 completion on an overloaded symbol.
1404 For more information about overloaded functions, see @ref{C plus plus
1405 expressions, ,C@t{++} expressions}. You can use the command @code{set
1406 overload-resolution off} to disable overload resolution;
1407 see @ref{Debugging C plus plus, ,@value{GDBN} features for C@t{++}}.
1411 @section Getting help
1412 @cindex online documentation
1415 You can always ask @value{GDBN} itself for information on its commands,
1416 using the command @code{help}.
1419 @kindex h @r{(@code{help})}
1422 You can use @code{help} (abbreviated @code{h}) with no arguments to
1423 display a short list of named classes of commands:
1427 List of classes of commands:
1429 aliases -- Aliases of other commands
1430 breakpoints -- Making program stop at certain points
1431 data -- Examining data
1432 files -- Specifying and examining files
1433 internals -- Maintenance commands
1434 obscure -- Obscure features
1435 running -- Running the program
1436 stack -- Examining the stack
1437 status -- Status inquiries
1438 support -- Support facilities
1439 tracepoints -- Tracing of program execution without@*
1440 stopping the program
1441 user-defined -- User-defined commands
1443 Type "help" followed by a class name for a list of
1444 commands in that class.
1445 Type "help" followed by command name for full
1447 Command name abbreviations are allowed if unambiguous.
1450 @c the above line break eliminates huge line overfull...
1452 @item help @var{class}
1453 Using one of the general help classes as an argument, you can get a
1454 list of the individual commands in that class. For example, here is the
1455 help display for the class @code{status}:
1458 (@value{GDBP}) help status
1463 @c Line break in "show" line falsifies real output, but needed
1464 @c to fit in smallbook page size.
1465 info -- Generic command for showing things
1466 about the program being debugged
1467 show -- Generic command for showing things
1470 Type "help" followed by command name for full
1472 Command name abbreviations are allowed if unambiguous.
1476 @item help @var{command}
1477 With a command name as @code{help} argument, @value{GDBN} displays a
1478 short paragraph on how to use that command.
1481 @item apropos @var{args}
1482 The @code{apropos @var{args}} command searches through all of the @value{GDBN}
1483 commands, and their documentation, for the regular expression specified in
1484 @var{args}. It prints out all matches found. For example:
1495 set symbol-reloading -- Set dynamic symbol table reloading
1496 multiple times in one run
1497 show symbol-reloading -- Show dynamic symbol table reloading
1498 multiple times in one run
1503 @item complete @var{args}
1504 The @code{complete @var{args}} command lists all the possible completions
1505 for the beginning of a command. Use @var{args} to specify the beginning of the
1506 command you want completed. For example:
1512 @noindent results in:
1523 @noindent This is intended for use by @sc{gnu} Emacs.
1526 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1527 and @code{show} to inquire about the state of your program, or the state
1528 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1529 manual introduces each of them in the appropriate context. The listings
1530 under @code{info} and under @code{show} in the Index point to
1531 all the sub-commands. @xref{Index}.
1536 @kindex i @r{(@code{info})}
1538 This command (abbreviated @code{i}) is for describing the state of your
1539 program. For example, you can list the arguments given to your program
1540 with @code{info args}, list the registers currently in use with @code{info
1541 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1542 You can get a complete list of the @code{info} sub-commands with
1543 @w{@code{help info}}.
1547 You can assign the result of an expression to an environment variable with
1548 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1549 @code{set prompt $}.
1553 In contrast to @code{info}, @code{show} is for describing the state of
1554 @value{GDBN} itself.
1555 You can change most of the things you can @code{show}, by using the
1556 related command @code{set}; for example, you can control what number
1557 system is used for displays with @code{set radix}, or simply inquire
1558 which is currently in use with @code{show radix}.
1561 To display all the settable parameters and their current
1562 values, you can use @code{show} with no arguments; you may also use
1563 @code{info set}. Both commands produce the same display.
1564 @c FIXME: "info set" violates the rule that "info" is for state of
1565 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1566 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1570 Here are three miscellaneous @code{show} subcommands, all of which are
1571 exceptional in lacking corresponding @code{set} commands:
1574 @kindex show version
1575 @cindex version number
1577 Show what version of @value{GDBN} is running. You should include this
1578 information in @value{GDBN} bug-reports. If multiple versions of
1579 @value{GDBN} are in use at your site, you may need to determine which
1580 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1581 commands are introduced, and old ones may wither away. Also, many
1582 system vendors ship variant versions of @value{GDBN}, and there are
1583 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1584 The version number is the same as the one announced when you start
1587 @kindex show copying
1589 Display information about permission for copying @value{GDBN}.
1591 @kindex show warranty
1593 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1594 if your version of @value{GDBN} comes with one.
1599 @chapter Running Programs Under @value{GDBN}
1601 When you run a program under @value{GDBN}, you must first generate
1602 debugging information when you compile it.
1604 You may start @value{GDBN} with its arguments, if any, in an environment
1605 of your choice. If you are doing native debugging, you may redirect
1606 your program's input and output, debug an already running process, or
1607 kill a child process.
1610 * Compilation:: Compiling for debugging
1611 * Starting:: Starting your program
1612 * Arguments:: Your program's arguments
1613 * Environment:: Your program's environment
1615 * Working Directory:: Your program's working directory
1616 * Input/Output:: Your program's input and output
1617 * Attach:: Debugging an already-running process
1618 * Kill Process:: Killing the child process
1620 * Threads:: Debugging programs with multiple threads
1621 * Processes:: Debugging programs with multiple processes
1625 @section Compiling for debugging
1627 In order to debug a program effectively, you need to generate
1628 debugging information when you compile it. This debugging information
1629 is stored in the object file; it describes the data type of each
1630 variable or function and the correspondence between source line numbers
1631 and addresses in the executable code.
1633 To request debugging information, specify the @samp{-g} option when you run
1636 Most compilers do not include information about preprocessor macros in
1637 the debugging information if you specify the @option{-g} flag alone,
1638 because this information is rather large. Version 3.1 of @value{NGCC},
1639 the @sc{gnu} C compiler, provides macro information if you specify the
1640 options @option{-gdwarf-2} and @option{-g3}; the former option requests
1641 debugging information in the Dwarf 2 format, and the latter requests
1642 ``extra information''. In the future, we hope to find more compact ways
1643 to represent macro information, so that it can be included with
1646 Many C compilers are unable to handle the @samp{-g} and @samp{-O}
1647 options together. Using those compilers, you cannot generate optimized
1648 executables containing debugging information.
1650 @value{NGCC}, the @sc{gnu} C compiler, supports @samp{-g} with or
1651 without @samp{-O}, making it possible to debug optimized code. We
1652 recommend that you @emph{always} use @samp{-g} whenever you compile a
1653 program. You may think your program is correct, but there is no sense
1654 in pushing your luck.
1656 @cindex optimized code, debugging
1657 @cindex debugging optimized code
1658 When you debug a program compiled with @samp{-g -O}, remember that the
1659 optimizer is rearranging your code; the debugger shows you what is
1660 really there. Do not be too surprised when the execution path does not
1661 exactly match your source file! An extreme example: if you define a
1662 variable, but never use it, @value{GDBN} never sees that
1663 variable---because the compiler optimizes it out of existence.
1665 Some things do not work as well with @samp{-g -O} as with just
1666 @samp{-g}, particularly on machines with instruction scheduling. If in
1667 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1668 please report it to us as a bug (including a test case!).
1669 @xref{Variables}, for more information about debugging optimized code.
1671 Older versions of the @sc{gnu} C compiler permitted a variant option
1672 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1673 format; if your @sc{gnu} C compiler has this option, do not use it.
1677 @section Starting your program
1683 @kindex r @r{(@code{run})}
1686 Use the @code{run} command to start your program under @value{GDBN}.
1687 You must first specify the program name (except on VxWorks) with an
1688 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1689 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1690 (@pxref{Files, ,Commands to specify files}).
1694 If you are running your program in an execution environment that
1695 supports processes, @code{run} creates an inferior process and makes
1696 that process run your program. (In environments without processes,
1697 @code{run} jumps to the start of your program.)
1699 The execution of a program is affected by certain information it
1700 receives from its superior. @value{GDBN} provides ways to specify this
1701 information, which you must do @emph{before} starting your program. (You
1702 can change it after starting your program, but such changes only affect
1703 your program the next time you start it.) This information may be
1704 divided into four categories:
1707 @item The @emph{arguments.}
1708 Specify the arguments to give your program as the arguments of the
1709 @code{run} command. If a shell is available on your target, the shell
1710 is used to pass the arguments, so that you may use normal conventions
1711 (such as wildcard expansion or variable substitution) in describing
1713 In Unix systems, you can control which shell is used with the
1714 @code{SHELL} environment variable.
1715 @xref{Arguments, ,Your program's arguments}.
1717 @item The @emph{environment.}
1718 Your program normally inherits its environment from @value{GDBN}, but you can
1719 use the @value{GDBN} commands @code{set environment} and @code{unset
1720 environment} to change parts of the environment that affect
1721 your program. @xref{Environment, ,Your program's environment}.
1723 @item The @emph{working directory.}
1724 Your program inherits its working directory from @value{GDBN}. You can set
1725 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1726 @xref{Working Directory, ,Your program's working directory}.
1728 @item The @emph{standard input and output.}
1729 Your program normally uses the same device for standard input and
1730 standard output as @value{GDBN} is using. You can redirect input and output
1731 in the @code{run} command line, or you can use the @code{tty} command to
1732 set a different device for your program.
1733 @xref{Input/Output, ,Your program's input and output}.
1736 @emph{Warning:} While input and output redirection work, you cannot use
1737 pipes to pass the output of the program you are debugging to another
1738 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1742 When you issue the @code{run} command, your program begins to execute
1743 immediately. @xref{Stopping, ,Stopping and continuing}, for discussion
1744 of how to arrange for your program to stop. Once your program has
1745 stopped, you may call functions in your program, using the @code{print}
1746 or @code{call} commands. @xref{Data, ,Examining Data}.
1748 If the modification time of your symbol file has changed since the last
1749 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1750 table, and reads it again. When it does this, @value{GDBN} tries to retain
1751 your current breakpoints.
1756 @cindex run to main procedure
1757 The name of the main procedure can vary from language to language.
1758 With C or C@t{++}, the main procedure name is always @code{main}, but
1759 other languages such as Ada do not require a specific name for their
1760 main procedure. The debugger provides a convenient way to start the
1761 execution of the program and to stop at the beginning of the main
1762 procedure, depending on the language used.
1764 The @samp{start} command does the equivalent of setting a temporary
1765 breakpoint at the beginning of the main procedure and then invoking
1766 the @samp{run} command.
1768 @cindex elaboration phase
1769 Some programs contain an @dfn{elaboration} phase where some startup code is
1770 executed before the main procedure is called. This depends on the
1771 languages used to write your program. In C@t{++}, for instance,
1772 constructors for static and global objects are executed before
1773 @code{main} is called. It is therefore possible that the debugger stops
1774 before reaching the main procedure. However, the temporary breakpoint
1775 will remain to halt execution.
1777 Specify the arguments to give to your program as arguments to the
1778 @samp{start} command. These arguments will be given verbatim to the
1779 underlying @samp{run} command. Note that the same arguments will be
1780 reused if no argument is provided during subsequent calls to
1781 @samp{start} or @samp{run}.
1783 It is sometimes necessary to debug the program during elaboration. In
1784 these cases, using the @code{start} command would stop the execution of
1785 your program too late, as the program would have already completed the
1786 elaboration phase. Under these circumstances, insert breakpoints in your
1787 elaboration code before running your program.
1791 @section Your program's arguments
1793 @cindex arguments (to your program)
1794 The arguments to your program can be specified by the arguments of the
1796 They are passed to a shell, which expands wildcard characters and
1797 performs redirection of I/O, and thence to your program. Your
1798 @code{SHELL} environment variable (if it exists) specifies what shell
1799 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1800 the default shell (@file{/bin/sh} on Unix).
1802 On non-Unix systems, the program is usually invoked directly by
1803 @value{GDBN}, which emulates I/O redirection via the appropriate system
1804 calls, and the wildcard characters are expanded by the startup code of
1805 the program, not by the shell.
1807 @code{run} with no arguments uses the same arguments used by the previous
1808 @code{run}, or those set by the @code{set args} command.
1813 Specify the arguments to be used the next time your program is run. If
1814 @code{set args} has no arguments, @code{run} executes your program
1815 with no arguments. Once you have run your program with arguments,
1816 using @code{set args} before the next @code{run} is the only way to run
1817 it again without arguments.
1821 Show the arguments to give your program when it is started.
1825 @section Your program's environment
1827 @cindex environment (of your program)
1828 The @dfn{environment} consists of a set of environment variables and
1829 their values. Environment variables conventionally record such things as
1830 your user name, your home directory, your terminal type, and your search
1831 path for programs to run. Usually you set up environment variables with
1832 the shell and they are inherited by all the other programs you run. When
1833 debugging, it can be useful to try running your program with a modified
1834 environment without having to start @value{GDBN} over again.
1838 @item path @var{directory}
1839 Add @var{directory} to the front of the @code{PATH} environment variable
1840 (the search path for executables) that will be passed to your program.
1841 The value of @code{PATH} used by @value{GDBN} does not change.
1842 You may specify several directory names, separated by whitespace or by a
1843 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1844 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1845 is moved to the front, so it is searched sooner.
1847 You can use the string @samp{$cwd} to refer to whatever is the current
1848 working directory at the time @value{GDBN} searches the path. If you
1849 use @samp{.} instead, it refers to the directory where you executed the
1850 @code{path} command. @value{GDBN} replaces @samp{.} in the
1851 @var{directory} argument (with the current path) before adding
1852 @var{directory} to the search path.
1853 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1854 @c document that, since repeating it would be a no-op.
1858 Display the list of search paths for executables (the @code{PATH}
1859 environment variable).
1861 @kindex show environment
1862 @item show environment @r{[}@var{varname}@r{]}
1863 Print the value of environment variable @var{varname} to be given to
1864 your program when it starts. If you do not supply @var{varname},
1865 print the names and values of all environment variables to be given to
1866 your program. You can abbreviate @code{environment} as @code{env}.
1868 @kindex set environment
1869 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1870 Set environment variable @var{varname} to @var{value}. The value
1871 changes for your program only, not for @value{GDBN} itself. @var{value} may
1872 be any string; the values of environment variables are just strings, and
1873 any interpretation is supplied by your program itself. The @var{value}
1874 parameter is optional; if it is eliminated, the variable is set to a
1876 @c "any string" here does not include leading, trailing
1877 @c blanks. Gnu asks: does anyone care?
1879 For example, this command:
1886 tells the debugged program, when subsequently run, that its user is named
1887 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
1888 are not actually required.)
1890 @kindex unset environment
1891 @item unset environment @var{varname}
1892 Remove variable @var{varname} from the environment to be passed to your
1893 program. This is different from @samp{set env @var{varname} =};
1894 @code{unset environment} removes the variable from the environment,
1895 rather than assigning it an empty value.
1898 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
1900 by your @code{SHELL} environment variable if it exists (or
1901 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
1902 that runs an initialization file---such as @file{.cshrc} for C-shell, or
1903 @file{.bashrc} for BASH---any variables you set in that file affect
1904 your program. You may wish to move setting of environment variables to
1905 files that are only run when you sign on, such as @file{.login} or
1908 @node Working Directory
1909 @section Your program's working directory
1911 @cindex working directory (of your program)
1912 Each time you start your program with @code{run}, it inherits its
1913 working directory from the current working directory of @value{GDBN}.
1914 The @value{GDBN} working directory is initially whatever it inherited
1915 from its parent process (typically the shell), but you can specify a new
1916 working directory in @value{GDBN} with the @code{cd} command.
1918 The @value{GDBN} working directory also serves as a default for the commands
1919 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
1924 @item cd @var{directory}
1925 Set the @value{GDBN} working directory to @var{directory}.
1929 Print the @value{GDBN} working directory.
1932 It is generally impossible to find the current working directory of
1933 the process being debugged (since a program can change its directory
1934 during its run). If you work on a system where @value{GDBN} is
1935 configured with the @file{/proc} support, you can use the @code{info
1936 proc} command (@pxref{SVR4 Process Information}) to find out the
1937 current working directory of the debuggee.
1940 @section Your program's input and output
1945 By default, the program you run under @value{GDBN} does input and output to
1946 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
1947 to its own terminal modes to interact with you, but it records the terminal
1948 modes your program was using and switches back to them when you continue
1949 running your program.
1952 @kindex info terminal
1954 Displays information recorded by @value{GDBN} about the terminal modes your
1958 You can redirect your program's input and/or output using shell
1959 redirection with the @code{run} command. For example,
1966 starts your program, diverting its output to the file @file{outfile}.
1969 @cindex controlling terminal
1970 Another way to specify where your program should do input and output is
1971 with the @code{tty} command. This command accepts a file name as
1972 argument, and causes this file to be the default for future @code{run}
1973 commands. It also resets the controlling terminal for the child
1974 process, for future @code{run} commands. For example,
1981 directs that processes started with subsequent @code{run} commands
1982 default to do input and output on the terminal @file{/dev/ttyb} and have
1983 that as their controlling terminal.
1985 An explicit redirection in @code{run} overrides the @code{tty} command's
1986 effect on the input/output device, but not its effect on the controlling
1989 When you use the @code{tty} command or redirect input in the @code{run}
1990 command, only the input @emph{for your program} is affected. The input
1991 for @value{GDBN} still comes from your terminal.
1994 @section Debugging an already-running process
1999 @item attach @var{process-id}
2000 This command attaches to a running process---one that was started
2001 outside @value{GDBN}. (@code{info files} shows your active
2002 targets.) The command takes as argument a process ID. The usual way to
2003 find out the process-id of a Unix process is with the @code{ps} utility,
2004 or with the @samp{jobs -l} shell command.
2006 @code{attach} does not repeat if you press @key{RET} a second time after
2007 executing the command.
2010 To use @code{attach}, your program must be running in an environment
2011 which supports processes; for example, @code{attach} does not work for
2012 programs on bare-board targets that lack an operating system. You must
2013 also have permission to send the process a signal.
2015 When you use @code{attach}, the debugger finds the program running in
2016 the process first by looking in the current working directory, then (if
2017 the program is not found) by using the source file search path
2018 (@pxref{Source Path, ,Specifying source directories}). You can also use
2019 the @code{file} command to load the program. @xref{Files, ,Commands to
2022 The first thing @value{GDBN} does after arranging to debug the specified
2023 process is to stop it. You can examine and modify an attached process
2024 with all the @value{GDBN} commands that are ordinarily available when
2025 you start processes with @code{run}. You can insert breakpoints; you
2026 can step and continue; you can modify storage. If you would rather the
2027 process continue running, you may use the @code{continue} command after
2028 attaching @value{GDBN} to the process.
2033 When you have finished debugging the attached process, you can use the
2034 @code{detach} command to release it from @value{GDBN} control. Detaching
2035 the process continues its execution. After the @code{detach} command,
2036 that process and @value{GDBN} become completely independent once more, and you
2037 are ready to @code{attach} another process or start one with @code{run}.
2038 @code{detach} does not repeat if you press @key{RET} again after
2039 executing the command.
2042 If you exit @value{GDBN} or use the @code{run} command while you have an
2043 attached process, you kill that process. By default, @value{GDBN} asks
2044 for confirmation if you try to do either of these things; you can
2045 control whether or not you need to confirm by using the @code{set
2046 confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
2050 @section Killing the child process
2055 Kill the child process in which your program is running under @value{GDBN}.
2058 This command is useful if you wish to debug a core dump instead of a
2059 running process. @value{GDBN} ignores any core dump file while your program
2062 On some operating systems, a program cannot be executed outside @value{GDBN}
2063 while you have breakpoints set on it inside @value{GDBN}. You can use the
2064 @code{kill} command in this situation to permit running your program
2065 outside the debugger.
2067 The @code{kill} command is also useful if you wish to recompile and
2068 relink your program, since on many systems it is impossible to modify an
2069 executable file while it is running in a process. In this case, when you
2070 next type @code{run}, @value{GDBN} notices that the file has changed, and
2071 reads the symbol table again (while trying to preserve your current
2072 breakpoint settings).
2075 @section Debugging programs with multiple threads
2077 @cindex threads of execution
2078 @cindex multiple threads
2079 @cindex switching threads
2080 In some operating systems, such as HP-UX and Solaris, a single program
2081 may have more than one @dfn{thread} of execution. The precise semantics
2082 of threads differ from one operating system to another, but in general
2083 the threads of a single program are akin to multiple processes---except
2084 that they share one address space (that is, they can all examine and
2085 modify the same variables). On the other hand, each thread has its own
2086 registers and execution stack, and perhaps private memory.
2088 @value{GDBN} provides these facilities for debugging multi-thread
2092 @item automatic notification of new threads
2093 @item @samp{thread @var{threadno}}, a command to switch among threads
2094 @item @samp{info threads}, a command to inquire about existing threads
2095 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2096 a command to apply a command to a list of threads
2097 @item thread-specific breakpoints
2101 @emph{Warning:} These facilities are not yet available on every
2102 @value{GDBN} configuration where the operating system supports threads.
2103 If your @value{GDBN} does not support threads, these commands have no
2104 effect. For example, a system without thread support shows no output
2105 from @samp{info threads}, and always rejects the @code{thread} command,
2109 (@value{GDBP}) info threads
2110 (@value{GDBP}) thread 1
2111 Thread ID 1 not known. Use the "info threads" command to
2112 see the IDs of currently known threads.
2114 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2115 @c doesn't support threads"?
2118 @cindex focus of debugging
2119 @cindex current thread
2120 The @value{GDBN} thread debugging facility allows you to observe all
2121 threads while your program runs---but whenever @value{GDBN} takes
2122 control, one thread in particular is always the focus of debugging.
2123 This thread is called the @dfn{current thread}. Debugging commands show
2124 program information from the perspective of the current thread.
2126 @cindex @code{New} @var{systag} message
2127 @cindex thread identifier (system)
2128 @c FIXME-implementors!! It would be more helpful if the [New...] message
2129 @c included GDB's numeric thread handle, so you could just go to that
2130 @c thread without first checking `info threads'.
2131 Whenever @value{GDBN} detects a new thread in your program, it displays
2132 the target system's identification for the thread with a message in the
2133 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2134 whose form varies depending on the particular system. For example, on
2135 LynxOS, you might see
2138 [New process 35 thread 27]
2142 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2143 the @var{systag} is simply something like @samp{process 368}, with no
2146 @c FIXME!! (1) Does the [New...] message appear even for the very first
2147 @c thread of a program, or does it only appear for the
2148 @c second---i.e.@: when it becomes obvious we have a multithread
2150 @c (2) *Is* there necessarily a first thread always? Or do some
2151 @c multithread systems permit starting a program with multiple
2152 @c threads ab initio?
2154 @cindex thread number
2155 @cindex thread identifier (GDB)
2156 For debugging purposes, @value{GDBN} associates its own thread
2157 number---always a single integer---with each thread in your program.
2160 @kindex info threads
2162 Display a summary of all threads currently in your
2163 program. @value{GDBN} displays for each thread (in this order):
2166 @item the thread number assigned by @value{GDBN}
2168 @item the target system's thread identifier (@var{systag})
2170 @item the current stack frame summary for that thread
2174 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2175 indicates the current thread.
2179 @c end table here to get a little more width for example
2182 (@value{GDBP}) info threads
2183 3 process 35 thread 27 0x34e5 in sigpause ()
2184 2 process 35 thread 23 0x34e5 in sigpause ()
2185 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2191 @cindex debugging multithreaded programs (on HP-UX)
2192 @cindex thread identifier (GDB), on HP-UX
2193 For debugging purposes, @value{GDBN} associates its own thread
2194 number---a small integer assigned in thread-creation order---with each
2195 thread in your program.
2197 @cindex @code{New} @var{systag} message, on HP-UX
2198 @cindex thread identifier (system), on HP-UX
2199 @c FIXME-implementors!! It would be more helpful if the [New...] message
2200 @c included GDB's numeric thread handle, so you could just go to that
2201 @c thread without first checking `info threads'.
2202 Whenever @value{GDBN} detects a new thread in your program, it displays
2203 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2204 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2205 whose form varies depending on the particular system. For example, on
2209 [New thread 2 (system thread 26594)]
2213 when @value{GDBN} notices a new thread.
2216 @kindex info threads (HP-UX)
2218 Display a summary of all threads currently in your
2219 program. @value{GDBN} displays for each thread (in this order):
2222 @item the thread number assigned by @value{GDBN}
2224 @item the target system's thread identifier (@var{systag})
2226 @item the current stack frame summary for that thread
2230 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2231 indicates the current thread.
2235 @c end table here to get a little more width for example
2238 (@value{GDBP}) info threads
2239 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2241 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2242 from /usr/lib/libc.2
2243 1 system thread 27905 0x7b003498 in _brk () \@*
2244 from /usr/lib/libc.2
2248 @kindex thread @var{threadno}
2249 @item thread @var{threadno}
2250 Make thread number @var{threadno} the current thread. The command
2251 argument @var{threadno} is the internal @value{GDBN} thread number, as
2252 shown in the first field of the @samp{info threads} display.
2253 @value{GDBN} responds by displaying the system identifier of the thread
2254 you selected, and its current stack frame summary:
2257 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2258 (@value{GDBP}) thread 2
2259 [Switching to process 35 thread 23]
2260 0x34e5 in sigpause ()
2264 As with the @samp{[New @dots{}]} message, the form of the text after
2265 @samp{Switching to} depends on your system's conventions for identifying
2268 @item thread apply [@var{threadno}] [@var{all}] @var{args}
2269 The @code{thread apply} command allows you to apply a command to one or
2270 more threads. Specify the numbers of the threads that you want affected
2271 with the command argument @var{threadno}. @var{threadno} is the internal
2272 @value{GDBN} thread number, as shown in the first field of the @samp{info
2273 threads} display. To apply a command to all threads, use
2274 @code{thread apply all} @var{args}.
2277 @cindex automatic thread selection
2278 @cindex switching threads automatically
2279 @cindex threads, automatic switching
2280 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2281 signal, it automatically selects the thread where that breakpoint or
2282 signal happened. @value{GDBN} alerts you to the context switch with a
2283 message of the form @samp{[Switching to @var{systag}]} to identify the
2286 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2287 more information about how @value{GDBN} behaves when you stop and start
2288 programs with multiple threads.
2290 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2291 watchpoints in programs with multiple threads.
2294 @section Debugging programs with multiple processes
2296 @cindex fork, debugging programs which call
2297 @cindex multiple processes
2298 @cindex processes, multiple
2299 On most systems, @value{GDBN} has no special support for debugging
2300 programs which create additional processes using the @code{fork}
2301 function. When a program forks, @value{GDBN} will continue to debug the
2302 parent process and the child process will run unimpeded. If you have
2303 set a breakpoint in any code which the child then executes, the child
2304 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2305 will cause it to terminate.
2307 However, if you want to debug the child process there is a workaround
2308 which isn't too painful. Put a call to @code{sleep} in the code which
2309 the child process executes after the fork. It may be useful to sleep
2310 only if a certain environment variable is set, or a certain file exists,
2311 so that the delay need not occur when you don't want to run @value{GDBN}
2312 on the child. While the child is sleeping, use the @code{ps} program to
2313 get its process ID. Then tell @value{GDBN} (a new invocation of
2314 @value{GDBN} if you are also debugging the parent process) to attach to
2315 the child process (@pxref{Attach}). From that point on you can debug
2316 the child process just like any other process which you attached to.
2318 On some systems, @value{GDBN} provides support for debugging programs that
2319 create additional processes using the @code{fork} or @code{vfork} functions.
2320 Currently, the only platforms with this feature are HP-UX (11.x and later
2321 only?) and GNU/Linux (kernel version 2.5.60 and later).
2323 By default, when a program forks, @value{GDBN} will continue to debug
2324 the parent process and the child process will run unimpeded.
2326 If you want to follow the child process instead of the parent process,
2327 use the command @w{@code{set follow-fork-mode}}.
2330 @kindex set follow-fork-mode
2331 @item set follow-fork-mode @var{mode}
2332 Set the debugger response to a program call of @code{fork} or
2333 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2334 process. The @var{mode} can be:
2338 The original process is debugged after a fork. The child process runs
2339 unimpeded. This is the default.
2342 The new process is debugged after a fork. The parent process runs
2347 @item show follow-fork-mode
2348 Display the current debugger response to a @code{fork} or @code{vfork} call.
2351 If you ask to debug a child process and a @code{vfork} is followed by an
2352 @code{exec}, @value{GDBN} executes the new target up to the first
2353 breakpoint in the new target. If you have a breakpoint set on
2354 @code{main} in your original program, the breakpoint will also be set on
2355 the child process's @code{main}.
2357 When a child process is spawned by @code{vfork}, you cannot debug the
2358 child or parent until an @code{exec} call completes.
2360 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2361 call executes, the new target restarts. To restart the parent process,
2362 use the @code{file} command with the parent executable name as its
2365 You can use the @code{catch} command to make @value{GDBN} stop whenever
2366 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2367 Catchpoints, ,Setting catchpoints}.
2370 @chapter Stopping and Continuing
2372 The principal purposes of using a debugger are so that you can stop your
2373 program before it terminates; or so that, if your program runs into
2374 trouble, you can investigate and find out why.
2376 Inside @value{GDBN}, your program may stop for any of several reasons,
2377 such as a signal, a breakpoint, or reaching a new line after a
2378 @value{GDBN} command such as @code{step}. You may then examine and
2379 change variables, set new breakpoints or remove old ones, and then
2380 continue execution. Usually, the messages shown by @value{GDBN} provide
2381 ample explanation of the status of your program---but you can also
2382 explicitly request this information at any time.
2385 @kindex info program
2387 Display information about the status of your program: whether it is
2388 running or not, what process it is, and why it stopped.
2392 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2393 * Continuing and Stepping:: Resuming execution
2395 * Thread Stops:: Stopping and starting multi-thread programs
2399 @section Breakpoints, watchpoints, and catchpoints
2402 A @dfn{breakpoint} makes your program stop whenever a certain point in
2403 the program is reached. For each breakpoint, you can add conditions to
2404 control in finer detail whether your program stops. You can set
2405 breakpoints with the @code{break} command and its variants (@pxref{Set
2406 Breaks, ,Setting breakpoints}), to specify the place where your program
2407 should stop by line number, function name or exact address in the
2410 In HP-UX, SunOS 4.x, SVR4, and Alpha OSF/1 configurations, you can set
2411 breakpoints in shared libraries before the executable is run. There is
2412 a minor limitation on HP-UX systems: you must wait until the executable
2413 is run in order to set breakpoints in shared library routines that are
2414 not called directly by the program (for example, routines that are
2415 arguments in a @code{pthread_create} call).
2418 @cindex memory tracing
2419 @cindex breakpoint on memory address
2420 @cindex breakpoint on variable modification
2421 A @dfn{watchpoint} is a special breakpoint that stops your program
2422 when the value of an expression changes. You must use a different
2423 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
2424 watchpoints}), but aside from that, you can manage a watchpoint like
2425 any other breakpoint: you enable, disable, and delete both breakpoints
2426 and watchpoints using the same commands.
2428 You can arrange to have values from your program displayed automatically
2429 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2433 @cindex breakpoint on events
2434 A @dfn{catchpoint} is another special breakpoint that stops your program
2435 when a certain kind of event occurs, such as the throwing of a C@t{++}
2436 exception or the loading of a library. As with watchpoints, you use a
2437 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2438 catchpoints}), but aside from that, you can manage a catchpoint like any
2439 other breakpoint. (To stop when your program receives a signal, use the
2440 @code{handle} command; see @ref{Signals, ,Signals}.)
2442 @cindex breakpoint numbers
2443 @cindex numbers for breakpoints
2444 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2445 catchpoint when you create it; these numbers are successive integers
2446 starting with one. In many of the commands for controlling various
2447 features of breakpoints you use the breakpoint number to say which
2448 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2449 @dfn{disabled}; if disabled, it has no effect on your program until you
2452 @cindex breakpoint ranges
2453 @cindex ranges of breakpoints
2454 Some @value{GDBN} commands accept a range of breakpoints on which to
2455 operate. A breakpoint range is either a single breakpoint number, like
2456 @samp{5}, or two such numbers, in increasing order, separated by a
2457 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2458 all breakpoint in that range are operated on.
2461 * Set Breaks:: Setting breakpoints
2462 * Set Watchpoints:: Setting watchpoints
2463 * Set Catchpoints:: Setting catchpoints
2464 * Delete Breaks:: Deleting breakpoints
2465 * Disabling:: Disabling breakpoints
2466 * Conditions:: Break conditions
2467 * Break Commands:: Breakpoint command lists
2468 * Breakpoint Menus:: Breakpoint menus
2469 * Error in Breakpoints:: ``Cannot insert breakpoints''
2470 * Breakpoint related warnings:: ``Breakpoint address adjusted...''
2474 @subsection Setting breakpoints
2476 @c FIXME LMB what does GDB do if no code on line of breakpt?
2477 @c consider in particular declaration with/without initialization.
2479 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2482 @kindex b @r{(@code{break})}
2483 @vindex $bpnum@r{, convenience variable}
2484 @cindex latest breakpoint
2485 Breakpoints are set with the @code{break} command (abbreviated
2486 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2487 number of the breakpoint you've set most recently; see @ref{Convenience
2488 Vars,, Convenience variables}, for a discussion of what you can do with
2489 convenience variables.
2491 You have several ways to say where the breakpoint should go.
2494 @item break @var{function}
2495 Set a breakpoint at entry to function @var{function}.
2496 When using source languages that permit overloading of symbols, such as
2497 C@t{++}, @var{function} may refer to more than one possible place to break.
2498 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2500 @item break +@var{offset}
2501 @itemx break -@var{offset}
2502 Set a breakpoint some number of lines forward or back from the position
2503 at which execution stopped in the currently selected @dfn{stack frame}.
2504 (@xref{Frames, ,Frames}, for a description of stack frames.)
2506 @item break @var{linenum}
2507 Set a breakpoint at line @var{linenum} in the current source file.
2508 The current source file is the last file whose source text was printed.
2509 The breakpoint will stop your program just before it executes any of the
2512 @item break @var{filename}:@var{linenum}
2513 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2515 @item break @var{filename}:@var{function}
2516 Set a breakpoint at entry to function @var{function} found in file
2517 @var{filename}. Specifying a file name as well as a function name is
2518 superfluous except when multiple files contain similarly named
2521 @item break *@var{address}
2522 Set a breakpoint at address @var{address}. You can use this to set
2523 breakpoints in parts of your program which do not have debugging
2524 information or source files.
2527 When called without any arguments, @code{break} sets a breakpoint at
2528 the next instruction to be executed in the selected stack frame
2529 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2530 innermost, this makes your program stop as soon as control
2531 returns to that frame. This is similar to the effect of a
2532 @code{finish} command in the frame inside the selected frame---except
2533 that @code{finish} does not leave an active breakpoint. If you use
2534 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2535 the next time it reaches the current location; this may be useful
2538 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2539 least one instruction has been executed. If it did not do this, you
2540 would be unable to proceed past a breakpoint without first disabling the
2541 breakpoint. This rule applies whether or not the breakpoint already
2542 existed when your program stopped.
2544 @item break @dots{} if @var{cond}
2545 Set a breakpoint with condition @var{cond}; evaluate the expression
2546 @var{cond} each time the breakpoint is reached, and stop only if the
2547 value is nonzero---that is, if @var{cond} evaluates as true.
2548 @samp{@dots{}} stands for one of the possible arguments described
2549 above (or no argument) specifying where to break. @xref{Conditions,
2550 ,Break conditions}, for more information on breakpoint conditions.
2553 @item tbreak @var{args}
2554 Set a breakpoint enabled only for one stop. @var{args} are the
2555 same as for the @code{break} command, and the breakpoint is set in the same
2556 way, but the breakpoint is automatically deleted after the first time your
2557 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2560 @item hbreak @var{args}
2561 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2562 @code{break} command and the breakpoint is set in the same way, but the
2563 breakpoint requires hardware support and some target hardware may not
2564 have this support. The main purpose of this is EPROM/ROM code
2565 debugging, so you can set a breakpoint at an instruction without
2566 changing the instruction. This can be used with the new trap-generation
2567 provided by SPARClite DSU and some x86-based targets. These targets
2568 will generate traps when a program accesses some data or instruction
2569 address that is assigned to the debug registers. However the hardware
2570 breakpoint registers can take a limited number of breakpoints. For
2571 example, on the DSU, only two data breakpoints can be set at a time, and
2572 @value{GDBN} will reject this command if more than two are used. Delete
2573 or disable unused hardware breakpoints before setting new ones
2574 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2575 @xref{set remote hardware-breakpoint-limit}.
2579 @item thbreak @var{args}
2580 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2581 are the same as for the @code{hbreak} command and the breakpoint is set in
2582 the same way. However, like the @code{tbreak} command,
2583 the breakpoint is automatically deleted after the
2584 first time your program stops there. Also, like the @code{hbreak}
2585 command, the breakpoint requires hardware support and some target hardware
2586 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2587 See also @ref{Conditions, ,Break conditions}.
2590 @cindex regular expression
2591 @item rbreak @var{regex}
2592 Set breakpoints on all functions matching the regular expression
2593 @var{regex}. This command sets an unconditional breakpoint on all
2594 matches, printing a list of all breakpoints it set. Once these
2595 breakpoints are set, they are treated just like the breakpoints set with
2596 the @code{break} command. You can delete them, disable them, or make
2597 them conditional the same way as any other breakpoint.
2599 The syntax of the regular expression is the standard one used with tools
2600 like @file{grep}. Note that this is different from the syntax used by
2601 shells, so for instance @code{foo*} matches all functions that include
2602 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2603 @code{.*} leading and trailing the regular expression you supply, so to
2604 match only functions that begin with @code{foo}, use @code{^foo}.
2606 @cindex non-member C@t{++} functions, set breakpoint in
2607 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2608 breakpoints on overloaded functions that are not members of any special
2611 @cindex set breakpoints on all functions
2612 The @code{rbreak} command can be used to set breakpoints in
2613 @strong{all} the functions in a program, like this:
2616 (@value{GDBP}) rbreak .
2619 @kindex info breakpoints
2620 @cindex @code{$_} and @code{info breakpoints}
2621 @item info breakpoints @r{[}@var{n}@r{]}
2622 @itemx info break @r{[}@var{n}@r{]}
2623 @itemx info watchpoints @r{[}@var{n}@r{]}
2624 Print a table of all breakpoints, watchpoints, and catchpoints set and
2625 not deleted, with the following columns for each breakpoint:
2628 @item Breakpoint Numbers
2630 Breakpoint, watchpoint, or catchpoint.
2632 Whether the breakpoint is marked to be disabled or deleted when hit.
2633 @item Enabled or Disabled
2634 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2635 that are not enabled.
2637 Where the breakpoint is in your program, as a memory address. If the
2638 breakpoint is pending (see below for details) on a future load of a shared library, the address
2639 will be listed as @samp{<PENDING>}.
2641 Where the breakpoint is in the source for your program, as a file and
2642 line number. For a pending breakpoint, the original string passed to
2643 the breakpoint command will be listed as it cannot be resolved until
2644 the appropriate shared library is loaded in the future.
2648 If a breakpoint is conditional, @code{info break} shows the condition on
2649 the line following the affected breakpoint; breakpoint commands, if any,
2650 are listed after that. A pending breakpoint is allowed to have a condition
2651 specified for it. The condition is not parsed for validity until a shared
2652 library is loaded that allows the pending breakpoint to resolve to a
2656 @code{info break} with a breakpoint
2657 number @var{n} as argument lists only that breakpoint. The
2658 convenience variable @code{$_} and the default examining-address for
2659 the @code{x} command are set to the address of the last breakpoint
2660 listed (@pxref{Memory, ,Examining memory}).
2663 @code{info break} displays a count of the number of times the breakpoint
2664 has been hit. This is especially useful in conjunction with the
2665 @code{ignore} command. You can ignore a large number of breakpoint
2666 hits, look at the breakpoint info to see how many times the breakpoint
2667 was hit, and then run again, ignoring one less than that number. This
2668 will get you quickly to the last hit of that breakpoint.
2671 @value{GDBN} allows you to set any number of breakpoints at the same place in
2672 your program. There is nothing silly or meaningless about this. When
2673 the breakpoints are conditional, this is even useful
2674 (@pxref{Conditions, ,Break conditions}).
2676 @cindex pending breakpoints
2677 If a specified breakpoint location cannot be found, it may be due to the fact
2678 that the location is in a shared library that is yet to be loaded. In such
2679 a case, you may want @value{GDBN} to create a special breakpoint (known as
2680 a @dfn{pending breakpoint}) that
2681 attempts to resolve itself in the future when an appropriate shared library
2684 Pending breakpoints are useful to set at the start of your
2685 @value{GDBN} session for locations that you know will be dynamically loaded
2686 later by the program being debugged. When shared libraries are loaded,
2687 a check is made to see if the load resolves any pending breakpoint locations.
2688 If a pending breakpoint location gets resolved,
2689 a regular breakpoint is created and the original pending breakpoint is removed.
2691 @value{GDBN} provides some additional commands for controlling pending
2694 @kindex set breakpoint pending
2695 @kindex show breakpoint pending
2697 @item set breakpoint pending auto
2698 This is the default behavior. When @value{GDBN} cannot find the breakpoint
2699 location, it queries you whether a pending breakpoint should be created.
2701 @item set breakpoint pending on
2702 This indicates that an unrecognized breakpoint location should automatically
2703 result in a pending breakpoint being created.
2705 @item set breakpoint pending off
2706 This indicates that pending breakpoints are not to be created. Any
2707 unrecognized breakpoint location results in an error. This setting does
2708 not affect any pending breakpoints previously created.
2710 @item show breakpoint pending
2711 Show the current behavior setting for creating pending breakpoints.
2714 @cindex operations allowed on pending breakpoints
2715 Normal breakpoint operations apply to pending breakpoints as well. You may
2716 specify a condition for a pending breakpoint and/or commands to run when the
2717 breakpoint is reached. You can also enable or disable
2718 the pending breakpoint. When you specify a condition for a pending breakpoint,
2719 the parsing of the condition will be deferred until the point where the
2720 pending breakpoint location is resolved. Disabling a pending breakpoint
2721 tells @value{GDBN} to not attempt to resolve the breakpoint on any subsequent
2722 shared library load. When a pending breakpoint is re-enabled,
2723 @value{GDBN} checks to see if the location is already resolved.
2724 This is done because any number of shared library loads could have
2725 occurred since the time the breakpoint was disabled and one or more
2726 of these loads could resolve the location.
2728 @cindex negative breakpoint numbers
2729 @cindex internal @value{GDBN} breakpoints
2730 @value{GDBN} itself sometimes sets breakpoints in your program for
2731 special purposes, such as proper handling of @code{longjmp} (in C
2732 programs). These internal breakpoints are assigned negative numbers,
2733 starting with @code{-1}; @samp{info breakpoints} does not display them.
2734 You can see these breakpoints with the @value{GDBN} maintenance command
2735 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
2738 @node Set Watchpoints
2739 @subsection Setting watchpoints
2741 @cindex setting watchpoints
2742 @cindex software watchpoints
2743 @cindex hardware watchpoints
2744 You can use a watchpoint to stop execution whenever the value of an
2745 expression changes, without having to predict a particular place where
2748 Depending on your system, watchpoints may be implemented in software or
2749 hardware. @value{GDBN} does software watchpointing by single-stepping your
2750 program and testing the variable's value each time, which is hundreds of
2751 times slower than normal execution. (But this may still be worth it, to
2752 catch errors where you have no clue what part of your program is the
2755 On some systems, such as HP-UX, @sc{gnu}/Linux and some other x86-based targets,
2756 @value{GDBN} includes support for
2757 hardware watchpoints, which do not slow down the running of your
2762 @item watch @var{expr}
2763 Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
2764 is written into by the program and its value changes.
2767 @item rwatch @var{expr}
2768 Set a watchpoint that will break when watch @var{expr} is read by the program.
2771 @item awatch @var{expr}
2772 Set a watchpoint that will break when @var{expr} is either read or written into
2775 @kindex info watchpoints
2776 @item info watchpoints
2777 This command prints a list of watchpoints, breakpoints, and catchpoints;
2778 it is the same as @code{info break}.
2781 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
2782 watchpoints execute very quickly, and the debugger reports a change in
2783 value at the exact instruction where the change occurs. If @value{GDBN}
2784 cannot set a hardware watchpoint, it sets a software watchpoint, which
2785 executes more slowly and reports the change in value at the next
2786 statement, not the instruction, after the change occurs.
2788 When you issue the @code{watch} command, @value{GDBN} reports
2791 Hardware watchpoint @var{num}: @var{expr}
2795 if it was able to set a hardware watchpoint.
2797 Currently, the @code{awatch} and @code{rwatch} commands can only set
2798 hardware watchpoints, because accesses to data that don't change the
2799 value of the watched expression cannot be detected without examining
2800 every instruction as it is being executed, and @value{GDBN} does not do
2801 that currently. If @value{GDBN} finds that it is unable to set a
2802 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
2803 will print a message like this:
2806 Expression cannot be implemented with read/access watchpoint.
2809 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
2810 data type of the watched expression is wider than what a hardware
2811 watchpoint on the target machine can handle. For example, some systems
2812 can only watch regions that are up to 4 bytes wide; on such systems you
2813 cannot set hardware watchpoints for an expression that yields a
2814 double-precision floating-point number (which is typically 8 bytes
2815 wide). As a work-around, it might be possible to break the large region
2816 into a series of smaller ones and watch them with separate watchpoints.
2818 If you set too many hardware watchpoints, @value{GDBN} might be unable
2819 to insert all of them when you resume the execution of your program.
2820 Since the precise number of active watchpoints is unknown until such
2821 time as the program is about to be resumed, @value{GDBN} might not be
2822 able to warn you about this when you set the watchpoints, and the
2823 warning will be printed only when the program is resumed:
2826 Hardware watchpoint @var{num}: Could not insert watchpoint
2830 If this happens, delete or disable some of the watchpoints.
2832 The SPARClite DSU will generate traps when a program accesses some data
2833 or instruction address that is assigned to the debug registers. For the
2834 data addresses, DSU facilitates the @code{watch} command. However the
2835 hardware breakpoint registers can only take two data watchpoints, and
2836 both watchpoints must be the same kind. For example, you can set two
2837 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
2838 @strong{or} two with @code{awatch} commands, but you cannot set one
2839 watchpoint with one command and the other with a different command.
2840 @value{GDBN} will reject the command if you try to mix watchpoints.
2841 Delete or disable unused watchpoint commands before setting new ones.
2843 If you call a function interactively using @code{print} or @code{call},
2844 any watchpoints you have set will be inactive until @value{GDBN} reaches another
2845 kind of breakpoint or the call completes.
2847 @value{GDBN} automatically deletes watchpoints that watch local
2848 (automatic) variables, or expressions that involve such variables, when
2849 they go out of scope, that is, when the execution leaves the block in
2850 which these variables were defined. In particular, when the program
2851 being debugged terminates, @emph{all} local variables go out of scope,
2852 and so only watchpoints that watch global variables remain set. If you
2853 rerun the program, you will need to set all such watchpoints again. One
2854 way of doing that would be to set a code breakpoint at the entry to the
2855 @code{main} function and when it breaks, set all the watchpoints.
2858 @cindex watchpoints and threads
2859 @cindex threads and watchpoints
2860 @emph{Warning:} In multi-thread programs, watchpoints have only limited
2861 usefulness. With the current watchpoint implementation, @value{GDBN}
2862 can only watch the value of an expression @emph{in a single thread}. If
2863 you are confident that the expression can only change due to the current
2864 thread's activity (and if you are also confident that no other thread
2865 can become current), then you can use watchpoints as usual. However,
2866 @value{GDBN} may not notice when a non-current thread's activity changes
2869 @c FIXME: this is almost identical to the previous paragraph.
2870 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
2871 have only limited usefulness. If @value{GDBN} creates a software
2872 watchpoint, it can only watch the value of an expression @emph{in a
2873 single thread}. If you are confident that the expression can only
2874 change due to the current thread's activity (and if you are also
2875 confident that no other thread can become current), then you can use
2876 software watchpoints as usual. However, @value{GDBN} may not notice
2877 when a non-current thread's activity changes the expression. (Hardware
2878 watchpoints, in contrast, watch an expression in all threads.)
2881 @xref{set remote hardware-watchpoint-limit}.
2883 @node Set Catchpoints
2884 @subsection Setting catchpoints
2885 @cindex catchpoints, setting
2886 @cindex exception handlers
2887 @cindex event handling
2889 You can use @dfn{catchpoints} to cause the debugger to stop for certain
2890 kinds of program events, such as C@t{++} exceptions or the loading of a
2891 shared library. Use the @code{catch} command to set a catchpoint.
2895 @item catch @var{event}
2896 Stop when @var{event} occurs. @var{event} can be any of the following:
2899 @cindex stop on C@t{++} exceptions
2900 The throwing of a C@t{++} exception.
2903 The catching of a C@t{++} exception.
2906 @cindex break on fork/exec
2907 A call to @code{exec}. This is currently only available for HP-UX.
2910 A call to @code{fork}. This is currently only available for HP-UX.
2913 A call to @code{vfork}. This is currently only available for HP-UX.
2916 @itemx load @var{libname}
2917 @cindex break on load/unload of shared library
2918 The dynamic loading of any shared library, or the loading of the library
2919 @var{libname}. This is currently only available for HP-UX.
2922 @itemx unload @var{libname}
2923 The unloading of any dynamically loaded shared library, or the unloading
2924 of the library @var{libname}. This is currently only available for HP-UX.
2927 @item tcatch @var{event}
2928 Set a catchpoint that is enabled only for one stop. The catchpoint is
2929 automatically deleted after the first time the event is caught.
2933 Use the @code{info break} command to list the current catchpoints.
2935 There are currently some limitations to C@t{++} exception handling
2936 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
2940 If you call a function interactively, @value{GDBN} normally returns
2941 control to you when the function has finished executing. If the call
2942 raises an exception, however, the call may bypass the mechanism that
2943 returns control to you and cause your program either to abort or to
2944 simply continue running until it hits a breakpoint, catches a signal
2945 that @value{GDBN} is listening for, or exits. This is the case even if
2946 you set a catchpoint for the exception; catchpoints on exceptions are
2947 disabled within interactive calls.
2950 You cannot raise an exception interactively.
2953 You cannot install an exception handler interactively.
2956 @cindex raise exceptions
2957 Sometimes @code{catch} is not the best way to debug exception handling:
2958 if you need to know exactly where an exception is raised, it is better to
2959 stop @emph{before} the exception handler is called, since that way you
2960 can see the stack before any unwinding takes place. If you set a
2961 breakpoint in an exception handler instead, it may not be easy to find
2962 out where the exception was raised.
2964 To stop just before an exception handler is called, you need some
2965 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
2966 raised by calling a library function named @code{__raise_exception}
2967 which has the following ANSI C interface:
2970 /* @var{addr} is where the exception identifier is stored.
2971 @var{id} is the exception identifier. */
2972 void __raise_exception (void **addr, void *id);
2976 To make the debugger catch all exceptions before any stack
2977 unwinding takes place, set a breakpoint on @code{__raise_exception}
2978 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
2980 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
2981 that depends on the value of @var{id}, you can stop your program when
2982 a specific exception is raised. You can use multiple conditional
2983 breakpoints to stop your program when any of a number of exceptions are
2988 @subsection Deleting breakpoints
2990 @cindex clearing breakpoints, watchpoints, catchpoints
2991 @cindex deleting breakpoints, watchpoints, catchpoints
2992 It is often necessary to eliminate a breakpoint, watchpoint, or
2993 catchpoint once it has done its job and you no longer want your program
2994 to stop there. This is called @dfn{deleting} the breakpoint. A
2995 breakpoint that has been deleted no longer exists; it is forgotten.
2997 With the @code{clear} command you can delete breakpoints according to
2998 where they are in your program. With the @code{delete} command you can
2999 delete individual breakpoints, watchpoints, or catchpoints by specifying
3000 their breakpoint numbers.
3002 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3003 automatically ignores breakpoints on the first instruction to be executed
3004 when you continue execution without changing the execution address.
3009 Delete any breakpoints at the next instruction to be executed in the
3010 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
3011 the innermost frame is selected, this is a good way to delete a
3012 breakpoint where your program just stopped.
3014 @item clear @var{function}
3015 @itemx clear @var{filename}:@var{function}
3016 Delete any breakpoints set at entry to the function @var{function}.
3018 @item clear @var{linenum}
3019 @itemx clear @var{filename}:@var{linenum}
3020 Delete any breakpoints set at or within the code of the specified line.
3022 @cindex delete breakpoints
3024 @kindex d @r{(@code{delete})}
3025 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3026 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3027 ranges specified as arguments. If no argument is specified, delete all
3028 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3029 confirm off}). You can abbreviate this command as @code{d}.
3033 @subsection Disabling breakpoints
3035 @cindex enable/disable a breakpoint
3036 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3037 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3038 it had been deleted, but remembers the information on the breakpoint so
3039 that you can @dfn{enable} it again later.
3041 You disable and enable breakpoints, watchpoints, and catchpoints with
3042 the @code{enable} and @code{disable} commands, optionally specifying one
3043 or more breakpoint numbers as arguments. Use @code{info break} or
3044 @code{info watch} to print a list of breakpoints, watchpoints, and
3045 catchpoints if you do not know which numbers to use.
3047 A breakpoint, watchpoint, or catchpoint can have any of four different
3048 states of enablement:
3052 Enabled. The breakpoint stops your program. A breakpoint set
3053 with the @code{break} command starts out in this state.
3055 Disabled. The breakpoint has no effect on your program.
3057 Enabled once. The breakpoint stops your program, but then becomes
3060 Enabled for deletion. The breakpoint stops your program, but
3061 immediately after it does so it is deleted permanently. A breakpoint
3062 set with the @code{tbreak} command starts out in this state.
3065 You can use the following commands to enable or disable breakpoints,
3066 watchpoints, and catchpoints:
3070 @kindex dis @r{(@code{disable})}
3071 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3072 Disable the specified breakpoints---or all breakpoints, if none are
3073 listed. A disabled breakpoint has no effect but is not forgotten. All
3074 options such as ignore-counts, conditions and commands are remembered in
3075 case the breakpoint is enabled again later. You may abbreviate
3076 @code{disable} as @code{dis}.
3079 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3080 Enable the specified breakpoints (or all defined breakpoints). They
3081 become effective once again in stopping your program.
3083 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3084 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3085 of these breakpoints immediately after stopping your program.
3087 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3088 Enable the specified breakpoints to work once, then die. @value{GDBN}
3089 deletes any of these breakpoints as soon as your program stops there.
3092 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3093 @c confusing: tbreak is also initially enabled.
3094 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3095 ,Setting breakpoints}), breakpoints that you set are initially enabled;
3096 subsequently, they become disabled or enabled only when you use one of
3097 the commands above. (The command @code{until} can set and delete a
3098 breakpoint of its own, but it does not change the state of your other
3099 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3103 @subsection Break conditions
3104 @cindex conditional breakpoints
3105 @cindex breakpoint conditions
3107 @c FIXME what is scope of break condition expr? Context where wanted?
3108 @c in particular for a watchpoint?
3109 The simplest sort of breakpoint breaks every time your program reaches a
3110 specified place. You can also specify a @dfn{condition} for a
3111 breakpoint. A condition is just a Boolean expression in your
3112 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3113 a condition evaluates the expression each time your program reaches it,
3114 and your program stops only if the condition is @emph{true}.
3116 This is the converse of using assertions for program validation; in that
3117 situation, you want to stop when the assertion is violated---that is,
3118 when the condition is false. In C, if you want to test an assertion expressed
3119 by the condition @var{assert}, you should set the condition
3120 @samp{! @var{assert}} on the appropriate breakpoint.
3122 Conditions are also accepted for watchpoints; you may not need them,
3123 since a watchpoint is inspecting the value of an expression anyhow---but
3124 it might be simpler, say, to just set a watchpoint on a variable name,
3125 and specify a condition that tests whether the new value is an interesting
3128 Break conditions can have side effects, and may even call functions in
3129 your program. This can be useful, for example, to activate functions
3130 that log program progress, or to use your own print functions to
3131 format special data structures. The effects are completely predictable
3132 unless there is another enabled breakpoint at the same address. (In
3133 that case, @value{GDBN} might see the other breakpoint first and stop your
3134 program without checking the condition of this one.) Note that
3135 breakpoint commands are usually more convenient and flexible than break
3137 purpose of performing side effects when a breakpoint is reached
3138 (@pxref{Break Commands, ,Breakpoint command lists}).
3140 Break conditions can be specified when a breakpoint is set, by using
3141 @samp{if} in the arguments to the @code{break} command. @xref{Set
3142 Breaks, ,Setting breakpoints}. They can also be changed at any time
3143 with the @code{condition} command.
3145 You can also use the @code{if} keyword with the @code{watch} command.
3146 The @code{catch} command does not recognize the @code{if} keyword;
3147 @code{condition} is the only way to impose a further condition on a
3152 @item condition @var{bnum} @var{expression}
3153 Specify @var{expression} as the break condition for breakpoint,
3154 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3155 breakpoint @var{bnum} stops your program only if the value of
3156 @var{expression} is true (nonzero, in C). When you use
3157 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3158 syntactic correctness, and to determine whether symbols in it have
3159 referents in the context of your breakpoint. If @var{expression} uses
3160 symbols not referenced in the context of the breakpoint, @value{GDBN}
3161 prints an error message:
3164 No symbol "foo" in current context.
3169 not actually evaluate @var{expression} at the time the @code{condition}
3170 command (or a command that sets a breakpoint with a condition, like
3171 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3173 @item condition @var{bnum}
3174 Remove the condition from breakpoint number @var{bnum}. It becomes
3175 an ordinary unconditional breakpoint.
3178 @cindex ignore count (of breakpoint)
3179 A special case of a breakpoint condition is to stop only when the
3180 breakpoint has been reached a certain number of times. This is so
3181 useful that there is a special way to do it, using the @dfn{ignore
3182 count} of the breakpoint. Every breakpoint has an ignore count, which
3183 is an integer. Most of the time, the ignore count is zero, and
3184 therefore has no effect. But if your program reaches a breakpoint whose
3185 ignore count is positive, then instead of stopping, it just decrements
3186 the ignore count by one and continues. As a result, if the ignore count
3187 value is @var{n}, the breakpoint does not stop the next @var{n} times
3188 your program reaches it.
3192 @item ignore @var{bnum} @var{count}
3193 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3194 The next @var{count} times the breakpoint is reached, your program's
3195 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3198 To make the breakpoint stop the next time it is reached, specify
3201 When you use @code{continue} to resume execution of your program from a
3202 breakpoint, you can specify an ignore count directly as an argument to
3203 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3204 Stepping,,Continuing and stepping}.
3206 If a breakpoint has a positive ignore count and a condition, the
3207 condition is not checked. Once the ignore count reaches zero,
3208 @value{GDBN} resumes checking the condition.
3210 You could achieve the effect of the ignore count with a condition such
3211 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3212 is decremented each time. @xref{Convenience Vars, ,Convenience
3216 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3219 @node Break Commands
3220 @subsection Breakpoint command lists
3222 @cindex breakpoint commands
3223 You can give any breakpoint (or watchpoint or catchpoint) a series of
3224 commands to execute when your program stops due to that breakpoint. For
3225 example, you might want to print the values of certain expressions, or
3226 enable other breakpoints.
3231 @item commands @r{[}@var{bnum}@r{]}
3232 @itemx @dots{} @var{command-list} @dots{}
3234 Specify a list of commands for breakpoint number @var{bnum}. The commands
3235 themselves appear on the following lines. Type a line containing just
3236 @code{end} to terminate the commands.
3238 To remove all commands from a breakpoint, type @code{commands} and
3239 follow it immediately with @code{end}; that is, give no commands.
3241 With no @var{bnum} argument, @code{commands} refers to the last
3242 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3243 recently encountered).
3246 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3247 disabled within a @var{command-list}.
3249 You can use breakpoint commands to start your program up again. Simply
3250 use the @code{continue} command, or @code{step}, or any other command
3251 that resumes execution.
3253 Any other commands in the command list, after a command that resumes
3254 execution, are ignored. This is because any time you resume execution
3255 (even with a simple @code{next} or @code{step}), you may encounter
3256 another breakpoint---which could have its own command list, leading to
3257 ambiguities about which list to execute.
3260 If the first command you specify in a command list is @code{silent}, the
3261 usual message about stopping at a breakpoint is not printed. This may
3262 be desirable for breakpoints that are to print a specific message and
3263 then continue. If none of the remaining commands print anything, you
3264 see no sign that the breakpoint was reached. @code{silent} is
3265 meaningful only at the beginning of a breakpoint command list.
3267 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3268 print precisely controlled output, and are often useful in silent
3269 breakpoints. @xref{Output, ,Commands for controlled output}.
3271 For example, here is how you could use breakpoint commands to print the
3272 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3278 printf "x is %d\n",x
3283 One application for breakpoint commands is to compensate for one bug so
3284 you can test for another. Put a breakpoint just after the erroneous line
3285 of code, give it a condition to detect the case in which something
3286 erroneous has been done, and give it commands to assign correct values
3287 to any variables that need them. End with the @code{continue} command
3288 so that your program does not stop, and start with the @code{silent}
3289 command so that no output is produced. Here is an example:
3300 @node Breakpoint Menus
3301 @subsection Breakpoint menus
3303 @cindex symbol overloading
3305 Some programming languages (notably C@t{++} and Objective-C) permit a
3306 single function name
3307 to be defined several times, for application in different contexts.
3308 This is called @dfn{overloading}. When a function name is overloaded,
3309 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3310 a breakpoint. If you realize this is a problem, you can use
3311 something like @samp{break @var{function}(@var{types})} to specify which
3312 particular version of the function you want. Otherwise, @value{GDBN} offers
3313 you a menu of numbered choices for different possible breakpoints, and
3314 waits for your selection with the prompt @samp{>}. The first two
3315 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3316 sets a breakpoint at each definition of @var{function}, and typing
3317 @kbd{0} aborts the @code{break} command without setting any new
3320 For example, the following session excerpt shows an attempt to set a
3321 breakpoint at the overloaded symbol @code{String::after}.
3322 We choose three particular definitions of that function name:
3324 @c FIXME! This is likely to change to show arg type lists, at least
3327 (@value{GDBP}) b String::after
3330 [2] file:String.cc; line number:867
3331 [3] file:String.cc; line number:860
3332 [4] file:String.cc; line number:875
3333 [5] file:String.cc; line number:853
3334 [6] file:String.cc; line number:846
3335 [7] file:String.cc; line number:735
3337 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3338 Breakpoint 2 at 0xb344: file String.cc, line 875.
3339 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3340 Multiple breakpoints were set.
3341 Use the "delete" command to delete unwanted
3347 @c @ifclear BARETARGET
3348 @node Error in Breakpoints
3349 @subsection ``Cannot insert breakpoints''
3351 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3353 Under some operating systems, breakpoints cannot be used in a program if
3354 any other process is running that program. In this situation,
3355 attempting to run or continue a program with a breakpoint causes
3356 @value{GDBN} to print an error message:
3359 Cannot insert breakpoints.
3360 The same program may be running in another process.
3363 When this happens, you have three ways to proceed:
3367 Remove or disable the breakpoints, then continue.
3370 Suspend @value{GDBN}, and copy the file containing your program to a new
3371 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3372 that @value{GDBN} should run your program under that name.
3373 Then start your program again.
3376 Relink your program so that the text segment is nonsharable, using the
3377 linker option @samp{-N}. The operating system limitation may not apply
3378 to nonsharable executables.
3382 A similar message can be printed if you request too many active
3383 hardware-assisted breakpoints and watchpoints:
3385 @c FIXME: the precise wording of this message may change; the relevant
3386 @c source change is not committed yet (Sep 3, 1999).
3388 Stopped; cannot insert breakpoints.
3389 You may have requested too many hardware breakpoints and watchpoints.
3393 This message is printed when you attempt to resume the program, since
3394 only then @value{GDBN} knows exactly how many hardware breakpoints and
3395 watchpoints it needs to insert.
3397 When this message is printed, you need to disable or remove some of the
3398 hardware-assisted breakpoints and watchpoints, and then continue.
3400 @node Breakpoint related warnings
3401 @subsection ``Breakpoint address adjusted...''
3402 @cindex breakpoint address adjusted
3404 Some processor architectures place constraints on the addresses at
3405 which breakpoints may be placed. For architectures thus constrained,
3406 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3407 with the constraints dictated by the architecture.
3409 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3410 a VLIW architecture in which a number of RISC-like instructions may be
3411 bundled together for parallel execution. The FR-V architecture
3412 constrains the location of a breakpoint instruction within such a
3413 bundle to the instruction with the lowest address. @value{GDBN}
3414 honors this constraint by adjusting a breakpoint's address to the
3415 first in the bundle.
3417 It is not uncommon for optimized code to have bundles which contain
3418 instructions from different source statements, thus it may happen that
3419 a breakpoint's address will be adjusted from one source statement to
3420 another. Since this adjustment may significantly alter @value{GDBN}'s
3421 breakpoint related behavior from what the user expects, a warning is
3422 printed when the breakpoint is first set and also when the breakpoint
3425 A warning like the one below is printed when setting a breakpoint
3426 that's been subject to address adjustment:
3429 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3432 Such warnings are printed both for user settable and @value{GDBN}'s
3433 internal breakpoints. If you see one of these warnings, you should
3434 verify that a breakpoint set at the adjusted address will have the
3435 desired affect. If not, the breakpoint in question may be removed and
3436 other breakpoints may be set which will have the desired behavior.
3437 E.g., it may be sufficient to place the breakpoint at a later
3438 instruction. A conditional breakpoint may also be useful in some
3439 cases to prevent the breakpoint from triggering too often.
3441 @value{GDBN} will also issue a warning when stopping at one of these
3442 adjusted breakpoints:
3445 warning: Breakpoint 1 address previously adjusted from 0x00010414
3449 When this warning is encountered, it may be too late to take remedial
3450 action except in cases where the breakpoint is hit earlier or more
3451 frequently than expected.
3453 @node Continuing and Stepping
3454 @section Continuing and stepping
3458 @cindex resuming execution
3459 @dfn{Continuing} means resuming program execution until your program
3460 completes normally. In contrast, @dfn{stepping} means executing just
3461 one more ``step'' of your program, where ``step'' may mean either one
3462 line of source code, or one machine instruction (depending on what
3463 particular command you use). Either when continuing or when stepping,
3464 your program may stop even sooner, due to a breakpoint or a signal. (If
3465 it stops due to a signal, you may want to use @code{handle}, or use
3466 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3470 @kindex c @r{(@code{continue})}
3471 @kindex fg @r{(resume foreground execution)}
3472 @item continue @r{[}@var{ignore-count}@r{]}
3473 @itemx c @r{[}@var{ignore-count}@r{]}
3474 @itemx fg @r{[}@var{ignore-count}@r{]}
3475 Resume program execution, at the address where your program last stopped;
3476 any breakpoints set at that address are bypassed. The optional argument
3477 @var{ignore-count} allows you to specify a further number of times to
3478 ignore a breakpoint at this location; its effect is like that of
3479 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3481 The argument @var{ignore-count} is meaningful only when your program
3482 stopped due to a breakpoint. At other times, the argument to
3483 @code{continue} is ignored.
3485 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3486 debugged program is deemed to be the foreground program) are provided
3487 purely for convenience, and have exactly the same behavior as
3491 To resume execution at a different place, you can use @code{return}
3492 (@pxref{Returning, ,Returning from a function}) to go back to the
3493 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3494 different address}) to go to an arbitrary location in your program.
3496 A typical technique for using stepping is to set a breakpoint
3497 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3498 beginning of the function or the section of your program where a problem
3499 is believed to lie, run your program until it stops at that breakpoint,
3500 and then step through the suspect area, examining the variables that are
3501 interesting, until you see the problem happen.
3505 @kindex s @r{(@code{step})}
3507 Continue running your program until control reaches a different source
3508 line, then stop it and return control to @value{GDBN}. This command is
3509 abbreviated @code{s}.
3512 @c "without debugging information" is imprecise; actually "without line
3513 @c numbers in the debugging information". (gcc -g1 has debugging info but
3514 @c not line numbers). But it seems complex to try to make that
3515 @c distinction here.
3516 @emph{Warning:} If you use the @code{step} command while control is
3517 within a function that was compiled without debugging information,
3518 execution proceeds until control reaches a function that does have
3519 debugging information. Likewise, it will not step into a function which
3520 is compiled without debugging information. To step through functions
3521 without debugging information, use the @code{stepi} command, described
3525 The @code{step} command only stops at the first instruction of a source
3526 line. This prevents the multiple stops that could otherwise occur in
3527 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3528 to stop if a function that has debugging information is called within
3529 the line. In other words, @code{step} @emph{steps inside} any functions
3530 called within the line.
3532 Also, the @code{step} command only enters a function if there is line
3533 number information for the function. Otherwise it acts like the
3534 @code{next} command. This avoids problems when using @code{cc -gl}
3535 on MIPS machines. Previously, @code{step} entered subroutines if there
3536 was any debugging information about the routine.
3538 @item step @var{count}
3539 Continue running as in @code{step}, but do so @var{count} times. If a
3540 breakpoint is reached, or a signal not related to stepping occurs before
3541 @var{count} steps, stepping stops right away.
3544 @kindex n @r{(@code{next})}
3545 @item next @r{[}@var{count}@r{]}
3546 Continue to the next source line in the current (innermost) stack frame.
3547 This is similar to @code{step}, but function calls that appear within
3548 the line of code are executed without stopping. Execution stops when
3549 control reaches a different line of code at the original stack level
3550 that was executing when you gave the @code{next} command. This command
3551 is abbreviated @code{n}.
3553 An argument @var{count} is a repeat count, as for @code{step}.
3556 @c FIX ME!! Do we delete this, or is there a way it fits in with
3557 @c the following paragraph? --- Vctoria
3559 @c @code{next} within a function that lacks debugging information acts like
3560 @c @code{step}, but any function calls appearing within the code of the
3561 @c function are executed without stopping.
3563 The @code{next} command only stops at the first instruction of a
3564 source line. This prevents multiple stops that could otherwise occur in
3565 @code{switch} statements, @code{for} loops, etc.
3567 @kindex set step-mode
3569 @cindex functions without line info, and stepping
3570 @cindex stepping into functions with no line info
3571 @itemx set step-mode on
3572 The @code{set step-mode on} command causes the @code{step} command to
3573 stop at the first instruction of a function which contains no debug line
3574 information rather than stepping over it.
3576 This is useful in cases where you may be interested in inspecting the
3577 machine instructions of a function which has no symbolic info and do not
3578 want @value{GDBN} to automatically skip over this function.
3580 @item set step-mode off
3581 Causes the @code{step} command to step over any functions which contains no
3582 debug information. This is the default.
3586 Continue running until just after function in the selected stack frame
3587 returns. Print the returned value (if any).
3589 Contrast this with the @code{return} command (@pxref{Returning,
3590 ,Returning from a function}).
3593 @kindex u @r{(@code{until})}
3596 Continue running until a source line past the current line, in the
3597 current stack frame, is reached. This command is used to avoid single
3598 stepping through a loop more than once. It is like the @code{next}
3599 command, except that when @code{until} encounters a jump, it
3600 automatically continues execution until the program counter is greater
3601 than the address of the jump.
3603 This means that when you reach the end of a loop after single stepping
3604 though it, @code{until} makes your program continue execution until it
3605 exits the loop. In contrast, a @code{next} command at the end of a loop
3606 simply steps back to the beginning of the loop, which forces you to step
3607 through the next iteration.
3609 @code{until} always stops your program if it attempts to exit the current
3612 @code{until} may produce somewhat counterintuitive results if the order
3613 of machine code does not match the order of the source lines. For
3614 example, in the following excerpt from a debugging session, the @code{f}
3615 (@code{frame}) command shows that execution is stopped at line
3616 @code{206}; yet when we use @code{until}, we get to line @code{195}:
3620 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
3622 (@value{GDBP}) until
3623 195 for ( ; argc > 0; NEXTARG) @{
3626 This happened because, for execution efficiency, the compiler had
3627 generated code for the loop closure test at the end, rather than the
3628 start, of the loop---even though the test in a C @code{for}-loop is
3629 written before the body of the loop. The @code{until} command appeared
3630 to step back to the beginning of the loop when it advanced to this
3631 expression; however, it has not really gone to an earlier
3632 statement---not in terms of the actual machine code.
3634 @code{until} with no argument works by means of single
3635 instruction stepping, and hence is slower than @code{until} with an
3638 @item until @var{location}
3639 @itemx u @var{location}
3640 Continue running your program until either the specified location is
3641 reached, or the current stack frame returns. @var{location} is any of
3642 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
3643 ,Setting breakpoints}). This form of the command uses breakpoints, and
3644 hence is quicker than @code{until} without an argument. The specified
3645 location is actually reached only if it is in the current frame. This
3646 implies that @code{until} can be used to skip over recursive function
3647 invocations. For instance in the code below, if the current location is
3648 line @code{96}, issuing @code{until 99} will execute the program up to
3649 line @code{99} in the same invocation of factorial, i.e. after the inner
3650 invocations have returned.
3653 94 int factorial (int value)
3655 96 if (value > 1) @{
3656 97 value *= factorial (value - 1);
3663 @kindex advance @var{location}
3664 @itemx advance @var{location}
3665 Continue running the program up to the given location. An argument is
3666 required, anything of the same form as arguments for the @code{break}
3667 command. Execution will also stop upon exit from the current stack
3668 frame. This command is similar to @code{until}, but @code{advance} will
3669 not skip over recursive function calls, and the target location doesn't
3670 have to be in the same frame as the current one.
3674 @kindex si @r{(@code{stepi})}
3676 @itemx stepi @var{arg}
3678 Execute one machine instruction, then stop and return to the debugger.
3680 It is often useful to do @samp{display/i $pc} when stepping by machine
3681 instructions. This makes @value{GDBN} automatically display the next
3682 instruction to be executed, each time your program stops. @xref{Auto
3683 Display,, Automatic display}.
3685 An argument is a repeat count, as in @code{step}.
3689 @kindex ni @r{(@code{nexti})}
3691 @itemx nexti @var{arg}
3693 Execute one machine instruction, but if it is a function call,
3694 proceed until the function returns.
3696 An argument is a repeat count, as in @code{next}.
3703 A signal is an asynchronous event that can happen in a program. The
3704 operating system defines the possible kinds of signals, and gives each
3705 kind a name and a number. For example, in Unix @code{SIGINT} is the
3706 signal a program gets when you type an interrupt character (often @kbd{C-c});
3707 @code{SIGSEGV} is the signal a program gets from referencing a place in
3708 memory far away from all the areas in use; @code{SIGALRM} occurs when
3709 the alarm clock timer goes off (which happens only if your program has
3710 requested an alarm).
3712 @cindex fatal signals
3713 Some signals, including @code{SIGALRM}, are a normal part of the
3714 functioning of your program. Others, such as @code{SIGSEGV}, indicate
3715 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
3716 program has not specified in advance some other way to handle the signal.
3717 @code{SIGINT} does not indicate an error in your program, but it is normally
3718 fatal so it can carry out the purpose of the interrupt: to kill the program.
3720 @value{GDBN} has the ability to detect any occurrence of a signal in your
3721 program. You can tell @value{GDBN} in advance what to do for each kind of
3724 @cindex handling signals
3725 Normally, @value{GDBN} is set up to let the non-erroneous signals like
3726 @code{SIGALRM} be silently passed to your program
3727 (so as not to interfere with their role in the program's functioning)
3728 but to stop your program immediately whenever an error signal happens.
3729 You can change these settings with the @code{handle} command.
3732 @kindex info signals
3735 Print a table of all the kinds of signals and how @value{GDBN} has been told to
3736 handle each one. You can use this to see the signal numbers of all
3737 the defined types of signals.
3739 @code{info handle} is an alias for @code{info signals}.
3742 @item handle @var{signal} @var{keywords}@dots{}
3743 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
3744 can be the number of a signal or its name (with or without the
3745 @samp{SIG} at the beginning); a list of signal numbers of the form
3746 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
3747 known signals. The @var{keywords} say what change to make.
3751 The keywords allowed by the @code{handle} command can be abbreviated.
3752 Their full names are:
3756 @value{GDBN} should not stop your program when this signal happens. It may
3757 still print a message telling you that the signal has come in.
3760 @value{GDBN} should stop your program when this signal happens. This implies
3761 the @code{print} keyword as well.
3764 @value{GDBN} should print a message when this signal happens.
3767 @value{GDBN} should not mention the occurrence of the signal at all. This
3768 implies the @code{nostop} keyword as well.
3772 @value{GDBN} should allow your program to see this signal; your program
3773 can handle the signal, or else it may terminate if the signal is fatal
3774 and not handled. @code{pass} and @code{noignore} are synonyms.
3778 @value{GDBN} should not allow your program to see this signal.
3779 @code{nopass} and @code{ignore} are synonyms.
3783 When a signal stops your program, the signal is not visible to the
3785 continue. Your program sees the signal then, if @code{pass} is in
3786 effect for the signal in question @emph{at that time}. In other words,
3787 after @value{GDBN} reports a signal, you can use the @code{handle}
3788 command with @code{pass} or @code{nopass} to control whether your
3789 program sees that signal when you continue.
3791 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
3792 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
3793 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
3796 You can also use the @code{signal} command to prevent your program from
3797 seeing a signal, or cause it to see a signal it normally would not see,
3798 or to give it any signal at any time. For example, if your program stopped
3799 due to some sort of memory reference error, you might store correct
3800 values into the erroneous variables and continue, hoping to see more
3801 execution; but your program would probably terminate immediately as
3802 a result of the fatal signal once it saw the signal. To prevent this,
3803 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
3807 @section Stopping and starting multi-thread programs
3809 When your program has multiple threads (@pxref{Threads,, Debugging
3810 programs with multiple threads}), you can choose whether to set
3811 breakpoints on all threads, or on a particular thread.
3814 @cindex breakpoints and threads
3815 @cindex thread breakpoints
3816 @kindex break @dots{} thread @var{threadno}
3817 @item break @var{linespec} thread @var{threadno}
3818 @itemx break @var{linespec} thread @var{threadno} if @dots{}
3819 @var{linespec} specifies source lines; there are several ways of
3820 writing them, but the effect is always to specify some source line.
3822 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
3823 to specify that you only want @value{GDBN} to stop the program when a
3824 particular thread reaches this breakpoint. @var{threadno} is one of the
3825 numeric thread identifiers assigned by @value{GDBN}, shown in the first
3826 column of the @samp{info threads} display.
3828 If you do not specify @samp{thread @var{threadno}} when you set a
3829 breakpoint, the breakpoint applies to @emph{all} threads of your
3832 You can use the @code{thread} qualifier on conditional breakpoints as
3833 well; in this case, place @samp{thread @var{threadno}} before the
3834 breakpoint condition, like this:
3837 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
3842 @cindex stopped threads
3843 @cindex threads, stopped
3844 Whenever your program stops under @value{GDBN} for any reason,
3845 @emph{all} threads of execution stop, not just the current thread. This
3846 allows you to examine the overall state of the program, including
3847 switching between threads, without worrying that things may change
3850 @cindex thread breakpoints and system calls
3851 @cindex system calls and thread breakpoints
3852 @cindex premature return from system calls
3853 There is an unfortunate side effect. If one thread stops for a
3854 breakpoint, or for some other reason, and another thread is blocked in a
3855 system call, then the system call may return prematurely. This is a
3856 consequence of the interaction between multiple threads and the signals
3857 that @value{GDBN} uses to implement breakpoints and other events that
3860 To handle this problem, your program should check the return value of
3861 each system call and react appropriately. This is good programming
3864 For example, do not write code like this:
3870 The call to @code{sleep} will return early if a different thread stops
3871 at a breakpoint or for some other reason.
3873 Instead, write this:
3878 unslept = sleep (unslept);
3881 A system call is allowed to return early, so the system is still
3882 conforming to its specification. But @value{GDBN} does cause your
3883 multi-threaded program to behave differently than it would without
3886 Also, @value{GDBN} uses internal breakpoints in the thread library to
3887 monitor certain events such as thread creation and thread destruction.
3888 When such an event happens, a system call in another thread may return
3889 prematurely, even though your program does not appear to stop.
3891 @cindex continuing threads
3892 @cindex threads, continuing
3893 Conversely, whenever you restart the program, @emph{all} threads start
3894 executing. @emph{This is true even when single-stepping} with commands
3895 like @code{step} or @code{next}.
3897 In particular, @value{GDBN} cannot single-step all threads in lockstep.
3898 Since thread scheduling is up to your debugging target's operating
3899 system (not controlled by @value{GDBN}), other threads may
3900 execute more than one statement while the current thread completes a
3901 single step. Moreover, in general other threads stop in the middle of a
3902 statement, rather than at a clean statement boundary, when the program
3905 You might even find your program stopped in another thread after
3906 continuing or even single-stepping. This happens whenever some other
3907 thread runs into a breakpoint, a signal, or an exception before the
3908 first thread completes whatever you requested.
3910 On some OSes, you can lock the OS scheduler and thus allow only a single
3914 @item set scheduler-locking @var{mode}
3915 Set the scheduler locking mode. If it is @code{off}, then there is no
3916 locking and any thread may run at any time. If @code{on}, then only the
3917 current thread may run when the inferior is resumed. The @code{step}
3918 mode optimizes for single-stepping. It stops other threads from
3919 ``seizing the prompt'' by preempting the current thread while you are
3920 stepping. Other threads will only rarely (or never) get a chance to run
3921 when you step. They are more likely to run when you @samp{next} over a
3922 function call, and they are completely free to run when you use commands
3923 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
3924 thread hits a breakpoint during its timeslice, they will never steal the
3925 @value{GDBN} prompt away from the thread that you are debugging.
3927 @item show scheduler-locking
3928 Display the current scheduler locking mode.
3933 @chapter Examining the Stack
3935 When your program has stopped, the first thing you need to know is where it
3936 stopped and how it got there.
3939 Each time your program performs a function call, information about the call
3941 That information includes the location of the call in your program,
3942 the arguments of the call,
3943 and the local variables of the function being called.
3944 The information is saved in a block of data called a @dfn{stack frame}.
3945 The stack frames are allocated in a region of memory called the @dfn{call
3948 When your program stops, the @value{GDBN} commands for examining the
3949 stack allow you to see all of this information.
3951 @cindex selected frame
3952 One of the stack frames is @dfn{selected} by @value{GDBN} and many
3953 @value{GDBN} commands refer implicitly to the selected frame. In
3954 particular, whenever you ask @value{GDBN} for the value of a variable in
3955 your program, the value is found in the selected frame. There are
3956 special @value{GDBN} commands to select whichever frame you are
3957 interested in. @xref{Selection, ,Selecting a frame}.
3959 When your program stops, @value{GDBN} automatically selects the
3960 currently executing frame and describes it briefly, similar to the
3961 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
3964 * Frames:: Stack frames
3965 * Backtrace:: Backtraces
3966 * Selection:: Selecting a frame
3967 * Frame Info:: Information on a frame
3972 @section Stack frames
3974 @cindex frame, definition
3976 The call stack is divided up into contiguous pieces called @dfn{stack
3977 frames}, or @dfn{frames} for short; each frame is the data associated
3978 with one call to one function. The frame contains the arguments given
3979 to the function, the function's local variables, and the address at
3980 which the function is executing.
3982 @cindex initial frame
3983 @cindex outermost frame
3984 @cindex innermost frame
3985 When your program is started, the stack has only one frame, that of the
3986 function @code{main}. This is called the @dfn{initial} frame or the
3987 @dfn{outermost} frame. Each time a function is called, a new frame is
3988 made. Each time a function returns, the frame for that function invocation
3989 is eliminated. If a function is recursive, there can be many frames for
3990 the same function. The frame for the function in which execution is
3991 actually occurring is called the @dfn{innermost} frame. This is the most
3992 recently created of all the stack frames that still exist.
3994 @cindex frame pointer
3995 Inside your program, stack frames are identified by their addresses. A
3996 stack frame consists of many bytes, each of which has its own address; each
3997 kind of computer has a convention for choosing one byte whose
3998 address serves as the address of the frame. Usually this address is kept
3999 in a register called the @dfn{frame pointer register} while execution is
4000 going on in that frame.
4002 @cindex frame number
4003 @value{GDBN} assigns numbers to all existing stack frames, starting with
4004 zero for the innermost frame, one for the frame that called it,
4005 and so on upward. These numbers do not really exist in your program;
4006 they are assigned by @value{GDBN} to give you a way of designating stack
4007 frames in @value{GDBN} commands.
4009 @c The -fomit-frame-pointer below perennially causes hbox overflow
4010 @c underflow problems.
4011 @cindex frameless execution
4012 Some compilers provide a way to compile functions so that they operate
4013 without stack frames. (For example, the @value{GCC} option
4015 @samp{-fomit-frame-pointer}
4017 generates functions without a frame.)
4018 This is occasionally done with heavily used library functions to save
4019 the frame setup time. @value{GDBN} has limited facilities for dealing
4020 with these function invocations. If the innermost function invocation
4021 has no stack frame, @value{GDBN} nevertheless regards it as though
4022 it had a separate frame, which is numbered zero as usual, allowing
4023 correct tracing of the function call chain. However, @value{GDBN} has
4024 no provision for frameless functions elsewhere in the stack.
4027 @kindex frame@r{, command}
4028 @cindex current stack frame
4029 @item frame @var{args}
4030 The @code{frame} command allows you to move from one stack frame to another,
4031 and to print the stack frame you select. @var{args} may be either the
4032 address of the frame or the stack frame number. Without an argument,
4033 @code{frame} prints the current stack frame.
4035 @kindex select-frame
4036 @cindex selecting frame silently
4038 The @code{select-frame} command allows you to move from one stack frame
4039 to another without printing the frame. This is the silent version of
4048 @cindex stack traces
4049 A backtrace is a summary of how your program got where it is. It shows one
4050 line per frame, for many frames, starting with the currently executing
4051 frame (frame zero), followed by its caller (frame one), and on up the
4056 @kindex bt @r{(@code{backtrace})}
4059 Print a backtrace of the entire stack: one line per frame for all
4060 frames in the stack.
4062 You can stop the backtrace at any time by typing the system interrupt
4063 character, normally @kbd{C-c}.
4065 @item backtrace @var{n}
4067 Similar, but print only the innermost @var{n} frames.
4069 @item backtrace -@var{n}
4071 Similar, but print only the outermost @var{n} frames.
4076 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4077 are additional aliases for @code{backtrace}.
4079 Each line in the backtrace shows the frame number and the function name.
4080 The program counter value is also shown---unless you use @code{set
4081 print address off}. The backtrace also shows the source file name and
4082 line number, as well as the arguments to the function. The program
4083 counter value is omitted if it is at the beginning of the code for that
4086 Here is an example of a backtrace. It was made with the command
4087 @samp{bt 3}, so it shows the innermost three frames.
4091 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4093 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4094 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4096 (More stack frames follow...)
4101 The display for frame zero does not begin with a program counter
4102 value, indicating that your program has stopped at the beginning of the
4103 code for line @code{993} of @code{builtin.c}.
4105 Most programs have a standard user entry point---a place where system
4106 libraries and startup code transition into user code. For C this is
4107 @code{main}. When @value{GDBN} finds the entry function in a backtrace
4108 it will terminate the backtrace, to avoid tracing into highly
4109 system-specific (and generally uninteresting) code.
4111 If you need to examine the startup code, or limit the number of levels
4112 in a backtrace, you can change this behavior:
4115 @item set backtrace past-main
4116 @itemx set backtrace past-main on
4117 @kindex set backtrace
4118 Backtraces will continue past the user entry point.
4120 @item set backtrace past-main off
4121 Backtraces will stop when they encounter the user entry point. This is the
4124 @item show backtrace past-main
4125 @kindex show backtrace
4126 Display the current user entry point backtrace policy.
4128 @item set backtrace past-entry
4129 @itemx set backtrace past-entry on
4130 Backtraces will continue past the internal entry point of an application.
4131 This entry point is encoded by the linker when the application is built,
4132 and is likely before the user entry point @code{main} (or equivalent) is called.
4134 @item set backtrace past-entry off
4135 Backtraces will stop when they encouter the internal entry point of an
4136 application. This is the default.
4138 @item show backtrace past-entry
4139 Display the current internal entry point backtrace policy.
4141 @item set backtrace limit @var{n}
4142 @itemx set backtrace limit 0
4143 @cindex backtrace limit
4144 Limit the backtrace to @var{n} levels. A value of zero means
4147 @item show backtrace limit
4148 Display the current limit on backtrace levels.
4152 @section Selecting a frame
4154 Most commands for examining the stack and other data in your program work on
4155 whichever stack frame is selected at the moment. Here are the commands for
4156 selecting a stack frame; all of them finish by printing a brief description
4157 of the stack frame just selected.
4160 @kindex frame@r{, selecting}
4161 @kindex f @r{(@code{frame})}
4164 Select frame number @var{n}. Recall that frame zero is the innermost
4165 (currently executing) frame, frame one is the frame that called the
4166 innermost one, and so on. The highest-numbered frame is the one for
4169 @item frame @var{addr}
4171 Select the frame at address @var{addr}. This is useful mainly if the
4172 chaining of stack frames has been damaged by a bug, making it
4173 impossible for @value{GDBN} to assign numbers properly to all frames. In
4174 addition, this can be useful when your program has multiple stacks and
4175 switches between them.
4177 On the SPARC architecture, @code{frame} needs two addresses to
4178 select an arbitrary frame: a frame pointer and a stack pointer.
4180 On the MIPS and Alpha architecture, it needs two addresses: a stack
4181 pointer and a program counter.
4183 On the 29k architecture, it needs three addresses: a register stack
4184 pointer, a program counter, and a memory stack pointer.
4185 @c note to future updaters: this is conditioned on a flag
4186 @c SETUP_ARBITRARY_FRAME in the tm-*.h files. The above is up to date
4187 @c as of 27 Jan 1994.
4191 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4192 advances toward the outermost frame, to higher frame numbers, to frames
4193 that have existed longer. @var{n} defaults to one.
4196 @kindex do @r{(@code{down})}
4198 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4199 advances toward the innermost frame, to lower frame numbers, to frames
4200 that were created more recently. @var{n} defaults to one. You may
4201 abbreviate @code{down} as @code{do}.
4204 All of these commands end by printing two lines of output describing the
4205 frame. The first line shows the frame number, the function name, the
4206 arguments, and the source file and line number of execution in that
4207 frame. The second line shows the text of that source line.
4215 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4217 10 read_input_file (argv[i]);
4221 After such a printout, the @code{list} command with no arguments
4222 prints ten lines centered on the point of execution in the frame.
4223 You can also edit the program at the point of execution with your favorite
4224 editing program by typing @code{edit}.
4225 @xref{List, ,Printing source lines},
4229 @kindex down-silently
4231 @item up-silently @var{n}
4232 @itemx down-silently @var{n}
4233 These two commands are variants of @code{up} and @code{down},
4234 respectively; they differ in that they do their work silently, without
4235 causing display of the new frame. They are intended primarily for use
4236 in @value{GDBN} command scripts, where the output might be unnecessary and
4241 @section Information about a frame
4243 There are several other commands to print information about the selected
4249 When used without any argument, this command does not change which
4250 frame is selected, but prints a brief description of the currently
4251 selected stack frame. It can be abbreviated @code{f}. With an
4252 argument, this command is used to select a stack frame.
4253 @xref{Selection, ,Selecting a frame}.
4256 @kindex info f @r{(@code{info frame})}
4259 This command prints a verbose description of the selected stack frame,
4264 the address of the frame
4266 the address of the next frame down (called by this frame)
4268 the address of the next frame up (caller of this frame)
4270 the language in which the source code corresponding to this frame is written
4272 the address of the frame's arguments
4274 the address of the frame's local variables
4276 the program counter saved in it (the address of execution in the caller frame)
4278 which registers were saved in the frame
4281 @noindent The verbose description is useful when
4282 something has gone wrong that has made the stack format fail to fit
4283 the usual conventions.
4285 @item info frame @var{addr}
4286 @itemx info f @var{addr}
4287 Print a verbose description of the frame at address @var{addr}, without
4288 selecting that frame. The selected frame remains unchanged by this
4289 command. This requires the same kind of address (more than one for some
4290 architectures) that you specify in the @code{frame} command.
4291 @xref{Selection, ,Selecting a frame}.
4295 Print the arguments of the selected frame, each on a separate line.
4299 Print the local variables of the selected frame, each on a separate
4300 line. These are all variables (declared either static or automatic)
4301 accessible at the point of execution of the selected frame.
4304 @cindex catch exceptions, list active handlers
4305 @cindex exception handlers, how to list
4307 Print a list of all the exception handlers that are active in the
4308 current stack frame at the current point of execution. To see other
4309 exception handlers, visit the associated frame (using the @code{up},
4310 @code{down}, or @code{frame} commands); then type @code{info catch}.
4311 @xref{Set Catchpoints, , Setting catchpoints}.
4317 @chapter Examining Source Files
4319 @value{GDBN} can print parts of your program's source, since the debugging
4320 information recorded in the program tells @value{GDBN} what source files were
4321 used to build it. When your program stops, @value{GDBN} spontaneously prints
4322 the line where it stopped. Likewise, when you select a stack frame
4323 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4324 execution in that frame has stopped. You can print other portions of
4325 source files by explicit command.
4327 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4328 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4329 @value{GDBN} under @sc{gnu} Emacs}.
4332 * List:: Printing source lines
4333 * Edit:: Editing source files
4334 * Search:: Searching source files
4335 * Source Path:: Specifying source directories
4336 * Machine Code:: Source and machine code
4340 @section Printing source lines
4343 @kindex l @r{(@code{list})}
4344 To print lines from a source file, use the @code{list} command
4345 (abbreviated @code{l}). By default, ten lines are printed.
4346 There are several ways to specify what part of the file you want to print.
4348 Here are the forms of the @code{list} command most commonly used:
4351 @item list @var{linenum}
4352 Print lines centered around line number @var{linenum} in the
4353 current source file.
4355 @item list @var{function}
4356 Print lines centered around the beginning of function
4360 Print more lines. If the last lines printed were printed with a
4361 @code{list} command, this prints lines following the last lines
4362 printed; however, if the last line printed was a solitary line printed
4363 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4364 Stack}), this prints lines centered around that line.
4367 Print lines just before the lines last printed.
4370 By default, @value{GDBN} prints ten source lines with any of these forms of
4371 the @code{list} command. You can change this using @code{set listsize}:
4374 @kindex set listsize
4375 @item set listsize @var{count}
4376 Make the @code{list} command display @var{count} source lines (unless
4377 the @code{list} argument explicitly specifies some other number).
4379 @kindex show listsize
4381 Display the number of lines that @code{list} prints.
4384 Repeating a @code{list} command with @key{RET} discards the argument,
4385 so it is equivalent to typing just @code{list}. This is more useful
4386 than listing the same lines again. An exception is made for an
4387 argument of @samp{-}; that argument is preserved in repetition so that
4388 each repetition moves up in the source file.
4391 In general, the @code{list} command expects you to supply zero, one or two
4392 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4393 of writing them, but the effect is always to specify some source line.
4394 Here is a complete description of the possible arguments for @code{list}:
4397 @item list @var{linespec}
4398 Print lines centered around the line specified by @var{linespec}.
4400 @item list @var{first},@var{last}
4401 Print lines from @var{first} to @var{last}. Both arguments are
4404 @item list ,@var{last}
4405 Print lines ending with @var{last}.
4407 @item list @var{first},
4408 Print lines starting with @var{first}.
4411 Print lines just after the lines last printed.
4414 Print lines just before the lines last printed.
4417 As described in the preceding table.
4420 Here are the ways of specifying a single source line---all the
4425 Specifies line @var{number} of the current source file.
4426 When a @code{list} command has two linespecs, this refers to
4427 the same source file as the first linespec.
4430 Specifies the line @var{offset} lines after the last line printed.
4431 When used as the second linespec in a @code{list} command that has
4432 two, this specifies the line @var{offset} lines down from the
4436 Specifies the line @var{offset} lines before the last line printed.
4438 @item @var{filename}:@var{number}
4439 Specifies line @var{number} in the source file @var{filename}.
4441 @item @var{function}
4442 Specifies the line that begins the body of the function @var{function}.
4443 For example: in C, this is the line with the open brace.
4445 @item @var{filename}:@var{function}
4446 Specifies the line of the open-brace that begins the body of the
4447 function @var{function} in the file @var{filename}. You only need the
4448 file name with a function name to avoid ambiguity when there are
4449 identically named functions in different source files.
4451 @item *@var{address}
4452 Specifies the line containing the program address @var{address}.
4453 @var{address} may be any expression.
4457 @section Editing source files
4458 @cindex editing source files
4461 @kindex e @r{(@code{edit})}
4462 To edit the lines in a source file, use the @code{edit} command.
4463 The editing program of your choice
4464 is invoked with the current line set to
4465 the active line in the program.
4466 Alternatively, there are several ways to specify what part of the file you
4467 want to print if you want to see other parts of the program.
4469 Here are the forms of the @code{edit} command most commonly used:
4473 Edit the current source file at the active line number in the program.
4475 @item edit @var{number}
4476 Edit the current source file with @var{number} as the active line number.
4478 @item edit @var{function}
4479 Edit the file containing @var{function} at the beginning of its definition.
4481 @item edit @var{filename}:@var{number}
4482 Specifies line @var{number} in the source file @var{filename}.
4484 @item edit @var{filename}:@var{function}
4485 Specifies the line that begins the body of the
4486 function @var{function} in the file @var{filename}. You only need the
4487 file name with a function name to avoid ambiguity when there are
4488 identically named functions in different source files.
4490 @item edit *@var{address}
4491 Specifies the line containing the program address @var{address}.
4492 @var{address} may be any expression.
4495 @subsection Choosing your editor
4496 You can customize @value{GDBN} to use any editor you want
4498 The only restriction is that your editor (say @code{ex}), recognizes the
4499 following command-line syntax:
4501 ex +@var{number} file
4503 The optional numeric value +@var{number} specifies the number of the line in
4504 the file where to start editing.}.
4505 By default, it is @file{@value{EDITOR}}, but you can change this
4506 by setting the environment variable @code{EDITOR} before using
4507 @value{GDBN}. For example, to configure @value{GDBN} to use the
4508 @code{vi} editor, you could use these commands with the @code{sh} shell:
4514 or in the @code{csh} shell,
4516 setenv EDITOR /usr/bin/vi
4521 @section Searching source files
4522 @cindex searching source files
4523 @kindex reverse-search
4525 There are two commands for searching through the current source file for a
4530 @kindex forward-search
4531 @item forward-search @var{regexp}
4532 @itemx search @var{regexp}
4533 The command @samp{forward-search @var{regexp}} checks each line,
4534 starting with the one following the last line listed, for a match for
4535 @var{regexp}. It lists the line that is found. You can use the
4536 synonym @samp{search @var{regexp}} or abbreviate the command name as
4539 @item reverse-search @var{regexp}
4540 The command @samp{reverse-search @var{regexp}} checks each line, starting
4541 with the one before the last line listed and going backward, for a match
4542 for @var{regexp}. It lists the line that is found. You can abbreviate
4543 this command as @code{rev}.
4547 @section Specifying source directories
4550 @cindex directories for source files
4551 Executable programs sometimes do not record the directories of the source
4552 files from which they were compiled, just the names. Even when they do,
4553 the directories could be moved between the compilation and your debugging
4554 session. @value{GDBN} has a list of directories to search for source files;
4555 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
4556 it tries all the directories in the list, in the order they are present
4557 in the list, until it finds a file with the desired name.
4559 For example, suppose an executable references the file
4560 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
4561 @file{/mnt/cross}. The file is first looked up literally; if this
4562 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
4563 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
4564 message is printed. @value{GDBN} does not look up the parts of the
4565 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
4566 Likewise, the subdirectories of the source path are not searched: if
4567 the source path is @file{/mnt/cross}, and the binary refers to
4568 @file{foo.c}, @value{GDBN} would not find it under
4569 @file{/mnt/cross/usr/src/foo-1.0/lib}.
4571 Plain file names, relative file names with leading directories, file
4572 names containing dots, etc.@: are all treated as described above; for
4573 instance, if the source path is @file{/mnt/cross}, and the source file
4574 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
4575 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
4576 that---@file{/mnt/cross/foo.c}.
4578 Note that the executable search path is @emph{not} used to locate the
4579 source files. Neither is the current working directory, unless it
4580 happens to be in the source path.
4582 Whenever you reset or rearrange the source path, @value{GDBN} clears out
4583 any information it has cached about where source files are found and where
4584 each line is in the file.
4588 When you start @value{GDBN}, its source path includes only @samp{cdir}
4589 and @samp{cwd}, in that order.
4590 To add other directories, use the @code{directory} command.
4593 @item directory @var{dirname} @dots{}
4594 @item dir @var{dirname} @dots{}
4595 Add directory @var{dirname} to the front of the source path. Several
4596 directory names may be given to this command, separated by @samp{:}
4597 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
4598 part of absolute file names) or
4599 whitespace. You may specify a directory that is already in the source
4600 path; this moves it forward, so @value{GDBN} searches it sooner.
4604 @vindex $cdir@r{, convenience variable}
4605 @vindex $cwdr@r{, convenience variable}
4606 @cindex compilation directory
4607 @cindex current directory
4608 @cindex working directory
4609 @cindex directory, current
4610 @cindex directory, compilation
4611 You can use the string @samp{$cdir} to refer to the compilation
4612 directory (if one is recorded), and @samp{$cwd} to refer to the current
4613 working directory. @samp{$cwd} is not the same as @samp{.}---the former
4614 tracks the current working directory as it changes during your @value{GDBN}
4615 session, while the latter is immediately expanded to the current
4616 directory at the time you add an entry to the source path.
4619 Reset the source path to empty again. This requires confirmation.
4621 @c RET-repeat for @code{directory} is explicitly disabled, but since
4622 @c repeating it would be a no-op we do not say that. (thanks to RMS)
4624 @item show directories
4625 @kindex show directories
4626 Print the source path: show which directories it contains.
4629 If your source path is cluttered with directories that are no longer of
4630 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
4631 versions of source. You can correct the situation as follows:
4635 Use @code{directory} with no argument to reset the source path to empty.
4638 Use @code{directory} with suitable arguments to reinstall the
4639 directories you want in the source path. You can add all the
4640 directories in one command.
4644 @section Source and machine code
4645 @cindex source line and its code address
4647 You can use the command @code{info line} to map source lines to program
4648 addresses (and vice versa), and the command @code{disassemble} to display
4649 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
4650 mode, the @code{info line} command causes the arrow to point to the
4651 line specified. Also, @code{info line} prints addresses in symbolic form as
4656 @item info line @var{linespec}
4657 Print the starting and ending addresses of the compiled code for
4658 source line @var{linespec}. You can specify source lines in any of
4659 the ways understood by the @code{list} command (@pxref{List, ,Printing
4663 For example, we can use @code{info line} to discover the location of
4664 the object code for the first line of function
4665 @code{m4_changequote}:
4667 @c FIXME: I think this example should also show the addresses in
4668 @c symbolic form, as they usually would be displayed.
4670 (@value{GDBP}) info line m4_changequote
4671 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
4675 @cindex code address and its source line
4676 We can also inquire (using @code{*@var{addr}} as the form for
4677 @var{linespec}) what source line covers a particular address:
4679 (@value{GDBP}) info line *0x63ff
4680 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
4683 @cindex @code{$_} and @code{info line}
4684 @cindex @code{x} command, default address
4685 @kindex x@r{(examine), and} info line
4686 After @code{info line}, the default address for the @code{x} command
4687 is changed to the starting address of the line, so that @samp{x/i} is
4688 sufficient to begin examining the machine code (@pxref{Memory,
4689 ,Examining memory}). Also, this address is saved as the value of the
4690 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
4695 @cindex assembly instructions
4696 @cindex instructions, assembly
4697 @cindex machine instructions
4698 @cindex listing machine instructions
4700 This specialized command dumps a range of memory as machine
4701 instructions. The default memory range is the function surrounding the
4702 program counter of the selected frame. A single argument to this
4703 command is a program counter value; @value{GDBN} dumps the function
4704 surrounding this value. Two arguments specify a range of addresses
4705 (first inclusive, second exclusive) to dump.
4708 The following example shows the disassembly of a range of addresses of
4709 HP PA-RISC 2.0 code:
4712 (@value{GDBP}) disas 0x32c4 0x32e4
4713 Dump of assembler code from 0x32c4 to 0x32e4:
4714 0x32c4 <main+204>: addil 0,dp
4715 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
4716 0x32cc <main+212>: ldil 0x3000,r31
4717 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
4718 0x32d4 <main+220>: ldo 0(r31),rp
4719 0x32d8 <main+224>: addil -0x800,dp
4720 0x32dc <main+228>: ldo 0x588(r1),r26
4721 0x32e0 <main+232>: ldil 0x3000,r31
4722 End of assembler dump.
4725 Some architectures have more than one commonly-used set of instruction
4726 mnemonics or other syntax.
4729 @kindex set disassembly-flavor
4730 @cindex Intel disassembly flavor
4731 @cindex AT&T disassembly flavor
4732 @item set disassembly-flavor @var{instruction-set}
4733 Select the instruction set to use when disassembling the
4734 program via the @code{disassemble} or @code{x/i} commands.
4736 Currently this command is only defined for the Intel x86 family. You
4737 can set @var{instruction-set} to either @code{intel} or @code{att}.
4738 The default is @code{att}, the AT&T flavor used by default by Unix
4739 assemblers for x86-based targets.
4744 @chapter Examining Data
4746 @cindex printing data
4747 @cindex examining data
4750 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
4751 @c document because it is nonstandard... Under Epoch it displays in a
4752 @c different window or something like that.
4753 The usual way to examine data in your program is with the @code{print}
4754 command (abbreviated @code{p}), or its synonym @code{inspect}. It
4755 evaluates and prints the value of an expression of the language your
4756 program is written in (@pxref{Languages, ,Using @value{GDBN} with
4757 Different Languages}).
4760 @item print @var{expr}
4761 @itemx print /@var{f} @var{expr}
4762 @var{expr} is an expression (in the source language). By default the
4763 value of @var{expr} is printed in a format appropriate to its data type;
4764 you can choose a different format by specifying @samp{/@var{f}}, where
4765 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
4769 @itemx print /@var{f}
4770 @cindex reprint the last value
4771 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
4772 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
4773 conveniently inspect the same value in an alternative format.
4776 A more low-level way of examining data is with the @code{x} command.
4777 It examines data in memory at a specified address and prints it in a
4778 specified format. @xref{Memory, ,Examining memory}.
4780 If you are interested in information about types, or about how the
4781 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
4782 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
4786 * Expressions:: Expressions
4787 * Variables:: Program variables
4788 * Arrays:: Artificial arrays
4789 * Output Formats:: Output formats
4790 * Memory:: Examining memory
4791 * Auto Display:: Automatic display
4792 * Print Settings:: Print settings
4793 * Value History:: Value history
4794 * Convenience Vars:: Convenience variables
4795 * Registers:: Registers
4796 * Floating Point Hardware:: Floating point hardware
4797 * Vector Unit:: Vector Unit
4798 * Auxiliary Vector:: Auxiliary data provided by operating system
4799 * Memory Region Attributes:: Memory region attributes
4800 * Dump/Restore Files:: Copy between memory and a file
4801 * Core File Generation:: Cause a program dump its core
4802 * Character Sets:: Debugging programs that use a different
4803 character set than GDB does
4807 @section Expressions
4810 @code{print} and many other @value{GDBN} commands accept an expression and
4811 compute its value. Any kind of constant, variable or operator defined
4812 by the programming language you are using is valid in an expression in
4813 @value{GDBN}. This includes conditional expressions, function calls,
4814 casts, and string constants. It also includes preprocessor macros, if
4815 you compiled your program to include this information; see
4818 @cindex arrays in expressions
4819 @value{GDBN} supports array constants in expressions input by
4820 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
4821 you can use the command @code{print @{1, 2, 3@}} to build up an array in
4822 memory that is @code{malloc}ed in the target program.
4824 Because C is so widespread, most of the expressions shown in examples in
4825 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
4826 Languages}, for information on how to use expressions in other
4829 In this section, we discuss operators that you can use in @value{GDBN}
4830 expressions regardless of your programming language.
4832 @cindex casts, in expressions
4833 Casts are supported in all languages, not just in C, because it is so
4834 useful to cast a number into a pointer in order to examine a structure
4835 at that address in memory.
4836 @c FIXME: casts supported---Mod2 true?
4838 @value{GDBN} supports these operators, in addition to those common
4839 to programming languages:
4843 @samp{@@} is a binary operator for treating parts of memory as arrays.
4844 @xref{Arrays, ,Artificial arrays}, for more information.
4847 @samp{::} allows you to specify a variable in terms of the file or
4848 function where it is defined. @xref{Variables, ,Program variables}.
4850 @cindex @{@var{type}@}
4851 @cindex type casting memory
4852 @cindex memory, viewing as typed object
4853 @cindex casts, to view memory
4854 @item @{@var{type}@} @var{addr}
4855 Refers to an object of type @var{type} stored at address @var{addr} in
4856 memory. @var{addr} may be any expression whose value is an integer or
4857 pointer (but parentheses are required around binary operators, just as in
4858 a cast). This construct is allowed regardless of what kind of data is
4859 normally supposed to reside at @var{addr}.
4863 @section Program variables
4865 The most common kind of expression to use is the name of a variable
4868 Variables in expressions are understood in the selected stack frame
4869 (@pxref{Selection, ,Selecting a frame}); they must be either:
4873 global (or file-static)
4880 visible according to the scope rules of the
4881 programming language from the point of execution in that frame
4884 @noindent This means that in the function
4899 you can examine and use the variable @code{a} whenever your program is
4900 executing within the function @code{foo}, but you can only use or
4901 examine the variable @code{b} while your program is executing inside
4902 the block where @code{b} is declared.
4904 @cindex variable name conflict
4905 There is an exception: you can refer to a variable or function whose
4906 scope is a single source file even if the current execution point is not
4907 in this file. But it is possible to have more than one such variable or
4908 function with the same name (in different source files). If that
4909 happens, referring to that name has unpredictable effects. If you wish,
4910 you can specify a static variable in a particular function or file,
4911 using the colon-colon (@code{::}) notation:
4913 @cindex colon-colon, context for variables/functions
4915 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
4916 @cindex @code{::}, context for variables/functions
4919 @var{file}::@var{variable}
4920 @var{function}::@var{variable}
4924 Here @var{file} or @var{function} is the name of the context for the
4925 static @var{variable}. In the case of file names, you can use quotes to
4926 make sure @value{GDBN} parses the file name as a single word---for example,
4927 to print a global value of @code{x} defined in @file{f2.c}:
4930 (@value{GDBP}) p 'f2.c'::x
4933 @cindex C@t{++} scope resolution
4934 This use of @samp{::} is very rarely in conflict with the very similar
4935 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
4936 scope resolution operator in @value{GDBN} expressions.
4937 @c FIXME: Um, so what happens in one of those rare cases where it's in
4940 @cindex wrong values
4941 @cindex variable values, wrong
4942 @cindex function entry/exit, wrong values of variables
4943 @cindex optimized code, wrong values of variables
4945 @emph{Warning:} Occasionally, a local variable may appear to have the
4946 wrong value at certain points in a function---just after entry to a new
4947 scope, and just before exit.
4949 You may see this problem when you are stepping by machine instructions.
4950 This is because, on most machines, it takes more than one instruction to
4951 set up a stack frame (including local variable definitions); if you are
4952 stepping by machine instructions, variables may appear to have the wrong
4953 values until the stack frame is completely built. On exit, it usually
4954 also takes more than one machine instruction to destroy a stack frame;
4955 after you begin stepping through that group of instructions, local
4956 variable definitions may be gone.
4958 This may also happen when the compiler does significant optimizations.
4959 To be sure of always seeing accurate values, turn off all optimization
4962 @cindex ``No symbol "foo" in current context''
4963 Another possible effect of compiler optimizations is to optimize
4964 unused variables out of existence, or assign variables to registers (as
4965 opposed to memory addresses). Depending on the support for such cases
4966 offered by the debug info format used by the compiler, @value{GDBN}
4967 might not be able to display values for such local variables. If that
4968 happens, @value{GDBN} will print a message like this:
4971 No symbol "foo" in current context.
4974 To solve such problems, either recompile without optimizations, or use a
4975 different debug info format, if the compiler supports several such
4976 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
4977 usually supports the @option{-gstabs+} option. @option{-gstabs+}
4978 produces debug info in a format that is superior to formats such as
4979 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
4980 an effective form for debug info. @xref{Debugging Options,,Options
4981 for Debugging Your Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}.
4982 @xref{C, , Debugging C++}, for more info about debug info formats
4983 that are best suited to C@t{++} programs.
4986 @section Artificial arrays
4988 @cindex artificial array
4990 @kindex @@@r{, referencing memory as an array}
4991 It is often useful to print out several successive objects of the
4992 same type in memory; a section of an array, or an array of
4993 dynamically determined size for which only a pointer exists in the
4996 You can do this by referring to a contiguous span of memory as an
4997 @dfn{artificial array}, using the binary operator @samp{@@}. The left
4998 operand of @samp{@@} should be the first element of the desired array
4999 and be an individual object. The right operand should be the desired length
5000 of the array. The result is an array value whose elements are all of
5001 the type of the left argument. The first element is actually the left
5002 argument; the second element comes from bytes of memory immediately
5003 following those that hold the first element, and so on. Here is an
5004 example. If a program says
5007 int *array = (int *) malloc (len * sizeof (int));
5011 you can print the contents of @code{array} with
5017 The left operand of @samp{@@} must reside in memory. Array values made
5018 with @samp{@@} in this way behave just like other arrays in terms of
5019 subscripting, and are coerced to pointers when used in expressions.
5020 Artificial arrays most often appear in expressions via the value history
5021 (@pxref{Value History, ,Value history}), after printing one out.
5023 Another way to create an artificial array is to use a cast.
5024 This re-interprets a value as if it were an array.
5025 The value need not be in memory:
5027 (@value{GDBP}) p/x (short[2])0x12345678
5028 $1 = @{0x1234, 0x5678@}
5031 As a convenience, if you leave the array length out (as in
5032 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5033 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5035 (@value{GDBP}) p/x (short[])0x12345678
5036 $2 = @{0x1234, 0x5678@}
5039 Sometimes the artificial array mechanism is not quite enough; in
5040 moderately complex data structures, the elements of interest may not
5041 actually be adjacent---for example, if you are interested in the values
5042 of pointers in an array. One useful work-around in this situation is
5043 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5044 variables}) as a counter in an expression that prints the first
5045 interesting value, and then repeat that expression via @key{RET}. For
5046 instance, suppose you have an array @code{dtab} of pointers to
5047 structures, and you are interested in the values of a field @code{fv}
5048 in each structure. Here is an example of what you might type:
5058 @node Output Formats
5059 @section Output formats
5061 @cindex formatted output
5062 @cindex output formats
5063 By default, @value{GDBN} prints a value according to its data type. Sometimes
5064 this is not what you want. For example, you might want to print a number
5065 in hex, or a pointer in decimal. Or you might want to view data in memory
5066 at a certain address as a character string or as an instruction. To do
5067 these things, specify an @dfn{output format} when you print a value.
5069 The simplest use of output formats is to say how to print a value
5070 already computed. This is done by starting the arguments of the
5071 @code{print} command with a slash and a format letter. The format
5072 letters supported are:
5076 Regard the bits of the value as an integer, and print the integer in
5080 Print as integer in signed decimal.
5083 Print as integer in unsigned decimal.
5086 Print as integer in octal.
5089 Print as integer in binary. The letter @samp{t} stands for ``two''.
5090 @footnote{@samp{b} cannot be used because these format letters are also
5091 used with the @code{x} command, where @samp{b} stands for ``byte'';
5092 see @ref{Memory,,Examining memory}.}
5095 @cindex unknown address, locating
5096 @cindex locate address
5097 Print as an address, both absolute in hexadecimal and as an offset from
5098 the nearest preceding symbol. You can use this format used to discover
5099 where (in what function) an unknown address is located:
5102 (@value{GDBP}) p/a 0x54320
5103 $3 = 0x54320 <_initialize_vx+396>
5107 The command @code{info symbol 0x54320} yields similar results.
5108 @xref{Symbols, info symbol}.
5111 Regard as an integer and print it as a character constant.
5114 Regard the bits of the value as a floating point number and print
5115 using typical floating point syntax.
5118 For example, to print the program counter in hex (@pxref{Registers}), type
5125 Note that no space is required before the slash; this is because command
5126 names in @value{GDBN} cannot contain a slash.
5128 To reprint the last value in the value history with a different format,
5129 you can use the @code{print} command with just a format and no
5130 expression. For example, @samp{p/x} reprints the last value in hex.
5133 @section Examining memory
5135 You can use the command @code{x} (for ``examine'') to examine memory in
5136 any of several formats, independently of your program's data types.
5138 @cindex examining memory
5140 @kindex x @r{(examine memory)}
5141 @item x/@var{nfu} @var{addr}
5144 Use the @code{x} command to examine memory.
5147 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5148 much memory to display and how to format it; @var{addr} is an
5149 expression giving the address where you want to start displaying memory.
5150 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5151 Several commands set convenient defaults for @var{addr}.
5154 @item @var{n}, the repeat count
5155 The repeat count is a decimal integer; the default is 1. It specifies
5156 how much memory (counting by units @var{u}) to display.
5157 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5160 @item @var{f}, the display format
5161 The display format is one of the formats used by @code{print},
5162 @samp{s} (null-terminated string), or @samp{i} (machine instruction).
5163 The default is @samp{x} (hexadecimal) initially.
5164 The default changes each time you use either @code{x} or @code{print}.
5166 @item @var{u}, the unit size
5167 The unit size is any of
5173 Halfwords (two bytes).
5175 Words (four bytes). This is the initial default.
5177 Giant words (eight bytes).
5180 Each time you specify a unit size with @code{x}, that size becomes the
5181 default unit the next time you use @code{x}. (For the @samp{s} and
5182 @samp{i} formats, the unit size is ignored and is normally not written.)
5184 @item @var{addr}, starting display address
5185 @var{addr} is the address where you want @value{GDBN} to begin displaying
5186 memory. The expression need not have a pointer value (though it may);
5187 it is always interpreted as an integer address of a byte of memory.
5188 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5189 @var{addr} is usually just after the last address examined---but several
5190 other commands also set the default address: @code{info breakpoints} (to
5191 the address of the last breakpoint listed), @code{info line} (to the
5192 starting address of a line), and @code{print} (if you use it to display
5193 a value from memory).
5196 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5197 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5198 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5199 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5200 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5202 Since the letters indicating unit sizes are all distinct from the
5203 letters specifying output formats, you do not have to remember whether
5204 unit size or format comes first; either order works. The output
5205 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5206 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5208 Even though the unit size @var{u} is ignored for the formats @samp{s}
5209 and @samp{i}, you might still want to use a count @var{n}; for example,
5210 @samp{3i} specifies that you want to see three machine instructions,
5211 including any operands. The command @code{disassemble} gives an
5212 alternative way of inspecting machine instructions; see @ref{Machine
5213 Code,,Source and machine code}.
5215 All the defaults for the arguments to @code{x} are designed to make it
5216 easy to continue scanning memory with minimal specifications each time
5217 you use @code{x}. For example, after you have inspected three machine
5218 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5219 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5220 the repeat count @var{n} is used again; the other arguments default as
5221 for successive uses of @code{x}.
5223 @cindex @code{$_}, @code{$__}, and value history
5224 The addresses and contents printed by the @code{x} command are not saved
5225 in the value history because there is often too much of them and they
5226 would get in the way. Instead, @value{GDBN} makes these values available for
5227 subsequent use in expressions as values of the convenience variables
5228 @code{$_} and @code{$__}. After an @code{x} command, the last address
5229 examined is available for use in expressions in the convenience variable
5230 @code{$_}. The contents of that address, as examined, are available in
5231 the convenience variable @code{$__}.
5233 If the @code{x} command has a repeat count, the address and contents saved
5234 are from the last memory unit printed; this is not the same as the last
5235 address printed if several units were printed on the last line of output.
5238 @section Automatic display
5239 @cindex automatic display
5240 @cindex display of expressions
5242 If you find that you want to print the value of an expression frequently
5243 (to see how it changes), you might want to add it to the @dfn{automatic
5244 display list} so that @value{GDBN} prints its value each time your program stops.
5245 Each expression added to the list is given a number to identify it;
5246 to remove an expression from the list, you specify that number.
5247 The automatic display looks like this:
5251 3: bar[5] = (struct hack *) 0x3804
5255 This display shows item numbers, expressions and their current values. As with
5256 displays you request manually using @code{x} or @code{print}, you can
5257 specify the output format you prefer; in fact, @code{display} decides
5258 whether to use @code{print} or @code{x} depending on how elaborate your
5259 format specification is---it uses @code{x} if you specify a unit size,
5260 or one of the two formats (@samp{i} and @samp{s}) that are only
5261 supported by @code{x}; otherwise it uses @code{print}.
5265 @item display @var{expr}
5266 Add the expression @var{expr} to the list of expressions to display
5267 each time your program stops. @xref{Expressions, ,Expressions}.
5269 @code{display} does not repeat if you press @key{RET} again after using it.
5271 @item display/@var{fmt} @var{expr}
5272 For @var{fmt} specifying only a display format and not a size or
5273 count, add the expression @var{expr} to the auto-display list but
5274 arrange to display it each time in the specified format @var{fmt}.
5275 @xref{Output Formats,,Output formats}.
5277 @item display/@var{fmt} @var{addr}
5278 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5279 number of units, add the expression @var{addr} as a memory address to
5280 be examined each time your program stops. Examining means in effect
5281 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5284 For example, @samp{display/i $pc} can be helpful, to see the machine
5285 instruction about to be executed each time execution stops (@samp{$pc}
5286 is a common name for the program counter; @pxref{Registers, ,Registers}).
5289 @kindex delete display
5291 @item undisplay @var{dnums}@dots{}
5292 @itemx delete display @var{dnums}@dots{}
5293 Remove item numbers @var{dnums} from the list of expressions to display.
5295 @code{undisplay} does not repeat if you press @key{RET} after using it.
5296 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5298 @kindex disable display
5299 @item disable display @var{dnums}@dots{}
5300 Disable the display of item numbers @var{dnums}. A disabled display
5301 item is not printed automatically, but is not forgotten. It may be
5302 enabled again later.
5304 @kindex enable display
5305 @item enable display @var{dnums}@dots{}
5306 Enable display of item numbers @var{dnums}. It becomes effective once
5307 again in auto display of its expression, until you specify otherwise.
5310 Display the current values of the expressions on the list, just as is
5311 done when your program stops.
5313 @kindex info display
5315 Print the list of expressions previously set up to display
5316 automatically, each one with its item number, but without showing the
5317 values. This includes disabled expressions, which are marked as such.
5318 It also includes expressions which would not be displayed right now
5319 because they refer to automatic variables not currently available.
5322 @cindex display disabled out of scope
5323 If a display expression refers to local variables, then it does not make
5324 sense outside the lexical context for which it was set up. Such an
5325 expression is disabled when execution enters a context where one of its
5326 variables is not defined. For example, if you give the command
5327 @code{display last_char} while inside a function with an argument
5328 @code{last_char}, @value{GDBN} displays this argument while your program
5329 continues to stop inside that function. When it stops elsewhere---where
5330 there is no variable @code{last_char}---the display is disabled
5331 automatically. The next time your program stops where @code{last_char}
5332 is meaningful, you can enable the display expression once again.
5334 @node Print Settings
5335 @section Print settings
5337 @cindex format options
5338 @cindex print settings
5339 @value{GDBN} provides the following ways to control how arrays, structures,
5340 and symbols are printed.
5343 These settings are useful for debugging programs in any language:
5347 @item set print address
5348 @itemx set print address on
5349 @cindex print/don't print memory addresses
5350 @value{GDBN} prints memory addresses showing the location of stack
5351 traces, structure values, pointer values, breakpoints, and so forth,
5352 even when it also displays the contents of those addresses. The default
5353 is @code{on}. For example, this is what a stack frame display looks like with
5354 @code{set print address on}:
5359 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
5361 530 if (lquote != def_lquote)
5365 @item set print address off
5366 Do not print addresses when displaying their contents. For example,
5367 this is the same stack frame displayed with @code{set print address off}:
5371 (@value{GDBP}) set print addr off
5373 #0 set_quotes (lq="<<", rq=">>") at input.c:530
5374 530 if (lquote != def_lquote)
5378 You can use @samp{set print address off} to eliminate all machine
5379 dependent displays from the @value{GDBN} interface. For example, with
5380 @code{print address off}, you should get the same text for backtraces on
5381 all machines---whether or not they involve pointer arguments.
5384 @item show print address
5385 Show whether or not addresses are to be printed.
5388 When @value{GDBN} prints a symbolic address, it normally prints the
5389 closest earlier symbol plus an offset. If that symbol does not uniquely
5390 identify the address (for example, it is a name whose scope is a single
5391 source file), you may need to clarify. One way to do this is with
5392 @code{info line}, for example @samp{info line *0x4537}. Alternately,
5393 you can set @value{GDBN} to print the source file and line number when
5394 it prints a symbolic address:
5397 @item set print symbol-filename on
5398 @cindex closest symbol and offset for an address
5399 Tell @value{GDBN} to print the source file name and line number of a
5400 symbol in the symbolic form of an address.
5402 @item set print symbol-filename off
5403 Do not print source file name and line number of a symbol. This is the
5406 @item show print symbol-filename
5407 Show whether or not @value{GDBN} will print the source file name and
5408 line number of a symbol in the symbolic form of an address.
5411 Another situation where it is helpful to show symbol filenames and line
5412 numbers is when disassembling code; @value{GDBN} shows you the line
5413 number and source file that corresponds to each instruction.
5415 Also, you may wish to see the symbolic form only if the address being
5416 printed is reasonably close to the closest earlier symbol:
5419 @item set print max-symbolic-offset @var{max-offset}
5420 @cindex maximum value for offset of closest symbol
5421 Tell @value{GDBN} to only display the symbolic form of an address if the
5422 offset between the closest earlier symbol and the address is less than
5423 @var{max-offset}. The default is 0, which tells @value{GDBN}
5424 to always print the symbolic form of an address if any symbol precedes it.
5426 @item show print max-symbolic-offset
5427 Ask how large the maximum offset is that @value{GDBN} prints in a
5431 @cindex wild pointer, interpreting
5432 @cindex pointer, finding referent
5433 If you have a pointer and you are not sure where it points, try
5434 @samp{set print symbol-filename on}. Then you can determine the name
5435 and source file location of the variable where it points, using
5436 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
5437 For example, here @value{GDBN} shows that a variable @code{ptt} points
5438 at another variable @code{t}, defined in @file{hi2.c}:
5441 (@value{GDBP}) set print symbol-filename on
5442 (@value{GDBP}) p/a ptt
5443 $4 = 0xe008 <t in hi2.c>
5447 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
5448 does not show the symbol name and filename of the referent, even with
5449 the appropriate @code{set print} options turned on.
5452 Other settings control how different kinds of objects are printed:
5455 @item set print array
5456 @itemx set print array on
5457 @cindex pretty print arrays
5458 Pretty print arrays. This format is more convenient to read,
5459 but uses more space. The default is off.
5461 @item set print array off
5462 Return to compressed format for arrays.
5464 @item show print array
5465 Show whether compressed or pretty format is selected for displaying
5468 @item set print elements @var{number-of-elements}
5469 @cindex number of array elements to print
5470 Set a limit on how many elements of an array @value{GDBN} will print.
5471 If @value{GDBN} is printing a large array, it stops printing after it has
5472 printed the number of elements set by the @code{set print elements} command.
5473 This limit also applies to the display of strings.
5474 When @value{GDBN} starts, this limit is set to 200.
5475 Setting @var{number-of-elements} to zero means that the printing is unlimited.
5477 @item show print elements
5478 Display the number of elements of a large array that @value{GDBN} will print.
5479 If the number is 0, then the printing is unlimited.
5481 @item set print null-stop
5482 @cindex @sc{null} elements in arrays
5483 Cause @value{GDBN} to stop printing the characters of an array when the first
5484 @sc{null} is encountered. This is useful when large arrays actually
5485 contain only short strings.
5488 @item set print pretty on
5489 Cause @value{GDBN} to print structures in an indented format with one member
5490 per line, like this:
5505 @item set print pretty off
5506 Cause @value{GDBN} to print structures in a compact format, like this:
5510 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
5511 meat = 0x54 "Pork"@}
5516 This is the default format.
5518 @item show print pretty
5519 Show which format @value{GDBN} is using to print structures.
5521 @item set print sevenbit-strings on
5522 @cindex eight-bit characters in strings
5523 @cindex octal escapes in strings
5524 Print using only seven-bit characters; if this option is set,
5525 @value{GDBN} displays any eight-bit characters (in strings or
5526 character values) using the notation @code{\}@var{nnn}. This setting is
5527 best if you are working in English (@sc{ascii}) and you use the
5528 high-order bit of characters as a marker or ``meta'' bit.
5530 @item set print sevenbit-strings off
5531 Print full eight-bit characters. This allows the use of more
5532 international character sets, and is the default.
5534 @item show print sevenbit-strings
5535 Show whether or not @value{GDBN} is printing only seven-bit characters.
5537 @item set print union on
5538 @cindex unions in structures, printing
5539 Tell @value{GDBN} to print unions which are contained in structures. This
5540 is the default setting.
5542 @item set print union off
5543 Tell @value{GDBN} not to print unions which are contained in structures.
5545 @item show print union
5546 Ask @value{GDBN} whether or not it will print unions which are contained in
5549 For example, given the declarations
5552 typedef enum @{Tree, Bug@} Species;
5553 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
5554 typedef enum @{Caterpillar, Cocoon, Butterfly@}
5565 struct thing foo = @{Tree, @{Acorn@}@};
5569 with @code{set print union on} in effect @samp{p foo} would print
5572 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
5576 and with @code{set print union off} in effect it would print
5579 $1 = @{it = Tree, form = @{...@}@}
5585 These settings are of interest when debugging C@t{++} programs:
5588 @cindex demangling C@t{++} names
5589 @item set print demangle
5590 @itemx set print demangle on
5591 Print C@t{++} names in their source form rather than in the encoded
5592 (``mangled'') form passed to the assembler and linker for type-safe
5593 linkage. The default is on.
5595 @item show print demangle
5596 Show whether C@t{++} names are printed in mangled or demangled form.
5598 @item set print asm-demangle
5599 @itemx set print asm-demangle on
5600 Print C@t{++} names in their source form rather than their mangled form, even
5601 in assembler code printouts such as instruction disassemblies.
5604 @item show print asm-demangle
5605 Show whether C@t{++} names in assembly listings are printed in mangled
5608 @cindex C@t{++} symbol decoding style
5609 @cindex symbol decoding style, C@t{++}
5610 @item set demangle-style @var{style}
5611 Choose among several encoding schemes used by different compilers to
5612 represent C@t{++} names. The choices for @var{style} are currently:
5616 Allow @value{GDBN} to choose a decoding style by inspecting your program.
5619 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
5620 This is the default.
5623 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
5626 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
5629 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
5630 @strong{Warning:} this setting alone is not sufficient to allow
5631 debugging @code{cfront}-generated executables. @value{GDBN} would
5632 require further enhancement to permit that.
5635 If you omit @var{style}, you will see a list of possible formats.
5637 @item show demangle-style
5638 Display the encoding style currently in use for decoding C@t{++} symbols.
5640 @item set print object
5641 @itemx set print object on
5642 @cindex derived type of an object, printing
5643 When displaying a pointer to an object, identify the @emph{actual}
5644 (derived) type of the object rather than the @emph{declared} type, using
5645 the virtual function table.
5647 @item set print object off
5648 Display only the declared type of objects, without reference to the
5649 virtual function table. This is the default setting.
5651 @item show print object
5652 Show whether actual, or declared, object types are displayed.
5654 @item set print static-members
5655 @itemx set print static-members on
5656 @cindex static members of C@t{++} objects
5657 Print static members when displaying a C@t{++} object. The default is on.
5659 @item set print static-members off
5660 Do not print static members when displaying a C@t{++} object.
5662 @item show print static-members
5663 Show whether C@t{++} static members are printed, or not.
5665 @c These don't work with HP ANSI C++ yet.
5666 @item set print vtbl
5667 @itemx set print vtbl on
5668 @cindex pretty print C@t{++} virtual function tables
5669 Pretty print C@t{++} virtual function tables. The default is off.
5670 (The @code{vtbl} commands do not work on programs compiled with the HP
5671 ANSI C@t{++} compiler (@code{aCC}).)
5673 @item set print vtbl off
5674 Do not pretty print C@t{++} virtual function tables.
5676 @item show print vtbl
5677 Show whether C@t{++} virtual function tables are pretty printed, or not.
5681 @section Value history
5683 @cindex value history
5684 Values printed by the @code{print} command are saved in the @value{GDBN}
5685 @dfn{value history}. This allows you to refer to them in other expressions.
5686 Values are kept until the symbol table is re-read or discarded
5687 (for example with the @code{file} or @code{symbol-file} commands).
5688 When the symbol table changes, the value history is discarded,
5689 since the values may contain pointers back to the types defined in the
5694 @cindex history number
5695 The values printed are given @dfn{history numbers} by which you can
5696 refer to them. These are successive integers starting with one.
5697 @code{print} shows you the history number assigned to a value by
5698 printing @samp{$@var{num} = } before the value; here @var{num} is the
5701 To refer to any previous value, use @samp{$} followed by the value's
5702 history number. The way @code{print} labels its output is designed to
5703 remind you of this. Just @code{$} refers to the most recent value in
5704 the history, and @code{$$} refers to the value before that.
5705 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
5706 is the value just prior to @code{$$}, @code{$$1} is equivalent to
5707 @code{$$}, and @code{$$0} is equivalent to @code{$}.
5709 For example, suppose you have just printed a pointer to a structure and
5710 want to see the contents of the structure. It suffices to type
5716 If you have a chain of structures where the component @code{next} points
5717 to the next one, you can print the contents of the next one with this:
5724 You can print successive links in the chain by repeating this
5725 command---which you can do by just typing @key{RET}.
5727 Note that the history records values, not expressions. If the value of
5728 @code{x} is 4 and you type these commands:
5736 then the value recorded in the value history by the @code{print} command
5737 remains 4 even though the value of @code{x} has changed.
5742 Print the last ten values in the value history, with their item numbers.
5743 This is like @samp{p@ $$9} repeated ten times, except that @code{show
5744 values} does not change the history.
5746 @item show values @var{n}
5747 Print ten history values centered on history item number @var{n}.
5750 Print ten history values just after the values last printed. If no more
5751 values are available, @code{show values +} produces no display.
5754 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
5755 same effect as @samp{show values +}.
5757 @node Convenience Vars
5758 @section Convenience variables
5760 @cindex convenience variables
5761 @value{GDBN} provides @dfn{convenience variables} that you can use within
5762 @value{GDBN} to hold on to a value and refer to it later. These variables
5763 exist entirely within @value{GDBN}; they are not part of your program, and
5764 setting a convenience variable has no direct effect on further execution
5765 of your program. That is why you can use them freely.
5767 Convenience variables are prefixed with @samp{$}. Any name preceded by
5768 @samp{$} can be used for a convenience variable, unless it is one of
5769 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
5770 (Value history references, in contrast, are @emph{numbers} preceded
5771 by @samp{$}. @xref{Value History, ,Value history}.)
5773 You can save a value in a convenience variable with an assignment
5774 expression, just as you would set a variable in your program.
5778 set $foo = *object_ptr
5782 would save in @code{$foo} the value contained in the object pointed to by
5785 Using a convenience variable for the first time creates it, but its
5786 value is @code{void} until you assign a new value. You can alter the
5787 value with another assignment at any time.
5789 Convenience variables have no fixed types. You can assign a convenience
5790 variable any type of value, including structures and arrays, even if
5791 that variable already has a value of a different type. The convenience
5792 variable, when used as an expression, has the type of its current value.
5795 @kindex show convenience
5796 @item show convenience
5797 Print a list of convenience variables used so far, and their values.
5798 Abbreviated @code{show conv}.
5801 One of the ways to use a convenience variable is as a counter to be
5802 incremented or a pointer to be advanced. For example, to print
5803 a field from successive elements of an array of structures:
5807 print bar[$i++]->contents
5811 Repeat that command by typing @key{RET}.
5813 Some convenience variables are created automatically by @value{GDBN} and given
5814 values likely to be useful.
5817 @vindex $_@r{, convenience variable}
5819 The variable @code{$_} is automatically set by the @code{x} command to
5820 the last address examined (@pxref{Memory, ,Examining memory}). Other
5821 commands which provide a default address for @code{x} to examine also
5822 set @code{$_} to that address; these commands include @code{info line}
5823 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
5824 except when set by the @code{x} command, in which case it is a pointer
5825 to the type of @code{$__}.
5827 @vindex $__@r{, convenience variable}
5829 The variable @code{$__} is automatically set by the @code{x} command
5830 to the value found in the last address examined. Its type is chosen
5831 to match the format in which the data was printed.
5834 @vindex $_exitcode@r{, convenience variable}
5835 The variable @code{$_exitcode} is automatically set to the exit code when
5836 the program being debugged terminates.
5839 On HP-UX systems, if you refer to a function or variable name that
5840 begins with a dollar sign, @value{GDBN} searches for a user or system
5841 name first, before it searches for a convenience variable.
5847 You can refer to machine register contents, in expressions, as variables
5848 with names starting with @samp{$}. The names of registers are different
5849 for each machine; use @code{info registers} to see the names used on
5853 @kindex info registers
5854 @item info registers
5855 Print the names and values of all registers except floating-point
5856 and vector registers (in the selected stack frame).
5858 @kindex info all-registers
5859 @cindex floating point registers
5860 @item info all-registers
5861 Print the names and values of all registers, including floating-point
5862 and vector registers (in the selected stack frame).
5864 @item info registers @var{regname} @dots{}
5865 Print the @dfn{relativized} value of each specified register @var{regname}.
5866 As discussed in detail below, register values are normally relative to
5867 the selected stack frame. @var{regname} may be any register name valid on
5868 the machine you are using, with or without the initial @samp{$}.
5871 @value{GDBN} has four ``standard'' register names that are available (in
5872 expressions) on most machines---whenever they do not conflict with an
5873 architecture's canonical mnemonics for registers. The register names
5874 @code{$pc} and @code{$sp} are used for the program counter register and
5875 the stack pointer. @code{$fp} is used for a register that contains a
5876 pointer to the current stack frame, and @code{$ps} is used for a
5877 register that contains the processor status. For example,
5878 you could print the program counter in hex with
5885 or print the instruction to be executed next with
5892 or add four to the stack pointer@footnote{This is a way of removing
5893 one word from the stack, on machines where stacks grow downward in
5894 memory (most machines, nowadays). This assumes that the innermost
5895 stack frame is selected; setting @code{$sp} is not allowed when other
5896 stack frames are selected. To pop entire frames off the stack,
5897 regardless of machine architecture, use @code{return};
5898 see @ref{Returning, ,Returning from a function}.} with
5904 Whenever possible, these four standard register names are available on
5905 your machine even though the machine has different canonical mnemonics,
5906 so long as there is no conflict. The @code{info registers} command
5907 shows the canonical names. For example, on the SPARC, @code{info
5908 registers} displays the processor status register as @code{$psr} but you
5909 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
5910 is an alias for the @sc{eflags} register.
5912 @value{GDBN} always considers the contents of an ordinary register as an
5913 integer when the register is examined in this way. Some machines have
5914 special registers which can hold nothing but floating point; these
5915 registers are considered to have floating point values. There is no way
5916 to refer to the contents of an ordinary register as floating point value
5917 (although you can @emph{print} it as a floating point value with
5918 @samp{print/f $@var{regname}}).
5920 Some registers have distinct ``raw'' and ``virtual'' data formats. This
5921 means that the data format in which the register contents are saved by
5922 the operating system is not the same one that your program normally
5923 sees. For example, the registers of the 68881 floating point
5924 coprocessor are always saved in ``extended'' (raw) format, but all C
5925 programs expect to work with ``double'' (virtual) format. In such
5926 cases, @value{GDBN} normally works with the virtual format only (the format
5927 that makes sense for your program), but the @code{info registers} command
5928 prints the data in both formats.
5930 Normally, register values are relative to the selected stack frame
5931 (@pxref{Selection, ,Selecting a frame}). This means that you get the
5932 value that the register would contain if all stack frames farther in
5933 were exited and their saved registers restored. In order to see the
5934 true contents of hardware registers, you must select the innermost
5935 frame (with @samp{frame 0}).
5937 However, @value{GDBN} must deduce where registers are saved, from the machine
5938 code generated by your compiler. If some registers are not saved, or if
5939 @value{GDBN} is unable to locate the saved registers, the selected stack
5940 frame makes no difference.
5942 @node Floating Point Hardware
5943 @section Floating point hardware
5944 @cindex floating point
5946 Depending on the configuration, @value{GDBN} may be able to give
5947 you more information about the status of the floating point hardware.
5952 Display hardware-dependent information about the floating
5953 point unit. The exact contents and layout vary depending on the
5954 floating point chip. Currently, @samp{info float} is supported on
5955 the ARM and x86 machines.
5959 @section Vector Unit
5962 Depending on the configuration, @value{GDBN} may be able to give you
5963 more information about the status of the vector unit.
5968 Display information about the vector unit. The exact contents and
5969 layout vary depending on the hardware.
5972 @node Auxiliary Vector
5973 @section Operating system auxiliary vector
5974 @cindex auxiliary vector
5975 @cindex vector, auxiliary
5977 Some operating systems supply an @dfn{auxiliary vector} to programs at
5978 startup. This is akin to the arguments and environment that you
5979 specify for a program, but contains a system-dependent variety of
5980 binary values that tell system libraries important details about the
5981 hardware, operating system, and process. Each value's purpose is
5982 identified by an integer tag; the meanings are well-known but system-specific.
5983 Depending on the configuration and operating system facilities,
5984 @value{GDBN} may be able to show you this information.
5989 Display the auxiliary vector of the inferior, which can be either a
5990 live process or a core dump file. @value{GDBN} prints each tag value
5991 numerically, and also shows names and text descriptions for recognized
5992 tags. Some values in the vector are numbers, some bit masks, and some
5993 pointers to strings or other data. @value{GDBN} displays each value in the
5994 most appropriate form for a recognized tag, and in hexadecimal for
5995 an unrecognized tag.
5998 @node Memory Region Attributes
5999 @section Memory region attributes
6000 @cindex memory region attributes
6002 @dfn{Memory region attributes} allow you to describe special handling
6003 required by regions of your target's memory. @value{GDBN} uses attributes
6004 to determine whether to allow certain types of memory accesses; whether to
6005 use specific width accesses; and whether to cache target memory.
6007 Defined memory regions can be individually enabled and disabled. When a
6008 memory region is disabled, @value{GDBN} uses the default attributes when
6009 accessing memory in that region. Similarly, if no memory regions have
6010 been defined, @value{GDBN} uses the default attributes when accessing
6013 When a memory region is defined, it is given a number to identify it;
6014 to enable, disable, or remove a memory region, you specify that number.
6018 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
6019 Define memory region bounded by @var{lower} and @var{upper} with
6020 attributes @var{attributes}@dots{}. Note that @var{upper} == 0 is a
6021 special case: it is treated as the the target's maximum memory address.
6022 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
6025 @item delete mem @var{nums}@dots{}
6026 Remove memory regions @var{nums}@dots{}.
6029 @item disable mem @var{nums}@dots{}
6030 Disable memory regions @var{nums}@dots{}.
6031 A disabled memory region is not forgotten.
6032 It may be enabled again later.
6035 @item enable mem @var{nums}@dots{}
6036 Enable memory regions @var{nums}@dots{}.
6040 Print a table of all defined memory regions, with the following columns
6044 @item Memory Region Number
6045 @item Enabled or Disabled.
6046 Enabled memory regions are marked with @samp{y}.
6047 Disabled memory regions are marked with @samp{n}.
6050 The address defining the inclusive lower bound of the memory region.
6053 The address defining the exclusive upper bound of the memory region.
6056 The list of attributes set for this memory region.
6061 @subsection Attributes
6063 @subsubsection Memory Access Mode
6064 The access mode attributes set whether @value{GDBN} may make read or
6065 write accesses to a memory region.
6067 While these attributes prevent @value{GDBN} from performing invalid
6068 memory accesses, they do nothing to prevent the target system, I/O DMA,
6069 etc. from accessing memory.
6073 Memory is read only.
6075 Memory is write only.
6077 Memory is read/write. This is the default.
6080 @subsubsection Memory Access Size
6081 The acccess size attributes tells @value{GDBN} to use specific sized
6082 accesses in the memory region. Often memory mapped device registers
6083 require specific sized accesses. If no access size attribute is
6084 specified, @value{GDBN} may use accesses of any size.
6088 Use 8 bit memory accesses.
6090 Use 16 bit memory accesses.
6092 Use 32 bit memory accesses.
6094 Use 64 bit memory accesses.
6097 @c @subsubsection Hardware/Software Breakpoints
6098 @c The hardware/software breakpoint attributes set whether @value{GDBN}
6099 @c will use hardware or software breakpoints for the internal breakpoints
6100 @c used by the step, next, finish, until, etc. commands.
6104 @c Always use hardware breakpoints
6105 @c @item swbreak (default)
6108 @subsubsection Data Cache
6109 The data cache attributes set whether @value{GDBN} will cache target
6110 memory. While this generally improves performance by reducing debug
6111 protocol overhead, it can lead to incorrect results because @value{GDBN}
6112 does not know about volatile variables or memory mapped device
6117 Enable @value{GDBN} to cache target memory.
6119 Disable @value{GDBN} from caching target memory. This is the default.
6122 @c @subsubsection Memory Write Verification
6123 @c The memory write verification attributes set whether @value{GDBN}
6124 @c will re-reads data after each write to verify the write was successful.
6128 @c @item noverify (default)
6131 @node Dump/Restore Files
6132 @section Copy between memory and a file
6133 @cindex dump/restore files
6134 @cindex append data to a file
6135 @cindex dump data to a file
6136 @cindex restore data from a file
6138 You can use the commands @code{dump}, @code{append}, and
6139 @code{restore} to copy data between target memory and a file. The
6140 @code{dump} and @code{append} commands write data to a file, and the
6141 @code{restore} command reads data from a file back into the inferior's
6142 memory. Files may be in binary, Motorola S-record, Intel hex, or
6143 Tektronix Hex format; however, @value{GDBN} can only append to binary
6149 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6150 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
6151 Dump the contents of memory from @var{start_addr} to @var{end_addr},
6152 or the value of @var{expr}, to @var{filename} in the given format.
6154 The @var{format} parameter may be any one of:
6161 Motorola S-record format.
6163 Tektronix Hex format.
6166 @value{GDBN} uses the same definitions of these formats as the
6167 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
6168 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
6172 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6173 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
6174 Append the contents of memory from @var{start_addr} to @var{end_addr},
6175 or the value of @var{expr}, to @var{filename}, in raw binary form.
6176 (@value{GDBN} can only append data to files in raw binary form.)
6179 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
6180 Restore the contents of file @var{filename} into memory. The
6181 @code{restore} command can automatically recognize any known @sc{bfd}
6182 file format, except for raw binary. To restore a raw binary file you
6183 must specify the optional keyword @code{binary} after the filename.
6185 If @var{bias} is non-zero, its value will be added to the addresses
6186 contained in the file. Binary files always start at address zero, so
6187 they will be restored at address @var{bias}. Other bfd files have
6188 a built-in location; they will be restored at offset @var{bias}
6191 If @var{start} and/or @var{end} are non-zero, then only data between
6192 file offset @var{start} and file offset @var{end} will be restored.
6193 These offsets are relative to the addresses in the file, before
6194 the @var{bias} argument is applied.
6198 @node Core File Generation
6199 @section How to Produce a Core File from Your Program
6200 @cindex dump core from inferior
6202 A @dfn{core file} or @dfn{core dump} is a file that records the memory
6203 image of a running process and its process status (register values
6204 etc.). Its primary use is post-mortem debugging of a program that
6205 crashed while it ran outside a debugger. A program that crashes
6206 automatically produces a core file, unless this feature is disabled by
6207 the user. @xref{Files}, for information on invoking @value{GDBN} in
6208 the post-mortem debugging mode.
6210 Occasionally, you may wish to produce a core file of the program you
6211 are debugging in order to preserve a snapshot of its state.
6212 @value{GDBN} has a special command for that.
6216 @kindex generate-core-file
6217 @item generate-core-file [@var{file}]
6218 @itemx gcore [@var{file}]
6219 Produce a core dump of the inferior process. The optional argument
6220 @var{file} specifies the file name where to put the core dump. If not
6221 specified, the file name defaults to @file{core.@var{pid}}, where
6222 @var{pid} is the inferior process ID.
6224 Note that this command is implemented only for some systems (as of
6225 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
6228 @node Character Sets
6229 @section Character Sets
6230 @cindex character sets
6232 @cindex translating between character sets
6233 @cindex host character set
6234 @cindex target character set
6236 If the program you are debugging uses a different character set to
6237 represent characters and strings than the one @value{GDBN} uses itself,
6238 @value{GDBN} can automatically translate between the character sets for
6239 you. The character set @value{GDBN} uses we call the @dfn{host
6240 character set}; the one the inferior program uses we call the
6241 @dfn{target character set}.
6243 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
6244 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
6245 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
6246 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
6247 then the host character set is Latin-1, and the target character set is
6248 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
6249 target-charset EBCDIC-US}, then @value{GDBN} translates between
6250 @sc{ebcdic} and Latin 1 as you print character or string values, or use
6251 character and string literals in expressions.
6253 @value{GDBN} has no way to automatically recognize which character set
6254 the inferior program uses; you must tell it, using the @code{set
6255 target-charset} command, described below.
6257 Here are the commands for controlling @value{GDBN}'s character set
6261 @item set target-charset @var{charset}
6262 @kindex set target-charset
6263 Set the current target character set to @var{charset}. We list the
6264 character set names @value{GDBN} recognizes below, but if you type
6265 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6266 list the target character sets it supports.
6270 @item set host-charset @var{charset}
6271 @kindex set host-charset
6272 Set the current host character set to @var{charset}.
6274 By default, @value{GDBN} uses a host character set appropriate to the
6275 system it is running on; you can override that default using the
6276 @code{set host-charset} command.
6278 @value{GDBN} can only use certain character sets as its host character
6279 set. We list the character set names @value{GDBN} recognizes below, and
6280 indicate which can be host character sets, but if you type
6281 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6282 list the host character sets it supports.
6284 @item set charset @var{charset}
6286 Set the current host and target character sets to @var{charset}. As
6287 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
6288 @value{GDBN} will list the name of the character sets that can be used
6289 for both host and target.
6293 @kindex show charset
6294 Show the names of the current host and target charsets.
6296 @itemx show host-charset
6297 @kindex show host-charset
6298 Show the name of the current host charset.
6300 @itemx show target-charset
6301 @kindex show target-charset
6302 Show the name of the current target charset.
6306 @value{GDBN} currently includes support for the following character
6312 @cindex ASCII character set
6313 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
6317 @cindex ISO 8859-1 character set
6318 @cindex ISO Latin 1 character set
6319 The ISO Latin 1 character set. This extends @sc{ascii} with accented
6320 characters needed for French, German, and Spanish. @value{GDBN} can use
6321 this as its host character set.
6325 @cindex EBCDIC character set
6326 @cindex IBM1047 character set
6327 Variants of the @sc{ebcdic} character set, used on some of IBM's
6328 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
6329 @value{GDBN} cannot use these as its host character set.
6333 Note that these are all single-byte character sets. More work inside
6334 GDB is needed to support multi-byte or variable-width character
6335 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
6337 Here is an example of @value{GDBN}'s character set support in action.
6338 Assume that the following source code has been placed in the file
6339 @file{charset-test.c}:
6345 = @{72, 101, 108, 108, 111, 44, 32, 119,
6346 111, 114, 108, 100, 33, 10, 0@};
6347 char ibm1047_hello[]
6348 = @{200, 133, 147, 147, 150, 107, 64, 166,
6349 150, 153, 147, 132, 90, 37, 0@};
6353 printf ("Hello, world!\n");
6357 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
6358 containing the string @samp{Hello, world!} followed by a newline,
6359 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
6361 We compile the program, and invoke the debugger on it:
6364 $ gcc -g charset-test.c -o charset-test
6365 $ gdb -nw charset-test
6366 GNU gdb 2001-12-19-cvs
6367 Copyright 2001 Free Software Foundation, Inc.
6372 We can use the @code{show charset} command to see what character sets
6373 @value{GDBN} is currently using to interpret and display characters and
6377 (@value{GDBP}) show charset
6378 The current host and target character set is `ISO-8859-1'.
6382 For the sake of printing this manual, let's use @sc{ascii} as our
6383 initial character set:
6385 (@value{GDBP}) set charset ASCII
6386 (@value{GDBP}) show charset
6387 The current host and target character set is `ASCII'.
6391 Let's assume that @sc{ascii} is indeed the correct character set for our
6392 host system --- in other words, let's assume that if @value{GDBN} prints
6393 characters using the @sc{ascii} character set, our terminal will display
6394 them properly. Since our current target character set is also
6395 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
6398 (@value{GDBP}) print ascii_hello
6399 $1 = 0x401698 "Hello, world!\n"
6400 (@value{GDBP}) print ascii_hello[0]
6405 @value{GDBN} uses the target character set for character and string
6406 literals you use in expressions:
6409 (@value{GDBP}) print '+'
6414 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
6417 @value{GDBN} relies on the user to tell it which character set the
6418 target program uses. If we print @code{ibm1047_hello} while our target
6419 character set is still @sc{ascii}, we get jibberish:
6422 (@value{GDBP}) print ibm1047_hello
6423 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
6424 (@value{GDBP}) print ibm1047_hello[0]
6429 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
6430 @value{GDBN} tells us the character sets it supports:
6433 (@value{GDBP}) set target-charset
6434 ASCII EBCDIC-US IBM1047 ISO-8859-1
6435 (@value{GDBP}) set target-charset
6438 We can select @sc{ibm1047} as our target character set, and examine the
6439 program's strings again. Now the @sc{ascii} string is wrong, but
6440 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
6441 target character set, @sc{ibm1047}, to the host character set,
6442 @sc{ascii}, and they display correctly:
6445 (@value{GDBP}) set target-charset IBM1047
6446 (@value{GDBP}) show charset
6447 The current host character set is `ASCII'.
6448 The current target character set is `IBM1047'.
6449 (@value{GDBP}) print ascii_hello
6450 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
6451 (@value{GDBP}) print ascii_hello[0]
6453 (@value{GDBP}) print ibm1047_hello
6454 $8 = 0x4016a8 "Hello, world!\n"
6455 (@value{GDBP}) print ibm1047_hello[0]
6460 As above, @value{GDBN} uses the target character set for character and
6461 string literals you use in expressions:
6464 (@value{GDBP}) print '+'
6469 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
6474 @chapter C Preprocessor Macros
6476 Some languages, such as C and C@t{++}, provide a way to define and invoke
6477 ``preprocessor macros'' which expand into strings of tokens.
6478 @value{GDBN} can evaluate expressions containing macro invocations, show
6479 the result of macro expansion, and show a macro's definition, including
6480 where it was defined.
6482 You may need to compile your program specially to provide @value{GDBN}
6483 with information about preprocessor macros. Most compilers do not
6484 include macros in their debugging information, even when you compile
6485 with the @option{-g} flag. @xref{Compilation}.
6487 A program may define a macro at one point, remove that definition later,
6488 and then provide a different definition after that. Thus, at different
6489 points in the program, a macro may have different definitions, or have
6490 no definition at all. If there is a current stack frame, @value{GDBN}
6491 uses the macros in scope at that frame's source code line. Otherwise,
6492 @value{GDBN} uses the macros in scope at the current listing location;
6495 At the moment, @value{GDBN} does not support the @code{##}
6496 token-splicing operator, the @code{#} stringification operator, or
6497 variable-arity macros.
6499 Whenever @value{GDBN} evaluates an expression, it always expands any
6500 macro invocations present in the expression. @value{GDBN} also provides
6501 the following commands for working with macros explicitly.
6505 @kindex macro expand
6506 @cindex macro expansion, showing the results of preprocessor
6507 @cindex preprocessor macro expansion, showing the results of
6508 @cindex expanding preprocessor macros
6509 @item macro expand @var{expression}
6510 @itemx macro exp @var{expression}
6511 Show the results of expanding all preprocessor macro invocations in
6512 @var{expression}. Since @value{GDBN} simply expands macros, but does
6513 not parse the result, @var{expression} need not be a valid expression;
6514 it can be any string of tokens.
6516 @item macro expand-once @var{expression}
6517 @itemx macro exp1 @var{expression}
6518 @cindex expand macro once
6519 @i{(This command is not yet implemented.)} Show the results of
6520 expanding those preprocessor macro invocations that appear explicitly in
6521 @var{expression}. Macro invocations appearing in that expansion are
6522 left unchanged. This command allows you to see the effect of a
6523 particular macro more clearly, without being confused by further
6524 expansions. Since @value{GDBN} simply expands macros, but does not
6525 parse the result, @var{expression} need not be a valid expression; it
6526 can be any string of tokens.
6529 @cindex macro definition, showing
6530 @cindex definition, showing a macro's
6531 @item info macro @var{macro}
6532 Show the definition of the macro named @var{macro}, and describe the
6533 source location where that definition was established.
6535 @kindex macro define
6536 @cindex user-defined macros
6537 @cindex defining macros interactively
6538 @cindex macros, user-defined
6539 @item macro define @var{macro} @var{replacement-list}
6540 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
6541 @i{(This command is not yet implemented.)} Introduce a definition for a
6542 preprocessor macro named @var{macro}, invocations of which are replaced
6543 by the tokens given in @var{replacement-list}. The first form of this
6544 command defines an ``object-like'' macro, which takes no arguments; the
6545 second form defines a ``function-like'' macro, which takes the arguments
6546 given in @var{arglist}.
6548 A definition introduced by this command is in scope in every expression
6549 evaluated in @value{GDBN}, until it is removed with the @command{macro
6550 undef} command, described below. The definition overrides all
6551 definitions for @var{macro} present in the program being debugged, as
6552 well as any previous user-supplied definition.
6555 @item macro undef @var{macro}
6556 @i{(This command is not yet implemented.)} Remove any user-supplied
6557 definition for the macro named @var{macro}. This command only affects
6558 definitions provided with the @command{macro define} command, described
6559 above; it cannot remove definitions present in the program being
6564 @cindex macros, example of debugging with
6565 Here is a transcript showing the above commands in action. First, we
6566 show our source files:
6574 #define ADD(x) (M + x)
6579 printf ("Hello, world!\n");
6581 printf ("We're so creative.\n");
6583 printf ("Goodbye, world!\n");
6590 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
6591 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
6592 compiler includes information about preprocessor macros in the debugging
6596 $ gcc -gdwarf-2 -g3 sample.c -o sample
6600 Now, we start @value{GDBN} on our sample program:
6604 GNU gdb 2002-05-06-cvs
6605 Copyright 2002 Free Software Foundation, Inc.
6606 GDB is free software, @dots{}
6610 We can expand macros and examine their definitions, even when the
6611 program is not running. @value{GDBN} uses the current listing position
6612 to decide which macro definitions are in scope:
6615 (@value{GDBP}) list main
6618 5 #define ADD(x) (M + x)
6623 10 printf ("Hello, world!\n");
6625 12 printf ("We're so creative.\n");
6626 (@value{GDBP}) info macro ADD
6627 Defined at /home/jimb/gdb/macros/play/sample.c:5
6628 #define ADD(x) (M + x)
6629 (@value{GDBP}) info macro Q
6630 Defined at /home/jimb/gdb/macros/play/sample.h:1
6631 included at /home/jimb/gdb/macros/play/sample.c:2
6633 (@value{GDBP}) macro expand ADD(1)
6634 expands to: (42 + 1)
6635 (@value{GDBP}) macro expand-once ADD(1)
6636 expands to: once (M + 1)
6640 In the example above, note that @command{macro expand-once} expands only
6641 the macro invocation explicit in the original text --- the invocation of
6642 @code{ADD} --- but does not expand the invocation of the macro @code{M},
6643 which was introduced by @code{ADD}.
6645 Once the program is running, GDB uses the macro definitions in force at
6646 the source line of the current stack frame:
6649 (@value{GDBP}) break main
6650 Breakpoint 1 at 0x8048370: file sample.c, line 10.
6652 Starting program: /home/jimb/gdb/macros/play/sample
6654 Breakpoint 1, main () at sample.c:10
6655 10 printf ("Hello, world!\n");
6659 At line 10, the definition of the macro @code{N} at line 9 is in force:
6662 (@value{GDBP}) info macro N
6663 Defined at /home/jimb/gdb/macros/play/sample.c:9
6665 (@value{GDBP}) macro expand N Q M
6667 (@value{GDBP}) print N Q M
6672 As we step over directives that remove @code{N}'s definition, and then
6673 give it a new definition, @value{GDBN} finds the definition (or lack
6674 thereof) in force at each point:
6679 12 printf ("We're so creative.\n");
6680 (@value{GDBP}) info macro N
6681 The symbol `N' has no definition as a C/C++ preprocessor macro
6682 at /home/jimb/gdb/macros/play/sample.c:12
6685 14 printf ("Goodbye, world!\n");
6686 (@value{GDBP}) info macro N
6687 Defined at /home/jimb/gdb/macros/play/sample.c:13
6689 (@value{GDBP}) macro expand N Q M
6690 expands to: 1729 < 42
6691 (@value{GDBP}) print N Q M
6698 @chapter Tracepoints
6699 @c This chapter is based on the documentation written by Michael
6700 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
6703 In some applications, it is not feasible for the debugger to interrupt
6704 the program's execution long enough for the developer to learn
6705 anything helpful about its behavior. If the program's correctness
6706 depends on its real-time behavior, delays introduced by a debugger
6707 might cause the program to change its behavior drastically, or perhaps
6708 fail, even when the code itself is correct. It is useful to be able
6709 to observe the program's behavior without interrupting it.
6711 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
6712 specify locations in the program, called @dfn{tracepoints}, and
6713 arbitrary expressions to evaluate when those tracepoints are reached.
6714 Later, using the @code{tfind} command, you can examine the values
6715 those expressions had when the program hit the tracepoints. The
6716 expressions may also denote objects in memory---structures or arrays,
6717 for example---whose values @value{GDBN} should record; while visiting
6718 a particular tracepoint, you may inspect those objects as if they were
6719 in memory at that moment. However, because @value{GDBN} records these
6720 values without interacting with you, it can do so quickly and
6721 unobtrusively, hopefully not disturbing the program's behavior.
6723 The tracepoint facility is currently available only for remote
6724 targets. @xref{Targets}. In addition, your remote target must know how
6725 to collect trace data. This functionality is implemented in the remote
6726 stub; however, none of the stubs distributed with @value{GDBN} support
6727 tracepoints as of this writing.
6729 This chapter describes the tracepoint commands and features.
6733 * Analyze Collected Data::
6734 * Tracepoint Variables::
6737 @node Set Tracepoints
6738 @section Commands to Set Tracepoints
6740 Before running such a @dfn{trace experiment}, an arbitrary number of
6741 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
6742 tracepoint has a number assigned to it by @value{GDBN}. Like with
6743 breakpoints, tracepoint numbers are successive integers starting from
6744 one. Many of the commands associated with tracepoints take the
6745 tracepoint number as their argument, to identify which tracepoint to
6748 For each tracepoint, you can specify, in advance, some arbitrary set
6749 of data that you want the target to collect in the trace buffer when
6750 it hits that tracepoint. The collected data can include registers,
6751 local variables, or global data. Later, you can use @value{GDBN}
6752 commands to examine the values these data had at the time the
6755 This section describes commands to set tracepoints and associated
6756 conditions and actions.
6759 * Create and Delete Tracepoints::
6760 * Enable and Disable Tracepoints::
6761 * Tracepoint Passcounts::
6762 * Tracepoint Actions::
6763 * Listing Tracepoints::
6764 * Starting and Stopping Trace Experiment::
6767 @node Create and Delete Tracepoints
6768 @subsection Create and Delete Tracepoints
6771 @cindex set tracepoint
6774 The @code{trace} command is very similar to the @code{break} command.
6775 Its argument can be a source line, a function name, or an address in
6776 the target program. @xref{Set Breaks}. The @code{trace} command
6777 defines a tracepoint, which is a point in the target program where the
6778 debugger will briefly stop, collect some data, and then allow the
6779 program to continue. Setting a tracepoint or changing its commands
6780 doesn't take effect until the next @code{tstart} command; thus, you
6781 cannot change the tracepoint attributes once a trace experiment is
6784 Here are some examples of using the @code{trace} command:
6787 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
6789 (@value{GDBP}) @b{trace +2} // 2 lines forward
6791 (@value{GDBP}) @b{trace my_function} // first source line of function
6793 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
6795 (@value{GDBP}) @b{trace *0x2117c4} // an address
6799 You can abbreviate @code{trace} as @code{tr}.
6802 @cindex last tracepoint number
6803 @cindex recent tracepoint number
6804 @cindex tracepoint number
6805 The convenience variable @code{$tpnum} records the tracepoint number
6806 of the most recently set tracepoint.
6808 @kindex delete tracepoint
6809 @cindex tracepoint deletion
6810 @item delete tracepoint @r{[}@var{num}@r{]}
6811 Permanently delete one or more tracepoints. With no argument, the
6812 default is to delete all tracepoints.
6817 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
6819 (@value{GDBP}) @b{delete trace} // remove all tracepoints
6823 You can abbreviate this command as @code{del tr}.
6826 @node Enable and Disable Tracepoints
6827 @subsection Enable and Disable Tracepoints
6830 @kindex disable tracepoint
6831 @item disable tracepoint @r{[}@var{num}@r{]}
6832 Disable tracepoint @var{num}, or all tracepoints if no argument
6833 @var{num} is given. A disabled tracepoint will have no effect during
6834 the next trace experiment, but it is not forgotten. You can re-enable
6835 a disabled tracepoint using the @code{enable tracepoint} command.
6837 @kindex enable tracepoint
6838 @item enable tracepoint @r{[}@var{num}@r{]}
6839 Enable tracepoint @var{num}, or all tracepoints. The enabled
6840 tracepoints will become effective the next time a trace experiment is
6844 @node Tracepoint Passcounts
6845 @subsection Tracepoint Passcounts
6849 @cindex tracepoint pass count
6850 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
6851 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
6852 automatically stop a trace experiment. If a tracepoint's passcount is
6853 @var{n}, then the trace experiment will be automatically stopped on
6854 the @var{n}'th time that tracepoint is hit. If the tracepoint number
6855 @var{num} is not specified, the @code{passcount} command sets the
6856 passcount of the most recently defined tracepoint. If no passcount is
6857 given, the trace experiment will run until stopped explicitly by the
6863 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
6864 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
6866 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
6867 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
6868 (@value{GDBP}) @b{trace foo}
6869 (@value{GDBP}) @b{pass 3}
6870 (@value{GDBP}) @b{trace bar}
6871 (@value{GDBP}) @b{pass 2}
6872 (@value{GDBP}) @b{trace baz}
6873 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
6874 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
6875 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
6876 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
6880 @node Tracepoint Actions
6881 @subsection Tracepoint Action Lists
6885 @cindex tracepoint actions
6886 @item actions @r{[}@var{num}@r{]}
6887 This command will prompt for a list of actions to be taken when the
6888 tracepoint is hit. If the tracepoint number @var{num} is not
6889 specified, this command sets the actions for the one that was most
6890 recently defined (so that you can define a tracepoint and then say
6891 @code{actions} without bothering about its number). You specify the
6892 actions themselves on the following lines, one action at a time, and
6893 terminate the actions list with a line containing just @code{end}. So
6894 far, the only defined actions are @code{collect} and
6895 @code{while-stepping}.
6897 @cindex remove actions from a tracepoint
6898 To remove all actions from a tracepoint, type @samp{actions @var{num}}
6899 and follow it immediately with @samp{end}.
6902 (@value{GDBP}) @b{collect @var{data}} // collect some data
6904 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
6906 (@value{GDBP}) @b{end} // signals the end of actions.
6909 In the following example, the action list begins with @code{collect}
6910 commands indicating the things to be collected when the tracepoint is
6911 hit. Then, in order to single-step and collect additional data
6912 following the tracepoint, a @code{while-stepping} command is used,
6913 followed by the list of things to be collected while stepping. The
6914 @code{while-stepping} command is terminated by its own separate
6915 @code{end} command. Lastly, the action list is terminated by an
6919 (@value{GDBP}) @b{trace foo}
6920 (@value{GDBP}) @b{actions}
6921 Enter actions for tracepoint 1, one per line:
6930 @kindex collect @r{(tracepoints)}
6931 @item collect @var{expr1}, @var{expr2}, @dots{}
6932 Collect values of the given expressions when the tracepoint is hit.
6933 This command accepts a comma-separated list of any valid expressions.
6934 In addition to global, static, or local variables, the following
6935 special arguments are supported:
6939 collect all registers
6942 collect all function arguments
6945 collect all local variables.
6948 You can give several consecutive @code{collect} commands, each one
6949 with a single argument, or one @code{collect} command with several
6950 arguments separated by commas: the effect is the same.
6952 The command @code{info scope} (@pxref{Symbols, info scope}) is
6953 particularly useful for figuring out what data to collect.
6955 @kindex while-stepping @r{(tracepoints)}
6956 @item while-stepping @var{n}
6957 Perform @var{n} single-step traces after the tracepoint, collecting
6958 new data at each step. The @code{while-stepping} command is
6959 followed by the list of what to collect while stepping (followed by
6960 its own @code{end} command):
6964 > collect $regs, myglobal
6970 You may abbreviate @code{while-stepping} as @code{ws} or
6974 @node Listing Tracepoints
6975 @subsection Listing Tracepoints
6978 @kindex info tracepoints
6979 @cindex information about tracepoints
6980 @item info tracepoints @r{[}@var{num}@r{]}
6981 Display information about the tracepoint @var{num}. If you don't specify
6982 a tracepoint number, displays information about all the tracepoints
6983 defined so far. For each tracepoint, the following information is
6990 whether it is enabled or disabled
6994 its passcount as given by the @code{passcount @var{n}} command
6996 its step count as given by the @code{while-stepping @var{n}} command
6998 where in the source files is the tracepoint set
7000 its action list as given by the @code{actions} command
7004 (@value{GDBP}) @b{info trace}
7005 Num Enb Address PassC StepC What
7006 1 y 0x002117c4 0 0 <gdb_asm>
7007 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
7008 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
7013 This command can be abbreviated @code{info tp}.
7016 @node Starting and Stopping Trace Experiment
7017 @subsection Starting and Stopping Trace Experiment
7021 @cindex start a new trace experiment
7022 @cindex collected data discarded
7024 This command takes no arguments. It starts the trace experiment, and
7025 begins collecting data. This has the side effect of discarding all
7026 the data collected in the trace buffer during the previous trace
7030 @cindex stop a running trace experiment
7032 This command takes no arguments. It ends the trace experiment, and
7033 stops collecting data.
7035 @strong{Note:} a trace experiment and data collection may stop
7036 automatically if any tracepoint's passcount is reached
7037 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
7040 @cindex status of trace data collection
7041 @cindex trace experiment, status of
7043 This command displays the status of the current trace data
7047 Here is an example of the commands we described so far:
7050 (@value{GDBP}) @b{trace gdb_c_test}
7051 (@value{GDBP}) @b{actions}
7052 Enter actions for tracepoint #1, one per line.
7053 > collect $regs,$locals,$args
7058 (@value{GDBP}) @b{tstart}
7059 [time passes @dots{}]
7060 (@value{GDBP}) @b{tstop}
7064 @node Analyze Collected Data
7065 @section Using the collected data
7067 After the tracepoint experiment ends, you use @value{GDBN} commands
7068 for examining the trace data. The basic idea is that each tracepoint
7069 collects a trace @dfn{snapshot} every time it is hit and another
7070 snapshot every time it single-steps. All these snapshots are
7071 consecutively numbered from zero and go into a buffer, and you can
7072 examine them later. The way you examine them is to @dfn{focus} on a
7073 specific trace snapshot. When the remote stub is focused on a trace
7074 snapshot, it will respond to all @value{GDBN} requests for memory and
7075 registers by reading from the buffer which belongs to that snapshot,
7076 rather than from @emph{real} memory or registers of the program being
7077 debugged. This means that @strong{all} @value{GDBN} commands
7078 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
7079 behave as if we were currently debugging the program state as it was
7080 when the tracepoint occurred. Any requests for data that are not in
7081 the buffer will fail.
7084 * tfind:: How to select a trace snapshot
7085 * tdump:: How to display all data for a snapshot
7086 * save-tracepoints:: How to save tracepoints for a future run
7090 @subsection @code{tfind @var{n}}
7093 @cindex select trace snapshot
7094 @cindex find trace snapshot
7095 The basic command for selecting a trace snapshot from the buffer is
7096 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
7097 counting from zero. If no argument @var{n} is given, the next
7098 snapshot is selected.
7100 Here are the various forms of using the @code{tfind} command.
7104 Find the first snapshot in the buffer. This is a synonym for
7105 @code{tfind 0} (since 0 is the number of the first snapshot).
7108 Stop debugging trace snapshots, resume @emph{live} debugging.
7111 Same as @samp{tfind none}.
7114 No argument means find the next trace snapshot.
7117 Find the previous trace snapshot before the current one. This permits
7118 retracing earlier steps.
7120 @item tfind tracepoint @var{num}
7121 Find the next snapshot associated with tracepoint @var{num}. Search
7122 proceeds forward from the last examined trace snapshot. If no
7123 argument @var{num} is given, it means find the next snapshot collected
7124 for the same tracepoint as the current snapshot.
7126 @item tfind pc @var{addr}
7127 Find the next snapshot associated with the value @var{addr} of the
7128 program counter. Search proceeds forward from the last examined trace
7129 snapshot. If no argument @var{addr} is given, it means find the next
7130 snapshot with the same value of PC as the current snapshot.
7132 @item tfind outside @var{addr1}, @var{addr2}
7133 Find the next snapshot whose PC is outside the given range of
7136 @item tfind range @var{addr1}, @var{addr2}
7137 Find the next snapshot whose PC is between @var{addr1} and
7138 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
7140 @item tfind line @r{[}@var{file}:@r{]}@var{n}
7141 Find the next snapshot associated with the source line @var{n}. If
7142 the optional argument @var{file} is given, refer to line @var{n} in
7143 that source file. Search proceeds forward from the last examined
7144 trace snapshot. If no argument @var{n} is given, it means find the
7145 next line other than the one currently being examined; thus saying
7146 @code{tfind line} repeatedly can appear to have the same effect as
7147 stepping from line to line in a @emph{live} debugging session.
7150 The default arguments for the @code{tfind} commands are specifically
7151 designed to make it easy to scan through the trace buffer. For
7152 instance, @code{tfind} with no argument selects the next trace
7153 snapshot, and @code{tfind -} with no argument selects the previous
7154 trace snapshot. So, by giving one @code{tfind} command, and then
7155 simply hitting @key{RET} repeatedly you can examine all the trace
7156 snapshots in order. Or, by saying @code{tfind -} and then hitting
7157 @key{RET} repeatedly you can examine the snapshots in reverse order.
7158 The @code{tfind line} command with no argument selects the snapshot
7159 for the next source line executed. The @code{tfind pc} command with
7160 no argument selects the next snapshot with the same program counter
7161 (PC) as the current frame. The @code{tfind tracepoint} command with
7162 no argument selects the next trace snapshot collected by the same
7163 tracepoint as the current one.
7165 In addition to letting you scan through the trace buffer manually,
7166 these commands make it easy to construct @value{GDBN} scripts that
7167 scan through the trace buffer and print out whatever collected data
7168 you are interested in. Thus, if we want to examine the PC, FP, and SP
7169 registers from each trace frame in the buffer, we can say this:
7172 (@value{GDBP}) @b{tfind start}
7173 (@value{GDBP}) @b{while ($trace_frame != -1)}
7174 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
7175 $trace_frame, $pc, $sp, $fp
7179 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
7180 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
7181 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
7182 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
7183 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
7184 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
7185 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
7186 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
7187 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
7188 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
7189 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
7192 Or, if we want to examine the variable @code{X} at each source line in
7196 (@value{GDBP}) @b{tfind start}
7197 (@value{GDBP}) @b{while ($trace_frame != -1)}
7198 > printf "Frame %d, X == %d\n", $trace_frame, X
7208 @subsection @code{tdump}
7210 @cindex dump all data collected at tracepoint
7211 @cindex tracepoint data, display
7213 This command takes no arguments. It prints all the data collected at
7214 the current trace snapshot.
7217 (@value{GDBP}) @b{trace 444}
7218 (@value{GDBP}) @b{actions}
7219 Enter actions for tracepoint #2, one per line:
7220 > collect $regs, $locals, $args, gdb_long_test
7223 (@value{GDBP}) @b{tstart}
7225 (@value{GDBP}) @b{tfind line 444}
7226 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
7228 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
7230 (@value{GDBP}) @b{tdump}
7231 Data collected at tracepoint 2, trace frame 1:
7232 d0 0xc4aa0085 -995491707
7236 d4 0x71aea3d 119204413
7241 a1 0x3000668 50333288
7244 a4 0x3000698 50333336
7246 fp 0x30bf3c 0x30bf3c
7247 sp 0x30bf34 0x30bf34
7249 pc 0x20b2c8 0x20b2c8
7253 p = 0x20e5b4 "gdb-test"
7260 gdb_long_test = 17 '\021'
7265 @node save-tracepoints
7266 @subsection @code{save-tracepoints @var{filename}}
7267 @kindex save-tracepoints
7268 @cindex save tracepoints for future sessions
7270 This command saves all current tracepoint definitions together with
7271 their actions and passcounts, into a file @file{@var{filename}}
7272 suitable for use in a later debugging session. To read the saved
7273 tracepoint definitions, use the @code{source} command (@pxref{Command
7276 @node Tracepoint Variables
7277 @section Convenience Variables for Tracepoints
7278 @cindex tracepoint variables
7279 @cindex convenience variables for tracepoints
7282 @vindex $trace_frame
7283 @item (int) $trace_frame
7284 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
7285 snapshot is selected.
7288 @item (int) $tracepoint
7289 The tracepoint for the current trace snapshot.
7292 @item (int) $trace_line
7293 The line number for the current trace snapshot.
7296 @item (char []) $trace_file
7297 The source file for the current trace snapshot.
7300 @item (char []) $trace_func
7301 The name of the function containing @code{$tracepoint}.
7304 Note: @code{$trace_file} is not suitable for use in @code{printf},
7305 use @code{output} instead.
7307 Here's a simple example of using these convenience variables for
7308 stepping through all the trace snapshots and printing some of their
7312 (@value{GDBP}) @b{tfind start}
7314 (@value{GDBP}) @b{while $trace_frame != -1}
7315 > output $trace_file
7316 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
7322 @chapter Debugging Programs That Use Overlays
7325 If your program is too large to fit completely in your target system's
7326 memory, you can sometimes use @dfn{overlays} to work around this
7327 problem. @value{GDBN} provides some support for debugging programs that
7331 * How Overlays Work:: A general explanation of overlays.
7332 * Overlay Commands:: Managing overlays in @value{GDBN}.
7333 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
7334 mapped by asking the inferior.
7335 * Overlay Sample Program:: A sample program using overlays.
7338 @node How Overlays Work
7339 @section How Overlays Work
7340 @cindex mapped overlays
7341 @cindex unmapped overlays
7342 @cindex load address, overlay's
7343 @cindex mapped address
7344 @cindex overlay area
7346 Suppose you have a computer whose instruction address space is only 64
7347 kilobytes long, but which has much more memory which can be accessed by
7348 other means: special instructions, segment registers, or memory
7349 management hardware, for example. Suppose further that you want to
7350 adapt a program which is larger than 64 kilobytes to run on this system.
7352 One solution is to identify modules of your program which are relatively
7353 independent, and need not call each other directly; call these modules
7354 @dfn{overlays}. Separate the overlays from the main program, and place
7355 their machine code in the larger memory. Place your main program in
7356 instruction memory, but leave at least enough space there to hold the
7357 largest overlay as well.
7359 Now, to call a function located in an overlay, you must first copy that
7360 overlay's machine code from the large memory into the space set aside
7361 for it in the instruction memory, and then jump to its entry point
7364 @c NB: In the below the mapped area's size is greater or equal to the
7365 @c size of all overlays. This is intentional to remind the developer
7366 @c that overlays don't necessarily need to be the same size.
7370 Data Instruction Larger
7371 Address Space Address Space Address Space
7372 +-----------+ +-----------+ +-----------+
7374 +-----------+ +-----------+ +-----------+<-- overlay 1
7375 | program | | main | .----| overlay 1 | load address
7376 | variables | | program | | +-----------+
7377 | and heap | | | | | |
7378 +-----------+ | | | +-----------+<-- overlay 2
7379 | | +-----------+ | | | load address
7380 +-----------+ | | | .-| overlay 2 |
7382 mapped --->+-----------+ | | +-----------+
7384 | overlay | <-' | | |
7385 | area | <---' +-----------+<-- overlay 3
7386 | | <---. | | load address
7387 +-----------+ `--| overlay 3 |
7394 @anchor{A code overlay}A code overlay
7398 The diagram (@pxref{A code overlay}) shows a system with separate data
7399 and instruction address spaces. To map an overlay, the program copies
7400 its code from the larger address space to the instruction address space.
7401 Since the overlays shown here all use the same mapped address, only one
7402 may be mapped at a time. For a system with a single address space for
7403 data and instructions, the diagram would be similar, except that the
7404 program variables and heap would share an address space with the main
7405 program and the overlay area.
7407 An overlay loaded into instruction memory and ready for use is called a
7408 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
7409 instruction memory. An overlay not present (or only partially present)
7410 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
7411 is its address in the larger memory. The mapped address is also called
7412 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
7413 called the @dfn{load memory address}, or @dfn{LMA}.
7415 Unfortunately, overlays are not a completely transparent way to adapt a
7416 program to limited instruction memory. They introduce a new set of
7417 global constraints you must keep in mind as you design your program:
7422 Before calling or returning to a function in an overlay, your program
7423 must make sure that overlay is actually mapped. Otherwise, the call or
7424 return will transfer control to the right address, but in the wrong
7425 overlay, and your program will probably crash.
7428 If the process of mapping an overlay is expensive on your system, you
7429 will need to choose your overlays carefully to minimize their effect on
7430 your program's performance.
7433 The executable file you load onto your system must contain each
7434 overlay's instructions, appearing at the overlay's load address, not its
7435 mapped address. However, each overlay's instructions must be relocated
7436 and its symbols defined as if the overlay were at its mapped address.
7437 You can use GNU linker scripts to specify different load and relocation
7438 addresses for pieces of your program; see @ref{Overlay Description,,,
7439 ld.info, Using ld: the GNU linker}.
7442 The procedure for loading executable files onto your system must be able
7443 to load their contents into the larger address space as well as the
7444 instruction and data spaces.
7448 The overlay system described above is rather simple, and could be
7449 improved in many ways:
7454 If your system has suitable bank switch registers or memory management
7455 hardware, you could use those facilities to make an overlay's load area
7456 contents simply appear at their mapped address in instruction space.
7457 This would probably be faster than copying the overlay to its mapped
7458 area in the usual way.
7461 If your overlays are small enough, you could set aside more than one
7462 overlay area, and have more than one overlay mapped at a time.
7465 You can use overlays to manage data, as well as instructions. In
7466 general, data overlays are even less transparent to your design than
7467 code overlays: whereas code overlays only require care when you call or
7468 return to functions, data overlays require care every time you access
7469 the data. Also, if you change the contents of a data overlay, you
7470 must copy its contents back out to its load address before you can copy a
7471 different data overlay into the same mapped area.
7476 @node Overlay Commands
7477 @section Overlay Commands
7479 To use @value{GDBN}'s overlay support, each overlay in your program must
7480 correspond to a separate section of the executable file. The section's
7481 virtual memory address and load memory address must be the overlay's
7482 mapped and load addresses. Identifying overlays with sections allows
7483 @value{GDBN} to determine the appropriate address of a function or
7484 variable, depending on whether the overlay is mapped or not.
7486 @value{GDBN}'s overlay commands all start with the word @code{overlay};
7487 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
7492 Disable @value{GDBN}'s overlay support. When overlay support is
7493 disabled, @value{GDBN} assumes that all functions and variables are
7494 always present at their mapped addresses. By default, @value{GDBN}'s
7495 overlay support is disabled.
7497 @item overlay manual
7498 @cindex manual overlay debugging
7499 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
7500 relies on you to tell it which overlays are mapped, and which are not,
7501 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
7502 commands described below.
7504 @item overlay map-overlay @var{overlay}
7505 @itemx overlay map @var{overlay}
7506 @cindex map an overlay
7507 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
7508 be the name of the object file section containing the overlay. When an
7509 overlay is mapped, @value{GDBN} assumes it can find the overlay's
7510 functions and variables at their mapped addresses. @value{GDBN} assumes
7511 that any other overlays whose mapped ranges overlap that of
7512 @var{overlay} are now unmapped.
7514 @item overlay unmap-overlay @var{overlay}
7515 @itemx overlay unmap @var{overlay}
7516 @cindex unmap an overlay
7517 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
7518 must be the name of the object file section containing the overlay.
7519 When an overlay is unmapped, @value{GDBN} assumes it can find the
7520 overlay's functions and variables at their load addresses.
7523 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
7524 consults a data structure the overlay manager maintains in the inferior
7525 to see which overlays are mapped. For details, see @ref{Automatic
7528 @item overlay load-target
7530 @cindex reloading the overlay table
7531 Re-read the overlay table from the inferior. Normally, @value{GDBN}
7532 re-reads the table @value{GDBN} automatically each time the inferior
7533 stops, so this command should only be necessary if you have changed the
7534 overlay mapping yourself using @value{GDBN}. This command is only
7535 useful when using automatic overlay debugging.
7537 @item overlay list-overlays
7539 @cindex listing mapped overlays
7540 Display a list of the overlays currently mapped, along with their mapped
7541 addresses, load addresses, and sizes.
7545 Normally, when @value{GDBN} prints a code address, it includes the name
7546 of the function the address falls in:
7549 (@value{GDBP}) print main
7550 $3 = @{int ()@} 0x11a0 <main>
7553 When overlay debugging is enabled, @value{GDBN} recognizes code in
7554 unmapped overlays, and prints the names of unmapped functions with
7555 asterisks around them. For example, if @code{foo} is a function in an
7556 unmapped overlay, @value{GDBN} prints it this way:
7559 (@value{GDBP}) overlay list
7560 No sections are mapped.
7561 (@value{GDBP}) print foo
7562 $5 = @{int (int)@} 0x100000 <*foo*>
7565 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
7569 (@value{GDBP}) overlay list
7570 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
7571 mapped at 0x1016 - 0x104a
7572 (@value{GDBP}) print foo
7573 $6 = @{int (int)@} 0x1016 <foo>
7576 When overlay debugging is enabled, @value{GDBN} can find the correct
7577 address for functions and variables in an overlay, whether or not the
7578 overlay is mapped. This allows most @value{GDBN} commands, like
7579 @code{break} and @code{disassemble}, to work normally, even on unmapped
7580 code. However, @value{GDBN}'s breakpoint support has some limitations:
7584 @cindex breakpoints in overlays
7585 @cindex overlays, setting breakpoints in
7586 You can set breakpoints in functions in unmapped overlays, as long as
7587 @value{GDBN} can write to the overlay at its load address.
7589 @value{GDBN} can not set hardware or simulator-based breakpoints in
7590 unmapped overlays. However, if you set a breakpoint at the end of your
7591 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
7592 you are using manual overlay management), @value{GDBN} will re-set its
7593 breakpoints properly.
7597 @node Automatic Overlay Debugging
7598 @section Automatic Overlay Debugging
7599 @cindex automatic overlay debugging
7601 @value{GDBN} can automatically track which overlays are mapped and which
7602 are not, given some simple co-operation from the overlay manager in the
7603 inferior. If you enable automatic overlay debugging with the
7604 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
7605 looks in the inferior's memory for certain variables describing the
7606 current state of the overlays.
7608 Here are the variables your overlay manager must define to support
7609 @value{GDBN}'s automatic overlay debugging:
7613 @item @code{_ovly_table}:
7614 This variable must be an array of the following structures:
7619 /* The overlay's mapped address. */
7622 /* The size of the overlay, in bytes. */
7625 /* The overlay's load address. */
7628 /* Non-zero if the overlay is currently mapped;
7630 unsigned long mapped;
7634 @item @code{_novlys}:
7635 This variable must be a four-byte signed integer, holding the total
7636 number of elements in @code{_ovly_table}.
7640 To decide whether a particular overlay is mapped or not, @value{GDBN}
7641 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
7642 @code{lma} members equal the VMA and LMA of the overlay's section in the
7643 executable file. When @value{GDBN} finds a matching entry, it consults
7644 the entry's @code{mapped} member to determine whether the overlay is
7647 In addition, your overlay manager may define a function called
7648 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
7649 will silently set a breakpoint there. If the overlay manager then
7650 calls this function whenever it has changed the overlay table, this
7651 will enable @value{GDBN} to accurately keep track of which overlays
7652 are in program memory, and update any breakpoints that may be set
7653 in overlays. This will allow breakpoints to work even if the
7654 overlays are kept in ROM or other non-writable memory while they
7655 are not being executed.
7657 @node Overlay Sample Program
7658 @section Overlay Sample Program
7659 @cindex overlay example program
7661 When linking a program which uses overlays, you must place the overlays
7662 at their load addresses, while relocating them to run at their mapped
7663 addresses. To do this, you must write a linker script (@pxref{Overlay
7664 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
7665 since linker scripts are specific to a particular host system, target
7666 architecture, and target memory layout, this manual cannot provide
7667 portable sample code demonstrating @value{GDBN}'s overlay support.
7669 However, the @value{GDBN} source distribution does contain an overlaid
7670 program, with linker scripts for a few systems, as part of its test
7671 suite. The program consists of the following files from
7672 @file{gdb/testsuite/gdb.base}:
7676 The main program file.
7678 A simple overlay manager, used by @file{overlays.c}.
7683 Overlay modules, loaded and used by @file{overlays.c}.
7686 Linker scripts for linking the test program on the @code{d10v-elf}
7687 and @code{m32r-elf} targets.
7690 You can build the test program using the @code{d10v-elf} GCC
7691 cross-compiler like this:
7694 $ d10v-elf-gcc -g -c overlays.c
7695 $ d10v-elf-gcc -g -c ovlymgr.c
7696 $ d10v-elf-gcc -g -c foo.c
7697 $ d10v-elf-gcc -g -c bar.c
7698 $ d10v-elf-gcc -g -c baz.c
7699 $ d10v-elf-gcc -g -c grbx.c
7700 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
7701 baz.o grbx.o -Wl,-Td10v.ld -o overlays
7704 The build process is identical for any other architecture, except that
7705 you must substitute the appropriate compiler and linker script for the
7706 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
7710 @chapter Using @value{GDBN} with Different Languages
7713 Although programming languages generally have common aspects, they are
7714 rarely expressed in the same manner. For instance, in ANSI C,
7715 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
7716 Modula-2, it is accomplished by @code{p^}. Values can also be
7717 represented (and displayed) differently. Hex numbers in C appear as
7718 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
7720 @cindex working language
7721 Language-specific information is built into @value{GDBN} for some languages,
7722 allowing you to express operations like the above in your program's
7723 native language, and allowing @value{GDBN} to output values in a manner
7724 consistent with the syntax of your program's native language. The
7725 language you use to build expressions is called the @dfn{working
7729 * Setting:: Switching between source languages
7730 * Show:: Displaying the language
7731 * Checks:: Type and range checks
7732 * Support:: Supported languages
7733 * Unsupported languages:: Unsupported languages
7737 @section Switching between source languages
7739 There are two ways to control the working language---either have @value{GDBN}
7740 set it automatically, or select it manually yourself. You can use the
7741 @code{set language} command for either purpose. On startup, @value{GDBN}
7742 defaults to setting the language automatically. The working language is
7743 used to determine how expressions you type are interpreted, how values
7746 In addition to the working language, every source file that
7747 @value{GDBN} knows about has its own working language. For some object
7748 file formats, the compiler might indicate which language a particular
7749 source file is in. However, most of the time @value{GDBN} infers the
7750 language from the name of the file. The language of a source file
7751 controls whether C@t{++} names are demangled---this way @code{backtrace} can
7752 show each frame appropriately for its own language. There is no way to
7753 set the language of a source file from within @value{GDBN}, but you can
7754 set the language associated with a filename extension. @xref{Show, ,
7755 Displaying the language}.
7757 This is most commonly a problem when you use a program, such
7758 as @code{cfront} or @code{f2c}, that generates C but is written in
7759 another language. In that case, make the
7760 program use @code{#line} directives in its C output; that way
7761 @value{GDBN} will know the correct language of the source code of the original
7762 program, and will display that source code, not the generated C code.
7765 * Filenames:: Filename extensions and languages.
7766 * Manually:: Setting the working language manually
7767 * Automatically:: Having @value{GDBN} infer the source language
7771 @subsection List of filename extensions and languages
7773 If a source file name ends in one of the following extensions, then
7774 @value{GDBN} infers that its language is the one indicated.
7795 Objective-C source file
7802 Modula-2 source file
7806 Assembler source file. This actually behaves almost like C, but
7807 @value{GDBN} does not skip over function prologues when stepping.
7810 In addition, you may set the language associated with a filename
7811 extension. @xref{Show, , Displaying the language}.
7814 @subsection Setting the working language
7816 If you allow @value{GDBN} to set the language automatically,
7817 expressions are interpreted the same way in your debugging session and
7820 @kindex set language
7821 If you wish, you may set the language manually. To do this, issue the
7822 command @samp{set language @var{lang}}, where @var{lang} is the name of
7824 @code{c} or @code{modula-2}.
7825 For a list of the supported languages, type @samp{set language}.
7827 Setting the language manually prevents @value{GDBN} from updating the working
7828 language automatically. This can lead to confusion if you try
7829 to debug a program when the working language is not the same as the
7830 source language, when an expression is acceptable to both
7831 languages---but means different things. For instance, if the current
7832 source file were written in C, and @value{GDBN} was parsing Modula-2, a
7840 might not have the effect you intended. In C, this means to add
7841 @code{b} and @code{c} and place the result in @code{a}. The result
7842 printed would be the value of @code{a}. In Modula-2, this means to compare
7843 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
7846 @subsection Having @value{GDBN} infer the source language
7848 To have @value{GDBN} set the working language automatically, use
7849 @samp{set language local} or @samp{set language auto}. @value{GDBN}
7850 then infers the working language. That is, when your program stops in a
7851 frame (usually by encountering a breakpoint), @value{GDBN} sets the
7852 working language to the language recorded for the function in that
7853 frame. If the language for a frame is unknown (that is, if the function
7854 or block corresponding to the frame was defined in a source file that
7855 does not have a recognized extension), the current working language is
7856 not changed, and @value{GDBN} issues a warning.
7858 This may not seem necessary for most programs, which are written
7859 entirely in one source language. However, program modules and libraries
7860 written in one source language can be used by a main program written in
7861 a different source language. Using @samp{set language auto} in this
7862 case frees you from having to set the working language manually.
7865 @section Displaying the language
7867 The following commands help you find out which language is the
7868 working language, and also what language source files were written in.
7870 @kindex show language
7873 Display the current working language. This is the
7874 language you can use with commands such as @code{print} to
7875 build and compute expressions that may involve variables in your program.
7878 @kindex info frame@r{, show the source language}
7879 Display the source language for this frame. This language becomes the
7880 working language if you use an identifier from this frame.
7881 @xref{Frame Info, ,Information about a frame}, to identify the other
7882 information listed here.
7885 @kindex info source@r{, show the source language}
7886 Display the source language of this source file.
7887 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
7888 information listed here.
7891 In unusual circumstances, you may have source files with extensions
7892 not in the standard list. You can then set the extension associated
7893 with a language explicitly:
7895 @kindex set extension-language
7896 @kindex info extensions
7898 @item set extension-language @var{.ext} @var{language}
7899 Set source files with extension @var{.ext} to be assumed to be in
7900 the source language @var{language}.
7902 @item info extensions
7903 List all the filename extensions and the associated languages.
7907 @section Type and range checking
7910 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
7911 checking are included, but they do not yet have any effect. This
7912 section documents the intended facilities.
7914 @c FIXME remove warning when type/range code added
7916 Some languages are designed to guard you against making seemingly common
7917 errors through a series of compile- and run-time checks. These include
7918 checking the type of arguments to functions and operators, and making
7919 sure mathematical overflows are caught at run time. Checks such as
7920 these help to ensure a program's correctness once it has been compiled
7921 by eliminating type mismatches, and providing active checks for range
7922 errors when your program is running.
7924 @value{GDBN} can check for conditions like the above if you wish.
7925 Although @value{GDBN} does not check the statements in your program, it
7926 can check expressions entered directly into @value{GDBN} for evaluation via
7927 the @code{print} command, for example. As with the working language,
7928 @value{GDBN} can also decide whether or not to check automatically based on
7929 your program's source language. @xref{Support, ,Supported languages},
7930 for the default settings of supported languages.
7933 * Type Checking:: An overview of type checking
7934 * Range Checking:: An overview of range checking
7937 @cindex type checking
7938 @cindex checks, type
7940 @subsection An overview of type checking
7942 Some languages, such as Modula-2, are strongly typed, meaning that the
7943 arguments to operators and functions have to be of the correct type,
7944 otherwise an error occurs. These checks prevent type mismatch
7945 errors from ever causing any run-time problems. For example,
7953 The second example fails because the @code{CARDINAL} 1 is not
7954 type-compatible with the @code{REAL} 2.3.
7956 For the expressions you use in @value{GDBN} commands, you can tell the
7957 @value{GDBN} type checker to skip checking;
7958 to treat any mismatches as errors and abandon the expression;
7959 or to only issue warnings when type mismatches occur,
7960 but evaluate the expression anyway. When you choose the last of
7961 these, @value{GDBN} evaluates expressions like the second example above, but
7962 also issues a warning.
7964 Even if you turn type checking off, there may be other reasons
7965 related to type that prevent @value{GDBN} from evaluating an expression.
7966 For instance, @value{GDBN} does not know how to add an @code{int} and
7967 a @code{struct foo}. These particular type errors have nothing to do
7968 with the language in use, and usually arise from expressions, such as
7969 the one described above, which make little sense to evaluate anyway.
7971 Each language defines to what degree it is strict about type. For
7972 instance, both Modula-2 and C require the arguments to arithmetical
7973 operators to be numbers. In C, enumerated types and pointers can be
7974 represented as numbers, so that they are valid arguments to mathematical
7975 operators. @xref{Support, ,Supported languages}, for further
7976 details on specific languages.
7978 @value{GDBN} provides some additional commands for controlling the type checker:
7980 @kindex set check type
7981 @kindex show check type
7983 @item set check type auto
7984 Set type checking on or off based on the current working language.
7985 @xref{Support, ,Supported languages}, for the default settings for
7988 @item set check type on
7989 @itemx set check type off
7990 Set type checking on or off, overriding the default setting for the
7991 current working language. Issue a warning if the setting does not
7992 match the language default. If any type mismatches occur in
7993 evaluating an expression while type checking is on, @value{GDBN} prints a
7994 message and aborts evaluation of the expression.
7996 @item set check type warn
7997 Cause the type checker to issue warnings, but to always attempt to
7998 evaluate the expression. Evaluating the expression may still
7999 be impossible for other reasons. For example, @value{GDBN} cannot add
8000 numbers and structures.
8003 Show the current setting of the type checker, and whether or not @value{GDBN}
8004 is setting it automatically.
8007 @cindex range checking
8008 @cindex checks, range
8009 @node Range Checking
8010 @subsection An overview of range checking
8012 In some languages (such as Modula-2), it is an error to exceed the
8013 bounds of a type; this is enforced with run-time checks. Such range
8014 checking is meant to ensure program correctness by making sure
8015 computations do not overflow, or indices on an array element access do
8016 not exceed the bounds of the array.
8018 For expressions you use in @value{GDBN} commands, you can tell
8019 @value{GDBN} to treat range errors in one of three ways: ignore them,
8020 always treat them as errors and abandon the expression, or issue
8021 warnings but evaluate the expression anyway.
8023 A range error can result from numerical overflow, from exceeding an
8024 array index bound, or when you type a constant that is not a member
8025 of any type. Some languages, however, do not treat overflows as an
8026 error. In many implementations of C, mathematical overflow causes the
8027 result to ``wrap around'' to lower values---for example, if @var{m} is
8028 the largest integer value, and @var{s} is the smallest, then
8031 @var{m} + 1 @result{} @var{s}
8034 This, too, is specific to individual languages, and in some cases
8035 specific to individual compilers or machines. @xref{Support, ,
8036 Supported languages}, for further details on specific languages.
8038 @value{GDBN} provides some additional commands for controlling the range checker:
8040 @kindex set check range
8041 @kindex show check range
8043 @item set check range auto
8044 Set range checking on or off based on the current working language.
8045 @xref{Support, ,Supported languages}, for the default settings for
8048 @item set check range on
8049 @itemx set check range off
8050 Set range checking on or off, overriding the default setting for the
8051 current working language. A warning is issued if the setting does not
8052 match the language default. If a range error occurs and range checking is on,
8053 then a message is printed and evaluation of the expression is aborted.
8055 @item set check range warn
8056 Output messages when the @value{GDBN} range checker detects a range error,
8057 but attempt to evaluate the expression anyway. Evaluating the
8058 expression may still be impossible for other reasons, such as accessing
8059 memory that the process does not own (a typical example from many Unix
8063 Show the current setting of the range checker, and whether or not it is
8064 being set automatically by @value{GDBN}.
8068 @section Supported languages
8070 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, assembly, Modula-2, and Ada.
8071 @c This is false ...
8072 Some @value{GDBN} features may be used in expressions regardless of the
8073 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
8074 and the @samp{@{type@}addr} construct (@pxref{Expressions,
8075 ,Expressions}) can be used with the constructs of any supported
8078 The following sections detail to what degree each source language is
8079 supported by @value{GDBN}. These sections are not meant to be language
8080 tutorials or references, but serve only as a reference guide to what the
8081 @value{GDBN} expression parser accepts, and what input and output
8082 formats should look like for different languages. There are many good
8083 books written on each of these languages; please look to these for a
8084 language reference or tutorial.
8088 * Objective-C:: Objective-C
8089 * Modula-2:: Modula-2
8094 @subsection C and C@t{++}
8096 @cindex C and C@t{++}
8097 @cindex expressions in C or C@t{++}
8099 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
8100 to both languages. Whenever this is the case, we discuss those languages
8104 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
8105 @cindex @sc{gnu} C@t{++}
8106 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
8107 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
8108 effectively, you must compile your C@t{++} programs with a supported
8109 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
8110 compiler (@code{aCC}).
8112 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
8113 format; if it doesn't work on your system, try the stabs+ debugging
8114 format. You can select those formats explicitly with the @code{g++}
8115 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
8116 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
8117 CC, gcc.info, Using @sc{gnu} CC}.
8120 * C Operators:: C and C@t{++} operators
8121 * C Constants:: C and C@t{++} constants
8122 * C plus plus expressions:: C@t{++} expressions
8123 * C Defaults:: Default settings for C and C@t{++}
8124 * C Checks:: C and C@t{++} type and range checks
8125 * Debugging C:: @value{GDBN} and C
8126 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
8130 @subsubsection C and C@t{++} operators
8132 @cindex C and C@t{++} operators
8134 Operators must be defined on values of specific types. For instance,
8135 @code{+} is defined on numbers, but not on structures. Operators are
8136 often defined on groups of types.
8138 For the purposes of C and C@t{++}, the following definitions hold:
8143 @emph{Integral types} include @code{int} with any of its storage-class
8144 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
8147 @emph{Floating-point types} include @code{float}, @code{double}, and
8148 @code{long double} (if supported by the target platform).
8151 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
8154 @emph{Scalar types} include all of the above.
8159 The following operators are supported. They are listed here
8160 in order of increasing precedence:
8164 The comma or sequencing operator. Expressions in a comma-separated list
8165 are evaluated from left to right, with the result of the entire
8166 expression being the last expression evaluated.
8169 Assignment. The value of an assignment expression is the value
8170 assigned. Defined on scalar types.
8173 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
8174 and translated to @w{@code{@var{a} = @var{a op b}}}.
8175 @w{@code{@var{op}=}} and @code{=} have the same precedence.
8176 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
8177 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
8180 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
8181 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
8185 Logical @sc{or}. Defined on integral types.
8188 Logical @sc{and}. Defined on integral types.
8191 Bitwise @sc{or}. Defined on integral types.
8194 Bitwise exclusive-@sc{or}. Defined on integral types.
8197 Bitwise @sc{and}. Defined on integral types.
8200 Equality and inequality. Defined on scalar types. The value of these
8201 expressions is 0 for false and non-zero for true.
8203 @item <@r{, }>@r{, }<=@r{, }>=
8204 Less than, greater than, less than or equal, greater than or equal.
8205 Defined on scalar types. The value of these expressions is 0 for false
8206 and non-zero for true.
8209 left shift, and right shift. Defined on integral types.
8212 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8215 Addition and subtraction. Defined on integral types, floating-point types and
8218 @item *@r{, }/@r{, }%
8219 Multiplication, division, and modulus. Multiplication and division are
8220 defined on integral and floating-point types. Modulus is defined on
8224 Increment and decrement. When appearing before a variable, the
8225 operation is performed before the variable is used in an expression;
8226 when appearing after it, the variable's value is used before the
8227 operation takes place.
8230 Pointer dereferencing. Defined on pointer types. Same precedence as
8234 Address operator. Defined on variables. Same precedence as @code{++}.
8236 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
8237 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
8238 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
8239 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
8243 Negative. Defined on integral and floating-point types. Same
8244 precedence as @code{++}.
8247 Logical negation. Defined on integral types. Same precedence as
8251 Bitwise complement operator. Defined on integral types. Same precedence as
8256 Structure member, and pointer-to-structure member. For convenience,
8257 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
8258 pointer based on the stored type information.
8259 Defined on @code{struct} and @code{union} data.
8262 Dereferences of pointers to members.
8265 Array indexing. @code{@var{a}[@var{i}]} is defined as
8266 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
8269 Function parameter list. Same precedence as @code{->}.
8272 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
8273 and @code{class} types.
8276 Doubled colons also represent the @value{GDBN} scope operator
8277 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
8281 If an operator is redefined in the user code, @value{GDBN} usually
8282 attempts to invoke the redefined version instead of using the operator's
8290 @subsubsection C and C@t{++} constants
8292 @cindex C and C@t{++} constants
8294 @value{GDBN} allows you to express the constants of C and C@t{++} in the
8299 Integer constants are a sequence of digits. Octal constants are
8300 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
8301 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
8302 @samp{l}, specifying that the constant should be treated as a
8306 Floating point constants are a sequence of digits, followed by a decimal
8307 point, followed by a sequence of digits, and optionally followed by an
8308 exponent. An exponent is of the form:
8309 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
8310 sequence of digits. The @samp{+} is optional for positive exponents.
8311 A floating-point constant may also end with a letter @samp{f} or
8312 @samp{F}, specifying that the constant should be treated as being of
8313 the @code{float} (as opposed to the default @code{double}) type; or with
8314 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
8318 Enumerated constants consist of enumerated identifiers, or their
8319 integral equivalents.
8322 Character constants are a single character surrounded by single quotes
8323 (@code{'}), or a number---the ordinal value of the corresponding character
8324 (usually its @sc{ascii} value). Within quotes, the single character may
8325 be represented by a letter or by @dfn{escape sequences}, which are of
8326 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
8327 of the character's ordinal value; or of the form @samp{\@var{x}}, where
8328 @samp{@var{x}} is a predefined special character---for example,
8329 @samp{\n} for newline.
8332 String constants are a sequence of character constants surrounded by
8333 double quotes (@code{"}). Any valid character constant (as described
8334 above) may appear. Double quotes within the string must be preceded by
8335 a backslash, so for instance @samp{"a\"b'c"} is a string of five
8339 Pointer constants are an integral value. You can also write pointers
8340 to constants using the C operator @samp{&}.
8343 Array constants are comma-separated lists surrounded by braces @samp{@{}
8344 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
8345 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
8346 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
8350 * C plus plus expressions::
8357 @node C plus plus expressions
8358 @subsubsection C@t{++} expressions
8360 @cindex expressions in C@t{++}
8361 @value{GDBN} expression handling can interpret most C@t{++} expressions.
8363 @cindex debugging C@t{++} programs
8364 @cindex C@t{++} compilers
8365 @cindex debug formats and C@t{++}
8366 @cindex @value{NGCC} and C@t{++}
8368 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
8369 proper compiler and the proper debug format. Currently, @value{GDBN}
8370 works best when debugging C@t{++} code that is compiled with
8371 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
8372 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
8373 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
8374 stabs+ as their default debug format, so you usually don't need to
8375 specify a debug format explicitly. Other compilers and/or debug formats
8376 are likely to work badly or not at all when using @value{GDBN} to debug
8382 @cindex member functions
8384 Member function calls are allowed; you can use expressions like
8387 count = aml->GetOriginal(x, y)
8390 @vindex this@r{, inside C@t{++} member functions}
8391 @cindex namespace in C@t{++}
8393 While a member function is active (in the selected stack frame), your
8394 expressions have the same namespace available as the member function;
8395 that is, @value{GDBN} allows implicit references to the class instance
8396 pointer @code{this} following the same rules as C@t{++}.
8398 @cindex call overloaded functions
8399 @cindex overloaded functions, calling
8400 @cindex type conversions in C@t{++}
8402 You can call overloaded functions; @value{GDBN} resolves the function
8403 call to the right definition, with some restrictions. @value{GDBN} does not
8404 perform overload resolution involving user-defined type conversions,
8405 calls to constructors, or instantiations of templates that do not exist
8406 in the program. It also cannot handle ellipsis argument lists or
8409 It does perform integral conversions and promotions, floating-point
8410 promotions, arithmetic conversions, pointer conversions, conversions of
8411 class objects to base classes, and standard conversions such as those of
8412 functions or arrays to pointers; it requires an exact match on the
8413 number of function arguments.
8415 Overload resolution is always performed, unless you have specified
8416 @code{set overload-resolution off}. @xref{Debugging C plus plus,
8417 ,@value{GDBN} features for C@t{++}}.
8419 You must specify @code{set overload-resolution off} in order to use an
8420 explicit function signature to call an overloaded function, as in
8422 p 'foo(char,int)'('x', 13)
8425 The @value{GDBN} command-completion facility can simplify this;
8426 see @ref{Completion, ,Command completion}.
8428 @cindex reference declarations
8430 @value{GDBN} understands variables declared as C@t{++} references; you can use
8431 them in expressions just as you do in C@t{++} source---they are automatically
8434 In the parameter list shown when @value{GDBN} displays a frame, the values of
8435 reference variables are not displayed (unlike other variables); this
8436 avoids clutter, since references are often used for large structures.
8437 The @emph{address} of a reference variable is always shown, unless
8438 you have specified @samp{set print address off}.
8441 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
8442 expressions can use it just as expressions in your program do. Since
8443 one scope may be defined in another, you can use @code{::} repeatedly if
8444 necessary, for example in an expression like
8445 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
8446 resolving name scope by reference to source files, in both C and C@t{++}
8447 debugging (@pxref{Variables, ,Program variables}).
8450 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
8451 calling virtual functions correctly, printing out virtual bases of
8452 objects, calling functions in a base subobject, casting objects, and
8453 invoking user-defined operators.
8456 @subsubsection C and C@t{++} defaults
8458 @cindex C and C@t{++} defaults
8460 If you allow @value{GDBN} to set type and range checking automatically, they
8461 both default to @code{off} whenever the working language changes to
8462 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
8463 selects the working language.
8465 If you allow @value{GDBN} to set the language automatically, it
8466 recognizes source files whose names end with @file{.c}, @file{.C}, or
8467 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
8468 these files, it sets the working language to C or C@t{++}.
8469 @xref{Automatically, ,Having @value{GDBN} infer the source language},
8470 for further details.
8472 @c Type checking is (a) primarily motivated by Modula-2, and (b)
8473 @c unimplemented. If (b) changes, it might make sense to let this node
8474 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
8477 @subsubsection C and C@t{++} type and range checks
8479 @cindex C and C@t{++} checks
8481 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
8482 is not used. However, if you turn type checking on, @value{GDBN}
8483 considers two variables type equivalent if:
8487 The two variables are structured and have the same structure, union, or
8491 The two variables have the same type name, or types that have been
8492 declared equivalent through @code{typedef}.
8495 @c leaving this out because neither J Gilmore nor R Pesch understand it.
8498 The two @code{struct}, @code{union}, or @code{enum} variables are
8499 declared in the same declaration. (Note: this may not be true for all C
8504 Range checking, if turned on, is done on mathematical operations. Array
8505 indices are not checked, since they are often used to index a pointer
8506 that is not itself an array.
8509 @subsubsection @value{GDBN} and C
8511 The @code{set print union} and @code{show print union} commands apply to
8512 the @code{union} type. When set to @samp{on}, any @code{union} that is
8513 inside a @code{struct} or @code{class} is also printed. Otherwise, it
8514 appears as @samp{@{...@}}.
8516 The @code{@@} operator aids in the debugging of dynamic arrays, formed
8517 with pointers and a memory allocation function. @xref{Expressions,
8521 * Debugging C plus plus::
8524 @node Debugging C plus plus
8525 @subsubsection @value{GDBN} features for C@t{++}
8527 @cindex commands for C@t{++}
8529 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
8530 designed specifically for use with C@t{++}. Here is a summary:
8533 @cindex break in overloaded functions
8534 @item @r{breakpoint menus}
8535 When you want a breakpoint in a function whose name is overloaded,
8536 @value{GDBN} breakpoint menus help you specify which function definition
8537 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
8539 @cindex overloading in C@t{++}
8540 @item rbreak @var{regex}
8541 Setting breakpoints using regular expressions is helpful for setting
8542 breakpoints on overloaded functions that are not members of any special
8544 @xref{Set Breaks, ,Setting breakpoints}.
8546 @cindex C@t{++} exception handling
8549 Debug C@t{++} exception handling using these commands. @xref{Set
8550 Catchpoints, , Setting catchpoints}.
8553 @item ptype @var{typename}
8554 Print inheritance relationships as well as other information for type
8556 @xref{Symbols, ,Examining the Symbol Table}.
8558 @cindex C@t{++} symbol display
8559 @item set print demangle
8560 @itemx show print demangle
8561 @itemx set print asm-demangle
8562 @itemx show print asm-demangle
8563 Control whether C@t{++} symbols display in their source form, both when
8564 displaying code as C@t{++} source and when displaying disassemblies.
8565 @xref{Print Settings, ,Print settings}.
8567 @item set print object
8568 @itemx show print object
8569 Choose whether to print derived (actual) or declared types of objects.
8570 @xref{Print Settings, ,Print settings}.
8572 @item set print vtbl
8573 @itemx show print vtbl
8574 Control the format for printing virtual function tables.
8575 @xref{Print Settings, ,Print settings}.
8576 (The @code{vtbl} commands do not work on programs compiled with the HP
8577 ANSI C@t{++} compiler (@code{aCC}).)
8579 @kindex set overload-resolution
8580 @cindex overloaded functions, overload resolution
8581 @item set overload-resolution on
8582 Enable overload resolution for C@t{++} expression evaluation. The default
8583 is on. For overloaded functions, @value{GDBN} evaluates the arguments
8584 and searches for a function whose signature matches the argument types,
8585 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
8586 expressions}, for details). If it cannot find a match, it emits a
8589 @item set overload-resolution off
8590 Disable overload resolution for C@t{++} expression evaluation. For
8591 overloaded functions that are not class member functions, @value{GDBN}
8592 chooses the first function of the specified name that it finds in the
8593 symbol table, whether or not its arguments are of the correct type. For
8594 overloaded functions that are class member functions, @value{GDBN}
8595 searches for a function whose signature @emph{exactly} matches the
8598 @item @r{Overloaded symbol names}
8599 You can specify a particular definition of an overloaded symbol, using
8600 the same notation that is used to declare such symbols in C@t{++}: type
8601 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
8602 also use the @value{GDBN} command-line word completion facilities to list the
8603 available choices, or to finish the type list for you.
8604 @xref{Completion,, Command completion}, for details on how to do this.
8608 @subsection Objective-C
8611 This section provides information about some commands and command
8612 options that are useful for debugging Objective-C code.
8615 * Method Names in Commands::
8616 * The Print Command with Objective-C::
8619 @node Method Names in Commands, The Print Command with Objective-C, Objective-C, Objective-C
8620 @subsubsection Method Names in Commands
8622 The following commands have been extended to accept Objective-C method
8623 names as line specifications:
8625 @kindex clear@r{, and Objective-C}
8626 @kindex break@r{, and Objective-C}
8627 @kindex info line@r{, and Objective-C}
8628 @kindex jump@r{, and Objective-C}
8629 @kindex list@r{, and Objective-C}
8633 @item @code{info line}
8638 A fully qualified Objective-C method name is specified as
8641 -[@var{Class} @var{methodName}]
8644 where the minus sign is used to indicate an instance method and a
8645 plus sign (not shown) is used to indicate a class method. The class
8646 name @var{Class} and method name @var{methodName} are enclosed in
8647 brackets, similar to the way messages are specified in Objective-C
8648 source code. For example, to set a breakpoint at the @code{create}
8649 instance method of class @code{Fruit} in the program currently being
8653 break -[Fruit create]
8656 To list ten program lines around the @code{initialize} class method,
8660 list +[NSText initialize]
8663 In the current version of @value{GDBN}, the plus or minus sign is
8664 required. In future versions of @value{GDBN}, the plus or minus
8665 sign will be optional, but you can use it to narrow the search. It
8666 is also possible to specify just a method name:
8672 You must specify the complete method name, including any colons. If
8673 your program's source files contain more than one @code{create} method,
8674 you'll be presented with a numbered list of classes that implement that
8675 method. Indicate your choice by number, or type @samp{0} to exit if
8678 As another example, to clear a breakpoint established at the
8679 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
8682 clear -[NSWindow makeKeyAndOrderFront:]
8685 @node The Print Command with Objective-C
8686 @subsubsection The Print Command With Objective-C
8687 @kindex print-object
8688 @kindex po @r{(@code{print-object})}
8690 The print command has also been extended to accept methods. For example:
8693 print -[@var{object} hash]
8696 @cindex print an Objective-C object description
8697 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
8699 will tell @value{GDBN} to send the @code{hash} message to @var{object}
8700 and print the result. Also, an additional command has been added,
8701 @code{print-object} or @code{po} for short, which is meant to print
8702 the description of an object. However, this command may only work
8703 with certain Objective-C libraries that have a particular hook
8704 function, @code{_NSPrintForDebugger}, defined.
8706 @node Modula-2, Ada, Objective-C, Support
8707 @subsection Modula-2
8709 @cindex Modula-2, @value{GDBN} support
8711 The extensions made to @value{GDBN} to support Modula-2 only support
8712 output from the @sc{gnu} Modula-2 compiler (which is currently being
8713 developed). Other Modula-2 compilers are not currently supported, and
8714 attempting to debug executables produced by them is most likely
8715 to give an error as @value{GDBN} reads in the executable's symbol
8718 @cindex expressions in Modula-2
8720 * M2 Operators:: Built-in operators
8721 * Built-In Func/Proc:: Built-in functions and procedures
8722 * M2 Constants:: Modula-2 constants
8723 * M2 Defaults:: Default settings for Modula-2
8724 * Deviations:: Deviations from standard Modula-2
8725 * M2 Checks:: Modula-2 type and range checks
8726 * M2 Scope:: The scope operators @code{::} and @code{.}
8727 * GDB/M2:: @value{GDBN} and Modula-2
8731 @subsubsection Operators
8732 @cindex Modula-2 operators
8734 Operators must be defined on values of specific types. For instance,
8735 @code{+} is defined on numbers, but not on structures. Operators are
8736 often defined on groups of types. For the purposes of Modula-2, the
8737 following definitions hold:
8742 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
8746 @emph{Character types} consist of @code{CHAR} and its subranges.
8749 @emph{Floating-point types} consist of @code{REAL}.
8752 @emph{Pointer types} consist of anything declared as @code{POINTER TO
8756 @emph{Scalar types} consist of all of the above.
8759 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
8762 @emph{Boolean types} consist of @code{BOOLEAN}.
8766 The following operators are supported, and appear in order of
8767 increasing precedence:
8771 Function argument or array index separator.
8774 Assignment. The value of @var{var} @code{:=} @var{value} is
8778 Less than, greater than on integral, floating-point, or enumerated
8782 Less than or equal to, greater than or equal to
8783 on integral, floating-point and enumerated types, or set inclusion on
8784 set types. Same precedence as @code{<}.
8786 @item =@r{, }<>@r{, }#
8787 Equality and two ways of expressing inequality, valid on scalar types.
8788 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
8789 available for inequality, since @code{#} conflicts with the script
8793 Set membership. Defined on set types and the types of their members.
8794 Same precedence as @code{<}.
8797 Boolean disjunction. Defined on boolean types.
8800 Boolean conjunction. Defined on boolean types.
8803 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8806 Addition and subtraction on integral and floating-point types, or union
8807 and difference on set types.
8810 Multiplication on integral and floating-point types, or set intersection
8814 Division on floating-point types, or symmetric set difference on set
8815 types. Same precedence as @code{*}.
8818 Integer division and remainder. Defined on integral types. Same
8819 precedence as @code{*}.
8822 Negative. Defined on @code{INTEGER} and @code{REAL} data.
8825 Pointer dereferencing. Defined on pointer types.
8828 Boolean negation. Defined on boolean types. Same precedence as
8832 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
8833 precedence as @code{^}.
8836 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
8839 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
8843 @value{GDBN} and Modula-2 scope operators.
8847 @emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
8848 treats the use of the operator @code{IN}, or the use of operators
8849 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
8850 @code{<=}, and @code{>=} on sets as an error.
8854 @node Built-In Func/Proc
8855 @subsubsection Built-in functions and procedures
8856 @cindex Modula-2 built-ins
8858 Modula-2 also makes available several built-in procedures and functions.
8859 In describing these, the following metavariables are used:
8864 represents an @code{ARRAY} variable.
8867 represents a @code{CHAR} constant or variable.
8870 represents a variable or constant of integral type.
8873 represents an identifier that belongs to a set. Generally used in the
8874 same function with the metavariable @var{s}. The type of @var{s} should
8875 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
8878 represents a variable or constant of integral or floating-point type.
8881 represents a variable or constant of floating-point type.
8887 represents a variable.
8890 represents a variable or constant of one of many types. See the
8891 explanation of the function for details.
8894 All Modula-2 built-in procedures also return a result, described below.
8898 Returns the absolute value of @var{n}.
8901 If @var{c} is a lower case letter, it returns its upper case
8902 equivalent, otherwise it returns its argument.
8905 Returns the character whose ordinal value is @var{i}.
8908 Decrements the value in the variable @var{v} by one. Returns the new value.
8910 @item DEC(@var{v},@var{i})
8911 Decrements the value in the variable @var{v} by @var{i}. Returns the
8914 @item EXCL(@var{m},@var{s})
8915 Removes the element @var{m} from the set @var{s}. Returns the new
8918 @item FLOAT(@var{i})
8919 Returns the floating point equivalent of the integer @var{i}.
8922 Returns the index of the last member of @var{a}.
8925 Increments the value in the variable @var{v} by one. Returns the new value.
8927 @item INC(@var{v},@var{i})
8928 Increments the value in the variable @var{v} by @var{i}. Returns the
8931 @item INCL(@var{m},@var{s})
8932 Adds the element @var{m} to the set @var{s} if it is not already
8933 there. Returns the new set.
8936 Returns the maximum value of the type @var{t}.
8939 Returns the minimum value of the type @var{t}.
8942 Returns boolean TRUE if @var{i} is an odd number.
8945 Returns the ordinal value of its argument. For example, the ordinal
8946 value of a character is its @sc{ascii} value (on machines supporting the
8947 @sc{ascii} character set). @var{x} must be of an ordered type, which include
8948 integral, character and enumerated types.
8951 Returns the size of its argument. @var{x} can be a variable or a type.
8953 @item TRUNC(@var{r})
8954 Returns the integral part of @var{r}.
8956 @item VAL(@var{t},@var{i})
8957 Returns the member of the type @var{t} whose ordinal value is @var{i}.
8961 @emph{Warning:} Sets and their operations are not yet supported, so
8962 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
8966 @cindex Modula-2 constants
8968 @subsubsection Constants
8970 @value{GDBN} allows you to express the constants of Modula-2 in the following
8976 Integer constants are simply a sequence of digits. When used in an
8977 expression, a constant is interpreted to be type-compatible with the
8978 rest of the expression. Hexadecimal integers are specified by a
8979 trailing @samp{H}, and octal integers by a trailing @samp{B}.
8982 Floating point constants appear as a sequence of digits, followed by a
8983 decimal point and another sequence of digits. An optional exponent can
8984 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
8985 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
8986 digits of the floating point constant must be valid decimal (base 10)
8990 Character constants consist of a single character enclosed by a pair of
8991 like quotes, either single (@code{'}) or double (@code{"}). They may
8992 also be expressed by their ordinal value (their @sc{ascii} value, usually)
8993 followed by a @samp{C}.
8996 String constants consist of a sequence of characters enclosed by a
8997 pair of like quotes, either single (@code{'}) or double (@code{"}).
8998 Escape sequences in the style of C are also allowed. @xref{C
8999 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
9003 Enumerated constants consist of an enumerated identifier.
9006 Boolean constants consist of the identifiers @code{TRUE} and
9010 Pointer constants consist of integral values only.
9013 Set constants are not yet supported.
9017 @subsubsection Modula-2 defaults
9018 @cindex Modula-2 defaults
9020 If type and range checking are set automatically by @value{GDBN}, they
9021 both default to @code{on} whenever the working language changes to
9022 Modula-2. This happens regardless of whether you or @value{GDBN}
9023 selected the working language.
9025 If you allow @value{GDBN} to set the language automatically, then entering
9026 code compiled from a file whose name ends with @file{.mod} sets the
9027 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
9028 the language automatically}, for further details.
9031 @subsubsection Deviations from standard Modula-2
9032 @cindex Modula-2, deviations from
9034 A few changes have been made to make Modula-2 programs easier to debug.
9035 This is done primarily via loosening its type strictness:
9039 Unlike in standard Modula-2, pointer constants can be formed by
9040 integers. This allows you to modify pointer variables during
9041 debugging. (In standard Modula-2, the actual address contained in a
9042 pointer variable is hidden from you; it can only be modified
9043 through direct assignment to another pointer variable or expression that
9044 returned a pointer.)
9047 C escape sequences can be used in strings and characters to represent
9048 non-printable characters. @value{GDBN} prints out strings with these
9049 escape sequences embedded. Single non-printable characters are
9050 printed using the @samp{CHR(@var{nnn})} format.
9053 The assignment operator (@code{:=}) returns the value of its right-hand
9057 All built-in procedures both modify @emph{and} return their argument.
9061 @subsubsection Modula-2 type and range checks
9062 @cindex Modula-2 checks
9065 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
9068 @c FIXME remove warning when type/range checks added
9070 @value{GDBN} considers two Modula-2 variables type equivalent if:
9074 They are of types that have been declared equivalent via a @code{TYPE
9075 @var{t1} = @var{t2}} statement
9078 They have been declared on the same line. (Note: This is true of the
9079 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
9082 As long as type checking is enabled, any attempt to combine variables
9083 whose types are not equivalent is an error.
9085 Range checking is done on all mathematical operations, assignment, array
9086 index bounds, and all built-in functions and procedures.
9089 @subsubsection The scope operators @code{::} and @code{.}
9091 @cindex @code{.}, Modula-2 scope operator
9092 @cindex colon, doubled as scope operator
9094 @vindex colon-colon@r{, in Modula-2}
9095 @c Info cannot handle :: but TeX can.
9098 @vindex ::@r{, in Modula-2}
9101 There are a few subtle differences between the Modula-2 scope operator
9102 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
9107 @var{module} . @var{id}
9108 @var{scope} :: @var{id}
9112 where @var{scope} is the name of a module or a procedure,
9113 @var{module} the name of a module, and @var{id} is any declared
9114 identifier within your program, except another module.
9116 Using the @code{::} operator makes @value{GDBN} search the scope
9117 specified by @var{scope} for the identifier @var{id}. If it is not
9118 found in the specified scope, then @value{GDBN} searches all scopes
9119 enclosing the one specified by @var{scope}.
9121 Using the @code{.} operator makes @value{GDBN} search the current scope for
9122 the identifier specified by @var{id} that was imported from the
9123 definition module specified by @var{module}. With this operator, it is
9124 an error if the identifier @var{id} was not imported from definition
9125 module @var{module}, or if @var{id} is not an identifier in
9129 @subsubsection @value{GDBN} and Modula-2
9131 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
9132 Five subcommands of @code{set print} and @code{show print} apply
9133 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
9134 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
9135 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
9136 analogue in Modula-2.
9138 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
9139 with any language, is not useful with Modula-2. Its
9140 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
9141 created in Modula-2 as they can in C or C@t{++}. However, because an
9142 address can be specified by an integral constant, the construct
9143 @samp{@{@var{type}@}@var{adrexp}} is still useful.
9145 @cindex @code{#} in Modula-2
9146 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
9147 interpreted as the beginning of a comment. Use @code{<>} instead.
9153 The extensions made to @value{GDBN} for Ada only support
9154 output from the @sc{gnu} Ada (GNAT) compiler.
9155 Other Ada compilers are not currently supported, and
9156 attempting to debug executables produced by them is most likely
9160 @cindex expressions in Ada
9162 * Ada Mode Intro:: General remarks on the Ada syntax
9163 and semantics supported by Ada mode
9165 * Omissions from Ada:: Restrictions on the Ada expression syntax.
9166 * Additions to Ada:: Extensions of the Ada expression syntax.
9167 * Stopping Before Main Program:: Debugging the program during elaboration.
9168 * Ada Glitches:: Known peculiarities of Ada mode.
9171 @node Ada Mode Intro
9172 @subsubsection Introduction
9173 @cindex Ada mode, general
9175 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
9176 syntax, with some extensions.
9177 The philosophy behind the design of this subset is
9181 That @value{GDBN} should provide basic literals and access to operations for
9182 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
9183 leaving more sophisticated computations to subprograms written into the
9184 program (which therefore may be called from @value{GDBN}).
9187 That type safety and strict adherence to Ada language restrictions
9188 are not particularly important to the @value{GDBN} user.
9191 That brevity is important to the @value{GDBN} user.
9194 Thus, for brevity, the debugger acts as if there were
9195 implicit @code{with} and @code{use} clauses in effect for all user-written
9196 packages, making it unnecessary to fully qualify most names with
9197 their packages, regardless of context. Where this causes ambiguity,
9198 @value{GDBN} asks the user's intent.
9200 The debugger will start in Ada mode if it detects an Ada main program.
9201 As for other languages, it will enter Ada mode when stopped in a program that
9202 was translated from an Ada source file.
9204 While in Ada mode, you may use `@t{--}' for comments. This is useful
9205 mostly for documenting command files. The standard @value{GDBN} comment
9206 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
9207 middle (to allow based literals).
9209 The debugger supports limited overloading. Given a subprogram call in which
9210 the function symbol has multiple definitions, it will use the number of
9211 actual parameters and some information about their types to attempt to narrow
9212 the set of definitions. It also makes very limited use of context, preferring
9213 procedures to functions in the context of the @code{call} command, and
9214 functions to procedures elsewhere.
9216 @node Omissions from Ada
9217 @subsubsection Omissions from Ada
9218 @cindex Ada, omissions from
9220 Here are the notable omissions from the subset:
9224 Only a subset of the attributes are supported:
9228 @t{'First}, @t{'Last}, and @t{'Length}
9229 on array objects (not on types and subtypes).
9232 @t{'Min} and @t{'Max}.
9235 @t{'Pos} and @t{'Val}.
9241 @t{'Range} on array objects (not subtypes), but only as the right
9242 operand of the membership (@code{in}) operator.
9245 @t{'Access}, @t{'Unchecked_Access}, and
9246 @t{'Unrestricted_Access} (a GNAT extension).
9254 @code{Characters.Latin_1} are not available and
9255 concatenation is not implemented. Thus, escape characters in strings are
9256 not currently available.
9259 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
9260 equality of representations. They will generally work correctly
9261 for strings and arrays whose elements have integer or enumeration types.
9262 They may not work correctly for arrays whose element
9263 types have user-defined equality, for arrays of real values
9264 (in particular, IEEE-conformant floating point, because of negative
9265 zeroes and NaNs), and for arrays whose elements contain unused bits with
9266 indeterminate values.
9269 The other component-by-component array operations (@code{and}, @code{or},
9270 @code{xor}, @code{not}, and relational tests other than equality)
9271 are not implemented.
9274 There are no record or array aggregates.
9277 Calls to dispatching subprograms are not implemented.
9280 The overloading algorithm is much more limited (i.e., less selective)
9281 than that of real Ada. It makes only limited use of the context in which a subexpression
9282 appears to resolve its meaning, and it is much looser in its rules for allowing
9283 type matches. As a result, some function calls will be ambiguous, and the user
9284 will be asked to choose the proper resolution.
9287 The @code{new} operator is not implemented.
9290 Entry calls are not implemented.
9293 Aside from printing, arithmetic operations on the native VAX floating-point
9294 formats are not supported.
9297 It is not possible to slice a packed array.
9300 @node Additions to Ada
9301 @subsubsection Additions to Ada
9302 @cindex Ada, deviations from
9304 As it does for other languages, @value{GDBN} makes certain generic
9305 extensions to Ada (@pxref{Expressions}):
9309 If the expression @var{E} is a variable residing in memory
9310 (typically a local variable or array element) and @var{N} is
9311 a positive integer, then @code{@var{E}@@@var{N}} displays the values of
9312 @var{E} and the @var{N}-1 adjacent variables following it in memory as an array.
9313 In Ada, this operator is generally not necessary, since its prime use
9314 is in displaying parts of an array, and slicing will usually do this in Ada.
9315 However, there are occasional uses when debugging programs
9316 in which certain debugging information has been optimized away.
9319 @code{@var{B}::@var{var}} means ``the variable named @var{var} that appears
9320 in function or file @var{B}.'' When @var{B} is a file name, you must typically
9321 surround it in single quotes.
9324 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
9325 @var{type} that appears at address @var{addr}.''
9328 A name starting with @samp{$} is a convenience variable
9329 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
9332 In addition, @value{GDBN} provides a few other shortcuts and outright additions specific
9337 The assignment statement is allowed as an expression, returning
9338 its right-hand operand as its value. Thus, you may enter
9342 print A(tmp := y + 1)
9346 The semicolon is allowed as an ``operator,'' returning as its value
9347 the value of its right-hand operand.
9348 This allows, for example,
9349 complex conditional breaks:
9353 condition 1 (report(i); k += 1; A(k) > 100)
9357 Rather than use catenation and symbolic character names to introduce special
9358 characters into strings, one may instead use a special bracket notation,
9359 which is also used to print strings. A sequence of characters of the form
9360 @samp{["@var{XX}"]} within a string or character literal denotes the
9361 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
9362 sequence of characters @samp{["""]} also denotes a single quotation mark
9363 in strings. For example,
9365 "One line.["0a"]Next line.["0a"]"
9368 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF}) after each
9372 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
9373 @t{'Max} is optional (and is ignored in any case). For example, it is valid
9381 When printing arrays, @value{GDBN} uses positional notation when the
9382 array has a lower bound of 1, and uses a modified named notation otherwise.
9383 For example, a one-dimensional array of three integers with a lower bound of 3 might print as
9390 That is, in contrast to valid Ada, only the first component has a @code{=>}
9394 You may abbreviate attributes in expressions with any unique,
9395 multi-character subsequence of
9396 their names (an exact match gets preference).
9397 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
9398 in place of @t{a'length}.
9401 @cindex quoting Ada internal identifiers
9402 Since Ada is case-insensitive, the debugger normally maps identifiers you type
9403 to lower case. The GNAT compiler uses upper-case characters for
9404 some of its internal identifiers, which are normally of no interest to users.
9405 For the rare occasions when you actually have to look at them,
9406 enclose them in angle brackets to avoid the lower-case mapping.
9409 @value{GDBP} print <JMPBUF_SAVE>[0]
9413 Printing an object of class-wide type or dereferencing an
9414 access-to-class-wide value will display all the components of the object's
9415 specific type (as indicated by its run-time tag). Likewise, component
9416 selection on such a value will operate on the specific type of the
9421 @node Stopping Before Main Program
9422 @subsubsection Stopping at the Very Beginning
9424 @cindex breakpointing Ada elaboration code
9425 It is sometimes necessary to debug the program during elaboration, and
9426 before reaching the main procedure.
9427 As defined in the Ada Reference
9428 Manual, the elaboration code is invoked from a procedure called
9429 @code{adainit}. To run your program up to the beginning of
9430 elaboration, simply use the following two commands:
9431 @code{tbreak adainit} and @code{run}.
9434 @subsubsection Known Peculiarities of Ada Mode
9435 @cindex Ada, problems
9437 Besides the omissions listed previously (@pxref{Omissions from Ada}),
9438 we know of several problems with and limitations of Ada mode in
9440 some of which will be fixed with planned future releases of the debugger
9441 and the GNU Ada compiler.
9445 Currently, the debugger
9446 has insufficient information to determine whether certain pointers represent
9447 pointers to objects or the objects themselves.
9448 Thus, the user may have to tack an extra @code{.all} after an expression
9449 to get it printed properly.
9452 Static constants that the compiler chooses not to materialize as objects in
9453 storage are invisible to the debugger.
9456 Named parameter associations in function argument lists are ignored (the
9457 argument lists are treated as positional).
9460 Many useful library packages are currently invisible to the debugger.
9463 Fixed-point arithmetic, conversions, input, and output is carried out using
9464 floating-point arithmetic, and may give results that only approximate those on
9468 The type of the @t{'Address} attribute may not be @code{System.Address}.
9471 The GNAT compiler never generates the prefix @code{Standard} for any of
9472 the standard symbols defined by the Ada language. @value{GDBN} knows about
9473 this: it will strip the prefix from names when you use it, and will never
9474 look for a name you have so qualified among local symbols, nor match against
9475 symbols in other packages or subprograms. If you have
9476 defined entities anywhere in your program other than parameters and
9477 local variables whose simple names match names in @code{Standard},
9478 GNAT's lack of qualification here can cause confusion. When this happens,
9479 you can usually resolve the confusion
9480 by qualifying the problematic names with package
9481 @code{Standard} explicitly.
9484 @node Unsupported languages
9485 @section Unsupported languages
9487 @cindex unsupported languages
9488 @cindex minimal language
9489 In addition to the other fully-supported programming languages,
9490 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
9491 It does not represent a real programming language, but provides a set
9492 of capabilities close to what the C or assembly languages provide.
9493 This should allow most simple operations to be performed while debugging
9494 an application that uses a language currently not supported by @value{GDBN}.
9496 If the language is set to @code{auto}, @value{GDBN} will automatically
9497 select this language if the current frame corresponds to an unsupported
9501 @chapter Examining the Symbol Table
9503 The commands described in this chapter allow you to inquire about the
9504 symbols (names of variables, functions and types) defined in your
9505 program. This information is inherent in the text of your program and
9506 does not change as your program executes. @value{GDBN} finds it in your
9507 program's symbol table, in the file indicated when you started @value{GDBN}
9508 (@pxref{File Options, ,Choosing files}), or by one of the
9509 file-management commands (@pxref{Files, ,Commands to specify files}).
9511 @cindex symbol names
9512 @cindex names of symbols
9513 @cindex quoting names
9514 Occasionally, you may need to refer to symbols that contain unusual
9515 characters, which @value{GDBN} ordinarily treats as word delimiters. The
9516 most frequent case is in referring to static variables in other
9517 source files (@pxref{Variables,,Program variables}). File names
9518 are recorded in object files as debugging symbols, but @value{GDBN} would
9519 ordinarily parse a typical file name, like @file{foo.c}, as the three words
9520 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
9521 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
9528 looks up the value of @code{x} in the scope of the file @file{foo.c}.
9531 @kindex info address
9532 @cindex address of a symbol
9533 @item info address @var{symbol}
9534 Describe where the data for @var{symbol} is stored. For a register
9535 variable, this says which register it is kept in. For a non-register
9536 local variable, this prints the stack-frame offset at which the variable
9539 Note the contrast with @samp{print &@var{symbol}}, which does not work
9540 at all for a register variable, and for a stack local variable prints
9541 the exact address of the current instantiation of the variable.
9544 @cindex symbol from address
9545 @item info symbol @var{addr}
9546 Print the name of a symbol which is stored at the address @var{addr}.
9547 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
9548 nearest symbol and an offset from it:
9551 (@value{GDBP}) info symbol 0x54320
9552 _initialize_vx + 396 in section .text
9556 This is the opposite of the @code{info address} command. You can use
9557 it to find out the name of a variable or a function given its address.
9560 @item whatis @var{expr}
9561 Print the data type of expression @var{expr}. @var{expr} is not
9562 actually evaluated, and any side-effecting operations (such as
9563 assignments or function calls) inside it do not take place.
9564 @xref{Expressions, ,Expressions}.
9567 Print the data type of @code{$}, the last value in the value history.
9570 @item ptype @var{typename}
9571 Print a description of data type @var{typename}. @var{typename} may be
9572 the name of a type, or for C code it may have the form @samp{class
9573 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
9574 @var{union-tag}} or @samp{enum @var{enum-tag}}.
9576 @item ptype @var{expr}
9578 Print a description of the type of expression @var{expr}. @code{ptype}
9579 differs from @code{whatis} by printing a detailed description, instead
9580 of just the name of the type.
9582 For example, for this variable declaration:
9585 struct complex @{double real; double imag;@} v;
9589 the two commands give this output:
9593 (@value{GDBP}) whatis v
9594 type = struct complex
9595 (@value{GDBP}) ptype v
9596 type = struct complex @{
9604 As with @code{whatis}, using @code{ptype} without an argument refers to
9605 the type of @code{$}, the last value in the value history.
9608 @item info types @var{regexp}
9610 Print a brief description of all types whose names match @var{regexp}
9611 (or all types in your program, if you supply no argument). Each
9612 complete typename is matched as though it were a complete line; thus,
9613 @samp{i type value} gives information on all types in your program whose
9614 names include the string @code{value}, but @samp{i type ^value$} gives
9615 information only on types whose complete name is @code{value}.
9617 This command differs from @code{ptype} in two ways: first, like
9618 @code{whatis}, it does not print a detailed description; second, it
9619 lists all source files where a type is defined.
9622 @cindex local variables
9623 @item info scope @var{addr}
9624 List all the variables local to a particular scope. This command
9625 accepts a location---a function name, a source line, or an address
9626 preceded by a @samp{*}, and prints all the variables local to the
9627 scope defined by that location. For example:
9630 (@value{GDBP}) @b{info scope command_line_handler}
9631 Scope for command_line_handler:
9632 Symbol rl is an argument at stack/frame offset 8, length 4.
9633 Symbol linebuffer is in static storage at address 0x150a18, length 4.
9634 Symbol linelength is in static storage at address 0x150a1c, length 4.
9635 Symbol p is a local variable in register $esi, length 4.
9636 Symbol p1 is a local variable in register $ebx, length 4.
9637 Symbol nline is a local variable in register $edx, length 4.
9638 Symbol repeat is a local variable at frame offset -8, length 4.
9642 This command is especially useful for determining what data to collect
9643 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
9648 Show information about the current source file---that is, the source file for
9649 the function containing the current point of execution:
9652 the name of the source file, and the directory containing it,
9654 the directory it was compiled in,
9656 its length, in lines,
9658 which programming language it is written in,
9660 whether the executable includes debugging information for that file, and
9661 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
9663 whether the debugging information includes information about
9664 preprocessor macros.
9668 @kindex info sources
9670 Print the names of all source files in your program for which there is
9671 debugging information, organized into two lists: files whose symbols
9672 have already been read, and files whose symbols will be read when needed.
9674 @kindex info functions
9675 @item info functions
9676 Print the names and data types of all defined functions.
9678 @item info functions @var{regexp}
9679 Print the names and data types of all defined functions
9680 whose names contain a match for regular expression @var{regexp}.
9681 Thus, @samp{info fun step} finds all functions whose names
9682 include @code{step}; @samp{info fun ^step} finds those whose names
9683 start with @code{step}. If a function name contains characters
9684 that conflict with the regular expression language (eg.
9685 @samp{operator*()}), they may be quoted with a backslash.
9687 @kindex info variables
9688 @item info variables
9689 Print the names and data types of all variables that are declared
9690 outside of functions (i.e.@: excluding local variables).
9692 @item info variables @var{regexp}
9693 Print the names and data types of all variables (except for local
9694 variables) whose names contain a match for regular expression
9697 @kindex info classes
9699 @itemx info classes @var{regexp}
9700 Display all Objective-C classes in your program, or
9701 (with the @var{regexp} argument) all those matching a particular regular
9704 @kindex info selectors
9705 @item info selectors
9706 @itemx info selectors @var{regexp}
9707 Display all Objective-C selectors in your program, or
9708 (with the @var{regexp} argument) all those matching a particular regular
9712 This was never implemented.
9713 @kindex info methods
9715 @itemx info methods @var{regexp}
9716 The @code{info methods} command permits the user to examine all defined
9717 methods within C@t{++} program, or (with the @var{regexp} argument) a
9718 specific set of methods found in the various C@t{++} classes. Many
9719 C@t{++} classes provide a large number of methods. Thus, the output
9720 from the @code{ptype} command can be overwhelming and hard to use. The
9721 @code{info-methods} command filters the methods, printing only those
9722 which match the regular-expression @var{regexp}.
9725 @cindex reloading symbols
9726 Some systems allow individual object files that make up your program to
9727 be replaced without stopping and restarting your program. For example,
9728 in VxWorks you can simply recompile a defective object file and keep on
9729 running. If you are running on one of these systems, you can allow
9730 @value{GDBN} to reload the symbols for automatically relinked modules:
9733 @kindex set symbol-reloading
9734 @item set symbol-reloading on
9735 Replace symbol definitions for the corresponding source file when an
9736 object file with a particular name is seen again.
9738 @item set symbol-reloading off
9739 Do not replace symbol definitions when encountering object files of the
9740 same name more than once. This is the default state; if you are not
9741 running on a system that permits automatic relinking of modules, you
9742 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
9743 may discard symbols when linking large programs, that may contain
9744 several modules (from different directories or libraries) with the same
9747 @kindex show symbol-reloading
9748 @item show symbol-reloading
9749 Show the current @code{on} or @code{off} setting.
9752 @kindex set opaque-type-resolution
9753 @item set opaque-type-resolution on
9754 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
9755 declared as a pointer to a @code{struct}, @code{class}, or
9756 @code{union}---for example, @code{struct MyType *}---that is used in one
9757 source file although the full declaration of @code{struct MyType} is in
9758 another source file. The default is on.
9760 A change in the setting of this subcommand will not take effect until
9761 the next time symbols for a file are loaded.
9763 @item set opaque-type-resolution off
9764 Tell @value{GDBN} not to resolve opaque types. In this case, the type
9765 is printed as follows:
9767 @{<no data fields>@}
9770 @kindex show opaque-type-resolution
9771 @item show opaque-type-resolution
9772 Show whether opaque types are resolved or not.
9774 @kindex maint print symbols
9776 @kindex maint print psymbols
9777 @cindex partial symbol dump
9778 @item maint print symbols @var{filename}
9779 @itemx maint print psymbols @var{filename}
9780 @itemx maint print msymbols @var{filename}
9781 Write a dump of debugging symbol data into the file @var{filename}.
9782 These commands are used to debug the @value{GDBN} symbol-reading code. Only
9783 symbols with debugging data are included. If you use @samp{maint print
9784 symbols}, @value{GDBN} includes all the symbols for which it has already
9785 collected full details: that is, @var{filename} reflects symbols for
9786 only those files whose symbols @value{GDBN} has read. You can use the
9787 command @code{info sources} to find out which files these are. If you
9788 use @samp{maint print psymbols} instead, the dump shows information about
9789 symbols that @value{GDBN} only knows partially---that is, symbols defined in
9790 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
9791 @samp{maint print msymbols} dumps just the minimal symbol information
9792 required for each object file from which @value{GDBN} has read some symbols.
9793 @xref{Files, ,Commands to specify files}, for a discussion of how
9794 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
9796 @kindex maint info symtabs
9797 @kindex maint info psymtabs
9798 @cindex listing @value{GDBN}'s internal symbol tables
9799 @cindex symbol tables, listing @value{GDBN}'s internal
9800 @cindex full symbol tables, listing @value{GDBN}'s internal
9801 @cindex partial symbol tables, listing @value{GDBN}'s internal
9802 @item maint info symtabs @r{[} @var{regexp} @r{]}
9803 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
9805 List the @code{struct symtab} or @code{struct partial_symtab}
9806 structures whose names match @var{regexp}. If @var{regexp} is not
9807 given, list them all. The output includes expressions which you can
9808 copy into a @value{GDBN} debugging this one to examine a particular
9809 structure in more detail. For example:
9812 (@value{GDBP}) maint info psymtabs dwarf2read
9813 @{ objfile /home/gnu/build/gdb/gdb
9814 ((struct objfile *) 0x82e69d0)
9815 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
9816 ((struct partial_symtab *) 0x8474b10)
9819 text addresses 0x814d3c8 -- 0x8158074
9820 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
9821 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
9825 (@value{GDBP}) maint info symtabs
9829 We see that there is one partial symbol table whose filename contains
9830 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
9831 and we see that @value{GDBN} has not read in any symtabs yet at all.
9832 If we set a breakpoint on a function, that will cause @value{GDBN} to
9833 read the symtab for the compilation unit containing that function:
9836 (@value{GDBP}) break dwarf2_psymtab_to_symtab
9837 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
9839 (@value{GDBP}) maint info symtabs
9840 @{ objfile /home/gnu/build/gdb/gdb
9841 ((struct objfile *) 0x82e69d0)
9842 @{ symtab /home/gnu/src/gdb/dwarf2read.c
9843 ((struct symtab *) 0x86c1f38)
9846 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
9856 @chapter Altering Execution
9858 Once you think you have found an error in your program, you might want to
9859 find out for certain whether correcting the apparent error would lead to
9860 correct results in the rest of the run. You can find the answer by
9861 experiment, using the @value{GDBN} features for altering execution of the
9864 For example, you can store new values into variables or memory
9865 locations, give your program a signal, restart it at a different
9866 address, or even return prematurely from a function.
9869 * Assignment:: Assignment to variables
9870 * Jumping:: Continuing at a different address
9871 * Signaling:: Giving your program a signal
9872 * Returning:: Returning from a function
9873 * Calling:: Calling your program's functions
9874 * Patching:: Patching your program
9878 @section Assignment to variables
9881 @cindex setting variables
9882 To alter the value of a variable, evaluate an assignment expression.
9883 @xref{Expressions, ,Expressions}. For example,
9890 stores the value 4 into the variable @code{x}, and then prints the
9891 value of the assignment expression (which is 4).
9892 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
9893 information on operators in supported languages.
9895 @kindex set variable
9896 @cindex variables, setting
9897 If you are not interested in seeing the value of the assignment, use the
9898 @code{set} command instead of the @code{print} command. @code{set} is
9899 really the same as @code{print} except that the expression's value is
9900 not printed and is not put in the value history (@pxref{Value History,
9901 ,Value history}). The expression is evaluated only for its effects.
9903 If the beginning of the argument string of the @code{set} command
9904 appears identical to a @code{set} subcommand, use the @code{set
9905 variable} command instead of just @code{set}. This command is identical
9906 to @code{set} except for its lack of subcommands. For example, if your
9907 program has a variable @code{width}, you get an error if you try to set
9908 a new value with just @samp{set width=13}, because @value{GDBN} has the
9909 command @code{set width}:
9912 (@value{GDBP}) whatis width
9914 (@value{GDBP}) p width
9916 (@value{GDBP}) set width=47
9917 Invalid syntax in expression.
9921 The invalid expression, of course, is @samp{=47}. In
9922 order to actually set the program's variable @code{width}, use
9925 (@value{GDBP}) set var width=47
9928 Because the @code{set} command has many subcommands that can conflict
9929 with the names of program variables, it is a good idea to use the
9930 @code{set variable} command instead of just @code{set}. For example, if
9931 your program has a variable @code{g}, you run into problems if you try
9932 to set a new value with just @samp{set g=4}, because @value{GDBN} has
9933 the command @code{set gnutarget}, abbreviated @code{set g}:
9937 (@value{GDBP}) whatis g
9941 (@value{GDBP}) set g=4
9945 The program being debugged has been started already.
9946 Start it from the beginning? (y or n) y
9947 Starting program: /home/smith/cc_progs/a.out
9948 "/home/smith/cc_progs/a.out": can't open to read symbols:
9950 (@value{GDBP}) show g
9951 The current BFD target is "=4".
9956 The program variable @code{g} did not change, and you silently set the
9957 @code{gnutarget} to an invalid value. In order to set the variable
9961 (@value{GDBP}) set var g=4
9964 @value{GDBN} allows more implicit conversions in assignments than C; you can
9965 freely store an integer value into a pointer variable or vice versa,
9966 and you can convert any structure to any other structure that is the
9967 same length or shorter.
9968 @comment FIXME: how do structs align/pad in these conversions?
9969 @comment /doc@cygnus.com 18dec1990
9971 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
9972 construct to generate a value of specified type at a specified address
9973 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
9974 to memory location @code{0x83040} as an integer (which implies a certain size
9975 and representation in memory), and
9978 set @{int@}0x83040 = 4
9982 stores the value 4 into that memory location.
9985 @section Continuing at a different address
9987 Ordinarily, when you continue your program, you do so at the place where
9988 it stopped, with the @code{continue} command. You can instead continue at
9989 an address of your own choosing, with the following commands:
9993 @item jump @var{linespec}
9994 Resume execution at line @var{linespec}. Execution stops again
9995 immediately if there is a breakpoint there. @xref{List, ,Printing
9996 source lines}, for a description of the different forms of
9997 @var{linespec}. It is common practice to use the @code{tbreak} command
9998 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
10001 The @code{jump} command does not change the current stack frame, or
10002 the stack pointer, or the contents of any memory location or any
10003 register other than the program counter. If line @var{linespec} is in
10004 a different function from the one currently executing, the results may
10005 be bizarre if the two functions expect different patterns of arguments or
10006 of local variables. For this reason, the @code{jump} command requests
10007 confirmation if the specified line is not in the function currently
10008 executing. However, even bizarre results are predictable if you are
10009 well acquainted with the machine-language code of your program.
10011 @item jump *@var{address}
10012 Resume execution at the instruction at address @var{address}.
10015 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
10016 On many systems, you can get much the same effect as the @code{jump}
10017 command by storing a new value into the register @code{$pc}. The
10018 difference is that this does not start your program running; it only
10019 changes the address of where it @emph{will} run when you continue. For
10027 makes the next @code{continue} command or stepping command execute at
10028 address @code{0x485}, rather than at the address where your program stopped.
10029 @xref{Continuing and Stepping, ,Continuing and stepping}.
10031 The most common occasion to use the @code{jump} command is to back
10032 up---perhaps with more breakpoints set---over a portion of a program
10033 that has already executed, in order to examine its execution in more
10038 @section Giving your program a signal
10042 @item signal @var{signal}
10043 Resume execution where your program stopped, but immediately give it the
10044 signal @var{signal}. @var{signal} can be the name or the number of a
10045 signal. For example, on many systems @code{signal 2} and @code{signal
10046 SIGINT} are both ways of sending an interrupt signal.
10048 Alternatively, if @var{signal} is zero, continue execution without
10049 giving a signal. This is useful when your program stopped on account of
10050 a signal and would ordinary see the signal when resumed with the
10051 @code{continue} command; @samp{signal 0} causes it to resume without a
10054 @code{signal} does not repeat when you press @key{RET} a second time
10055 after executing the command.
10059 Invoking the @code{signal} command is not the same as invoking the
10060 @code{kill} utility from the shell. Sending a signal with @code{kill}
10061 causes @value{GDBN} to decide what to do with the signal depending on
10062 the signal handling tables (@pxref{Signals}). The @code{signal} command
10063 passes the signal directly to your program.
10067 @section Returning from a function
10070 @cindex returning from a function
10073 @itemx return @var{expression}
10074 You can cancel execution of a function call with the @code{return}
10075 command. If you give an
10076 @var{expression} argument, its value is used as the function's return
10080 When you use @code{return}, @value{GDBN} discards the selected stack frame
10081 (and all frames within it). You can think of this as making the
10082 discarded frame return prematurely. If you wish to specify a value to
10083 be returned, give that value as the argument to @code{return}.
10085 This pops the selected stack frame (@pxref{Selection, ,Selecting a
10086 frame}), and any other frames inside of it, leaving its caller as the
10087 innermost remaining frame. That frame becomes selected. The
10088 specified value is stored in the registers used for returning values
10091 The @code{return} command does not resume execution; it leaves the
10092 program stopped in the state that would exist if the function had just
10093 returned. In contrast, the @code{finish} command (@pxref{Continuing
10094 and Stepping, ,Continuing and stepping}) resumes execution until the
10095 selected stack frame returns naturally.
10098 @section Calling program functions
10101 @cindex calling functions
10102 @cindex inferior functions, calling
10103 @item print @var{expr}
10104 Evaluate the expression @var{expr} and displaying the resuling value.
10105 @var{expr} may include calls to functions in the program being
10109 @item call @var{expr}
10110 Evaluate the expression @var{expr} without displaying @code{void}
10113 You can use this variant of the @code{print} command if you want to
10114 execute a function from your program that does not return anything
10115 (a.k.a.@: @dfn{a void function}), but without cluttering the output
10116 with @code{void} returned values that @value{GDBN} will otherwise
10117 print. If the result is not void, it is printed and saved in the
10121 @cindex weak alias functions
10122 Sometimes, a function you wish to call is actually a @dfn{weak alias}
10123 for another function. In such case, @value{GDBN} might not pick up
10124 the type information, including the types of the function arguments,
10125 which causes @value{GDBN} to call the inferior function incorrectly.
10126 As a result, the called function will function erroneously and may
10127 even crash. A solution to that is to use the name of the aliased
10131 @section Patching programs
10133 @cindex patching binaries
10134 @cindex writing into executables
10135 @cindex writing into corefiles
10137 By default, @value{GDBN} opens the file containing your program's
10138 executable code (or the corefile) read-only. This prevents accidental
10139 alterations to machine code; but it also prevents you from intentionally
10140 patching your program's binary.
10142 If you'd like to be able to patch the binary, you can specify that
10143 explicitly with the @code{set write} command. For example, you might
10144 want to turn on internal debugging flags, or even to make emergency
10150 @itemx set write off
10151 If you specify @samp{set write on}, @value{GDBN} opens executable and
10152 core files for both reading and writing; if you specify @samp{set write
10153 off} (the default), @value{GDBN} opens them read-only.
10155 If you have already loaded a file, you must load it again (using the
10156 @code{exec-file} or @code{core-file} command) after changing @code{set
10157 write}, for your new setting to take effect.
10161 Display whether executable files and core files are opened for writing
10162 as well as reading.
10166 @chapter @value{GDBN} Files
10168 @value{GDBN} needs to know the file name of the program to be debugged,
10169 both in order to read its symbol table and in order to start your
10170 program. To debug a core dump of a previous run, you must also tell
10171 @value{GDBN} the name of the core dump file.
10174 * Files:: Commands to specify files
10175 * Separate Debug Files:: Debugging information in separate files
10176 * Symbol Errors:: Errors reading symbol files
10180 @section Commands to specify files
10182 @cindex symbol table
10183 @cindex core dump file
10185 You may want to specify executable and core dump file names. The usual
10186 way to do this is at start-up time, using the arguments to
10187 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
10188 Out of @value{GDBN}}).
10190 Occasionally it is necessary to change to a different file during a
10191 @value{GDBN} session. Or you may run @value{GDBN} and forget to specify
10192 a file you want to use. In these situations the @value{GDBN} commands
10193 to specify new files are useful.
10196 @cindex executable file
10198 @item file @var{filename}
10199 Use @var{filename} as the program to be debugged. It is read for its
10200 symbols and for the contents of pure memory. It is also the program
10201 executed when you use the @code{run} command. If you do not specify a
10202 directory and the file is not found in the @value{GDBN} working directory,
10203 @value{GDBN} uses the environment variable @code{PATH} as a list of
10204 directories to search, just as the shell does when looking for a program
10205 to run. You can change the value of this variable, for both @value{GDBN}
10206 and your program, using the @code{path} command.
10208 On systems with memory-mapped files, an auxiliary file named
10209 @file{@var{filename}.syms} may hold symbol table information for
10210 @var{filename}. If so, @value{GDBN} maps in the symbol table from
10211 @file{@var{filename}.syms}, starting up more quickly. See the
10212 descriptions of the file options @samp{-mapped} and @samp{-readnow}
10213 (available on the command line, see @ref{File Options, , -readnow},
10214 and with the commands @code{file}, @code{symbol-file}, or
10215 @code{add-symbol-file}, described below), for more information.
10218 @code{file} with no argument makes @value{GDBN} discard any information it
10219 has on both executable file and the symbol table.
10222 @item exec-file @r{[} @var{filename} @r{]}
10223 Specify that the program to be run (but not the symbol table) is found
10224 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
10225 if necessary to locate your program. Omitting @var{filename} means to
10226 discard information on the executable file.
10228 @kindex symbol-file
10229 @item symbol-file @r{[} @var{filename} @r{]}
10230 Read symbol table information from file @var{filename}. @code{PATH} is
10231 searched when necessary. Use the @code{file} command to get both symbol
10232 table and program to run from the same file.
10234 @code{symbol-file} with no argument clears out @value{GDBN} information on your
10235 program's symbol table.
10237 The @code{symbol-file} command causes @value{GDBN} to forget the contents
10238 of its convenience variables, the value history, and all breakpoints and
10239 auto-display expressions. This is because they may contain pointers to
10240 the internal data recording symbols and data types, which are part of
10241 the old symbol table data being discarded inside @value{GDBN}.
10243 @code{symbol-file} does not repeat if you press @key{RET} again after
10246 When @value{GDBN} is configured for a particular environment, it
10247 understands debugging information in whatever format is the standard
10248 generated for that environment; you may use either a @sc{gnu} compiler, or
10249 other compilers that adhere to the local conventions.
10250 Best results are usually obtained from @sc{gnu} compilers; for example,
10251 using @code{@value{GCC}} you can generate debugging information for
10254 For most kinds of object files, with the exception of old SVR3 systems
10255 using COFF, the @code{symbol-file} command does not normally read the
10256 symbol table in full right away. Instead, it scans the symbol table
10257 quickly to find which source files and which symbols are present. The
10258 details are read later, one source file at a time, as they are needed.
10260 The purpose of this two-stage reading strategy is to make @value{GDBN}
10261 start up faster. For the most part, it is invisible except for
10262 occasional pauses while the symbol table details for a particular source
10263 file are being read. (The @code{set verbose} command can turn these
10264 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
10265 warnings and messages}.)
10267 We have not implemented the two-stage strategy for COFF yet. When the
10268 symbol table is stored in COFF format, @code{symbol-file} reads the
10269 symbol table data in full right away. Note that ``stabs-in-COFF''
10270 still does the two-stage strategy, since the debug info is actually
10274 @cindex reading symbols immediately
10275 @cindex symbols, reading immediately
10277 @cindex memory-mapped symbol file
10278 @cindex saving symbol table
10279 @item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10280 @itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10281 You can override the @value{GDBN} two-stage strategy for reading symbol
10282 tables by using the @samp{-readnow} option with any of the commands that
10283 load symbol table information, if you want to be sure @value{GDBN} has the
10284 entire symbol table available.
10286 If memory-mapped files are available on your system through the
10287 @code{mmap} system call, you can use another option, @samp{-mapped}, to
10288 cause @value{GDBN} to write the symbols for your program into a reusable
10289 file. Future @value{GDBN} debugging sessions map in symbol information
10290 from this auxiliary symbol file (if the program has not changed), rather
10291 than spending time reading the symbol table from the executable
10292 program. Using the @samp{-mapped} option has the same effect as
10293 starting @value{GDBN} with the @samp{-mapped} command-line option.
10295 You can use both options together, to make sure the auxiliary symbol
10296 file has all the symbol information for your program.
10298 The auxiliary symbol file for a program called @var{myprog} is called
10299 @samp{@var{myprog}.syms}. Once this file exists (so long as it is newer
10300 than the corresponding executable), @value{GDBN} always attempts to use
10301 it when you debug @var{myprog}; no special options or commands are
10304 The @file{.syms} file is specific to the host machine where you run
10305 @value{GDBN}. It holds an exact image of the internal @value{GDBN}
10306 symbol table. It cannot be shared across multiple host platforms.
10308 @c FIXME: for now no mention of directories, since this seems to be in
10309 @c flux. 13mar1992 status is that in theory GDB would look either in
10310 @c current dir or in same dir as myprog; but issues like competing
10311 @c GDB's, or clutter in system dirs, mean that in practice right now
10312 @c only current dir is used. FFish says maybe a special GDB hierarchy
10313 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
10317 @item core-file @r{[} @var{filename} @r{]}
10319 Specify the whereabouts of a core dump file to be used as the ``contents
10320 of memory''. Traditionally, core files contain only some parts of the
10321 address space of the process that generated them; @value{GDBN} can access the
10322 executable file itself for other parts.
10324 @code{core-file} with no argument specifies that no core file is
10327 Note that the core file is ignored when your program is actually running
10328 under @value{GDBN}. So, if you have been running your program and you
10329 wish to debug a core file instead, you must kill the subprocess in which
10330 the program is running. To do this, use the @code{kill} command
10331 (@pxref{Kill Process, ,Killing the child process}).
10333 @kindex add-symbol-file
10334 @cindex dynamic linking
10335 @item add-symbol-file @var{filename} @var{address}
10336 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10337 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
10338 The @code{add-symbol-file} command reads additional symbol table
10339 information from the file @var{filename}. You would use this command
10340 when @var{filename} has been dynamically loaded (by some other means)
10341 into the program that is running. @var{address} should be the memory
10342 address at which the file has been loaded; @value{GDBN} cannot figure
10343 this out for itself. You can additionally specify an arbitrary number
10344 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
10345 section name and base address for that section. You can specify any
10346 @var{address} as an expression.
10348 The symbol table of the file @var{filename} is added to the symbol table
10349 originally read with the @code{symbol-file} command. You can use the
10350 @code{add-symbol-file} command any number of times; the new symbol data
10351 thus read keeps adding to the old. To discard all old symbol data
10352 instead, use the @code{symbol-file} command without any arguments.
10354 @cindex relocatable object files, reading symbols from
10355 @cindex object files, relocatable, reading symbols from
10356 @cindex reading symbols from relocatable object files
10357 @cindex symbols, reading from relocatable object files
10358 @cindex @file{.o} files, reading symbols from
10359 Although @var{filename} is typically a shared library file, an
10360 executable file, or some other object file which has been fully
10361 relocated for loading into a process, you can also load symbolic
10362 information from relocatable @file{.o} files, as long as:
10366 the file's symbolic information refers only to linker symbols defined in
10367 that file, not to symbols defined by other object files,
10369 every section the file's symbolic information refers to has actually
10370 been loaded into the inferior, as it appears in the file, and
10372 you can determine the address at which every section was loaded, and
10373 provide these to the @code{add-symbol-file} command.
10377 Some embedded operating systems, like Sun Chorus and VxWorks, can load
10378 relocatable files into an already running program; such systems
10379 typically make the requirements above easy to meet. However, it's
10380 important to recognize that many native systems use complex link
10381 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
10382 assembly, for example) that make the requirements difficult to meet. In
10383 general, one cannot assume that using @code{add-symbol-file} to read a
10384 relocatable object file's symbolic information will have the same effect
10385 as linking the relocatable object file into the program in the normal
10388 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
10390 You can use the @samp{-mapped} and @samp{-readnow} options just as with
10391 the @code{symbol-file} command, to change how @value{GDBN} manages the symbol
10392 table information for @var{filename}.
10394 @kindex add-shared-symbol-file
10395 @item add-shared-symbol-file
10396 The @code{add-shared-symbol-file} command can be used only under Harris' CXUX
10397 operating system for the Motorola 88k. @value{GDBN} automatically looks for
10398 shared libraries, however if @value{GDBN} does not find yours, you can run
10399 @code{add-shared-symbol-file}. It takes no arguments.
10403 The @code{section} command changes the base address of section SECTION of
10404 the exec file to ADDR. This can be used if the exec file does not contain
10405 section addresses, (such as in the a.out format), or when the addresses
10406 specified in the file itself are wrong. Each section must be changed
10407 separately. The @code{info files} command, described below, lists all
10408 the sections and their addresses.
10411 @kindex info target
10414 @code{info files} and @code{info target} are synonymous; both print the
10415 current target (@pxref{Targets, ,Specifying a Debugging Target}),
10416 including the names of the executable and core dump files currently in
10417 use by @value{GDBN}, and the files from which symbols were loaded. The
10418 command @code{help target} lists all possible targets rather than
10421 @kindex maint info sections
10422 @item maint info sections
10423 Another command that can give you extra information about program sections
10424 is @code{maint info sections}. In addition to the section information
10425 displayed by @code{info files}, this command displays the flags and file
10426 offset of each section in the executable and core dump files. In addition,
10427 @code{maint info sections} provides the following command options (which
10428 may be arbitrarily combined):
10432 Display sections for all loaded object files, including shared libraries.
10433 @item @var{sections}
10434 Display info only for named @var{sections}.
10435 @item @var{section-flags}
10436 Display info only for sections for which @var{section-flags} are true.
10437 The section flags that @value{GDBN} currently knows about are:
10440 Section will have space allocated in the process when loaded.
10441 Set for all sections except those containing debug information.
10443 Section will be loaded from the file into the child process memory.
10444 Set for pre-initialized code and data, clear for @code{.bss} sections.
10446 Section needs to be relocated before loading.
10448 Section cannot be modified by the child process.
10450 Section contains executable code only.
10452 Section contains data only (no executable code).
10454 Section will reside in ROM.
10456 Section contains data for constructor/destructor lists.
10458 Section is not empty.
10460 An instruction to the linker to not output the section.
10461 @item COFF_SHARED_LIBRARY
10462 A notification to the linker that the section contains
10463 COFF shared library information.
10465 Section contains common symbols.
10468 @kindex set trust-readonly-sections
10469 @item set trust-readonly-sections on
10470 Tell @value{GDBN} that readonly sections in your object file
10471 really are read-only (i.e.@: that their contents will not change).
10472 In that case, @value{GDBN} can fetch values from these sections
10473 out of the object file, rather than from the target program.
10474 For some targets (notably embedded ones), this can be a significant
10475 enhancement to debugging performance.
10477 The default is off.
10479 @item set trust-readonly-sections off
10480 Tell @value{GDBN} not to trust readonly sections. This means that
10481 the contents of the section might change while the program is running,
10482 and must therefore be fetched from the target when needed.
10485 All file-specifying commands allow both absolute and relative file names
10486 as arguments. @value{GDBN} always converts the file name to an absolute file
10487 name and remembers it that way.
10489 @cindex shared libraries
10490 @value{GDBN} supports HP-UX, SunOS, SVr4, Irix 5, and IBM RS/6000 shared
10493 @value{GDBN} automatically loads symbol definitions from shared libraries
10494 when you use the @code{run} command, or when you examine a core file.
10495 (Before you issue the @code{run} command, @value{GDBN} does not understand
10496 references to a function in a shared library, however---unless you are
10497 debugging a core file).
10499 On HP-UX, if the program loads a library explicitly, @value{GDBN}
10500 automatically loads the symbols at the time of the @code{shl_load} call.
10502 @c FIXME: some @value{GDBN} release may permit some refs to undef
10503 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
10504 @c FIXME...lib; check this from time to time when updating manual
10506 There are times, however, when you may wish to not automatically load
10507 symbol definitions from shared libraries, such as when they are
10508 particularly large or there are many of them.
10510 To control the automatic loading of shared library symbols, use the
10514 @kindex set auto-solib-add
10515 @item set auto-solib-add @var{mode}
10516 If @var{mode} is @code{on}, symbols from all shared object libraries
10517 will be loaded automatically when the inferior begins execution, you
10518 attach to an independently started inferior, or when the dynamic linker
10519 informs @value{GDBN} that a new library has been loaded. If @var{mode}
10520 is @code{off}, symbols must be loaded manually, using the
10521 @code{sharedlibrary} command. The default value is @code{on}.
10523 @cindex memory used for symbol tables
10524 If your program uses lots of shared libraries with debug info that
10525 takes large amounts of memory, you can decrease the @value{GDBN}
10526 memory footprint by preventing it from automatically loading the
10527 symbols from shared libraries. To that end, type @kbd{set
10528 auto-solib-add off} before running the inferior, then load each
10529 library whose debug symbols you do need with @kbd{sharedlibrary
10530 @var{regexp}}, where @var{regexp} is a regular expresion that matches
10531 the libraries whose symbols you want to be loaded.
10533 @kindex show auto-solib-add
10534 @item show auto-solib-add
10535 Display the current autoloading mode.
10538 To explicitly load shared library symbols, use the @code{sharedlibrary}
10542 @kindex info sharedlibrary
10545 @itemx info sharedlibrary
10546 Print the names of the shared libraries which are currently loaded.
10548 @kindex sharedlibrary
10550 @item sharedlibrary @var{regex}
10551 @itemx share @var{regex}
10552 Load shared object library symbols for files matching a
10553 Unix regular expression.
10554 As with files loaded automatically, it only loads shared libraries
10555 required by your program for a core file or after typing @code{run}. If
10556 @var{regex} is omitted all shared libraries required by your program are
10560 On some systems, such as HP-UX systems, @value{GDBN} supports
10561 autoloading shared library symbols until a limiting threshold size is
10562 reached. This provides the benefit of allowing autoloading to remain on
10563 by default, but avoids autoloading excessively large shared libraries,
10564 up to a threshold that is initially set, but which you can modify if you
10567 Beyond that threshold, symbols from shared libraries must be explicitly
10568 loaded. To load these symbols, use the command @code{sharedlibrary
10569 @var{filename}}. The base address of the shared library is determined
10570 automatically by @value{GDBN} and need not be specified.
10572 To display or set the threshold, use the commands:
10575 @kindex set auto-solib-limit
10576 @item set auto-solib-limit @var{threshold}
10577 Set the autoloading size threshold, in an integral number of megabytes.
10578 If @var{threshold} is nonzero and shared library autoloading is enabled,
10579 symbols from all shared object libraries will be loaded until the total
10580 size of the loaded shared library symbols exceeds this threshold.
10581 Otherwise, symbols must be loaded manually, using the
10582 @code{sharedlibrary} command. The default threshold is 100 (i.e.@: 100
10585 @kindex show auto-solib-limit
10586 @item show auto-solib-limit
10587 Display the current autoloading size threshold, in megabytes.
10590 Shared libraries are also supported in many cross or remote debugging
10591 configurations. A copy of the target's libraries need to be present on the
10592 host system; they need to be the same as the target libraries, although the
10593 copies on the target can be stripped as long as the copies on the host are
10596 You need to tell @value{GDBN} where the target libraries are, so that it can
10597 load the correct copies---otherwise, it may try to load the host's libraries.
10598 @value{GDBN} has two variables to specify the search directories for target
10602 @kindex set solib-absolute-prefix
10603 @item set solib-absolute-prefix @var{path}
10604 If this variable is set, @var{path} will be used as a prefix for any
10605 absolute shared library paths; many runtime loaders store the absolute
10606 paths to the shared library in the target program's memory. If you use
10607 @samp{solib-absolute-prefix} to find shared libraries, they need to be laid
10608 out in the same way that they are on the target, with e.g.@: a
10609 @file{/usr/lib} hierarchy under @var{path}.
10611 You can set the default value of @samp{solib-absolute-prefix} by using the
10612 configure-time @samp{--with-sysroot} option.
10614 @kindex show solib-absolute-prefix
10615 @item show solib-absolute-prefix
10616 Display the current shared library prefix.
10618 @kindex set solib-search-path
10619 @item set solib-search-path @var{path}
10620 If this variable is set, @var{path} is a colon-separated list of directories
10621 to search for shared libraries. @samp{solib-search-path} is used after
10622 @samp{solib-absolute-prefix} fails to locate the library, or if the path to
10623 the library is relative instead of absolute. If you want to use
10624 @samp{solib-search-path} instead of @samp{solib-absolute-prefix}, be sure to
10625 set @samp{solib-absolute-prefix} to a nonexistant directory to prevent
10626 @value{GDBN} from finding your host's libraries.
10628 @kindex show solib-search-path
10629 @item show solib-search-path
10630 Display the current shared library search path.
10634 @node Separate Debug Files
10635 @section Debugging Information in Separate Files
10636 @cindex separate debugging information files
10637 @cindex debugging information in separate files
10638 @cindex @file{.debug} subdirectories
10639 @cindex debugging information directory, global
10640 @cindex global debugging information directory
10642 @value{GDBN} allows you to put a program's debugging information in a
10643 file separate from the executable itself, in a way that allows
10644 @value{GDBN} to find and load the debugging information automatically.
10645 Since debugging information can be very large --- sometimes larger
10646 than the executable code itself --- some systems distribute debugging
10647 information for their executables in separate files, which users can
10648 install only when they need to debug a problem.
10650 If an executable's debugging information has been extracted to a
10651 separate file, the executable should contain a @dfn{debug link} giving
10652 the name of the debugging information file (with no directory
10653 components), and a checksum of its contents. (The exact form of a
10654 debug link is described below.) If the full name of the directory
10655 containing the executable is @var{execdir}, and the executable has a
10656 debug link that specifies the name @var{debugfile}, then @value{GDBN}
10657 will automatically search for the debugging information file in three
10662 the directory containing the executable file (that is, it will look
10663 for a file named @file{@var{execdir}/@var{debugfile}},
10665 a subdirectory of that directory named @file{.debug} (that is, the
10666 file @file{@var{execdir}/.debug/@var{debugfile}}, and
10668 a subdirectory of the global debug file directory that includes the
10669 executable's full path, and the name from the link (that is, the file
10670 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
10671 @var{globaldebugdir} is the global debug file directory, and
10672 @var{execdir} has been turned into a relative path).
10675 @value{GDBN} checks under each of these names for a debugging
10676 information file whose checksum matches that given in the link, and
10677 reads the debugging information from the first one it finds.
10679 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
10680 which has a link containing the name @file{ls.debug}, and the global
10681 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
10682 for debug information in @file{/usr/bin/ls.debug},
10683 @file{/usr/bin/.debug/ls.debug}, and
10684 @file{/usr/lib/debug/usr/bin/ls.debug}.
10686 You can set the global debugging info directory's name, and view the
10687 name @value{GDBN} is currently using.
10691 @kindex set debug-file-directory
10692 @item set debug-file-directory @var{directory}
10693 Set the directory which @value{GDBN} searches for separate debugging
10694 information files to @var{directory}.
10696 @kindex show debug-file-directory
10697 @item show debug-file-directory
10698 Show the directory @value{GDBN} searches for separate debugging
10703 @cindex @code{.gnu_debuglink} sections
10704 @cindex debug links
10705 A debug link is a special section of the executable file named
10706 @code{.gnu_debuglink}. The section must contain:
10710 A filename, with any leading directory components removed, followed by
10713 zero to three bytes of padding, as needed to reach the next four-byte
10714 boundary within the section, and
10716 a four-byte CRC checksum, stored in the same endianness used for the
10717 executable file itself. The checksum is computed on the debugging
10718 information file's full contents by the function given below, passing
10719 zero as the @var{crc} argument.
10722 Any executable file format can carry a debug link, as long as it can
10723 contain a section named @code{.gnu_debuglink} with the contents
10726 The debugging information file itself should be an ordinary
10727 executable, containing a full set of linker symbols, sections, and
10728 debugging information. The sections of the debugging information file
10729 should have the same names, addresses and sizes as the original file,
10730 but they need not contain any data --- much like a @code{.bss} section
10731 in an ordinary executable.
10733 As of December 2002, there is no standard GNU utility to produce
10734 separated executable / debugging information file pairs. Ulrich
10735 Drepper's @file{elfutils} package, starting with version 0.53,
10736 contains a version of the @code{strip} command such that the command
10737 @kbd{strip foo -f foo.debug} removes the debugging information from
10738 the executable file @file{foo}, places it in the file
10739 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
10741 Since there are many different ways to compute CRC's (different
10742 polynomials, reversals, byte ordering, etc.), the simplest way to
10743 describe the CRC used in @code{.gnu_debuglink} sections is to give the
10744 complete code for a function that computes it:
10746 @kindex gnu_debuglink_crc32
10749 gnu_debuglink_crc32 (unsigned long crc,
10750 unsigned char *buf, size_t len)
10752 static const unsigned long crc32_table[256] =
10754 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
10755 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
10756 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
10757 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
10758 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
10759 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
10760 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
10761 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
10762 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
10763 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
10764 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
10765 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
10766 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
10767 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
10768 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
10769 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
10770 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
10771 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
10772 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
10773 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
10774 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
10775 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
10776 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
10777 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
10778 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
10779 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
10780 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
10781 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
10782 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
10783 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
10784 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
10785 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
10786 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
10787 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
10788 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
10789 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
10790 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
10791 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
10792 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
10793 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
10794 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
10795 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
10796 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
10797 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
10798 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
10799 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
10800 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
10801 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
10802 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
10803 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
10804 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
10807 unsigned char *end;
10809 crc = ~crc & 0xffffffff;
10810 for (end = buf + len; buf < end; ++buf)
10811 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
10812 return ~crc & 0xffffffff;
10817 @node Symbol Errors
10818 @section Errors reading symbol files
10820 While reading a symbol file, @value{GDBN} occasionally encounters problems,
10821 such as symbol types it does not recognize, or known bugs in compiler
10822 output. By default, @value{GDBN} does not notify you of such problems, since
10823 they are relatively common and primarily of interest to people
10824 debugging compilers. If you are interested in seeing information
10825 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
10826 only one message about each such type of problem, no matter how many
10827 times the problem occurs; or you can ask @value{GDBN} to print more messages,
10828 to see how many times the problems occur, with the @code{set
10829 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
10832 The messages currently printed, and their meanings, include:
10835 @item inner block not inside outer block in @var{symbol}
10837 The symbol information shows where symbol scopes begin and end
10838 (such as at the start of a function or a block of statements). This
10839 error indicates that an inner scope block is not fully contained
10840 in its outer scope blocks.
10842 @value{GDBN} circumvents the problem by treating the inner block as if it had
10843 the same scope as the outer block. In the error message, @var{symbol}
10844 may be shown as ``@code{(don't know)}'' if the outer block is not a
10847 @item block at @var{address} out of order
10849 The symbol information for symbol scope blocks should occur in
10850 order of increasing addresses. This error indicates that it does not
10853 @value{GDBN} does not circumvent this problem, and has trouble
10854 locating symbols in the source file whose symbols it is reading. (You
10855 can often determine what source file is affected by specifying
10856 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
10859 @item bad block start address patched
10861 The symbol information for a symbol scope block has a start address
10862 smaller than the address of the preceding source line. This is known
10863 to occur in the SunOS 4.1.1 (and earlier) C compiler.
10865 @value{GDBN} circumvents the problem by treating the symbol scope block as
10866 starting on the previous source line.
10868 @item bad string table offset in symbol @var{n}
10871 Symbol number @var{n} contains a pointer into the string table which is
10872 larger than the size of the string table.
10874 @value{GDBN} circumvents the problem by considering the symbol to have the
10875 name @code{foo}, which may cause other problems if many symbols end up
10878 @item unknown symbol type @code{0x@var{nn}}
10880 The symbol information contains new data types that @value{GDBN} does
10881 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
10882 uncomprehended information, in hexadecimal.
10884 @value{GDBN} circumvents the error by ignoring this symbol information.
10885 This usually allows you to debug your program, though certain symbols
10886 are not accessible. If you encounter such a problem and feel like
10887 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
10888 on @code{complain}, then go up to the function @code{read_dbx_symtab}
10889 and examine @code{*bufp} to see the symbol.
10891 @item stub type has NULL name
10893 @value{GDBN} could not find the full definition for a struct or class.
10895 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
10896 The symbol information for a C@t{++} member function is missing some
10897 information that recent versions of the compiler should have output for
10900 @item info mismatch between compiler and debugger
10902 @value{GDBN} could not parse a type specification output by the compiler.
10907 @chapter Specifying a Debugging Target
10909 @cindex debugging target
10912 A @dfn{target} is the execution environment occupied by your program.
10914 Often, @value{GDBN} runs in the same host environment as your program;
10915 in that case, the debugging target is specified as a side effect when
10916 you use the @code{file} or @code{core} commands. When you need more
10917 flexibility---for example, running @value{GDBN} on a physically separate
10918 host, or controlling a standalone system over a serial port or a
10919 realtime system over a TCP/IP connection---you can use the @code{target}
10920 command to specify one of the target types configured for @value{GDBN}
10921 (@pxref{Target Commands, ,Commands for managing targets}).
10924 * Active Targets:: Active targets
10925 * Target Commands:: Commands for managing targets
10926 * Byte Order:: Choosing target byte order
10927 * Remote:: Remote debugging
10928 * KOD:: Kernel Object Display
10932 @node Active Targets
10933 @section Active targets
10935 @cindex stacking targets
10936 @cindex active targets
10937 @cindex multiple targets
10939 There are three classes of targets: processes, core files, and
10940 executable files. @value{GDBN} can work concurrently on up to three
10941 active targets, one in each class. This allows you to (for example)
10942 start a process and inspect its activity without abandoning your work on
10945 For example, if you execute @samp{gdb a.out}, then the executable file
10946 @code{a.out} is the only active target. If you designate a core file as
10947 well---presumably from a prior run that crashed and coredumped---then
10948 @value{GDBN} has two active targets and uses them in tandem, looking
10949 first in the corefile target, then in the executable file, to satisfy
10950 requests for memory addresses. (Typically, these two classes of target
10951 are complementary, since core files contain only a program's
10952 read-write memory---variables and so on---plus machine status, while
10953 executable files contain only the program text and initialized data.)
10955 When you type @code{run}, your executable file becomes an active process
10956 target as well. When a process target is active, all @value{GDBN}
10957 commands requesting memory addresses refer to that target; addresses in
10958 an active core file or executable file target are obscured while the
10959 process target is active.
10961 Use the @code{core-file} and @code{exec-file} commands to select a new
10962 core file or executable target (@pxref{Files, ,Commands to specify
10963 files}). To specify as a target a process that is already running, use
10964 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
10967 @node Target Commands
10968 @section Commands for managing targets
10971 @item target @var{type} @var{parameters}
10972 Connects the @value{GDBN} host environment to a target machine or
10973 process. A target is typically a protocol for talking to debugging
10974 facilities. You use the argument @var{type} to specify the type or
10975 protocol of the target machine.
10977 Further @var{parameters} are interpreted by the target protocol, but
10978 typically include things like device names or host names to connect
10979 with, process numbers, and baud rates.
10981 The @code{target} command does not repeat if you press @key{RET} again
10982 after executing the command.
10984 @kindex help target
10986 Displays the names of all targets available. To display targets
10987 currently selected, use either @code{info target} or @code{info files}
10988 (@pxref{Files, ,Commands to specify files}).
10990 @item help target @var{name}
10991 Describe a particular target, including any parameters necessary to
10994 @kindex set gnutarget
10995 @item set gnutarget @var{args}
10996 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
10997 knows whether it is reading an @dfn{executable},
10998 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
10999 with the @code{set gnutarget} command. Unlike most @code{target} commands,
11000 with @code{gnutarget} the @code{target} refers to a program, not a machine.
11003 @emph{Warning:} To specify a file format with @code{set gnutarget},
11004 you must know the actual BFD name.
11008 @xref{Files, , Commands to specify files}.
11010 @kindex show gnutarget
11011 @item show gnutarget
11012 Use the @code{show gnutarget} command to display what file format
11013 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
11014 @value{GDBN} will determine the file format for each file automatically,
11015 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
11018 @cindex common targets
11019 Here are some common targets (available, or not, depending on the GDB
11024 @item target exec @var{program}
11025 @cindex executable file target
11026 An executable file. @samp{target exec @var{program}} is the same as
11027 @samp{exec-file @var{program}}.
11029 @item target core @var{filename}
11030 @cindex core dump file target
11031 A core dump file. @samp{target core @var{filename}} is the same as
11032 @samp{core-file @var{filename}}.
11034 @item target remote @var{dev}
11035 @cindex remote target
11036 Remote serial target in GDB-specific protocol. The argument @var{dev}
11037 specifies what serial device to use for the connection (e.g.
11038 @file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote}
11039 supports the @code{load} command. This is only useful if you have
11040 some other way of getting the stub to the target system, and you can put
11041 it somewhere in memory where it won't get clobbered by the download.
11044 @cindex built-in simulator target
11045 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
11053 works; however, you cannot assume that a specific memory map, device
11054 drivers, or even basic I/O is available, although some simulators do
11055 provide these. For info about any processor-specific simulator details,
11056 see the appropriate section in @ref{Embedded Processors, ,Embedded
11061 Some configurations may include these targets as well:
11065 @item target nrom @var{dev}
11066 @cindex NetROM ROM emulator target
11067 NetROM ROM emulator. This target only supports downloading.
11071 Different targets are available on different configurations of @value{GDBN};
11072 your configuration may have more or fewer targets.
11074 Many remote targets require you to download the executable's code
11075 once you've successfully established a connection.
11079 @kindex load @var{filename}
11080 @item load @var{filename}
11081 Depending on what remote debugging facilities are configured into
11082 @value{GDBN}, the @code{load} command may be available. Where it exists, it
11083 is meant to make @var{filename} (an executable) available for debugging
11084 on the remote system---by downloading, or dynamic linking, for example.
11085 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
11086 the @code{add-symbol-file} command.
11088 If your @value{GDBN} does not have a @code{load} command, attempting to
11089 execute it gets the error message ``@code{You can't do that when your
11090 target is @dots{}}''
11092 The file is loaded at whatever address is specified in the executable.
11093 For some object file formats, you can specify the load address when you
11094 link the program; for other formats, like a.out, the object file format
11095 specifies a fixed address.
11096 @c FIXME! This would be a good place for an xref to the GNU linker doc.
11098 @code{load} does not repeat if you press @key{RET} again after using it.
11102 @section Choosing target byte order
11104 @cindex choosing target byte order
11105 @cindex target byte order
11107 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
11108 offer the ability to run either big-endian or little-endian byte
11109 orders. Usually the executable or symbol will include a bit to
11110 designate the endian-ness, and you will not need to worry about
11111 which to use. However, you may still find it useful to adjust
11112 @value{GDBN}'s idea of processor endian-ness manually.
11116 @item set endian big
11117 Instruct @value{GDBN} to assume the target is big-endian.
11119 @item set endian little
11120 Instruct @value{GDBN} to assume the target is little-endian.
11122 @item set endian auto
11123 Instruct @value{GDBN} to use the byte order associated with the
11127 Display @value{GDBN}'s current idea of the target byte order.
11131 Note that these commands merely adjust interpretation of symbolic
11132 data on the host, and that they have absolutely no effect on the
11136 @section Remote debugging
11137 @cindex remote debugging
11139 If you are trying to debug a program running on a machine that cannot run
11140 @value{GDBN} in the usual way, it is often useful to use remote debugging.
11141 For example, you might use remote debugging on an operating system kernel,
11142 or on a small system which does not have a general purpose operating system
11143 powerful enough to run a full-featured debugger.
11145 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
11146 to make this work with particular debugging targets. In addition,
11147 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
11148 but not specific to any particular target system) which you can use if you
11149 write the remote stubs---the code that runs on the remote system to
11150 communicate with @value{GDBN}.
11152 Other remote targets may be available in your
11153 configuration of @value{GDBN}; use @code{help target} to list them.
11156 @section Kernel Object Display
11157 @cindex kernel object display
11160 Some targets support kernel object display. Using this facility,
11161 @value{GDBN} communicates specially with the underlying operating system
11162 and can display information about operating system-level objects such as
11163 mutexes and other synchronization objects. Exactly which objects can be
11164 displayed is determined on a per-OS basis.
11167 Use the @code{set os} command to set the operating system. This tells
11168 @value{GDBN} which kernel object display module to initialize:
11171 (@value{GDBP}) set os cisco
11175 The associated command @code{show os} displays the operating system
11176 set with the @code{set os} command; if no operating system has been
11177 set, @code{show os} will display an empty string @samp{""}.
11179 If @code{set os} succeeds, @value{GDBN} will display some information
11180 about the operating system, and will create a new @code{info} command
11181 which can be used to query the target. The @code{info} command is named
11182 after the operating system:
11186 (@value{GDBP}) info cisco
11187 List of Cisco Kernel Objects
11189 any Any and all objects
11192 Further subcommands can be used to query about particular objects known
11195 There is currently no way to determine whether a given operating
11196 system is supported other than to try setting it with @kbd{set os
11197 @var{name}}, where @var{name} is the name of the operating system you
11201 @node Remote Debugging
11202 @chapter Debugging remote programs
11205 * Connecting:: Connecting to a remote target
11206 * Server:: Using the gdbserver program
11207 * NetWare:: Using the gdbserve.nlm program
11208 * Remote configuration:: Remote configuration
11209 * remote stub:: Implementing a remote stub
11213 @section Connecting to a remote target
11215 On the @value{GDBN} host machine, you will need an unstripped copy of
11216 your program, since @value{GDBN} needs symobl and debugging information.
11217 Start up @value{GDBN} as usual, using the name of the local copy of your
11218 program as the first argument.
11220 @cindex serial line, @code{target remote}
11221 If you're using a serial line, you may want to give @value{GDBN} the
11222 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
11223 before the @code{target} command.
11225 After that, use @code{target remote} to establish communications with
11226 the target machine. Its argument specifies how to communicate---either
11227 via a devicename attached to a direct serial line, or a TCP or UDP port
11228 (possibly to a terminal server which in turn has a serial line to the
11229 target). For example, to use a serial line connected to the device
11230 named @file{/dev/ttyb}:
11233 target remote /dev/ttyb
11236 @cindex TCP port, @code{target remote}
11237 To use a TCP connection, use an argument of the form
11238 @code{@var{host}:@var{port}} or @code{tcp:@var{host}:@var{port}}.
11239 For example, to connect to port 2828 on a
11240 terminal server named @code{manyfarms}:
11243 target remote manyfarms:2828
11246 If your remote target is actually running on the same machine as
11247 your debugger session (e.g.@: a simulator of your target running on
11248 the same host), you can omit the hostname. For example, to connect
11249 to port 1234 on your local machine:
11252 target remote :1234
11256 Note that the colon is still required here.
11258 @cindex UDP port, @code{target remote}
11259 To use a UDP connection, use an argument of the form
11260 @code{udp:@var{host}:@var{port}}. For example, to connect to UDP port 2828
11261 on a terminal server named @code{manyfarms}:
11264 target remote udp:manyfarms:2828
11267 When using a UDP connection for remote debugging, you should keep in mind
11268 that the `U' stands for ``Unreliable''. UDP can silently drop packets on
11269 busy or unreliable networks, which will cause havoc with your debugging
11272 Now you can use all the usual commands to examine and change data and to
11273 step and continue the remote program.
11275 @cindex interrupting remote programs
11276 @cindex remote programs, interrupting
11277 Whenever @value{GDBN} is waiting for the remote program, if you type the
11278 interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
11279 program. This may or may not succeed, depending in part on the hardware
11280 and the serial drivers the remote system uses. If you type the
11281 interrupt character once again, @value{GDBN} displays this prompt:
11284 Interrupted while waiting for the program.
11285 Give up (and stop debugging it)? (y or n)
11288 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
11289 (If you decide you want to try again later, you can use @samp{target
11290 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
11291 goes back to waiting.
11294 @kindex detach (remote)
11296 When you have finished debugging the remote program, you can use the
11297 @code{detach} command to release it from @value{GDBN} control.
11298 Detaching from the target normally resumes its execution, but the results
11299 will depend on your particular remote stub. After the @code{detach}
11300 command, @value{GDBN} is free to connect to another target.
11304 The @code{disconnect} command behaves like @code{detach}, except that
11305 the target is generally not resumed. It will wait for @value{GDBN}
11306 (this instance or another one) to connect and continue debugging. After
11307 the @code{disconnect} command, @value{GDBN} is again free to connect to
11312 @section Using the @code{gdbserver} program
11315 @cindex remote connection without stubs
11316 @code{gdbserver} is a control program for Unix-like systems, which
11317 allows you to connect your program with a remote @value{GDBN} via
11318 @code{target remote}---but without linking in the usual debugging stub.
11320 @code{gdbserver} is not a complete replacement for the debugging stubs,
11321 because it requires essentially the same operating-system facilities
11322 that @value{GDBN} itself does. In fact, a system that can run
11323 @code{gdbserver} to connect to a remote @value{GDBN} could also run
11324 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
11325 because it is a much smaller program than @value{GDBN} itself. It is
11326 also easier to port than all of @value{GDBN}, so you may be able to get
11327 started more quickly on a new system by using @code{gdbserver}.
11328 Finally, if you develop code for real-time systems, you may find that
11329 the tradeoffs involved in real-time operation make it more convenient to
11330 do as much development work as possible on another system, for example
11331 by cross-compiling. You can use @code{gdbserver} to make a similar
11332 choice for debugging.
11334 @value{GDBN} and @code{gdbserver} communicate via either a serial line
11335 or a TCP connection, using the standard @value{GDBN} remote serial
11339 @item On the target machine,
11340 you need to have a copy of the program you want to debug.
11341 @code{gdbserver} does not need your program's symbol table, so you can
11342 strip the program if necessary to save space. @value{GDBN} on the host
11343 system does all the symbol handling.
11345 To use the server, you must tell it how to communicate with @value{GDBN};
11346 the name of your program; and the arguments for your program. The usual
11350 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
11353 @var{comm} is either a device name (to use a serial line) or a TCP
11354 hostname and portnumber. For example, to debug Emacs with the argument
11355 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
11359 target> gdbserver /dev/com1 emacs foo.txt
11362 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
11365 To use a TCP connection instead of a serial line:
11368 target> gdbserver host:2345 emacs foo.txt
11371 The only difference from the previous example is the first argument,
11372 specifying that you are communicating with the host @value{GDBN} via
11373 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
11374 expect a TCP connection from machine @samp{host} to local TCP port 2345.
11375 (Currently, the @samp{host} part is ignored.) You can choose any number
11376 you want for the port number as long as it does not conflict with any
11377 TCP ports already in use on the target system (for example, @code{23} is
11378 reserved for @code{telnet}).@footnote{If you choose a port number that
11379 conflicts with another service, @code{gdbserver} prints an error message
11380 and exits.} You must use the same port number with the host @value{GDBN}
11381 @code{target remote} command.
11383 On some targets, @code{gdbserver} can also attach to running programs.
11384 This is accomplished via the @code{--attach} argument. The syntax is:
11387 target> gdbserver @var{comm} --attach @var{pid}
11390 @var{pid} is the process ID of a currently running process. It isn't necessary
11391 to point @code{gdbserver} at a binary for the running process.
11394 @cindex attach to a program by name
11395 You can debug processes by name instead of process ID if your target has the
11396 @code{pidof} utility:
11399 target> gdbserver @var{comm} --attach `pidof @var{PROGRAM}`
11402 In case more than one copy of @var{PROGRAM} is running, or @var{PROGRAM}
11403 has multiple threads, most versions of @code{pidof} support the
11404 @code{-s} option to only return the first process ID.
11406 @item On the host machine,
11407 connect to your target (@pxref{Connecting,,Connecting to a remote target}).
11408 For TCP connections, you must start up @code{gdbserver} prior to using
11409 the @code{target remote} command. Otherwise you may get an error whose
11410 text depends on the host system, but which usually looks something like
11411 @samp{Connection refused}. You don't need to use the @code{load}
11412 command in @value{GDBN} when using gdbserver, since the program is
11413 already on the target.
11418 @section Using the @code{gdbserve.nlm} program
11420 @kindex gdbserve.nlm
11421 @code{gdbserve.nlm} is a control program for NetWare systems, which
11422 allows you to connect your program with a remote @value{GDBN} via
11423 @code{target remote}.
11425 @value{GDBN} and @code{gdbserve.nlm} communicate via a serial line,
11426 using the standard @value{GDBN} remote serial protocol.
11429 @item On the target machine,
11430 you need to have a copy of the program you want to debug.
11431 @code{gdbserve.nlm} does not need your program's symbol table, so you
11432 can strip the program if necessary to save space. @value{GDBN} on the
11433 host system does all the symbol handling.
11435 To use the server, you must tell it how to communicate with
11436 @value{GDBN}; the name of your program; and the arguments for your
11437 program. The syntax is:
11440 load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ]
11441 [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ]
11444 @var{board} and @var{port} specify the serial line; @var{baud} specifies
11445 the baud rate used by the connection. @var{port} and @var{node} default
11446 to 0, @var{baud} defaults to 9600@dmn{bps}.
11448 For example, to debug Emacs with the argument @samp{foo.txt}and
11449 communicate with @value{GDBN} over serial port number 2 or board 1
11450 using a 19200@dmn{bps} connection:
11453 load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
11457 On the @value{GDBN} host machine, connect to your target (@pxref{Connecting,,
11458 Connecting to a remote target}).
11462 @node Remote configuration
11463 @section Remote configuration
11465 The following configuration options are available when debugging remote
11469 @kindex set remote hardware-watchpoint-limit
11470 @kindex set remote hardware-breakpoint-limit
11471 @anchor{set remote hardware-watchpoint-limit}
11472 @anchor{set remote hardware-breakpoint-limit}
11473 @item set remote hardware-watchpoint-limit @var{limit}
11474 @itemx set remote hardware-breakpoint-limit @var{limit}
11475 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
11476 watchpoints. A limit of -1, the default, is treated as unlimited.
11480 @section Implementing a remote stub
11482 @cindex debugging stub, example
11483 @cindex remote stub, example
11484 @cindex stub example, remote debugging
11485 The stub files provided with @value{GDBN} implement the target side of the
11486 communication protocol, and the @value{GDBN} side is implemented in the
11487 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
11488 these subroutines to communicate, and ignore the details. (If you're
11489 implementing your own stub file, you can still ignore the details: start
11490 with one of the existing stub files. @file{sparc-stub.c} is the best
11491 organized, and therefore the easiest to read.)
11493 @cindex remote serial debugging, overview
11494 To debug a program running on another machine (the debugging
11495 @dfn{target} machine), you must first arrange for all the usual
11496 prerequisites for the program to run by itself. For example, for a C
11501 A startup routine to set up the C runtime environment; these usually
11502 have a name like @file{crt0}. The startup routine may be supplied by
11503 your hardware supplier, or you may have to write your own.
11506 A C subroutine library to support your program's
11507 subroutine calls, notably managing input and output.
11510 A way of getting your program to the other machine---for example, a
11511 download program. These are often supplied by the hardware
11512 manufacturer, but you may have to write your own from hardware
11516 The next step is to arrange for your program to use a serial port to
11517 communicate with the machine where @value{GDBN} is running (the @dfn{host}
11518 machine). In general terms, the scheme looks like this:
11522 @value{GDBN} already understands how to use this protocol; when everything
11523 else is set up, you can simply use the @samp{target remote} command
11524 (@pxref{Targets,,Specifying a Debugging Target}).
11526 @item On the target,
11527 you must link with your program a few special-purpose subroutines that
11528 implement the @value{GDBN} remote serial protocol. The file containing these
11529 subroutines is called a @dfn{debugging stub}.
11531 On certain remote targets, you can use an auxiliary program
11532 @code{gdbserver} instead of linking a stub into your program.
11533 @xref{Server,,Using the @code{gdbserver} program}, for details.
11536 The debugging stub is specific to the architecture of the remote
11537 machine; for example, use @file{sparc-stub.c} to debug programs on
11540 @cindex remote serial stub list
11541 These working remote stubs are distributed with @value{GDBN}:
11546 @cindex @file{i386-stub.c}
11549 For Intel 386 and compatible architectures.
11552 @cindex @file{m68k-stub.c}
11553 @cindex Motorola 680x0
11555 For Motorola 680x0 architectures.
11558 @cindex @file{sh-stub.c}
11561 For Renesas SH architectures.
11564 @cindex @file{sparc-stub.c}
11566 For @sc{sparc} architectures.
11568 @item sparcl-stub.c
11569 @cindex @file{sparcl-stub.c}
11572 For Fujitsu @sc{sparclite} architectures.
11576 The @file{README} file in the @value{GDBN} distribution may list other
11577 recently added stubs.
11580 * Stub Contents:: What the stub can do for you
11581 * Bootstrapping:: What you must do for the stub
11582 * Debug Session:: Putting it all together
11585 @node Stub Contents
11586 @subsection What the stub can do for you
11588 @cindex remote serial stub
11589 The debugging stub for your architecture supplies these three
11593 @item set_debug_traps
11594 @findex set_debug_traps
11595 @cindex remote serial stub, initialization
11596 This routine arranges for @code{handle_exception} to run when your
11597 program stops. You must call this subroutine explicitly near the
11598 beginning of your program.
11600 @item handle_exception
11601 @findex handle_exception
11602 @cindex remote serial stub, main routine
11603 This is the central workhorse, but your program never calls it
11604 explicitly---the setup code arranges for @code{handle_exception} to
11605 run when a trap is triggered.
11607 @code{handle_exception} takes control when your program stops during
11608 execution (for example, on a breakpoint), and mediates communications
11609 with @value{GDBN} on the host machine. This is where the communications
11610 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
11611 representative on the target machine. It begins by sending summary
11612 information on the state of your program, then continues to execute,
11613 retrieving and transmitting any information @value{GDBN} needs, until you
11614 execute a @value{GDBN} command that makes your program resume; at that point,
11615 @code{handle_exception} returns control to your own code on the target
11619 @cindex @code{breakpoint} subroutine, remote
11620 Use this auxiliary subroutine to make your program contain a
11621 breakpoint. Depending on the particular situation, this may be the only
11622 way for @value{GDBN} to get control. For instance, if your target
11623 machine has some sort of interrupt button, you won't need to call this;
11624 pressing the interrupt button transfers control to
11625 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
11626 simply receiving characters on the serial port may also trigger a trap;
11627 again, in that situation, you don't need to call @code{breakpoint} from
11628 your own program---simply running @samp{target remote} from the host
11629 @value{GDBN} session gets control.
11631 Call @code{breakpoint} if none of these is true, or if you simply want
11632 to make certain your program stops at a predetermined point for the
11633 start of your debugging session.
11636 @node Bootstrapping
11637 @subsection What you must do for the stub
11639 @cindex remote stub, support routines
11640 The debugging stubs that come with @value{GDBN} are set up for a particular
11641 chip architecture, but they have no information about the rest of your
11642 debugging target machine.
11644 First of all you need to tell the stub how to communicate with the
11648 @item int getDebugChar()
11649 @findex getDebugChar
11650 Write this subroutine to read a single character from the serial port.
11651 It may be identical to @code{getchar} for your target system; a
11652 different name is used to allow you to distinguish the two if you wish.
11654 @item void putDebugChar(int)
11655 @findex putDebugChar
11656 Write this subroutine to write a single character to the serial port.
11657 It may be identical to @code{putchar} for your target system; a
11658 different name is used to allow you to distinguish the two if you wish.
11661 @cindex control C, and remote debugging
11662 @cindex interrupting remote targets
11663 If you want @value{GDBN} to be able to stop your program while it is
11664 running, you need to use an interrupt-driven serial driver, and arrange
11665 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
11666 character). That is the character which @value{GDBN} uses to tell the
11667 remote system to stop.
11669 Getting the debugging target to return the proper status to @value{GDBN}
11670 probably requires changes to the standard stub; one quick and dirty way
11671 is to just execute a breakpoint instruction (the ``dirty'' part is that
11672 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
11674 Other routines you need to supply are:
11677 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
11678 @findex exceptionHandler
11679 Write this function to install @var{exception_address} in the exception
11680 handling tables. You need to do this because the stub does not have any
11681 way of knowing what the exception handling tables on your target system
11682 are like (for example, the processor's table might be in @sc{rom},
11683 containing entries which point to a table in @sc{ram}).
11684 @var{exception_number} is the exception number which should be changed;
11685 its meaning is architecture-dependent (for example, different numbers
11686 might represent divide by zero, misaligned access, etc). When this
11687 exception occurs, control should be transferred directly to
11688 @var{exception_address}, and the processor state (stack, registers,
11689 and so on) should be just as it is when a processor exception occurs. So if
11690 you want to use a jump instruction to reach @var{exception_address}, it
11691 should be a simple jump, not a jump to subroutine.
11693 For the 386, @var{exception_address} should be installed as an interrupt
11694 gate so that interrupts are masked while the handler runs. The gate
11695 should be at privilege level 0 (the most privileged level). The
11696 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
11697 help from @code{exceptionHandler}.
11699 @item void flush_i_cache()
11700 @findex flush_i_cache
11701 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
11702 instruction cache, if any, on your target machine. If there is no
11703 instruction cache, this subroutine may be a no-op.
11705 On target machines that have instruction caches, @value{GDBN} requires this
11706 function to make certain that the state of your program is stable.
11710 You must also make sure this library routine is available:
11713 @item void *memset(void *, int, int)
11715 This is the standard library function @code{memset} that sets an area of
11716 memory to a known value. If you have one of the free versions of
11717 @code{libc.a}, @code{memset} can be found there; otherwise, you must
11718 either obtain it from your hardware manufacturer, or write your own.
11721 If you do not use the GNU C compiler, you may need other standard
11722 library subroutines as well; this varies from one stub to another,
11723 but in general the stubs are likely to use any of the common library
11724 subroutines which @code{@value{GCC}} generates as inline code.
11727 @node Debug Session
11728 @subsection Putting it all together
11730 @cindex remote serial debugging summary
11731 In summary, when your program is ready to debug, you must follow these
11736 Make sure you have defined the supporting low-level routines
11737 (@pxref{Bootstrapping,,What you must do for the stub}):
11739 @code{getDebugChar}, @code{putDebugChar},
11740 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
11744 Insert these lines near the top of your program:
11752 For the 680x0 stub only, you need to provide a variable called
11753 @code{exceptionHook}. Normally you just use:
11756 void (*exceptionHook)() = 0;
11760 but if before calling @code{set_debug_traps}, you set it to point to a
11761 function in your program, that function is called when
11762 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
11763 error). The function indicated by @code{exceptionHook} is called with
11764 one parameter: an @code{int} which is the exception number.
11767 Compile and link together: your program, the @value{GDBN} debugging stub for
11768 your target architecture, and the supporting subroutines.
11771 Make sure you have a serial connection between your target machine and
11772 the @value{GDBN} host, and identify the serial port on the host.
11775 @c The "remote" target now provides a `load' command, so we should
11776 @c document that. FIXME.
11777 Download your program to your target machine (or get it there by
11778 whatever means the manufacturer provides), and start it.
11781 Start @value{GDBN} on the host, and connect to the target
11782 (@pxref{Connecting,,Connecting to a remote target}).
11786 @node Configurations
11787 @chapter Configuration-Specific Information
11789 While nearly all @value{GDBN} commands are available for all native and
11790 cross versions of the debugger, there are some exceptions. This chapter
11791 describes things that are only available in certain configurations.
11793 There are three major categories of configurations: native
11794 configurations, where the host and target are the same, embedded
11795 operating system configurations, which are usually the same for several
11796 different processor architectures, and bare embedded processors, which
11797 are quite different from each other.
11802 * Embedded Processors::
11809 This section describes details specific to particular native
11814 * BSD libkvm Interface:: Debugging BSD kernel memory images
11815 * SVR4 Process Information:: SVR4 process information
11816 * DJGPP Native:: Features specific to the DJGPP port
11817 * Cygwin Native:: Features specific to the Cygwin port
11823 On HP-UX systems, if you refer to a function or variable name that
11824 begins with a dollar sign, @value{GDBN} searches for a user or system
11825 name first, before it searches for a convenience variable.
11827 @node BSD libkvm Interface
11828 @subsection BSD libkvm Interface
11831 @cindex kernel memory image
11832 @cindex kernel crash dump
11834 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
11835 interface that provides a uniform interface for accessing kernel virtual
11836 memory images, including live systems and crash dumps. @value{GDBN}
11837 uses this interface to allow you to debug live kernels and kernel crash
11838 dumps on many native BSD configurations. This is implemented as a
11839 special @code{kvm} debugging target. For debugging a live system, load
11840 the currently running kernel into @value{GDBN} and connect to the
11844 (@value{GDBP}) @b{target kvm}
11847 For debugging crash dumps, provide the file name of the crash dump as an
11851 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
11854 Once connected to the @code{kvm} target, the following commands are
11860 Set current context from pcb address.
11863 Set current context from proc address. This command isn't available on
11864 modern FreeBSD systems.
11867 @node SVR4 Process Information
11868 @subsection SVR4 process information
11870 @cindex examine process image
11871 @cindex process info via @file{/proc}
11873 Many versions of SVR4 and compatible systems provide a facility called
11874 @samp{/proc} that can be used to examine the image of a running
11875 process using file-system subroutines. If @value{GDBN} is configured
11876 for an operating system with this facility, the command @code{info
11877 proc} is available to report information about the process running
11878 your program, or about any process running on your system. @code{info
11879 proc} works only on SVR4 systems that include the @code{procfs} code.
11880 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
11881 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
11887 @itemx info proc @var{process-id}
11888 Summarize available information about any running process. If a
11889 process ID is specified by @var{process-id}, display information about
11890 that process; otherwise display information about the program being
11891 debugged. The summary includes the debugged process ID, the command
11892 line used to invoke it, its current working directory, and its
11893 executable file's absolute file name.
11895 On some systems, @var{process-id} can be of the form
11896 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
11897 within a process. If the optional @var{pid} part is missing, it means
11898 a thread from the process being debugged (the leading @samp{/} still
11899 needs to be present, or else @value{GDBN} will interpret the number as
11900 a process ID rather than a thread ID).
11902 @item info proc mappings
11903 @cindex memory address space mappings
11904 Report the memory address space ranges accessible in the program, with
11905 information on whether the process has read, write, or execute access
11906 rights to each range. On @sc{gnu}/Linux systems, each memory range
11907 includes the object file which is mapped to that range, instead of the
11908 memory access rights to that range.
11910 @item info proc stat
11911 @itemx info proc status
11912 @cindex process detailed status information
11913 These subcommands are specific to @sc{gnu}/Linux systems. They show
11914 the process-related information, including the user ID and group ID;
11915 how many threads are there in the process; its virtual memory usage;
11916 the signals that are pending, blocked, and ignored; its TTY; its
11917 consumption of system and user time; its stack size; its @samp{nice}
11918 value; etc. For more information, see the @samp{proc(5)} man page
11919 (type @kbd{man 5 proc} from your shell prompt).
11921 @item info proc all
11922 Show all the information about the process described under all of the
11923 above @code{info proc} subcommands.
11926 @comment These sub-options of 'info proc' were not included when
11927 @comment procfs.c was re-written. Keep their descriptions around
11928 @comment against the day when someone finds the time to put them back in.
11929 @kindex info proc times
11930 @item info proc times
11931 Starting time, user CPU time, and system CPU time for your program and
11934 @kindex info proc id
11936 Report on the process IDs related to your program: its own process ID,
11937 the ID of its parent, the process group ID, and the session ID.
11942 @subsection Features for Debugging @sc{djgpp} Programs
11943 @cindex @sc{djgpp} debugging
11944 @cindex native @sc{djgpp} debugging
11945 @cindex MS-DOS-specific commands
11947 @sc{djgpp} is the port of @sc{gnu} development tools to MS-DOS and
11948 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
11949 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
11950 top of real-mode DOS systems and their emulations.
11952 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
11953 defines a few commands specific to the @sc{djgpp} port. This
11954 subsection describes those commands.
11959 This is a prefix of @sc{djgpp}-specific commands which print
11960 information about the target system and important OS structures.
11963 @cindex MS-DOS system info
11964 @cindex free memory information (MS-DOS)
11965 @item info dos sysinfo
11966 This command displays assorted information about the underlying
11967 platform: the CPU type and features, the OS version and flavor, the
11968 DPMI version, and the available conventional and DPMI memory.
11973 @cindex segment descriptor tables
11974 @cindex descriptor tables display
11976 @itemx info dos ldt
11977 @itemx info dos idt
11978 These 3 commands display entries from, respectively, Global, Local,
11979 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
11980 tables are data structures which store a descriptor for each segment
11981 that is currently in use. The segment's selector is an index into a
11982 descriptor table; the table entry for that index holds the
11983 descriptor's base address and limit, and its attributes and access
11986 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
11987 segment (used for both data and the stack), and a DOS segment (which
11988 allows access to DOS/BIOS data structures and absolute addresses in
11989 conventional memory). However, the DPMI host will usually define
11990 additional segments in order to support the DPMI environment.
11992 @cindex garbled pointers
11993 These commands allow to display entries from the descriptor tables.
11994 Without an argument, all entries from the specified table are
11995 displayed. An argument, which should be an integer expression, means
11996 display a single entry whose index is given by the argument. For
11997 example, here's a convenient way to display information about the
11998 debugged program's data segment:
12001 @exdent @code{(@value{GDBP}) info dos ldt $ds}
12002 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
12006 This comes in handy when you want to see whether a pointer is outside
12007 the data segment's limit (i.e.@: @dfn{garbled}).
12009 @cindex page tables display (MS-DOS)
12011 @itemx info dos pte
12012 These two commands display entries from, respectively, the Page
12013 Directory and the Page Tables. Page Directories and Page Tables are
12014 data structures which control how virtual memory addresses are mapped
12015 into physical addresses. A Page Table includes an entry for every
12016 page of memory that is mapped into the program's address space; there
12017 may be several Page Tables, each one holding up to 4096 entries. A
12018 Page Directory has up to 4096 entries, one each for every Page Table
12019 that is currently in use.
12021 Without an argument, @kbd{info dos pde} displays the entire Page
12022 Directory, and @kbd{info dos pte} displays all the entries in all of
12023 the Page Tables. An argument, an integer expression, given to the
12024 @kbd{info dos pde} command means display only that entry from the Page
12025 Directory table. An argument given to the @kbd{info dos pte} command
12026 means display entries from a single Page Table, the one pointed to by
12027 the specified entry in the Page Directory.
12029 @cindex direct memory access (DMA) on MS-DOS
12030 These commands are useful when your program uses @dfn{DMA} (Direct
12031 Memory Access), which needs physical addresses to program the DMA
12034 These commands are supported only with some DPMI servers.
12036 @cindex physical address from linear address
12037 @item info dos address-pte @var{addr}
12038 This command displays the Page Table entry for a specified linear
12039 address. The argument linear address @var{addr} should already have the
12040 appropriate segment's base address added to it, because this command
12041 accepts addresses which may belong to @emph{any} segment. For
12042 example, here's how to display the Page Table entry for the page where
12043 the variable @code{i} is stored:
12046 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
12047 @exdent @code{Page Table entry for address 0x11a00d30:}
12048 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
12052 This says that @code{i} is stored at offset @code{0xd30} from the page
12053 whose physical base address is @code{0x02698000}, and prints all the
12054 attributes of that page.
12056 Note that you must cast the addresses of variables to a @code{char *},
12057 since otherwise the value of @code{__djgpp_base_address}, the base
12058 address of all variables and functions in a @sc{djgpp} program, will
12059 be added using the rules of C pointer arithmetics: if @code{i} is
12060 declared an @code{int}, @value{GDBN} will add 4 times the value of
12061 @code{__djgpp_base_address} to the address of @code{i}.
12063 Here's another example, it displays the Page Table entry for the
12067 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
12068 @exdent @code{Page Table entry for address 0x29110:}
12069 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
12073 (The @code{+ 3} offset is because the transfer buffer's address is the
12074 3rd member of the @code{_go32_info_block} structure.) The output of
12075 this command clearly shows that addresses in conventional memory are
12076 mapped 1:1, i.e.@: the physical and linear addresses are identical.
12078 This command is supported only with some DPMI servers.
12081 @node Cygwin Native
12082 @subsection Features for Debugging MS Windows PE executables
12083 @cindex MS Windows debugging
12084 @cindex native Cygwin debugging
12085 @cindex Cygwin-specific commands
12087 @value{GDBN} supports native debugging of MS Windows programs, including
12088 DLLs with and without symbolic debugging information. There are various
12089 additional Cygwin-specific commands, described in this subsection. The
12090 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
12091 that have no debugging symbols.
12097 This is a prefix of MS Windows specific commands which print
12098 information about the target system and important OS structures.
12100 @item info w32 selector
12101 This command displays information returned by
12102 the Win32 API @code{GetThreadSelectorEntry} function.
12103 It takes an optional argument that is evaluated to
12104 a long value to give the information about this given selector.
12105 Without argument, this command displays information
12106 about the the six segment registers.
12110 This is a Cygwin specific alias of info shared.
12112 @kindex dll-symbols
12114 This command loads symbols from a dll similarly to
12115 add-sym command but without the need to specify a base address.
12117 @kindex set new-console
12118 @item set new-console @var{mode}
12119 If @var{mode} is @code{on} the debuggee will
12120 be started in a new console on next start.
12121 If @var{mode} is @code{off}i, the debuggee will
12122 be started in the same console as the debugger.
12124 @kindex show new-console
12125 @item show new-console
12126 Displays whether a new console is used
12127 when the debuggee is started.
12129 @kindex set new-group
12130 @item set new-group @var{mode}
12131 This boolean value controls whether the debuggee should
12132 start a new group or stay in the same group as the debugger.
12133 This affects the way the Windows OS handles
12136 @kindex show new-group
12137 @item show new-group
12138 Displays current value of new-group boolean.
12140 @kindex set debugevents
12141 @item set debugevents
12142 This boolean value adds debug output concerning events seen by the debugger.
12144 @kindex set debugexec
12145 @item set debugexec
12146 This boolean value adds debug output concerning execute events
12147 seen by the debugger.
12149 @kindex set debugexceptions
12150 @item set debugexceptions
12151 This boolean value adds debug ouptut concerning exception events
12152 seen by the debugger.
12154 @kindex set debugmemory
12155 @item set debugmemory
12156 This boolean value adds debug ouptut concerning memory events
12157 seen by the debugger.
12161 This boolean values specifies whether the debuggee is called
12162 via a shell or directly (default value is on).
12166 Displays if the debuggee will be started with a shell.
12171 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
12174 @node Non-debug DLL symbols
12175 @subsubsection Support for DLLs without debugging symbols
12176 @cindex DLLs with no debugging symbols
12177 @cindex Minimal symbols and DLLs
12179 Very often on windows, some of the DLLs that your program relies on do
12180 not include symbolic debugging information (for example,
12181 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
12182 symbols in a DLL, it relies on the minimal amount of symbolic
12183 information contained in the DLL's export table. This subsubsection
12184 describes working with such symbols, known internally to @value{GDBN} as
12185 ``minimal symbols''.
12187 Note that before the debugged program has started execution, no DLLs
12188 will have been loaded. The easiest way around this problem is simply to
12189 start the program --- either by setting a breakpoint or letting the
12190 program run once to completion. It is also possible to force
12191 @value{GDBN} to load a particular DLL before starting the executable ---
12192 see the shared library information in @pxref{Files} or the
12193 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
12194 explicitly loading symbols from a DLL with no debugging information will
12195 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
12196 which may adversely affect symbol lookup performance.
12198 @subsubsection DLL name prefixes
12200 In keeping with the naming conventions used by the Microsoft debugging
12201 tools, DLL export symbols are made available with a prefix based on the
12202 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
12203 also entered into the symbol table, so @code{CreateFileA} is often
12204 sufficient. In some cases there will be name clashes within a program
12205 (particularly if the executable itself includes full debugging symbols)
12206 necessitating the use of the fully qualified name when referring to the
12207 contents of the DLL. Use single-quotes around the name to avoid the
12208 exclamation mark (``!'') being interpreted as a language operator.
12210 Note that the internal name of the DLL may be all upper-case, even
12211 though the file name of the DLL is lower-case, or vice-versa. Since
12212 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
12213 some confusion. If in doubt, try the @code{info functions} and
12214 @code{info variables} commands or even @code{maint print msymbols} (see
12215 @pxref{Symbols}). Here's an example:
12218 (@value{GDBP}) info function CreateFileA
12219 All functions matching regular expression "CreateFileA":
12221 Non-debugging symbols:
12222 0x77e885f4 CreateFileA
12223 0x77e885f4 KERNEL32!CreateFileA
12227 (@value{GDBP}) info function !
12228 All functions matching regular expression "!":
12230 Non-debugging symbols:
12231 0x6100114c cygwin1!__assert
12232 0x61004034 cygwin1!_dll_crt0@@0
12233 0x61004240 cygwin1!dll_crt0(per_process *)
12237 @subsubsection Working with minimal symbols
12239 Symbols extracted from a DLL's export table do not contain very much
12240 type information. All that @value{GDBN} can do is guess whether a symbol
12241 refers to a function or variable depending on the linker section that
12242 contains the symbol. Also note that the actual contents of the memory
12243 contained in a DLL are not available unless the program is running. This
12244 means that you cannot examine the contents of a variable or disassemble
12245 a function within a DLL without a running program.
12247 Variables are generally treated as pointers and dereferenced
12248 automatically. For this reason, it is often necessary to prefix a
12249 variable name with the address-of operator (``&'') and provide explicit
12250 type information in the command. Here's an example of the type of
12254 (@value{GDBP}) print 'cygwin1!__argv'
12259 (@value{GDBP}) x 'cygwin1!__argv'
12260 0x10021610: "\230y\""
12263 And two possible solutions:
12266 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
12267 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
12271 (@value{GDBP}) x/2x &'cygwin1!__argv'
12272 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
12273 (@value{GDBP}) x/x 0x10021608
12274 0x10021608: 0x0022fd98
12275 (@value{GDBP}) x/s 0x0022fd98
12276 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
12279 Setting a break point within a DLL is possible even before the program
12280 starts execution. However, under these circumstances, @value{GDBN} can't
12281 examine the initial instructions of the function in order to skip the
12282 function's frame set-up code. You can work around this by using ``*&''
12283 to set the breakpoint at a raw memory address:
12286 (@value{GDBP}) break *&'python22!PyOS_Readline'
12287 Breakpoint 1 at 0x1e04eff0
12290 The author of these extensions is not entirely convinced that setting a
12291 break point within a shared DLL like @file{kernel32.dll} is completely
12295 @section Embedded Operating Systems
12297 This section describes configurations involving the debugging of
12298 embedded operating systems that are available for several different
12302 * VxWorks:: Using @value{GDBN} with VxWorks
12305 @value{GDBN} includes the ability to debug programs running on
12306 various real-time operating systems.
12309 @subsection Using @value{GDBN} with VxWorks
12315 @kindex target vxworks
12316 @item target vxworks @var{machinename}
12317 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
12318 is the target system's machine name or IP address.
12322 On VxWorks, @code{load} links @var{filename} dynamically on the
12323 current target system as well as adding its symbols in @value{GDBN}.
12325 @value{GDBN} enables developers to spawn and debug tasks running on networked
12326 VxWorks targets from a Unix host. Already-running tasks spawned from
12327 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
12328 both the Unix host and on the VxWorks target. The program
12329 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
12330 installed with the name @code{vxgdb}, to distinguish it from a
12331 @value{GDBN} for debugging programs on the host itself.)
12334 @item VxWorks-timeout @var{args}
12335 @kindex vxworks-timeout
12336 All VxWorks-based targets now support the option @code{vxworks-timeout}.
12337 This option is set by the user, and @var{args} represents the number of
12338 seconds @value{GDBN} waits for responses to rpc's. You might use this if
12339 your VxWorks target is a slow software simulator or is on the far side
12340 of a thin network line.
12343 The following information on connecting to VxWorks was current when
12344 this manual was produced; newer releases of VxWorks may use revised
12347 @findex INCLUDE_RDB
12348 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
12349 to include the remote debugging interface routines in the VxWorks
12350 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
12351 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
12352 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
12353 source debugging task @code{tRdbTask} when VxWorks is booted. For more
12354 information on configuring and remaking VxWorks, see the manufacturer's
12356 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
12358 Once you have included @file{rdb.a} in your VxWorks system image and set
12359 your Unix execution search path to find @value{GDBN}, you are ready to
12360 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
12361 @code{vxgdb}, depending on your installation).
12363 @value{GDBN} comes up showing the prompt:
12370 * VxWorks Connection:: Connecting to VxWorks
12371 * VxWorks Download:: VxWorks download
12372 * VxWorks Attach:: Running tasks
12375 @node VxWorks Connection
12376 @subsubsection Connecting to VxWorks
12378 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
12379 network. To connect to a target whose host name is ``@code{tt}'', type:
12382 (vxgdb) target vxworks tt
12386 @value{GDBN} displays messages like these:
12389 Attaching remote machine across net...
12394 @value{GDBN} then attempts to read the symbol tables of any object modules
12395 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
12396 these files by searching the directories listed in the command search
12397 path (@pxref{Environment, ,Your program's environment}); if it fails
12398 to find an object file, it displays a message such as:
12401 prog.o: No such file or directory.
12404 When this happens, add the appropriate directory to the search path with
12405 the @value{GDBN} command @code{path}, and execute the @code{target}
12408 @node VxWorks Download
12409 @subsubsection VxWorks download
12411 @cindex download to VxWorks
12412 If you have connected to the VxWorks target and you want to debug an
12413 object that has not yet been loaded, you can use the @value{GDBN}
12414 @code{load} command to download a file from Unix to VxWorks
12415 incrementally. The object file given as an argument to the @code{load}
12416 command is actually opened twice: first by the VxWorks target in order
12417 to download the code, then by @value{GDBN} in order to read the symbol
12418 table. This can lead to problems if the current working directories on
12419 the two systems differ. If both systems have NFS mounted the same
12420 filesystems, you can avoid these problems by using absolute paths.
12421 Otherwise, it is simplest to set the working directory on both systems
12422 to the directory in which the object file resides, and then to reference
12423 the file by its name, without any path. For instance, a program
12424 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
12425 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
12426 program, type this on VxWorks:
12429 -> cd "@var{vxpath}/vw/demo/rdb"
12433 Then, in @value{GDBN}, type:
12436 (vxgdb) cd @var{hostpath}/vw/demo/rdb
12437 (vxgdb) load prog.o
12440 @value{GDBN} displays a response similar to this:
12443 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
12446 You can also use the @code{load} command to reload an object module
12447 after editing and recompiling the corresponding source file. Note that
12448 this makes @value{GDBN} delete all currently-defined breakpoints,
12449 auto-displays, and convenience variables, and to clear the value
12450 history. (This is necessary in order to preserve the integrity of
12451 debugger's data structures that reference the target system's symbol
12454 @node VxWorks Attach
12455 @subsubsection Running tasks
12457 @cindex running VxWorks tasks
12458 You can also attach to an existing task using the @code{attach} command as
12462 (vxgdb) attach @var{task}
12466 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
12467 or suspended when you attach to it. Running tasks are suspended at
12468 the time of attachment.
12470 @node Embedded Processors
12471 @section Embedded Processors
12473 This section goes into details specific to particular embedded
12479 * H8/300:: Renesas H8/300
12480 * H8/500:: Renesas H8/500
12481 * M32R/D:: Renesas M32R/D
12482 * M68K:: Motorola M68K
12483 * MIPS Embedded:: MIPS Embedded
12484 * OpenRISC 1000:: OpenRisc 1000
12485 * PA:: HP PA Embedded
12488 * Sparclet:: Tsqware Sparclet
12489 * Sparclite:: Fujitsu Sparclite
12490 * ST2000:: Tandem ST2000
12491 * Z8000:: Zilog Z8000
12500 @item target rdi @var{dev}
12501 ARM Angel monitor, via RDI library interface to ADP protocol. You may
12502 use this target to communicate with both boards running the Angel
12503 monitor, or with the EmbeddedICE JTAG debug device.
12506 @item target rdp @var{dev}
12512 @subsection Renesas H8/300
12516 @kindex target hms@r{, with H8/300}
12517 @item target hms @var{dev}
12518 A Renesas SH, H8/300, or H8/500 board, attached via serial line to your host.
12519 Use special commands @code{device} and @code{speed} to control the serial
12520 line and the communications speed used.
12522 @kindex target e7000@r{, with H8/300}
12523 @item target e7000 @var{dev}
12524 E7000 emulator for Renesas H8 and SH.
12526 @kindex target sh3@r{, with H8/300}
12527 @kindex target sh3e@r{, with H8/300}
12528 @item target sh3 @var{dev}
12529 @itemx target sh3e @var{dev}
12530 Renesas SH-3 and SH-3E target systems.
12534 @cindex download to H8/300 or H8/500
12535 @cindex H8/300 or H8/500 download
12536 @cindex download to Renesas SH
12537 @cindex Renesas SH download
12538 When you select remote debugging to a Renesas SH, H8/300, or H8/500
12539 board, the @code{load} command downloads your program to the Renesas
12540 board and also opens it as the current executable target for
12541 @value{GDBN} on your host (like the @code{file} command).
12543 @value{GDBN} needs to know these things to talk to your
12544 Renesas SH, H8/300, or H8/500:
12548 that you want to use @samp{target hms}, the remote debugging interface
12549 for Renesas microprocessors, or @samp{target e7000}, the in-circuit
12550 emulator for the Renesas SH and the Renesas 300H. (@samp{target hms} is
12551 the default when @value{GDBN} is configured specifically for the Renesas SH,
12552 H8/300, or H8/500.)
12555 what serial device connects your host to your Renesas board (the first
12556 serial device available on your host is the default).
12559 what speed to use over the serial device.
12563 * Renesas Boards:: Connecting to Renesas boards.
12564 * Renesas ICE:: Using the E7000 In-Circuit Emulator.
12565 * Renesas Special:: Special @value{GDBN} commands for Renesas micros.
12568 @node Renesas Boards
12569 @subsubsection Connecting to Renesas boards
12571 @c only for Unix hosts
12573 @cindex serial device, Renesas micros
12574 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
12575 need to explicitly set the serial device. The default @var{port} is the
12576 first available port on your host. This is only necessary on Unix
12577 hosts, where it is typically something like @file{/dev/ttya}.
12580 @cindex serial line speed, Renesas micros
12581 @code{@value{GDBN}} has another special command to set the communications
12582 speed: @samp{speed @var{bps}}. This command also is only used from Unix
12583 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
12584 the DOS @code{mode} command (for instance,
12585 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
12587 The @samp{device} and @samp{speed} commands are available only when you
12588 use a Unix host to debug your Renesas microprocessor programs. If you
12590 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
12591 called @code{asynctsr} to communicate with the development board
12592 through a PC serial port. You must also use the DOS @code{mode} command
12593 to set up the serial port on the DOS side.
12595 The following sample session illustrates the steps needed to start a
12596 program under @value{GDBN} control on an H8/300. The example uses a
12597 sample H8/300 program called @file{t.x}. The procedure is the same for
12598 the Renesas SH and the H8/500.
12600 First hook up your development board. In this example, we use a
12601 board attached to serial port @code{COM2}; if you use a different serial
12602 port, substitute its name in the argument of the @code{mode} command.
12603 When you call @code{asynctsr}, the auxiliary comms program used by the
12604 debugger, you give it just the numeric part of the serial port's name;
12605 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
12609 C:\H8300\TEST> asynctsr 2
12610 C:\H8300\TEST> mode com2:9600,n,8,1,p
12612 Resident portion of MODE loaded
12614 COM2: 9600, n, 8, 1, p
12619 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
12620 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
12621 disable it, or even boot without it, to use @code{asynctsr} to control
12622 your development board.
12625 @kindex target hms@r{, and serial protocol}
12626 Now that serial communications are set up, and the development board is
12627 connected, you can start up @value{GDBN}. Call @code{@value{GDBP}} with
12628 the name of your program as the argument. @code{@value{GDBN}} prompts
12629 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
12630 commands to begin your debugging session: @samp{target hms} to specify
12631 cross-debugging to the Renesas board, and the @code{load} command to
12632 download your program to the board. @code{load} displays the names of
12633 the program's sections, and a @samp{*} for each 2K of data downloaded.
12634 (If you want to refresh @value{GDBN} data on symbols or on the
12635 executable file without downloading, use the @value{GDBN} commands
12636 @code{file} or @code{symbol-file}. These commands, and @code{load}
12637 itself, are described in @ref{Files,,Commands to specify files}.)
12640 (eg-C:\H8300\TEST) @value{GDBP} t.x
12641 @value{GDBN} is free software and you are welcome to distribute copies
12642 of it under certain conditions; type "show copying" to see
12644 There is absolutely no warranty for @value{GDBN}; type "show warranty"
12646 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
12647 (@value{GDBP}) target hms
12648 Connected to remote H8/300 HMS system.
12649 (@value{GDBP}) load t.x
12650 .text : 0x8000 .. 0xabde ***********
12651 .data : 0xabde .. 0xad30 *
12652 .stack : 0xf000 .. 0xf014 *
12655 At this point, you're ready to run or debug your program. From here on,
12656 you can use all the usual @value{GDBN} commands. The @code{break} command
12657 sets breakpoints; the @code{run} command starts your program;
12658 @code{print} or @code{x} display data; the @code{continue} command
12659 resumes execution after stopping at a breakpoint. You can use the
12660 @code{help} command at any time to find out more about @value{GDBN} commands.
12662 Remember, however, that @emph{operating system} facilities aren't
12663 available on your development board; for example, if your program hangs,
12664 you can't send an interrupt---but you can press the @sc{reset} switch!
12666 Use the @sc{reset} button on the development board
12669 to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
12670 no way to pass an interrupt signal to the development board); and
12673 to return to the @value{GDBN} command prompt after your program finishes
12674 normally. The communications protocol provides no other way for @value{GDBN}
12675 to detect program completion.
12678 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
12679 development board as a ``normal exit'' of your program.
12682 @subsubsection Using the E7000 in-circuit emulator
12684 @kindex target e7000@r{, with Renesas ICE}
12685 You can use the E7000 in-circuit emulator to develop code for either the
12686 Renesas SH or the H8/300H. Use one of these forms of the @samp{target
12687 e7000} command to connect @value{GDBN} to your E7000:
12690 @item target e7000 @var{port} @var{speed}
12691 Use this form if your E7000 is connected to a serial port. The
12692 @var{port} argument identifies what serial port to use (for example,
12693 @samp{com2}). The third argument is the line speed in bits per second
12694 (for example, @samp{9600}).
12696 @item target e7000 @var{hostname}
12697 If your E7000 is installed as a host on a TCP/IP network, you can just
12698 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
12701 @node Renesas Special
12702 @subsubsection Special @value{GDBN} commands for Renesas micros
12704 Some @value{GDBN} commands are available only for the H8/300:
12708 @kindex set machine
12709 @kindex show machine
12710 @item set machine h8300
12711 @itemx set machine h8300h
12712 Condition @value{GDBN} for one of the two variants of the H8/300
12713 architecture with @samp{set machine}. You can use @samp{show machine}
12714 to check which variant is currently in effect.
12723 @kindex set memory @var{mod}
12724 @cindex memory models, H8/500
12725 @item set memory @var{mod}
12727 Specify which H8/500 memory model (@var{mod}) you are using with
12728 @samp{set memory}; check which memory model is in effect with @samp{show
12729 memory}. The accepted values for @var{mod} are @code{small},
12730 @code{big}, @code{medium}, and @code{compact}.
12735 @subsection Renesas M32R/D
12739 @kindex target m32r
12740 @item target m32r @var{dev}
12741 Renesas M32R/D ROM monitor.
12743 @kindex target m32rsdi
12744 @item target m32rsdi @var{dev}
12745 Renesas M32R SDI server, connected via parallel port to the board.
12752 The Motorola m68k configuration includes ColdFire support, and
12753 target command for the following ROM monitors.
12757 @kindex target abug
12758 @item target abug @var{dev}
12759 ABug ROM monitor for M68K.
12761 @kindex target cpu32bug
12762 @item target cpu32bug @var{dev}
12763 CPU32BUG monitor, running on a CPU32 (M68K) board.
12765 @kindex target dbug
12766 @item target dbug @var{dev}
12767 dBUG ROM monitor for Motorola ColdFire.
12770 @item target est @var{dev}
12771 EST-300 ICE monitor, running on a CPU32 (M68K) board.
12773 @kindex target rom68k
12774 @item target rom68k @var{dev}
12775 ROM 68K monitor, running on an M68K IDP board.
12781 @kindex target rombug
12782 @item target rombug @var{dev}
12783 ROMBUG ROM monitor for OS/9000.
12787 @node MIPS Embedded
12788 @subsection MIPS Embedded
12790 @cindex MIPS boards
12791 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
12792 MIPS board attached to a serial line. This is available when
12793 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
12796 Use these @value{GDBN} commands to specify the connection to your target board:
12799 @item target mips @var{port}
12800 @kindex target mips @var{port}
12801 To run a program on the board, start up @code{@value{GDBP}} with the
12802 name of your program as the argument. To connect to the board, use the
12803 command @samp{target mips @var{port}}, where @var{port} is the name of
12804 the serial port connected to the board. If the program has not already
12805 been downloaded to the board, you may use the @code{load} command to
12806 download it. You can then use all the usual @value{GDBN} commands.
12808 For example, this sequence connects to the target board through a serial
12809 port, and loads and runs a program called @var{prog} through the
12813 host$ @value{GDBP} @var{prog}
12814 @value{GDBN} is free software and @dots{}
12815 (@value{GDBP}) target mips /dev/ttyb
12816 (@value{GDBP}) load @var{prog}
12820 @item target mips @var{hostname}:@var{portnumber}
12821 On some @value{GDBN} host configurations, you can specify a TCP
12822 connection (for instance, to a serial line managed by a terminal
12823 concentrator) instead of a serial port, using the syntax
12824 @samp{@var{hostname}:@var{portnumber}}.
12826 @item target pmon @var{port}
12827 @kindex target pmon @var{port}
12830 @item target ddb @var{port}
12831 @kindex target ddb @var{port}
12832 NEC's DDB variant of PMON for Vr4300.
12834 @item target lsi @var{port}
12835 @kindex target lsi @var{port}
12836 LSI variant of PMON.
12838 @kindex target r3900
12839 @item target r3900 @var{dev}
12840 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
12842 @kindex target array
12843 @item target array @var{dev}
12844 Array Tech LSI33K RAID controller board.
12850 @value{GDBN} also supports these special commands for MIPS targets:
12853 @item set processor @var{args}
12854 @itemx show processor
12855 @kindex set processor @var{args}
12856 @kindex show processor
12857 Use the @code{set processor} command to set the type of MIPS
12858 processor when you want to access processor-type-specific registers.
12859 For example, @code{set processor @var{r3041}} tells @value{GDBN}
12860 to use the CPU registers appropriate for the 3041 chip.
12861 Use the @code{show processor} command to see what MIPS processor @value{GDBN}
12862 is using. Use the @code{info reg} command to see what registers
12863 @value{GDBN} is using.
12865 @item set mipsfpu double
12866 @itemx set mipsfpu single
12867 @itemx set mipsfpu none
12868 @itemx show mipsfpu
12869 @kindex set mipsfpu
12870 @kindex show mipsfpu
12871 @cindex MIPS remote floating point
12872 @cindex floating point, MIPS remote
12873 If your target board does not support the MIPS floating point
12874 coprocessor, you should use the command @samp{set mipsfpu none} (if you
12875 need this, you may wish to put the command in your @value{GDBN} init
12876 file). This tells @value{GDBN} how to find the return value of
12877 functions which return floating point values. It also allows
12878 @value{GDBN} to avoid saving the floating point registers when calling
12879 functions on the board. If you are using a floating point coprocessor
12880 with only single precision floating point support, as on the @sc{r4650}
12881 processor, use the command @samp{set mipsfpu single}. The default
12882 double precision floating point coprocessor may be selected using
12883 @samp{set mipsfpu double}.
12885 In previous versions the only choices were double precision or no
12886 floating point, so @samp{set mipsfpu on} will select double precision
12887 and @samp{set mipsfpu off} will select no floating point.
12889 As usual, you can inquire about the @code{mipsfpu} variable with
12890 @samp{show mipsfpu}.
12892 @item set remotedebug @var{n}
12893 @itemx show remotedebug
12894 @kindex set remotedebug@r{, MIPS protocol}
12895 @kindex show remotedebug@r{, MIPS protocol}
12896 @cindex @code{remotedebug}, MIPS protocol
12897 @cindex MIPS @code{remotedebug} protocol
12898 @c FIXME! For this to be useful, you must know something about the MIPS
12899 @c FIXME...protocol. Where is it described?
12900 You can see some debugging information about communications with the board
12901 by setting the @code{remotedebug} variable. If you set it to @code{1} using
12902 @samp{set remotedebug 1}, every packet is displayed. If you set it
12903 to @code{2}, every character is displayed. You can check the current value
12904 at any time with the command @samp{show remotedebug}.
12906 @item set timeout @var{seconds}
12907 @itemx set retransmit-timeout @var{seconds}
12908 @itemx show timeout
12909 @itemx show retransmit-timeout
12910 @cindex @code{timeout}, MIPS protocol
12911 @cindex @code{retransmit-timeout}, MIPS protocol
12912 @kindex set timeout
12913 @kindex show timeout
12914 @kindex set retransmit-timeout
12915 @kindex show retransmit-timeout
12916 You can control the timeout used while waiting for a packet, in the MIPS
12917 remote protocol, with the @code{set timeout @var{seconds}} command. The
12918 default is 5 seconds. Similarly, you can control the timeout used while
12919 waiting for an acknowledgement of a packet with the @code{set
12920 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
12921 You can inspect both values with @code{show timeout} and @code{show
12922 retransmit-timeout}. (These commands are @emph{only} available when
12923 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
12925 The timeout set by @code{set timeout} does not apply when @value{GDBN}
12926 is waiting for your program to stop. In that case, @value{GDBN} waits
12927 forever because it has no way of knowing how long the program is going
12928 to run before stopping.
12931 @node OpenRISC 1000
12932 @subsection OpenRISC 1000
12933 @cindex OpenRISC 1000
12935 @cindex or1k boards
12936 See OR1k Architecture document (@uref{www.opencores.org}) for more information
12937 about platform and commands.
12941 @kindex target jtag
12942 @item target jtag jtag://@var{host}:@var{port}
12944 Connects to remote JTAG server.
12945 JTAG remote server can be either an or1ksim or JTAG server,
12946 connected via parallel port to the board.
12948 Example: @code{target jtag jtag://localhost:9999}
12951 @item or1ksim @var{command}
12952 If connected to @code{or1ksim} OpenRISC 1000 Architectural
12953 Simulator, proprietary commands can be executed.
12955 @kindex info or1k spr
12956 @item info or1k spr
12957 Displays spr groups.
12959 @item info or1k spr @var{group}
12960 @itemx info or1k spr @var{groupno}
12961 Displays register names in selected group.
12963 @item info or1k spr @var{group} @var{register}
12964 @itemx info or1k spr @var{register}
12965 @itemx info or1k spr @var{groupno} @var{registerno}
12966 @itemx info or1k spr @var{registerno}
12967 Shows information about specified spr register.
12970 @item spr @var{group} @var{register} @var{value}
12971 @itemx spr @var{register @var{value}}
12972 @itemx spr @var{groupno} @var{registerno @var{value}}
12973 @itemx spr @var{registerno @var{value}}
12974 Writes @var{value} to specified spr register.
12977 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
12978 It is very similar to @value{GDBN} trace, except it does not interfere with normal
12979 program execution and is thus much faster. Hardware breakpoints/watchpoint
12980 triggers can be set using:
12983 Load effective address/data
12985 Store effective address/data
12987 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
12992 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
12993 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
12995 @code{htrace} commands:
12996 @cindex OpenRISC 1000 htrace
12999 @item hwatch @var{conditional}
13000 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
13001 or Data. For example:
13003 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
13005 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
13009 Display information about current HW trace configuration.
13011 @item htrace trigger @var{conditional}
13012 Set starting criteria for HW trace.
13014 @item htrace qualifier @var{conditional}
13015 Set acquisition qualifier for HW trace.
13017 @item htrace stop @var{conditional}
13018 Set HW trace stopping criteria.
13020 @item htrace record [@var{data}]*
13021 Selects the data to be recorded, when qualifier is met and HW trace was
13024 @item htrace enable
13025 @itemx htrace disable
13026 Enables/disables the HW trace.
13028 @item htrace rewind [@var{filename}]
13029 Clears currently recorded trace data.
13031 If filename is specified, new trace file is made and any newly collected data
13032 will be written there.
13034 @item htrace print [@var{start} [@var{len}]]
13035 Prints trace buffer, using current record configuration.
13037 @item htrace mode continuous
13038 Set continuous trace mode.
13040 @item htrace mode suspend
13041 Set suspend trace mode.
13046 @subsection PowerPC
13050 @kindex target dink32
13051 @item target dink32 @var{dev}
13052 DINK32 ROM monitor.
13054 @kindex target ppcbug
13055 @item target ppcbug @var{dev}
13056 @kindex target ppcbug1
13057 @item target ppcbug1 @var{dev}
13058 PPCBUG ROM monitor for PowerPC.
13061 @item target sds @var{dev}
13062 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
13067 @subsection HP PA Embedded
13071 @kindex target op50n
13072 @item target op50n @var{dev}
13073 OP50N monitor, running on an OKI HPPA board.
13075 @kindex target w89k
13076 @item target w89k @var{dev}
13077 W89K monitor, running on a Winbond HPPA board.
13082 @subsection Renesas SH
13086 @kindex target hms@r{, with Renesas SH}
13087 @item target hms @var{dev}
13088 A Renesas SH board attached via serial line to your host. Use special
13089 commands @code{device} and @code{speed} to control the serial line and
13090 the communications speed used.
13092 @kindex target e7000@r{, with Renesas SH}
13093 @item target e7000 @var{dev}
13094 E7000 emulator for Renesas SH.
13096 @kindex target sh3@r{, with SH}
13097 @kindex target sh3e@r{, with SH}
13098 @item target sh3 @var{dev}
13099 @item target sh3e @var{dev}
13100 Renesas SH-3 and SH-3E target systems.
13105 @subsection Tsqware Sparclet
13109 @value{GDBN} enables developers to debug tasks running on
13110 Sparclet targets from a Unix host.
13111 @value{GDBN} uses code that runs on
13112 both the Unix host and on the Sparclet target. The program
13113 @code{@value{GDBP}} is installed and executed on the Unix host.
13116 @item remotetimeout @var{args}
13117 @kindex remotetimeout
13118 @value{GDBN} supports the option @code{remotetimeout}.
13119 This option is set by the user, and @var{args} represents the number of
13120 seconds @value{GDBN} waits for responses.
13123 @cindex compiling, on Sparclet
13124 When compiling for debugging, include the options @samp{-g} to get debug
13125 information and @samp{-Ttext} to relocate the program to where you wish to
13126 load it on the target. You may also want to add the options @samp{-n} or
13127 @samp{-N} in order to reduce the size of the sections. Example:
13130 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
13133 You can use @code{objdump} to verify that the addresses are what you intended:
13136 sparclet-aout-objdump --headers --syms prog
13139 @cindex running, on Sparclet
13141 your Unix execution search path to find @value{GDBN}, you are ready to
13142 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
13143 (or @code{sparclet-aout-gdb}, depending on your installation).
13145 @value{GDBN} comes up showing the prompt:
13152 * Sparclet File:: Setting the file to debug
13153 * Sparclet Connection:: Connecting to Sparclet
13154 * Sparclet Download:: Sparclet download
13155 * Sparclet Execution:: Running and debugging
13158 @node Sparclet File
13159 @subsubsection Setting file to debug
13161 The @value{GDBN} command @code{file} lets you choose with program to debug.
13164 (gdbslet) file prog
13168 @value{GDBN} then attempts to read the symbol table of @file{prog}.
13169 @value{GDBN} locates
13170 the file by searching the directories listed in the command search
13172 If the file was compiled with debug information (option "-g"), source
13173 files will be searched as well.
13174 @value{GDBN} locates
13175 the source files by searching the directories listed in the directory search
13176 path (@pxref{Environment, ,Your program's environment}).
13178 to find a file, it displays a message such as:
13181 prog: No such file or directory.
13184 When this happens, add the appropriate directories to the search paths with
13185 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
13186 @code{target} command again.
13188 @node Sparclet Connection
13189 @subsubsection Connecting to Sparclet
13191 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
13192 To connect to a target on serial port ``@code{ttya}'', type:
13195 (gdbslet) target sparclet /dev/ttya
13196 Remote target sparclet connected to /dev/ttya
13197 main () at ../prog.c:3
13201 @value{GDBN} displays messages like these:
13207 @node Sparclet Download
13208 @subsubsection Sparclet download
13210 @cindex download to Sparclet
13211 Once connected to the Sparclet target,
13212 you can use the @value{GDBN}
13213 @code{load} command to download the file from the host to the target.
13214 The file name and load offset should be given as arguments to the @code{load}
13216 Since the file format is aout, the program must be loaded to the starting
13217 address. You can use @code{objdump} to find out what this value is. The load
13218 offset is an offset which is added to the VMA (virtual memory address)
13219 of each of the file's sections.
13220 For instance, if the program
13221 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
13222 and bss at 0x12010170, in @value{GDBN}, type:
13225 (gdbslet) load prog 0x12010000
13226 Loading section .text, size 0xdb0 vma 0x12010000
13229 If the code is loaded at a different address then what the program was linked
13230 to, you may need to use the @code{section} and @code{add-symbol-file} commands
13231 to tell @value{GDBN} where to map the symbol table.
13233 @node Sparclet Execution
13234 @subsubsection Running and debugging
13236 @cindex running and debugging Sparclet programs
13237 You can now begin debugging the task using @value{GDBN}'s execution control
13238 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
13239 manual for the list of commands.
13243 Breakpoint 1 at 0x12010000: file prog.c, line 3.
13245 Starting program: prog
13246 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
13247 3 char *symarg = 0;
13249 4 char *execarg = "hello!";
13254 @subsection Fujitsu Sparclite
13258 @kindex target sparclite
13259 @item target sparclite @var{dev}
13260 Fujitsu sparclite boards, used only for the purpose of loading.
13261 You must use an additional command to debug the program.
13262 For example: target remote @var{dev} using @value{GDBN} standard
13268 @subsection Tandem ST2000
13270 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
13273 To connect your ST2000 to the host system, see the manufacturer's
13274 manual. Once the ST2000 is physically attached, you can run:
13277 target st2000 @var{dev} @var{speed}
13281 to establish it as your debugging environment. @var{dev} is normally
13282 the name of a serial device, such as @file{/dev/ttya}, connected to the
13283 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
13284 connection (for example, to a serial line attached via a terminal
13285 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
13287 The @code{load} and @code{attach} commands are @emph{not} defined for
13288 this target; you must load your program into the ST2000 as you normally
13289 would for standalone operation. @value{GDBN} reads debugging information
13290 (such as symbols) from a separate, debugging version of the program
13291 available on your host computer.
13292 @c FIXME!! This is terribly vague; what little content is here is
13293 @c basically hearsay.
13295 @cindex ST2000 auxiliary commands
13296 These auxiliary @value{GDBN} commands are available to help you with the ST2000
13300 @item st2000 @var{command}
13301 @kindex st2000 @var{cmd}
13302 @cindex STDBUG commands (ST2000)
13303 @cindex commands to STDBUG (ST2000)
13304 Send a @var{command} to the STDBUG monitor. See the manufacturer's
13305 manual for available commands.
13308 @cindex connect (to STDBUG)
13309 Connect the controlling terminal to the STDBUG command monitor. When
13310 you are done interacting with STDBUG, typing either of two character
13311 sequences gets you back to the @value{GDBN} command prompt:
13312 @kbd{@key{RET}~.} (Return, followed by tilde and period) or
13313 @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
13317 @subsection Zilog Z8000
13320 @cindex simulator, Z8000
13321 @cindex Zilog Z8000 simulator
13323 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
13326 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
13327 unsegmented variant of the Z8000 architecture) or the Z8001 (the
13328 segmented variant). The simulator recognizes which architecture is
13329 appropriate by inspecting the object code.
13332 @item target sim @var{args}
13334 @kindex target sim@r{, with Z8000}
13335 Debug programs on a simulated CPU. If the simulator supports setup
13336 options, specify them via @var{args}.
13340 After specifying this target, you can debug programs for the simulated
13341 CPU in the same style as programs for your host computer; use the
13342 @code{file} command to load a new program image, the @code{run} command
13343 to run your program, and so on.
13345 As well as making available all the usual machine registers
13346 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
13347 additional items of information as specially named registers:
13352 Counts clock-ticks in the simulator.
13355 Counts instructions run in the simulator.
13358 Execution time in 60ths of a second.
13362 You can refer to these values in @value{GDBN} expressions with the usual
13363 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
13364 conditional breakpoint that suspends only after at least 5000
13365 simulated clock ticks.
13367 @node Architectures
13368 @section Architectures
13370 This section describes characteristics of architectures that affect
13371 all uses of @value{GDBN} with the architecture, both native and cross.
13384 @kindex set rstack_high_address
13385 @cindex AMD 29K register stack
13386 @cindex register stack, AMD29K
13387 @item set rstack_high_address @var{address}
13388 On AMD 29000 family processors, registers are saved in a separate
13389 @dfn{register stack}. There is no way for @value{GDBN} to determine the
13390 extent of this stack. Normally, @value{GDBN} just assumes that the
13391 stack is ``large enough''. This may result in @value{GDBN} referencing
13392 memory locations that do not exist. If necessary, you can get around
13393 this problem by specifying the ending address of the register stack with
13394 the @code{set rstack_high_address} command. The argument should be an
13395 address, which you probably want to precede with @samp{0x} to specify in
13398 @kindex show rstack_high_address
13399 @item show rstack_high_address
13400 Display the current limit of the register stack, on AMD 29000 family
13408 See the following section.
13413 @cindex stack on Alpha
13414 @cindex stack on MIPS
13415 @cindex Alpha stack
13417 Alpha- and MIPS-based computers use an unusual stack frame, which
13418 sometimes requires @value{GDBN} to search backward in the object code to
13419 find the beginning of a function.
13421 @cindex response time, MIPS debugging
13422 To improve response time (especially for embedded applications, where
13423 @value{GDBN} may be restricted to a slow serial line for this search)
13424 you may want to limit the size of this search, using one of these
13428 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
13429 @item set heuristic-fence-post @var{limit}
13430 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
13431 search for the beginning of a function. A value of @var{0} (the
13432 default) means there is no limit. However, except for @var{0}, the
13433 larger the limit the more bytes @code{heuristic-fence-post} must search
13434 and therefore the longer it takes to run.
13436 @item show heuristic-fence-post
13437 Display the current limit.
13441 These commands are available @emph{only} when @value{GDBN} is configured
13442 for debugging programs on Alpha or MIPS processors.
13445 @node Controlling GDB
13446 @chapter Controlling @value{GDBN}
13448 You can alter the way @value{GDBN} interacts with you by using the
13449 @code{set} command. For commands controlling how @value{GDBN} displays
13450 data, see @ref{Print Settings, ,Print settings}. Other settings are
13455 * Editing:: Command editing
13456 * History:: Command history
13457 * Screen Size:: Screen size
13458 * Numbers:: Numbers
13459 * ABI:: Configuring the current ABI
13460 * Messages/Warnings:: Optional warnings and messages
13461 * Debugging Output:: Optional messages about internal happenings
13469 @value{GDBN} indicates its readiness to read a command by printing a string
13470 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
13471 can change the prompt string with the @code{set prompt} command. For
13472 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
13473 the prompt in one of the @value{GDBN} sessions so that you can always tell
13474 which one you are talking to.
13476 @emph{Note:} @code{set prompt} does not add a space for you after the
13477 prompt you set. This allows you to set a prompt which ends in a space
13478 or a prompt that does not.
13482 @item set prompt @var{newprompt}
13483 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
13485 @kindex show prompt
13487 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
13491 @section Command editing
13493 @cindex command line editing
13495 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
13496 @sc{gnu} library provides consistent behavior for programs which provide a
13497 command line interface to the user. Advantages are @sc{gnu} Emacs-style
13498 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
13499 substitution, and a storage and recall of command history across
13500 debugging sessions.
13502 You may control the behavior of command line editing in @value{GDBN} with the
13503 command @code{set}.
13506 @kindex set editing
13509 @itemx set editing on
13510 Enable command line editing (enabled by default).
13512 @item set editing off
13513 Disable command line editing.
13515 @kindex show editing
13517 Show whether command line editing is enabled.
13520 @xref{Command Line Editing}, for more details about the Readline
13521 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
13522 encouraged to read that chapter.
13525 @section Command history
13526 @cindex command history
13528 @value{GDBN} can keep track of the commands you type during your
13529 debugging sessions, so that you can be certain of precisely what
13530 happened. Use these commands to manage the @value{GDBN} command
13533 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
13534 package, to provide the history facility. @xref{Using History
13535 Interactively}, for the detailed description of the History library.
13537 Here is the description of @value{GDBN} commands related to command
13541 @cindex history substitution
13542 @cindex history file
13543 @kindex set history filename
13544 @cindex @env{GDBHISTFILE}, environment variable
13545 @item set history filename @var{fname}
13546 Set the name of the @value{GDBN} command history file to @var{fname}.
13547 This is the file where @value{GDBN} reads an initial command history
13548 list, and where it writes the command history from this session when it
13549 exits. You can access this list through history expansion or through
13550 the history command editing characters listed below. This file defaults
13551 to the value of the environment variable @code{GDBHISTFILE}, or to
13552 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
13555 @cindex history save
13556 @kindex set history
13557 @item set history save
13558 @itemx set history save on
13559 Record command history in a file, whose name may be specified with the
13560 @code{set history filename} command. By default, this option is disabled.
13562 @item set history save off
13563 Stop recording command history in a file.
13565 @cindex history size
13566 @item set history size @var{size}
13567 Set the number of commands which @value{GDBN} keeps in its history list.
13568 This defaults to the value of the environment variable
13569 @code{HISTSIZE}, or to 256 if this variable is not set.
13572 History expansion assigns special meaning to the character @kbd{!}.
13573 @xref{Event Designators}, for more details.
13575 @cindex history expansion, turn on/off
13576 Since @kbd{!} is also the logical not operator in C, history expansion
13577 is off by default. If you decide to enable history expansion with the
13578 @code{set history expansion on} command, you may sometimes need to
13579 follow @kbd{!} (when it is used as logical not, in an expression) with
13580 a space or a tab to prevent it from being expanded. The readline
13581 history facilities do not attempt substitution on the strings
13582 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
13584 The commands to control history expansion are:
13587 @item set history expansion on
13588 @itemx set history expansion
13589 @kindex set history expansion
13590 Enable history expansion. History expansion is off by default.
13592 @item set history expansion off
13593 Disable history expansion.
13596 @kindex show history
13598 @itemx show history filename
13599 @itemx show history save
13600 @itemx show history size
13601 @itemx show history expansion
13602 These commands display the state of the @value{GDBN} history parameters.
13603 @code{show history} by itself displays all four states.
13609 @item show commands
13610 Display the last ten commands in the command history.
13612 @item show commands @var{n}
13613 Print ten commands centered on command number @var{n}.
13615 @item show commands +
13616 Print ten commands just after the commands last printed.
13620 @section Screen size
13621 @cindex size of screen
13622 @cindex pauses in output
13624 Certain commands to @value{GDBN} may produce large amounts of
13625 information output to the screen. To help you read all of it,
13626 @value{GDBN} pauses and asks you for input at the end of each page of
13627 output. Type @key{RET} when you want to continue the output, or @kbd{q}
13628 to discard the remaining output. Also, the screen width setting
13629 determines when to wrap lines of output. Depending on what is being
13630 printed, @value{GDBN} tries to break the line at a readable place,
13631 rather than simply letting it overflow onto the following line.
13633 Normally @value{GDBN} knows the size of the screen from the terminal
13634 driver software. For example, on Unix @value{GDBN} uses the termcap data base
13635 together with the value of the @code{TERM} environment variable and the
13636 @code{stty rows} and @code{stty cols} settings. If this is not correct,
13637 you can override it with the @code{set height} and @code{set
13644 @kindex show height
13645 @item set height @var{lpp}
13647 @itemx set width @var{cpl}
13649 These @code{set} commands specify a screen height of @var{lpp} lines and
13650 a screen width of @var{cpl} characters. The associated @code{show}
13651 commands display the current settings.
13653 If you specify a height of zero lines, @value{GDBN} does not pause during
13654 output no matter how long the output is. This is useful if output is to a
13655 file or to an editor buffer.
13657 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
13658 from wrapping its output.
13663 @cindex number representation
13664 @cindex entering numbers
13666 You can always enter numbers in octal, decimal, or hexadecimal in
13667 @value{GDBN} by the usual conventions: octal numbers begin with
13668 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
13669 begin with @samp{0x}. Numbers that begin with none of these are, by
13670 default, entered in base 10; likewise, the default display for
13671 numbers---when no particular format is specified---is base 10. You can
13672 change the default base for both input and output with the @code{set
13676 @kindex set input-radix
13677 @item set input-radix @var{base}
13678 Set the default base for numeric input. Supported choices
13679 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
13680 specified either unambiguously or using the current default radix; for
13690 sets the base to decimal. On the other hand, @samp{set radix 10}
13691 leaves the radix unchanged no matter what it was.
13693 @kindex set output-radix
13694 @item set output-radix @var{base}
13695 Set the default base for numeric display. Supported choices
13696 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
13697 specified either unambiguously or using the current default radix.
13699 @kindex show input-radix
13700 @item show input-radix
13701 Display the current default base for numeric input.
13703 @kindex show output-radix
13704 @item show output-radix
13705 Display the current default base for numeric display.
13709 @section Configuring the current ABI
13711 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
13712 application automatically. However, sometimes you need to override its
13713 conclusions. Use these commands to manage @value{GDBN}'s view of the
13720 One @value{GDBN} configuration can debug binaries for multiple operating
13721 system targets, either via remote debugging or native emulation.
13722 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
13723 but you can override its conclusion using the @code{set osabi} command.
13724 One example where this is useful is in debugging of binaries which use
13725 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
13726 not have the same identifying marks that the standard C library for your
13731 Show the OS ABI currently in use.
13734 With no argument, show the list of registered available OS ABI's.
13736 @item set osabi @var{abi}
13737 Set the current OS ABI to @var{abi}.
13740 @cindex float promotion
13741 @kindex set coerce-float-to-double
13743 Generally, the way that an argument of type @code{float} is passed to a
13744 function depends on whether the function is prototyped. For a prototyped
13745 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
13746 according to the architecture's convention for @code{float}. For unprototyped
13747 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
13748 @code{double} and then passed.
13750 Unfortunately, some forms of debug information do not reliably indicate whether
13751 a function is prototyped. If @value{GDBN} calls a function that is not marked
13752 as prototyped, it consults @kbd{set coerce-float-to-double}.
13755 @item set coerce-float-to-double
13756 @itemx set coerce-float-to-double on
13757 Arguments of type @code{float} will be promoted to @code{double} when passed
13758 to an unprototyped function. This is the default setting.
13760 @item set coerce-float-to-double off
13761 Arguments of type @code{float} will be passed directly to unprototyped
13766 @kindex show cp-abi
13767 @value{GDBN} needs to know the ABI used for your program's C@t{++}
13768 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
13769 used to build your application. @value{GDBN} only fully supports
13770 programs with a single C@t{++} ABI; if your program contains code using
13771 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
13772 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
13773 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
13774 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
13775 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
13776 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
13781 Show the C@t{++} ABI currently in use.
13784 With no argument, show the list of supported C@t{++} ABI's.
13786 @item set cp-abi @var{abi}
13787 @itemx set cp-abi auto
13788 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
13791 @node Messages/Warnings
13792 @section Optional warnings and messages
13794 By default, @value{GDBN} is silent about its inner workings. If you are
13795 running on a slow machine, you may want to use the @code{set verbose}
13796 command. This makes @value{GDBN} tell you when it does a lengthy
13797 internal operation, so you will not think it has crashed.
13799 Currently, the messages controlled by @code{set verbose} are those
13800 which announce that the symbol table for a source file is being read;
13801 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
13804 @kindex set verbose
13805 @item set verbose on
13806 Enables @value{GDBN} output of certain informational messages.
13808 @item set verbose off
13809 Disables @value{GDBN} output of certain informational messages.
13811 @kindex show verbose
13813 Displays whether @code{set verbose} is on or off.
13816 By default, if @value{GDBN} encounters bugs in the symbol table of an
13817 object file, it is silent; but if you are debugging a compiler, you may
13818 find this information useful (@pxref{Symbol Errors, ,Errors reading
13823 @kindex set complaints
13824 @item set complaints @var{limit}
13825 Permits @value{GDBN} to output @var{limit} complaints about each type of
13826 unusual symbols before becoming silent about the problem. Set
13827 @var{limit} to zero to suppress all complaints; set it to a large number
13828 to prevent complaints from being suppressed.
13830 @kindex show complaints
13831 @item show complaints
13832 Displays how many symbol complaints @value{GDBN} is permitted to produce.
13836 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
13837 lot of stupid questions to confirm certain commands. For example, if
13838 you try to run a program which is already running:
13842 The program being debugged has been started already.
13843 Start it from the beginning? (y or n)
13846 If you are willing to unflinchingly face the consequences of your own
13847 commands, you can disable this ``feature'':
13851 @kindex set confirm
13853 @cindex confirmation
13854 @cindex stupid questions
13855 @item set confirm off
13856 Disables confirmation requests.
13858 @item set confirm on
13859 Enables confirmation requests (the default).
13861 @kindex show confirm
13863 Displays state of confirmation requests.
13867 @node Debugging Output
13868 @section Optional messages about internal happenings
13869 @cindex optional debugging messages
13873 @cindex gdbarch debugging info
13874 @item set debug arch
13875 Turns on or off display of gdbarch debugging info. The default is off
13877 @item show debug arch
13878 Displays the current state of displaying gdbarch debugging info.
13879 @item set debug event
13880 @cindex event debugging info
13881 Turns on or off display of @value{GDBN} event debugging info. The
13883 @item show debug event
13884 Displays the current state of displaying @value{GDBN} event debugging
13886 @item set debug expression
13887 @cindex expression debugging info
13888 Turns on or off display of @value{GDBN} expression debugging info. The
13890 @item show debug expression
13891 Displays the current state of displaying @value{GDBN} expression
13893 @item set debug frame
13894 @cindex frame debugging info
13895 Turns on or off display of @value{GDBN} frame debugging info. The
13897 @item show debug frame
13898 Displays the current state of displaying @value{GDBN} frame debugging
13900 @item set debug infrun
13901 @cindex inferior debugging info
13902 Turns on or off display of @value{GDBN} debugging info for running the inferior.
13903 The default is off. @file{infrun.c} contains GDB's runtime state machine used
13904 for implementing operations such as single-stepping the inferior.
13905 @item show debug infrun
13906 Displays the current state of @value{GDBN} inferior debugging.
13907 @item set debug observer
13908 @cindex observer debugging info
13909 Turns on or off display of @value{GDBN} observer debugging. This
13910 includes info such as the notification of observable events.
13911 @item show debug observer
13912 Displays the current state of observer debugging.
13913 @item set debug overload
13914 @cindex C@t{++} overload debugging info
13915 Turns on or off display of @value{GDBN} C@t{++} overload debugging
13916 info. This includes info such as ranking of functions, etc. The default
13918 @item show debug overload
13919 Displays the current state of displaying @value{GDBN} C@t{++} overload
13921 @cindex packets, reporting on stdout
13922 @cindex serial connections, debugging
13923 @item set debug remote
13924 Turns on or off display of reports on all packets sent back and forth across
13925 the serial line to the remote machine. The info is printed on the
13926 @value{GDBN} standard output stream. The default is off.
13927 @item show debug remote
13928 Displays the state of display of remote packets.
13929 @item set debug serial
13930 Turns on or off display of @value{GDBN} serial debugging info. The
13932 @item show debug serial
13933 Displays the current state of displaying @value{GDBN} serial debugging
13935 @item set debug target
13936 @cindex target debugging info
13937 Turns on or off display of @value{GDBN} target debugging info. This info
13938 includes what is going on at the target level of GDB, as it happens. The
13939 default is 0. Set it to 1 to track events, and to 2 to also track the
13940 value of large memory transfers. Changes to this flag do not take effect
13941 until the next time you connect to a target or use the @code{run} command.
13942 @item show debug target
13943 Displays the current state of displaying @value{GDBN} target debugging
13945 @item set debug varobj
13946 @cindex variable object debugging info
13947 Turns on or off display of @value{GDBN} variable object debugging
13948 info. The default is off.
13949 @item show debug varobj
13950 Displays the current state of displaying @value{GDBN} variable object
13955 @chapter Canned Sequences of Commands
13957 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
13958 command lists}), @value{GDBN} provides two ways to store sequences of
13959 commands for execution as a unit: user-defined commands and command
13963 * Define:: User-defined commands
13964 * Hooks:: User-defined command hooks
13965 * Command Files:: Command files
13966 * Output:: Commands for controlled output
13970 @section User-defined commands
13972 @cindex user-defined command
13973 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
13974 which you assign a new name as a command. This is done with the
13975 @code{define} command. User commands may accept up to 10 arguments
13976 separated by whitespace. Arguments are accessed within the user command
13977 via @var{$arg0@dots{}$arg9}. A trivial example:
13981 print $arg0 + $arg1 + $arg2
13985 To execute the command use:
13992 This defines the command @code{adder}, which prints the sum of
13993 its three arguments. Note the arguments are text substitutions, so they may
13994 reference variables, use complex expressions, or even perform inferior
14000 @item define @var{commandname}
14001 Define a command named @var{commandname}. If there is already a command
14002 by that name, you are asked to confirm that you want to redefine it.
14004 The definition of the command is made up of other @value{GDBN} command lines,
14005 which are given following the @code{define} command. The end of these
14006 commands is marked by a line containing @code{end}.
14011 Takes a single argument, which is an expression to evaluate.
14012 It is followed by a series of commands that are executed
14013 only if the expression is true (nonzero).
14014 There can then optionally be a line @code{else}, followed
14015 by a series of commands that are only executed if the expression
14016 was false. The end of the list is marked by a line containing @code{end}.
14020 The syntax is similar to @code{if}: the command takes a single argument,
14021 which is an expression to evaluate, and must be followed by the commands to
14022 execute, one per line, terminated by an @code{end}.
14023 The commands are executed repeatedly as long as the expression
14027 @item document @var{commandname}
14028 Document the user-defined command @var{commandname}, so that it can be
14029 accessed by @code{help}. The command @var{commandname} must already be
14030 defined. This command reads lines of documentation just as @code{define}
14031 reads the lines of the command definition, ending with @code{end}.
14032 After the @code{document} command is finished, @code{help} on command
14033 @var{commandname} displays the documentation you have written.
14035 You may use the @code{document} command again to change the
14036 documentation of a command. Redefining the command with @code{define}
14037 does not change the documentation.
14039 @kindex help user-defined
14040 @item help user-defined
14041 List all user-defined commands, with the first line of the documentation
14046 @itemx show user @var{commandname}
14047 Display the @value{GDBN} commands used to define @var{commandname} (but
14048 not its documentation). If no @var{commandname} is given, display the
14049 definitions for all user-defined commands.
14051 @kindex show max-user-call-depth
14052 @kindex set max-user-call-depth
14053 @item show max-user-call-depth
14054 @itemx set max-user-call-depth
14055 The value of @code{max-user-call-depth} controls how many recursion
14056 levels are allowed in user-defined commands before GDB suspects an
14057 infinite recursion and aborts the command.
14061 When user-defined commands are executed, the
14062 commands of the definition are not printed. An error in any command
14063 stops execution of the user-defined command.
14065 If used interactively, commands that would ask for confirmation proceed
14066 without asking when used inside a user-defined command. Many @value{GDBN}
14067 commands that normally print messages to say what they are doing omit the
14068 messages when used in a user-defined command.
14071 @section User-defined command hooks
14072 @cindex command hooks
14073 @cindex hooks, for commands
14074 @cindex hooks, pre-command
14077 You may define @dfn{hooks}, which are a special kind of user-defined
14078 command. Whenever you run the command @samp{foo}, if the user-defined
14079 command @samp{hook-foo} exists, it is executed (with no arguments)
14080 before that command.
14082 @cindex hooks, post-command
14084 A hook may also be defined which is run after the command you executed.
14085 Whenever you run the command @samp{foo}, if the user-defined command
14086 @samp{hookpost-foo} exists, it is executed (with no arguments) after
14087 that command. Post-execution hooks may exist simultaneously with
14088 pre-execution hooks, for the same command.
14090 It is valid for a hook to call the command which it hooks. If this
14091 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
14093 @c It would be nice if hookpost could be passed a parameter indicating
14094 @c if the command it hooks executed properly or not. FIXME!
14096 @kindex stop@r{, a pseudo-command}
14097 In addition, a pseudo-command, @samp{stop} exists. Defining
14098 (@samp{hook-stop}) makes the associated commands execute every time
14099 execution stops in your program: before breakpoint commands are run,
14100 displays are printed, or the stack frame is printed.
14102 For example, to ignore @code{SIGALRM} signals while
14103 single-stepping, but treat them normally during normal execution,
14108 handle SIGALRM nopass
14112 handle SIGALRM pass
14115 define hook-continue
14116 handle SIGLARM pass
14120 As a further example, to hook at the begining and end of the @code{echo}
14121 command, and to add extra text to the beginning and end of the message,
14129 define hookpost-echo
14133 (@value{GDBP}) echo Hello World
14134 <<<---Hello World--->>>
14139 You can define a hook for any single-word command in @value{GDBN}, but
14140 not for command aliases; you should define a hook for the basic command
14141 name, e.g. @code{backtrace} rather than @code{bt}.
14142 @c FIXME! So how does Joe User discover whether a command is an alias
14144 If an error occurs during the execution of your hook, execution of
14145 @value{GDBN} commands stops and @value{GDBN} issues a prompt
14146 (before the command that you actually typed had a chance to run).
14148 If you try to define a hook which does not match any known command, you
14149 get a warning from the @code{define} command.
14151 @node Command Files
14152 @section Command files
14154 @cindex command files
14155 A command file for @value{GDBN} is a file of lines that are @value{GDBN}
14156 commands. Comments (lines starting with @kbd{#}) may also be included.
14157 An empty line in a command file does nothing; it does not mean to repeat
14158 the last command, as it would from the terminal.
14161 @cindex @file{.gdbinit}
14162 @cindex @file{gdb.ini}
14163 When you start @value{GDBN}, it automatically executes commands from its
14164 @dfn{init files}, normally called @file{.gdbinit}@footnote{The DJGPP
14165 port of @value{GDBN} uses the name @file{gdb.ini} instead, due to the
14166 limitations of file names imposed by DOS filesystems.}.
14167 During startup, @value{GDBN} does the following:
14171 Reads the init file (if any) in your home directory@footnote{On
14172 DOS/Windows systems, the home directory is the one pointed to by the
14173 @code{HOME} environment variable.}.
14176 Processes command line options and operands.
14179 Reads the init file (if any) in the current working directory.
14182 Reads command files specified by the @samp{-x} option.
14185 The init file in your home directory can set options (such as @samp{set
14186 complaints}) that affect subsequent processing of command line options
14187 and operands. Init files are not executed if you use the @samp{-nx}
14188 option (@pxref{Mode Options, ,Choosing modes}).
14190 @cindex init file name
14191 On some configurations of @value{GDBN}, the init file is known by a
14192 different name (these are typically environments where a specialized
14193 form of @value{GDBN} may need to coexist with other forms, hence a
14194 different name for the specialized version's init file). These are the
14195 environments with special init file names:
14197 @cindex @file{.vxgdbinit}
14200 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
14202 @cindex @file{.os68gdbinit}
14204 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
14206 @cindex @file{.esgdbinit}
14208 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
14211 You can also request the execution of a command file with the
14212 @code{source} command:
14216 @item source @var{filename}
14217 Execute the command file @var{filename}.
14220 The lines in a command file are executed sequentially. They are not
14221 printed as they are executed. An error in any command terminates
14222 execution of the command file and control is returned to the console.
14224 Commands that would ask for confirmation if used interactively proceed
14225 without asking when used in a command file. Many @value{GDBN} commands that
14226 normally print messages to say what they are doing omit the messages
14227 when called from command files.
14229 @value{GDBN} also accepts command input from standard input. In this
14230 mode, normal output goes to standard output and error output goes to
14231 standard error. Errors in a command file supplied on standard input do
14232 not terminate execution of the command file --- execution continues with
14236 gdb < cmds > log 2>&1
14239 (The syntax above will vary depending on the shell used.) This example
14240 will execute commands from the file @file{cmds}. All output and errors
14241 would be directed to @file{log}.
14244 @section Commands for controlled output
14246 During the execution of a command file or a user-defined command, normal
14247 @value{GDBN} output is suppressed; the only output that appears is what is
14248 explicitly printed by the commands in the definition. This section
14249 describes three commands useful for generating exactly the output you
14254 @item echo @var{text}
14255 @c I do not consider backslash-space a standard C escape sequence
14256 @c because it is not in ANSI.
14257 Print @var{text}. Nonprinting characters can be included in
14258 @var{text} using C escape sequences, such as @samp{\n} to print a
14259 newline. @strong{No newline is printed unless you specify one.}
14260 In addition to the standard C escape sequences, a backslash followed
14261 by a space stands for a space. This is useful for displaying a
14262 string with spaces at the beginning or the end, since leading and
14263 trailing spaces are otherwise trimmed from all arguments.
14264 To print @samp{@w{ }and foo =@w{ }}, use the command
14265 @samp{echo \@w{ }and foo = \@w{ }}.
14267 A backslash at the end of @var{text} can be used, as in C, to continue
14268 the command onto subsequent lines. For example,
14271 echo This is some text\n\
14272 which is continued\n\
14273 onto several lines.\n
14276 produces the same output as
14279 echo This is some text\n
14280 echo which is continued\n
14281 echo onto several lines.\n
14285 @item output @var{expression}
14286 Print the value of @var{expression} and nothing but that value: no
14287 newlines, no @samp{$@var{nn} = }. The value is not entered in the
14288 value history either. @xref{Expressions, ,Expressions}, for more information
14291 @item output/@var{fmt} @var{expression}
14292 Print the value of @var{expression} in format @var{fmt}. You can use
14293 the same formats as for @code{print}. @xref{Output Formats,,Output
14294 formats}, for more information.
14297 @item printf @var{string}, @var{expressions}@dots{}
14298 Print the values of the @var{expressions} under the control of
14299 @var{string}. The @var{expressions} are separated by commas and may be
14300 either numbers or pointers. Their values are printed as specified by
14301 @var{string}, exactly as if your program were to execute the C
14303 @c FIXME: the above implies that at least all ANSI C formats are
14304 @c supported, but it isn't true: %E and %G don't work (or so it seems).
14305 @c Either this is a bug, or the manual should document what formats are
14309 printf (@var{string}, @var{expressions}@dots{});
14312 For example, you can print two values in hex like this:
14315 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
14318 The only backslash-escape sequences that you can use in the format
14319 string are the simple ones that consist of backslash followed by a
14324 @chapter Command Interpreters
14325 @cindex command interpreters
14327 @value{GDBN} supports multiple command interpreters, and some command
14328 infrastructure to allow users or user interface writers to switch
14329 between interpreters or run commands in other interpreters.
14331 @value{GDBN} currently supports two command interpreters, the console
14332 interpreter (sometimes called the command-line interpreter or @sc{cli})
14333 and the machine interface interpreter (or @sc{gdb/mi}). This manual
14334 describes both of these interfaces in great detail.
14336 By default, @value{GDBN} will start with the console interpreter.
14337 However, the user may choose to start @value{GDBN} with another
14338 interpreter by specifying the @option{-i} or @option{--interpreter}
14339 startup options. Defined interpreters include:
14343 @cindex console interpreter
14344 The traditional console or command-line interpreter. This is the most often
14345 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
14346 @value{GDBN} will use this interpreter.
14349 @cindex mi interpreter
14350 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
14351 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
14352 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
14356 @cindex mi2 interpreter
14357 The current @sc{gdb/mi} interface.
14360 @cindex mi1 interpreter
14361 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
14365 @cindex invoke another interpreter
14366 The interpreter being used by @value{GDBN} may not be dynamically
14367 switched at runtime. Although possible, this could lead to a very
14368 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
14369 enters the command "interpreter-set console" in a console view,
14370 @value{GDBN} would switch to using the console interpreter, rendering
14371 the IDE inoperable!
14373 @kindex interpreter-exec
14374 Although you may only choose a single interpreter at startup, you may execute
14375 commands in any interpreter from the current interpreter using the appropriate
14376 command. If you are running the console interpreter, simply use the
14377 @code{interpreter-exec} command:
14380 interpreter-exec mi "-data-list-register-names"
14383 @sc{gdb/mi} has a similar command, although it is only available in versions of
14384 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
14387 @chapter @value{GDBN} Text User Interface
14389 @cindex Text User Interface
14392 * TUI Overview:: TUI overview
14393 * TUI Keys:: TUI key bindings
14394 * TUI Single Key Mode:: TUI single key mode
14395 * TUI Commands:: TUI specific commands
14396 * TUI Configuration:: TUI configuration variables
14399 The @value{GDBN} Text User Interface, TUI in short, is a terminal
14400 interface which uses the @code{curses} library to show the source
14401 file, the assembly output, the program registers and @value{GDBN}
14402 commands in separate text windows.
14404 The TUI is enabled by invoking @value{GDBN} using either
14406 @samp{gdbtui} or @samp{gdb -tui}.
14409 @section TUI overview
14411 The TUI has two display modes that can be switched while
14416 A curses (or TUI) mode in which it displays several text
14417 windows on the terminal.
14420 A standard mode which corresponds to the @value{GDBN} configured without
14424 In the TUI mode, @value{GDBN} can display several text window
14429 This window is the @value{GDBN} command window with the @value{GDBN}
14430 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
14431 managed using readline but through the TUI. The @emph{command}
14432 window is always visible.
14435 The source window shows the source file of the program. The current
14436 line as well as active breakpoints are displayed in this window.
14439 The assembly window shows the disassembly output of the program.
14442 This window shows the processor registers. It detects when
14443 a register is changed and when this is the case, registers that have
14444 changed are highlighted.
14448 The source and assembly windows show the current program position
14449 by highlighting the current line and marking them with the @samp{>} marker.
14450 Breakpoints are also indicated with two markers. A first one
14451 indicates the breakpoint type:
14455 Breakpoint which was hit at least once.
14458 Breakpoint which was never hit.
14461 Hardware breakpoint which was hit at least once.
14464 Hardware breakpoint which was never hit.
14468 The second marker indicates whether the breakpoint is enabled or not:
14472 Breakpoint is enabled.
14475 Breakpoint is disabled.
14479 The source, assembly and register windows are attached to the thread
14480 and the frame position. They are updated when the current thread
14481 changes, when the frame changes or when the program counter changes.
14482 These three windows are arranged by the TUI according to several
14483 layouts. The layout defines which of these three windows are visible.
14484 The following layouts are available:
14494 source and assembly
14497 source and registers
14500 assembly and registers
14504 On top of the command window a status line gives various information
14505 concerning the current process begin debugged. The status line is
14506 updated when the information it shows changes. The following fields
14511 Indicates the current gdb target
14512 (@pxref{Targets, ,Specifying a Debugging Target}).
14515 Gives information about the current process or thread number.
14516 When no process is being debugged, this field is set to @code{No process}.
14519 Gives the current function name for the selected frame.
14520 The name is demangled if demangling is turned on (@pxref{Print Settings}).
14521 When there is no symbol corresponding to the current program counter
14522 the string @code{??} is displayed.
14525 Indicates the current line number for the selected frame.
14526 When the current line number is not known the string @code{??} is displayed.
14529 Indicates the current program counter address.
14534 @section TUI Key Bindings
14535 @cindex TUI key bindings
14537 The TUI installs several key bindings in the readline keymaps
14538 (@pxref{Command Line Editing}).
14539 They allow to leave or enter in the TUI mode or they operate
14540 directly on the TUI layout and windows. The TUI also provides
14541 a @emph{SingleKey} keymap which binds several keys directly to
14542 @value{GDBN} commands. The following key bindings
14543 are installed for both TUI mode and the @value{GDBN} standard mode.
14552 Enter or leave the TUI mode. When the TUI mode is left,
14553 the curses window management is left and @value{GDBN} operates using
14554 its standard mode writing on the terminal directly. When the TUI
14555 mode is entered, the control is given back to the curses windows.
14556 The screen is then refreshed.
14560 Use a TUI layout with only one window. The layout will
14561 either be @samp{source} or @samp{assembly}. When the TUI mode
14562 is not active, it will switch to the TUI mode.
14564 Think of this key binding as the Emacs @kbd{C-x 1} binding.
14568 Use a TUI layout with at least two windows. When the current
14569 layout shows already two windows, a next layout with two windows is used.
14570 When a new layout is chosen, one window will always be common to the
14571 previous layout and the new one.
14573 Think of it as the Emacs @kbd{C-x 2} binding.
14577 Change the active window. The TUI associates several key bindings
14578 (like scrolling and arrow keys) to the active window. This command
14579 gives the focus to the next TUI window.
14581 Think of it as the Emacs @kbd{C-x o} binding.
14585 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
14586 (@pxref{TUI Single Key Mode}).
14590 The following key bindings are handled only by the TUI mode:
14595 Scroll the active window one page up.
14599 Scroll the active window one page down.
14603 Scroll the active window one line up.
14607 Scroll the active window one line down.
14611 Scroll the active window one column left.
14615 Scroll the active window one column right.
14619 Refresh the screen.
14623 In the TUI mode, the arrow keys are used by the active window
14624 for scrolling. This means they are available for readline when the
14625 active window is the command window. When the command window
14626 does not have the focus, it is necessary to use other readline
14627 key bindings such as @key{C-p}, @key{C-n}, @key{C-b} and @key{C-f}.
14629 @node TUI Single Key Mode
14630 @section TUI Single Key Mode
14631 @cindex TUI single key mode
14633 The TUI provides a @emph{SingleKey} mode in which it installs a particular
14634 key binding in the readline keymaps to connect single keys to
14638 @kindex c @r{(SingleKey TUI key)}
14642 @kindex d @r{(SingleKey TUI key)}
14646 @kindex f @r{(SingleKey TUI key)}
14650 @kindex n @r{(SingleKey TUI key)}
14654 @kindex q @r{(SingleKey TUI key)}
14656 exit the @emph{SingleKey} mode.
14658 @kindex r @r{(SingleKey TUI key)}
14662 @kindex s @r{(SingleKey TUI key)}
14666 @kindex u @r{(SingleKey TUI key)}
14670 @kindex v @r{(SingleKey TUI key)}
14674 @kindex w @r{(SingleKey TUI key)}
14680 Other keys temporarily switch to the @value{GDBN} command prompt.
14681 The key that was pressed is inserted in the editing buffer so that
14682 it is possible to type most @value{GDBN} commands without interaction
14683 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
14684 @emph{SingleKey} mode is restored. The only way to permanently leave
14685 this mode is by hitting @key{q} or @samp{@key{C-x} @key{s}}.
14689 @section TUI specific commands
14690 @cindex TUI commands
14692 The TUI has specific commands to control the text windows.
14693 These commands are always available, that is they do not depend on
14694 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
14695 is in the standard mode, using these commands will automatically switch
14701 List and give the size of all displayed windows.
14705 Display the next layout.
14708 Display the previous layout.
14711 Display the source window only.
14714 Display the assembly window only.
14717 Display the source and assembly window.
14720 Display the register window together with the source or assembly window.
14722 @item focus next | prev | src | asm | regs | split
14724 Set the focus to the named window.
14725 This command allows to change the active window so that scrolling keys
14726 can be affected to another window.
14730 Refresh the screen. This is similar to using @key{C-L} key.
14732 @item tui reg float
14734 Show the floating point registers in the register window.
14736 @item tui reg general
14737 Show the general registers in the register window.
14740 Show the next register group. The list of register groups as well as
14741 their order is target specific. The predefined register groups are the
14742 following: @code{general}, @code{float}, @code{system}, @code{vector},
14743 @code{all}, @code{save}, @code{restore}.
14745 @item tui reg system
14746 Show the system registers in the register window.
14750 Update the source window and the current execution point.
14752 @item winheight @var{name} +@var{count}
14753 @itemx winheight @var{name} -@var{count}
14755 Change the height of the window @var{name} by @var{count}
14756 lines. Positive counts increase the height, while negative counts
14761 @node TUI Configuration
14762 @section TUI configuration variables
14763 @cindex TUI configuration variables
14765 The TUI has several configuration variables that control the
14766 appearance of windows on the terminal.
14769 @item set tui border-kind @var{kind}
14770 @kindex set tui border-kind
14771 Select the border appearance for the source, assembly and register windows.
14772 The possible values are the following:
14775 Use a space character to draw the border.
14778 Use ascii characters + - and | to draw the border.
14781 Use the Alternate Character Set to draw the border. The border is
14782 drawn using character line graphics if the terminal supports them.
14786 @item set tui active-border-mode @var{mode}
14787 @kindex set tui active-border-mode
14788 Select the attributes to display the border of the active window.
14789 The possible values are @code{normal}, @code{standout}, @code{reverse},
14790 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
14792 @item set tui border-mode @var{mode}
14793 @kindex set tui border-mode
14794 Select the attributes to display the border of other windows.
14795 The @var{mode} can be one of the following:
14798 Use normal attributes to display the border.
14804 Use reverse video mode.
14807 Use half bright mode.
14809 @item half-standout
14810 Use half bright and standout mode.
14813 Use extra bright or bold mode.
14815 @item bold-standout
14816 Use extra bright or bold and standout mode.
14823 @chapter Using @value{GDBN} under @sc{gnu} Emacs
14826 @cindex @sc{gnu} Emacs
14827 A special interface allows you to use @sc{gnu} Emacs to view (and
14828 edit) the source files for the program you are debugging with
14831 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
14832 executable file you want to debug as an argument. This command starts
14833 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
14834 created Emacs buffer.
14835 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
14837 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
14842 All ``terminal'' input and output goes through the Emacs buffer.
14845 This applies both to @value{GDBN} commands and their output, and to the input
14846 and output done by the program you are debugging.
14848 This is useful because it means that you can copy the text of previous
14849 commands and input them again; you can even use parts of the output
14852 All the facilities of Emacs' Shell mode are available for interacting
14853 with your program. In particular, you can send signals the usual
14854 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
14859 @value{GDBN} displays source code through Emacs.
14862 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
14863 source file for that frame and puts an arrow (@samp{=>}) at the
14864 left margin of the current line. Emacs uses a separate buffer for
14865 source display, and splits the screen to show both your @value{GDBN} session
14868 Explicit @value{GDBN} @code{list} or search commands still produce output as
14869 usual, but you probably have no reason to use them from Emacs.
14871 If you specify an absolute file name when prompted for the @kbd{M-x
14872 gdb} argument, then Emacs sets your current working directory to where
14873 your program resides. If you only specify the file name, then Emacs
14874 sets your current working directory to to the directory associated
14875 with the previous buffer. In this case, @value{GDBN} may find your
14876 program by searching your environment's @code{PATH} variable, but on
14877 some operating systems it might not find the source. So, although the
14878 @value{GDBN} input and output session proceeds normally, the auxiliary
14879 buffer does not display the current source and line of execution.
14881 The initial working directory of @value{GDBN} is printed on the top
14882 line of the @value{GDBN} I/O buffer and this serves as a default for
14883 the commands that specify files for @value{GDBN} to operate
14884 on. @xref{Files, ,Commands to specify files}.
14886 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
14887 need to call @value{GDBN} by a different name (for example, if you
14888 keep several configurations around, with different names) you can
14889 customize the Emacs variable @code{gud-gdb-command-name} to run the
14892 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
14893 addition to the standard Shell mode commands:
14897 Describe the features of Emacs' @value{GDBN} Mode.
14900 Execute to another source line, like the @value{GDBN} @code{step} command; also
14901 update the display window to show the current file and location.
14904 Execute to next source line in this function, skipping all function
14905 calls, like the @value{GDBN} @code{next} command. Then update the display window
14906 to show the current file and location.
14909 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
14910 display window accordingly.
14913 Execute until exit from the selected stack frame, like the @value{GDBN}
14914 @code{finish} command.
14917 Continue execution of your program, like the @value{GDBN} @code{continue}
14921 Go up the number of frames indicated by the numeric argument
14922 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
14923 like the @value{GDBN} @code{up} command.
14926 Go down the number of frames indicated by the numeric argument, like the
14927 @value{GDBN} @code{down} command.
14930 In any source file, the Emacs command @kbd{C-x SPC} (@code{gud-break})
14931 tells @value{GDBN} to set a breakpoint on the source line point is on.
14933 If you type @kbd{M-x speedbar}, then Emacs displays a separate frame which
14934 shows a backtrace when the @value{GDBN} I/O buffer is current. Move
14935 point to any frame in the stack and type @key{RET} to make it become the
14936 current frame and display the associated source in the source buffer.
14937 Alternatively, click @kbd{Mouse-2} to make the selected frame become the
14940 If you accidentally delete the source-display buffer, an easy way to get
14941 it back is to type the command @code{f} in the @value{GDBN} buffer, to
14942 request a frame display; when you run under Emacs, this recreates
14943 the source buffer if necessary to show you the context of the current
14946 The source files displayed in Emacs are in ordinary Emacs buffers
14947 which are visiting the source files in the usual way. You can edit
14948 the files with these buffers if you wish; but keep in mind that @value{GDBN}
14949 communicates with Emacs in terms of line numbers. If you add or
14950 delete lines from the text, the line numbers that @value{GDBN} knows cease
14951 to correspond properly with the code.
14953 The description given here is for GNU Emacs version 21.3 and a more
14954 detailed description of its interaction with @value{GDBN} is given in
14955 the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu} Emacs Manual}).
14957 @c The following dropped because Epoch is nonstandard. Reactivate
14958 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
14960 @kindex Emacs Epoch environment
14964 Version 18 of @sc{gnu} Emacs has a built-in window system
14965 called the @code{epoch}
14966 environment. Users of this environment can use a new command,
14967 @code{inspect} which performs identically to @code{print} except that
14968 each value is printed in its own window.
14973 @chapter The @sc{gdb/mi} Interface
14975 @unnumberedsec Function and Purpose
14977 @cindex @sc{gdb/mi}, its purpose
14978 @sc{gdb/mi} is a line based machine oriented text interface to @value{GDBN}. It is
14979 specifically intended to support the development of systems which use
14980 the debugger as just one small component of a larger system.
14982 This chapter is a specification of the @sc{gdb/mi} interface. It is written
14983 in the form of a reference manual.
14985 Note that @sc{gdb/mi} is still under construction, so some of the
14986 features described below are incomplete and subject to change.
14988 @unnumberedsec Notation and Terminology
14990 @cindex notational conventions, for @sc{gdb/mi}
14991 This chapter uses the following notation:
14995 @code{|} separates two alternatives.
14998 @code{[ @var{something} ]} indicates that @var{something} is optional:
14999 it may or may not be given.
15002 @code{( @var{group} )*} means that @var{group} inside the parentheses
15003 may repeat zero or more times.
15006 @code{( @var{group} )+} means that @var{group} inside the parentheses
15007 may repeat one or more times.
15010 @code{"@var{string}"} means a literal @var{string}.
15014 @heading Dependencies
15017 @heading Acknowledgments
15019 In alphabetic order: Andrew Cagney, Fernando Nasser, Stan Shebs and
15023 * GDB/MI Command Syntax::
15024 * GDB/MI Compatibility with CLI::
15025 * GDB/MI Output Records::
15026 * GDB/MI Command Description Format::
15027 * GDB/MI Breakpoint Table Commands::
15028 * GDB/MI Data Manipulation::
15029 * GDB/MI Program Control::
15030 * GDB/MI Miscellaneous Commands::
15032 * GDB/MI Kod Commands::
15033 * GDB/MI Memory Overlay Commands::
15034 * GDB/MI Signal Handling Commands::
15036 * GDB/MI Stack Manipulation::
15037 * GDB/MI Symbol Query::
15038 * GDB/MI Target Manipulation::
15039 * GDB/MI Thread Commands::
15040 * GDB/MI Tracepoint Commands::
15041 * GDB/MI Variable Objects::
15044 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15045 @node GDB/MI Command Syntax
15046 @section @sc{gdb/mi} Command Syntax
15049 * GDB/MI Input Syntax::
15050 * GDB/MI Output Syntax::
15051 * GDB/MI Simple Examples::
15054 @node GDB/MI Input Syntax
15055 @subsection @sc{gdb/mi} Input Syntax
15057 @cindex input syntax for @sc{gdb/mi}
15058 @cindex @sc{gdb/mi}, input syntax
15060 @item @var{command} @expansion{}
15061 @code{@var{cli-command} | @var{mi-command}}
15063 @item @var{cli-command} @expansion{}
15064 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
15065 @var{cli-command} is any existing @value{GDBN} CLI command.
15067 @item @var{mi-command} @expansion{}
15068 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
15069 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
15071 @item @var{token} @expansion{}
15072 "any sequence of digits"
15074 @item @var{option} @expansion{}
15075 @code{"-" @var{parameter} [ " " @var{parameter} ]}
15077 @item @var{parameter} @expansion{}
15078 @code{@var{non-blank-sequence} | @var{c-string}}
15080 @item @var{operation} @expansion{}
15081 @emph{any of the operations described in this chapter}
15083 @item @var{non-blank-sequence} @expansion{}
15084 @emph{anything, provided it doesn't contain special characters such as
15085 "-", @var{nl}, """ and of course " "}
15087 @item @var{c-string} @expansion{}
15088 @code{""" @var{seven-bit-iso-c-string-content} """}
15090 @item @var{nl} @expansion{}
15099 The CLI commands are still handled by the @sc{mi} interpreter; their
15100 output is described below.
15103 The @code{@var{token}}, when present, is passed back when the command
15107 Some @sc{mi} commands accept optional arguments as part of the parameter
15108 list. Each option is identified by a leading @samp{-} (dash) and may be
15109 followed by an optional argument parameter. Options occur first in the
15110 parameter list and can be delimited from normal parameters using
15111 @samp{--} (this is useful when some parameters begin with a dash).
15118 We want easy access to the existing CLI syntax (for debugging).
15121 We want it to be easy to spot a @sc{mi} operation.
15124 @node GDB/MI Output Syntax
15125 @subsection @sc{gdb/mi} Output Syntax
15127 @cindex output syntax of @sc{gdb/mi}
15128 @cindex @sc{gdb/mi}, output syntax
15129 The output from @sc{gdb/mi} consists of zero or more out-of-band records
15130 followed, optionally, by a single result record. This result record
15131 is for the most recent command. The sequence of output records is
15132 terminated by @samp{(@value{GDBP})}.
15134 If an input command was prefixed with a @code{@var{token}} then the
15135 corresponding output for that command will also be prefixed by that same
15139 @item @var{output} @expansion{}
15140 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(@value{GDBP})" @var{nl}}
15142 @item @var{result-record} @expansion{}
15143 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
15145 @item @var{out-of-band-record} @expansion{}
15146 @code{@var{async-record} | @var{stream-record}}
15148 @item @var{async-record} @expansion{}
15149 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
15151 @item @var{exec-async-output} @expansion{}
15152 @code{[ @var{token} ] "*" @var{async-output}}
15154 @item @var{status-async-output} @expansion{}
15155 @code{[ @var{token} ] "+" @var{async-output}}
15157 @item @var{notify-async-output} @expansion{}
15158 @code{[ @var{token} ] "=" @var{async-output}}
15160 @item @var{async-output} @expansion{}
15161 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
15163 @item @var{result-class} @expansion{}
15164 @code{"done" | "running" | "connected" | "error" | "exit"}
15166 @item @var{async-class} @expansion{}
15167 @code{"stopped" | @var{others}} (where @var{others} will be added
15168 depending on the needs---this is still in development).
15170 @item @var{result} @expansion{}
15171 @code{ @var{variable} "=" @var{value}}
15173 @item @var{variable} @expansion{}
15174 @code{ @var{string} }
15176 @item @var{value} @expansion{}
15177 @code{ @var{const} | @var{tuple} | @var{list} }
15179 @item @var{const} @expansion{}
15180 @code{@var{c-string}}
15182 @item @var{tuple} @expansion{}
15183 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
15185 @item @var{list} @expansion{}
15186 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
15187 @var{result} ( "," @var{result} )* "]" }
15189 @item @var{stream-record} @expansion{}
15190 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
15192 @item @var{console-stream-output} @expansion{}
15193 @code{"~" @var{c-string}}
15195 @item @var{target-stream-output} @expansion{}
15196 @code{"@@" @var{c-string}}
15198 @item @var{log-stream-output} @expansion{}
15199 @code{"&" @var{c-string}}
15201 @item @var{nl} @expansion{}
15204 @item @var{token} @expansion{}
15205 @emph{any sequence of digits}.
15213 All output sequences end in a single line containing a period.
15216 The @code{@var{token}} is from the corresponding request. If an execution
15217 command is interrupted by the @samp{-exec-interrupt} command, the
15218 @var{token} associated with the @samp{*stopped} message is the one of the
15219 original execution command, not the one of the interrupt command.
15222 @cindex status output in @sc{gdb/mi}
15223 @var{status-async-output} contains on-going status information about the
15224 progress of a slow operation. It can be discarded. All status output is
15225 prefixed by @samp{+}.
15228 @cindex async output in @sc{gdb/mi}
15229 @var{exec-async-output} contains asynchronous state change on the target
15230 (stopped, started, disappeared). All async output is prefixed by
15234 @cindex notify output in @sc{gdb/mi}
15235 @var{notify-async-output} contains supplementary information that the
15236 client should handle (e.g., a new breakpoint information). All notify
15237 output is prefixed by @samp{=}.
15240 @cindex console output in @sc{gdb/mi}
15241 @var{console-stream-output} is output that should be displayed as is in the
15242 console. It is the textual response to a CLI command. All the console
15243 output is prefixed by @samp{~}.
15246 @cindex target output in @sc{gdb/mi}
15247 @var{target-stream-output} is the output produced by the target program.
15248 All the target output is prefixed by @samp{@@}.
15251 @cindex log output in @sc{gdb/mi}
15252 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
15253 instance messages that should be displayed as part of an error log. All
15254 the log output is prefixed by @samp{&}.
15257 @cindex list output in @sc{gdb/mi}
15258 New @sc{gdb/mi} commands should only output @var{lists} containing
15264 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
15265 details about the various output records.
15267 @node GDB/MI Simple Examples
15268 @subsection Simple Examples of @sc{gdb/mi} Interaction
15269 @cindex @sc{gdb/mi}, simple examples
15271 This subsection presents several simple examples of interaction using
15272 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
15273 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
15274 the output received from @sc{gdb/mi}.
15276 @subsubheading Target Stop
15277 @c Ummm... There is no "-stop" command. This assumes async, no?
15278 Here's an example of stopping the inferior process:
15289 <- *stop,reason="stop",address="0x123",source="a.c:123"
15293 @subsubheading Simple CLI Command
15295 Here's an example of a simple CLI command being passed through
15296 @sc{gdb/mi} and on to the CLI.
15306 @subsubheading Command With Side Effects
15309 -> -symbol-file xyz.exe
15310 <- *breakpoint,nr="3",address="0x123",source="a.c:123"
15314 @subsubheading A Bad Command
15316 Here's what happens if you pass a non-existent command:
15320 <- ^error,msg="Undefined MI command: rubbish"
15324 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15325 @node GDB/MI Compatibility with CLI
15326 @section @sc{gdb/mi} Compatibility with CLI
15328 @cindex compatibility, @sc{gdb/mi} and CLI
15329 @cindex @sc{gdb/mi}, compatibility with CLI
15330 To help users familiar with @value{GDBN}'s existing CLI interface, @sc{gdb/mi}
15331 accepts existing CLI commands. As specified by the syntax, such
15332 commands can be directly entered into the @sc{gdb/mi} interface and @value{GDBN} will
15335 This mechanism is provided as an aid to developers of @sc{gdb/mi}
15336 clients and not as a reliable interface into the CLI. Since the command
15337 is being interpreteted in an environment that assumes @sc{gdb/mi}
15338 behaviour, the exact output of such commands is likely to end up being
15339 an un-supported hybrid of @sc{gdb/mi} and CLI output.
15341 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15342 @node GDB/MI Output Records
15343 @section @sc{gdb/mi} Output Records
15346 * GDB/MI Result Records::
15347 * GDB/MI Stream Records::
15348 * GDB/MI Out-of-band Records::
15351 @node GDB/MI Result Records
15352 @subsection @sc{gdb/mi} Result Records
15354 @cindex result records in @sc{gdb/mi}
15355 @cindex @sc{gdb/mi}, result records
15356 In addition to a number of out-of-band notifications, the response to a
15357 @sc{gdb/mi} command includes one of the following result indications:
15361 @item "^done" [ "," @var{results} ]
15362 The synchronous operation was successful, @code{@var{results}} are the return
15367 @c Is this one correct? Should it be an out-of-band notification?
15368 The asynchronous operation was successfully started. The target is
15371 @item "^error" "," @var{c-string}
15373 The operation failed. The @code{@var{c-string}} contains the corresponding
15377 @node GDB/MI Stream Records
15378 @subsection @sc{gdb/mi} Stream Records
15380 @cindex @sc{gdb/mi}, stream records
15381 @cindex stream records in @sc{gdb/mi}
15382 @value{GDBN} internally maintains a number of output streams: the console, the
15383 target, and the log. The output intended for each of these streams is
15384 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
15386 Each stream record begins with a unique @dfn{prefix character} which
15387 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
15388 Syntax}). In addition to the prefix, each stream record contains a
15389 @code{@var{string-output}}. This is either raw text (with an implicit new
15390 line) or a quoted C string (which does not contain an implicit newline).
15393 @item "~" @var{string-output}
15394 The console output stream contains text that should be displayed in the
15395 CLI console window. It contains the textual responses to CLI commands.
15397 @item "@@" @var{string-output}
15398 The target output stream contains any textual output from the running
15401 @item "&" @var{string-output}
15402 The log stream contains debugging messages being produced by @value{GDBN}'s
15406 @node GDB/MI Out-of-band Records
15407 @subsection @sc{gdb/mi} Out-of-band Records
15409 @cindex out-of-band records in @sc{gdb/mi}
15410 @cindex @sc{gdb/mi}, out-of-band records
15411 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
15412 additional changes that have occurred. Those changes can either be a
15413 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
15414 target activity (e.g., target stopped).
15416 The following is a preliminary list of possible out-of-band records.
15423 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15424 @node GDB/MI Command Description Format
15425 @section @sc{gdb/mi} Command Description Format
15427 The remaining sections describe blocks of commands. Each block of
15428 commands is laid out in a fashion similar to this section.
15430 Note the the line breaks shown in the examples are here only for
15431 readability. They don't appear in the real output.
15432 Also note that the commands with a non-available example (N.A.@:) are
15433 not yet implemented.
15435 @subheading Motivation
15437 The motivation for this collection of commands.
15439 @subheading Introduction
15441 A brief introduction to this collection of commands as a whole.
15443 @subheading Commands
15445 For each command in the block, the following is described:
15447 @subsubheading Synopsis
15450 -command @var{args}@dots{}
15453 @subsubheading @value{GDBN} Command
15455 The corresponding @value{GDBN} CLI command.
15457 @subsubheading Result
15459 @subsubheading Out-of-band
15461 @subsubheading Notes
15463 @subsubheading Example
15466 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15467 @node GDB/MI Breakpoint Table Commands
15468 @section @sc{gdb/mi} Breakpoint table commands
15470 @cindex breakpoint commands for @sc{gdb/mi}
15471 @cindex @sc{gdb/mi}, breakpoint commands
15472 This section documents @sc{gdb/mi} commands for manipulating
15475 @subheading The @code{-break-after} Command
15476 @findex -break-after
15478 @subsubheading Synopsis
15481 -break-after @var{number} @var{count}
15484 The breakpoint number @var{number} is not in effect until it has been
15485 hit @var{count} times. To see how this is reflected in the output of
15486 the @samp{-break-list} command, see the description of the
15487 @samp{-break-list} command below.
15489 @subsubheading @value{GDBN} Command
15491 The corresponding @value{GDBN} command is @samp{ignore}.
15493 @subsubheading Example
15498 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",line="5"@}
15505 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15506 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15507 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15508 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15509 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15510 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15511 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15512 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15513 addr="0x000100d0",func="main",file="hello.c",line="5",times="0",
15519 @subheading The @code{-break-catch} Command
15520 @findex -break-catch
15522 @subheading The @code{-break-commands} Command
15523 @findex -break-commands
15527 @subheading The @code{-break-condition} Command
15528 @findex -break-condition
15530 @subsubheading Synopsis
15533 -break-condition @var{number} @var{expr}
15536 Breakpoint @var{number} will stop the program only if the condition in
15537 @var{expr} is true. The condition becomes part of the
15538 @samp{-break-list} output (see the description of the @samp{-break-list}
15541 @subsubheading @value{GDBN} Command
15543 The corresponding @value{GDBN} command is @samp{condition}.
15545 @subsubheading Example
15549 -break-condition 1 1
15553 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15554 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15555 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15556 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15557 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15558 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15559 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15560 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15561 addr="0x000100d0",func="main",file="hello.c",line="5",cond="1",
15562 times="0",ignore="3"@}]@}
15566 @subheading The @code{-break-delete} Command
15567 @findex -break-delete
15569 @subsubheading Synopsis
15572 -break-delete ( @var{breakpoint} )+
15575 Delete the breakpoint(s) whose number(s) are specified in the argument
15576 list. This is obviously reflected in the breakpoint list.
15578 @subsubheading @value{GDBN} command
15580 The corresponding @value{GDBN} command is @samp{delete}.
15582 @subsubheading Example
15590 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
15591 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15592 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15593 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15594 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15595 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15596 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15601 @subheading The @code{-break-disable} Command
15602 @findex -break-disable
15604 @subsubheading Synopsis
15607 -break-disable ( @var{breakpoint} )+
15610 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
15611 break list is now set to @samp{n} for the named @var{breakpoint}(s).
15613 @subsubheading @value{GDBN} Command
15615 The corresponding @value{GDBN} command is @samp{disable}.
15617 @subsubheading Example
15625 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15626 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15627 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15628 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15629 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15630 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15631 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15632 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
15633 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
15637 @subheading The @code{-break-enable} Command
15638 @findex -break-enable
15640 @subsubheading Synopsis
15643 -break-enable ( @var{breakpoint} )+
15646 Enable (previously disabled) @var{breakpoint}(s).
15648 @subsubheading @value{GDBN} Command
15650 The corresponding @value{GDBN} command is @samp{enable}.
15652 @subsubheading Example
15660 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15661 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15662 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15663 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15664 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15665 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15666 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15667 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
15668 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
15672 @subheading The @code{-break-info} Command
15673 @findex -break-info
15675 @subsubheading Synopsis
15678 -break-info @var{breakpoint}
15682 Get information about a single breakpoint.
15684 @subsubheading @value{GDBN} command
15686 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
15688 @subsubheading Example
15691 @subheading The @code{-break-insert} Command
15692 @findex -break-insert
15694 @subsubheading Synopsis
15697 -break-insert [ -t ] [ -h ] [ -r ]
15698 [ -c @var{condition} ] [ -i @var{ignore-count} ]
15699 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
15703 If specified, @var{line}, can be one of:
15710 @item filename:linenum
15711 @item filename:function
15715 The possible optional parameters of this command are:
15719 Insert a tempoary breakpoint.
15721 Insert a hardware breakpoint.
15722 @item -c @var{condition}
15723 Make the breakpoint conditional on @var{condition}.
15724 @item -i @var{ignore-count}
15725 Initialize the @var{ignore-count}.
15727 Insert a regular breakpoint in all the functions whose names match the
15728 given regular expression. Other flags are not applicable to regular
15732 @subsubheading Result
15734 The result is in the form:
15737 ^done,bkptno="@var{number}",func="@var{funcname}",
15738 file="@var{filename}",line="@var{lineno}"
15742 where @var{number} is the @value{GDBN} number for this breakpoint, @var{funcname}
15743 is the name of the function where the breakpoint was inserted,
15744 @var{filename} is the name of the source file which contains this
15745 function, and @var{lineno} is the source line number within that file.
15747 Note: this format is open to change.
15748 @c An out-of-band breakpoint instead of part of the result?
15750 @subsubheading @value{GDBN} Command
15752 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
15753 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
15755 @subsubheading Example
15760 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
15762 -break-insert -t foo
15763 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",line="11"@}
15766 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15767 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15768 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15769 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15770 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15771 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15772 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15773 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15774 addr="0x0001072c", func="main",file="recursive2.c",line="4",times="0"@},
15775 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
15776 addr="0x00010774",func="foo",file="recursive2.c",line="11",times="0"@}]@}
15778 -break-insert -r foo.*
15779 ~int foo(int, int);
15780 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c",line="11"@}
15784 @subheading The @code{-break-list} Command
15785 @findex -break-list
15787 @subsubheading Synopsis
15793 Displays the list of inserted breakpoints, showing the following fields:
15797 number of the breakpoint
15799 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
15801 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
15804 is the breakpoint enabled or no: @samp{y} or @samp{n}
15806 memory location at which the breakpoint is set
15808 logical location of the breakpoint, expressed by function name, file
15811 number of times the breakpoint has been hit
15814 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
15815 @code{body} field is an empty list.
15817 @subsubheading @value{GDBN} Command
15819 The corresponding @value{GDBN} command is @samp{info break}.
15821 @subsubheading Example
15826 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15827 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15828 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15829 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15830 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15831 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15832 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15833 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15834 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
15835 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
15836 addr="0x00010114",func="foo",file="hello.c",line="13",times="0"@}]@}
15840 Here's an example of the result when there are no breakpoints:
15845 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
15846 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15847 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15848 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15849 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15850 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15851 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15856 @subheading The @code{-break-watch} Command
15857 @findex -break-watch
15859 @subsubheading Synopsis
15862 -break-watch [ -a | -r ]
15865 Create a watchpoint. With the @samp{-a} option it will create an
15866 @dfn{access} watchpoint, i.e. a watchpoint that triggers either on a
15867 read from or on a write to the memory location. With the @samp{-r}
15868 option, the watchpoint created is a @dfn{read} watchpoint, i.e. it will
15869 trigger only when the memory location is accessed for reading. Without
15870 either of the options, the watchpoint created is a regular watchpoint,
15871 i.e. it will trigger when the memory location is accessed for writing.
15872 @xref{Set Watchpoints, , Setting watchpoints}.
15874 Note that @samp{-break-list} will report a single list of watchpoints and
15875 breakpoints inserted.
15877 @subsubheading @value{GDBN} Command
15879 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
15882 @subsubheading Example
15884 Setting a watchpoint on a variable in the @code{main} function:
15889 ^done,wpt=@{number="2",exp="x"@}
15893 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
15894 value=@{old="-268439212",new="55"@},
15895 frame=@{func="main",args=[],file="recursive2.c",line="5"@}
15899 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
15900 the program execution twice: first for the variable changing value, then
15901 for the watchpoint going out of scope.
15906 ^done,wpt=@{number="5",exp="C"@}
15910 ^done,reason="watchpoint-trigger",
15911 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
15912 frame=@{func="callee4",args=[],
15913 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
15917 ^done,reason="watchpoint-scope",wpnum="5",
15918 frame=@{func="callee3",args=[@{name="strarg",
15919 value="0x11940 \"A string argument.\""@}],
15920 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
15924 Listing breakpoints and watchpoints, at different points in the program
15925 execution. Note that once the watchpoint goes out of scope, it is
15931 ^done,wpt=@{number="2",exp="C"@}
15934 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15935 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15936 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15937 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15938 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15939 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15940 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15941 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15942 addr="0x00010734",func="callee4",
15943 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
15944 bkpt=@{number="2",type="watchpoint",disp="keep",
15945 enabled="y",addr="",what="C",times="0"@}]@}
15949 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
15950 value=@{old="-276895068",new="3"@},
15951 frame=@{func="callee4",args=[],
15952 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
15955 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15956 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15957 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15958 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15959 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15960 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15961 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15962 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15963 addr="0x00010734",func="callee4",
15964 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
15965 bkpt=@{number="2",type="watchpoint",disp="keep",
15966 enabled="y",addr="",what="C",times="-5"@}]@}
15970 ^done,reason="watchpoint-scope",wpnum="2",
15971 frame=@{func="callee3",args=[@{name="strarg",
15972 value="0x11940 \"A string argument.\""@}],
15973 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
15976 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15977 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15978 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15979 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15980 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15981 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15982 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15983 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15984 addr="0x00010734",func="callee4",
15985 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@}]@}
15989 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15990 @node GDB/MI Data Manipulation
15991 @section @sc{gdb/mi} Data Manipulation
15993 @cindex data manipulation, in @sc{gdb/mi}
15994 @cindex @sc{gdb/mi}, data manipulation
15995 This section describes the @sc{gdb/mi} commands that manipulate data:
15996 examine memory and registers, evaluate expressions, etc.
15998 @c REMOVED FROM THE INTERFACE.
15999 @c @subheading -data-assign
16000 @c Change the value of a program variable. Plenty of side effects.
16001 @c @subsubheading GDB command
16003 @c @subsubheading Example
16006 @subheading The @code{-data-disassemble} Command
16007 @findex -data-disassemble
16009 @subsubheading Synopsis
16013 [ -s @var{start-addr} -e @var{end-addr} ]
16014 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
16022 @item @var{start-addr}
16023 is the beginning address (or @code{$pc})
16024 @item @var{end-addr}
16026 @item @var{filename}
16027 is the name of the file to disassemble
16028 @item @var{linenum}
16029 is the line number to disassemble around
16031 is the the number of disassembly lines to be produced. If it is -1,
16032 the whole function will be disassembled, in case no @var{end-addr} is
16033 specified. If @var{end-addr} is specified as a non-zero value, and
16034 @var{lines} is lower than the number of disassembly lines between
16035 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
16036 displayed; if @var{lines} is higher than the number of lines between
16037 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
16040 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
16044 @subsubheading Result
16046 The output for each instruction is composed of four fields:
16055 Note that whatever included in the instruction field, is not manipulated
16056 directely by @sc{gdb/mi}, i.e. it is not possible to adjust its format.
16058 @subsubheading @value{GDBN} Command
16060 There's no direct mapping from this command to the CLI.
16062 @subsubheading Example
16064 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
16068 -data-disassemble -s $pc -e "$pc + 20" -- 0
16071 @{address="0x000107c0",func-name="main",offset="4",
16072 inst="mov 2, %o0"@},
16073 @{address="0x000107c4",func-name="main",offset="8",
16074 inst="sethi %hi(0x11800), %o2"@},
16075 @{address="0x000107c8",func-name="main",offset="12",
16076 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
16077 @{address="0x000107cc",func-name="main",offset="16",
16078 inst="sethi %hi(0x11800), %o2"@},
16079 @{address="0x000107d0",func-name="main",offset="20",
16080 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
16084 Disassemble the whole @code{main} function. Line 32 is part of
16088 -data-disassemble -f basics.c -l 32 -- 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"@},
16097 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
16098 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
16102 Disassemble 3 instructions from the start of @code{main}:
16106 -data-disassemble -f basics.c -l 32 -n 3 -- 0
16108 @{address="0x000107bc",func-name="main",offset="0",
16109 inst="save %sp, -112, %sp"@},
16110 @{address="0x000107c0",func-name="main",offset="4",
16111 inst="mov 2, %o0"@},
16112 @{address="0x000107c4",func-name="main",offset="8",
16113 inst="sethi %hi(0x11800), %o2"@}]
16117 Disassemble 3 instructions from the start of @code{main} in mixed mode:
16121 -data-disassemble -f basics.c -l 32 -n 3 -- 1
16123 src_and_asm_line=@{line="31",
16124 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
16125 testsuite/gdb.mi/basics.c",line_asm_insn=[
16126 @{address="0x000107bc",func-name="main",offset="0",
16127 inst="save %sp, -112, %sp"@}]@},
16128 src_and_asm_line=@{line="32",
16129 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
16130 testsuite/gdb.mi/basics.c",line_asm_insn=[
16131 @{address="0x000107c0",func-name="main",offset="4",
16132 inst="mov 2, %o0"@},
16133 @{address="0x000107c4",func-name="main",offset="8",
16134 inst="sethi %hi(0x11800), %o2"@}]@}]
16139 @subheading The @code{-data-evaluate-expression} Command
16140 @findex -data-evaluate-expression
16142 @subsubheading Synopsis
16145 -data-evaluate-expression @var{expr}
16148 Evaluate @var{expr} as an expression. The expression could contain an
16149 inferior function call. The function call will execute synchronously.
16150 If the expression contains spaces, it must be enclosed in double quotes.
16152 @subsubheading @value{GDBN} Command
16154 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
16155 @samp{call}. In @code{gdbtk} only, there's a corresponding
16156 @samp{gdb_eval} command.
16158 @subsubheading Example
16160 In the following example, the numbers that precede the commands are the
16161 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
16162 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
16166 211-data-evaluate-expression A
16169 311-data-evaluate-expression &A
16170 311^done,value="0xefffeb7c"
16172 411-data-evaluate-expression A+3
16175 511-data-evaluate-expression "A + 3"
16181 @subheading The @code{-data-list-changed-registers} Command
16182 @findex -data-list-changed-registers
16184 @subsubheading Synopsis
16187 -data-list-changed-registers
16190 Display a list of the registers that have changed.
16192 @subsubheading @value{GDBN} Command
16194 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
16195 has the corresponding command @samp{gdb_changed_register_list}.
16197 @subsubheading Example
16199 On a PPC MBX board:
16207 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
16208 args=[],file="try.c",line="5"@}
16210 -data-list-changed-registers
16211 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
16212 "10","11","13","14","15","16","17","18","19","20","21","22","23",
16213 "24","25","26","27","28","30","31","64","65","66","67","69"]
16218 @subheading The @code{-data-list-register-names} Command
16219 @findex -data-list-register-names
16221 @subsubheading Synopsis
16224 -data-list-register-names [ ( @var{regno} )+ ]
16227 Show a list of register names for the current target. If no arguments
16228 are given, it shows a list of the names of all the registers. If
16229 integer numbers are given as arguments, it will print a list of the
16230 names of the registers corresponding to the arguments. To ensure
16231 consistency between a register name and its number, the output list may
16232 include empty register names.
16234 @subsubheading @value{GDBN} Command
16236 @value{GDBN} does not have a command which corresponds to
16237 @samp{-data-list-register-names}. In @code{gdbtk} there is a
16238 corresponding command @samp{gdb_regnames}.
16240 @subsubheading Example
16242 For the PPC MBX board:
16245 -data-list-register-names
16246 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
16247 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
16248 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
16249 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
16250 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
16251 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
16252 "", "pc","ps","cr","lr","ctr","xer"]
16254 -data-list-register-names 1 2 3
16255 ^done,register-names=["r1","r2","r3"]
16259 @subheading The @code{-data-list-register-values} Command
16260 @findex -data-list-register-values
16262 @subsubheading Synopsis
16265 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
16268 Display the registers' contents. @var{fmt} is the format according to
16269 which the registers' contents are to be returned, followed by an optional
16270 list of numbers specifying the registers to display. A missing list of
16271 numbers indicates that the contents of all the registers must be returned.
16273 Allowed formats for @var{fmt} are:
16290 @subsubheading @value{GDBN} Command
16292 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
16293 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
16295 @subsubheading Example
16297 For a PPC MBX board (note: line breaks are for readability only, they
16298 don't appear in the actual output):
16302 -data-list-register-values r 64 65
16303 ^done,register-values=[@{number="64",value="0xfe00a300"@},
16304 @{number="65",value="0x00029002"@}]
16306 -data-list-register-values x
16307 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
16308 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
16309 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
16310 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
16311 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
16312 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
16313 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
16314 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
16315 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
16316 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
16317 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
16318 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
16319 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
16320 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
16321 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
16322 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
16323 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
16324 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
16325 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
16326 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
16327 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
16328 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
16329 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
16330 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
16331 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
16332 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
16333 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
16334 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
16335 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
16336 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
16337 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
16338 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
16339 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
16340 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
16341 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
16342 @{number="69",value="0x20002b03"@}]
16347 @subheading The @code{-data-read-memory} Command
16348 @findex -data-read-memory
16350 @subsubheading Synopsis
16353 -data-read-memory [ -o @var{byte-offset} ]
16354 @var{address} @var{word-format} @var{word-size}
16355 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
16362 @item @var{address}
16363 An expression specifying the address of the first memory word to be
16364 read. Complex expressions containing embedded white space should be
16365 quoted using the C convention.
16367 @item @var{word-format}
16368 The format to be used to print the memory words. The notation is the
16369 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
16372 @item @var{word-size}
16373 The size of each memory word in bytes.
16375 @item @var{nr-rows}
16376 The number of rows in the output table.
16378 @item @var{nr-cols}
16379 The number of columns in the output table.
16382 If present, indicates that each row should include an @sc{ascii} dump. The
16383 value of @var{aschar} is used as a padding character when a byte is not a
16384 member of the printable @sc{ascii} character set (printable @sc{ascii}
16385 characters are those whose code is between 32 and 126, inclusively).
16387 @item @var{byte-offset}
16388 An offset to add to the @var{address} before fetching memory.
16391 This command displays memory contents as a table of @var{nr-rows} by
16392 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
16393 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
16394 (returned as @samp{total-bytes}). Should less than the requested number
16395 of bytes be returned by the target, the missing words are identified
16396 using @samp{N/A}. The number of bytes read from the target is returned
16397 in @samp{nr-bytes} and the starting address used to read memory in
16400 The address of the next/previous row or page is available in
16401 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
16404 @subsubheading @value{GDBN} Command
16406 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
16407 @samp{gdb_get_mem} memory read command.
16409 @subsubheading Example
16411 Read six bytes of memory starting at @code{bytes+6} but then offset by
16412 @code{-6} bytes. Format as three rows of two columns. One byte per
16413 word. Display each word in hex.
16417 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
16418 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
16419 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
16420 prev-page="0x0000138a",memory=[
16421 @{addr="0x00001390",data=["0x00","0x01"]@},
16422 @{addr="0x00001392",data=["0x02","0x03"]@},
16423 @{addr="0x00001394",data=["0x04","0x05"]@}]
16427 Read two bytes of memory starting at address @code{shorts + 64} and
16428 display as a single word formatted in decimal.
16432 5-data-read-memory shorts+64 d 2 1 1
16433 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
16434 next-row="0x00001512",prev-row="0x0000150e",
16435 next-page="0x00001512",prev-page="0x0000150e",memory=[
16436 @{addr="0x00001510",data=["128"]@}]
16440 Read thirty two bytes of memory starting at @code{bytes+16} and format
16441 as eight rows of four columns. Include a string encoding with @samp{x}
16442 used as the non-printable character.
16446 4-data-read-memory bytes+16 x 1 8 4 x
16447 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
16448 next-row="0x000013c0",prev-row="0x0000139c",
16449 next-page="0x000013c0",prev-page="0x00001380",memory=[
16450 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
16451 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
16452 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
16453 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
16454 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
16455 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
16456 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
16457 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
16461 @subheading The @code{-display-delete} Command
16462 @findex -display-delete
16464 @subsubheading Synopsis
16467 -display-delete @var{number}
16470 Delete the display @var{number}.
16472 @subsubheading @value{GDBN} Command
16474 The corresponding @value{GDBN} command is @samp{delete display}.
16476 @subsubheading Example
16480 @subheading The @code{-display-disable} Command
16481 @findex -display-disable
16483 @subsubheading Synopsis
16486 -display-disable @var{number}
16489 Disable display @var{number}.
16491 @subsubheading @value{GDBN} Command
16493 The corresponding @value{GDBN} command is @samp{disable display}.
16495 @subsubheading Example
16499 @subheading The @code{-display-enable} Command
16500 @findex -display-enable
16502 @subsubheading Synopsis
16505 -display-enable @var{number}
16508 Enable display @var{number}.
16510 @subsubheading @value{GDBN} Command
16512 The corresponding @value{GDBN} command is @samp{enable display}.
16514 @subsubheading Example
16518 @subheading The @code{-display-insert} Command
16519 @findex -display-insert
16521 @subsubheading Synopsis
16524 -display-insert @var{expression}
16527 Display @var{expression} every time the program stops.
16529 @subsubheading @value{GDBN} Command
16531 The corresponding @value{GDBN} command is @samp{display}.
16533 @subsubheading Example
16537 @subheading The @code{-display-list} Command
16538 @findex -display-list
16540 @subsubheading Synopsis
16546 List the displays. Do not show the current values.
16548 @subsubheading @value{GDBN} Command
16550 The corresponding @value{GDBN} command is @samp{info display}.
16552 @subsubheading Example
16556 @subheading The @code{-environment-cd} Command
16557 @findex -environment-cd
16559 @subsubheading Synopsis
16562 -environment-cd @var{pathdir}
16565 Set @value{GDBN}'s working directory.
16567 @subsubheading @value{GDBN} Command
16569 The corresponding @value{GDBN} command is @samp{cd}.
16571 @subsubheading Example
16575 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
16581 @subheading The @code{-environment-directory} Command
16582 @findex -environment-directory
16584 @subsubheading Synopsis
16587 -environment-directory [ -r ] [ @var{pathdir} ]+
16590 Add directories @var{pathdir} to beginning of search path for source files.
16591 If the @samp{-r} option is used, the search path is reset to the default
16592 search path. If directories @var{pathdir} are supplied in addition to the
16593 @samp{-r} option, the search path is first reset and then addition
16595 Multiple directories may be specified, separated by blanks. Specifying
16596 multiple directories in a single command
16597 results in the directories added to the beginning of the
16598 search path in the same order they were presented in the command.
16599 If blanks are needed as
16600 part of a directory name, double-quotes should be used around
16601 the name. In the command output, the path will show up separated
16602 by the system directory-separator character. The directory-seperator
16603 character must not be used
16604 in any directory name.
16605 If no directories are specified, the current search path is displayed.
16607 @subsubheading @value{GDBN} Command
16609 The corresponding @value{GDBN} command is @samp{dir}.
16611 @subsubheading Example
16615 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
16616 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
16618 -environment-directory ""
16619 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
16621 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
16622 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
16624 -environment-directory -r
16625 ^done,source-path="$cdir:$cwd"
16630 @subheading The @code{-environment-path} Command
16631 @findex -environment-path
16633 @subsubheading Synopsis
16636 -environment-path [ -r ] [ @var{pathdir} ]+
16639 Add directories @var{pathdir} to beginning of search path for object files.
16640 If the @samp{-r} option is used, the search path is reset to the original
16641 search path that existed at gdb start-up. If directories @var{pathdir} are
16642 supplied in addition to the
16643 @samp{-r} option, the search path is first reset and then addition
16645 Multiple directories may be specified, separated by blanks. Specifying
16646 multiple directories in a single command
16647 results in the directories added to the beginning of the
16648 search path in the same order they were presented in the command.
16649 If blanks are needed as
16650 part of a directory name, double-quotes should be used around
16651 the name. In the command output, the path will show up separated
16652 by the system directory-separator character. The directory-seperator
16653 character must not be used
16654 in any directory name.
16655 If no directories are specified, the current path is displayed.
16658 @subsubheading @value{GDBN} Command
16660 The corresponding @value{GDBN} command is @samp{path}.
16662 @subsubheading Example
16667 ^done,path="/usr/bin"
16669 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
16670 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
16672 -environment-path -r /usr/local/bin
16673 ^done,path="/usr/local/bin:/usr/bin"
16678 @subheading The @code{-environment-pwd} Command
16679 @findex -environment-pwd
16681 @subsubheading Synopsis
16687 Show the current working directory.
16689 @subsubheading @value{GDBN} command
16691 The corresponding @value{GDBN} command is @samp{pwd}.
16693 @subsubheading Example
16698 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
16702 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16703 @node GDB/MI Program Control
16704 @section @sc{gdb/mi} Program control
16706 @subsubheading Program termination
16708 As a result of execution, the inferior program can run to completion, if
16709 it doesn't encounter any breakpoints. In this case the output will
16710 include an exit code, if the program has exited exceptionally.
16712 @subsubheading Examples
16715 Program exited normally:
16723 *stopped,reason="exited-normally"
16728 Program exited exceptionally:
16736 *stopped,reason="exited",exit-code="01"
16740 Another way the program can terminate is if it receives a signal such as
16741 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
16745 *stopped,reason="exited-signalled",signal-name="SIGINT",
16746 signal-meaning="Interrupt"
16750 @subheading The @code{-exec-abort} Command
16751 @findex -exec-abort
16753 @subsubheading Synopsis
16759 Kill the inferior running program.
16761 @subsubheading @value{GDBN} Command
16763 The corresponding @value{GDBN} command is @samp{kill}.
16765 @subsubheading Example
16769 @subheading The @code{-exec-arguments} Command
16770 @findex -exec-arguments
16772 @subsubheading Synopsis
16775 -exec-arguments @var{args}
16778 Set the inferior program arguments, to be used in the next
16781 @subsubheading @value{GDBN} Command
16783 The corresponding @value{GDBN} command is @samp{set args}.
16785 @subsubheading Example
16788 Don't have one around.
16791 @subheading The @code{-exec-continue} Command
16792 @findex -exec-continue
16794 @subsubheading Synopsis
16800 Asynchronous command. Resumes the execution of the inferior program
16801 until a breakpoint is encountered, or until the inferior exits.
16803 @subsubheading @value{GDBN} Command
16805 The corresponding @value{GDBN} corresponding is @samp{continue}.
16807 @subsubheading Example
16814 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
16815 file="hello.c",line="13"@}
16820 @subheading The @code{-exec-finish} Command
16821 @findex -exec-finish
16823 @subsubheading Synopsis
16829 Asynchronous command. Resumes the execution of the inferior program
16830 until the current function is exited. Displays the results returned by
16833 @subsubheading @value{GDBN} Command
16835 The corresponding @value{GDBN} command is @samp{finish}.
16837 @subsubheading Example
16839 Function returning @code{void}.
16846 *stopped,reason="function-finished",frame=@{func="main",args=[],
16847 file="hello.c",line="7"@}
16851 Function returning other than @code{void}. The name of the internal
16852 @value{GDBN} variable storing the result is printed, together with the
16859 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
16860 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
16861 file="recursive2.c",line="14"@},
16862 gdb-result-var="$1",return-value="0"
16867 @subheading The @code{-exec-interrupt} Command
16868 @findex -exec-interrupt
16870 @subsubheading Synopsis
16876 Asynchronous command. Interrupts the background execution of the target.
16877 Note how the token associated with the stop message is the one for the
16878 execution command that has been interrupted. The token for the interrupt
16879 itself only appears in the @samp{^done} output. If the user is trying to
16880 interrupt a non-running program, an error message will be printed.
16882 @subsubheading @value{GDBN} Command
16884 The corresponding @value{GDBN} command is @samp{interrupt}.
16886 @subsubheading Example
16897 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
16898 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",line="13"@}
16903 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
16908 @subheading The @code{-exec-next} Command
16911 @subsubheading Synopsis
16917 Asynchronous command. Resumes execution of the inferior program, stopping
16918 when the beginning of the next source line is reached.
16920 @subsubheading @value{GDBN} Command
16922 The corresponding @value{GDBN} command is @samp{next}.
16924 @subsubheading Example
16930 *stopped,reason="end-stepping-range",line="8",file="hello.c"
16935 @subheading The @code{-exec-next-instruction} Command
16936 @findex -exec-next-instruction
16938 @subsubheading Synopsis
16941 -exec-next-instruction
16944 Asynchronous command. Executes one machine instruction. If the
16945 instruction is a function call continues until the function returns. If
16946 the program stops at an instruction in the middle of a source line, the
16947 address will be printed as well.
16949 @subsubheading @value{GDBN} Command
16951 The corresponding @value{GDBN} command is @samp{nexti}.
16953 @subsubheading Example
16957 -exec-next-instruction
16961 *stopped,reason="end-stepping-range",
16962 addr="0x000100d4",line="5",file="hello.c"
16967 @subheading The @code{-exec-return} Command
16968 @findex -exec-return
16970 @subsubheading Synopsis
16976 Makes current function return immediately. Doesn't execute the inferior.
16977 Displays the new current frame.
16979 @subsubheading @value{GDBN} Command
16981 The corresponding @value{GDBN} command is @samp{return}.
16983 @subsubheading Example
16987 200-break-insert callee4
16988 200^done,bkpt=@{number="1",addr="0x00010734",
16989 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
16994 000*stopped,reason="breakpoint-hit",bkptno="1",
16995 frame=@{func="callee4",args=[],
16996 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
17002 111^done,frame=@{level="0",func="callee3",
17003 args=[@{name="strarg",
17004 value="0x11940 \"A string argument.\""@}],
17005 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
17010 @subheading The @code{-exec-run} Command
17013 @subsubheading Synopsis
17019 Asynchronous command. Starts execution of the inferior from the
17020 beginning. The inferior executes until either a breakpoint is
17021 encountered or the program exits.
17023 @subsubheading @value{GDBN} Command
17025 The corresponding @value{GDBN} command is @samp{run}.
17027 @subsubheading Example
17032 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
17037 *stopped,reason="breakpoint-hit",bkptno="1",
17038 frame=@{func="main",args=[],file="recursive2.c",line="4"@}
17043 @subheading The @code{-exec-show-arguments} Command
17044 @findex -exec-show-arguments
17046 @subsubheading Synopsis
17049 -exec-show-arguments
17052 Print the arguments of the program.
17054 @subsubheading @value{GDBN} Command
17056 The corresponding @value{GDBN} command is @samp{show args}.
17058 @subsubheading Example
17061 @c @subheading -exec-signal
17063 @subheading The @code{-exec-step} Command
17066 @subsubheading Synopsis
17072 Asynchronous command. Resumes execution of the inferior program, stopping
17073 when the beginning of the next source line is reached, if the next
17074 source line is not a function call. If it is, stop at the first
17075 instruction of the called function.
17077 @subsubheading @value{GDBN} Command
17079 The corresponding @value{GDBN} command is @samp{step}.
17081 @subsubheading Example
17083 Stepping into a function:
17089 *stopped,reason="end-stepping-range",
17090 frame=@{func="foo",args=[@{name="a",value="10"@},
17091 @{name="b",value="0"@}],file="recursive2.c",line="11"@}
17101 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
17106 @subheading The @code{-exec-step-instruction} Command
17107 @findex -exec-step-instruction
17109 @subsubheading Synopsis
17112 -exec-step-instruction
17115 Asynchronous command. Resumes the inferior which executes one machine
17116 instruction. The output, once @value{GDBN} has stopped, will vary depending on
17117 whether we have stopped in the middle of a source line or not. In the
17118 former case, the address at which the program stopped will be printed as
17121 @subsubheading @value{GDBN} Command
17123 The corresponding @value{GDBN} command is @samp{stepi}.
17125 @subsubheading Example
17129 -exec-step-instruction
17133 *stopped,reason="end-stepping-range",
17134 frame=@{func="foo",args=[],file="try.c",line="10"@}
17136 -exec-step-instruction
17140 *stopped,reason="end-stepping-range",
17141 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",line="10"@}
17146 @subheading The @code{-exec-until} Command
17147 @findex -exec-until
17149 @subsubheading Synopsis
17152 -exec-until [ @var{location} ]
17155 Asynchronous command. Executes the inferior until the @var{location}
17156 specified in the argument is reached. If there is no argument, the inferior
17157 executes until a source line greater than the current one is reached.
17158 The reason for stopping in this case will be @samp{location-reached}.
17160 @subsubheading @value{GDBN} Command
17162 The corresponding @value{GDBN} command is @samp{until}.
17164 @subsubheading Example
17168 -exec-until recursive2.c:6
17172 *stopped,reason="location-reached",frame=@{func="main",args=[],
17173 file="recursive2.c",line="6"@}
17178 @subheading -file-clear
17179 Is this going away????
17183 @subheading The @code{-file-exec-and-symbols} Command
17184 @findex -file-exec-and-symbols
17186 @subsubheading Synopsis
17189 -file-exec-and-symbols @var{file}
17192 Specify the executable file to be debugged. This file is the one from
17193 which the symbol table is also read. If no file is specified, the
17194 command clears the executable and symbol information. If breakpoints
17195 are set when using this command with no arguments, @value{GDBN} will produce
17196 error messages. Otherwise, no output is produced, except a completion
17199 @subsubheading @value{GDBN} Command
17201 The corresponding @value{GDBN} command is @samp{file}.
17203 @subsubheading Example
17207 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
17213 @subheading The @code{-file-exec-file} Command
17214 @findex -file-exec-file
17216 @subsubheading Synopsis
17219 -file-exec-file @var{file}
17222 Specify the executable file to be debugged. Unlike
17223 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
17224 from this file. If used without argument, @value{GDBN} clears the information
17225 about the executable file. No output is produced, except a completion
17228 @subsubheading @value{GDBN} Command
17230 The corresponding @value{GDBN} command is @samp{exec-file}.
17232 @subsubheading Example
17236 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
17242 @subheading The @code{-file-list-exec-sections} Command
17243 @findex -file-list-exec-sections
17245 @subsubheading Synopsis
17248 -file-list-exec-sections
17251 List the sections of the current executable file.
17253 @subsubheading @value{GDBN} Command
17255 The @value{GDBN} command @samp{info file} shows, among the rest, the same
17256 information as this command. @code{gdbtk} has a corresponding command
17257 @samp{gdb_load_info}.
17259 @subsubheading Example
17263 @subheading The @code{-file-list-exec-source-file} Command
17264 @findex -file-list-exec-source-file
17266 @subsubheading Synopsis
17269 -file-list-exec-source-file
17272 List the line number, the current source file, and the absolute path
17273 to the current source file for the current executable.
17275 @subsubheading @value{GDBN} Command
17277 There's no @value{GDBN} command which directly corresponds to this one.
17279 @subsubheading Example
17283 123-file-list-exec-source-file
17284 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
17289 @subheading The @code{-file-list-exec-source-files} Command
17290 @findex -file-list-exec-source-files
17292 @subsubheading Synopsis
17295 -file-list-exec-source-files
17298 List the source files for the current executable.
17300 It will always output the filename, but only when GDB can find the absolute
17301 file name of a source file, will it output the fullname.
17303 @subsubheading @value{GDBN} Command
17305 There's no @value{GDBN} command which directly corresponds to this one.
17306 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
17308 @subsubheading Example
17311 -file-list-exec-source-files
17313 @{file=foo.c,fullname=/home/foo.c@},
17314 @{file=/home/bar.c,fullname=/home/bar.c@},
17315 @{file=gdb_could_not_find_fullpath.c@}]
17319 @subheading The @code{-file-list-shared-libraries} Command
17320 @findex -file-list-shared-libraries
17322 @subsubheading Synopsis
17325 -file-list-shared-libraries
17328 List the shared libraries in the program.
17330 @subsubheading @value{GDBN} Command
17332 The corresponding @value{GDBN} command is @samp{info shared}.
17334 @subsubheading Example
17338 @subheading The @code{-file-list-symbol-files} Command
17339 @findex -file-list-symbol-files
17341 @subsubheading Synopsis
17344 -file-list-symbol-files
17349 @subsubheading @value{GDBN} Command
17351 The corresponding @value{GDBN} command is @samp{info file} (part of it).
17353 @subsubheading Example
17357 @subheading The @code{-file-symbol-file} Command
17358 @findex -file-symbol-file
17360 @subsubheading Synopsis
17363 -file-symbol-file @var{file}
17366 Read symbol table info from the specified @var{file} argument. When
17367 used without arguments, clears @value{GDBN}'s symbol table info. No output is
17368 produced, except for a completion notification.
17370 @subsubheading @value{GDBN} Command
17372 The corresponding @value{GDBN} command is @samp{symbol-file}.
17374 @subsubheading Example
17378 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
17383 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17384 @node GDB/MI Miscellaneous Commands
17385 @section Miscellaneous @value{GDBN} commands in @sc{gdb/mi}
17387 @c @subheading -gdb-complete
17389 @subheading The @code{-gdb-exit} Command
17392 @subsubheading Synopsis
17398 Exit @value{GDBN} immediately.
17400 @subsubheading @value{GDBN} Command
17402 Approximately corresponds to @samp{quit}.
17404 @subsubheading Example
17411 @subheading The @code{-gdb-set} Command
17414 @subsubheading Synopsis
17420 Set an internal @value{GDBN} variable.
17421 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
17423 @subsubheading @value{GDBN} Command
17425 The corresponding @value{GDBN} command is @samp{set}.
17427 @subsubheading Example
17437 @subheading The @code{-gdb-show} Command
17440 @subsubheading Synopsis
17446 Show the current value of a @value{GDBN} variable.
17448 @subsubheading @value{GDBN} command
17450 The corresponding @value{GDBN} command is @samp{show}.
17452 @subsubheading Example
17461 @c @subheading -gdb-source
17464 @subheading The @code{-gdb-version} Command
17465 @findex -gdb-version
17467 @subsubheading Synopsis
17473 Show version information for @value{GDBN}. Used mostly in testing.
17475 @subsubheading @value{GDBN} Command
17477 There's no equivalent @value{GDBN} command. @value{GDBN} by default shows this
17478 information when you start an interactive session.
17480 @subsubheading Example
17482 @c This example modifies the actual output from GDB to avoid overfull
17488 ~Copyright 2000 Free Software Foundation, Inc.
17489 ~GDB is free software, covered by the GNU General Public License, and
17490 ~you are welcome to change it and/or distribute copies of it under
17491 ~ certain conditions.
17492 ~Type "show copying" to see the conditions.
17493 ~There is absolutely no warranty for GDB. Type "show warranty" for
17495 ~This GDB was configured as
17496 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
17501 @subheading The @code{-interpreter-exec} Command
17502 @findex -interpreter-exec
17504 @subheading Synopsis
17507 -interpreter-exec @var{interpreter} @var{command}
17510 Execute the specified @var{command} in the given @var{interpreter}.
17512 @subheading @value{GDBN} Command
17514 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
17516 @subheading Example
17520 -interpreter-exec console "break main"
17521 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
17522 &"During symbol reading, bad structure-type format.\n"
17523 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
17529 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17530 @node GDB/MI Kod Commands
17531 @section @sc{gdb/mi} Kod Commands
17533 The Kod commands are not implemented.
17535 @c @subheading -kod-info
17537 @c @subheading -kod-list
17539 @c @subheading -kod-list-object-types
17541 @c @subheading -kod-show
17543 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17544 @node GDB/MI Memory Overlay Commands
17545 @section @sc{gdb/mi} Memory Overlay Commands
17547 The memory overlay commands are not implemented.
17549 @c @subheading -overlay-auto
17551 @c @subheading -overlay-list-mapping-state
17553 @c @subheading -overlay-list-overlays
17555 @c @subheading -overlay-map
17557 @c @subheading -overlay-off
17559 @c @subheading -overlay-on
17561 @c @subheading -overlay-unmap
17563 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17564 @node GDB/MI Signal Handling Commands
17565 @section @sc{gdb/mi} Signal Handling Commands
17567 Signal handling commands are not implemented.
17569 @c @subheading -signal-handle
17571 @c @subheading -signal-list-handle-actions
17573 @c @subheading -signal-list-signal-types
17577 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17578 @node GDB/MI Stack Manipulation
17579 @section @sc{gdb/mi} Stack Manipulation Commands
17582 @subheading The @code{-stack-info-frame} Command
17583 @findex -stack-info-frame
17585 @subsubheading Synopsis
17591 Get info on the current frame.
17593 @subsubheading @value{GDBN} Command
17595 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
17596 (without arguments).
17598 @subsubheading Example
17601 @subheading The @code{-stack-info-depth} Command
17602 @findex -stack-info-depth
17604 @subsubheading Synopsis
17607 -stack-info-depth [ @var{max-depth} ]
17610 Return the depth of the stack. If the integer argument @var{max-depth}
17611 is specified, do not count beyond @var{max-depth} frames.
17613 @subsubheading @value{GDBN} Command
17615 There's no equivalent @value{GDBN} command.
17617 @subsubheading Example
17619 For a stack with frame levels 0 through 11:
17626 -stack-info-depth 4
17629 -stack-info-depth 12
17632 -stack-info-depth 11
17635 -stack-info-depth 13
17640 @subheading The @code{-stack-list-arguments} Command
17641 @findex -stack-list-arguments
17643 @subsubheading Synopsis
17646 -stack-list-arguments @var{show-values}
17647 [ @var{low-frame} @var{high-frame} ]
17650 Display a list of the arguments for the frames between @var{low-frame}
17651 and @var{high-frame} (inclusive). If @var{low-frame} and
17652 @var{high-frame} are not provided, list the arguments for the whole call
17655 The @var{show-values} argument must have a value of 0 or 1. A value of
17656 0 means that only the names of the arguments are listed, a value of 1
17657 means that both names and values of the arguments are printed.
17659 @subsubheading @value{GDBN} Command
17661 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
17662 @samp{gdb_get_args} command which partially overlaps with the
17663 functionality of @samp{-stack-list-arguments}.
17665 @subsubheading Example
17672 frame=@{level="0",addr="0x00010734",func="callee4",
17673 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
17674 frame=@{level="1",addr="0x0001076c",func="callee3",
17675 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
17676 frame=@{level="2",addr="0x0001078c",func="callee2",
17677 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
17678 frame=@{level="3",addr="0x000107b4",func="callee1",
17679 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
17680 frame=@{level="4",addr="0x000107e0",func="main",
17681 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
17683 -stack-list-arguments 0
17686 frame=@{level="0",args=[]@},
17687 frame=@{level="1",args=[name="strarg"]@},
17688 frame=@{level="2",args=[name="intarg",name="strarg"]@},
17689 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
17690 frame=@{level="4",args=[]@}]
17692 -stack-list-arguments 1
17695 frame=@{level="0",args=[]@},
17697 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
17698 frame=@{level="2",args=[
17699 @{name="intarg",value="2"@},
17700 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
17701 @{frame=@{level="3",args=[
17702 @{name="intarg",value="2"@},
17703 @{name="strarg",value="0x11940 \"A string argument.\""@},
17704 @{name="fltarg",value="3.5"@}]@},
17705 frame=@{level="4",args=[]@}]
17707 -stack-list-arguments 0 2 2
17708 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
17710 -stack-list-arguments 1 2 2
17711 ^done,stack-args=[frame=@{level="2",
17712 args=[@{name="intarg",value="2"@},
17713 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
17717 @c @subheading -stack-list-exception-handlers
17720 @subheading The @code{-stack-list-frames} Command
17721 @findex -stack-list-frames
17723 @subsubheading Synopsis
17726 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
17729 List the frames currently on the stack. For each frame it displays the
17734 The frame number, 0 being the topmost frame, i.e. the innermost function.
17736 The @code{$pc} value for that frame.
17740 File name of the source file where the function lives.
17742 Line number corresponding to the @code{$pc}.
17745 If invoked without arguments, this command prints a backtrace for the
17746 whole stack. If given two integer arguments, it shows the frames whose
17747 levels are between the two arguments (inclusive). If the two arguments
17748 are equal, it shows the single frame at the corresponding level.
17750 @subsubheading @value{GDBN} Command
17752 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
17754 @subsubheading Example
17756 Full stack backtrace:
17762 [frame=@{level="0",addr="0x0001076c",func="foo",
17763 file="recursive2.c",line="11"@},
17764 frame=@{level="1",addr="0x000107a4",func="foo",
17765 file="recursive2.c",line="14"@},
17766 frame=@{level="2",addr="0x000107a4",func="foo",
17767 file="recursive2.c",line="14"@},
17768 frame=@{level="3",addr="0x000107a4",func="foo",
17769 file="recursive2.c",line="14"@},
17770 frame=@{level="4",addr="0x000107a4",func="foo",
17771 file="recursive2.c",line="14"@},
17772 frame=@{level="5",addr="0x000107a4",func="foo",
17773 file="recursive2.c",line="14"@},
17774 frame=@{level="6",addr="0x000107a4",func="foo",
17775 file="recursive2.c",line="14"@},
17776 frame=@{level="7",addr="0x000107a4",func="foo",
17777 file="recursive2.c",line="14"@},
17778 frame=@{level="8",addr="0x000107a4",func="foo",
17779 file="recursive2.c",line="14"@},
17780 frame=@{level="9",addr="0x000107a4",func="foo",
17781 file="recursive2.c",line="14"@},
17782 frame=@{level="10",addr="0x000107a4",func="foo",
17783 file="recursive2.c",line="14"@},
17784 frame=@{level="11",addr="0x00010738",func="main",
17785 file="recursive2.c",line="4"@}]
17789 Show frames between @var{low_frame} and @var{high_frame}:
17793 -stack-list-frames 3 5
17795 [frame=@{level="3",addr="0x000107a4",func="foo",
17796 file="recursive2.c",line="14"@},
17797 frame=@{level="4",addr="0x000107a4",func="foo",
17798 file="recursive2.c",line="14"@},
17799 frame=@{level="5",addr="0x000107a4",func="foo",
17800 file="recursive2.c",line="14"@}]
17804 Show a single frame:
17808 -stack-list-frames 3 3
17810 [frame=@{level="3",addr="0x000107a4",func="foo",
17811 file="recursive2.c",line="14"@}]
17816 @subheading The @code{-stack-list-locals} Command
17817 @findex -stack-list-locals
17819 @subsubheading Synopsis
17822 -stack-list-locals @var{print-values}
17825 Display the local variable names for the current frame. With an
17826 argument of 0 or @code{--no-values}, prints only the names of the variables.
17827 With argument of 1 or @code{--all-values}, prints also their values. With
17828 argument of 2 or @code{--simple-values}, prints the name, type and value for
17829 simple data types and the name and type for arrays, structures and
17830 unions. In this last case, the idea is that the user can see the
17831 value of simple data types immediately and he can create variable
17832 objects for other data types if he wishes to explore their values in
17835 @subsubheading @value{GDBN} Command
17837 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
17839 @subsubheading Example
17843 -stack-list-locals 0
17844 ^done,locals=[name="A",name="B",name="C"]
17846 -stack-list-locals --all-values
17847 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
17848 @{name="C",value="@{1, 2, 3@}"@}]
17849 -stack-list-locals --simple-values
17850 ^done,locals=[@{name="A",type="int",value="1"@},
17851 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
17856 @subheading The @code{-stack-select-frame} Command
17857 @findex -stack-select-frame
17859 @subsubheading Synopsis
17862 -stack-select-frame @var{framenum}
17865 Change the current frame. Select a different frame @var{framenum} on
17868 @subsubheading @value{GDBN} Command
17870 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
17871 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
17873 @subsubheading Example
17877 -stack-select-frame 2
17882 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17883 @node GDB/MI Symbol Query
17884 @section @sc{gdb/mi} Symbol Query Commands
17887 @subheading The @code{-symbol-info-address} Command
17888 @findex -symbol-info-address
17890 @subsubheading Synopsis
17893 -symbol-info-address @var{symbol}
17896 Describe where @var{symbol} is stored.
17898 @subsubheading @value{GDBN} Command
17900 The corresponding @value{GDBN} command is @samp{info address}.
17902 @subsubheading Example
17906 @subheading The @code{-symbol-info-file} Command
17907 @findex -symbol-info-file
17909 @subsubheading Synopsis
17915 Show the file for the symbol.
17917 @subsubheading @value{GDBN} Command
17919 There's no equivalent @value{GDBN} command. @code{gdbtk} has
17920 @samp{gdb_find_file}.
17922 @subsubheading Example
17926 @subheading The @code{-symbol-info-function} Command
17927 @findex -symbol-info-function
17929 @subsubheading Synopsis
17932 -symbol-info-function
17935 Show which function the symbol lives in.
17937 @subsubheading @value{GDBN} Command
17939 @samp{gdb_get_function} in @code{gdbtk}.
17941 @subsubheading Example
17945 @subheading The @code{-symbol-info-line} Command
17946 @findex -symbol-info-line
17948 @subsubheading Synopsis
17954 Show the core addresses of the code for a source line.
17956 @subsubheading @value{GDBN} Command
17958 The corresponding @value{GDBN} command is @samp{info line}.
17959 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
17961 @subsubheading Example
17965 @subheading The @code{-symbol-info-symbol} Command
17966 @findex -symbol-info-symbol
17968 @subsubheading Synopsis
17971 -symbol-info-symbol @var{addr}
17974 Describe what symbol is at location @var{addr}.
17976 @subsubheading @value{GDBN} Command
17978 The corresponding @value{GDBN} command is @samp{info symbol}.
17980 @subsubheading Example
17984 @subheading The @code{-symbol-list-functions} Command
17985 @findex -symbol-list-functions
17987 @subsubheading Synopsis
17990 -symbol-list-functions
17993 List the functions in the executable.
17995 @subsubheading @value{GDBN} Command
17997 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
17998 @samp{gdb_search} in @code{gdbtk}.
18000 @subsubheading Example
18004 @subheading The @code{-symbol-list-lines} Command
18005 @findex -symbol-list-lines
18007 @subsubheading Synopsis
18010 -symbol-list-lines @var{filename}
18013 Print the list of lines that contain code and their associated program
18014 addresses for the given source filename. The entries are sorted in
18015 ascending PC order.
18017 @subsubheading @value{GDBN} Command
18019 There is no corresponding @value{GDBN} command.
18021 @subsubheading Example
18024 -symbol-list-lines basics.c
18025 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
18030 @subheading The @code{-symbol-list-types} Command
18031 @findex -symbol-list-types
18033 @subsubheading Synopsis
18039 List all the type names.
18041 @subsubheading @value{GDBN} Command
18043 The corresponding commands are @samp{info types} in @value{GDBN},
18044 @samp{gdb_search} in @code{gdbtk}.
18046 @subsubheading Example
18050 @subheading The @code{-symbol-list-variables} Command
18051 @findex -symbol-list-variables
18053 @subsubheading Synopsis
18056 -symbol-list-variables
18059 List all the global and static variable names.
18061 @subsubheading @value{GDBN} Command
18063 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
18065 @subsubheading Example
18069 @subheading The @code{-symbol-locate} Command
18070 @findex -symbol-locate
18072 @subsubheading Synopsis
18078 @subsubheading @value{GDBN} Command
18080 @samp{gdb_loc} in @code{gdbtk}.
18082 @subsubheading Example
18086 @subheading The @code{-symbol-type} Command
18087 @findex -symbol-type
18089 @subsubheading Synopsis
18092 -symbol-type @var{variable}
18095 Show type of @var{variable}.
18097 @subsubheading @value{GDBN} Command
18099 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
18100 @samp{gdb_obj_variable}.
18102 @subsubheading Example
18106 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18107 @node GDB/MI Target Manipulation
18108 @section @sc{gdb/mi} Target Manipulation Commands
18111 @subheading The @code{-target-attach} Command
18112 @findex -target-attach
18114 @subsubheading Synopsis
18117 -target-attach @var{pid} | @var{file}
18120 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
18122 @subsubheading @value{GDBN} command
18124 The corresponding @value{GDBN} command is @samp{attach}.
18126 @subsubheading Example
18130 @subheading The @code{-target-compare-sections} Command
18131 @findex -target-compare-sections
18133 @subsubheading Synopsis
18136 -target-compare-sections [ @var{section} ]
18139 Compare data of section @var{section} on target to the exec file.
18140 Without the argument, all sections are compared.
18142 @subsubheading @value{GDBN} Command
18144 The @value{GDBN} equivalent is @samp{compare-sections}.
18146 @subsubheading Example
18150 @subheading The @code{-target-detach} Command
18151 @findex -target-detach
18153 @subsubheading Synopsis
18159 Disconnect from the remote target. There's no output.
18161 @subsubheading @value{GDBN} command
18163 The corresponding @value{GDBN} command is @samp{detach}.
18165 @subsubheading Example
18175 @subheading The @code{-target-disconnect} Command
18176 @findex -target-disconnect
18178 @subsubheading Synopsis
18184 Disconnect from the remote target. There's no output.
18186 @subsubheading @value{GDBN} command
18188 The corresponding @value{GDBN} command is @samp{disconnect}.
18190 @subsubheading Example
18200 @subheading The @code{-target-download} Command
18201 @findex -target-download
18203 @subsubheading Synopsis
18209 Loads the executable onto the remote target.
18210 It prints out an update message every half second, which includes the fields:
18214 The name of the section.
18216 The size of what has been sent so far for that section.
18218 The size of the section.
18220 The total size of what was sent so far (the current and the previous sections).
18222 The size of the overall executable to download.
18226 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
18227 @sc{gdb/mi} Output Syntax}).
18229 In addition, it prints the name and size of the sections, as they are
18230 downloaded. These messages include the following fields:
18234 The name of the section.
18236 The size of the section.
18238 The size of the overall executable to download.
18242 At the end, a summary is printed.
18244 @subsubheading @value{GDBN} Command
18246 The corresponding @value{GDBN} command is @samp{load}.
18248 @subsubheading Example
18250 Note: each status message appears on a single line. Here the messages
18251 have been broken down so that they can fit onto a page.
18256 +download,@{section=".text",section-size="6668",total-size="9880"@}
18257 +download,@{section=".text",section-sent="512",section-size="6668",
18258 total-sent="512",total-size="9880"@}
18259 +download,@{section=".text",section-sent="1024",section-size="6668",
18260 total-sent="1024",total-size="9880"@}
18261 +download,@{section=".text",section-sent="1536",section-size="6668",
18262 total-sent="1536",total-size="9880"@}
18263 +download,@{section=".text",section-sent="2048",section-size="6668",
18264 total-sent="2048",total-size="9880"@}
18265 +download,@{section=".text",section-sent="2560",section-size="6668",
18266 total-sent="2560",total-size="9880"@}
18267 +download,@{section=".text",section-sent="3072",section-size="6668",
18268 total-sent="3072",total-size="9880"@}
18269 +download,@{section=".text",section-sent="3584",section-size="6668",
18270 total-sent="3584",total-size="9880"@}
18271 +download,@{section=".text",section-sent="4096",section-size="6668",
18272 total-sent="4096",total-size="9880"@}
18273 +download,@{section=".text",section-sent="4608",section-size="6668",
18274 total-sent="4608",total-size="9880"@}
18275 +download,@{section=".text",section-sent="5120",section-size="6668",
18276 total-sent="5120",total-size="9880"@}
18277 +download,@{section=".text",section-sent="5632",section-size="6668",
18278 total-sent="5632",total-size="9880"@}
18279 +download,@{section=".text",section-sent="6144",section-size="6668",
18280 total-sent="6144",total-size="9880"@}
18281 +download,@{section=".text",section-sent="6656",section-size="6668",
18282 total-sent="6656",total-size="9880"@}
18283 +download,@{section=".init",section-size="28",total-size="9880"@}
18284 +download,@{section=".fini",section-size="28",total-size="9880"@}
18285 +download,@{section=".data",section-size="3156",total-size="9880"@}
18286 +download,@{section=".data",section-sent="512",section-size="3156",
18287 total-sent="7236",total-size="9880"@}
18288 +download,@{section=".data",section-sent="1024",section-size="3156",
18289 total-sent="7748",total-size="9880"@}
18290 +download,@{section=".data",section-sent="1536",section-size="3156",
18291 total-sent="8260",total-size="9880"@}
18292 +download,@{section=".data",section-sent="2048",section-size="3156",
18293 total-sent="8772",total-size="9880"@}
18294 +download,@{section=".data",section-sent="2560",section-size="3156",
18295 total-sent="9284",total-size="9880"@}
18296 +download,@{section=".data",section-sent="3072",section-size="3156",
18297 total-sent="9796",total-size="9880"@}
18298 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
18304 @subheading The @code{-target-exec-status} Command
18305 @findex -target-exec-status
18307 @subsubheading Synopsis
18310 -target-exec-status
18313 Provide information on the state of the target (whether it is running or
18314 not, for instance).
18316 @subsubheading @value{GDBN} Command
18318 There's no equivalent @value{GDBN} command.
18320 @subsubheading Example
18324 @subheading The @code{-target-list-available-targets} Command
18325 @findex -target-list-available-targets
18327 @subsubheading Synopsis
18330 -target-list-available-targets
18333 List the possible targets to connect to.
18335 @subsubheading @value{GDBN} Command
18337 The corresponding @value{GDBN} command is @samp{help target}.
18339 @subsubheading Example
18343 @subheading The @code{-target-list-current-targets} Command
18344 @findex -target-list-current-targets
18346 @subsubheading Synopsis
18349 -target-list-current-targets
18352 Describe the current target.
18354 @subsubheading @value{GDBN} Command
18356 The corresponding information is printed by @samp{info file} (among
18359 @subsubheading Example
18363 @subheading The @code{-target-list-parameters} Command
18364 @findex -target-list-parameters
18366 @subsubheading Synopsis
18369 -target-list-parameters
18374 @subsubheading @value{GDBN} Command
18378 @subsubheading Example
18382 @subheading The @code{-target-select} Command
18383 @findex -target-select
18385 @subsubheading Synopsis
18388 -target-select @var{type} @var{parameters @dots{}}
18391 Connect @value{GDBN} to the remote target. This command takes two args:
18395 The type of target, for instance @samp{async}, @samp{remote}, etc.
18396 @item @var{parameters}
18397 Device names, host names and the like. @xref{Target Commands, ,
18398 Commands for managing targets}, for more details.
18401 The output is a connection notification, followed by the address at
18402 which the target program is, in the following form:
18405 ^connected,addr="@var{address}",func="@var{function name}",
18406 args=[@var{arg list}]
18409 @subsubheading @value{GDBN} Command
18411 The corresponding @value{GDBN} command is @samp{target}.
18413 @subsubheading Example
18417 -target-select async /dev/ttya
18418 ^connected,addr="0xfe00a300",func="??",args=[]
18422 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18423 @node GDB/MI Thread Commands
18424 @section @sc{gdb/mi} Thread Commands
18427 @subheading The @code{-thread-info} Command
18428 @findex -thread-info
18430 @subsubheading Synopsis
18436 @subsubheading @value{GDBN} command
18440 @subsubheading Example
18444 @subheading The @code{-thread-list-all-threads} Command
18445 @findex -thread-list-all-threads
18447 @subsubheading Synopsis
18450 -thread-list-all-threads
18453 @subsubheading @value{GDBN} Command
18455 The equivalent @value{GDBN} command is @samp{info threads}.
18457 @subsubheading Example
18461 @subheading The @code{-thread-list-ids} Command
18462 @findex -thread-list-ids
18464 @subsubheading Synopsis
18470 Produces a list of the currently known @value{GDBN} thread ids. At the
18471 end of the list it also prints the total number of such threads.
18473 @subsubheading @value{GDBN} Command
18475 Part of @samp{info threads} supplies the same information.
18477 @subsubheading Example
18479 No threads present, besides the main process:
18484 ^done,thread-ids=@{@},number-of-threads="0"
18494 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18495 number-of-threads="3"
18500 @subheading The @code{-thread-select} Command
18501 @findex -thread-select
18503 @subsubheading Synopsis
18506 -thread-select @var{threadnum}
18509 Make @var{threadnum} the current thread. It prints the number of the new
18510 current thread, and the topmost frame for that thread.
18512 @subsubheading @value{GDBN} Command
18514 The corresponding @value{GDBN} command is @samp{thread}.
18516 @subsubheading Example
18523 *stopped,reason="end-stepping-range",thread-id="2",line="187",
18524 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
18528 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18529 number-of-threads="3"
18532 ^done,new-thread-id="3",
18533 frame=@{level="0",func="vprintf",
18534 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
18535 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
18539 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18540 @node GDB/MI Tracepoint Commands
18541 @section @sc{gdb/mi} Tracepoint Commands
18543 The tracepoint commands are not yet implemented.
18545 @c @subheading -trace-actions
18547 @c @subheading -trace-delete
18549 @c @subheading -trace-disable
18551 @c @subheading -trace-dump
18553 @c @subheading -trace-enable
18555 @c @subheading -trace-exists
18557 @c @subheading -trace-find
18559 @c @subheading -trace-frame-number
18561 @c @subheading -trace-info
18563 @c @subheading -trace-insert
18565 @c @subheading -trace-list
18567 @c @subheading -trace-pass-count
18569 @c @subheading -trace-save
18571 @c @subheading -trace-start
18573 @c @subheading -trace-stop
18576 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18577 @node GDB/MI Variable Objects
18578 @section @sc{gdb/mi} Variable Objects
18581 @subheading Motivation for Variable Objects in @sc{gdb/mi}
18583 For the implementation of a variable debugger window (locals, watched
18584 expressions, etc.), we are proposing the adaptation of the existing code
18585 used by @code{Insight}.
18587 The two main reasons for that are:
18591 It has been proven in practice (it is already on its second generation).
18594 It will shorten development time (needless to say how important it is
18598 The original interface was designed to be used by Tcl code, so it was
18599 slightly changed so it could be used through @sc{gdb/mi}. This section
18600 describes the @sc{gdb/mi} operations that will be available and gives some
18601 hints about their use.
18603 @emph{Note}: In addition to the set of operations described here, we
18604 expect the @sc{gui} implementation of a variable window to require, at
18605 least, the following operations:
18608 @item @code{-gdb-show} @code{output-radix}
18609 @item @code{-stack-list-arguments}
18610 @item @code{-stack-list-locals}
18611 @item @code{-stack-select-frame}
18614 @subheading Introduction to Variable Objects in @sc{gdb/mi}
18616 @cindex variable objects in @sc{gdb/mi}
18617 The basic idea behind variable objects is the creation of a named object
18618 to represent a variable, an expression, a memory location or even a CPU
18619 register. For each object created, a set of operations is available for
18620 examining or changing its properties.
18622 Furthermore, complex data types, such as C structures, are represented
18623 in a tree format. For instance, the @code{struct} type variable is the
18624 root and the children will represent the struct members. If a child
18625 is itself of a complex type, it will also have children of its own.
18626 Appropriate language differences are handled for C, C@t{++} and Java.
18628 When returning the actual values of the objects, this facility allows
18629 for the individual selection of the display format used in the result
18630 creation. It can be chosen among: binary, decimal, hexadecimal, octal
18631 and natural. Natural refers to a default format automatically
18632 chosen based on the variable type (like decimal for an @code{int}, hex
18633 for pointers, etc.).
18635 The following is the complete set of @sc{gdb/mi} operations defined to
18636 access this functionality:
18638 @multitable @columnfractions .4 .6
18639 @item @strong{Operation}
18640 @tab @strong{Description}
18642 @item @code{-var-create}
18643 @tab create a variable object
18644 @item @code{-var-delete}
18645 @tab delete the variable object and its children
18646 @item @code{-var-set-format}
18647 @tab set the display format of this variable
18648 @item @code{-var-show-format}
18649 @tab show the display format of this variable
18650 @item @code{-var-info-num-children}
18651 @tab tells how many children this object has
18652 @item @code{-var-list-children}
18653 @tab return a list of the object's children
18654 @item @code{-var-info-type}
18655 @tab show the type of this variable object
18656 @item @code{-var-info-expression}
18657 @tab print what this variable object represents
18658 @item @code{-var-show-attributes}
18659 @tab is this variable editable? does it exist here?
18660 @item @code{-var-evaluate-expression}
18661 @tab get the value of this variable
18662 @item @code{-var-assign}
18663 @tab set the value of this variable
18664 @item @code{-var-update}
18665 @tab update the variable and its children
18668 In the next subsection we describe each operation in detail and suggest
18669 how it can be used.
18671 @subheading Description And Use of Operations on Variable Objects
18673 @subheading The @code{-var-create} Command
18674 @findex -var-create
18676 @subsubheading Synopsis
18679 -var-create @{@var{name} | "-"@}
18680 @{@var{frame-addr} | "*"@} @var{expression}
18683 This operation creates a variable object, which allows the monitoring of
18684 a variable, the result of an expression, a memory cell or a CPU
18687 The @var{name} parameter is the string by which the object can be
18688 referenced. It must be unique. If @samp{-} is specified, the varobj
18689 system will generate a string ``varNNNNNN'' automatically. It will be
18690 unique provided that one does not specify @var{name} on that format.
18691 The command fails if a duplicate name is found.
18693 The frame under which the expression should be evaluated can be
18694 specified by @var{frame-addr}. A @samp{*} indicates that the current
18695 frame should be used.
18697 @var{expression} is any expression valid on the current language set (must not
18698 begin with a @samp{*}), or one of the following:
18702 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
18705 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
18708 @samp{$@var{regname}} --- a CPU register name
18711 @subsubheading Result
18713 This operation returns the name, number of children and the type of the
18714 object created. Type is returned as a string as the ones generated by
18715 the @value{GDBN} CLI:
18718 name="@var{name}",numchild="N",type="@var{type}"
18722 @subheading The @code{-var-delete} Command
18723 @findex -var-delete
18725 @subsubheading Synopsis
18728 -var-delete @var{name}
18731 Deletes a previously created variable object and all of its children.
18733 Returns an error if the object @var{name} is not found.
18736 @subheading The @code{-var-set-format} Command
18737 @findex -var-set-format
18739 @subsubheading Synopsis
18742 -var-set-format @var{name} @var{format-spec}
18745 Sets the output format for the value of the object @var{name} to be
18748 The syntax for the @var{format-spec} is as follows:
18751 @var{format-spec} @expansion{}
18752 @{binary | decimal | hexadecimal | octal | natural@}
18756 @subheading The @code{-var-show-format} Command
18757 @findex -var-show-format
18759 @subsubheading Synopsis
18762 -var-show-format @var{name}
18765 Returns the format used to display the value of the object @var{name}.
18768 @var{format} @expansion{}
18773 @subheading The @code{-var-info-num-children} Command
18774 @findex -var-info-num-children
18776 @subsubheading Synopsis
18779 -var-info-num-children @var{name}
18782 Returns the number of children of a variable object @var{name}:
18789 @subheading The @code{-var-list-children} Command
18790 @findex -var-list-children
18792 @subsubheading Synopsis
18795 -var-list-children [@var{print-values}] @var{name}
18798 Returns a list of the children of the specified variable object. With
18799 just the variable object name as an argument or with an optional
18800 preceding argument of 0 or @code{--no-values}, prints only the names of the
18801 variables. With an optional preceding argument of 1 or @code{--all-values},
18802 also prints their values.
18804 @subsubheading Example
18808 -var-list-children n
18809 numchild=@var{n},children=[@{name=@var{name},
18810 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
18812 -var-list-children --all-values n
18813 numchild=@var{n},children=[@{name=@var{name},
18814 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
18818 @subheading The @code{-var-info-type} Command
18819 @findex -var-info-type
18821 @subsubheading Synopsis
18824 -var-info-type @var{name}
18827 Returns the type of the specified variable @var{name}. The type is
18828 returned as a string in the same format as it is output by the
18832 type=@var{typename}
18836 @subheading The @code{-var-info-expression} Command
18837 @findex -var-info-expression
18839 @subsubheading Synopsis
18842 -var-info-expression @var{name}
18845 Returns what is represented by the variable object @var{name}:
18848 lang=@var{lang-spec},exp=@var{expression}
18852 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
18854 @subheading The @code{-var-show-attributes} Command
18855 @findex -var-show-attributes
18857 @subsubheading Synopsis
18860 -var-show-attributes @var{name}
18863 List attributes of the specified variable object @var{name}:
18866 status=@var{attr} [ ( ,@var{attr} )* ]
18870 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
18872 @subheading The @code{-var-evaluate-expression} Command
18873 @findex -var-evaluate-expression
18875 @subsubheading Synopsis
18878 -var-evaluate-expression @var{name}
18881 Evaluates the expression that is represented by the specified variable
18882 object and returns its value as a string in the current format specified
18889 Note that one must invoke @code{-var-list-children} for a variable
18890 before the value of a child variable can be evaluated.
18892 @subheading The @code{-var-assign} Command
18893 @findex -var-assign
18895 @subsubheading Synopsis
18898 -var-assign @var{name} @var{expression}
18901 Assigns the value of @var{expression} to the variable object specified
18902 by @var{name}. The object must be @samp{editable}. If the variable's
18903 value is altered by the assign, the variable will show up in any
18904 subsequent @code{-var-update} list.
18906 @subsubheading Example
18914 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
18918 @subheading The @code{-var-update} Command
18919 @findex -var-update
18921 @subsubheading Synopsis
18924 -var-update @{@var{name} | "*"@}
18927 Update the value of the variable object @var{name} by evaluating its
18928 expression after fetching all the new values from memory or registers.
18929 A @samp{*} causes all existing variable objects to be updated.
18933 @chapter @value{GDBN} Annotations
18935 This chapter describes annotations in @value{GDBN}. Annotations were
18936 designed to interface @value{GDBN} to graphical user interfaces or other
18937 similar programs which want to interact with @value{GDBN} at a
18938 relatively high level.
18940 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
18944 This is Edition @value{EDITION}, @value{DATE}.
18948 * Annotations Overview:: What annotations are; the general syntax.
18949 * Server Prefix:: Issuing a command without affecting user state.
18950 * Prompting:: Annotations marking @value{GDBN}'s need for input.
18951 * Errors:: Annotations for error messages.
18952 * Invalidation:: Some annotations describe things now invalid.
18953 * Annotations for Running::
18954 Whether the program is running, how it stopped, etc.
18955 * Source Annotations:: Annotations describing source code.
18958 @node Annotations Overview
18959 @section What is an Annotation?
18960 @cindex annotations
18962 Annotations start with a newline character, two @samp{control-z}
18963 characters, and the name of the annotation. If there is no additional
18964 information associated with this annotation, the name of the annotation
18965 is followed immediately by a newline. If there is additional
18966 information, the name of the annotation is followed by a space, the
18967 additional information, and a newline. The additional information
18968 cannot contain newline characters.
18970 Any output not beginning with a newline and two @samp{control-z}
18971 characters denotes literal output from @value{GDBN}. Currently there is
18972 no need for @value{GDBN} to output a newline followed by two
18973 @samp{control-z} characters, but if there was such a need, the
18974 annotations could be extended with an @samp{escape} annotation which
18975 means those three characters as output.
18977 The annotation @var{level}, which is specified using the
18978 @option{--annotate} command line option (@pxref{Mode Options}), controls
18979 how much information @value{GDBN} prints together with its prompt,
18980 values of expressions, source lines, and other types of output. Level 0
18981 is for no anntations, level 1 is for use when @value{GDBN} is run as a
18982 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
18983 for programs that control @value{GDBN}, and level 2 annotations have
18984 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
18985 Interface, annotate, GDB's Obsolete Annotations}). This chapter
18986 describes level 3 annotations.
18988 A simple example of starting up @value{GDBN} with annotations is:
18991 $ @kbd{gdb --annotate=3}
18993 Copyright 2003 Free Software Foundation, Inc.
18994 GDB is free software, covered by the GNU General Public License,
18995 and you are welcome to change it and/or distribute copies of it
18996 under certain conditions.
18997 Type "show copying" to see the conditions.
18998 There is absolutely no warranty for GDB. Type "show warranty"
19000 This GDB was configured as "i386-pc-linux-gnu"
19011 Here @samp{quit} is input to @value{GDBN}; the rest is output from
19012 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
19013 denotes a @samp{control-z} character) are annotations; the rest is
19014 output from @value{GDBN}.
19016 @node Server Prefix
19017 @section The Server Prefix
19018 @cindex server prefix for annotations
19020 To issue a command to @value{GDBN} without affecting certain aspects of
19021 the state which is seen by users, prefix it with @samp{server }. This
19022 means that this command will not affect the command history, nor will it
19023 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
19024 pressed on a line by itself.
19026 The server prefix does not affect the recording of values into the value
19027 history; to print a value without recording it into the value history,
19028 use the @code{output} command instead of the @code{print} command.
19031 @section Annotation for @value{GDBN} Input
19033 @cindex annotations for prompts
19034 When @value{GDBN} prompts for input, it annotates this fact so it is possible
19035 to know when to send output, when the output from a given command is
19038 Different kinds of input each have a different @dfn{input type}. Each
19039 input type has three annotations: a @code{pre-} annotation, which
19040 denotes the beginning of any prompt which is being output, a plain
19041 annotation, which denotes the end of the prompt, and then a @code{post-}
19042 annotation which denotes the end of any echo which may (or may not) be
19043 associated with the input. For example, the @code{prompt} input type
19044 features the following annotations:
19052 The input types are
19057 @findex post-prompt
19059 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
19061 @findex pre-commands
19063 @findex post-commands
19065 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
19066 command. The annotations are repeated for each command which is input.
19068 @findex pre-overload-choice
19069 @findex overload-choice
19070 @findex post-overload-choice
19071 @item overload-choice
19072 When @value{GDBN} wants the user to select between various overloaded functions.
19078 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
19080 @findex pre-prompt-for-continue
19081 @findex prompt-for-continue
19082 @findex post-prompt-for-continue
19083 @item prompt-for-continue
19084 When @value{GDBN} is asking the user to press return to continue. Note: Don't
19085 expect this to work well; instead use @code{set height 0} to disable
19086 prompting. This is because the counting of lines is buggy in the
19087 presence of annotations.
19092 @cindex annotations for errors, warnings and interrupts
19099 This annotation occurs right before @value{GDBN} responds to an interrupt.
19106 This annotation occurs right before @value{GDBN} responds to an error.
19108 Quit and error annotations indicate that any annotations which @value{GDBN} was
19109 in the middle of may end abruptly. For example, if a
19110 @code{value-history-begin} annotation is followed by a @code{error}, one
19111 cannot expect to receive the matching @code{value-history-end}. One
19112 cannot expect not to receive it either, however; an error annotation
19113 does not necessarily mean that @value{GDBN} is immediately returning all the way
19116 @findex error-begin
19117 A quit or error annotation may be preceded by
19123 Any output between that and the quit or error annotation is the error
19126 Warning messages are not yet annotated.
19127 @c If we want to change that, need to fix warning(), type_error(),
19128 @c range_error(), and possibly other places.
19131 @section Invalidation Notices
19133 @cindex annotations for invalidation messages
19134 The following annotations say that certain pieces of state may have
19138 @findex frames-invalid
19139 @item ^Z^Zframes-invalid
19141 The frames (for example, output from the @code{backtrace} command) may
19144 @findex breakpoints-invalid
19145 @item ^Z^Zbreakpoints-invalid
19147 The breakpoints may have changed. For example, the user just added or
19148 deleted a breakpoint.
19151 @node Annotations for Running
19152 @section Running the Program
19153 @cindex annotations for running programs
19157 When the program starts executing due to a @value{GDBN} command such as
19158 @code{step} or @code{continue},
19164 is output. When the program stops,
19170 is output. Before the @code{stopped} annotation, a variety of
19171 annotations describe how the program stopped.
19175 @item ^Z^Zexited @var{exit-status}
19176 The program exited, and @var{exit-status} is the exit status (zero for
19177 successful exit, otherwise nonzero).
19180 @findex signal-name
19181 @findex signal-name-end
19182 @findex signal-string
19183 @findex signal-string-end
19184 @item ^Z^Zsignalled
19185 The program exited with a signal. After the @code{^Z^Zsignalled}, the
19186 annotation continues:
19192 ^Z^Zsignal-name-end
19196 ^Z^Zsignal-string-end
19201 where @var{name} is the name of the signal, such as @code{SIGILL} or
19202 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
19203 as @code{Illegal Instruction} or @code{Segmentation fault}.
19204 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
19205 user's benefit and have no particular format.
19209 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
19210 just saying that the program received the signal, not that it was
19211 terminated with it.
19214 @item ^Z^Zbreakpoint @var{number}
19215 The program hit breakpoint number @var{number}.
19218 @item ^Z^Zwatchpoint @var{number}
19219 The program hit watchpoint number @var{number}.
19222 @node Source Annotations
19223 @section Displaying Source
19224 @cindex annotations for source display
19227 The following annotation is used instead of displaying source code:
19230 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
19233 where @var{filename} is an absolute file name indicating which source
19234 file, @var{line} is the line number within that file (where 1 is the
19235 first line in the file), @var{character} is the character position
19236 within the file (where 0 is the first character in the file) (for most
19237 debug formats this will necessarily point to the beginning of a line),
19238 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
19239 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
19240 @var{addr} is the address in the target program associated with the
19241 source which is being displayed. @var{addr} is in the form @samp{0x}
19242 followed by one or more lowercase hex digits (note that this does not
19243 depend on the language).
19246 @chapter Reporting Bugs in @value{GDBN}
19247 @cindex bugs in @value{GDBN}
19248 @cindex reporting bugs in @value{GDBN}
19250 Your bug reports play an essential role in making @value{GDBN} reliable.
19252 Reporting a bug may help you by bringing a solution to your problem, or it
19253 may not. But in any case the principal function of a bug report is to help
19254 the entire community by making the next version of @value{GDBN} work better. Bug
19255 reports are your contribution to the maintenance of @value{GDBN}.
19257 In order for a bug report to serve its purpose, you must include the
19258 information that enables us to fix the bug.
19261 * Bug Criteria:: Have you found a bug?
19262 * Bug Reporting:: How to report bugs
19266 @section Have you found a bug?
19267 @cindex bug criteria
19269 If you are not sure whether you have found a bug, here are some guidelines:
19272 @cindex fatal signal
19273 @cindex debugger crash
19274 @cindex crash of debugger
19276 If the debugger gets a fatal signal, for any input whatever, that is a
19277 @value{GDBN} bug. Reliable debuggers never crash.
19279 @cindex error on valid input
19281 If @value{GDBN} produces an error message for valid input, that is a
19282 bug. (Note that if you're cross debugging, the problem may also be
19283 somewhere in the connection to the target.)
19285 @cindex invalid input
19287 If @value{GDBN} does not produce an error message for invalid input,
19288 that is a bug. However, you should note that your idea of
19289 ``invalid input'' might be our idea of ``an extension'' or ``support
19290 for traditional practice''.
19293 If you are an experienced user of debugging tools, your suggestions
19294 for improvement of @value{GDBN} are welcome in any case.
19297 @node Bug Reporting
19298 @section How to report bugs
19299 @cindex bug reports
19300 @cindex @value{GDBN} bugs, reporting
19302 A number of companies and individuals offer support for @sc{gnu} products.
19303 If you obtained @value{GDBN} from a support organization, we recommend you
19304 contact that organization first.
19306 You can find contact information for many support companies and
19307 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
19309 @c should add a web page ref...
19311 In any event, we also recommend that you submit bug reports for
19312 @value{GDBN}. The prefered method is to submit them directly using
19313 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
19314 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
19317 @strong{Do not send bug reports to @samp{info-gdb}, or to
19318 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
19319 not want to receive bug reports. Those that do have arranged to receive
19322 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
19323 serves as a repeater. The mailing list and the newsgroup carry exactly
19324 the same messages. Often people think of posting bug reports to the
19325 newsgroup instead of mailing them. This appears to work, but it has one
19326 problem which can be crucial: a newsgroup posting often lacks a mail
19327 path back to the sender. Thus, if we need to ask for more information,
19328 we may be unable to reach you. For this reason, it is better to send
19329 bug reports to the mailing list.
19331 The fundamental principle of reporting bugs usefully is this:
19332 @strong{report all the facts}. If you are not sure whether to state a
19333 fact or leave it out, state it!
19335 Often people omit facts because they think they know what causes the
19336 problem and assume that some details do not matter. Thus, you might
19337 assume that the name of the variable you use in an example does not matter.
19338 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
19339 stray memory reference which happens to fetch from the location where that
19340 name is stored in memory; perhaps, if the name were different, the contents
19341 of that location would fool the debugger into doing the right thing despite
19342 the bug. Play it safe and give a specific, complete example. That is the
19343 easiest thing for you to do, and the most helpful.
19345 Keep in mind that the purpose of a bug report is to enable us to fix the
19346 bug. It may be that the bug has been reported previously, but neither
19347 you nor we can know that unless your bug report is complete and
19350 Sometimes people give a few sketchy facts and ask, ``Does this ring a
19351 bell?'' Those bug reports are useless, and we urge everyone to
19352 @emph{refuse to respond to them} except to chide the sender to report
19355 To enable us to fix the bug, you should include all these things:
19359 The version of @value{GDBN}. @value{GDBN} announces it if you start
19360 with no arguments; you can also print it at any time using @code{show
19363 Without this, we will not know whether there is any point in looking for
19364 the bug in the current version of @value{GDBN}.
19367 The type of machine you are using, and the operating system name and
19371 What compiler (and its version) was used to compile @value{GDBN}---e.g.
19372 ``@value{GCC}--2.8.1''.
19375 What compiler (and its version) was used to compile the program you are
19376 debugging---e.g. ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
19377 C Compiler''. For GCC, you can say @code{gcc --version} to get this
19378 information; for other compilers, see the documentation for those
19382 The command arguments you gave the compiler to compile your example and
19383 observe the bug. For example, did you use @samp{-O}? To guarantee
19384 you will not omit something important, list them all. A copy of the
19385 Makefile (or the output from make) is sufficient.
19387 If we were to try to guess the arguments, we would probably guess wrong
19388 and then we might not encounter the bug.
19391 A complete input script, and all necessary source files, that will
19395 A description of what behavior you observe that you believe is
19396 incorrect. For example, ``It gets a fatal signal.''
19398 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
19399 will certainly notice it. But if the bug is incorrect output, we might
19400 not notice unless it is glaringly wrong. You might as well not give us
19401 a chance to make a mistake.
19403 Even if the problem you experience is a fatal signal, you should still
19404 say so explicitly. Suppose something strange is going on, such as, your
19405 copy of @value{GDBN} is out of synch, or you have encountered a bug in
19406 the C library on your system. (This has happened!) Your copy might
19407 crash and ours would not. If you told us to expect a crash, then when
19408 ours fails to crash, we would know that the bug was not happening for
19409 us. If you had not told us to expect a crash, then we would not be able
19410 to draw any conclusion from our observations.
19413 @cindex recording a session script
19414 To collect all this information, you can use a session recording program
19415 such as @command{script}, which is available on many Unix systems.
19416 Just run your @value{GDBN} session inside @command{script} and then
19417 include the @file{typescript} file with your bug report.
19419 Another way to record a @value{GDBN} session is to run @value{GDBN}
19420 inside Emacs and then save the entire buffer to a file.
19423 If you wish to suggest changes to the @value{GDBN} source, send us context
19424 diffs. If you even discuss something in the @value{GDBN} source, refer to
19425 it by context, not by line number.
19427 The line numbers in our development sources will not match those in your
19428 sources. Your line numbers would convey no useful information to us.
19432 Here are some things that are not necessary:
19436 A description of the envelope of the bug.
19438 Often people who encounter a bug spend a lot of time investigating
19439 which changes to the input file will make the bug go away and which
19440 changes will not affect it.
19442 This is often time consuming and not very useful, because the way we
19443 will find the bug is by running a single example under the debugger
19444 with breakpoints, not by pure deduction from a series of examples.
19445 We recommend that you save your time for something else.
19447 Of course, if you can find a simpler example to report @emph{instead}
19448 of the original one, that is a convenience for us. Errors in the
19449 output will be easier to spot, running under the debugger will take
19450 less time, and so on.
19452 However, simplification is not vital; if you do not want to do this,
19453 report the bug anyway and send us the entire test case you used.
19456 A patch for the bug.
19458 A patch for the bug does help us if it is a good one. But do not omit
19459 the necessary information, such as the test case, on the assumption that
19460 a patch is all we need. We might see problems with your patch and decide
19461 to fix the problem another way, or we might not understand it at all.
19463 Sometimes with a program as complicated as @value{GDBN} it is very hard to
19464 construct an example that will make the program follow a certain path
19465 through the code. If you do not send us the example, we will not be able
19466 to construct one, so we will not be able to verify that the bug is fixed.
19468 And if we cannot understand what bug you are trying to fix, or why your
19469 patch should be an improvement, we will not install it. A test case will
19470 help us to understand.
19473 A guess about what the bug is or what it depends on.
19475 Such guesses are usually wrong. Even we cannot guess right about such
19476 things without first using the debugger to find the facts.
19479 @c The readline documentation is distributed with the readline code
19480 @c and consists of the two following files:
19482 @c inc-hist.texinfo
19483 @c Use -I with makeinfo to point to the appropriate directory,
19484 @c environment var TEXINPUTS with TeX.
19485 @include rluser.texinfo
19486 @include inc-hist.texinfo
19489 @node Formatting Documentation
19490 @appendix Formatting Documentation
19492 @cindex @value{GDBN} reference card
19493 @cindex reference card
19494 The @value{GDBN} 4 release includes an already-formatted reference card, ready
19495 for printing with PostScript or Ghostscript, in the @file{gdb}
19496 subdirectory of the main source directory@footnote{In
19497 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
19498 release.}. If you can use PostScript or Ghostscript with your printer,
19499 you can print the reference card immediately with @file{refcard.ps}.
19501 The release also includes the source for the reference card. You
19502 can format it, using @TeX{}, by typing:
19508 The @value{GDBN} reference card is designed to print in @dfn{landscape}
19509 mode on US ``letter'' size paper;
19510 that is, on a sheet 11 inches wide by 8.5 inches
19511 high. You will need to specify this form of printing as an option to
19512 your @sc{dvi} output program.
19514 @cindex documentation
19516 All the documentation for @value{GDBN} comes as part of the machine-readable
19517 distribution. The documentation is written in Texinfo format, which is
19518 a documentation system that uses a single source file to produce both
19519 on-line information and a printed manual. You can use one of the Info
19520 formatting commands to create the on-line version of the documentation
19521 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
19523 @value{GDBN} includes an already formatted copy of the on-line Info
19524 version of this manual in the @file{gdb} subdirectory. The main Info
19525 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
19526 subordinate files matching @samp{gdb.info*} in the same directory. If
19527 necessary, you can print out these files, or read them with any editor;
19528 but they are easier to read using the @code{info} subsystem in @sc{gnu}
19529 Emacs or the standalone @code{info} program, available as part of the
19530 @sc{gnu} Texinfo distribution.
19532 If you want to format these Info files yourself, you need one of the
19533 Info formatting programs, such as @code{texinfo-format-buffer} or
19536 If you have @code{makeinfo} installed, and are in the top level
19537 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
19538 version @value{GDBVN}), you can make the Info file by typing:
19545 If you want to typeset and print copies of this manual, you need @TeX{},
19546 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
19547 Texinfo definitions file.
19549 @TeX{} is a typesetting program; it does not print files directly, but
19550 produces output files called @sc{dvi} files. To print a typeset
19551 document, you need a program to print @sc{dvi} files. If your system
19552 has @TeX{} installed, chances are it has such a program. The precise
19553 command to use depends on your system; @kbd{lpr -d} is common; another
19554 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
19555 require a file name without any extension or a @samp{.dvi} extension.
19557 @TeX{} also requires a macro definitions file called
19558 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
19559 written in Texinfo format. On its own, @TeX{} cannot either read or
19560 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
19561 and is located in the @file{gdb-@var{version-number}/texinfo}
19564 If you have @TeX{} and a @sc{dvi} printer program installed, you can
19565 typeset and print this manual. First switch to the the @file{gdb}
19566 subdirectory of the main source directory (for example, to
19567 @file{gdb-@value{GDBVN}/gdb}) and type:
19573 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
19575 @node Installing GDB
19576 @appendix Installing @value{GDBN}
19577 @cindex configuring @value{GDBN}
19578 @cindex installation
19579 @cindex configuring @value{GDBN}, and source tree subdirectories
19581 @value{GDBN} comes with a @code{configure} script that automates the process
19582 of preparing @value{GDBN} for installation; you can then use @code{make} to
19583 build the @code{gdb} program.
19585 @c irrelevant in info file; it's as current as the code it lives with.
19586 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
19587 look at the @file{README} file in the sources; we may have improved the
19588 installation procedures since publishing this manual.}
19591 The @value{GDBN} distribution includes all the source code you need for
19592 @value{GDBN} in a single directory, whose name is usually composed by
19593 appending the version number to @samp{gdb}.
19595 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
19596 @file{gdb-@value{GDBVN}} directory. That directory contains:
19599 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
19600 script for configuring @value{GDBN} and all its supporting libraries
19602 @item gdb-@value{GDBVN}/gdb
19603 the source specific to @value{GDBN} itself
19605 @item gdb-@value{GDBVN}/bfd
19606 source for the Binary File Descriptor library
19608 @item gdb-@value{GDBVN}/include
19609 @sc{gnu} include files
19611 @item gdb-@value{GDBVN}/libiberty
19612 source for the @samp{-liberty} free software library
19614 @item gdb-@value{GDBVN}/opcodes
19615 source for the library of opcode tables and disassemblers
19617 @item gdb-@value{GDBVN}/readline
19618 source for the @sc{gnu} command-line interface
19620 @item gdb-@value{GDBVN}/glob
19621 source for the @sc{gnu} filename pattern-matching subroutine
19623 @item gdb-@value{GDBVN}/mmalloc
19624 source for the @sc{gnu} memory-mapped malloc package
19627 The simplest way to configure and build @value{GDBN} is to run @code{configure}
19628 from the @file{gdb-@var{version-number}} source directory, which in
19629 this example is the @file{gdb-@value{GDBVN}} directory.
19631 First switch to the @file{gdb-@var{version-number}} source directory
19632 if you are not already in it; then run @code{configure}. Pass the
19633 identifier for the platform on which @value{GDBN} will run as an
19639 cd gdb-@value{GDBVN}
19640 ./configure @var{host}
19645 where @var{host} is an identifier such as @samp{sun4} or
19646 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
19647 (You can often leave off @var{host}; @code{configure} tries to guess the
19648 correct value by examining your system.)
19650 Running @samp{configure @var{host}} and then running @code{make} builds the
19651 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
19652 libraries, then @code{gdb} itself. The configured source files, and the
19653 binaries, are left in the corresponding source directories.
19656 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
19657 system does not recognize this automatically when you run a different
19658 shell, you may need to run @code{sh} on it explicitly:
19661 sh configure @var{host}
19664 If you run @code{configure} from a directory that contains source
19665 directories for multiple libraries or programs, such as the
19666 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
19667 creates configuration files for every directory level underneath (unless
19668 you tell it not to, with the @samp{--norecursion} option).
19670 You should run the @code{configure} script from the top directory in the
19671 source tree, the @file{gdb-@var{version-number}} directory. If you run
19672 @code{configure} from one of the subdirectories, you will configure only
19673 that subdirectory. That is usually not what you want. In particular,
19674 if you run the first @code{configure} from the @file{gdb} subdirectory
19675 of the @file{gdb-@var{version-number}} directory, you will omit the
19676 configuration of @file{bfd}, @file{readline}, and other sibling
19677 directories of the @file{gdb} subdirectory. This leads to build errors
19678 about missing include files such as @file{bfd/bfd.h}.
19680 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
19681 However, you should make sure that the shell on your path (named by
19682 the @samp{SHELL} environment variable) is publicly readable. Remember
19683 that @value{GDBN} uses the shell to start your program---some systems refuse to
19684 let @value{GDBN} debug child processes whose programs are not readable.
19687 * Separate Objdir:: Compiling @value{GDBN} in another directory
19688 * Config Names:: Specifying names for hosts and targets
19689 * Configure Options:: Summary of options for configure
19692 @node Separate Objdir
19693 @section Compiling @value{GDBN} in another directory
19695 If you want to run @value{GDBN} versions for several host or target machines,
19696 you need a different @code{gdb} compiled for each combination of
19697 host and target. @code{configure} is designed to make this easy by
19698 allowing you to generate each configuration in a separate subdirectory,
19699 rather than in the source directory. If your @code{make} program
19700 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
19701 @code{make} in each of these directories builds the @code{gdb}
19702 program specified there.
19704 To build @code{gdb} in a separate directory, run @code{configure}
19705 with the @samp{--srcdir} option to specify where to find the source.
19706 (You also need to specify a path to find @code{configure}
19707 itself from your working directory. If the path to @code{configure}
19708 would be the same as the argument to @samp{--srcdir}, you can leave out
19709 the @samp{--srcdir} option; it is assumed.)
19711 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
19712 separate directory for a Sun 4 like this:
19716 cd gdb-@value{GDBVN}
19719 ../gdb-@value{GDBVN}/configure sun4
19724 When @code{configure} builds a configuration using a remote source
19725 directory, it creates a tree for the binaries with the same structure
19726 (and using the same names) as the tree under the source directory. In
19727 the example, you'd find the Sun 4 library @file{libiberty.a} in the
19728 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
19729 @file{gdb-sun4/gdb}.
19731 Make sure that your path to the @file{configure} script has just one
19732 instance of @file{gdb} in it. If your path to @file{configure} looks
19733 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
19734 one subdirectory of @value{GDBN}, not the whole package. This leads to
19735 build errors about missing include files such as @file{bfd/bfd.h}.
19737 One popular reason to build several @value{GDBN} configurations in separate
19738 directories is to configure @value{GDBN} for cross-compiling (where
19739 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
19740 programs that run on another machine---the @dfn{target}).
19741 You specify a cross-debugging target by
19742 giving the @samp{--target=@var{target}} option to @code{configure}.
19744 When you run @code{make} to build a program or library, you must run
19745 it in a configured directory---whatever directory you were in when you
19746 called @code{configure} (or one of its subdirectories).
19748 The @code{Makefile} that @code{configure} generates in each source
19749 directory also runs recursively. If you type @code{make} in a source
19750 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
19751 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
19752 will build all the required libraries, and then build GDB.
19754 When you have multiple hosts or targets configured in separate
19755 directories, you can run @code{make} on them in parallel (for example,
19756 if they are NFS-mounted on each of the hosts); they will not interfere
19760 @section Specifying names for hosts and targets
19762 The specifications used for hosts and targets in the @code{configure}
19763 script are based on a three-part naming scheme, but some short predefined
19764 aliases are also supported. The full naming scheme encodes three pieces
19765 of information in the following pattern:
19768 @var{architecture}-@var{vendor}-@var{os}
19771 For example, you can use the alias @code{sun4} as a @var{host} argument,
19772 or as the value for @var{target} in a @code{--target=@var{target}}
19773 option. The equivalent full name is @samp{sparc-sun-sunos4}.
19775 The @code{configure} script accompanying @value{GDBN} does not provide
19776 any query facility to list all supported host and target names or
19777 aliases. @code{configure} calls the Bourne shell script
19778 @code{config.sub} to map abbreviations to full names; you can read the
19779 script, if you wish, or you can use it to test your guesses on
19780 abbreviations---for example:
19783 % sh config.sub i386-linux
19785 % sh config.sub alpha-linux
19786 alpha-unknown-linux-gnu
19787 % sh config.sub hp9k700
19789 % sh config.sub sun4
19790 sparc-sun-sunos4.1.1
19791 % sh config.sub sun3
19792 m68k-sun-sunos4.1.1
19793 % sh config.sub i986v
19794 Invalid configuration `i986v': machine `i986v' not recognized
19798 @code{config.sub} is also distributed in the @value{GDBN} source
19799 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
19801 @node Configure Options
19802 @section @code{configure} options
19804 Here is a summary of the @code{configure} options and arguments that
19805 are most often useful for building @value{GDBN}. @code{configure} also has
19806 several other options not listed here. @inforef{What Configure
19807 Does,,configure.info}, for a full explanation of @code{configure}.
19810 configure @r{[}--help@r{]}
19811 @r{[}--prefix=@var{dir}@r{]}
19812 @r{[}--exec-prefix=@var{dir}@r{]}
19813 @r{[}--srcdir=@var{dirname}@r{]}
19814 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
19815 @r{[}--target=@var{target}@r{]}
19820 You may introduce options with a single @samp{-} rather than
19821 @samp{--} if you prefer; but you may abbreviate option names if you use
19826 Display a quick summary of how to invoke @code{configure}.
19828 @item --prefix=@var{dir}
19829 Configure the source to install programs and files under directory
19832 @item --exec-prefix=@var{dir}
19833 Configure the source to install programs under directory
19836 @c avoid splitting the warning from the explanation:
19838 @item --srcdir=@var{dirname}
19839 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
19840 @code{make} that implements the @code{VPATH} feature.}@*
19841 Use this option to make configurations in directories separate from the
19842 @value{GDBN} source directories. Among other things, you can use this to
19843 build (or maintain) several configurations simultaneously, in separate
19844 directories. @code{configure} writes configuration specific files in
19845 the current directory, but arranges for them to use the source in the
19846 directory @var{dirname}. @code{configure} creates directories under
19847 the working directory in parallel to the source directories below
19850 @item --norecursion
19851 Configure only the directory level where @code{configure} is executed; do not
19852 propagate configuration to subdirectories.
19854 @item --target=@var{target}
19855 Configure @value{GDBN} for cross-debugging programs running on the specified
19856 @var{target}. Without this option, @value{GDBN} is configured to debug
19857 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
19859 There is no convenient way to generate a list of all available targets.
19861 @item @var{host} @dots{}
19862 Configure @value{GDBN} to run on the specified @var{host}.
19864 There is no convenient way to generate a list of all available hosts.
19867 There are many other options available as well, but they are generally
19868 needed for special purposes only.
19870 @node Maintenance Commands
19871 @appendix Maintenance Commands
19872 @cindex maintenance commands
19873 @cindex internal commands
19875 In addition to commands intended for @value{GDBN} users, @value{GDBN}
19876 includes a number of commands intended for @value{GDBN} developers.
19877 These commands are provided here for reference.
19880 @kindex maint info breakpoints
19881 @item @anchor{maint info breakpoints}maint info breakpoints
19882 Using the same format as @samp{info breakpoints}, display both the
19883 breakpoints you've set explicitly, and those @value{GDBN} is using for
19884 internal purposes. Internal breakpoints are shown with negative
19885 breakpoint numbers. The type column identifies what kind of breakpoint
19890 Normal, explicitly set breakpoint.
19893 Normal, explicitly set watchpoint.
19896 Internal breakpoint, used to handle correctly stepping through
19897 @code{longjmp} calls.
19899 @item longjmp resume
19900 Internal breakpoint at the target of a @code{longjmp}.
19903 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
19906 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
19909 Shared library events.
19913 @kindex maint internal-error
19914 @kindex maint internal-warning
19915 @item maint internal-error
19916 @itemx maint internal-warning
19917 Cause @value{GDBN} to call the internal function @code{internal_error}
19918 or @code{internal_warning} and hence behave as though an internal error
19919 or internal warning has been detected. In addition to reporting the
19920 internal problem, these functions give the user the opportunity to
19921 either quit @value{GDBN} or create a core file of the current
19922 @value{GDBN} session.
19925 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
19926 @dots{}/maint.c:121: internal-error: testing, 1, 2
19927 A problem internal to GDB has been detected. Further
19928 debugging may prove unreliable.
19929 Quit this debugging session? (y or n) @kbd{n}
19930 Create a core file? (y or n) @kbd{n}
19934 Takes an optional parameter that is used as the text of the error or
19937 @kindex maint print dummy-frames
19938 @item maint print dummy-frames
19940 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
19943 (@value{GDBP}) @kbd{b add}
19945 (@value{GDBP}) @kbd{print add(2,3)}
19946 Breakpoint 2, add (a=2, b=3) at @dots{}
19948 The program being debugged stopped while in a function called from GDB.
19950 (@value{GDBP}) @kbd{maint print dummy-frames}
19951 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
19952 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
19953 call_lo=0x01014000 call_hi=0x01014001
19957 Takes an optional file parameter.
19959 @kindex maint print registers
19960 @kindex maint print raw-registers
19961 @kindex maint print cooked-registers
19962 @kindex maint print register-groups
19963 @item maint print registers
19964 @itemx maint print raw-registers
19965 @itemx maint print cooked-registers
19966 @itemx maint print register-groups
19967 Print @value{GDBN}'s internal register data structures.
19969 The command @code{maint print raw-registers} includes the contents of
19970 the raw register cache; the command @code{maint print cooked-registers}
19971 includes the (cooked) value of all registers; and the command
19972 @code{maint print register-groups} includes the groups that each
19973 register is a member of. @xref{Registers,, Registers, gdbint,
19974 @value{GDBN} Internals}.
19976 Takes an optional file parameter.
19978 @kindex maint print reggroups
19979 @item maint print reggroups
19980 Print @value{GDBN}'s internal register group data structures.
19982 Takes an optional file parameter.
19985 (@value{GDBP}) @kbd{maint print reggroups}
19996 @kindex maint set profile
19997 @kindex maint show profile
19998 @cindex profiling GDB
19999 @item maint set profile
20000 @itemx maint show profile
20001 Control profiling of @value{GDBN}.
20003 Profiling will be disabled until you use the @samp{maint set profile}
20004 command to enable it. When you enable profiling, the system will begin
20005 collecting timing and execution count data; when you disable profiling or
20006 exit @value{GDBN}, the results will be written to a log file. Remember that
20007 if you use profiling, @value{GDBN} will overwrite the profiling log file
20008 (often called @file{gmon.out}). If you have a record of important profiling
20009 data in a @file{gmon.out} file, be sure to move it to a safe location.
20011 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
20012 compiled with the @samp{-pg} compiler option.
20014 @kindex maint set dwarf2 max-cache-age
20015 @kindex maint show dwarf2 max-cache-age
20016 @item maint set dwarf2 max-cache-age
20017 @itemx maint show dwarf2 max-cache-age
20018 Control the DWARF 2 compilation unit cache.
20020 In object files with inter-compilation-unit references, such as those
20021 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
20022 reader needs to frequently refer to previously read compilation units.
20023 This setting controls how long a compilation unit will remain in the cache
20024 if it is not referenced. Setting it to zero disables caching, which will
20025 slow down @value{GDBN} startup but reduce memory consumption.
20030 @node Remote Protocol
20031 @appendix @value{GDBN} Remote Serial Protocol
20036 * Stop Reply Packets::
20037 * General Query Packets::
20038 * Register Packet Format::
20040 * File-I/O remote protocol extension::
20046 There may be occasions when you need to know something about the
20047 protocol---for example, if there is only one serial port to your target
20048 machine, you might want your program to do something special if it
20049 recognizes a packet meant for @value{GDBN}.
20051 In the examples below, @samp{->} and @samp{<-} are used to indicate
20052 transmitted and received data respectfully.
20054 @cindex protocol, @value{GDBN} remote serial
20055 @cindex serial protocol, @value{GDBN} remote
20056 @cindex remote serial protocol
20057 All @value{GDBN} commands and responses (other than acknowledgments) are
20058 sent as a @var{packet}. A @var{packet} is introduced with the character
20059 @samp{$}, the actual @var{packet-data}, and the terminating character
20060 @samp{#} followed by a two-digit @var{checksum}:
20063 @code{$}@var{packet-data}@code{#}@var{checksum}
20067 @cindex checksum, for @value{GDBN} remote
20069 The two-digit @var{checksum} is computed as the modulo 256 sum of all
20070 characters between the leading @samp{$} and the trailing @samp{#} (an
20071 eight bit unsigned checksum).
20073 Implementors should note that prior to @value{GDBN} 5.0 the protocol
20074 specification also included an optional two-digit @var{sequence-id}:
20077 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
20080 @cindex sequence-id, for @value{GDBN} remote
20082 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
20083 has never output @var{sequence-id}s. Stubs that handle packets added
20084 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
20086 @cindex acknowledgment, for @value{GDBN} remote
20087 When either the host or the target machine receives a packet, the first
20088 response expected is an acknowledgment: either @samp{+} (to indicate
20089 the package was received correctly) or @samp{-} (to request
20093 -> @code{$}@var{packet-data}@code{#}@var{checksum}
20098 The host (@value{GDBN}) sends @var{command}s, and the target (the
20099 debugging stub incorporated in your program) sends a @var{response}. In
20100 the case of step and continue @var{command}s, the response is only sent
20101 when the operation has completed (the target has again stopped).
20103 @var{packet-data} consists of a sequence of characters with the
20104 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
20107 Fields within the packet should be separated using @samp{,} @samp{;} or
20108 @cindex remote protocol, field separator
20109 @samp{:}. Except where otherwise noted all numbers are represented in
20110 @sc{hex} with leading zeros suppressed.
20112 Implementors should note that prior to @value{GDBN} 5.0, the character
20113 @samp{:} could not appear as the third character in a packet (as it
20114 would potentially conflict with the @var{sequence-id}).
20116 Response @var{data} can be run-length encoded to save space. A @samp{*}
20117 means that the next character is an @sc{ascii} encoding giving a repeat count
20118 which stands for that many repetitions of the character preceding the
20119 @samp{*}. The encoding is @code{n+29}, yielding a printable character
20120 where @code{n >=3} (which is where rle starts to win). The printable
20121 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
20122 value greater than 126 should not be used.
20129 means the same as "0000".
20131 The error response returned for some packets includes a two character
20132 error number. That number is not well defined.
20134 For any @var{command} not supported by the stub, an empty response
20135 (@samp{$#00}) should be returned. That way it is possible to extend the
20136 protocol. A newer @value{GDBN} can tell if a packet is supported based
20139 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
20140 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
20146 The following table provides a complete list of all currently defined
20147 @var{command}s and their corresponding response @var{data}.
20151 @item @code{!} --- extended mode
20152 @cindex @code{!} packet
20154 Enable extended mode. In extended mode, the remote server is made
20155 persistent. The @samp{R} packet is used to restart the program being
20161 The remote target both supports and has enabled extended mode.
20164 @item @code{?} --- last signal
20165 @cindex @code{?} packet
20167 Indicate the reason the target halted. The reply is the same as for
20171 @xref{Stop Reply Packets}, for the reply specifications.
20173 @item @code{a} --- reserved
20175 Reserved for future use.
20177 @item @code{A}@var{arglen}@code{,}@var{argnum}@code{,}@var{arg}@code{,@dots{}} --- set program arguments @strong{(reserved)}
20178 @cindex @code{A} packet
20180 Initialized @samp{argv[]} array passed into program. @var{arglen}
20181 specifies the number of bytes in the hex encoded byte stream @var{arg}.
20182 See @code{gdbserver} for more details.
20190 @item @code{b}@var{baud} --- set baud @strong{(deprecated)}
20191 @cindex @code{b} packet
20193 Change the serial line speed to @var{baud}.
20195 JTC: @emph{When does the transport layer state change? When it's
20196 received, or after the ACK is transmitted. In either case, there are
20197 problems if the command or the acknowledgment packet is dropped.}
20199 Stan: @emph{If people really wanted to add something like this, and get
20200 it working for the first time, they ought to modify ser-unix.c to send
20201 some kind of out-of-band message to a specially-setup stub and have the
20202 switch happen "in between" packets, so that from remote protocol's point
20203 of view, nothing actually happened.}
20205 @item @code{B}@var{addr},@var{mode} --- set breakpoint @strong{(deprecated)}
20206 @cindex @code{B} packet
20208 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
20209 breakpoint at @var{addr}.
20211 This packet has been replaced by the @samp{Z} and @samp{z} packets
20212 (@pxref{insert breakpoint or watchpoint packet}).
20214 @item @code{c}@var{addr} --- continue
20215 @cindex @code{c} packet
20217 @var{addr} is address to resume. If @var{addr} is omitted, resume at
20221 @xref{Stop Reply Packets}, for the reply specifications.
20223 @item @code{C}@var{sig}@code{;}@var{addr} --- continue with signal
20224 @cindex @code{C} packet
20226 Continue with signal @var{sig} (hex signal number). If
20227 @code{;}@var{addr} is omitted, resume at same address.
20230 @xref{Stop Reply Packets}, for the reply specifications.
20232 @item @code{d} --- toggle debug @strong{(deprecated)}
20233 @cindex @code{d} packet
20237 @item @code{D} --- detach
20238 @cindex @code{D} packet
20240 Detach @value{GDBN} from the remote system. Sent to the remote target
20241 before @value{GDBN} disconnects via the @code{detach} command.
20245 @item @emph{no response}
20246 @value{GDBN} does not check for any response after sending this packet.
20249 @item @code{e} --- reserved
20251 Reserved for future use.
20253 @item @code{E} --- reserved
20255 Reserved for future use.
20257 @item @code{f} --- reserved
20259 Reserved for future use.
20261 @item @code{F}@var{RC}@code{,}@var{EE}@code{,}@var{CF}@code{;}@var{XX} --- Reply to target's F packet.
20262 @cindex @code{F} packet
20264 This packet is send by @value{GDBN} as reply to a @code{F} request packet
20265 sent by the target. This is part of the File-I/O protocol extension.
20266 @xref{File-I/O remote protocol extension}, for the specification.
20268 @item @code{g} --- read registers
20269 @anchor{read registers packet}
20270 @cindex @code{g} packet
20272 Read general registers.
20276 @item @var{XX@dots{}}
20277 Each byte of register data is described by two hex digits. The bytes
20278 with the register are transmitted in target byte order. The size of
20279 each register and their position within the @samp{g} @var{packet} are
20280 determined by the @value{GDBN} internal macros
20281 @var{DEPRECATED_REGISTER_RAW_SIZE} and @var{REGISTER_NAME} macros. The
20282 specification of several standard @code{g} packets is specified below.
20287 @item @code{G}@var{XX@dots{}} --- write regs
20288 @cindex @code{G} packet
20290 @xref{read registers packet}, for a description of the @var{XX@dots{}}
20301 @item @code{h} --- reserved
20303 Reserved for future use.
20305 @item @code{H}@var{c}@var{t@dots{}} --- set thread
20306 @cindex @code{H} packet
20308 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
20309 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
20310 should be @samp{c} for step and continue operations, @samp{g} for other
20311 operations. The thread designator @var{t@dots{}} may be -1, meaning all
20312 the threads, a thread number, or zero which means pick any thread.
20323 @c 'H': How restrictive (or permissive) is the thread model. If a
20324 @c thread is selected and stopped, are other threads allowed
20325 @c to continue to execute? As I mentioned above, I think the
20326 @c semantics of each command when a thread is selected must be
20327 @c described. For example:
20329 @c 'g': If the stub supports threads and a specific thread is
20330 @c selected, returns the register block from that thread;
20331 @c otherwise returns current registers.
20333 @c 'G' If the stub supports threads and a specific thread is
20334 @c selected, sets the registers of the register block of
20335 @c that thread; otherwise sets current registers.
20337 @item @code{i}@var{addr}@code{,}@var{nnn} --- cycle step @strong{(draft)}
20338 @anchor{cycle step packet}
20339 @cindex @code{i} packet
20341 Step the remote target by a single clock cycle. If @code{,}@var{nnn} is
20342 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
20343 step starting at that address.
20345 @item @code{I} --- signal then cycle step @strong{(reserved)}
20346 @cindex @code{I} packet
20348 @xref{step with signal packet}. @xref{cycle step packet}.
20350 @item @code{j} --- reserved
20352 Reserved for future use.
20354 @item @code{J} --- reserved
20356 Reserved for future use.
20358 @item @code{k} --- kill request
20359 @cindex @code{k} packet
20361 FIXME: @emph{There is no description of how to operate when a specific
20362 thread context has been selected (i.e.@: does 'k' kill only that
20365 @item @code{K} --- reserved
20367 Reserved for future use.
20369 @item @code{l} --- reserved
20371 Reserved for future use.
20373 @item @code{L} --- reserved
20375 Reserved for future use.
20377 @item @code{m}@var{addr}@code{,}@var{length} --- read memory
20378 @cindex @code{m} packet
20380 Read @var{length} bytes of memory starting at address @var{addr}.
20381 Neither @value{GDBN} nor the stub assume that sized memory transfers are
20382 assumed using word aligned accesses. FIXME: @emph{A word aligned memory
20383 transfer mechanism is needed.}
20387 @item @var{XX@dots{}}
20388 @var{XX@dots{}} is mem contents. Can be fewer bytes than requested if able
20389 to read only part of the data. Neither @value{GDBN} nor the stub assume
20390 that sized memory transfers are assumed using word aligned
20391 accesses. FIXME: @emph{A word aligned memory transfer mechanism is
20397 @item @code{M}@var{addr},@var{length}@code{:}@var{XX@dots{}} --- write mem
20398 @cindex @code{M} packet
20400 Write @var{length} bytes of memory starting at address @var{addr}.
20401 @var{XX@dots{}} is the data.
20408 for an error (this includes the case where only part of the data was
20412 @item @code{n} --- reserved
20414 Reserved for future use.
20416 @item @code{N} --- reserved
20418 Reserved for future use.
20420 @item @code{o} --- reserved
20422 Reserved for future use.
20424 @item @code{O} --- reserved
20426 @item @code{p}@var{hex number of register} --- read register packet
20427 @cindex @code{p} packet
20429 @xref{read registers packet}, for a description of how the returned
20430 register value is encoded.
20434 @item @var{XX@dots{}}
20435 the register's value
20439 Indicating an unrecognized @var{query}.
20442 @item @code{P}@var{n@dots{}}@code{=}@var{r@dots{}} --- write register
20443 @anchor{write register packet}
20444 @cindex @code{P} packet
20446 Write register @var{n@dots{}} with value @var{r@dots{}}, which contains two hex
20447 digits for each byte in the register (target byte order).
20457 @item @code{q}@var{query} --- general query
20458 @anchor{general query packet}
20459 @cindex @code{q} packet
20461 Request info about @var{query}. In general @value{GDBN} queries have a
20462 leading upper case letter. Custom vendor queries should use a company
20463 prefix (in lower case) ex: @samp{qfsf.var}. @var{query} may optionally
20464 be followed by a @samp{,} or @samp{;} separated list. Stubs must ensure
20465 that they match the full @var{query} name.
20469 @item @var{XX@dots{}}
20470 Hex encoded data from query. The reply can not be empty.
20474 Indicating an unrecognized @var{query}.
20477 @item @code{Q}@var{var}@code{=}@var{val} --- general set
20478 @cindex @code{Q} packet
20480 Set value of @var{var} to @var{val}.
20482 @xref{general query packet}, for a discussion of naming conventions.
20484 @item @code{r} --- reset @strong{(deprecated)}
20485 @cindex @code{r} packet
20487 Reset the entire system.
20489 @item @code{R}@var{XX} --- remote restart
20490 @cindex @code{R} packet
20492 Restart the program being debugged. @var{XX}, while needed, is ignored.
20493 This packet is only available in extended mode.
20497 @item @emph{no reply}
20498 The @samp{R} packet has no reply.
20501 @item @code{s}@var{addr} --- step
20502 @cindex @code{s} packet
20504 @var{addr} is address to resume. If @var{addr} is omitted, resume at
20508 @xref{Stop Reply Packets}, for the reply specifications.
20510 @item @code{S}@var{sig}@code{;}@var{addr} --- step with signal
20511 @anchor{step with signal packet}
20512 @cindex @code{S} packet
20514 Like @samp{C} but step not continue.
20517 @xref{Stop Reply Packets}, for the reply specifications.
20519 @item @code{t}@var{addr}@code{:}@var{PP}@code{,}@var{MM} --- search
20520 @cindex @code{t} packet
20522 Search backwards starting at address @var{addr} for a match with pattern
20523 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
20524 @var{addr} must be at least 3 digits.
20526 @item @code{T}@var{XX} --- thread alive
20527 @cindex @code{T} packet
20529 Find out if the thread XX is alive.
20534 thread is still alive
20539 @item @code{u} --- reserved
20541 Reserved for future use.
20543 @item @code{U} --- reserved
20545 Reserved for future use.
20547 @item @code{v} --- verbose packet prefix
20549 Packets starting with @code{v} are identified by a multi-letter name,
20550 up to the first @code{;} or @code{?} (or the end of the packet).
20552 @item @code{vCont}[;@var{action}[@code{:}@var{tid}]]... --- extended resume
20553 @cindex @code{vCont} packet
20555 Resume the inferior. Different actions may be specified for each thread.
20556 If an action is specified with no @var{tid}, then it is applied to any
20557 threads that don't have a specific action specified; if no default action is
20558 specified then other threads should remain stopped. Specifying multiple
20559 default actions is an error; specifying no actions is also an error.
20560 Thread IDs are specified in hexadecimal. Currently supported actions are:
20566 Continue with signal @var{sig}. @var{sig} should be two hex digits.
20570 Step with signal @var{sig}. @var{sig} should be two hex digits.
20573 The optional @var{addr} argument normally associated with these packets is
20574 not supported in @code{vCont}.
20577 @xref{Stop Reply Packets}, for the reply specifications.
20579 @item @code{vCont?} --- extended resume query
20580 @cindex @code{vCont?} packet
20582 Query support for the @code{vCont} packet.
20586 @item @code{vCont}[;@var{action}]...
20587 The @code{vCont} packet is supported. Each @var{action} is a supported
20588 command in the @code{vCont} packet.
20590 The @code{vCont} packet is not supported.
20593 @item @code{V} --- reserved
20595 Reserved for future use.
20597 @item @code{w} --- reserved
20599 Reserved for future use.
20601 @item @code{W} --- reserved
20603 Reserved for future use.
20605 @item @code{x} --- reserved
20607 Reserved for future use.
20609 @item @code{X}@var{addr}@code{,}@var{length}@var{:}@var{XX@dots{}} --- write mem (binary)
20610 @cindex @code{X} packet
20612 @var{addr} is address, @var{length} is number of bytes, @var{XX@dots{}}
20613 is binary data. The characters @code{$}, @code{#}, and @code{0x7d} are
20614 escaped using @code{0x7d}, and then XORed with @code{0x20}.
20615 For example, @code{0x7d} would be transmitted as @code{0x7d 0x5d}.
20625 @item @code{y} --- reserved
20627 Reserved for future use.
20629 @item @code{Y} reserved
20631 Reserved for future use.
20633 @item @code{z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- remove breakpoint or watchpoint @strong{(draft)}
20634 @itemx @code{Z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- insert breakpoint or watchpoint @strong{(draft)}
20635 @anchor{insert breakpoint or watchpoint packet}
20636 @cindex @code{z} packet
20637 @cindex @code{Z} packets
20639 Insert (@code{Z}) or remove (@code{z}) a @var{type} breakpoint or
20640 watchpoint starting at address @var{address} and covering the next
20641 @var{length} bytes.
20643 Each breakpoint and watchpoint packet @var{type} is documented
20646 @emph{Implementation notes: A remote target shall return an empty string
20647 for an unrecognized breakpoint or watchpoint packet @var{type}. A
20648 remote target shall support either both or neither of a given
20649 @code{Z}@var{type}@dots{} and @code{z}@var{type}@dots{} packet pair. To
20650 avoid potential problems with duplicate packets, the operations should
20651 be implemented in an idempotent way.}
20653 @item @code{z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- remove memory breakpoint @strong{(draft)}
20654 @item @code{Z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- insert memory breakpoint @strong{(draft)}
20655 @cindex @code{z0} packet
20656 @cindex @code{Z0} packet
20658 Insert (@code{Z0}) or remove (@code{z0}) a memory breakpoint at address
20659 @code{addr} of size @code{length}.
20661 A memory breakpoint is implemented by replacing the instruction at
20662 @var{addr} with a software breakpoint or trap instruction. The
20663 @code{length} is used by targets that indicates the size of the
20664 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
20665 @sc{mips} can insert either a 2 or 4 byte breakpoint).
20667 @emph{Implementation note: It is possible for a target to copy or move
20668 code that contains memory breakpoints (e.g., when implementing
20669 overlays). The behavior of this packet, in the presence of such a
20670 target, is not defined.}
20682 @item @code{z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- remove hardware breakpoint @strong{(draft)}
20683 @item @code{Z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- insert hardware breakpoint @strong{(draft)}
20684 @cindex @code{z1} packet
20685 @cindex @code{Z1} packet
20687 Insert (@code{Z1}) or remove (@code{z1}) a hardware breakpoint at
20688 address @code{addr} of size @code{length}.
20690 A hardware breakpoint is implemented using a mechanism that is not
20691 dependant on being able to modify the target's memory.
20693 @emph{Implementation note: A hardware breakpoint is not affected by code
20706 @item @code{z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- remove write watchpoint @strong{(draft)}
20707 @item @code{Z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- insert write watchpoint @strong{(draft)}
20708 @cindex @code{z2} packet
20709 @cindex @code{Z2} packet
20711 Insert (@code{Z2}) or remove (@code{z2}) a write watchpoint.
20723 @item @code{z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- remove read watchpoint @strong{(draft)}
20724 @item @code{Z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- insert read watchpoint @strong{(draft)}
20725 @cindex @code{z3} packet
20726 @cindex @code{Z3} packet
20728 Insert (@code{Z3}) or remove (@code{z3}) a read watchpoint.
20740 @item @code{z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- remove access watchpoint @strong{(draft)}
20741 @item @code{Z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- insert access watchpoint @strong{(draft)}
20742 @cindex @code{z4} packet
20743 @cindex @code{Z4} packet
20745 Insert (@code{Z4}) or remove (@code{z4}) an access watchpoint.
20759 @node Stop Reply Packets
20760 @section Stop Reply Packets
20761 @cindex stop reply packets
20763 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
20764 receive any of the below as a reply. In the case of the @samp{C},
20765 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
20766 when the target halts. In the below the exact meaning of @samp{signal
20767 number} is poorly defined. In general one of the UNIX signal numbering
20768 conventions is used.
20773 @var{AA} is the signal number
20775 @item @code{T}@var{AA}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}
20776 @cindex @code{T} packet reply
20778 @var{AA} = two hex digit signal number; @var{n...} = register number
20779 (hex), @var{r...} = target byte ordered register contents, size defined
20780 by @code{DEPRECATED_REGISTER_RAW_SIZE}; @var{n...} = @samp{thread},
20781 @var{r...} = thread process ID, this is a hex integer; @var{n...} =
20782 (@samp{watch} | @samp{rwatch} | @samp{awatch}, @var{r...} = data
20783 address, this is a hex integer; @var{n...} = other string not starting
20784 with valid hex digit. @value{GDBN} should ignore this @var{n...},
20785 @var{r...} pair and go on to the next. This way we can extend the
20790 The process exited, and @var{AA} is the exit status. This is only
20791 applicable to certain targets.
20795 The process terminated with signal @var{AA}.
20797 @item O@var{XX@dots{}}
20799 @var{XX@dots{}} is hex encoding of @sc{ascii} data. This can happen at
20800 any time while the program is running and the debugger should continue
20801 to wait for @samp{W}, @samp{T}, etc.
20803 @item F@var{call-id}@code{,}@var{parameter@dots{}}
20805 @var{call-id} is the identifier which says which host system call should
20806 be called. This is just the name of the function. Translation into the
20807 correct system call is only applicable as it's defined in @value{GDBN}.
20808 @xref{File-I/O remote protocol extension}, for a list of implemented
20811 @var{parameter@dots{}} is a list of parameters as defined for this very
20814 The target replies with this packet when it expects @value{GDBN} to call
20815 a host system call on behalf of the target. @value{GDBN} replies with
20816 an appropriate @code{F} packet and keeps up waiting for the next reply
20817 packet from the target. The latest @samp{C}, @samp{c}, @samp{S} or
20818 @samp{s} action is expected to be continued.
20819 @xref{File-I/O remote protocol extension}, for more details.
20823 @node General Query Packets
20824 @section General Query Packets
20826 The following set and query packets have already been defined.
20830 @item @code{q}@code{C} --- current thread
20832 Return the current thread id.
20836 @item @code{QC}@var{pid}
20837 Where @var{pid} is an unsigned hexidecimal process id.
20839 Any other reply implies the old pid.
20842 @item @code{q}@code{fThreadInfo} -- all thread ids
20844 @code{q}@code{sThreadInfo}
20846 Obtain a list of active thread ids from the target (OS). Since there
20847 may be too many active threads to fit into one reply packet, this query
20848 works iteratively: it may require more than one query/reply sequence to
20849 obtain the entire list of threads. The first query of the sequence will
20850 be the @code{qf}@code{ThreadInfo} query; subsequent queries in the
20851 sequence will be the @code{qs}@code{ThreadInfo} query.
20853 NOTE: replaces the @code{qL} query (see below).
20857 @item @code{m}@var{id}
20859 @item @code{m}@var{id},@var{id}@dots{}
20860 a comma-separated list of thread ids
20862 (lower case 'el') denotes end of list.
20865 In response to each query, the target will reply with a list of one or
20866 more thread ids, in big-endian unsigned hex, separated by commas.
20867 @value{GDBN} will respond to each reply with a request for more thread
20868 ids (using the @code{qs} form of the query), until the target responds
20869 with @code{l} (lower-case el, for @code{'last'}).
20871 @item @code{q}@code{ThreadExtraInfo}@code{,}@var{id} --- extra thread info
20873 Where @var{id} is a thread-id in big-endian hex. Obtain a printable
20874 string description of a thread's attributes from the target OS. This
20875 string may contain anything that the target OS thinks is interesting for
20876 @value{GDBN} to tell the user about the thread. The string is displayed
20877 in @value{GDBN}'s @samp{info threads} display. Some examples of
20878 possible thread extra info strings are ``Runnable'', or ``Blocked on
20883 @item @var{XX@dots{}}
20884 Where @var{XX@dots{}} is a hex encoding of @sc{ascii} data, comprising
20885 the printable string containing the extra information about the thread's
20889 @item @code{q}@code{L}@var{startflag}@var{threadcount}@var{nextthread} --- query @var{LIST} or @var{threadLIST} @strong{(deprecated)}
20891 Obtain thread information from RTOS. Where: @var{startflag} (one hex
20892 digit) is one to indicate the first query and zero to indicate a
20893 subsequent query; @var{threadcount} (two hex digits) is the maximum
20894 number of threads the response packet can contain; and @var{nextthread}
20895 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
20896 returned in the response as @var{argthread}.
20898 NOTE: this query is replaced by the @code{q}@code{fThreadInfo} query
20903 @item @code{q}@code{M}@var{count}@var{done}@var{argthread}@var{thread@dots{}}
20904 Where: @var{count} (two hex digits) is the number of threads being
20905 returned; @var{done} (one hex digit) is zero to indicate more threads
20906 and one indicates no further threads; @var{argthreadid} (eight hex
20907 digits) is @var{nextthread} from the request packet; @var{thread@dots{}}
20908 is a sequence of thread IDs from the target. @var{threadid} (eight hex
20909 digits). See @code{remote.c:parse_threadlist_response()}.
20912 @item @code{q}@code{CRC:}@var{addr}@code{,}@var{length} --- compute CRC of memory block
20916 @item @code{E}@var{NN}
20917 An error (such as memory fault)
20918 @item @code{C}@var{CRC32}
20919 A 32 bit cyclic redundancy check of the specified memory region.
20922 @item @code{q}@code{Offsets} --- query sect offs
20924 Get section offsets that the target used when re-locating the downloaded
20925 image. @emph{Note: while a @code{Bss} offset is included in the
20926 response, @value{GDBN} ignores this and instead applies the @code{Data}
20927 offset to the @code{Bss} section.}
20931 @item @code{Text=}@var{xxx}@code{;Data=}@var{yyy}@code{;Bss=}@var{zzz}
20934 @item @code{q}@code{P}@var{mode}@var{threadid} --- thread info request
20936 Returns information on @var{threadid}. Where: @var{mode} is a hex
20937 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
20944 See @code{remote.c:remote_unpack_thread_info_response()}.
20946 @item @code{q}@code{Rcmd,}@var{command} --- remote command
20948 @var{command} (hex encoded) is passed to the local interpreter for
20949 execution. Invalid commands should be reported using the output string.
20950 Before the final result packet, the target may also respond with a
20951 number of intermediate @code{O}@var{output} console output packets.
20952 @emph{Implementors should note that providing access to a stubs's
20953 interpreter may have security implications}.
20958 A command response with no output.
20960 A command response with the hex encoded output string @var{OUTPUT}.
20961 @item @code{E}@var{NN}
20962 Indicate a badly formed request.
20964 When @samp{q}@samp{Rcmd} is not recognized.
20967 @item @code{qSymbol::} --- symbol lookup
20969 Notify the target that @value{GDBN} is prepared to serve symbol lookup
20970 requests. Accept requests from the target for the values of symbols.
20975 The target does not need to look up any (more) symbols.
20976 @item @code{qSymbol:}@var{sym_name}
20977 The target requests the value of symbol @var{sym_name} (hex encoded).
20978 @value{GDBN} may provide the value by using the
20979 @code{qSymbol:}@var{sym_value}:@var{sym_name} message, described below.
20982 @item @code{qSymbol:}@var{sym_value}:@var{sym_name} --- symbol value
20984 Set the value of @var{sym_name} to @var{sym_value}.
20986 @var{sym_name} (hex encoded) is the name of a symbol whose value the
20987 target has previously requested.
20989 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
20990 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
20996 The target does not need to look up any (more) symbols.
20997 @item @code{qSymbol:}@var{sym_name}
20998 The target requests the value of a new symbol @var{sym_name} (hex
20999 encoded). @value{GDBN} will continue to supply the values of symbols
21000 (if available), until the target ceases to request them.
21003 @item @code{qPart}:@var{object}:@code{read}:@var{annex}:@var{offset},@var{length} --- read special data
21005 Read uninterpreted bytes from the target's special data area
21006 identified by the keyword @code{object}.
21007 Request @var{length} bytes starting at @var{offset} bytes into the data.
21008 The content and encoding of @var{annex} is specific to the object;
21009 it can supply additional details about what data to access.
21011 Here are the specific requests of this form defined so far.
21012 All @samp{@code{qPart}:@var{object}:@code{read}:@dots{}}
21013 requests use the same reply formats, listed below.
21016 @item @code{qPart}:@code{auxv}:@code{read}::@var{offset},@var{length}
21017 Access the target's @dfn{auxiliary vector}. @xref{Auxiliary Vector}.
21018 Note @var{annex} must be empty.
21024 The @var{offset} in the request is at the end of the data.
21025 There is no more data to be read.
21027 @item @var{XX@dots{}}
21028 Hex encoded data bytes read.
21029 This may be fewer bytes than the @var{length} in the request.
21032 The request was malformed, or @var{annex} was invalid.
21034 @item @code{E}@var{nn}
21035 The offset was invalid, or there was an error encountered reading the data.
21036 @var{nn} is a hex-encoded @code{errno} value.
21038 @item @code{""} (empty)
21039 An empty reply indicates the @var{object} or @var{annex} string was not
21040 recognized by the stub.
21043 @item @code{qPart}:@var{object}:@code{write}:@var{annex}:@var{offset}:@var{data@dots{}}
21045 Write uninterpreted bytes into the target's special data area
21046 identified by the keyword @code{object},
21047 starting at @var{offset} bytes into the data.
21048 @var{data@dots{}} is the hex-encoded data to be written.
21049 The content and encoding of @var{annex} is specific to the object;
21050 it can supply additional details about what data to access.
21052 No requests of this form are presently in use. This specification
21053 serves as a placeholder to document the common format that new
21054 specific request specifications ought to use.
21059 @var{nn} (hex encoded) is the number of bytes written.
21060 This may be fewer bytes than supplied in the request.
21063 The request was malformed, or @var{annex} was invalid.
21065 @item @code{E}@var{nn}
21066 The offset was invalid, or there was an error encountered writing the data.
21067 @var{nn} is a hex-encoded @code{errno} value.
21069 @item @code{""} (empty)
21070 An empty reply indicates the @var{object} or @var{annex} string was not
21071 recognized by the stub, or that the object does not support writing.
21074 @item @code{qPart}:@var{object}:@var{operation}:@dots{}
21075 Requests of this form may be added in the future. When a stub does
21076 not recognize the @var{object} keyword, or its support for
21077 @var{object} does not recognize the @var{operation} keyword,
21078 the stub must respond with an empty packet.
21081 @node Register Packet Format
21082 @section Register Packet Format
21084 The following @samp{g}/@samp{G} packets have previously been defined.
21085 In the below, some thirty-two bit registers are transferred as
21086 sixty-four bits. Those registers should be zero/sign extended (which?)
21087 to fill the space allocated. Register bytes are transfered in target
21088 byte order. The two nibbles within a register byte are transfered
21089 most-significant - least-significant.
21095 All registers are transfered as thirty-two bit quantities in the order:
21096 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
21097 registers; fsr; fir; fp.
21101 All registers are transfered as sixty-four bit quantities (including
21102 thirty-two bit registers such as @code{sr}). The ordering is the same
21110 Example sequence of a target being re-started. Notice how the restart
21111 does not get any direct output:
21116 @emph{target restarts}
21119 <- @code{T001:1234123412341234}
21123 Example sequence of a target being stepped by a single instruction:
21126 -> @code{G1445@dots{}}
21131 <- @code{T001:1234123412341234}
21135 <- @code{1455@dots{}}
21139 @node File-I/O remote protocol extension
21140 @section File-I/O remote protocol extension
21141 @cindex File-I/O remote protocol extension
21144 * File-I/O Overview::
21145 * Protocol basics::
21146 * The F request packet::
21147 * The F reply packet::
21148 * Memory transfer::
21149 * The Ctrl-C message::
21151 * The isatty call::
21152 * The system call::
21153 * List of supported calls::
21154 * Protocol specific representation of datatypes::
21156 * File-I/O Examples::
21159 @node File-I/O Overview
21160 @subsection File-I/O Overview
21161 @cindex file-i/o overview
21163 The File I/O remote protocol extension (short: File-I/O) allows the
21164 target to use the hosts file system and console I/O when calling various
21165 system calls. System calls on the target system are translated into a
21166 remote protocol packet to the host system which then performs the needed
21167 actions and returns with an adequate response packet to the target system.
21168 This simulates file system operations even on targets that lack file systems.
21170 The protocol is defined host- and target-system independent. It uses
21171 it's own independent representation of datatypes and values. Both,
21172 @value{GDBN} and the target's @value{GDBN} stub are responsible for
21173 translating the system dependent values into the unified protocol values
21174 when data is transmitted.
21176 The communication is synchronous. A system call is possible only
21177 when GDB is waiting for the @samp{C}, @samp{c}, @samp{S} or @samp{s}
21178 packets. While @value{GDBN} handles the request for a system call,
21179 the target is stopped to allow deterministic access to the target's
21180 memory. Therefore File-I/O is not interuptible by target signals. It
21181 is possible to interrupt File-I/O by a user interrupt (Ctrl-C), though.
21183 The target's request to perform a host system call does not finish
21184 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
21185 after finishing the system call, the target returns to continuing the
21186 previous activity (continue, step). No additional continue or step
21187 request from @value{GDBN} is required.
21190 (@value{GDBP}) continue
21191 <- target requests 'system call X'
21192 target is stopped, @value{GDBN} executes system call
21193 -> GDB returns result
21194 ... target continues, GDB returns to wait for the target
21195 <- target hits breakpoint and sends a Txx packet
21198 The protocol is only used for files on the host file system and
21199 for I/O on the console. Character or block special devices, pipes,
21200 named pipes or sockets or any other communication method on the host
21201 system are not supported by this protocol.
21203 @node Protocol basics
21204 @subsection Protocol basics
21205 @cindex protocol basics, file-i/o
21207 The File-I/O protocol uses the @code{F} packet, as request as well
21208 as as reply packet. Since a File-I/O system call can only occur when
21209 @value{GDBN} is waiting for the continuing or stepping target, the
21210 File-I/O request is a reply that @value{GDBN} has to expect as a result
21211 of a former @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
21212 This @code{F} packet contains all information needed to allow @value{GDBN}
21213 to call the appropriate host system call:
21217 A unique identifier for the requested system call.
21220 All parameters to the system call. Pointers are given as addresses
21221 in the target memory address space. Pointers to strings are given as
21222 pointer/length pair. Numerical values are given as they are.
21223 Numerical control values are given in a protocol specific representation.
21227 At that point @value{GDBN} has to perform the following actions.
21231 If parameter pointer values are given, which point to data needed as input
21232 to a system call, @value{GDBN} requests this data from the target with a
21233 standard @code{m} packet request. This additional communication has to be
21234 expected by the target implementation and is handled as any other @code{m}
21238 @value{GDBN} translates all value from protocol representation to host
21239 representation as needed. Datatypes are coerced into the host types.
21242 @value{GDBN} calls the system call
21245 It then coerces datatypes back to protocol representation.
21248 If pointer parameters in the request packet point to buffer space in which
21249 a system call is expected to copy data to, the data is transmitted to the
21250 target using a @code{M} or @code{X} packet. This packet has to be expected
21251 by the target implementation and is handled as any other @code{M} or @code{X}
21256 Eventually @value{GDBN} replies with another @code{F} packet which contains all
21257 necessary information for the target to continue. This at least contains
21264 @code{errno}, if has been changed by the system call.
21271 After having done the needed type and value coercion, the target continues
21272 the latest continue or step action.
21274 @node The F request packet
21275 @subsection The @code{F} request packet
21276 @cindex file-i/o request packet
21277 @cindex @code{F} request packet
21279 The @code{F} request packet has the following format:
21284 @code{F}@var{call-id}@code{,}@var{parameter@dots{}}
21287 @var{call-id} is the identifier to indicate the host system call to be called.
21288 This is just the name of the function.
21290 @var{parameter@dots{}} are the parameters to the system call.
21294 Parameters are hexadecimal integer values, either the real values in case
21295 of scalar datatypes, as pointers to target buffer space in case of compound
21296 datatypes and unspecified memory areas or as pointer/length pairs in case
21297 of string parameters. These are appended to the call-id, each separated
21298 from its predecessor by a comma. All values are transmitted in ASCII
21299 string representation, pointer/length pairs separated by a slash.
21301 @node The F reply packet
21302 @subsection The @code{F} reply packet
21303 @cindex file-i/o reply packet
21304 @cindex @code{F} reply packet
21306 The @code{F} reply packet has the following format:
21311 @code{F}@var{retcode}@code{,}@var{errno}@code{,}@var{Ctrl-C flag}@code{;}@var{call specific attachment}
21314 @var{retcode} is the return code of the system call as hexadecimal value.
21316 @var{errno} is the errno set by the call, in protocol specific representation.
21317 This parameter can be omitted if the call was successful.
21319 @var{Ctrl-C flag} is only send if the user requested a break. In this
21320 case, @var{errno} must be send as well, even if the call was successful.
21321 The @var{Ctrl-C flag} itself consists of the character 'C':
21328 or, if the call was interupted before the host call has been performed:
21335 assuming 4 is the protocol specific representation of @code{EINTR}.
21339 @node Memory transfer
21340 @subsection Memory transfer
21341 @cindex memory transfer, in file-i/o protocol
21343 Structured data which is transferred using a memory read or write as e.g.@:
21344 a @code{struct stat} is expected to be in a protocol specific format with
21345 all scalar multibyte datatypes being big endian. This should be done by
21346 the target before the @code{F} packet is sent resp.@: by @value{GDBN} before
21347 it transfers memory to the target. Transferred pointers to structured
21348 data should point to the already coerced data at any time.
21350 @node The Ctrl-C message
21351 @subsection The Ctrl-C message
21352 @cindex ctrl-c message, in file-i/o protocol
21354 A special case is, if the @var{Ctrl-C flag} is set in the @value{GDBN}
21355 reply packet. In this case the target should behave, as if it had
21356 gotten a break message. The meaning for the target is ``system call
21357 interupted by @code{SIGINT}''. Consequentially, the target should actually stop
21358 (as with a break message) and return to @value{GDBN} with a @code{T02}
21359 packet. In this case, it's important for the target to know, in which
21360 state the system call was interrupted. Since this action is by design
21361 not an atomic operation, we have to differ between two cases:
21365 The system call hasn't been performed on the host yet.
21368 The system call on the host has been finished.
21372 These two states can be distinguished by the target by the value of the
21373 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
21374 call hasn't been performed. This is equivalent to the @code{EINTR} handling
21375 on POSIX systems. In any other case, the target may presume that the
21376 system call has been finished --- successful or not --- and should behave
21377 as if the break message arrived right after the system call.
21379 @value{GDBN} must behave reliable. If the system call has not been called
21380 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
21381 @code{errno} in the packet. If the system call on the host has been finished
21382 before the user requests a break, the full action must be finshed by
21383 @value{GDBN}. This requires sending @code{M} or @code{X} packets as they fit.
21384 The @code{F} packet may only be send when either nothing has happened
21385 or the full action has been completed.
21388 @subsection Console I/O
21389 @cindex console i/o as part of file-i/o
21391 By default and if not explicitely closed by the target system, the file
21392 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
21393 on the @value{GDBN} console is handled as any other file output operation
21394 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
21395 by @value{GDBN} so that after the target read request from file descriptor
21396 0 all following typing is buffered until either one of the following
21401 The user presses @kbd{Ctrl-C}. The behaviour is as explained above, the
21403 system call is treated as finished.
21406 The user presses @kbd{Enter}. This is treated as end of input with a trailing
21410 The user presses @kbd{Ctrl-D}. This is treated as end of input. No trailing
21411 character, especially no Ctrl-D is appended to the input.
21415 If the user has typed more characters as fit in the buffer given to
21416 the read call, the trailing characters are buffered in @value{GDBN} until
21417 either another @code{read(0, @dots{})} is requested by the target or debugging
21418 is stopped on users request.
21420 @node The isatty call
21421 @subsection The isatty(3) call
21422 @cindex isatty call, file-i/o protocol
21424 A special case in this protocol is the library call @code{isatty} which
21425 is implemented as it's own call inside of this protocol. It returns
21426 1 to the target if the file descriptor given as parameter is attached
21427 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
21428 would require implementing @code{ioctl} and would be more complex than
21431 @node The system call
21432 @subsection The system(3) call
21433 @cindex system call, file-i/o protocol
21435 The other special case in this protocol is the @code{system} call which
21436 is implemented as it's own call, too. @value{GDBN} is taking over the full
21437 task of calling the necessary host calls to perform the @code{system}
21438 call. The return value of @code{system} is simplified before it's returned
21439 to the target. Basically, the only signal transmitted back is @code{EINTR}
21440 in case the user pressed @kbd{Ctrl-C}. Otherwise the return value consists
21441 entirely of the exit status of the called command.
21443 Due to security concerns, the @code{system} call is refused to be called
21444 by @value{GDBN} by default. The user has to allow this call explicitly by
21448 @kindex set remote system-call-allowed 1
21449 @item @code{set remote system-call-allowed 1}
21452 Disabling the @code{system} call is done by
21455 @kindex set remote system-call-allowed 0
21456 @item @code{set remote system-call-allowed 0}
21459 The current setting is shown by typing
21462 @kindex show remote system-call-allowed
21463 @item @code{show remote system-call-allowed}
21466 @node List of supported calls
21467 @subsection List of supported calls
21468 @cindex list of supported file-i/o calls
21485 @unnumberedsubsubsec open
21486 @cindex open, file-i/o system call
21490 int open(const char *pathname, int flags);
21491 int open(const char *pathname, int flags, mode_t mode);
21494 Fopen,pathptr/len,flags,mode
21498 @code{flags} is the bitwise or of the following values:
21502 If the file does not exist it will be created. The host
21503 rules apply as far as file ownership and time stamps
21507 When used with O_CREAT, if the file already exists it is
21508 an error and open() fails.
21511 If the file already exists and the open mode allows
21512 writing (O_RDWR or O_WRONLY is given) it will be
21513 truncated to length 0.
21516 The file is opened in append mode.
21519 The file is opened for reading only.
21522 The file is opened for writing only.
21525 The file is opened for reading and writing.
21528 Each other bit is silently ignored.
21533 @code{mode} is the bitwise or of the following values:
21537 User has read permission.
21540 User has write permission.
21543 Group has read permission.
21546 Group has write permission.
21549 Others have read permission.
21552 Others have write permission.
21555 Each other bit is silently ignored.
21560 @exdent Return value:
21561 open returns the new file descriptor or -1 if an error
21569 pathname already exists and O_CREAT and O_EXCL were used.
21572 pathname refers to a directory.
21575 The requested access is not allowed.
21578 pathname was too long.
21581 A directory component in pathname does not exist.
21584 pathname refers to a device, pipe, named pipe or socket.
21587 pathname refers to a file on a read-only filesystem and
21588 write access was requested.
21591 pathname is an invalid pointer value.
21594 No space on device to create the file.
21597 The process already has the maximum number of files open.
21600 The limit on the total number of files open on the system
21604 The call was interrupted by the user.
21608 @unnumberedsubsubsec close
21609 @cindex close, file-i/o system call
21618 @exdent Return value:
21619 close returns zero on success, or -1 if an error occurred.
21626 fd isn't a valid open file descriptor.
21629 The call was interrupted by the user.
21633 @unnumberedsubsubsec read
21634 @cindex read, file-i/o system call
21638 int read(int fd, void *buf, unsigned int count);
21641 Fread,fd,bufptr,count
21643 @exdent Return value:
21644 On success, the number of bytes read is returned.
21645 Zero indicates end of file. If count is zero, read
21646 returns zero as well. On error, -1 is returned.
21653 fd is not a valid file descriptor or is not open for
21657 buf is an invalid pointer value.
21660 The call was interrupted by the user.
21664 @unnumberedsubsubsec write
21665 @cindex write, file-i/o system call
21669 int write(int fd, const void *buf, unsigned int count);
21672 Fwrite,fd,bufptr,count
21674 @exdent Return value:
21675 On success, the number of bytes written are returned.
21676 Zero indicates nothing was written. On error, -1
21684 fd is not a valid file descriptor or is not open for
21688 buf is an invalid pointer value.
21691 An attempt was made to write a file that exceeds the
21692 host specific maximum file size allowed.
21695 No space on device to write the data.
21698 The call was interrupted by the user.
21702 @unnumberedsubsubsec lseek
21703 @cindex lseek, file-i/o system call
21707 long lseek (int fd, long offset, int flag);
21710 Flseek,fd,offset,flag
21713 @code{flag} is one of:
21717 The offset is set to offset bytes.
21720 The offset is set to its current location plus offset
21724 The offset is set to the size of the file plus offset
21729 @exdent Return value:
21730 On success, the resulting unsigned offset in bytes from
21731 the beginning of the file is returned. Otherwise, a
21732 value of -1 is returned.
21739 fd is not a valid open file descriptor.
21742 fd is associated with the @value{GDBN} console.
21745 flag is not a proper value.
21748 The call was interrupted by the user.
21752 @unnumberedsubsubsec rename
21753 @cindex rename, file-i/o system call
21757 int rename(const char *oldpath, const char *newpath);
21760 Frename,oldpathptr/len,newpathptr/len
21762 @exdent Return value:
21763 On success, zero is returned. On error, -1 is returned.
21770 newpath is an existing directory, but oldpath is not a
21774 newpath is a non-empty directory.
21777 oldpath or newpath is a directory that is in use by some
21781 An attempt was made to make a directory a subdirectory
21785 A component used as a directory in oldpath or new
21786 path is not a directory. Or oldpath is a directory
21787 and newpath exists but is not a directory.
21790 oldpathptr or newpathptr are invalid pointer values.
21793 No access to the file or the path of the file.
21797 oldpath or newpath was too long.
21800 A directory component in oldpath or newpath does not exist.
21803 The file is on a read-only filesystem.
21806 The device containing the file has no room for the new
21810 The call was interrupted by the user.
21814 @unnumberedsubsubsec unlink
21815 @cindex unlink, file-i/o system call
21819 int unlink(const char *pathname);
21822 Funlink,pathnameptr/len
21824 @exdent Return value:
21825 On success, zero is returned. On error, -1 is returned.
21832 No access to the file or the path of the file.
21835 The system does not allow unlinking of directories.
21838 The file pathname cannot be unlinked because it's
21839 being used by another process.
21842 pathnameptr is an invalid pointer value.
21845 pathname was too long.
21848 A directory component in pathname does not exist.
21851 A component of the path is not a directory.
21854 The file is on a read-only filesystem.
21857 The call was interrupted by the user.
21861 @unnumberedsubsubsec stat/fstat
21862 @cindex fstat, file-i/o system call
21863 @cindex stat, file-i/o system call
21867 int stat(const char *pathname, struct stat *buf);
21868 int fstat(int fd, struct stat *buf);
21871 Fstat,pathnameptr/len,bufptr
21874 @exdent Return value:
21875 On success, zero is returned. On error, -1 is returned.
21882 fd is not a valid open file.
21885 A directory component in pathname does not exist or the
21886 path is an empty string.
21889 A component of the path is not a directory.
21892 pathnameptr is an invalid pointer value.
21895 No access to the file or the path of the file.
21898 pathname was too long.
21901 The call was interrupted by the user.
21905 @unnumberedsubsubsec gettimeofday
21906 @cindex gettimeofday, file-i/o system call
21910 int gettimeofday(struct timeval *tv, void *tz);
21913 Fgettimeofday,tvptr,tzptr
21915 @exdent Return value:
21916 On success, 0 is returned, -1 otherwise.
21923 tz is a non-NULL pointer.
21926 tvptr and/or tzptr is an invalid pointer value.
21930 @unnumberedsubsubsec isatty
21931 @cindex isatty, file-i/o system call
21935 int isatty(int fd);
21940 @exdent Return value:
21941 Returns 1 if fd refers to the @value{GDBN} console, 0 otherwise.
21948 The call was interrupted by the user.
21952 @unnumberedsubsubsec system
21953 @cindex system, file-i/o system call
21957 int system(const char *command);
21960 Fsystem,commandptr/len
21962 @exdent Return value:
21963 The value returned is -1 on error and the return status
21964 of the command otherwise. Only the exit status of the
21965 command is returned, which is extracted from the hosts
21966 system return value by calling WEXITSTATUS(retval).
21967 In case /bin/sh could not be executed, 127 is returned.
21974 The call was interrupted by the user.
21977 @node Protocol specific representation of datatypes
21978 @subsection Protocol specific representation of datatypes
21979 @cindex protocol specific representation of datatypes, in file-i/o protocol
21982 * Integral datatypes::
21988 @node Integral datatypes
21989 @unnumberedsubsubsec Integral datatypes
21990 @cindex integral datatypes, in file-i/o protocol
21992 The integral datatypes used in the system calls are
21995 int@r{,} unsigned int@r{,} long@r{,} unsigned long@r{,} mode_t @r{and} time_t
21998 @code{Int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
21999 implemented as 32 bit values in this protocol.
22001 @code{Long} and @code{unsigned long} are implemented as 64 bit types.
22003 @xref{Limits}, for corresponding MIN and MAX values (similar to those
22004 in @file{limits.h}) to allow range checking on host and target.
22006 @code{time_t} datatypes are defined as seconds since the Epoch.
22008 All integral datatypes transferred as part of a memory read or write of a
22009 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
22012 @node Pointer values
22013 @unnumberedsubsubsec Pointer values
22014 @cindex pointer values, in file-i/o protocol
22016 Pointers to target data are transmitted as they are. An exception
22017 is made for pointers to buffers for which the length isn't
22018 transmitted as part of the function call, namely strings. Strings
22019 are transmitted as a pointer/length pair, both as hex values, e.g.@:
22026 which is a pointer to data of length 18 bytes at position 0x1aaf.
22027 The length is defined as the full string length in bytes, including
22028 the trailing null byte. Example:
22031 ``hello, world'' at address 0x123456
22042 @unnumberedsubsubsec struct stat
22043 @cindex struct stat, in file-i/o protocol
22045 The buffer of type struct stat used by the target and @value{GDBN} is defined
22050 unsigned int st_dev; /* device */
22051 unsigned int st_ino; /* inode */
22052 mode_t st_mode; /* protection */
22053 unsigned int st_nlink; /* number of hard links */
22054 unsigned int st_uid; /* user ID of owner */
22055 unsigned int st_gid; /* group ID of owner */
22056 unsigned int st_rdev; /* device type (if inode device) */
22057 unsigned long st_size; /* total size, in bytes */
22058 unsigned long st_blksize; /* blocksize for filesystem I/O */
22059 unsigned long st_blocks; /* number of blocks allocated */
22060 time_t st_atime; /* time of last access */
22061 time_t st_mtime; /* time of last modification */
22062 time_t st_ctime; /* time of last change */
22066 The integral datatypes are conforming to the definitions given in the
22067 approriate section (see @ref{Integral datatypes}, for details) so this
22068 structure is of size 64 bytes.
22070 The values of several fields have a restricted meaning and/or
22077 st_ino: No valid meaning for the target. Transmitted unchanged.
22079 st_mode: Valid mode bits are described in Appendix C. Any other
22080 bits have currently no meaning for the target.
22082 st_uid: No valid meaning for the target. Transmitted unchanged.
22084 st_gid: No valid meaning for the target. Transmitted unchanged.
22086 st_rdev: No valid meaning for the target. Transmitted unchanged.
22088 st_atime, st_mtime, st_ctime:
22089 These values have a host and file system dependent
22090 accuracy. Especially on Windows hosts the file systems
22091 don't support exact timing values.
22094 The target gets a struct stat of the above representation and is
22095 responsible to coerce it to the target representation before
22098 Note that due to size differences between the host and target
22099 representation of stat members, these members could eventually
22100 get truncated on the target.
22102 @node struct timeval
22103 @unnumberedsubsubsec struct timeval
22104 @cindex struct timeval, in file-i/o protocol
22106 The buffer of type struct timeval used by the target and @value{GDBN}
22107 is defined as follows:
22111 time_t tv_sec; /* second */
22112 long tv_usec; /* microsecond */
22116 The integral datatypes are conforming to the definitions given in the
22117 approriate section (see @ref{Integral datatypes}, for details) so this
22118 structure is of size 8 bytes.
22121 @subsection Constants
22122 @cindex constants, in file-i/o protocol
22124 The following values are used for the constants inside of the
22125 protocol. @value{GDBN} and target are resposible to translate these
22126 values before and after the call as needed.
22137 @unnumberedsubsubsec Open flags
22138 @cindex open flags, in file-i/o protocol
22140 All values are given in hexadecimal representation.
22152 @node mode_t values
22153 @unnumberedsubsubsec mode_t values
22154 @cindex mode_t values, in file-i/o protocol
22156 All values are given in octal representation.
22173 @unnumberedsubsubsec Errno values
22174 @cindex errno values, in file-i/o protocol
22176 All values are given in decimal representation.
22201 EUNKNOWN is used as a fallback error value if a host system returns
22202 any error value not in the list of supported error numbers.
22205 @unnumberedsubsubsec Lseek flags
22206 @cindex lseek flags, in file-i/o protocol
22215 @unnumberedsubsubsec Limits
22216 @cindex limits, in file-i/o protocol
22218 All values are given in decimal representation.
22221 INT_MIN -2147483648
22223 UINT_MAX 4294967295
22224 LONG_MIN -9223372036854775808
22225 LONG_MAX 9223372036854775807
22226 ULONG_MAX 18446744073709551615
22229 @node File-I/O Examples
22230 @subsection File-I/O Examples
22231 @cindex file-i/o examples
22233 Example sequence of a write call, file descriptor 3, buffer is at target
22234 address 0x1234, 6 bytes should be written:
22237 <- @code{Fwrite,3,1234,6}
22238 @emph{request memory read from target}
22241 @emph{return "6 bytes written"}
22245 Example sequence of a read call, file descriptor 3, buffer is at target
22246 address 0x1234, 6 bytes should be read:
22249 <- @code{Fread,3,1234,6}
22250 @emph{request memory write to target}
22251 -> @code{X1234,6:XXXXXX}
22252 @emph{return "6 bytes read"}
22256 Example sequence of a read call, call fails on the host due to invalid
22257 file descriptor (EBADF):
22260 <- @code{Fread,3,1234,6}
22264 Example sequence of a read call, user presses Ctrl-C before syscall on
22268 <- @code{Fread,3,1234,6}
22273 Example sequence of a read call, user presses Ctrl-C after syscall on
22277 <- @code{Fread,3,1234,6}
22278 -> @code{X1234,6:XXXXXX}
22282 @include agentexpr.texi
22296 % I think something like @colophon should be in texinfo. In the
22298 \long\def\colophon{\hbox to0pt{}\vfill
22299 \centerline{The body of this manual is set in}
22300 \centerline{\fontname\tenrm,}
22301 \centerline{with headings in {\bf\fontname\tenbf}}
22302 \centerline{and examples in {\tt\fontname\tentt}.}
22303 \centerline{{\it\fontname\tenit\/},}
22304 \centerline{{\bf\fontname\tenbf}, and}
22305 \centerline{{\sl\fontname\tensl\/}}
22306 \centerline{are used for emphasis.}\vfill}
22308 % Blame: doc@cygnus.com, 1991.