1 \input texinfo @c -*-texinfo-*-
2 @c Copyright 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
3 @c 1999, 2000, 2001, 2002, 2003, 2004
4 @c Free Software Foundation, Inc.
7 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
8 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
25 @c readline appendices use @vindex, @findex and @ftable,
26 @c annotate.texi and gdbmi use @findex.
30 @c !!set GDB manual's edition---not the same as GDB version!
31 @c This is updated by GNU Press.
34 @c !!set GDB edit command default editor
37 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
39 @c This is a dir.info fragment to support semi-automated addition of
40 @c manuals to an info tree.
41 @dircategory Software development
43 * Gdb: (gdb). The GNU debugger.
47 This file documents the @sc{gnu} debugger @value{GDBN}.
50 This is the @value{EDITION} Edition, of @cite{Debugging with
51 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
52 Version @value{GDBVN}.
54 Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,@*
55 1999, 2000, 2001, 2002, 2003, 2004 Free Software Foundation, Inc.
57 Permission is granted to copy, distribute and/or modify this document
58 under the terms of the GNU Free Documentation License, Version 1.1 or
59 any later version published by the Free Software Foundation; with the
60 Invariant Sections being ``Free Software'' and ``Free Software Needs
61 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
62 and with the Back-Cover Texts as in (a) below.
64 (a) The Free Software Foundation's Back-Cover Text is: ``You have
65 freedom to copy and modify this GNU Manual, like GNU software. Copies
66 published by the Free Software Foundation raise funds for GNU
71 @title Debugging with @value{GDBN}
72 @subtitle The @sc{gnu} Source-Level Debugger
74 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
75 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
79 \hfill (Send bugs and comments on @value{GDBN} to bug-gdb\@gnu.org.)\par
80 \hfill {\it Debugging with @value{GDBN}}\par
81 \hfill \TeX{}info \texinfoversion\par
85 @vskip 0pt plus 1filll
86 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
87 1996, 1998, 1999, 2000, 2001, 2002, 2003, 2004 Free Software Foundation, Inc.
89 Published by the Free Software Foundation @*
90 59 Temple Place - Suite 330, @*
91 Boston, MA 02111-1307 USA @*
94 Permission is granted to copy, distribute and/or modify this document
95 under the terms of the GNU Free Documentation License, Version 1.1 or
96 any later version published by the Free Software Foundation; with the
97 Invariant Sections being ``Free Software'' and ``Free Software Needs
98 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
99 and with the Back-Cover Texts as in (a) below.
101 (a) The Free Software Foundation's Back-Cover Text is: ``You have
102 freedom to copy and modify this GNU Manual, like GNU software. Copies
103 published by the Free Software Foundation raise funds for GNU
109 @node Top, Summary, (dir), (dir)
111 @top Debugging with @value{GDBN}
113 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
115 This is the @value{EDITION} Edition, for @value{GDBN} Version
118 Copyright (C) 1988-2004 Free Software Foundation, Inc.
121 * Summary:: Summary of @value{GDBN}
122 * Sample Session:: A sample @value{GDBN} session
124 * Invocation:: Getting in and out of @value{GDBN}
125 * Commands:: @value{GDBN} commands
126 * Running:: Running programs under @value{GDBN}
127 * Stopping:: Stopping and continuing
128 * Stack:: Examining the stack
129 * Source:: Examining source files
130 * Data:: Examining data
131 * Macros:: Preprocessor Macros
132 * Tracepoints:: Debugging remote targets non-intrusively
133 * Overlays:: Debugging programs that use overlays
135 * Languages:: Using @value{GDBN} with different languages
137 * Symbols:: Examining the symbol table
138 * Altering:: Altering execution
139 * GDB Files:: @value{GDBN} files
140 * Targets:: Specifying a debugging target
141 * Remote Debugging:: Debugging remote programs
142 * Configurations:: Configuration-specific information
143 * Controlling GDB:: Controlling @value{GDBN}
144 * Sequences:: Canned sequences of commands
145 * TUI:: @value{GDBN} Text User Interface
146 * Interpreters:: Command Interpreters
147 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
148 * Annotations:: @value{GDBN}'s annotation interface.
149 * GDB/MI:: @value{GDBN}'s Machine Interface.
151 * GDB Bugs:: Reporting bugs in @value{GDBN}
152 * Formatting Documentation:: How to format and print @value{GDBN} documentation
154 * Command Line Editing:: Command Line Editing
155 * Using History Interactively:: Using History Interactively
156 * Installing GDB:: Installing GDB
157 * Maintenance Commands:: Maintenance Commands
158 * Remote Protocol:: GDB Remote Serial Protocol
159 * Agent Expressions:: The GDB Agent Expression Mechanism
160 * Copying:: GNU General Public License says
161 how you can copy and share GDB
162 * GNU Free Documentation License:: The license for this documentation
171 @unnumbered Summary of @value{GDBN}
173 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
174 going on ``inside'' another program while it executes---or what another
175 program was doing at the moment it crashed.
177 @value{GDBN} can do four main kinds of things (plus other things in support of
178 these) to help you catch bugs in the act:
182 Start your program, specifying anything that might affect its behavior.
185 Make your program stop on specified conditions.
188 Examine what has happened, when your program has stopped.
191 Change things in your program, so you can experiment with correcting the
192 effects of one bug and go on to learn about another.
195 You can use @value{GDBN} to debug programs written in C and C@t{++}.
196 For more information, see @ref{Support,,Supported languages}.
197 For more information, see @ref{C,,C and C++}.
200 Support for Modula-2 is partial. For information on Modula-2, see
201 @ref{Modula-2,,Modula-2}.
204 Debugging Pascal programs which use sets, subranges, file variables, or
205 nested functions does not currently work. @value{GDBN} does not support
206 entering expressions, printing values, or similar features using Pascal
210 @value{GDBN} can be used to debug programs written in Fortran, although
211 it may be necessary to refer to some variables with a trailing
214 @value{GDBN} can be used to debug programs written in Objective-C,
215 using either the Apple/NeXT or the GNU Objective-C runtime.
218 * Free Software:: Freely redistributable software
219 * Contributors:: Contributors to GDB
223 @unnumberedsec Free software
225 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
226 General Public License
227 (GPL). The GPL gives you the freedom to copy or adapt a licensed
228 program---but every person getting a copy also gets with it the
229 freedom to modify that copy (which means that they must get access to
230 the source code), and the freedom to distribute further copies.
231 Typical software companies use copyrights to limit your freedoms; the
232 Free Software Foundation uses the GPL to preserve these freedoms.
234 Fundamentally, the General Public License is a license which says that
235 you have these freedoms and that you cannot take these freedoms away
238 @unnumberedsec Free Software Needs Free Documentation
240 The biggest deficiency in the free software community today is not in
241 the software---it is the lack of good free documentation that we can
242 include with the free software. Many of our most important
243 programs do not come with free reference manuals and free introductory
244 texts. Documentation is an essential part of any software package;
245 when an important free software package does not come with a free
246 manual and a free tutorial, that is a major gap. We have many such
249 Consider Perl, for instance. The tutorial manuals that people
250 normally use are non-free. How did this come about? Because the
251 authors of those manuals published them with restrictive terms---no
252 copying, no modification, source files not available---which exclude
253 them from the free software world.
255 That wasn't the first time this sort of thing happened, and it was far
256 from the last. Many times we have heard a GNU user eagerly describe a
257 manual that he is writing, his intended contribution to the community,
258 only to learn that he had ruined everything by signing a publication
259 contract to make it non-free.
261 Free documentation, like free software, is a matter of freedom, not
262 price. The problem with the non-free manual is not that publishers
263 charge a price for printed copies---that in itself is fine. (The Free
264 Software Foundation sells printed copies of manuals, too.) The
265 problem is the restrictions on the use of the manual. Free manuals
266 are available in source code form, and give you permission to copy and
267 modify. Non-free manuals do not allow this.
269 The criteria of freedom for a free manual are roughly the same as for
270 free software. Redistribution (including the normal kinds of
271 commercial redistribution) must be permitted, so that the manual can
272 accompany every copy of the program, both on-line and on paper.
274 Permission for modification of the technical content is crucial too.
275 When people modify the software, adding or changing features, if they
276 are conscientious they will change the manual too---so they can
277 provide accurate and clear documentation for the modified program. A
278 manual that leaves you no choice but to write a new manual to document
279 a changed version of the program is not really available to our
282 Some kinds of limits on the way modification is handled are
283 acceptable. For example, requirements to preserve the original
284 author's copyright notice, the distribution terms, or the list of
285 authors, are ok. It is also no problem to require modified versions
286 to include notice that they were modified. Even entire sections that
287 may not be deleted or changed are acceptable, as long as they deal
288 with nontechnical topics (like this one). These kinds of restrictions
289 are acceptable because they don't obstruct the community's normal use
292 However, it must be possible to modify all the @emph{technical}
293 content of the manual, and then distribute the result in all the usual
294 media, through all the usual channels. Otherwise, the restrictions
295 obstruct the use of the manual, it is not free, and we need another
296 manual to replace it.
298 Please spread the word about this issue. Our community continues to
299 lose manuals to proprietary publishing. If we spread the word that
300 free software needs free reference manuals and free tutorials, perhaps
301 the next person who wants to contribute by writing documentation will
302 realize, before it is too late, that only free manuals contribute to
303 the free software community.
305 If you are writing documentation, please insist on publishing it under
306 the GNU Free Documentation License or another free documentation
307 license. Remember that this decision requires your approval---you
308 don't have to let the publisher decide. Some commercial publishers
309 will use a free license if you insist, but they will not propose the
310 option; it is up to you to raise the issue and say firmly that this is
311 what you want. If the publisher you are dealing with refuses, please
312 try other publishers. If you're not sure whether a proposed license
313 is free, write to @email{licensing@@gnu.org}.
315 You can encourage commercial publishers to sell more free, copylefted
316 manuals and tutorials by buying them, and particularly by buying
317 copies from the publishers that paid for their writing or for major
318 improvements. Meanwhile, try to avoid buying non-free documentation
319 at all. Check the distribution terms of a manual before you buy it,
320 and insist that whoever seeks your business must respect your freedom.
321 Check the history of the book, and try to reward the publishers that
322 have paid or pay the authors to work on it.
324 The Free Software Foundation maintains a list of free documentation
325 published by other publishers, at
326 @url{http://www.fsf.org/doc/other-free-books.html}.
329 @unnumberedsec Contributors to @value{GDBN}
331 Richard Stallman was the original author of @value{GDBN}, and of many
332 other @sc{gnu} programs. Many others have contributed to its
333 development. This section attempts to credit major contributors. One
334 of the virtues of free software is that everyone is free to contribute
335 to it; with regret, we cannot actually acknowledge everyone here. The
336 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
337 blow-by-blow account.
339 Changes much prior to version 2.0 are lost in the mists of time.
342 @emph{Plea:} Additions to this section are particularly welcome. If you
343 or your friends (or enemies, to be evenhanded) have been unfairly
344 omitted from this list, we would like to add your names!
347 So that they may not regard their many labors as thankless, we
348 particularly thank those who shepherded @value{GDBN} through major
350 Andrew Cagney (releases 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
351 Jim Blandy (release 4.18);
352 Jason Molenda (release 4.17);
353 Stan Shebs (release 4.14);
354 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
355 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
356 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
357 Jim Kingdon (releases 3.5, 3.4, and 3.3);
358 and Randy Smith (releases 3.2, 3.1, and 3.0).
360 Richard Stallman, assisted at various times by Peter TerMaat, Chris
361 Hanson, and Richard Mlynarik, handled releases through 2.8.
363 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
364 in @value{GDBN}, with significant additional contributions from Per
365 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
366 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
367 much general update work leading to release 3.0).
369 @value{GDBN} uses the BFD subroutine library to examine multiple
370 object-file formats; BFD was a joint project of David V.
371 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
373 David Johnson wrote the original COFF support; Pace Willison did
374 the original support for encapsulated COFF.
376 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
378 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
379 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
381 Jean-Daniel Fekete contributed Sun 386i support.
382 Chris Hanson improved the HP9000 support.
383 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
384 David Johnson contributed Encore Umax support.
385 Jyrki Kuoppala contributed Altos 3068 support.
386 Jeff Law contributed HP PA and SOM support.
387 Keith Packard contributed NS32K support.
388 Doug Rabson contributed Acorn Risc Machine support.
389 Bob Rusk contributed Harris Nighthawk CX-UX support.
390 Chris Smith contributed Convex support (and Fortran debugging).
391 Jonathan Stone contributed Pyramid support.
392 Michael Tiemann contributed SPARC support.
393 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
394 Pace Willison contributed Intel 386 support.
395 Jay Vosburgh contributed Symmetry support.
396 Marko Mlinar contributed OpenRISC 1000 support.
398 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
400 Rich Schaefer and Peter Schauer helped with support of SunOS shared
403 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
404 about several machine instruction sets.
406 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
407 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
408 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
409 and RDI targets, respectively.
411 Brian Fox is the author of the readline libraries providing
412 command-line editing and command history.
414 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
415 Modula-2 support, and contributed the Languages chapter of this manual.
417 Fred Fish wrote most of the support for Unix System Vr4.
418 He also enhanced the command-completion support to cover C@t{++} overloaded
421 Hitachi America (now Renesas America), Ltd. sponsored the support for
422 H8/300, H8/500, and Super-H processors.
424 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
426 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
429 Toshiba sponsored the support for the TX39 Mips processor.
431 Matsushita sponsored the support for the MN10200 and MN10300 processors.
433 Fujitsu sponsored the support for SPARClite and FR30 processors.
435 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
438 Michael Snyder added support for tracepoints.
440 Stu Grossman wrote gdbserver.
442 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
443 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
445 The following people at the Hewlett-Packard Company contributed
446 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
447 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
448 compiler, and the Text User Interface (nee Terminal User Interface):
449 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
450 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
451 provided HP-specific information in this manual.
453 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
454 Robert Hoehne made significant contributions to the DJGPP port.
456 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
457 development since 1991. Cygnus engineers who have worked on @value{GDBN}
458 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
459 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
460 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
461 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
462 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
463 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
464 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
465 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
466 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
467 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
468 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
469 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
470 Zuhn have made contributions both large and small.
472 Jim Blandy added support for preprocessor macros, while working for Red
476 @chapter A Sample @value{GDBN} Session
478 You can use this manual at your leisure to read all about @value{GDBN}.
479 However, a handful of commands are enough to get started using the
480 debugger. This chapter illustrates those commands.
483 In this sample session, we emphasize user input like this: @b{input},
484 to make it easier to pick out from the surrounding output.
487 @c FIXME: this example may not be appropriate for some configs, where
488 @c FIXME...primary interest is in remote use.
490 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
491 processor) exhibits the following bug: sometimes, when we change its
492 quote strings from the default, the commands used to capture one macro
493 definition within another stop working. In the following short @code{m4}
494 session, we define a macro @code{foo} which expands to @code{0000}; we
495 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
496 same thing. However, when we change the open quote string to
497 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
498 procedure fails to define a new synonym @code{baz}:
507 @b{define(bar,defn(`foo'))}
511 @b{changequote(<QUOTE>,<UNQUOTE>)}
513 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
516 m4: End of input: 0: fatal error: EOF in string
520 Let us use @value{GDBN} to try to see what is going on.
523 $ @b{@value{GDBP} m4}
524 @c FIXME: this falsifies the exact text played out, to permit smallbook
525 @c FIXME... format to come out better.
526 @value{GDBN} is free software and you are welcome to distribute copies
527 of it under certain conditions; type "show copying" to see
529 There is absolutely no warranty for @value{GDBN}; type "show warranty"
532 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
537 @value{GDBN} reads only enough symbol data to know where to find the
538 rest when needed; as a result, the first prompt comes up very quickly.
539 We now tell @value{GDBN} to use a narrower display width than usual, so
540 that examples fit in this manual.
543 (@value{GDBP}) @b{set width 70}
547 We need to see how the @code{m4} built-in @code{changequote} works.
548 Having looked at the source, we know the relevant subroutine is
549 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
550 @code{break} command.
553 (@value{GDBP}) @b{break m4_changequote}
554 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
558 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
559 control; as long as control does not reach the @code{m4_changequote}
560 subroutine, the program runs as usual:
563 (@value{GDBP}) @b{run}
564 Starting program: /work/Editorial/gdb/gnu/m4/m4
572 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
573 suspends execution of @code{m4}, displaying information about the
574 context where it stops.
577 @b{changequote(<QUOTE>,<UNQUOTE>)}
579 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
581 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
585 Now we use the command @code{n} (@code{next}) to advance execution to
586 the next line of the current function.
590 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
595 @code{set_quotes} looks like a promising subroutine. We can go into it
596 by using the command @code{s} (@code{step}) instead of @code{next}.
597 @code{step} goes to the next line to be executed in @emph{any}
598 subroutine, so it steps into @code{set_quotes}.
602 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
604 530 if (lquote != def_lquote)
608 The display that shows the subroutine where @code{m4} is now
609 suspended (and its arguments) is called a stack frame display. It
610 shows a summary of the stack. We can use the @code{backtrace}
611 command (which can also be spelled @code{bt}), to see where we are
612 in the stack as a whole: the @code{backtrace} command displays a
613 stack frame for each active subroutine.
616 (@value{GDBP}) @b{bt}
617 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
619 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
621 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
622 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
624 #4 0x79dc in expand_input () at macro.c:40
625 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
629 We step through a few more lines to see what happens. The first two
630 times, we can use @samp{s}; the next two times we use @code{n} to avoid
631 falling into the @code{xstrdup} subroutine.
635 0x3b5c 532 if (rquote != def_rquote)
637 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
638 def_lquote : xstrdup(lq);
640 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
643 538 len_lquote = strlen(rquote);
647 The last line displayed looks a little odd; we can examine the variables
648 @code{lquote} and @code{rquote} to see if they are in fact the new left
649 and right quotes we specified. We use the command @code{p}
650 (@code{print}) to see their values.
653 (@value{GDBP}) @b{p lquote}
654 $1 = 0x35d40 "<QUOTE>"
655 (@value{GDBP}) @b{p rquote}
656 $2 = 0x35d50 "<UNQUOTE>"
660 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
661 To look at some context, we can display ten lines of source
662 surrounding the current line with the @code{l} (@code{list}) command.
668 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
670 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
673 538 len_lquote = strlen(rquote);
674 539 len_rquote = strlen(lquote);
681 Let us step past the two lines that set @code{len_lquote} and
682 @code{len_rquote}, and then examine the values of those variables.
686 539 len_rquote = strlen(lquote);
689 (@value{GDBP}) @b{p len_lquote}
691 (@value{GDBP}) @b{p len_rquote}
696 That certainly looks wrong, assuming @code{len_lquote} and
697 @code{len_rquote} are meant to be the lengths of @code{lquote} and
698 @code{rquote} respectively. We can set them to better values using
699 the @code{p} command, since it can print the value of
700 any expression---and that expression can include subroutine calls and
704 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
706 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
711 Is that enough to fix the problem of using the new quotes with the
712 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
713 executing with the @code{c} (@code{continue}) command, and then try the
714 example that caused trouble initially:
720 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
727 Success! The new quotes now work just as well as the default ones. The
728 problem seems to have been just the two typos defining the wrong
729 lengths. We allow @code{m4} exit by giving it an EOF as input:
733 Program exited normally.
737 The message @samp{Program exited normally.} is from @value{GDBN}; it
738 indicates @code{m4} has finished executing. We can end our @value{GDBN}
739 session with the @value{GDBN} @code{quit} command.
742 (@value{GDBP}) @b{quit}
746 @chapter Getting In and Out of @value{GDBN}
748 This chapter discusses how to start @value{GDBN}, and how to get out of it.
752 type @samp{@value{GDBP}} to start @value{GDBN}.
754 type @kbd{quit} or @kbd{C-d} to exit.
758 * Invoking GDB:: How to start @value{GDBN}
759 * Quitting GDB:: How to quit @value{GDBN}
760 * Shell Commands:: How to use shell commands inside @value{GDBN}
761 * Logging output:: How to log @value{GDBN}'s output to a file
765 @section Invoking @value{GDBN}
767 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
768 @value{GDBN} reads commands from the terminal until you tell it to exit.
770 You can also run @code{@value{GDBP}} with a variety of arguments and options,
771 to specify more of your debugging environment at the outset.
773 The command-line options described here are designed
774 to cover a variety of situations; in some environments, some of these
775 options may effectively be unavailable.
777 The most usual way to start @value{GDBN} is with one argument,
778 specifying an executable program:
781 @value{GDBP} @var{program}
785 You can also start with both an executable program and a core file
789 @value{GDBP} @var{program} @var{core}
792 You can, instead, specify a process ID as a second argument, if you want
793 to debug a running process:
796 @value{GDBP} @var{program} 1234
800 would attach @value{GDBN} to process @code{1234} (unless you also have a file
801 named @file{1234}; @value{GDBN} does check for a core file first).
803 Taking advantage of the second command-line argument requires a fairly
804 complete operating system; when you use @value{GDBN} as a remote
805 debugger attached to a bare board, there may not be any notion of
806 ``process'', and there is often no way to get a core dump. @value{GDBN}
807 will warn you if it is unable to attach or to read core dumps.
809 You can optionally have @code{@value{GDBP}} pass any arguments after the
810 executable file to the inferior using @code{--args}. This option stops
813 gdb --args gcc -O2 -c foo.c
815 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
816 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
818 You can run @code{@value{GDBP}} without printing the front material, which describes
819 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
826 You can further control how @value{GDBN} starts up by using command-line
827 options. @value{GDBN} itself can remind you of the options available.
837 to display all available options and briefly describe their use
838 (@samp{@value{GDBP} -h} is a shorter equivalent).
840 All options and command line arguments you give are processed
841 in sequential order. The order makes a difference when the
842 @samp{-x} option is used.
846 * File Options:: Choosing files
847 * Mode Options:: Choosing modes
851 @subsection Choosing files
853 When @value{GDBN} starts, it reads any arguments other than options as
854 specifying an executable file and core file (or process ID). This is
855 the same as if the arguments were specified by the @samp{-se} and
856 @samp{-c} (or @samp{-p} options respectively. (@value{GDBN} reads the
857 first argument that does not have an associated option flag as
858 equivalent to the @samp{-se} option followed by that argument; and the
859 second argument that does not have an associated option flag, if any, as
860 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
861 If the second argument begins with a decimal digit, @value{GDBN} will
862 first attempt to attach to it as a process, and if that fails, attempt
863 to open it as a corefile. If you have a corefile whose name begins with
864 a digit, you can prevent @value{GDBN} from treating it as a pid by
865 prefixing it with @file{./}, eg. @file{./12345}.
867 If @value{GDBN} has not been configured to included core file support,
868 such as for most embedded targets, then it will complain about a second
869 argument and ignore it.
871 Many options have both long and short forms; both are shown in the
872 following list. @value{GDBN} also recognizes the long forms if you truncate
873 them, so long as enough of the option is present to be unambiguous.
874 (If you prefer, you can flag option arguments with @samp{--} rather
875 than @samp{-}, though we illustrate the more usual convention.)
877 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
878 @c way, both those who look for -foo and --foo in the index, will find
882 @item -symbols @var{file}
884 @cindex @code{--symbols}
886 Read symbol table from file @var{file}.
888 @item -exec @var{file}
890 @cindex @code{--exec}
892 Use file @var{file} as the executable file to execute when appropriate,
893 and for examining pure data in conjunction with a core dump.
897 Read symbol table from file @var{file} and use it as the executable
900 @item -core @var{file}
902 @cindex @code{--core}
904 Use file @var{file} as a core dump to examine.
906 @item -c @var{number}
907 @item -pid @var{number}
908 @itemx -p @var{number}
911 Connect to process ID @var{number}, as with the @code{attach} command.
912 If there is no such process, @value{GDBN} will attempt to open a core
913 file named @var{number}.
915 @item -command @var{file}
917 @cindex @code{--command}
919 Execute @value{GDBN} commands from file @var{file}. @xref{Command
920 Files,, Command files}.
922 @item -directory @var{directory}
923 @itemx -d @var{directory}
924 @cindex @code{--directory}
926 Add @var{directory} to the path to search for source files.
930 @cindex @code{--mapped}
932 @emph{Warning: this option depends on operating system facilities that are not
933 supported on all systems.}@*
934 If memory-mapped files are available on your system through the @code{mmap}
935 system call, you can use this option
936 to have @value{GDBN} write the symbols from your
937 program into a reusable file in the current directory. If the program you are debugging is
938 called @file{/tmp/fred}, the mapped symbol file is @file{/tmp/fred.syms}.
939 Future @value{GDBN} debugging sessions notice the presence of this file,
940 and can quickly map in symbol information from it, rather than reading
941 the symbol table from the executable program.
943 The @file{.syms} file is specific to the host machine where @value{GDBN}
944 is run. It holds an exact image of the internal @value{GDBN} symbol
945 table. It cannot be shared across multiple host platforms.
949 @cindex @code{--readnow}
951 Read each symbol file's entire symbol table immediately, rather than
952 the default, which is to read it incrementally as it is needed.
953 This makes startup slower, but makes future operations faster.
957 You typically combine the @code{-mapped} and @code{-readnow} options in
958 order to build a @file{.syms} file that contains complete symbol
959 information. (@xref{Files,,Commands to specify files}, for information
960 on @file{.syms} files.) A simple @value{GDBN} invocation to do nothing
961 but build a @file{.syms} file for future use is:
964 gdb -batch -nx -mapped -readnow programname
968 @subsection Choosing modes
970 You can run @value{GDBN} in various alternative modes---for example, in
971 batch mode or quiet mode.
978 Do not execute commands found in any initialization files. Normally,
979 @value{GDBN} executes the commands in these files after all the command
980 options and arguments have been processed. @xref{Command Files,,Command
986 @cindex @code{--quiet}
987 @cindex @code{--silent}
989 ``Quiet''. Do not print the introductory and copyright messages. These
990 messages are also suppressed in batch mode.
993 @cindex @code{--batch}
994 Run in batch mode. Exit with status @code{0} after processing all the
995 command files specified with @samp{-x} (and all commands from
996 initialization files, if not inhibited with @samp{-n}). Exit with
997 nonzero status if an error occurs in executing the @value{GDBN} commands
998 in the command files.
1000 Batch mode may be useful for running @value{GDBN} as a filter, for
1001 example to download and run a program on another computer; in order to
1002 make this more useful, the message
1005 Program exited normally.
1009 (which is ordinarily issued whenever a program running under
1010 @value{GDBN} control terminates) is not issued when running in batch
1015 @cindex @code{--nowindows}
1017 ``No windows''. If @value{GDBN} comes with a graphical user interface
1018 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1019 interface. If no GUI is available, this option has no effect.
1023 @cindex @code{--windows}
1025 If @value{GDBN} includes a GUI, then this option requires it to be
1028 @item -cd @var{directory}
1030 Run @value{GDBN} using @var{directory} as its working directory,
1031 instead of the current directory.
1035 @cindex @code{--fullname}
1037 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1038 subprocess. It tells @value{GDBN} to output the full file name and line
1039 number in a standard, recognizable fashion each time a stack frame is
1040 displayed (which includes each time your program stops). This
1041 recognizable format looks like two @samp{\032} characters, followed by
1042 the file name, line number and character position separated by colons,
1043 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1044 @samp{\032} characters as a signal to display the source code for the
1048 @cindex @code{--epoch}
1049 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1050 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1051 routines so as to allow Epoch to display values of expressions in a
1054 @item -annotate @var{level}
1055 @cindex @code{--annotate}
1056 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1057 effect is identical to using @samp{set annotate @var{level}}
1058 (@pxref{Annotations}). The annotation @var{level} controls how much
1059 information @value{GDBN} prints together with its prompt, values of
1060 expressions, source lines, and other types of output. Level 0 is the
1061 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1062 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1063 that control @value{GDBN}, and level 2 has been deprecated.
1065 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
1069 @cindex @code{--args}
1070 Change interpretation of command line so that arguments following the
1071 executable file are passed as command line arguments to the inferior.
1072 This option stops option processing.
1074 @item -baud @var{bps}
1076 @cindex @code{--baud}
1078 Set the line speed (baud rate or bits per second) of any serial
1079 interface used by @value{GDBN} for remote debugging.
1081 @item -tty @var{device}
1082 @itemx -t @var{device}
1083 @cindex @code{--tty}
1085 Run using @var{device} for your program's standard input and output.
1086 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1088 @c resolve the situation of these eventually
1090 @cindex @code{--tui}
1091 Activate the @dfn{Text User Interface} when starting. The Text User
1092 Interface manages several text windows on the terminal, showing
1093 source, assembly, registers and @value{GDBN} command outputs
1094 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1095 Text User Interface can be enabled by invoking the program
1096 @samp{gdbtui}. Do not use this option if you run @value{GDBN} from
1097 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1100 @c @cindex @code{--xdb}
1101 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1102 @c For information, see the file @file{xdb_trans.html}, which is usually
1103 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1106 @item -interpreter @var{interp}
1107 @cindex @code{--interpreter}
1108 Use the interpreter @var{interp} for interface with the controlling
1109 program or device. This option is meant to be set by programs which
1110 communicate with @value{GDBN} using it as a back end.
1111 @xref{Interpreters, , Command Interpreters}.
1113 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1114 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1115 The @sc{gdb/mi} Interface}) included since @var{GDBN} version 6.0. The
1116 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1117 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1118 @sc{gdb/mi} interfaces are no longer supported.
1121 @cindex @code{--write}
1122 Open the executable and core files for both reading and writing. This
1123 is equivalent to the @samp{set write on} command inside @value{GDBN}
1127 @cindex @code{--statistics}
1128 This option causes @value{GDBN} to print statistics about time and
1129 memory usage after it completes each command and returns to the prompt.
1132 @cindex @code{--version}
1133 This option causes @value{GDBN} to print its version number and
1134 no-warranty blurb, and exit.
1139 @section Quitting @value{GDBN}
1140 @cindex exiting @value{GDBN}
1141 @cindex leaving @value{GDBN}
1144 @kindex quit @r{[}@var{expression}@r{]}
1145 @kindex q @r{(@code{quit})}
1146 @item quit @r{[}@var{expression}@r{]}
1148 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1149 @code{q}), or type an end-of-file character (usually @kbd{C-d}). If you
1150 do not supply @var{expression}, @value{GDBN} will terminate normally;
1151 otherwise it will terminate using the result of @var{expression} as the
1156 An interrupt (often @kbd{C-c}) does not exit from @value{GDBN}, but rather
1157 terminates the action of any @value{GDBN} command that is in progress and
1158 returns to @value{GDBN} command level. It is safe to type the interrupt
1159 character at any time because @value{GDBN} does not allow it to take effect
1160 until a time when it is safe.
1162 If you have been using @value{GDBN} to control an attached process or
1163 device, you can release it with the @code{detach} command
1164 (@pxref{Attach, ,Debugging an already-running process}).
1166 @node Shell Commands
1167 @section Shell commands
1169 If you need to execute occasional shell commands during your
1170 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1171 just use the @code{shell} command.
1175 @cindex shell escape
1176 @item shell @var{command string}
1177 Invoke a standard shell to execute @var{command string}.
1178 If it exists, the environment variable @code{SHELL} determines which
1179 shell to run. Otherwise @value{GDBN} uses the default shell
1180 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1183 The utility @code{make} is often needed in development environments.
1184 You do not have to use the @code{shell} command for this purpose in
1189 @cindex calling make
1190 @item make @var{make-args}
1191 Execute the @code{make} program with the specified
1192 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1195 @node Logging output
1196 @section Logging output
1197 @cindex logging @value{GDBN} output
1199 You may want to save the output of @value{GDBN} commands to a file.
1200 There are several commands to control @value{GDBN}'s logging.
1204 @item set logging on
1206 @item set logging off
1208 @item set logging file @var{file}
1209 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1210 @item set logging overwrite [on|off]
1211 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1212 you want @code{set logging on} to overwrite the logfile instead.
1213 @item set logging redirect [on|off]
1214 By default, @value{GDBN} output will go to both the terminal and the logfile.
1215 Set @code{redirect} if you want output to go only to the log file.
1216 @kindex show logging
1218 Show the current values of the logging settings.
1222 @chapter @value{GDBN} Commands
1224 You can abbreviate a @value{GDBN} command to the first few letters of the command
1225 name, if that abbreviation is unambiguous; and you can repeat certain
1226 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1227 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1228 show you the alternatives available, if there is more than one possibility).
1231 * Command Syntax:: How to give commands to @value{GDBN}
1232 * Completion:: Command completion
1233 * Help:: How to ask @value{GDBN} for help
1236 @node Command Syntax
1237 @section Command syntax
1239 A @value{GDBN} command is a single line of input. There is no limit on
1240 how long it can be. It starts with a command name, which is followed by
1241 arguments whose meaning depends on the command name. For example, the
1242 command @code{step} accepts an argument which is the number of times to
1243 step, as in @samp{step 5}. You can also use the @code{step} command
1244 with no arguments. Some commands do not allow any arguments.
1246 @cindex abbreviation
1247 @value{GDBN} command names may always be truncated if that abbreviation is
1248 unambiguous. Other possible command abbreviations are listed in the
1249 documentation for individual commands. In some cases, even ambiguous
1250 abbreviations are allowed; for example, @code{s} is specially defined as
1251 equivalent to @code{step} even though there are other commands whose
1252 names start with @code{s}. You can test abbreviations by using them as
1253 arguments to the @code{help} command.
1255 @cindex repeating commands
1256 @kindex RET @r{(repeat last command)}
1257 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1258 repeat the previous command. Certain commands (for example, @code{run})
1259 will not repeat this way; these are commands whose unintentional
1260 repetition might cause trouble and which you are unlikely to want to
1263 The @code{list} and @code{x} commands, when you repeat them with
1264 @key{RET}, construct new arguments rather than repeating
1265 exactly as typed. This permits easy scanning of source or memory.
1267 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1268 output, in a way similar to the common utility @code{more}
1269 (@pxref{Screen Size,,Screen size}). Since it is easy to press one
1270 @key{RET} too many in this situation, @value{GDBN} disables command
1271 repetition after any command that generates this sort of display.
1273 @kindex # @r{(a comment)}
1275 Any text from a @kbd{#} to the end of the line is a comment; it does
1276 nothing. This is useful mainly in command files (@pxref{Command
1277 Files,,Command files}).
1279 @cindex repeating command sequences
1280 @kindex C-o @r{(operate-and-get-next)}
1281 The @kbd{C-o} binding is useful for repeating a complex sequence of
1282 commands. This command accepts the current line, like @kbd{RET}, and
1283 then fetches the next line relative to the current line from the history
1287 @section Command completion
1290 @cindex word completion
1291 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1292 only one possibility; it can also show you what the valid possibilities
1293 are for the next word in a command, at any time. This works for @value{GDBN}
1294 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1296 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1297 of a word. If there is only one possibility, @value{GDBN} fills in the
1298 word, and waits for you to finish the command (or press @key{RET} to
1299 enter it). For example, if you type
1301 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1302 @c complete accuracy in these examples; space introduced for clarity.
1303 @c If texinfo enhancements make it unnecessary, it would be nice to
1304 @c replace " @key" by "@key" in the following...
1306 (@value{GDBP}) info bre @key{TAB}
1310 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1311 the only @code{info} subcommand beginning with @samp{bre}:
1314 (@value{GDBP}) info breakpoints
1318 You can either press @key{RET} at this point, to run the @code{info
1319 breakpoints} command, or backspace and enter something else, if
1320 @samp{breakpoints} does not look like the command you expected. (If you
1321 were sure you wanted @code{info breakpoints} in the first place, you
1322 might as well just type @key{RET} immediately after @samp{info bre},
1323 to exploit command abbreviations rather than command completion).
1325 If there is more than one possibility for the next word when you press
1326 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1327 characters and try again, or just press @key{TAB} a second time;
1328 @value{GDBN} displays all the possible completions for that word. For
1329 example, you might want to set a breakpoint on a subroutine whose name
1330 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1331 just sounds the bell. Typing @key{TAB} again displays all the
1332 function names in your program that begin with those characters, for
1336 (@value{GDBP}) b make_ @key{TAB}
1337 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1338 make_a_section_from_file make_environ
1339 make_abs_section make_function_type
1340 make_blockvector make_pointer_type
1341 make_cleanup make_reference_type
1342 make_command make_symbol_completion_list
1343 (@value{GDBP}) b make_
1347 After displaying the available possibilities, @value{GDBN} copies your
1348 partial input (@samp{b make_} in the example) so you can finish the
1351 If you just want to see the list of alternatives in the first place, you
1352 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1353 means @kbd{@key{META} ?}. You can type this either by holding down a
1354 key designated as the @key{META} shift on your keyboard (if there is
1355 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1357 @cindex quotes in commands
1358 @cindex completion of quoted strings
1359 Sometimes the string you need, while logically a ``word'', may contain
1360 parentheses or other characters that @value{GDBN} normally excludes from
1361 its notion of a word. To permit word completion to work in this
1362 situation, you may enclose words in @code{'} (single quote marks) in
1363 @value{GDBN} commands.
1365 The most likely situation where you might need this is in typing the
1366 name of a C@t{++} function. This is because C@t{++} allows function
1367 overloading (multiple definitions of the same function, distinguished
1368 by argument type). For example, when you want to set a breakpoint you
1369 may need to distinguish whether you mean the version of @code{name}
1370 that takes an @code{int} parameter, @code{name(int)}, or the version
1371 that takes a @code{float} parameter, @code{name(float)}. To use the
1372 word-completion facilities in this situation, type a single quote
1373 @code{'} at the beginning of the function name. This alerts
1374 @value{GDBN} that it may need to consider more information than usual
1375 when you press @key{TAB} or @kbd{M-?} to request word completion:
1378 (@value{GDBP}) b 'bubble( @kbd{M-?}
1379 bubble(double,double) bubble(int,int)
1380 (@value{GDBP}) b 'bubble(
1383 In some cases, @value{GDBN} can tell that completing a name requires using
1384 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1385 completing as much as it can) if you do not type the quote in the first
1389 (@value{GDBP}) b bub @key{TAB}
1390 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1391 (@value{GDBP}) b 'bubble(
1395 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1396 you have not yet started typing the argument list when you ask for
1397 completion on an overloaded symbol.
1399 For more information about overloaded functions, see @ref{C plus plus
1400 expressions, ,C@t{++} expressions}. You can use the command @code{set
1401 overload-resolution off} to disable overload resolution;
1402 see @ref{Debugging C plus plus, ,@value{GDBN} features for C@t{++}}.
1406 @section Getting help
1407 @cindex online documentation
1410 You can always ask @value{GDBN} itself for information on its commands,
1411 using the command @code{help}.
1414 @kindex h @r{(@code{help})}
1417 You can use @code{help} (abbreviated @code{h}) with no arguments to
1418 display a short list of named classes of commands:
1422 List of classes of commands:
1424 aliases -- Aliases of other commands
1425 breakpoints -- Making program stop at certain points
1426 data -- Examining data
1427 files -- Specifying and examining files
1428 internals -- Maintenance commands
1429 obscure -- Obscure features
1430 running -- Running the program
1431 stack -- Examining the stack
1432 status -- Status inquiries
1433 support -- Support facilities
1434 tracepoints -- Tracing of program execution without@*
1435 stopping the program
1436 user-defined -- User-defined commands
1438 Type "help" followed by a class name for a list of
1439 commands in that class.
1440 Type "help" followed by command name for full
1442 Command name abbreviations are allowed if unambiguous.
1445 @c the above line break eliminates huge line overfull...
1447 @item help @var{class}
1448 Using one of the general help classes as an argument, you can get a
1449 list of the individual commands in that class. For example, here is the
1450 help display for the class @code{status}:
1453 (@value{GDBP}) help status
1458 @c Line break in "show" line falsifies real output, but needed
1459 @c to fit in smallbook page size.
1460 info -- Generic command for showing things
1461 about the program being debugged
1462 show -- Generic command for showing things
1465 Type "help" followed by command name for full
1467 Command name abbreviations are allowed if unambiguous.
1471 @item help @var{command}
1472 With a command name as @code{help} argument, @value{GDBN} displays a
1473 short paragraph on how to use that command.
1476 @item apropos @var{args}
1477 The @code{apropos @var{args}} command searches through all of the @value{GDBN}
1478 commands, and their documentation, for the regular expression specified in
1479 @var{args}. It prints out all matches found. For example:
1490 set symbol-reloading -- Set dynamic symbol table reloading
1491 multiple times in one run
1492 show symbol-reloading -- Show dynamic symbol table reloading
1493 multiple times in one run
1498 @item complete @var{args}
1499 The @code{complete @var{args}} command lists all the possible completions
1500 for the beginning of a command. Use @var{args} to specify the beginning of the
1501 command you want completed. For example:
1507 @noindent results in:
1518 @noindent This is intended for use by @sc{gnu} Emacs.
1521 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1522 and @code{show} to inquire about the state of your program, or the state
1523 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1524 manual introduces each of them in the appropriate context. The listings
1525 under @code{info} and under @code{show} in the Index point to
1526 all the sub-commands. @xref{Index}.
1531 @kindex i @r{(@code{info})}
1533 This command (abbreviated @code{i}) is for describing the state of your
1534 program. For example, you can list the arguments given to your program
1535 with @code{info args}, list the registers currently in use with @code{info
1536 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1537 You can get a complete list of the @code{info} sub-commands with
1538 @w{@code{help info}}.
1542 You can assign the result of an expression to an environment variable with
1543 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1544 @code{set prompt $}.
1548 In contrast to @code{info}, @code{show} is for describing the state of
1549 @value{GDBN} itself.
1550 You can change most of the things you can @code{show}, by using the
1551 related command @code{set}; for example, you can control what number
1552 system is used for displays with @code{set radix}, or simply inquire
1553 which is currently in use with @code{show radix}.
1556 To display all the settable parameters and their current
1557 values, you can use @code{show} with no arguments; you may also use
1558 @code{info set}. Both commands produce the same display.
1559 @c FIXME: "info set" violates the rule that "info" is for state of
1560 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1561 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1565 Here are three miscellaneous @code{show} subcommands, all of which are
1566 exceptional in lacking corresponding @code{set} commands:
1569 @kindex show version
1570 @cindex version number
1572 Show what version of @value{GDBN} is running. You should include this
1573 information in @value{GDBN} bug-reports. If multiple versions of
1574 @value{GDBN} are in use at your site, you may need to determine which
1575 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1576 commands are introduced, and old ones may wither away. Also, many
1577 system vendors ship variant versions of @value{GDBN}, and there are
1578 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1579 The version number is the same as the one announced when you start
1582 @kindex show copying
1584 Display information about permission for copying @value{GDBN}.
1586 @kindex show warranty
1588 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1589 if your version of @value{GDBN} comes with one.
1594 @chapter Running Programs Under @value{GDBN}
1596 When you run a program under @value{GDBN}, you must first generate
1597 debugging information when you compile it.
1599 You may start @value{GDBN} with its arguments, if any, in an environment
1600 of your choice. If you are doing native debugging, you may redirect
1601 your program's input and output, debug an already running process, or
1602 kill a child process.
1605 * Compilation:: Compiling for debugging
1606 * Starting:: Starting your program
1607 * Arguments:: Your program's arguments
1608 * Environment:: Your program's environment
1610 * Working Directory:: Your program's working directory
1611 * Input/Output:: Your program's input and output
1612 * Attach:: Debugging an already-running process
1613 * Kill Process:: Killing the child process
1615 * Threads:: Debugging programs with multiple threads
1616 * Processes:: Debugging programs with multiple processes
1620 @section Compiling for debugging
1622 In order to debug a program effectively, you need to generate
1623 debugging information when you compile it. This debugging information
1624 is stored in the object file; it describes the data type of each
1625 variable or function and the correspondence between source line numbers
1626 and addresses in the executable code.
1628 To request debugging information, specify the @samp{-g} option when you run
1631 Most compilers do not include information about preprocessor macros in
1632 the debugging information if you specify the @option{-g} flag alone,
1633 because this information is rather large. Version 3.1 of @value{NGCC},
1634 the @sc{gnu} C compiler, provides macro information if you specify the
1635 options @option{-gdwarf-2} and @option{-g3}; the former option requests
1636 debugging information in the Dwarf 2 format, and the latter requests
1637 ``extra information''. In the future, we hope to find more compact ways
1638 to represent macro information, so that it can be included with
1641 Many C compilers are unable to handle the @samp{-g} and @samp{-O}
1642 options together. Using those compilers, you cannot generate optimized
1643 executables containing debugging information.
1645 @value{NGCC}, the @sc{gnu} C compiler, supports @samp{-g} with or
1646 without @samp{-O}, making it possible to debug optimized code. We
1647 recommend that you @emph{always} use @samp{-g} whenever you compile a
1648 program. You may think your program is correct, but there is no sense
1649 in pushing your luck.
1651 @cindex optimized code, debugging
1652 @cindex debugging optimized code
1653 When you debug a program compiled with @samp{-g -O}, remember that the
1654 optimizer is rearranging your code; the debugger shows you what is
1655 really there. Do not be too surprised when the execution path does not
1656 exactly match your source file! An extreme example: if you define a
1657 variable, but never use it, @value{GDBN} never sees that
1658 variable---because the compiler optimizes it out of existence.
1660 Some things do not work as well with @samp{-g -O} as with just
1661 @samp{-g}, particularly on machines with instruction scheduling. If in
1662 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1663 please report it to us as a bug (including a test case!).
1664 @xref{Variables}, for more information about debugging optimized code.
1666 Older versions of the @sc{gnu} C compiler permitted a variant option
1667 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1668 format; if your @sc{gnu} C compiler has this option, do not use it.
1672 @section Starting your program
1678 @kindex r @r{(@code{run})}
1681 Use the @code{run} command to start your program under @value{GDBN}.
1682 You must first specify the program name (except on VxWorks) with an
1683 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1684 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1685 (@pxref{Files, ,Commands to specify files}).
1689 If you are running your program in an execution environment that
1690 supports processes, @code{run} creates an inferior process and makes
1691 that process run your program. (In environments without processes,
1692 @code{run} jumps to the start of your program.)
1694 The execution of a program is affected by certain information it
1695 receives from its superior. @value{GDBN} provides ways to specify this
1696 information, which you must do @emph{before} starting your program. (You
1697 can change it after starting your program, but such changes only affect
1698 your program the next time you start it.) This information may be
1699 divided into four categories:
1702 @item The @emph{arguments.}
1703 Specify the arguments to give your program as the arguments of the
1704 @code{run} command. If a shell is available on your target, the shell
1705 is used to pass the arguments, so that you may use normal conventions
1706 (such as wildcard expansion or variable substitution) in describing
1708 In Unix systems, you can control which shell is used with the
1709 @code{SHELL} environment variable.
1710 @xref{Arguments, ,Your program's arguments}.
1712 @item The @emph{environment.}
1713 Your program normally inherits its environment from @value{GDBN}, but you can
1714 use the @value{GDBN} commands @code{set environment} and @code{unset
1715 environment} to change parts of the environment that affect
1716 your program. @xref{Environment, ,Your program's environment}.
1718 @item The @emph{working directory.}
1719 Your program inherits its working directory from @value{GDBN}. You can set
1720 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1721 @xref{Working Directory, ,Your program's working directory}.
1723 @item The @emph{standard input and output.}
1724 Your program normally uses the same device for standard input and
1725 standard output as @value{GDBN} is using. You can redirect input and output
1726 in the @code{run} command line, or you can use the @code{tty} command to
1727 set a different device for your program.
1728 @xref{Input/Output, ,Your program's input and output}.
1731 @emph{Warning:} While input and output redirection work, you cannot use
1732 pipes to pass the output of the program you are debugging to another
1733 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1737 When you issue the @code{run} command, your program begins to execute
1738 immediately. @xref{Stopping, ,Stopping and continuing}, for discussion
1739 of how to arrange for your program to stop. Once your program has
1740 stopped, you may call functions in your program, using the @code{print}
1741 or @code{call} commands. @xref{Data, ,Examining Data}.
1743 If the modification time of your symbol file has changed since the last
1744 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1745 table, and reads it again. When it does this, @value{GDBN} tries to retain
1746 your current breakpoints.
1751 @cindex run to main procedure
1752 The name of the main procedure can vary from language to language.
1753 With C or C@t{++}, the main procedure name is always @code{main}, but
1754 other languages such as Ada do not require a specific name for their
1755 main procedure. The debugger provides a convenient way to start the
1756 execution of the program and to stop at the beginning of the main
1757 procedure, depending on the language used.
1759 The @samp{start} command does the equivalent of setting a temporary
1760 breakpoint at the beginning of the main procedure and then invoking
1761 the @samp{run} command.
1763 Some programs contain an elaboration phase where some startup code is
1764 executed before the main program is called. This depends on the
1765 languages used to write your program. In C@t{++} for instance,
1766 constructors for static and global objects are executed before
1767 @code{main} is called. It is therefore possible that the debugger stops
1768 before reaching the main procedure. However, the temporary breakpoint
1769 will remain to halt execution.
1771 Specify the arguments to give to your program as arguments to the
1772 @samp{start} command. These arguments will be given verbatim to the
1773 underlying @samp{run} command. Note that the same arguments will be
1774 reused if no argument is provided during subsequent calls to
1775 @samp{start} or @samp{run}.
1777 It is sometimes necessary to debug the program during elaboration. In
1778 these cases, using the @code{start} command would stop the execution of
1779 your program too late, as the program would have already completed the
1780 elaboration phase. Under these circumstances, insert breakpoints in your
1781 elaboration code before running your program.
1785 @section Your program's arguments
1787 @cindex arguments (to your program)
1788 The arguments to your program can be specified by the arguments of the
1790 They are passed to a shell, which expands wildcard characters and
1791 performs redirection of I/O, and thence to your program. Your
1792 @code{SHELL} environment variable (if it exists) specifies what shell
1793 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1794 the default shell (@file{/bin/sh} on Unix).
1796 On non-Unix systems, the program is usually invoked directly by
1797 @value{GDBN}, which emulates I/O redirection via the appropriate system
1798 calls, and the wildcard characters are expanded by the startup code of
1799 the program, not by the shell.
1801 @code{run} with no arguments uses the same arguments used by the previous
1802 @code{run}, or those set by the @code{set args} command.
1807 Specify the arguments to be used the next time your program is run. If
1808 @code{set args} has no arguments, @code{run} executes your program
1809 with no arguments. Once you have run your program with arguments,
1810 using @code{set args} before the next @code{run} is the only way to run
1811 it again without arguments.
1815 Show the arguments to give your program when it is started.
1819 @section Your program's environment
1821 @cindex environment (of your program)
1822 The @dfn{environment} consists of a set of environment variables and
1823 their values. Environment variables conventionally record such things as
1824 your user name, your home directory, your terminal type, and your search
1825 path for programs to run. Usually you set up environment variables with
1826 the shell and they are inherited by all the other programs you run. When
1827 debugging, it can be useful to try running your program with a modified
1828 environment without having to start @value{GDBN} over again.
1832 @item path @var{directory}
1833 Add @var{directory} to the front of the @code{PATH} environment variable
1834 (the search path for executables) that will be passed to your program.
1835 The value of @code{PATH} used by @value{GDBN} does not change.
1836 You may specify several directory names, separated by whitespace or by a
1837 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1838 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1839 is moved to the front, so it is searched sooner.
1841 You can use the string @samp{$cwd} to refer to whatever is the current
1842 working directory at the time @value{GDBN} searches the path. If you
1843 use @samp{.} instead, it refers to the directory where you executed the
1844 @code{path} command. @value{GDBN} replaces @samp{.} in the
1845 @var{directory} argument (with the current path) before adding
1846 @var{directory} to the search path.
1847 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1848 @c document that, since repeating it would be a no-op.
1852 Display the list of search paths for executables (the @code{PATH}
1853 environment variable).
1855 @kindex show environment
1856 @item show environment @r{[}@var{varname}@r{]}
1857 Print the value of environment variable @var{varname} to be given to
1858 your program when it starts. If you do not supply @var{varname},
1859 print the names and values of all environment variables to be given to
1860 your program. You can abbreviate @code{environment} as @code{env}.
1862 @kindex set environment
1863 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1864 Set environment variable @var{varname} to @var{value}. The value
1865 changes for your program only, not for @value{GDBN} itself. @var{value} may
1866 be any string; the values of environment variables are just strings, and
1867 any interpretation is supplied by your program itself. The @var{value}
1868 parameter is optional; if it is eliminated, the variable is set to a
1870 @c "any string" here does not include leading, trailing
1871 @c blanks. Gnu asks: does anyone care?
1873 For example, this command:
1880 tells the debugged program, when subsequently run, that its user is named
1881 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
1882 are not actually required.)
1884 @kindex unset environment
1885 @item unset environment @var{varname}
1886 Remove variable @var{varname} from the environment to be passed to your
1887 program. This is different from @samp{set env @var{varname} =};
1888 @code{unset environment} removes the variable from the environment,
1889 rather than assigning it an empty value.
1892 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
1894 by your @code{SHELL} environment variable if it exists (or
1895 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
1896 that runs an initialization file---such as @file{.cshrc} for C-shell, or
1897 @file{.bashrc} for BASH---any variables you set in that file affect
1898 your program. You may wish to move setting of environment variables to
1899 files that are only run when you sign on, such as @file{.login} or
1902 @node Working Directory
1903 @section Your program's working directory
1905 @cindex working directory (of your program)
1906 Each time you start your program with @code{run}, it inherits its
1907 working directory from the current working directory of @value{GDBN}.
1908 The @value{GDBN} working directory is initially whatever it inherited
1909 from its parent process (typically the shell), but you can specify a new
1910 working directory in @value{GDBN} with the @code{cd} command.
1912 The @value{GDBN} working directory also serves as a default for the commands
1913 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
1918 @item cd @var{directory}
1919 Set the @value{GDBN} working directory to @var{directory}.
1923 Print the @value{GDBN} working directory.
1927 @section Your program's input and output
1932 By default, the program you run under @value{GDBN} does input and output to
1933 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
1934 to its own terminal modes to interact with you, but it records the terminal
1935 modes your program was using and switches back to them when you continue
1936 running your program.
1939 @kindex info terminal
1941 Displays information recorded by @value{GDBN} about the terminal modes your
1945 You can redirect your program's input and/or output using shell
1946 redirection with the @code{run} command. For example,
1953 starts your program, diverting its output to the file @file{outfile}.
1956 @cindex controlling terminal
1957 Another way to specify where your program should do input and output is
1958 with the @code{tty} command. This command accepts a file name as
1959 argument, and causes this file to be the default for future @code{run}
1960 commands. It also resets the controlling terminal for the child
1961 process, for future @code{run} commands. For example,
1968 directs that processes started with subsequent @code{run} commands
1969 default to do input and output on the terminal @file{/dev/ttyb} and have
1970 that as their controlling terminal.
1972 An explicit redirection in @code{run} overrides the @code{tty} command's
1973 effect on the input/output device, but not its effect on the controlling
1976 When you use the @code{tty} command or redirect input in the @code{run}
1977 command, only the input @emph{for your program} is affected. The input
1978 for @value{GDBN} still comes from your terminal.
1981 @section Debugging an already-running process
1986 @item attach @var{process-id}
1987 This command attaches to a running process---one that was started
1988 outside @value{GDBN}. (@code{info files} shows your active
1989 targets.) The command takes as argument a process ID. The usual way to
1990 find out the process-id of a Unix process is with the @code{ps} utility,
1991 or with the @samp{jobs -l} shell command.
1993 @code{attach} does not repeat if you press @key{RET} a second time after
1994 executing the command.
1997 To use @code{attach}, your program must be running in an environment
1998 which supports processes; for example, @code{attach} does not work for
1999 programs on bare-board targets that lack an operating system. You must
2000 also have permission to send the process a signal.
2002 When you use @code{attach}, the debugger finds the program running in
2003 the process first by looking in the current working directory, then (if
2004 the program is not found) by using the source file search path
2005 (@pxref{Source Path, ,Specifying source directories}). You can also use
2006 the @code{file} command to load the program. @xref{Files, ,Commands to
2009 The first thing @value{GDBN} does after arranging to debug the specified
2010 process is to stop it. You can examine and modify an attached process
2011 with all the @value{GDBN} commands that are ordinarily available when
2012 you start processes with @code{run}. You can insert breakpoints; you
2013 can step and continue; you can modify storage. If you would rather the
2014 process continue running, you may use the @code{continue} command after
2015 attaching @value{GDBN} to the process.
2020 When you have finished debugging the attached process, you can use the
2021 @code{detach} command to release it from @value{GDBN} control. Detaching
2022 the process continues its execution. After the @code{detach} command,
2023 that process and @value{GDBN} become completely independent once more, and you
2024 are ready to @code{attach} another process or start one with @code{run}.
2025 @code{detach} does not repeat if you press @key{RET} again after
2026 executing the command.
2029 If you exit @value{GDBN} or use the @code{run} command while you have an
2030 attached process, you kill that process. By default, @value{GDBN} asks
2031 for confirmation if you try to do either of these things; you can
2032 control whether or not you need to confirm by using the @code{set
2033 confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
2037 @section Killing the child process
2042 Kill the child process in which your program is running under @value{GDBN}.
2045 This command is useful if you wish to debug a core dump instead of a
2046 running process. @value{GDBN} ignores any core dump file while your program
2049 On some operating systems, a program cannot be executed outside @value{GDBN}
2050 while you have breakpoints set on it inside @value{GDBN}. You can use the
2051 @code{kill} command in this situation to permit running your program
2052 outside the debugger.
2054 The @code{kill} command is also useful if you wish to recompile and
2055 relink your program, since on many systems it is impossible to modify an
2056 executable file while it is running in a process. In this case, when you
2057 next type @code{run}, @value{GDBN} notices that the file has changed, and
2058 reads the symbol table again (while trying to preserve your current
2059 breakpoint settings).
2062 @section Debugging programs with multiple threads
2064 @cindex threads of execution
2065 @cindex multiple threads
2066 @cindex switching threads
2067 In some operating systems, such as HP-UX and Solaris, a single program
2068 may have more than one @dfn{thread} of execution. The precise semantics
2069 of threads differ from one operating system to another, but in general
2070 the threads of a single program are akin to multiple processes---except
2071 that they share one address space (that is, they can all examine and
2072 modify the same variables). On the other hand, each thread has its own
2073 registers and execution stack, and perhaps private memory.
2075 @value{GDBN} provides these facilities for debugging multi-thread
2079 @item automatic notification of new threads
2080 @item @samp{thread @var{threadno}}, a command to switch among threads
2081 @item @samp{info threads}, a command to inquire about existing threads
2082 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2083 a command to apply a command to a list of threads
2084 @item thread-specific breakpoints
2088 @emph{Warning:} These facilities are not yet available on every
2089 @value{GDBN} configuration where the operating system supports threads.
2090 If your @value{GDBN} does not support threads, these commands have no
2091 effect. For example, a system without thread support shows no output
2092 from @samp{info threads}, and always rejects the @code{thread} command,
2096 (@value{GDBP}) info threads
2097 (@value{GDBP}) thread 1
2098 Thread ID 1 not known. Use the "info threads" command to
2099 see the IDs of currently known threads.
2101 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2102 @c doesn't support threads"?
2105 @cindex focus of debugging
2106 @cindex current thread
2107 The @value{GDBN} thread debugging facility allows you to observe all
2108 threads while your program runs---but whenever @value{GDBN} takes
2109 control, one thread in particular is always the focus of debugging.
2110 This thread is called the @dfn{current thread}. Debugging commands show
2111 program information from the perspective of the current thread.
2113 @cindex @code{New} @var{systag} message
2114 @cindex thread identifier (system)
2115 @c FIXME-implementors!! It would be more helpful if the [New...] message
2116 @c included GDB's numeric thread handle, so you could just go to that
2117 @c thread without first checking `info threads'.
2118 Whenever @value{GDBN} detects a new thread in your program, it displays
2119 the target system's identification for the thread with a message in the
2120 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2121 whose form varies depending on the particular system. For example, on
2122 LynxOS, you might see
2125 [New process 35 thread 27]
2129 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2130 the @var{systag} is simply something like @samp{process 368}, with no
2133 @c FIXME!! (1) Does the [New...] message appear even for the very first
2134 @c thread of a program, or does it only appear for the
2135 @c second---i.e.@: when it becomes obvious we have a multithread
2137 @c (2) *Is* there necessarily a first thread always? Or do some
2138 @c multithread systems permit starting a program with multiple
2139 @c threads ab initio?
2141 @cindex thread number
2142 @cindex thread identifier (GDB)
2143 For debugging purposes, @value{GDBN} associates its own thread
2144 number---always a single integer---with each thread in your program.
2147 @kindex info threads
2149 Display a summary of all threads currently in your
2150 program. @value{GDBN} displays for each thread (in this order):
2153 @item the thread number assigned by @value{GDBN}
2155 @item the target system's thread identifier (@var{systag})
2157 @item the current stack frame summary for that thread
2161 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2162 indicates the current thread.
2166 @c end table here to get a little more width for example
2169 (@value{GDBP}) info threads
2170 3 process 35 thread 27 0x34e5 in sigpause ()
2171 2 process 35 thread 23 0x34e5 in sigpause ()
2172 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2178 @cindex debugging multithreaded programs (on HP-UX)
2179 @cindex thread identifier (GDB), on HP-UX
2180 For debugging purposes, @value{GDBN} associates its own thread
2181 number---a small integer assigned in thread-creation order---with each
2182 thread in your program.
2184 @cindex @code{New} @var{systag} message, on HP-UX
2185 @cindex thread identifier (system), on HP-UX
2186 @c FIXME-implementors!! It would be more helpful if the [New...] message
2187 @c included GDB's numeric thread handle, so you could just go to that
2188 @c thread without first checking `info threads'.
2189 Whenever @value{GDBN} detects a new thread in your program, it displays
2190 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2191 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2192 whose form varies depending on the particular system. For example, on
2196 [New thread 2 (system thread 26594)]
2200 when @value{GDBN} notices a new thread.
2203 @kindex info threads (HP-UX)
2205 Display a summary of all threads currently in your
2206 program. @value{GDBN} displays for each thread (in this order):
2209 @item the thread number assigned by @value{GDBN}
2211 @item the target system's thread identifier (@var{systag})
2213 @item the current stack frame summary for that thread
2217 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2218 indicates the current thread.
2222 @c end table here to get a little more width for example
2225 (@value{GDBP}) info threads
2226 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2228 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2229 from /usr/lib/libc.2
2230 1 system thread 27905 0x7b003498 in _brk () \@*
2231 from /usr/lib/libc.2
2235 @kindex thread @var{threadno}
2236 @item thread @var{threadno}
2237 Make thread number @var{threadno} the current thread. The command
2238 argument @var{threadno} is the internal @value{GDBN} thread number, as
2239 shown in the first field of the @samp{info threads} display.
2240 @value{GDBN} responds by displaying the system identifier of the thread
2241 you selected, and its current stack frame summary:
2244 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2245 (@value{GDBP}) thread 2
2246 [Switching to process 35 thread 23]
2247 0x34e5 in sigpause ()
2251 As with the @samp{[New @dots{}]} message, the form of the text after
2252 @samp{Switching to} depends on your system's conventions for identifying
2255 @item thread apply [@var{threadno}] [@var{all}] @var{args}
2256 The @code{thread apply} command allows you to apply a command to one or
2257 more threads. Specify the numbers of the threads that you want affected
2258 with the command argument @var{threadno}. @var{threadno} is the internal
2259 @value{GDBN} thread number, as shown in the first field of the @samp{info
2260 threads} display. To apply a command to all threads, use
2261 @code{thread apply all} @var{args}.
2264 @cindex automatic thread selection
2265 @cindex switching threads automatically
2266 @cindex threads, automatic switching
2267 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2268 signal, it automatically selects the thread where that breakpoint or
2269 signal happened. @value{GDBN} alerts you to the context switch with a
2270 message of the form @samp{[Switching to @var{systag}]} to identify the
2273 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2274 more information about how @value{GDBN} behaves when you stop and start
2275 programs with multiple threads.
2277 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2278 watchpoints in programs with multiple threads.
2281 @section Debugging programs with multiple processes
2283 @cindex fork, debugging programs which call
2284 @cindex multiple processes
2285 @cindex processes, multiple
2286 On most systems, @value{GDBN} has no special support for debugging
2287 programs which create additional processes using the @code{fork}
2288 function. When a program forks, @value{GDBN} will continue to debug the
2289 parent process and the child process will run unimpeded. If you have
2290 set a breakpoint in any code which the child then executes, the child
2291 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2292 will cause it to terminate.
2294 However, if you want to debug the child process there is a workaround
2295 which isn't too painful. Put a call to @code{sleep} in the code which
2296 the child process executes after the fork. It may be useful to sleep
2297 only if a certain environment variable is set, or a certain file exists,
2298 so that the delay need not occur when you don't want to run @value{GDBN}
2299 on the child. While the child is sleeping, use the @code{ps} program to
2300 get its process ID. Then tell @value{GDBN} (a new invocation of
2301 @value{GDBN} if you are also debugging the parent process) to attach to
2302 the child process (@pxref{Attach}). From that point on you can debug
2303 the child process just like any other process which you attached to.
2305 On some systems, @value{GDBN} provides support for debugging programs that
2306 create additional processes using the @code{fork} or @code{vfork} functions.
2307 Currently, the only platforms with this feature are HP-UX (11.x and later
2308 only?) and GNU/Linux (kernel version 2.5.60 and later).
2310 By default, when a program forks, @value{GDBN} will continue to debug
2311 the parent process and the child process will run unimpeded.
2313 If you want to follow the child process instead of the parent process,
2314 use the command @w{@code{set follow-fork-mode}}.
2317 @kindex set follow-fork-mode
2318 @item set follow-fork-mode @var{mode}
2319 Set the debugger response to a program call of @code{fork} or
2320 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2321 process. The @var{mode} can be:
2325 The original process is debugged after a fork. The child process runs
2326 unimpeded. This is the default.
2329 The new process is debugged after a fork. The parent process runs
2334 @item show follow-fork-mode
2335 Display the current debugger response to a @code{fork} or @code{vfork} call.
2338 If you ask to debug a child process and a @code{vfork} is followed by an
2339 @code{exec}, @value{GDBN} executes the new target up to the first
2340 breakpoint in the new target. If you have a breakpoint set on
2341 @code{main} in your original program, the breakpoint will also be set on
2342 the child process's @code{main}.
2344 When a child process is spawned by @code{vfork}, you cannot debug the
2345 child or parent until an @code{exec} call completes.
2347 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2348 call executes, the new target restarts. To restart the parent process,
2349 use the @code{file} command with the parent executable name as its
2352 You can use the @code{catch} command to make @value{GDBN} stop whenever
2353 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2354 Catchpoints, ,Setting catchpoints}.
2357 @chapter Stopping and Continuing
2359 The principal purposes of using a debugger are so that you can stop your
2360 program before it terminates; or so that, if your program runs into
2361 trouble, you can investigate and find out why.
2363 Inside @value{GDBN}, your program may stop for any of several reasons,
2364 such as a signal, a breakpoint, or reaching a new line after a
2365 @value{GDBN} command such as @code{step}. You may then examine and
2366 change variables, set new breakpoints or remove old ones, and then
2367 continue execution. Usually, the messages shown by @value{GDBN} provide
2368 ample explanation of the status of your program---but you can also
2369 explicitly request this information at any time.
2372 @kindex info program
2374 Display information about the status of your program: whether it is
2375 running or not, what process it is, and why it stopped.
2379 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2380 * Continuing and Stepping:: Resuming execution
2382 * Thread Stops:: Stopping and starting multi-thread programs
2386 @section Breakpoints, watchpoints, and catchpoints
2389 A @dfn{breakpoint} makes your program stop whenever a certain point in
2390 the program is reached. For each breakpoint, you can add conditions to
2391 control in finer detail whether your program stops. You can set
2392 breakpoints with the @code{break} command and its variants (@pxref{Set
2393 Breaks, ,Setting breakpoints}), to specify the place where your program
2394 should stop by line number, function name or exact address in the
2397 In HP-UX, SunOS 4.x, SVR4, and Alpha OSF/1 configurations, you can set
2398 breakpoints in shared libraries before the executable is run. There is
2399 a minor limitation on HP-UX systems: you must wait until the executable
2400 is run in order to set breakpoints in shared library routines that are
2401 not called directly by the program (for example, routines that are
2402 arguments in a @code{pthread_create} call).
2405 @cindex memory tracing
2406 @cindex breakpoint on memory address
2407 @cindex breakpoint on variable modification
2408 A @dfn{watchpoint} is a special breakpoint that stops your program
2409 when the value of an expression changes. You must use a different
2410 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
2411 watchpoints}), but aside from that, you can manage a watchpoint like
2412 any other breakpoint: you enable, disable, and delete both breakpoints
2413 and watchpoints using the same commands.
2415 You can arrange to have values from your program displayed automatically
2416 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2420 @cindex breakpoint on events
2421 A @dfn{catchpoint} is another special breakpoint that stops your program
2422 when a certain kind of event occurs, such as the throwing of a C@t{++}
2423 exception or the loading of a library. As with watchpoints, you use a
2424 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2425 catchpoints}), but aside from that, you can manage a catchpoint like any
2426 other breakpoint. (To stop when your program receives a signal, use the
2427 @code{handle} command; see @ref{Signals, ,Signals}.)
2429 @cindex breakpoint numbers
2430 @cindex numbers for breakpoints
2431 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2432 catchpoint when you create it; these numbers are successive integers
2433 starting with one. In many of the commands for controlling various
2434 features of breakpoints you use the breakpoint number to say which
2435 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2436 @dfn{disabled}; if disabled, it has no effect on your program until you
2439 @cindex breakpoint ranges
2440 @cindex ranges of breakpoints
2441 Some @value{GDBN} commands accept a range of breakpoints on which to
2442 operate. A breakpoint range is either a single breakpoint number, like
2443 @samp{5}, or two such numbers, in increasing order, separated by a
2444 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2445 all breakpoint in that range are operated on.
2448 * Set Breaks:: Setting breakpoints
2449 * Set Watchpoints:: Setting watchpoints
2450 * Set Catchpoints:: Setting catchpoints
2451 * Delete Breaks:: Deleting breakpoints
2452 * Disabling:: Disabling breakpoints
2453 * Conditions:: Break conditions
2454 * Break Commands:: Breakpoint command lists
2455 * Breakpoint Menus:: Breakpoint menus
2456 * Error in Breakpoints:: ``Cannot insert breakpoints''
2457 * Breakpoint related warnings:: ``Breakpoint address adjusted...''
2461 @subsection Setting breakpoints
2463 @c FIXME LMB what does GDB do if no code on line of breakpt?
2464 @c consider in particular declaration with/without initialization.
2466 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2469 @kindex b @r{(@code{break})}
2470 @vindex $bpnum@r{, convenience variable}
2471 @cindex latest breakpoint
2472 Breakpoints are set with the @code{break} command (abbreviated
2473 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2474 number of the breakpoint you've set most recently; see @ref{Convenience
2475 Vars,, Convenience variables}, for a discussion of what you can do with
2476 convenience variables.
2478 You have several ways to say where the breakpoint should go.
2481 @item break @var{function}
2482 Set a breakpoint at entry to function @var{function}.
2483 When using source languages that permit overloading of symbols, such as
2484 C@t{++}, @var{function} may refer to more than one possible place to break.
2485 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2487 @item break +@var{offset}
2488 @itemx break -@var{offset}
2489 Set a breakpoint some number of lines forward or back from the position
2490 at which execution stopped in the currently selected @dfn{stack frame}.
2491 (@xref{Frames, ,Frames}, for a description of stack frames.)
2493 @item break @var{linenum}
2494 Set a breakpoint at line @var{linenum} in the current source file.
2495 The current source file is the last file whose source text was printed.
2496 The breakpoint will stop your program just before it executes any of the
2499 @item break @var{filename}:@var{linenum}
2500 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2502 @item break @var{filename}:@var{function}
2503 Set a breakpoint at entry to function @var{function} found in file
2504 @var{filename}. Specifying a file name as well as a function name is
2505 superfluous except when multiple files contain similarly named
2508 @item break *@var{address}
2509 Set a breakpoint at address @var{address}. You can use this to set
2510 breakpoints in parts of your program which do not have debugging
2511 information or source files.
2514 When called without any arguments, @code{break} sets a breakpoint at
2515 the next instruction to be executed in the selected stack frame
2516 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2517 innermost, this makes your program stop as soon as control
2518 returns to that frame. This is similar to the effect of a
2519 @code{finish} command in the frame inside the selected frame---except
2520 that @code{finish} does not leave an active breakpoint. If you use
2521 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2522 the next time it reaches the current location; this may be useful
2525 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2526 least one instruction has been executed. If it did not do this, you
2527 would be unable to proceed past a breakpoint without first disabling the
2528 breakpoint. This rule applies whether or not the breakpoint already
2529 existed when your program stopped.
2531 @item break @dots{} if @var{cond}
2532 Set a breakpoint with condition @var{cond}; evaluate the expression
2533 @var{cond} each time the breakpoint is reached, and stop only if the
2534 value is nonzero---that is, if @var{cond} evaluates as true.
2535 @samp{@dots{}} stands for one of the possible arguments described
2536 above (or no argument) specifying where to break. @xref{Conditions,
2537 ,Break conditions}, for more information on breakpoint conditions.
2540 @item tbreak @var{args}
2541 Set a breakpoint enabled only for one stop. @var{args} are the
2542 same as for the @code{break} command, and the breakpoint is set in the same
2543 way, but the breakpoint is automatically deleted after the first time your
2544 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2547 @item hbreak @var{args}
2548 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2549 @code{break} command and the breakpoint is set in the same way, but the
2550 breakpoint requires hardware support and some target hardware may not
2551 have this support. The main purpose of this is EPROM/ROM code
2552 debugging, so you can set a breakpoint at an instruction without
2553 changing the instruction. This can be used with the new trap-generation
2554 provided by SPARClite DSU and some x86-based targets. These targets
2555 will generate traps when a program accesses some data or instruction
2556 address that is assigned to the debug registers. However the hardware
2557 breakpoint registers can take a limited number of breakpoints. For
2558 example, on the DSU, only two data breakpoints can be set at a time, and
2559 @value{GDBN} will reject this command if more than two are used. Delete
2560 or disable unused hardware breakpoints before setting new ones
2561 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2562 @xref{set remote hardware-breakpoint-limit}.
2566 @item thbreak @var{args}
2567 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2568 are the same as for the @code{hbreak} command and the breakpoint is set in
2569 the same way. However, like the @code{tbreak} command,
2570 the breakpoint is automatically deleted after the
2571 first time your program stops there. Also, like the @code{hbreak}
2572 command, the breakpoint requires hardware support and some target hardware
2573 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2574 See also @ref{Conditions, ,Break conditions}.
2577 @cindex regular expression
2578 @item rbreak @var{regex}
2579 Set breakpoints on all functions matching the regular expression
2580 @var{regex}. This command sets an unconditional breakpoint on all
2581 matches, printing a list of all breakpoints it set. Once these
2582 breakpoints are set, they are treated just like the breakpoints set with
2583 the @code{break} command. You can delete them, disable them, or make
2584 them conditional the same way as any other breakpoint.
2586 The syntax of the regular expression is the standard one used with tools
2587 like @file{grep}. Note that this is different from the syntax used by
2588 shells, so for instance @code{foo*} matches all functions that include
2589 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2590 @code{.*} leading and trailing the regular expression you supply, so to
2591 match only functions that begin with @code{foo}, use @code{^foo}.
2593 @cindex non-member C@t{++} functions, set breakpoint in
2594 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2595 breakpoints on overloaded functions that are not members of any special
2598 @cindex set breakpoints on all functions
2599 The @code{rbreak} command can be used to set breakpoints in
2600 @strong{all} the functions in a program, like this:
2603 (@value{GDBP}) rbreak .
2606 @kindex info breakpoints
2607 @cindex @code{$_} and @code{info breakpoints}
2608 @item info breakpoints @r{[}@var{n}@r{]}
2609 @itemx info break @r{[}@var{n}@r{]}
2610 @itemx info watchpoints @r{[}@var{n}@r{]}
2611 Print a table of all breakpoints, watchpoints, and catchpoints set and
2612 not deleted, with the following columns for each breakpoint:
2615 @item Breakpoint Numbers
2617 Breakpoint, watchpoint, or catchpoint.
2619 Whether the breakpoint is marked to be disabled or deleted when hit.
2620 @item Enabled or Disabled
2621 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2622 that are not enabled.
2624 Where the breakpoint is in your program, as a memory address. If the
2625 breakpoint is pending (see below for details) on a future load of a shared library, the address
2626 will be listed as @samp{<PENDING>}.
2628 Where the breakpoint is in the source for your program, as a file and
2629 line number. For a pending breakpoint, the original string passed to
2630 the breakpoint command will be listed as it cannot be resolved until
2631 the appropriate shared library is loaded in the future.
2635 If a breakpoint is conditional, @code{info break} shows the condition on
2636 the line following the affected breakpoint; breakpoint commands, if any,
2637 are listed after that. A pending breakpoint is allowed to have a condition
2638 specified for it. The condition is not parsed for validity until a shared
2639 library is loaded that allows the pending breakpoint to resolve to a
2643 @code{info break} with a breakpoint
2644 number @var{n} as argument lists only that breakpoint. The
2645 convenience variable @code{$_} and the default examining-address for
2646 the @code{x} command are set to the address of the last breakpoint
2647 listed (@pxref{Memory, ,Examining memory}).
2650 @code{info break} displays a count of the number of times the breakpoint
2651 has been hit. This is especially useful in conjunction with the
2652 @code{ignore} command. You can ignore a large number of breakpoint
2653 hits, look at the breakpoint info to see how many times the breakpoint
2654 was hit, and then run again, ignoring one less than that number. This
2655 will get you quickly to the last hit of that breakpoint.
2658 @value{GDBN} allows you to set any number of breakpoints at the same place in
2659 your program. There is nothing silly or meaningless about this. When
2660 the breakpoints are conditional, this is even useful
2661 (@pxref{Conditions, ,Break conditions}).
2663 @cindex pending breakpoints
2664 If a specified breakpoint location cannot be found, it may be due to the fact
2665 that the location is in a shared library that is yet to be loaded. In such
2666 a case, you may want @value{GDBN} to create a special breakpoint (known as
2667 a @dfn{pending breakpoint}) that
2668 attempts to resolve itself in the future when an appropriate shared library
2671 Pending breakpoints are useful to set at the start of your
2672 @value{GDBN} session for locations that you know will be dynamically loaded
2673 later by the program being debugged. When shared libraries are loaded,
2674 a check is made to see if the load resolves any pending breakpoint locations.
2675 If a pending breakpoint location gets resolved,
2676 a regular breakpoint is created and the original pending breakpoint is removed.
2678 @value{GDBN} provides some additional commands for controlling pending
2681 @kindex set breakpoint pending
2682 @kindex show breakpoint pending
2684 @item set breakpoint pending auto
2685 This is the default behavior. When @value{GDBN} cannot find the breakpoint
2686 location, it queries you whether a pending breakpoint should be created.
2688 @item set breakpoint pending on
2689 This indicates that an unrecognized breakpoint location should automatically
2690 result in a pending breakpoint being created.
2692 @item set breakpoint pending off
2693 This indicates that pending breakpoints are not to be created. Any
2694 unrecognized breakpoint location results in an error. This setting does
2695 not affect any pending breakpoints previously created.
2697 @item show breakpoint pending
2698 Show the current behavior setting for creating pending breakpoints.
2701 @cindex operations allowed on pending breakpoints
2702 Normal breakpoint operations apply to pending breakpoints as well. You may
2703 specify a condition for a pending breakpoint and/or commands to run when the
2704 breakpoint is reached. You can also enable or disable
2705 the pending breakpoint. When you specify a condition for a pending breakpoint,
2706 the parsing of the condition will be deferred until the point where the
2707 pending breakpoint location is resolved. Disabling a pending breakpoint
2708 tells @value{GDBN} to not attempt to resolve the breakpoint on any subsequent
2709 shared library load. When a pending breakpoint is re-enabled,
2710 @value{GDBN} checks to see if the location is already resolved.
2711 This is done because any number of shared library loads could have
2712 occurred since the time the breakpoint was disabled and one or more
2713 of these loads could resolve the location.
2715 @cindex negative breakpoint numbers
2716 @cindex internal @value{GDBN} breakpoints
2717 @value{GDBN} itself sometimes sets breakpoints in your program for
2718 special purposes, such as proper handling of @code{longjmp} (in C
2719 programs). These internal breakpoints are assigned negative numbers,
2720 starting with @code{-1}; @samp{info breakpoints} does not display them.
2721 You can see these breakpoints with the @value{GDBN} maintenance command
2722 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
2725 @node Set Watchpoints
2726 @subsection Setting watchpoints
2728 @cindex setting watchpoints
2729 @cindex software watchpoints
2730 @cindex hardware watchpoints
2731 You can use a watchpoint to stop execution whenever the value of an
2732 expression changes, without having to predict a particular place where
2735 Depending on your system, watchpoints may be implemented in software or
2736 hardware. @value{GDBN} does software watchpointing by single-stepping your
2737 program and testing the variable's value each time, which is hundreds of
2738 times slower than normal execution. (But this may still be worth it, to
2739 catch errors where you have no clue what part of your program is the
2742 On some systems, such as HP-UX, @sc{gnu}/Linux and some other x86-based targets,
2743 @value{GDBN} includes support for
2744 hardware watchpoints, which do not slow down the running of your
2749 @item watch @var{expr}
2750 Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
2751 is written into by the program and its value changes.
2754 @item rwatch @var{expr}
2755 Set a watchpoint that will break when watch @var{expr} is read by the program.
2758 @item awatch @var{expr}
2759 Set a watchpoint that will break when @var{expr} is either read or written into
2762 @kindex info watchpoints
2763 @item info watchpoints
2764 This command prints a list of watchpoints, breakpoints, and catchpoints;
2765 it is the same as @code{info break}.
2768 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
2769 watchpoints execute very quickly, and the debugger reports a change in
2770 value at the exact instruction where the change occurs. If @value{GDBN}
2771 cannot set a hardware watchpoint, it sets a software watchpoint, which
2772 executes more slowly and reports the change in value at the next
2773 statement, not the instruction, after the change occurs.
2775 When you issue the @code{watch} command, @value{GDBN} reports
2778 Hardware watchpoint @var{num}: @var{expr}
2782 if it was able to set a hardware watchpoint.
2784 Currently, the @code{awatch} and @code{rwatch} commands can only set
2785 hardware watchpoints, because accesses to data that don't change the
2786 value of the watched expression cannot be detected without examining
2787 every instruction as it is being executed, and @value{GDBN} does not do
2788 that currently. If @value{GDBN} finds that it is unable to set a
2789 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
2790 will print a message like this:
2793 Expression cannot be implemented with read/access watchpoint.
2796 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
2797 data type of the watched expression is wider than what a hardware
2798 watchpoint on the target machine can handle. For example, some systems
2799 can only watch regions that are up to 4 bytes wide; on such systems you
2800 cannot set hardware watchpoints for an expression that yields a
2801 double-precision floating-point number (which is typically 8 bytes
2802 wide). As a work-around, it might be possible to break the large region
2803 into a series of smaller ones and watch them with separate watchpoints.
2805 If you set too many hardware watchpoints, @value{GDBN} might be unable
2806 to insert all of them when you resume the execution of your program.
2807 Since the precise number of active watchpoints is unknown until such
2808 time as the program is about to be resumed, @value{GDBN} might not be
2809 able to warn you about this when you set the watchpoints, and the
2810 warning will be printed only when the program is resumed:
2813 Hardware watchpoint @var{num}: Could not insert watchpoint
2817 If this happens, delete or disable some of the watchpoints.
2819 The SPARClite DSU will generate traps when a program accesses some data
2820 or instruction address that is assigned to the debug registers. For the
2821 data addresses, DSU facilitates the @code{watch} command. However the
2822 hardware breakpoint registers can only take two data watchpoints, and
2823 both watchpoints must be the same kind. For example, you can set two
2824 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
2825 @strong{or} two with @code{awatch} commands, but you cannot set one
2826 watchpoint with one command and the other with a different command.
2827 @value{GDBN} will reject the command if you try to mix watchpoints.
2828 Delete or disable unused watchpoint commands before setting new ones.
2830 If you call a function interactively using @code{print} or @code{call},
2831 any watchpoints you have set will be inactive until @value{GDBN} reaches another
2832 kind of breakpoint or the call completes.
2834 @value{GDBN} automatically deletes watchpoints that watch local
2835 (automatic) variables, or expressions that involve such variables, when
2836 they go out of scope, that is, when the execution leaves the block in
2837 which these variables were defined. In particular, when the program
2838 being debugged terminates, @emph{all} local variables go out of scope,
2839 and so only watchpoints that watch global variables remain set. If you
2840 rerun the program, you will need to set all such watchpoints again. One
2841 way of doing that would be to set a code breakpoint at the entry to the
2842 @code{main} function and when it breaks, set all the watchpoints.
2845 @cindex watchpoints and threads
2846 @cindex threads and watchpoints
2847 @emph{Warning:} In multi-thread programs, watchpoints have only limited
2848 usefulness. With the current watchpoint implementation, @value{GDBN}
2849 can only watch the value of an expression @emph{in a single thread}. If
2850 you are confident that the expression can only change due to the current
2851 thread's activity (and if you are also confident that no other thread
2852 can become current), then you can use watchpoints as usual. However,
2853 @value{GDBN} may not notice when a non-current thread's activity changes
2856 @c FIXME: this is almost identical to the previous paragraph.
2857 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
2858 have only limited usefulness. If @value{GDBN} creates a software
2859 watchpoint, it can only watch the value of an expression @emph{in a
2860 single thread}. If you are confident that the expression can only
2861 change due to the current thread's activity (and if you are also
2862 confident that no other thread can become current), then you can use
2863 software watchpoints as usual. However, @value{GDBN} may not notice
2864 when a non-current thread's activity changes the expression. (Hardware
2865 watchpoints, in contrast, watch an expression in all threads.)
2868 @xref{set remote hardware-watchpoint-limit}.
2870 @node Set Catchpoints
2871 @subsection Setting catchpoints
2872 @cindex catchpoints, setting
2873 @cindex exception handlers
2874 @cindex event handling
2876 You can use @dfn{catchpoints} to cause the debugger to stop for certain
2877 kinds of program events, such as C@t{++} exceptions or the loading of a
2878 shared library. Use the @code{catch} command to set a catchpoint.
2882 @item catch @var{event}
2883 Stop when @var{event} occurs. @var{event} can be any of the following:
2886 @cindex stop on C@t{++} exceptions
2887 The throwing of a C@t{++} exception.
2890 The catching of a C@t{++} exception.
2893 @cindex break on fork/exec
2894 A call to @code{exec}. This is currently only available for HP-UX.
2897 A call to @code{fork}. This is currently only available for HP-UX.
2900 A call to @code{vfork}. This is currently only available for HP-UX.
2903 @itemx load @var{libname}
2904 @cindex break on load/unload of shared library
2905 The dynamic loading of any shared library, or the loading of the library
2906 @var{libname}. This is currently only available for HP-UX.
2909 @itemx unload @var{libname}
2910 The unloading of any dynamically loaded shared library, or the unloading
2911 of the library @var{libname}. This is currently only available for HP-UX.
2914 @item tcatch @var{event}
2915 Set a catchpoint that is enabled only for one stop. The catchpoint is
2916 automatically deleted after the first time the event is caught.
2920 Use the @code{info break} command to list the current catchpoints.
2922 There are currently some limitations to C@t{++} exception handling
2923 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
2927 If you call a function interactively, @value{GDBN} normally returns
2928 control to you when the function has finished executing. If the call
2929 raises an exception, however, the call may bypass the mechanism that
2930 returns control to you and cause your program either to abort or to
2931 simply continue running until it hits a breakpoint, catches a signal
2932 that @value{GDBN} is listening for, or exits. This is the case even if
2933 you set a catchpoint for the exception; catchpoints on exceptions are
2934 disabled within interactive calls.
2937 You cannot raise an exception interactively.
2940 You cannot install an exception handler interactively.
2943 @cindex raise exceptions
2944 Sometimes @code{catch} is not the best way to debug exception handling:
2945 if you need to know exactly where an exception is raised, it is better to
2946 stop @emph{before} the exception handler is called, since that way you
2947 can see the stack before any unwinding takes place. If you set a
2948 breakpoint in an exception handler instead, it may not be easy to find
2949 out where the exception was raised.
2951 To stop just before an exception handler is called, you need some
2952 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
2953 raised by calling a library function named @code{__raise_exception}
2954 which has the following ANSI C interface:
2957 /* @var{addr} is where the exception identifier is stored.
2958 @var{id} is the exception identifier. */
2959 void __raise_exception (void **addr, void *id);
2963 To make the debugger catch all exceptions before any stack
2964 unwinding takes place, set a breakpoint on @code{__raise_exception}
2965 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
2967 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
2968 that depends on the value of @var{id}, you can stop your program when
2969 a specific exception is raised. You can use multiple conditional
2970 breakpoints to stop your program when any of a number of exceptions are
2975 @subsection Deleting breakpoints
2977 @cindex clearing breakpoints, watchpoints, catchpoints
2978 @cindex deleting breakpoints, watchpoints, catchpoints
2979 It is often necessary to eliminate a breakpoint, watchpoint, or
2980 catchpoint once it has done its job and you no longer want your program
2981 to stop there. This is called @dfn{deleting} the breakpoint. A
2982 breakpoint that has been deleted no longer exists; it is forgotten.
2984 With the @code{clear} command you can delete breakpoints according to
2985 where they are in your program. With the @code{delete} command you can
2986 delete individual breakpoints, watchpoints, or catchpoints by specifying
2987 their breakpoint numbers.
2989 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
2990 automatically ignores breakpoints on the first instruction to be executed
2991 when you continue execution without changing the execution address.
2996 Delete any breakpoints at the next instruction to be executed in the
2997 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
2998 the innermost frame is selected, this is a good way to delete a
2999 breakpoint where your program just stopped.
3001 @item clear @var{function}
3002 @itemx clear @var{filename}:@var{function}
3003 Delete any breakpoints set at entry to the function @var{function}.
3005 @item clear @var{linenum}
3006 @itemx clear @var{filename}:@var{linenum}
3007 Delete any breakpoints set at or within the code of the specified line.
3009 @cindex delete breakpoints
3011 @kindex d @r{(@code{delete})}
3012 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3013 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3014 ranges specified as arguments. If no argument is specified, delete all
3015 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3016 confirm off}). You can abbreviate this command as @code{d}.
3020 @subsection Disabling breakpoints
3022 @cindex enable/disable a breakpoint
3023 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3024 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3025 it had been deleted, but remembers the information on the breakpoint so
3026 that you can @dfn{enable} it again later.
3028 You disable and enable breakpoints, watchpoints, and catchpoints with
3029 the @code{enable} and @code{disable} commands, optionally specifying one
3030 or more breakpoint numbers as arguments. Use @code{info break} or
3031 @code{info watch} to print a list of breakpoints, watchpoints, and
3032 catchpoints if you do not know which numbers to use.
3034 A breakpoint, watchpoint, or catchpoint can have any of four different
3035 states of enablement:
3039 Enabled. The breakpoint stops your program. A breakpoint set
3040 with the @code{break} command starts out in this state.
3042 Disabled. The breakpoint has no effect on your program.
3044 Enabled once. The breakpoint stops your program, but then becomes
3047 Enabled for deletion. The breakpoint stops your program, but
3048 immediately after it does so it is deleted permanently. A breakpoint
3049 set with the @code{tbreak} command starts out in this state.
3052 You can use the following commands to enable or disable breakpoints,
3053 watchpoints, and catchpoints:
3057 @kindex dis @r{(@code{disable})}
3058 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3059 Disable the specified breakpoints---or all breakpoints, if none are
3060 listed. A disabled breakpoint has no effect but is not forgotten. All
3061 options such as ignore-counts, conditions and commands are remembered in
3062 case the breakpoint is enabled again later. You may abbreviate
3063 @code{disable} as @code{dis}.
3066 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3067 Enable the specified breakpoints (or all defined breakpoints). They
3068 become effective once again in stopping your program.
3070 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3071 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3072 of these breakpoints immediately after stopping your program.
3074 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3075 Enable the specified breakpoints to work once, then die. @value{GDBN}
3076 deletes any of these breakpoints as soon as your program stops there.
3079 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3080 @c confusing: tbreak is also initially enabled.
3081 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3082 ,Setting breakpoints}), breakpoints that you set are initially enabled;
3083 subsequently, they become disabled or enabled only when you use one of
3084 the commands above. (The command @code{until} can set and delete a
3085 breakpoint of its own, but it does not change the state of your other
3086 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3090 @subsection Break conditions
3091 @cindex conditional breakpoints
3092 @cindex breakpoint conditions
3094 @c FIXME what is scope of break condition expr? Context where wanted?
3095 @c in particular for a watchpoint?
3096 The simplest sort of breakpoint breaks every time your program reaches a
3097 specified place. You can also specify a @dfn{condition} for a
3098 breakpoint. A condition is just a Boolean expression in your
3099 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3100 a condition evaluates the expression each time your program reaches it,
3101 and your program stops only if the condition is @emph{true}.
3103 This is the converse of using assertions for program validation; in that
3104 situation, you want to stop when the assertion is violated---that is,
3105 when the condition is false. In C, if you want to test an assertion expressed
3106 by the condition @var{assert}, you should set the condition
3107 @samp{! @var{assert}} on the appropriate breakpoint.
3109 Conditions are also accepted for watchpoints; you may not need them,
3110 since a watchpoint is inspecting the value of an expression anyhow---but
3111 it might be simpler, say, to just set a watchpoint on a variable name,
3112 and specify a condition that tests whether the new value is an interesting
3115 Break conditions can have side effects, and may even call functions in
3116 your program. This can be useful, for example, to activate functions
3117 that log program progress, or to use your own print functions to
3118 format special data structures. The effects are completely predictable
3119 unless there is another enabled breakpoint at the same address. (In
3120 that case, @value{GDBN} might see the other breakpoint first and stop your
3121 program without checking the condition of this one.) Note that
3122 breakpoint commands are usually more convenient and flexible than break
3124 purpose of performing side effects when a breakpoint is reached
3125 (@pxref{Break Commands, ,Breakpoint command lists}).
3127 Break conditions can be specified when a breakpoint is set, by using
3128 @samp{if} in the arguments to the @code{break} command. @xref{Set
3129 Breaks, ,Setting breakpoints}. They can also be changed at any time
3130 with the @code{condition} command.
3132 You can also use the @code{if} keyword with the @code{watch} command.
3133 The @code{catch} command does not recognize the @code{if} keyword;
3134 @code{condition} is the only way to impose a further condition on a
3139 @item condition @var{bnum} @var{expression}
3140 Specify @var{expression} as the break condition for breakpoint,
3141 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3142 breakpoint @var{bnum} stops your program only if the value of
3143 @var{expression} is true (nonzero, in C). When you use
3144 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3145 syntactic correctness, and to determine whether symbols in it have
3146 referents in the context of your breakpoint. If @var{expression} uses
3147 symbols not referenced in the context of the breakpoint, @value{GDBN}
3148 prints an error message:
3151 No symbol "foo" in current context.
3156 not actually evaluate @var{expression} at the time the @code{condition}
3157 command (or a command that sets a breakpoint with a condition, like
3158 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3160 @item condition @var{bnum}
3161 Remove the condition from breakpoint number @var{bnum}. It becomes
3162 an ordinary unconditional breakpoint.
3165 @cindex ignore count (of breakpoint)
3166 A special case of a breakpoint condition is to stop only when the
3167 breakpoint has been reached a certain number of times. This is so
3168 useful that there is a special way to do it, using the @dfn{ignore
3169 count} of the breakpoint. Every breakpoint has an ignore count, which
3170 is an integer. Most of the time, the ignore count is zero, and
3171 therefore has no effect. But if your program reaches a breakpoint whose
3172 ignore count is positive, then instead of stopping, it just decrements
3173 the ignore count by one and continues. As a result, if the ignore count
3174 value is @var{n}, the breakpoint does not stop the next @var{n} times
3175 your program reaches it.
3179 @item ignore @var{bnum} @var{count}
3180 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3181 The next @var{count} times the breakpoint is reached, your program's
3182 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3185 To make the breakpoint stop the next time it is reached, specify
3188 When you use @code{continue} to resume execution of your program from a
3189 breakpoint, you can specify an ignore count directly as an argument to
3190 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3191 Stepping,,Continuing and stepping}.
3193 If a breakpoint has a positive ignore count and a condition, the
3194 condition is not checked. Once the ignore count reaches zero,
3195 @value{GDBN} resumes checking the condition.
3197 You could achieve the effect of the ignore count with a condition such
3198 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3199 is decremented each time. @xref{Convenience Vars, ,Convenience
3203 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3206 @node Break Commands
3207 @subsection Breakpoint command lists
3209 @cindex breakpoint commands
3210 You can give any breakpoint (or watchpoint or catchpoint) a series of
3211 commands to execute when your program stops due to that breakpoint. For
3212 example, you might want to print the values of certain expressions, or
3213 enable other breakpoints.
3218 @item commands @r{[}@var{bnum}@r{]}
3219 @itemx @dots{} @var{command-list} @dots{}
3221 Specify a list of commands for breakpoint number @var{bnum}. The commands
3222 themselves appear on the following lines. Type a line containing just
3223 @code{end} to terminate the commands.
3225 To remove all commands from a breakpoint, type @code{commands} and
3226 follow it immediately with @code{end}; that is, give no commands.
3228 With no @var{bnum} argument, @code{commands} refers to the last
3229 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3230 recently encountered).
3233 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3234 disabled within a @var{command-list}.
3236 You can use breakpoint commands to start your program up again. Simply
3237 use the @code{continue} command, or @code{step}, or any other command
3238 that resumes execution.
3240 Any other commands in the command list, after a command that resumes
3241 execution, are ignored. This is because any time you resume execution
3242 (even with a simple @code{next} or @code{step}), you may encounter
3243 another breakpoint---which could have its own command list, leading to
3244 ambiguities about which list to execute.
3247 If the first command you specify in a command list is @code{silent}, the
3248 usual message about stopping at a breakpoint is not printed. This may
3249 be desirable for breakpoints that are to print a specific message and
3250 then continue. If none of the remaining commands print anything, you
3251 see no sign that the breakpoint was reached. @code{silent} is
3252 meaningful only at the beginning of a breakpoint command list.
3254 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3255 print precisely controlled output, and are often useful in silent
3256 breakpoints. @xref{Output, ,Commands for controlled output}.
3258 For example, here is how you could use breakpoint commands to print the
3259 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3265 printf "x is %d\n",x
3270 One application for breakpoint commands is to compensate for one bug so
3271 you can test for another. Put a breakpoint just after the erroneous line
3272 of code, give it a condition to detect the case in which something
3273 erroneous has been done, and give it commands to assign correct values
3274 to any variables that need them. End with the @code{continue} command
3275 so that your program does not stop, and start with the @code{silent}
3276 command so that no output is produced. Here is an example:
3287 @node Breakpoint Menus
3288 @subsection Breakpoint menus
3290 @cindex symbol overloading
3292 Some programming languages (notably C@t{++} and Objective-C) permit a
3293 single function name
3294 to be defined several times, for application in different contexts.
3295 This is called @dfn{overloading}. When a function name is overloaded,
3296 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3297 a breakpoint. If you realize this is a problem, you can use
3298 something like @samp{break @var{function}(@var{types})} to specify which
3299 particular version of the function you want. Otherwise, @value{GDBN} offers
3300 you a menu of numbered choices for different possible breakpoints, and
3301 waits for your selection with the prompt @samp{>}. The first two
3302 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3303 sets a breakpoint at each definition of @var{function}, and typing
3304 @kbd{0} aborts the @code{break} command without setting any new
3307 For example, the following session excerpt shows an attempt to set a
3308 breakpoint at the overloaded symbol @code{String::after}.
3309 We choose three particular definitions of that function name:
3311 @c FIXME! This is likely to change to show arg type lists, at least
3314 (@value{GDBP}) b String::after
3317 [2] file:String.cc; line number:867
3318 [3] file:String.cc; line number:860
3319 [4] file:String.cc; line number:875
3320 [5] file:String.cc; line number:853
3321 [6] file:String.cc; line number:846
3322 [7] file:String.cc; line number:735
3324 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3325 Breakpoint 2 at 0xb344: file String.cc, line 875.
3326 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3327 Multiple breakpoints were set.
3328 Use the "delete" command to delete unwanted
3334 @c @ifclear BARETARGET
3335 @node Error in Breakpoints
3336 @subsection ``Cannot insert breakpoints''
3338 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3340 Under some operating systems, breakpoints cannot be used in a program if
3341 any other process is running that program. In this situation,
3342 attempting to run or continue a program with a breakpoint causes
3343 @value{GDBN} to print an error message:
3346 Cannot insert breakpoints.
3347 The same program may be running in another process.
3350 When this happens, you have three ways to proceed:
3354 Remove or disable the breakpoints, then continue.
3357 Suspend @value{GDBN}, and copy the file containing your program to a new
3358 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3359 that @value{GDBN} should run your program under that name.
3360 Then start your program again.
3363 Relink your program so that the text segment is nonsharable, using the
3364 linker option @samp{-N}. The operating system limitation may not apply
3365 to nonsharable executables.
3369 A similar message can be printed if you request too many active
3370 hardware-assisted breakpoints and watchpoints:
3372 @c FIXME: the precise wording of this message may change; the relevant
3373 @c source change is not committed yet (Sep 3, 1999).
3375 Stopped; cannot insert breakpoints.
3376 You may have requested too many hardware breakpoints and watchpoints.
3380 This message is printed when you attempt to resume the program, since
3381 only then @value{GDBN} knows exactly how many hardware breakpoints and
3382 watchpoints it needs to insert.
3384 When this message is printed, you need to disable or remove some of the
3385 hardware-assisted breakpoints and watchpoints, and then continue.
3387 @node Breakpoint related warnings
3388 @subsection ``Breakpoint address adjusted...''
3389 @cindex breakpoint address adjusted
3391 Some processor architectures place constraints on the addresses at
3392 which breakpoints may be placed. For architectures thus constrained,
3393 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3394 with the constraints dictated by the architecture.
3396 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3397 a VLIW architecture in which a number of RISC-like instructions may be
3398 bundled together for parallel execution. The FR-V architecture
3399 constrains the location of a breakpoint instruction within such a
3400 bundle to the instruction with the lowest address. @value{GDBN}
3401 honors this constraint by adjusting a breakpoint's address to the
3402 first in the bundle.
3404 It is not uncommon for optimized code to have bundles which contain
3405 instructions from different source statements, thus it may happen that
3406 a breakpoint's address will be adjusted from one source statement to
3407 another. Since this adjustment may significantly alter @value{GDBN}'s
3408 breakpoint related behavior from what the user expects, a warning is
3409 printed when the breakpoint is first set and also when the breakpoint
3412 A warning like the one below is printed when setting a breakpoint
3413 that's been subject to address adjustment:
3416 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3419 Such warnings are printed both for user settable and @value{GDBN}'s
3420 internal breakpoints. If you see one of these warnings, you should
3421 verify that a breakpoint set at the adjusted address will have the
3422 desired affect. If not, the breakpoint in question may be removed and
3423 other breakpoints may be set which will have the desired behavior.
3424 E.g., it may be sufficient to place the breakpoint at a later
3425 instruction. A conditional breakpoint may also be useful in some
3426 cases to prevent the breakpoint from triggering too often.
3428 @value{GDBN} will also issue a warning when stopping at one of these
3429 adjusted breakpoints:
3432 warning: Breakpoint 1 address previously adjusted from 0x00010414
3436 When this warning is encountered, it may be too late to take remedial
3437 action except in cases where the breakpoint is hit earlier or more
3438 frequently than expected.
3440 @node Continuing and Stepping
3441 @section Continuing and stepping
3445 @cindex resuming execution
3446 @dfn{Continuing} means resuming program execution until your program
3447 completes normally. In contrast, @dfn{stepping} means executing just
3448 one more ``step'' of your program, where ``step'' may mean either one
3449 line of source code, or one machine instruction (depending on what
3450 particular command you use). Either when continuing or when stepping,
3451 your program may stop even sooner, due to a breakpoint or a signal. (If
3452 it stops due to a signal, you may want to use @code{handle}, or use
3453 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3457 @kindex c @r{(@code{continue})}
3458 @kindex fg @r{(resume foreground execution)}
3459 @item continue @r{[}@var{ignore-count}@r{]}
3460 @itemx c @r{[}@var{ignore-count}@r{]}
3461 @itemx fg @r{[}@var{ignore-count}@r{]}
3462 Resume program execution, at the address where your program last stopped;
3463 any breakpoints set at that address are bypassed. The optional argument
3464 @var{ignore-count} allows you to specify a further number of times to
3465 ignore a breakpoint at this location; its effect is like that of
3466 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3468 The argument @var{ignore-count} is meaningful only when your program
3469 stopped due to a breakpoint. At other times, the argument to
3470 @code{continue} is ignored.
3472 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3473 debugged program is deemed to be the foreground program) are provided
3474 purely for convenience, and have exactly the same behavior as
3478 To resume execution at a different place, you can use @code{return}
3479 (@pxref{Returning, ,Returning from a function}) to go back to the
3480 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3481 different address}) to go to an arbitrary location in your program.
3483 A typical technique for using stepping is to set a breakpoint
3484 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3485 beginning of the function or the section of your program where a problem
3486 is believed to lie, run your program until it stops at that breakpoint,
3487 and then step through the suspect area, examining the variables that are
3488 interesting, until you see the problem happen.
3492 @kindex s @r{(@code{step})}
3494 Continue running your program until control reaches a different source
3495 line, then stop it and return control to @value{GDBN}. This command is
3496 abbreviated @code{s}.
3499 @c "without debugging information" is imprecise; actually "without line
3500 @c numbers in the debugging information". (gcc -g1 has debugging info but
3501 @c not line numbers). But it seems complex to try to make that
3502 @c distinction here.
3503 @emph{Warning:} If you use the @code{step} command while control is
3504 within a function that was compiled without debugging information,
3505 execution proceeds until control reaches a function that does have
3506 debugging information. Likewise, it will not step into a function which
3507 is compiled without debugging information. To step through functions
3508 without debugging information, use the @code{stepi} command, described
3512 The @code{step} command only stops at the first instruction of a source
3513 line. This prevents the multiple stops that could otherwise occur in
3514 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3515 to stop if a function that has debugging information is called within
3516 the line. In other words, @code{step} @emph{steps inside} any functions
3517 called within the line.
3519 Also, the @code{step} command only enters a function if there is line
3520 number information for the function. Otherwise it acts like the
3521 @code{next} command. This avoids problems when using @code{cc -gl}
3522 on MIPS machines. Previously, @code{step} entered subroutines if there
3523 was any debugging information about the routine.
3525 @item step @var{count}
3526 Continue running as in @code{step}, but do so @var{count} times. If a
3527 breakpoint is reached, or a signal not related to stepping occurs before
3528 @var{count} steps, stepping stops right away.
3531 @kindex n @r{(@code{next})}
3532 @item next @r{[}@var{count}@r{]}
3533 Continue to the next source line in the current (innermost) stack frame.
3534 This is similar to @code{step}, but function calls that appear within
3535 the line of code are executed without stopping. Execution stops when
3536 control reaches a different line of code at the original stack level
3537 that was executing when you gave the @code{next} command. This command
3538 is abbreviated @code{n}.
3540 An argument @var{count} is a repeat count, as for @code{step}.
3543 @c FIX ME!! Do we delete this, or is there a way it fits in with
3544 @c the following paragraph? --- Vctoria
3546 @c @code{next} within a function that lacks debugging information acts like
3547 @c @code{step}, but any function calls appearing within the code of the
3548 @c function are executed without stopping.
3550 The @code{next} command only stops at the first instruction of a
3551 source line. This prevents multiple stops that could otherwise occur in
3552 @code{switch} statements, @code{for} loops, etc.
3554 @kindex set step-mode
3556 @cindex functions without line info, and stepping
3557 @cindex stepping into functions with no line info
3558 @itemx set step-mode on
3559 The @code{set step-mode on} command causes the @code{step} command to
3560 stop at the first instruction of a function which contains no debug line
3561 information rather than stepping over it.
3563 This is useful in cases where you may be interested in inspecting the
3564 machine instructions of a function which has no symbolic info and do not
3565 want @value{GDBN} to automatically skip over this function.
3567 @item set step-mode off
3568 Causes the @code{step} command to step over any functions which contains no
3569 debug information. This is the default.
3573 Continue running until just after function in the selected stack frame
3574 returns. Print the returned value (if any).
3576 Contrast this with the @code{return} command (@pxref{Returning,
3577 ,Returning from a function}).
3580 @kindex u @r{(@code{until})}
3583 Continue running until a source line past the current line, in the
3584 current stack frame, is reached. This command is used to avoid single
3585 stepping through a loop more than once. It is like the @code{next}
3586 command, except that when @code{until} encounters a jump, it
3587 automatically continues execution until the program counter is greater
3588 than the address of the jump.
3590 This means that when you reach the end of a loop after single stepping
3591 though it, @code{until} makes your program continue execution until it
3592 exits the loop. In contrast, a @code{next} command at the end of a loop
3593 simply steps back to the beginning of the loop, which forces you to step
3594 through the next iteration.
3596 @code{until} always stops your program if it attempts to exit the current
3599 @code{until} may produce somewhat counterintuitive results if the order
3600 of machine code does not match the order of the source lines. For
3601 example, in the following excerpt from a debugging session, the @code{f}
3602 (@code{frame}) command shows that execution is stopped at line
3603 @code{206}; yet when we use @code{until}, we get to line @code{195}:
3607 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
3609 (@value{GDBP}) until
3610 195 for ( ; argc > 0; NEXTARG) @{
3613 This happened because, for execution efficiency, the compiler had
3614 generated code for the loop closure test at the end, rather than the
3615 start, of the loop---even though the test in a C @code{for}-loop is
3616 written before the body of the loop. The @code{until} command appeared
3617 to step back to the beginning of the loop when it advanced to this
3618 expression; however, it has not really gone to an earlier
3619 statement---not in terms of the actual machine code.
3621 @code{until} with no argument works by means of single
3622 instruction stepping, and hence is slower than @code{until} with an
3625 @item until @var{location}
3626 @itemx u @var{location}
3627 Continue running your program until either the specified location is
3628 reached, or the current stack frame returns. @var{location} is any of
3629 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
3630 ,Setting breakpoints}). This form of the command uses breakpoints, and
3631 hence is quicker than @code{until} without an argument. The specified
3632 location is actually reached only if it is in the current frame. This
3633 implies that @code{until} can be used to skip over recursive function
3634 invocations. For instance in the code below, if the current location is
3635 line @code{96}, issuing @code{until 99} will execute the program up to
3636 line @code{99} in the same invocation of factorial, i.e. after the inner
3637 invocations have returned.
3640 94 int factorial (int value)
3642 96 if (value > 1) @{
3643 97 value *= factorial (value - 1);
3650 @kindex advance @var{location}
3651 @itemx advance @var{location}
3652 Continue running the program up to the given location. An argument is
3653 required, anything of the same form as arguments for the @code{break}
3654 command. Execution will also stop upon exit from the current stack
3655 frame. This command is similar to @code{until}, but @code{advance} will
3656 not skip over recursive function calls, and the target location doesn't
3657 have to be in the same frame as the current one.
3661 @kindex si @r{(@code{stepi})}
3663 @itemx stepi @var{arg}
3665 Execute one machine instruction, then stop and return to the debugger.
3667 It is often useful to do @samp{display/i $pc} when stepping by machine
3668 instructions. This makes @value{GDBN} automatically display the next
3669 instruction to be executed, each time your program stops. @xref{Auto
3670 Display,, Automatic display}.
3672 An argument is a repeat count, as in @code{step}.
3676 @kindex ni @r{(@code{nexti})}
3678 @itemx nexti @var{arg}
3680 Execute one machine instruction, but if it is a function call,
3681 proceed until the function returns.
3683 An argument is a repeat count, as in @code{next}.
3690 A signal is an asynchronous event that can happen in a program. The
3691 operating system defines the possible kinds of signals, and gives each
3692 kind a name and a number. For example, in Unix @code{SIGINT} is the
3693 signal a program gets when you type an interrupt character (often @kbd{C-c});
3694 @code{SIGSEGV} is the signal a program gets from referencing a place in
3695 memory far away from all the areas in use; @code{SIGALRM} occurs when
3696 the alarm clock timer goes off (which happens only if your program has
3697 requested an alarm).
3699 @cindex fatal signals
3700 Some signals, including @code{SIGALRM}, are a normal part of the
3701 functioning of your program. Others, such as @code{SIGSEGV}, indicate
3702 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
3703 program has not specified in advance some other way to handle the signal.
3704 @code{SIGINT} does not indicate an error in your program, but it is normally
3705 fatal so it can carry out the purpose of the interrupt: to kill the program.
3707 @value{GDBN} has the ability to detect any occurrence of a signal in your
3708 program. You can tell @value{GDBN} in advance what to do for each kind of
3711 @cindex handling signals
3712 Normally, @value{GDBN} is set up to let the non-erroneous signals like
3713 @code{SIGALRM} be silently passed to your program
3714 (so as not to interfere with their role in the program's functioning)
3715 but to stop your program immediately whenever an error signal happens.
3716 You can change these settings with the @code{handle} command.
3719 @kindex info signals
3722 Print a table of all the kinds of signals and how @value{GDBN} has been told to
3723 handle each one. You can use this to see the signal numbers of all
3724 the defined types of signals.
3726 @code{info handle} is an alias for @code{info signals}.
3729 @item handle @var{signal} @var{keywords}@dots{}
3730 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
3731 can be the number of a signal or its name (with or without the
3732 @samp{SIG} at the beginning); a list of signal numbers of the form
3733 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
3734 known signals. The @var{keywords} say what change to make.
3738 The keywords allowed by the @code{handle} command can be abbreviated.
3739 Their full names are:
3743 @value{GDBN} should not stop your program when this signal happens. It may
3744 still print a message telling you that the signal has come in.
3747 @value{GDBN} should stop your program when this signal happens. This implies
3748 the @code{print} keyword as well.
3751 @value{GDBN} should print a message when this signal happens.
3754 @value{GDBN} should not mention the occurrence of the signal at all. This
3755 implies the @code{nostop} keyword as well.
3759 @value{GDBN} should allow your program to see this signal; your program
3760 can handle the signal, or else it may terminate if the signal is fatal
3761 and not handled. @code{pass} and @code{noignore} are synonyms.
3765 @value{GDBN} should not allow your program to see this signal.
3766 @code{nopass} and @code{ignore} are synonyms.
3770 When a signal stops your program, the signal is not visible to the
3772 continue. Your program sees the signal then, if @code{pass} is in
3773 effect for the signal in question @emph{at that time}. In other words,
3774 after @value{GDBN} reports a signal, you can use the @code{handle}
3775 command with @code{pass} or @code{nopass} to control whether your
3776 program sees that signal when you continue.
3778 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
3779 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
3780 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
3783 You can also use the @code{signal} command to prevent your program from
3784 seeing a signal, or cause it to see a signal it normally would not see,
3785 or to give it any signal at any time. For example, if your program stopped
3786 due to some sort of memory reference error, you might store correct
3787 values into the erroneous variables and continue, hoping to see more
3788 execution; but your program would probably terminate immediately as
3789 a result of the fatal signal once it saw the signal. To prevent this,
3790 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
3794 @section Stopping and starting multi-thread programs
3796 When your program has multiple threads (@pxref{Threads,, Debugging
3797 programs with multiple threads}), you can choose whether to set
3798 breakpoints on all threads, or on a particular thread.
3801 @cindex breakpoints and threads
3802 @cindex thread breakpoints
3803 @kindex break @dots{} thread @var{threadno}
3804 @item break @var{linespec} thread @var{threadno}
3805 @itemx break @var{linespec} thread @var{threadno} if @dots{}
3806 @var{linespec} specifies source lines; there are several ways of
3807 writing them, but the effect is always to specify some source line.
3809 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
3810 to specify that you only want @value{GDBN} to stop the program when a
3811 particular thread reaches this breakpoint. @var{threadno} is one of the
3812 numeric thread identifiers assigned by @value{GDBN}, shown in the first
3813 column of the @samp{info threads} display.
3815 If you do not specify @samp{thread @var{threadno}} when you set a
3816 breakpoint, the breakpoint applies to @emph{all} threads of your
3819 You can use the @code{thread} qualifier on conditional breakpoints as
3820 well; in this case, place @samp{thread @var{threadno}} before the
3821 breakpoint condition, like this:
3824 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
3829 @cindex stopped threads
3830 @cindex threads, stopped
3831 Whenever your program stops under @value{GDBN} for any reason,
3832 @emph{all} threads of execution stop, not just the current thread. This
3833 allows you to examine the overall state of the program, including
3834 switching between threads, without worrying that things may change
3837 @cindex thread breakpoints and system calls
3838 @cindex system calls and thread breakpoints
3839 @cindex premature return from system calls
3840 There is an unfortunate side effect. If one thread stops for a
3841 breakpoint, or for some other reason, and another thread is blocked in a
3842 system call, then the system call may return prematurely. This is a
3843 consequence of the interaction between multiple threads and the signals
3844 that @value{GDBN} uses to implement breakpoints and other events that
3847 To handle this problem, your program should check the return value of
3848 each system call and react appropriately. This is good programming
3851 For example, do not write code like this:
3857 The call to @code{sleep} will return early if a different thread stops
3858 at a breakpoint or for some other reason.
3860 Instead, write this:
3865 unslept = sleep (unslept);
3868 A system call is allowed to return early, so the system is still
3869 conforming to its specification. But @value{GDBN} does cause your
3870 multi-threaded program to behave differently than it would without
3873 Also, @value{GDBN} uses internal breakpoints in the thread library to
3874 monitor certain events such as thread creation and thread destruction.
3875 When such an event happens, a system call in another thread may return
3876 prematurely, even though your program does not appear to stop.
3878 @cindex continuing threads
3879 @cindex threads, continuing
3880 Conversely, whenever you restart the program, @emph{all} threads start
3881 executing. @emph{This is true even when single-stepping} with commands
3882 like @code{step} or @code{next}.
3884 In particular, @value{GDBN} cannot single-step all threads in lockstep.
3885 Since thread scheduling is up to your debugging target's operating
3886 system (not controlled by @value{GDBN}), other threads may
3887 execute more than one statement while the current thread completes a
3888 single step. Moreover, in general other threads stop in the middle of a
3889 statement, rather than at a clean statement boundary, when the program
3892 You might even find your program stopped in another thread after
3893 continuing or even single-stepping. This happens whenever some other
3894 thread runs into a breakpoint, a signal, or an exception before the
3895 first thread completes whatever you requested.
3897 On some OSes, you can lock the OS scheduler and thus allow only a single
3901 @item set scheduler-locking @var{mode}
3902 Set the scheduler locking mode. If it is @code{off}, then there is no
3903 locking and any thread may run at any time. If @code{on}, then only the
3904 current thread may run when the inferior is resumed. The @code{step}
3905 mode optimizes for single-stepping. It stops other threads from
3906 ``seizing the prompt'' by preempting the current thread while you are
3907 stepping. Other threads will only rarely (or never) get a chance to run
3908 when you step. They are more likely to run when you @samp{next} over a
3909 function call, and they are completely free to run when you use commands
3910 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
3911 thread hits a breakpoint during its timeslice, they will never steal the
3912 @value{GDBN} prompt away from the thread that you are debugging.
3914 @item show scheduler-locking
3915 Display the current scheduler locking mode.
3920 @chapter Examining the Stack
3922 When your program has stopped, the first thing you need to know is where it
3923 stopped and how it got there.
3926 Each time your program performs a function call, information about the call
3928 That information includes the location of the call in your program,
3929 the arguments of the call,
3930 and the local variables of the function being called.
3931 The information is saved in a block of data called a @dfn{stack frame}.
3932 The stack frames are allocated in a region of memory called the @dfn{call
3935 When your program stops, the @value{GDBN} commands for examining the
3936 stack allow you to see all of this information.
3938 @cindex selected frame
3939 One of the stack frames is @dfn{selected} by @value{GDBN} and many
3940 @value{GDBN} commands refer implicitly to the selected frame. In
3941 particular, whenever you ask @value{GDBN} for the value of a variable in
3942 your program, the value is found in the selected frame. There are
3943 special @value{GDBN} commands to select whichever frame you are
3944 interested in. @xref{Selection, ,Selecting a frame}.
3946 When your program stops, @value{GDBN} automatically selects the
3947 currently executing frame and describes it briefly, similar to the
3948 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
3951 * Frames:: Stack frames
3952 * Backtrace:: Backtraces
3953 * Selection:: Selecting a frame
3954 * Frame Info:: Information on a frame
3959 @section Stack frames
3961 @cindex frame, definition
3963 The call stack is divided up into contiguous pieces called @dfn{stack
3964 frames}, or @dfn{frames} for short; each frame is the data associated
3965 with one call to one function. The frame contains the arguments given
3966 to the function, the function's local variables, and the address at
3967 which the function is executing.
3969 @cindex initial frame
3970 @cindex outermost frame
3971 @cindex innermost frame
3972 When your program is started, the stack has only one frame, that of the
3973 function @code{main}. This is called the @dfn{initial} frame or the
3974 @dfn{outermost} frame. Each time a function is called, a new frame is
3975 made. Each time a function returns, the frame for that function invocation
3976 is eliminated. If a function is recursive, there can be many frames for
3977 the same function. The frame for the function in which execution is
3978 actually occurring is called the @dfn{innermost} frame. This is the most
3979 recently created of all the stack frames that still exist.
3981 @cindex frame pointer
3982 Inside your program, stack frames are identified by their addresses. A
3983 stack frame consists of many bytes, each of which has its own address; each
3984 kind of computer has a convention for choosing one byte whose
3985 address serves as the address of the frame. Usually this address is kept
3986 in a register called the @dfn{frame pointer register} while execution is
3987 going on in that frame.
3989 @cindex frame number
3990 @value{GDBN} assigns numbers to all existing stack frames, starting with
3991 zero for the innermost frame, one for the frame that called it,
3992 and so on upward. These numbers do not really exist in your program;
3993 they are assigned by @value{GDBN} to give you a way of designating stack
3994 frames in @value{GDBN} commands.
3996 @c The -fomit-frame-pointer below perennially causes hbox overflow
3997 @c underflow problems.
3998 @cindex frameless execution
3999 Some compilers provide a way to compile functions so that they operate
4000 without stack frames. (For example, the @value{GCC} option
4002 @samp{-fomit-frame-pointer}
4004 generates functions without a frame.)
4005 This is occasionally done with heavily used library functions to save
4006 the frame setup time. @value{GDBN} has limited facilities for dealing
4007 with these function invocations. If the innermost function invocation
4008 has no stack frame, @value{GDBN} nevertheless regards it as though
4009 it had a separate frame, which is numbered zero as usual, allowing
4010 correct tracing of the function call chain. However, @value{GDBN} has
4011 no provision for frameless functions elsewhere in the stack.
4014 @kindex frame@r{, command}
4015 @cindex current stack frame
4016 @item frame @var{args}
4017 The @code{frame} command allows you to move from one stack frame to another,
4018 and to print the stack frame you select. @var{args} may be either the
4019 address of the frame or the stack frame number. Without an argument,
4020 @code{frame} prints the current stack frame.
4022 @kindex select-frame
4023 @cindex selecting frame silently
4025 The @code{select-frame} command allows you to move from one stack frame
4026 to another without printing the frame. This is the silent version of
4035 @cindex stack traces
4036 A backtrace is a summary of how your program got where it is. It shows one
4037 line per frame, for many frames, starting with the currently executing
4038 frame (frame zero), followed by its caller (frame one), and on up the
4043 @kindex bt @r{(@code{backtrace})}
4046 Print a backtrace of the entire stack: one line per frame for all
4047 frames in the stack.
4049 You can stop the backtrace at any time by typing the system interrupt
4050 character, normally @kbd{C-c}.
4052 @item backtrace @var{n}
4054 Similar, but print only the innermost @var{n} frames.
4056 @item backtrace -@var{n}
4058 Similar, but print only the outermost @var{n} frames.
4063 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4064 are additional aliases for @code{backtrace}.
4066 Each line in the backtrace shows the frame number and the function name.
4067 The program counter value is also shown---unless you use @code{set
4068 print address off}. The backtrace also shows the source file name and
4069 line number, as well as the arguments to the function. The program
4070 counter value is omitted if it is at the beginning of the code for that
4073 Here is an example of a backtrace. It was made with the command
4074 @samp{bt 3}, so it shows the innermost three frames.
4078 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4080 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4081 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4083 (More stack frames follow...)
4088 The display for frame zero does not begin with a program counter
4089 value, indicating that your program has stopped at the beginning of the
4090 code for line @code{993} of @code{builtin.c}.
4092 Most programs have a standard user entry point---a place where system
4093 libraries and startup code transition into user code. For C this is
4094 @code{main}. When @value{GDBN} finds the entry function in a backtrace
4095 it will terminate the backtrace, to avoid tracing into highly
4096 system-specific (and generally uninteresting) code.
4098 If you need to examine the startup code, or limit the number of levels
4099 in a backtrace, you can change this behavior:
4102 @item set backtrace past-main
4103 @itemx set backtrace past-main on
4104 @kindex set backtrace
4105 Backtraces will continue past the user entry point.
4107 @item set backtrace past-main off
4108 Backtraces will stop when they encounter the user entry point. This is the
4111 @item show backtrace past-main
4112 @kindex show backtrace
4113 Display the current user entry point backtrace policy.
4115 @item set backtrace limit @var{n}
4116 @itemx set backtrace limit 0
4117 @cindex backtrace limit
4118 Limit the backtrace to @var{n} levels. A value of zero means
4121 @item show backtrace limit
4122 Display the current limit on backtrace levels.
4126 @section Selecting a frame
4128 Most commands for examining the stack and other data in your program work on
4129 whichever stack frame is selected at the moment. Here are the commands for
4130 selecting a stack frame; all of them finish by printing a brief description
4131 of the stack frame just selected.
4134 @kindex frame@r{, selecting}
4135 @kindex f @r{(@code{frame})}
4138 Select frame number @var{n}. Recall that frame zero is the innermost
4139 (currently executing) frame, frame one is the frame that called the
4140 innermost one, and so on. The highest-numbered frame is the one for
4143 @item frame @var{addr}
4145 Select the frame at address @var{addr}. This is useful mainly if the
4146 chaining of stack frames has been damaged by a bug, making it
4147 impossible for @value{GDBN} to assign numbers properly to all frames. In
4148 addition, this can be useful when your program has multiple stacks and
4149 switches between them.
4151 On the SPARC architecture, @code{frame} needs two addresses to
4152 select an arbitrary frame: a frame pointer and a stack pointer.
4154 On the MIPS and Alpha architecture, it needs two addresses: a stack
4155 pointer and a program counter.
4157 On the 29k architecture, it needs three addresses: a register stack
4158 pointer, a program counter, and a memory stack pointer.
4159 @c note to future updaters: this is conditioned on a flag
4160 @c SETUP_ARBITRARY_FRAME in the tm-*.h files. The above is up to date
4161 @c as of 27 Jan 1994.
4165 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4166 advances toward the outermost frame, to higher frame numbers, to frames
4167 that have existed longer. @var{n} defaults to one.
4170 @kindex do @r{(@code{down})}
4172 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4173 advances toward the innermost frame, to lower frame numbers, to frames
4174 that were created more recently. @var{n} defaults to one. You may
4175 abbreviate @code{down} as @code{do}.
4178 All of these commands end by printing two lines of output describing the
4179 frame. The first line shows the frame number, the function name, the
4180 arguments, and the source file and line number of execution in that
4181 frame. The second line shows the text of that source line.
4189 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4191 10 read_input_file (argv[i]);
4195 After such a printout, the @code{list} command with no arguments
4196 prints ten lines centered on the point of execution in the frame.
4197 You can also edit the program at the point of execution with your favorite
4198 editing program by typing @code{edit}.
4199 @xref{List, ,Printing source lines},
4203 @kindex down-silently
4205 @item up-silently @var{n}
4206 @itemx down-silently @var{n}
4207 These two commands are variants of @code{up} and @code{down},
4208 respectively; they differ in that they do their work silently, without
4209 causing display of the new frame. They are intended primarily for use
4210 in @value{GDBN} command scripts, where the output might be unnecessary and
4215 @section Information about a frame
4217 There are several other commands to print information about the selected
4223 When used without any argument, this command does not change which
4224 frame is selected, but prints a brief description of the currently
4225 selected stack frame. It can be abbreviated @code{f}. With an
4226 argument, this command is used to select a stack frame.
4227 @xref{Selection, ,Selecting a frame}.
4230 @kindex info f @r{(@code{info frame})}
4233 This command prints a verbose description of the selected stack frame,
4238 the address of the frame
4240 the address of the next frame down (called by this frame)
4242 the address of the next frame up (caller of this frame)
4244 the language in which the source code corresponding to this frame is written
4246 the address of the frame's arguments
4248 the address of the frame's local variables
4250 the program counter saved in it (the address of execution in the caller frame)
4252 which registers were saved in the frame
4255 @noindent The verbose description is useful when
4256 something has gone wrong that has made the stack format fail to fit
4257 the usual conventions.
4259 @item info frame @var{addr}
4260 @itemx info f @var{addr}
4261 Print a verbose description of the frame at address @var{addr}, without
4262 selecting that frame. The selected frame remains unchanged by this
4263 command. This requires the same kind of address (more than one for some
4264 architectures) that you specify in the @code{frame} command.
4265 @xref{Selection, ,Selecting a frame}.
4269 Print the arguments of the selected frame, each on a separate line.
4273 Print the local variables of the selected frame, each on a separate
4274 line. These are all variables (declared either static or automatic)
4275 accessible at the point of execution of the selected frame.
4278 @cindex catch exceptions, list active handlers
4279 @cindex exception handlers, how to list
4281 Print a list of all the exception handlers that are active in the
4282 current stack frame at the current point of execution. To see other
4283 exception handlers, visit the associated frame (using the @code{up},
4284 @code{down}, or @code{frame} commands); then type @code{info catch}.
4285 @xref{Set Catchpoints, , Setting catchpoints}.
4291 @chapter Examining Source Files
4293 @value{GDBN} can print parts of your program's source, since the debugging
4294 information recorded in the program tells @value{GDBN} what source files were
4295 used to build it. When your program stops, @value{GDBN} spontaneously prints
4296 the line where it stopped. Likewise, when you select a stack frame
4297 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4298 execution in that frame has stopped. You can print other portions of
4299 source files by explicit command.
4301 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4302 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4303 @value{GDBN} under @sc{gnu} Emacs}.
4306 * List:: Printing source lines
4307 * Edit:: Editing source files
4308 * Search:: Searching source files
4309 * Source Path:: Specifying source directories
4310 * Machine Code:: Source and machine code
4314 @section Printing source lines
4317 @kindex l @r{(@code{list})}
4318 To print lines from a source file, use the @code{list} command
4319 (abbreviated @code{l}). By default, ten lines are printed.
4320 There are several ways to specify what part of the file you want to print.
4322 Here are the forms of the @code{list} command most commonly used:
4325 @item list @var{linenum}
4326 Print lines centered around line number @var{linenum} in the
4327 current source file.
4329 @item list @var{function}
4330 Print lines centered around the beginning of function
4334 Print more lines. If the last lines printed were printed with a
4335 @code{list} command, this prints lines following the last lines
4336 printed; however, if the last line printed was a solitary line printed
4337 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4338 Stack}), this prints lines centered around that line.
4341 Print lines just before the lines last printed.
4344 By default, @value{GDBN} prints ten source lines with any of these forms of
4345 the @code{list} command. You can change this using @code{set listsize}:
4348 @kindex set listsize
4349 @item set listsize @var{count}
4350 Make the @code{list} command display @var{count} source lines (unless
4351 the @code{list} argument explicitly specifies some other number).
4353 @kindex show listsize
4355 Display the number of lines that @code{list} prints.
4358 Repeating a @code{list} command with @key{RET} discards the argument,
4359 so it is equivalent to typing just @code{list}. This is more useful
4360 than listing the same lines again. An exception is made for an
4361 argument of @samp{-}; that argument is preserved in repetition so that
4362 each repetition moves up in the source file.
4365 In general, the @code{list} command expects you to supply zero, one or two
4366 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4367 of writing them, but the effect is always to specify some source line.
4368 Here is a complete description of the possible arguments for @code{list}:
4371 @item list @var{linespec}
4372 Print lines centered around the line specified by @var{linespec}.
4374 @item list @var{first},@var{last}
4375 Print lines from @var{first} to @var{last}. Both arguments are
4378 @item list ,@var{last}
4379 Print lines ending with @var{last}.
4381 @item list @var{first},
4382 Print lines starting with @var{first}.
4385 Print lines just after the lines last printed.
4388 Print lines just before the lines last printed.
4391 As described in the preceding table.
4394 Here are the ways of specifying a single source line---all the
4399 Specifies line @var{number} of the current source file.
4400 When a @code{list} command has two linespecs, this refers to
4401 the same source file as the first linespec.
4404 Specifies the line @var{offset} lines after the last line printed.
4405 When used as the second linespec in a @code{list} command that has
4406 two, this specifies the line @var{offset} lines down from the
4410 Specifies the line @var{offset} lines before the last line printed.
4412 @item @var{filename}:@var{number}
4413 Specifies line @var{number} in the source file @var{filename}.
4415 @item @var{function}
4416 Specifies the line that begins the body of the function @var{function}.
4417 For example: in C, this is the line with the open brace.
4419 @item @var{filename}:@var{function}
4420 Specifies the line of the open-brace that begins the body of the
4421 function @var{function} in the file @var{filename}. You only need the
4422 file name with a function name to avoid ambiguity when there are
4423 identically named functions in different source files.
4425 @item *@var{address}
4426 Specifies the line containing the program address @var{address}.
4427 @var{address} may be any expression.
4431 @section Editing source files
4432 @cindex editing source files
4435 @kindex e @r{(@code{edit})}
4436 To edit the lines in a source file, use the @code{edit} command.
4437 The editing program of your choice
4438 is invoked with the current line set to
4439 the active line in the program.
4440 Alternatively, there are several ways to specify what part of the file you
4441 want to print if you want to see other parts of the program.
4443 Here are the forms of the @code{edit} command most commonly used:
4447 Edit the current source file at the active line number in the program.
4449 @item edit @var{number}
4450 Edit the current source file with @var{number} as the active line number.
4452 @item edit @var{function}
4453 Edit the file containing @var{function} at the beginning of its definition.
4455 @item edit @var{filename}:@var{number}
4456 Specifies line @var{number} in the source file @var{filename}.
4458 @item edit @var{filename}:@var{function}
4459 Specifies the line that begins the body of the
4460 function @var{function} in the file @var{filename}. You only need the
4461 file name with a function name to avoid ambiguity when there are
4462 identically named functions in different source files.
4464 @item edit *@var{address}
4465 Specifies the line containing the program address @var{address}.
4466 @var{address} may be any expression.
4469 @subsection Choosing your editor
4470 You can customize @value{GDBN} to use any editor you want
4472 The only restriction is that your editor (say @code{ex}), recognizes the
4473 following command-line syntax:
4475 ex +@var{number} file
4477 The optional numeric value +@var{number} specifies the number of the line in
4478 the file where to start editing.}.
4479 By default, it is @file{@value{EDITOR}}, but you can change this
4480 by setting the environment variable @code{EDITOR} before using
4481 @value{GDBN}. For example, to configure @value{GDBN} to use the
4482 @code{vi} editor, you could use these commands with the @code{sh} shell:
4488 or in the @code{csh} shell,
4490 setenv EDITOR /usr/bin/vi
4495 @section Searching source files
4496 @cindex searching source files
4497 @kindex reverse-search
4499 There are two commands for searching through the current source file for a
4504 @kindex forward-search
4505 @item forward-search @var{regexp}
4506 @itemx search @var{regexp}
4507 The command @samp{forward-search @var{regexp}} checks each line,
4508 starting with the one following the last line listed, for a match for
4509 @var{regexp}. It lists the line that is found. You can use the
4510 synonym @samp{search @var{regexp}} or abbreviate the command name as
4513 @item reverse-search @var{regexp}
4514 The command @samp{reverse-search @var{regexp}} checks each line, starting
4515 with the one before the last line listed and going backward, for a match
4516 for @var{regexp}. It lists the line that is found. You can abbreviate
4517 this command as @code{rev}.
4521 @section Specifying source directories
4524 @cindex directories for source files
4525 Executable programs sometimes do not record the directories of the source
4526 files from which they were compiled, just the names. Even when they do,
4527 the directories could be moved between the compilation and your debugging
4528 session. @value{GDBN} has a list of directories to search for source files;
4529 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
4530 it tries all the directories in the list, in the order they are present
4531 in the list, until it finds a file with the desired name.
4533 For example, suppose an executable references the file
4534 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
4535 @file{/mnt/cross}. The file is first looked up literally; if this
4536 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
4537 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
4538 message is printed. @value{GDBN} does not look up the parts of the
4539 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
4540 Likewise, the subdirectories of the source path are not searched: if
4541 the source path is @file{/mnt/cross}, and the binary refers to
4542 @file{foo.c}, @value{GDBN} would not find it under
4543 @file{/mnt/cross/usr/src/foo-1.0/lib}.
4545 Plain file names, relative file names with leading directories, file
4546 names containing dots, etc.@: are all treated as described above; for
4547 instance, if the source path is @file{/mnt/cross}, and the source file
4548 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
4549 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
4550 that---@file{/mnt/cross/foo.c}.
4552 Note that the executable search path is @emph{not} used to locate the
4553 source files. Neither is the current working directory, unless it
4554 happens to be in the source path.
4556 Whenever you reset or rearrange the source path, @value{GDBN} clears out
4557 any information it has cached about where source files are found and where
4558 each line is in the file.
4562 When you start @value{GDBN}, its source path includes only @samp{cdir}
4563 and @samp{cwd}, in that order.
4564 To add other directories, use the @code{directory} command.
4567 @item directory @var{dirname} @dots{}
4568 @item dir @var{dirname} @dots{}
4569 Add directory @var{dirname} to the front of the source path. Several
4570 directory names may be given to this command, separated by @samp{:}
4571 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
4572 part of absolute file names) or
4573 whitespace. You may specify a directory that is already in the source
4574 path; this moves it forward, so @value{GDBN} searches it sooner.
4578 @vindex $cdir@r{, convenience variable}
4579 @vindex $cwdr@r{, convenience variable}
4580 @cindex compilation directory
4581 @cindex current directory
4582 @cindex working directory
4583 @cindex directory, current
4584 @cindex directory, compilation
4585 You can use the string @samp{$cdir} to refer to the compilation
4586 directory (if one is recorded), and @samp{$cwd} to refer to the current
4587 working directory. @samp{$cwd} is not the same as @samp{.}---the former
4588 tracks the current working directory as it changes during your @value{GDBN}
4589 session, while the latter is immediately expanded to the current
4590 directory at the time you add an entry to the source path.
4593 Reset the source path to empty again. This requires confirmation.
4595 @c RET-repeat for @code{directory} is explicitly disabled, but since
4596 @c repeating it would be a no-op we do not say that. (thanks to RMS)
4598 @item show directories
4599 @kindex show directories
4600 Print the source path: show which directories it contains.
4603 If your source path is cluttered with directories that are no longer of
4604 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
4605 versions of source. You can correct the situation as follows:
4609 Use @code{directory} with no argument to reset the source path to empty.
4612 Use @code{directory} with suitable arguments to reinstall the
4613 directories you want in the source path. You can add all the
4614 directories in one command.
4618 @section Source and machine code
4619 @cindex source line and its code address
4621 You can use the command @code{info line} to map source lines to program
4622 addresses (and vice versa), and the command @code{disassemble} to display
4623 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
4624 mode, the @code{info line} command causes the arrow to point to the
4625 line specified. Also, @code{info line} prints addresses in symbolic form as
4630 @item info line @var{linespec}
4631 Print the starting and ending addresses of the compiled code for
4632 source line @var{linespec}. You can specify source lines in any of
4633 the ways understood by the @code{list} command (@pxref{List, ,Printing
4637 For example, we can use @code{info line} to discover the location of
4638 the object code for the first line of function
4639 @code{m4_changequote}:
4641 @c FIXME: I think this example should also show the addresses in
4642 @c symbolic form, as they usually would be displayed.
4644 (@value{GDBP}) info line m4_changequote
4645 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
4649 @cindex code address and its source line
4650 We can also inquire (using @code{*@var{addr}} as the form for
4651 @var{linespec}) what source line covers a particular address:
4653 (@value{GDBP}) info line *0x63ff
4654 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
4657 @cindex @code{$_} and @code{info line}
4658 @cindex @code{x} command, default address
4659 @kindex x@r{(examine), and} info line
4660 After @code{info line}, the default address for the @code{x} command
4661 is changed to the starting address of the line, so that @samp{x/i} is
4662 sufficient to begin examining the machine code (@pxref{Memory,
4663 ,Examining memory}). Also, this address is saved as the value of the
4664 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
4669 @cindex assembly instructions
4670 @cindex instructions, assembly
4671 @cindex machine instructions
4672 @cindex listing machine instructions
4674 This specialized command dumps a range of memory as machine
4675 instructions. The default memory range is the function surrounding the
4676 program counter of the selected frame. A single argument to this
4677 command is a program counter value; @value{GDBN} dumps the function
4678 surrounding this value. Two arguments specify a range of addresses
4679 (first inclusive, second exclusive) to dump.
4682 The following example shows the disassembly of a range of addresses of
4683 HP PA-RISC 2.0 code:
4686 (@value{GDBP}) disas 0x32c4 0x32e4
4687 Dump of assembler code from 0x32c4 to 0x32e4:
4688 0x32c4 <main+204>: addil 0,dp
4689 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
4690 0x32cc <main+212>: ldil 0x3000,r31
4691 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
4692 0x32d4 <main+220>: ldo 0(r31),rp
4693 0x32d8 <main+224>: addil -0x800,dp
4694 0x32dc <main+228>: ldo 0x588(r1),r26
4695 0x32e0 <main+232>: ldil 0x3000,r31
4696 End of assembler dump.
4699 Some architectures have more than one commonly-used set of instruction
4700 mnemonics or other syntax.
4703 @kindex set disassembly-flavor
4704 @cindex Intel disassembly flavor
4705 @cindex AT&T disassembly flavor
4706 @item set disassembly-flavor @var{instruction-set}
4707 Select the instruction set to use when disassembling the
4708 program via the @code{disassemble} or @code{x/i} commands.
4710 Currently this command is only defined for the Intel x86 family. You
4711 can set @var{instruction-set} to either @code{intel} or @code{att}.
4712 The default is @code{att}, the AT&T flavor used by default by Unix
4713 assemblers for x86-based targets.
4718 @chapter Examining Data
4720 @cindex printing data
4721 @cindex examining data
4724 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
4725 @c document because it is nonstandard... Under Epoch it displays in a
4726 @c different window or something like that.
4727 The usual way to examine data in your program is with the @code{print}
4728 command (abbreviated @code{p}), or its synonym @code{inspect}. It
4729 evaluates and prints the value of an expression of the language your
4730 program is written in (@pxref{Languages, ,Using @value{GDBN} with
4731 Different Languages}).
4734 @item print @var{expr}
4735 @itemx print /@var{f} @var{expr}
4736 @var{expr} is an expression (in the source language). By default the
4737 value of @var{expr} is printed in a format appropriate to its data type;
4738 you can choose a different format by specifying @samp{/@var{f}}, where
4739 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
4743 @itemx print /@var{f}
4744 @cindex reprint the last value
4745 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
4746 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
4747 conveniently inspect the same value in an alternative format.
4750 A more low-level way of examining data is with the @code{x} command.
4751 It examines data in memory at a specified address and prints it in a
4752 specified format. @xref{Memory, ,Examining memory}.
4754 If you are interested in information about types, or about how the
4755 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
4756 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
4760 * Expressions:: Expressions
4761 * Variables:: Program variables
4762 * Arrays:: Artificial arrays
4763 * Output Formats:: Output formats
4764 * Memory:: Examining memory
4765 * Auto Display:: Automatic display
4766 * Print Settings:: Print settings
4767 * Value History:: Value history
4768 * Convenience Vars:: Convenience variables
4769 * Registers:: Registers
4770 * Floating Point Hardware:: Floating point hardware
4771 * Vector Unit:: Vector Unit
4772 * Auxiliary Vector:: Auxiliary data provided by operating system
4773 * Memory Region Attributes:: Memory region attributes
4774 * Dump/Restore Files:: Copy between memory and a file
4775 * Character Sets:: Debugging programs that use a different
4776 character set than GDB does
4780 @section Expressions
4783 @code{print} and many other @value{GDBN} commands accept an expression and
4784 compute its value. Any kind of constant, variable or operator defined
4785 by the programming language you are using is valid in an expression in
4786 @value{GDBN}. This includes conditional expressions, function calls,
4787 casts, and string constants. It also includes preprocessor macros, if
4788 you compiled your program to include this information; see
4791 @cindex arrays in expressions
4792 @value{GDBN} supports array constants in expressions input by
4793 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
4794 you can use the command @code{print @{1, 2, 3@}} to build up an array in
4795 memory that is @code{malloc}ed in the target program.
4797 Because C is so widespread, most of the expressions shown in examples in
4798 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
4799 Languages}, for information on how to use expressions in other
4802 In this section, we discuss operators that you can use in @value{GDBN}
4803 expressions regardless of your programming language.
4805 @cindex casts, in expressions
4806 Casts are supported in all languages, not just in C, because it is so
4807 useful to cast a number into a pointer in order to examine a structure
4808 at that address in memory.
4809 @c FIXME: casts supported---Mod2 true?
4811 @value{GDBN} supports these operators, in addition to those common
4812 to programming languages:
4816 @samp{@@} is a binary operator for treating parts of memory as arrays.
4817 @xref{Arrays, ,Artificial arrays}, for more information.
4820 @samp{::} allows you to specify a variable in terms of the file or
4821 function where it is defined. @xref{Variables, ,Program variables}.
4823 @cindex @{@var{type}@}
4824 @cindex type casting memory
4825 @cindex memory, viewing as typed object
4826 @cindex casts, to view memory
4827 @item @{@var{type}@} @var{addr}
4828 Refers to an object of type @var{type} stored at address @var{addr} in
4829 memory. @var{addr} may be any expression whose value is an integer or
4830 pointer (but parentheses are required around binary operators, just as in
4831 a cast). This construct is allowed regardless of what kind of data is
4832 normally supposed to reside at @var{addr}.
4836 @section Program variables
4838 The most common kind of expression to use is the name of a variable
4841 Variables in expressions are understood in the selected stack frame
4842 (@pxref{Selection, ,Selecting a frame}); they must be either:
4846 global (or file-static)
4853 visible according to the scope rules of the
4854 programming language from the point of execution in that frame
4857 @noindent This means that in the function
4872 you can examine and use the variable @code{a} whenever your program is
4873 executing within the function @code{foo}, but you can only use or
4874 examine the variable @code{b} while your program is executing inside
4875 the block where @code{b} is declared.
4877 @cindex variable name conflict
4878 There is an exception: you can refer to a variable or function whose
4879 scope is a single source file even if the current execution point is not
4880 in this file. But it is possible to have more than one such variable or
4881 function with the same name (in different source files). If that
4882 happens, referring to that name has unpredictable effects. If you wish,
4883 you can specify a static variable in a particular function or file,
4884 using the colon-colon (@code{::}) notation:
4886 @cindex colon-colon, context for variables/functions
4888 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
4889 @cindex @code{::}, context for variables/functions
4892 @var{file}::@var{variable}
4893 @var{function}::@var{variable}
4897 Here @var{file} or @var{function} is the name of the context for the
4898 static @var{variable}. In the case of file names, you can use quotes to
4899 make sure @value{GDBN} parses the file name as a single word---for example,
4900 to print a global value of @code{x} defined in @file{f2.c}:
4903 (@value{GDBP}) p 'f2.c'::x
4906 @cindex C@t{++} scope resolution
4907 This use of @samp{::} is very rarely in conflict with the very similar
4908 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
4909 scope resolution operator in @value{GDBN} expressions.
4910 @c FIXME: Um, so what happens in one of those rare cases where it's in
4913 @cindex wrong values
4914 @cindex variable values, wrong
4915 @cindex function entry/exit, wrong values of variables
4916 @cindex optimized code, wrong values of variables
4918 @emph{Warning:} Occasionally, a local variable may appear to have the
4919 wrong value at certain points in a function---just after entry to a new
4920 scope, and just before exit.
4922 You may see this problem when you are stepping by machine instructions.
4923 This is because, on most machines, it takes more than one instruction to
4924 set up a stack frame (including local variable definitions); if you are
4925 stepping by machine instructions, variables may appear to have the wrong
4926 values until the stack frame is completely built. On exit, it usually
4927 also takes more than one machine instruction to destroy a stack frame;
4928 after you begin stepping through that group of instructions, local
4929 variable definitions may be gone.
4931 This may also happen when the compiler does significant optimizations.
4932 To be sure of always seeing accurate values, turn off all optimization
4935 @cindex ``No symbol "foo" in current context''
4936 Another possible effect of compiler optimizations is to optimize
4937 unused variables out of existence, or assign variables to registers (as
4938 opposed to memory addresses). Depending on the support for such cases
4939 offered by the debug info format used by the compiler, @value{GDBN}
4940 might not be able to display values for such local variables. If that
4941 happens, @value{GDBN} will print a message like this:
4944 No symbol "foo" in current context.
4947 To solve such problems, either recompile without optimizations, or use a
4948 different debug info format, if the compiler supports several such
4949 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
4950 usually supports the @option{-gstabs+} option. @option{-gstabs+}
4951 produces debug info in a format that is superior to formats such as
4952 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
4953 an effective form for debug info. @xref{Debugging Options,,Options
4954 for Debugging Your Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}.
4955 @xref{C, , Debugging C++}, for more info about debug info formats
4956 that are best suited to C@t{++} programs.
4959 @section Artificial arrays
4961 @cindex artificial array
4963 @kindex @@@r{, referencing memory as an array}
4964 It is often useful to print out several successive objects of the
4965 same type in memory; a section of an array, or an array of
4966 dynamically determined size for which only a pointer exists in the
4969 You can do this by referring to a contiguous span of memory as an
4970 @dfn{artificial array}, using the binary operator @samp{@@}. The left
4971 operand of @samp{@@} should be the first element of the desired array
4972 and be an individual object. The right operand should be the desired length
4973 of the array. The result is an array value whose elements are all of
4974 the type of the left argument. The first element is actually the left
4975 argument; the second element comes from bytes of memory immediately
4976 following those that hold the first element, and so on. Here is an
4977 example. If a program says
4980 int *array = (int *) malloc (len * sizeof (int));
4984 you can print the contents of @code{array} with
4990 The left operand of @samp{@@} must reside in memory. Array values made
4991 with @samp{@@} in this way behave just like other arrays in terms of
4992 subscripting, and are coerced to pointers when used in expressions.
4993 Artificial arrays most often appear in expressions via the value history
4994 (@pxref{Value History, ,Value history}), after printing one out.
4996 Another way to create an artificial array is to use a cast.
4997 This re-interprets a value as if it were an array.
4998 The value need not be in memory:
5000 (@value{GDBP}) p/x (short[2])0x12345678
5001 $1 = @{0x1234, 0x5678@}
5004 As a convenience, if you leave the array length out (as in
5005 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5006 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5008 (@value{GDBP}) p/x (short[])0x12345678
5009 $2 = @{0x1234, 0x5678@}
5012 Sometimes the artificial array mechanism is not quite enough; in
5013 moderately complex data structures, the elements of interest may not
5014 actually be adjacent---for example, if you are interested in the values
5015 of pointers in an array. One useful work-around in this situation is
5016 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5017 variables}) as a counter in an expression that prints the first
5018 interesting value, and then repeat that expression via @key{RET}. For
5019 instance, suppose you have an array @code{dtab} of pointers to
5020 structures, and you are interested in the values of a field @code{fv}
5021 in each structure. Here is an example of what you might type:
5031 @node Output Formats
5032 @section Output formats
5034 @cindex formatted output
5035 @cindex output formats
5036 By default, @value{GDBN} prints a value according to its data type. Sometimes
5037 this is not what you want. For example, you might want to print a number
5038 in hex, or a pointer in decimal. Or you might want to view data in memory
5039 at a certain address as a character string or as an instruction. To do
5040 these things, specify an @dfn{output format} when you print a value.
5042 The simplest use of output formats is to say how to print a value
5043 already computed. This is done by starting the arguments of the
5044 @code{print} command with a slash and a format letter. The format
5045 letters supported are:
5049 Regard the bits of the value as an integer, and print the integer in
5053 Print as integer in signed decimal.
5056 Print as integer in unsigned decimal.
5059 Print as integer in octal.
5062 Print as integer in binary. The letter @samp{t} stands for ``two''.
5063 @footnote{@samp{b} cannot be used because these format letters are also
5064 used with the @code{x} command, where @samp{b} stands for ``byte'';
5065 see @ref{Memory,,Examining memory}.}
5068 @cindex unknown address, locating
5069 @cindex locate address
5070 Print as an address, both absolute in hexadecimal and as an offset from
5071 the nearest preceding symbol. You can use this format used to discover
5072 where (in what function) an unknown address is located:
5075 (@value{GDBP}) p/a 0x54320
5076 $3 = 0x54320 <_initialize_vx+396>
5080 The command @code{info symbol 0x54320} yields similar results.
5081 @xref{Symbols, info symbol}.
5084 Regard as an integer and print it as a character constant.
5087 Regard the bits of the value as a floating point number and print
5088 using typical floating point syntax.
5091 For example, to print the program counter in hex (@pxref{Registers}), type
5098 Note that no space is required before the slash; this is because command
5099 names in @value{GDBN} cannot contain a slash.
5101 To reprint the last value in the value history with a different format,
5102 you can use the @code{print} command with just a format and no
5103 expression. For example, @samp{p/x} reprints the last value in hex.
5106 @section Examining memory
5108 You can use the command @code{x} (for ``examine'') to examine memory in
5109 any of several formats, independently of your program's data types.
5111 @cindex examining memory
5113 @kindex x @r{(examine memory)}
5114 @item x/@var{nfu} @var{addr}
5117 Use the @code{x} command to examine memory.
5120 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5121 much memory to display and how to format it; @var{addr} is an
5122 expression giving the address where you want to start displaying memory.
5123 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5124 Several commands set convenient defaults for @var{addr}.
5127 @item @var{n}, the repeat count
5128 The repeat count is a decimal integer; the default is 1. It specifies
5129 how much memory (counting by units @var{u}) to display.
5130 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5133 @item @var{f}, the display format
5134 The display format is one of the formats used by @code{print},
5135 @samp{s} (null-terminated string), or @samp{i} (machine instruction).
5136 The default is @samp{x} (hexadecimal) initially.
5137 The default changes each time you use either @code{x} or @code{print}.
5139 @item @var{u}, the unit size
5140 The unit size is any of
5146 Halfwords (two bytes).
5148 Words (four bytes). This is the initial default.
5150 Giant words (eight bytes).
5153 Each time you specify a unit size with @code{x}, that size becomes the
5154 default unit the next time you use @code{x}. (For the @samp{s} and
5155 @samp{i} formats, the unit size is ignored and is normally not written.)
5157 @item @var{addr}, starting display address
5158 @var{addr} is the address where you want @value{GDBN} to begin displaying
5159 memory. The expression need not have a pointer value (though it may);
5160 it is always interpreted as an integer address of a byte of memory.
5161 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5162 @var{addr} is usually just after the last address examined---but several
5163 other commands also set the default address: @code{info breakpoints} (to
5164 the address of the last breakpoint listed), @code{info line} (to the
5165 starting address of a line), and @code{print} (if you use it to display
5166 a value from memory).
5169 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5170 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5171 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5172 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5173 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5175 Since the letters indicating unit sizes are all distinct from the
5176 letters specifying output formats, you do not have to remember whether
5177 unit size or format comes first; either order works. The output
5178 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5179 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5181 Even though the unit size @var{u} is ignored for the formats @samp{s}
5182 and @samp{i}, you might still want to use a count @var{n}; for example,
5183 @samp{3i} specifies that you want to see three machine instructions,
5184 including any operands. The command @code{disassemble} gives an
5185 alternative way of inspecting machine instructions; see @ref{Machine
5186 Code,,Source and machine code}.
5188 All the defaults for the arguments to @code{x} are designed to make it
5189 easy to continue scanning memory with minimal specifications each time
5190 you use @code{x}. For example, after you have inspected three machine
5191 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5192 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5193 the repeat count @var{n} is used again; the other arguments default as
5194 for successive uses of @code{x}.
5196 @cindex @code{$_}, @code{$__}, and value history
5197 The addresses and contents printed by the @code{x} command are not saved
5198 in the value history because there is often too much of them and they
5199 would get in the way. Instead, @value{GDBN} makes these values available for
5200 subsequent use in expressions as values of the convenience variables
5201 @code{$_} and @code{$__}. After an @code{x} command, the last address
5202 examined is available for use in expressions in the convenience variable
5203 @code{$_}. The contents of that address, as examined, are available in
5204 the convenience variable @code{$__}.
5206 If the @code{x} command has a repeat count, the address and contents saved
5207 are from the last memory unit printed; this is not the same as the last
5208 address printed if several units were printed on the last line of output.
5211 @section Automatic display
5212 @cindex automatic display
5213 @cindex display of expressions
5215 If you find that you want to print the value of an expression frequently
5216 (to see how it changes), you might want to add it to the @dfn{automatic
5217 display list} so that @value{GDBN} prints its value each time your program stops.
5218 Each expression added to the list is given a number to identify it;
5219 to remove an expression from the list, you specify that number.
5220 The automatic display looks like this:
5224 3: bar[5] = (struct hack *) 0x3804
5228 This display shows item numbers, expressions and their current values. As with
5229 displays you request manually using @code{x} or @code{print}, you can
5230 specify the output format you prefer; in fact, @code{display} decides
5231 whether to use @code{print} or @code{x} depending on how elaborate your
5232 format specification is---it uses @code{x} if you specify a unit size,
5233 or one of the two formats (@samp{i} and @samp{s}) that are only
5234 supported by @code{x}; otherwise it uses @code{print}.
5238 @item display @var{expr}
5239 Add the expression @var{expr} to the list of expressions to display
5240 each time your program stops. @xref{Expressions, ,Expressions}.
5242 @code{display} does not repeat if you press @key{RET} again after using it.
5244 @item display/@var{fmt} @var{expr}
5245 For @var{fmt} specifying only a display format and not a size or
5246 count, add the expression @var{expr} to the auto-display list but
5247 arrange to display it each time in the specified format @var{fmt}.
5248 @xref{Output Formats,,Output formats}.
5250 @item display/@var{fmt} @var{addr}
5251 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5252 number of units, add the expression @var{addr} as a memory address to
5253 be examined each time your program stops. Examining means in effect
5254 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5257 For example, @samp{display/i $pc} can be helpful, to see the machine
5258 instruction about to be executed each time execution stops (@samp{$pc}
5259 is a common name for the program counter; @pxref{Registers, ,Registers}).
5262 @kindex delete display
5264 @item undisplay @var{dnums}@dots{}
5265 @itemx delete display @var{dnums}@dots{}
5266 Remove item numbers @var{dnums} from the list of expressions to display.
5268 @code{undisplay} does not repeat if you press @key{RET} after using it.
5269 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5271 @kindex disable display
5272 @item disable display @var{dnums}@dots{}
5273 Disable the display of item numbers @var{dnums}. A disabled display
5274 item is not printed automatically, but is not forgotten. It may be
5275 enabled again later.
5277 @kindex enable display
5278 @item enable display @var{dnums}@dots{}
5279 Enable display of item numbers @var{dnums}. It becomes effective once
5280 again in auto display of its expression, until you specify otherwise.
5283 Display the current values of the expressions on the list, just as is
5284 done when your program stops.
5286 @kindex info display
5288 Print the list of expressions previously set up to display
5289 automatically, each one with its item number, but without showing the
5290 values. This includes disabled expressions, which are marked as such.
5291 It also includes expressions which would not be displayed right now
5292 because they refer to automatic variables not currently available.
5295 @cindex display disabled out of scope
5296 If a display expression refers to local variables, then it does not make
5297 sense outside the lexical context for which it was set up. Such an
5298 expression is disabled when execution enters a context where one of its
5299 variables is not defined. For example, if you give the command
5300 @code{display last_char} while inside a function with an argument
5301 @code{last_char}, @value{GDBN} displays this argument while your program
5302 continues to stop inside that function. When it stops elsewhere---where
5303 there is no variable @code{last_char}---the display is disabled
5304 automatically. The next time your program stops where @code{last_char}
5305 is meaningful, you can enable the display expression once again.
5307 @node Print Settings
5308 @section Print settings
5310 @cindex format options
5311 @cindex print settings
5312 @value{GDBN} provides the following ways to control how arrays, structures,
5313 and symbols are printed.
5316 These settings are useful for debugging programs in any language:
5320 @item set print address
5321 @itemx set print address on
5322 @cindex print/don't print memory addresses
5323 @value{GDBN} prints memory addresses showing the location of stack
5324 traces, structure values, pointer values, breakpoints, and so forth,
5325 even when it also displays the contents of those addresses. The default
5326 is @code{on}. For example, this is what a stack frame display looks like with
5327 @code{set print address on}:
5332 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
5334 530 if (lquote != def_lquote)
5338 @item set print address off
5339 Do not print addresses when displaying their contents. For example,
5340 this is the same stack frame displayed with @code{set print address off}:
5344 (@value{GDBP}) set print addr off
5346 #0 set_quotes (lq="<<", rq=">>") at input.c:530
5347 530 if (lquote != def_lquote)
5351 You can use @samp{set print address off} to eliminate all machine
5352 dependent displays from the @value{GDBN} interface. For example, with
5353 @code{print address off}, you should get the same text for backtraces on
5354 all machines---whether or not they involve pointer arguments.
5357 @item show print address
5358 Show whether or not addresses are to be printed.
5361 When @value{GDBN} prints a symbolic address, it normally prints the
5362 closest earlier symbol plus an offset. If that symbol does not uniquely
5363 identify the address (for example, it is a name whose scope is a single
5364 source file), you may need to clarify. One way to do this is with
5365 @code{info line}, for example @samp{info line *0x4537}. Alternately,
5366 you can set @value{GDBN} to print the source file and line number when
5367 it prints a symbolic address:
5370 @item set print symbol-filename on
5371 @cindex closest symbol and offset for an address
5372 Tell @value{GDBN} to print the source file name and line number of a
5373 symbol in the symbolic form of an address.
5375 @item set print symbol-filename off
5376 Do not print source file name and line number of a symbol. This is the
5379 @item show print symbol-filename
5380 Show whether or not @value{GDBN} will print the source file name and
5381 line number of a symbol in the symbolic form of an address.
5384 Another situation where it is helpful to show symbol filenames and line
5385 numbers is when disassembling code; @value{GDBN} shows you the line
5386 number and source file that corresponds to each instruction.
5388 Also, you may wish to see the symbolic form only if the address being
5389 printed is reasonably close to the closest earlier symbol:
5392 @item set print max-symbolic-offset @var{max-offset}
5393 @cindex maximum value for offset of closest symbol
5394 Tell @value{GDBN} to only display the symbolic form of an address if the
5395 offset between the closest earlier symbol and the address is less than
5396 @var{max-offset}. The default is 0, which tells @value{GDBN}
5397 to always print the symbolic form of an address if any symbol precedes it.
5399 @item show print max-symbolic-offset
5400 Ask how large the maximum offset is that @value{GDBN} prints in a
5404 @cindex wild pointer, interpreting
5405 @cindex pointer, finding referent
5406 If you have a pointer and you are not sure where it points, try
5407 @samp{set print symbol-filename on}. Then you can determine the name
5408 and source file location of the variable where it points, using
5409 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
5410 For example, here @value{GDBN} shows that a variable @code{ptt} points
5411 at another variable @code{t}, defined in @file{hi2.c}:
5414 (@value{GDBP}) set print symbol-filename on
5415 (@value{GDBP}) p/a ptt
5416 $4 = 0xe008 <t in hi2.c>
5420 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
5421 does not show the symbol name and filename of the referent, even with
5422 the appropriate @code{set print} options turned on.
5425 Other settings control how different kinds of objects are printed:
5428 @item set print array
5429 @itemx set print array on
5430 @cindex pretty print arrays
5431 Pretty print arrays. This format is more convenient to read,
5432 but uses more space. The default is off.
5434 @item set print array off
5435 Return to compressed format for arrays.
5437 @item show print array
5438 Show whether compressed or pretty format is selected for displaying
5441 @item set print elements @var{number-of-elements}
5442 @cindex number of array elements to print
5443 Set a limit on how many elements of an array @value{GDBN} will print.
5444 If @value{GDBN} is printing a large array, it stops printing after it has
5445 printed the number of elements set by the @code{set print elements} command.
5446 This limit also applies to the display of strings.
5447 When @value{GDBN} starts, this limit is set to 200.
5448 Setting @var{number-of-elements} to zero means that the printing is unlimited.
5450 @item show print elements
5451 Display the number of elements of a large array that @value{GDBN} will print.
5452 If the number is 0, then the printing is unlimited.
5454 @item set print null-stop
5455 @cindex @sc{null} elements in arrays
5456 Cause @value{GDBN} to stop printing the characters of an array when the first
5457 @sc{null} is encountered. This is useful when large arrays actually
5458 contain only short strings.
5461 @item set print pretty on
5462 Cause @value{GDBN} to print structures in an indented format with one member
5463 per line, like this:
5478 @item set print pretty off
5479 Cause @value{GDBN} to print structures in a compact format, like this:
5483 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
5484 meat = 0x54 "Pork"@}
5489 This is the default format.
5491 @item show print pretty
5492 Show which format @value{GDBN} is using to print structures.
5494 @item set print sevenbit-strings on
5495 @cindex eight-bit characters in strings
5496 @cindex octal escapes in strings
5497 Print using only seven-bit characters; if this option is set,
5498 @value{GDBN} displays any eight-bit characters (in strings or
5499 character values) using the notation @code{\}@var{nnn}. This setting is
5500 best if you are working in English (@sc{ascii}) and you use the
5501 high-order bit of characters as a marker or ``meta'' bit.
5503 @item set print sevenbit-strings off
5504 Print full eight-bit characters. This allows the use of more
5505 international character sets, and is the default.
5507 @item show print sevenbit-strings
5508 Show whether or not @value{GDBN} is printing only seven-bit characters.
5510 @item set print union on
5511 @cindex unions in structures, printing
5512 Tell @value{GDBN} to print unions which are contained in structures. This
5513 is the default setting.
5515 @item set print union off
5516 Tell @value{GDBN} not to print unions which are contained in structures.
5518 @item show print union
5519 Ask @value{GDBN} whether or not it will print unions which are contained in
5522 For example, given the declarations
5525 typedef enum @{Tree, Bug@} Species;
5526 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
5527 typedef enum @{Caterpillar, Cocoon, Butterfly@}
5538 struct thing foo = @{Tree, @{Acorn@}@};
5542 with @code{set print union on} in effect @samp{p foo} would print
5545 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
5549 and with @code{set print union off} in effect it would print
5552 $1 = @{it = Tree, form = @{...@}@}
5558 These settings are of interest when debugging C@t{++} programs:
5561 @cindex demangling C@t{++} names
5562 @item set print demangle
5563 @itemx set print demangle on
5564 Print C@t{++} names in their source form rather than in the encoded
5565 (``mangled'') form passed to the assembler and linker for type-safe
5566 linkage. The default is on.
5568 @item show print demangle
5569 Show whether C@t{++} names are printed in mangled or demangled form.
5571 @item set print asm-demangle
5572 @itemx set print asm-demangle on
5573 Print C@t{++} names in their source form rather than their mangled form, even
5574 in assembler code printouts such as instruction disassemblies.
5577 @item show print asm-demangle
5578 Show whether C@t{++} names in assembly listings are printed in mangled
5581 @cindex C@t{++} symbol decoding style
5582 @cindex symbol decoding style, C@t{++}
5583 @item set demangle-style @var{style}
5584 Choose among several encoding schemes used by different compilers to
5585 represent C@t{++} names. The choices for @var{style} are currently:
5589 Allow @value{GDBN} to choose a decoding style by inspecting your program.
5592 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
5593 This is the default.
5596 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
5599 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
5602 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
5603 @strong{Warning:} this setting alone is not sufficient to allow
5604 debugging @code{cfront}-generated executables. @value{GDBN} would
5605 require further enhancement to permit that.
5608 If you omit @var{style}, you will see a list of possible formats.
5610 @item show demangle-style
5611 Display the encoding style currently in use for decoding C@t{++} symbols.
5613 @item set print object
5614 @itemx set print object on
5615 @cindex derived type of an object, printing
5616 When displaying a pointer to an object, identify the @emph{actual}
5617 (derived) type of the object rather than the @emph{declared} type, using
5618 the virtual function table.
5620 @item set print object off
5621 Display only the declared type of objects, without reference to the
5622 virtual function table. This is the default setting.
5624 @item show print object
5625 Show whether actual, or declared, object types are displayed.
5627 @item set print static-members
5628 @itemx set print static-members on
5629 @cindex static members of C@t{++} objects
5630 Print static members when displaying a C@t{++} object. The default is on.
5632 @item set print static-members off
5633 Do not print static members when displaying a C@t{++} object.
5635 @item show print static-members
5636 Show whether C@t{++} static members are printed, or not.
5638 @c These don't work with HP ANSI C++ yet.
5639 @item set print vtbl
5640 @itemx set print vtbl on
5641 @cindex pretty print C@t{++} virtual function tables
5642 Pretty print C@t{++} virtual function tables. The default is off.
5643 (The @code{vtbl} commands do not work on programs compiled with the HP
5644 ANSI C@t{++} compiler (@code{aCC}).)
5646 @item set print vtbl off
5647 Do not pretty print C@t{++} virtual function tables.
5649 @item show print vtbl
5650 Show whether C@t{++} virtual function tables are pretty printed, or not.
5654 @section Value history
5656 @cindex value history
5657 Values printed by the @code{print} command are saved in the @value{GDBN}
5658 @dfn{value history}. This allows you to refer to them in other expressions.
5659 Values are kept until the symbol table is re-read or discarded
5660 (for example with the @code{file} or @code{symbol-file} commands).
5661 When the symbol table changes, the value history is discarded,
5662 since the values may contain pointers back to the types defined in the
5667 @cindex history number
5668 The values printed are given @dfn{history numbers} by which you can
5669 refer to them. These are successive integers starting with one.
5670 @code{print} shows you the history number assigned to a value by
5671 printing @samp{$@var{num} = } before the value; here @var{num} is the
5674 To refer to any previous value, use @samp{$} followed by the value's
5675 history number. The way @code{print} labels its output is designed to
5676 remind you of this. Just @code{$} refers to the most recent value in
5677 the history, and @code{$$} refers to the value before that.
5678 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
5679 is the value just prior to @code{$$}, @code{$$1} is equivalent to
5680 @code{$$}, and @code{$$0} is equivalent to @code{$}.
5682 For example, suppose you have just printed a pointer to a structure and
5683 want to see the contents of the structure. It suffices to type
5689 If you have a chain of structures where the component @code{next} points
5690 to the next one, you can print the contents of the next one with this:
5697 You can print successive links in the chain by repeating this
5698 command---which you can do by just typing @key{RET}.
5700 Note that the history records values, not expressions. If the value of
5701 @code{x} is 4 and you type these commands:
5709 then the value recorded in the value history by the @code{print} command
5710 remains 4 even though the value of @code{x} has changed.
5715 Print the last ten values in the value history, with their item numbers.
5716 This is like @samp{p@ $$9} repeated ten times, except that @code{show
5717 values} does not change the history.
5719 @item show values @var{n}
5720 Print ten history values centered on history item number @var{n}.
5723 Print ten history values just after the values last printed. If no more
5724 values are available, @code{show values +} produces no display.
5727 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
5728 same effect as @samp{show values +}.
5730 @node Convenience Vars
5731 @section Convenience variables
5733 @cindex convenience variables
5734 @value{GDBN} provides @dfn{convenience variables} that you can use within
5735 @value{GDBN} to hold on to a value and refer to it later. These variables
5736 exist entirely within @value{GDBN}; they are not part of your program, and
5737 setting a convenience variable has no direct effect on further execution
5738 of your program. That is why you can use them freely.
5740 Convenience variables are prefixed with @samp{$}. Any name preceded by
5741 @samp{$} can be used for a convenience variable, unless it is one of
5742 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
5743 (Value history references, in contrast, are @emph{numbers} preceded
5744 by @samp{$}. @xref{Value History, ,Value history}.)
5746 You can save a value in a convenience variable with an assignment
5747 expression, just as you would set a variable in your program.
5751 set $foo = *object_ptr
5755 would save in @code{$foo} the value contained in the object pointed to by
5758 Using a convenience variable for the first time creates it, but its
5759 value is @code{void} until you assign a new value. You can alter the
5760 value with another assignment at any time.
5762 Convenience variables have no fixed types. You can assign a convenience
5763 variable any type of value, including structures and arrays, even if
5764 that variable already has a value of a different type. The convenience
5765 variable, when used as an expression, has the type of its current value.
5768 @kindex show convenience
5769 @item show convenience
5770 Print a list of convenience variables used so far, and their values.
5771 Abbreviated @code{show conv}.
5774 One of the ways to use a convenience variable is as a counter to be
5775 incremented or a pointer to be advanced. For example, to print
5776 a field from successive elements of an array of structures:
5780 print bar[$i++]->contents
5784 Repeat that command by typing @key{RET}.
5786 Some convenience variables are created automatically by @value{GDBN} and given
5787 values likely to be useful.
5790 @vindex $_@r{, convenience variable}
5792 The variable @code{$_} is automatically set by the @code{x} command to
5793 the last address examined (@pxref{Memory, ,Examining memory}). Other
5794 commands which provide a default address for @code{x} to examine also
5795 set @code{$_} to that address; these commands include @code{info line}
5796 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
5797 except when set by the @code{x} command, in which case it is a pointer
5798 to the type of @code{$__}.
5800 @vindex $__@r{, convenience variable}
5802 The variable @code{$__} is automatically set by the @code{x} command
5803 to the value found in the last address examined. Its type is chosen
5804 to match the format in which the data was printed.
5807 @vindex $_exitcode@r{, convenience variable}
5808 The variable @code{$_exitcode} is automatically set to the exit code when
5809 the program being debugged terminates.
5812 On HP-UX systems, if you refer to a function or variable name that
5813 begins with a dollar sign, @value{GDBN} searches for a user or system
5814 name first, before it searches for a convenience variable.
5820 You can refer to machine register contents, in expressions, as variables
5821 with names starting with @samp{$}. The names of registers are different
5822 for each machine; use @code{info registers} to see the names used on
5826 @kindex info registers
5827 @item info registers
5828 Print the names and values of all registers except floating-point
5829 and vector registers (in the selected stack frame).
5831 @kindex info all-registers
5832 @cindex floating point registers
5833 @item info all-registers
5834 Print the names and values of all registers, including floating-point
5835 and vector registers (in the selected stack frame).
5837 @item info registers @var{regname} @dots{}
5838 Print the @dfn{relativized} value of each specified register @var{regname}.
5839 As discussed in detail below, register values are normally relative to
5840 the selected stack frame. @var{regname} may be any register name valid on
5841 the machine you are using, with or without the initial @samp{$}.
5844 @value{GDBN} has four ``standard'' register names that are available (in
5845 expressions) on most machines---whenever they do not conflict with an
5846 architecture's canonical mnemonics for registers. The register names
5847 @code{$pc} and @code{$sp} are used for the program counter register and
5848 the stack pointer. @code{$fp} is used for a register that contains a
5849 pointer to the current stack frame, and @code{$ps} is used for a
5850 register that contains the processor status. For example,
5851 you could print the program counter in hex with
5858 or print the instruction to be executed next with
5865 or add four to the stack pointer@footnote{This is a way of removing
5866 one word from the stack, on machines where stacks grow downward in
5867 memory (most machines, nowadays). This assumes that the innermost
5868 stack frame is selected; setting @code{$sp} is not allowed when other
5869 stack frames are selected. To pop entire frames off the stack,
5870 regardless of machine architecture, use @code{return};
5871 see @ref{Returning, ,Returning from a function}.} with
5877 Whenever possible, these four standard register names are available on
5878 your machine even though the machine has different canonical mnemonics,
5879 so long as there is no conflict. The @code{info registers} command
5880 shows the canonical names. For example, on the SPARC, @code{info
5881 registers} displays the processor status register as @code{$psr} but you
5882 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
5883 is an alias for the @sc{eflags} register.
5885 @value{GDBN} always considers the contents of an ordinary register as an
5886 integer when the register is examined in this way. Some machines have
5887 special registers which can hold nothing but floating point; these
5888 registers are considered to have floating point values. There is no way
5889 to refer to the contents of an ordinary register as floating point value
5890 (although you can @emph{print} it as a floating point value with
5891 @samp{print/f $@var{regname}}).
5893 Some registers have distinct ``raw'' and ``virtual'' data formats. This
5894 means that the data format in which the register contents are saved by
5895 the operating system is not the same one that your program normally
5896 sees. For example, the registers of the 68881 floating point
5897 coprocessor are always saved in ``extended'' (raw) format, but all C
5898 programs expect to work with ``double'' (virtual) format. In such
5899 cases, @value{GDBN} normally works with the virtual format only (the format
5900 that makes sense for your program), but the @code{info registers} command
5901 prints the data in both formats.
5903 Normally, register values are relative to the selected stack frame
5904 (@pxref{Selection, ,Selecting a frame}). This means that you get the
5905 value that the register would contain if all stack frames farther in
5906 were exited and their saved registers restored. In order to see the
5907 true contents of hardware registers, you must select the innermost
5908 frame (with @samp{frame 0}).
5910 However, @value{GDBN} must deduce where registers are saved, from the machine
5911 code generated by your compiler. If some registers are not saved, or if
5912 @value{GDBN} is unable to locate the saved registers, the selected stack
5913 frame makes no difference.
5915 @node Floating Point Hardware
5916 @section Floating point hardware
5917 @cindex floating point
5919 Depending on the configuration, @value{GDBN} may be able to give
5920 you more information about the status of the floating point hardware.
5925 Display hardware-dependent information about the floating
5926 point unit. The exact contents and layout vary depending on the
5927 floating point chip. Currently, @samp{info float} is supported on
5928 the ARM and x86 machines.
5932 @section Vector Unit
5935 Depending on the configuration, @value{GDBN} may be able to give you
5936 more information about the status of the vector unit.
5941 Display information about the vector unit. The exact contents and
5942 layout vary depending on the hardware.
5945 @node Auxiliary Vector
5946 @section Operating system auxiliary vector
5947 @cindex auxiliary vector
5948 @cindex vector, auxiliary
5950 Some operating systems supply an @dfn{auxiliary vector} to programs at
5951 startup. This is akin to the arguments and environment that you
5952 specify for a program, but contains a system-dependent variety of
5953 binary values that tell system libraries important details about the
5954 hardware, operating system, and process. Each value's purpose is
5955 identified by an integer tag; the meanings are well-known but system-specific.
5956 Depending on the configuration and operating system facilities,
5957 @value{GDBN} may be able to show you this information.
5962 Display the auxiliary vector of the inferior, which can be either a
5963 live process or a core dump file. @value{GDBN} prints each tag value
5964 numerically, and also shows names and text descriptions for recognized
5965 tags. Some values in the vector are numbers, some bit masks, and some
5966 pointers to strings or other data. @value{GDBN} displays each value in the
5967 most appropriate form for a recognized tag, and in hexadecimal for
5968 an unrecognized tag.
5971 @node Memory Region Attributes
5972 @section Memory region attributes
5973 @cindex memory region attributes
5975 @dfn{Memory region attributes} allow you to describe special handling
5976 required by regions of your target's memory. @value{GDBN} uses attributes
5977 to determine whether to allow certain types of memory accesses; whether to
5978 use specific width accesses; and whether to cache target memory.
5980 Defined memory regions can be individually enabled and disabled. When a
5981 memory region is disabled, @value{GDBN} uses the default attributes when
5982 accessing memory in that region. Similarly, if no memory regions have
5983 been defined, @value{GDBN} uses the default attributes when accessing
5986 When a memory region is defined, it is given a number to identify it;
5987 to enable, disable, or remove a memory region, you specify that number.
5991 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
5992 Define memory region bounded by @var{lower} and @var{upper} with
5993 attributes @var{attributes}@dots{}. Note that @var{upper} == 0 is a
5994 special case: it is treated as the the target's maximum memory address.
5995 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
5998 @item delete mem @var{nums}@dots{}
5999 Remove memory regions @var{nums}@dots{}.
6002 @item disable mem @var{nums}@dots{}
6003 Disable memory regions @var{nums}@dots{}.
6004 A disabled memory region is not forgotten.
6005 It may be enabled again later.
6008 @item enable mem @var{nums}@dots{}
6009 Enable memory regions @var{nums}@dots{}.
6013 Print a table of all defined memory regions, with the following columns
6017 @item Memory Region Number
6018 @item Enabled or Disabled.
6019 Enabled memory regions are marked with @samp{y}.
6020 Disabled memory regions are marked with @samp{n}.
6023 The address defining the inclusive lower bound of the memory region.
6026 The address defining the exclusive upper bound of the memory region.
6029 The list of attributes set for this memory region.
6034 @subsection Attributes
6036 @subsubsection Memory Access Mode
6037 The access mode attributes set whether @value{GDBN} may make read or
6038 write accesses to a memory region.
6040 While these attributes prevent @value{GDBN} from performing invalid
6041 memory accesses, they do nothing to prevent the target system, I/O DMA,
6042 etc. from accessing memory.
6046 Memory is read only.
6048 Memory is write only.
6050 Memory is read/write. This is the default.
6053 @subsubsection Memory Access Size
6054 The acccess size attributes tells @value{GDBN} to use specific sized
6055 accesses in the memory region. Often memory mapped device registers
6056 require specific sized accesses. If no access size attribute is
6057 specified, @value{GDBN} may use accesses of any size.
6061 Use 8 bit memory accesses.
6063 Use 16 bit memory accesses.
6065 Use 32 bit memory accesses.
6067 Use 64 bit memory accesses.
6070 @c @subsubsection Hardware/Software Breakpoints
6071 @c The hardware/software breakpoint attributes set whether @value{GDBN}
6072 @c will use hardware or software breakpoints for the internal breakpoints
6073 @c used by the step, next, finish, until, etc. commands.
6077 @c Always use hardware breakpoints
6078 @c @item swbreak (default)
6081 @subsubsection Data Cache
6082 The data cache attributes set whether @value{GDBN} will cache target
6083 memory. While this generally improves performance by reducing debug
6084 protocol overhead, it can lead to incorrect results because @value{GDBN}
6085 does not know about volatile variables or memory mapped device
6090 Enable @value{GDBN} to cache target memory.
6092 Disable @value{GDBN} from caching target memory. This is the default.
6095 @c @subsubsection Memory Write Verification
6096 @c The memory write verification attributes set whether @value{GDBN}
6097 @c will re-reads data after each write to verify the write was successful.
6101 @c @item noverify (default)
6104 @node Dump/Restore Files
6105 @section Copy between memory and a file
6106 @cindex dump/restore files
6107 @cindex append data to a file
6108 @cindex dump data to a file
6109 @cindex restore data from a file
6111 You can use the commands @code{dump}, @code{append}, and
6112 @code{restore} to copy data between target memory and a file. The
6113 @code{dump} and @code{append} commands write data to a file, and the
6114 @code{restore} command reads data from a file back into the inferior's
6115 memory. Files may be in binary, Motorola S-record, Intel hex, or
6116 Tektronix Hex format; however, @value{GDBN} can only append to binary
6122 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6123 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
6124 Dump the contents of memory from @var{start_addr} to @var{end_addr},
6125 or the value of @var{expr}, to @var{filename} in the given format.
6127 The @var{format} parameter may be any one of:
6134 Motorola S-record format.
6136 Tektronix Hex format.
6139 @value{GDBN} uses the same definitions of these formats as the
6140 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
6141 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
6145 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6146 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
6147 Append the contents of memory from @var{start_addr} to @var{end_addr},
6148 or the value of @var{expr}, to @var{filename}, in raw binary form.
6149 (@value{GDBN} can only append data to files in raw binary form.)
6152 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
6153 Restore the contents of file @var{filename} into memory. The
6154 @code{restore} command can automatically recognize any known @sc{bfd}
6155 file format, except for raw binary. To restore a raw binary file you
6156 must specify the optional keyword @code{binary} after the filename.
6158 If @var{bias} is non-zero, its value will be added to the addresses
6159 contained in the file. Binary files always start at address zero, so
6160 they will be restored at address @var{bias}. Other bfd files have
6161 a built-in location; they will be restored at offset @var{bias}
6164 If @var{start} and/or @var{end} are non-zero, then only data between
6165 file offset @var{start} and file offset @var{end} will be restored.
6166 These offsets are relative to the addresses in the file, before
6167 the @var{bias} argument is applied.
6171 @node Character Sets
6172 @section Character Sets
6173 @cindex character sets
6175 @cindex translating between character sets
6176 @cindex host character set
6177 @cindex target character set
6179 If the program you are debugging uses a different character set to
6180 represent characters and strings than the one @value{GDBN} uses itself,
6181 @value{GDBN} can automatically translate between the character sets for
6182 you. The character set @value{GDBN} uses we call the @dfn{host
6183 character set}; the one the inferior program uses we call the
6184 @dfn{target character set}.
6186 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
6187 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
6188 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
6189 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
6190 then the host character set is Latin-1, and the target character set is
6191 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
6192 target-charset EBCDIC-US}, then @value{GDBN} translates between
6193 @sc{ebcdic} and Latin 1 as you print character or string values, or use
6194 character and string literals in expressions.
6196 @value{GDBN} has no way to automatically recognize which character set
6197 the inferior program uses; you must tell it, using the @code{set
6198 target-charset} command, described below.
6200 Here are the commands for controlling @value{GDBN}'s character set
6204 @item set target-charset @var{charset}
6205 @kindex set target-charset
6206 Set the current target character set to @var{charset}. We list the
6207 character set names @value{GDBN} recognizes below, but if you type
6208 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6209 list the target character sets it supports.
6213 @item set host-charset @var{charset}
6214 @kindex set host-charset
6215 Set the current host character set to @var{charset}.
6217 By default, @value{GDBN} uses a host character set appropriate to the
6218 system it is running on; you can override that default using the
6219 @code{set host-charset} command.
6221 @value{GDBN} can only use certain character sets as its host character
6222 set. We list the character set names @value{GDBN} recognizes below, and
6223 indicate which can be host character sets, but if you type
6224 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6225 list the host character sets it supports.
6227 @item set charset @var{charset}
6229 Set the current host and target character sets to @var{charset}. As
6230 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
6231 @value{GDBN} will list the name of the character sets that can be used
6232 for both host and target.
6236 @kindex show charset
6237 Show the names of the current host and target charsets.
6239 @itemx show host-charset
6240 @kindex show host-charset
6241 Show the name of the current host charset.
6243 @itemx show target-charset
6244 @kindex show target-charset
6245 Show the name of the current target charset.
6249 @value{GDBN} currently includes support for the following character
6255 @cindex ASCII character set
6256 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
6260 @cindex ISO 8859-1 character set
6261 @cindex ISO Latin 1 character set
6262 The ISO Latin 1 character set. This extends @sc{ascii} with accented
6263 characters needed for French, German, and Spanish. @value{GDBN} can use
6264 this as its host character set.
6268 @cindex EBCDIC character set
6269 @cindex IBM1047 character set
6270 Variants of the @sc{ebcdic} character set, used on some of IBM's
6271 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
6272 @value{GDBN} cannot use these as its host character set.
6276 Note that these are all single-byte character sets. More work inside
6277 GDB is needed to support multi-byte or variable-width character
6278 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
6280 Here is an example of @value{GDBN}'s character set support in action.
6281 Assume that the following source code has been placed in the file
6282 @file{charset-test.c}:
6288 = @{72, 101, 108, 108, 111, 44, 32, 119,
6289 111, 114, 108, 100, 33, 10, 0@};
6290 char ibm1047_hello[]
6291 = @{200, 133, 147, 147, 150, 107, 64, 166,
6292 150, 153, 147, 132, 90, 37, 0@};
6296 printf ("Hello, world!\n");
6300 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
6301 containing the string @samp{Hello, world!} followed by a newline,
6302 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
6304 We compile the program, and invoke the debugger on it:
6307 $ gcc -g charset-test.c -o charset-test
6308 $ gdb -nw charset-test
6309 GNU gdb 2001-12-19-cvs
6310 Copyright 2001 Free Software Foundation, Inc.
6315 We can use the @code{show charset} command to see what character sets
6316 @value{GDBN} is currently using to interpret and display characters and
6320 (@value{GDBP}) show charset
6321 The current host and target character set is `ISO-8859-1'.
6325 For the sake of printing this manual, let's use @sc{ascii} as our
6326 initial character set:
6328 (@value{GDBP}) set charset ASCII
6329 (@value{GDBP}) show charset
6330 The current host and target character set is `ASCII'.
6334 Let's assume that @sc{ascii} is indeed the correct character set for our
6335 host system --- in other words, let's assume that if @value{GDBN} prints
6336 characters using the @sc{ascii} character set, our terminal will display
6337 them properly. Since our current target character set is also
6338 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
6341 (@value{GDBP}) print ascii_hello
6342 $1 = 0x401698 "Hello, world!\n"
6343 (@value{GDBP}) print ascii_hello[0]
6348 @value{GDBN} uses the target character set for character and string
6349 literals you use in expressions:
6352 (@value{GDBP}) print '+'
6357 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
6360 @value{GDBN} relies on the user to tell it which character set the
6361 target program uses. If we print @code{ibm1047_hello} while our target
6362 character set is still @sc{ascii}, we get jibberish:
6365 (@value{GDBP}) print ibm1047_hello
6366 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
6367 (@value{GDBP}) print ibm1047_hello[0]
6372 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
6373 @value{GDBN} tells us the character sets it supports:
6376 (@value{GDBP}) set target-charset
6377 ASCII EBCDIC-US IBM1047 ISO-8859-1
6378 (@value{GDBP}) set target-charset
6381 We can select @sc{ibm1047} as our target character set, and examine the
6382 program's strings again. Now the @sc{ascii} string is wrong, but
6383 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
6384 target character set, @sc{ibm1047}, to the host character set,
6385 @sc{ascii}, and they display correctly:
6388 (@value{GDBP}) set target-charset IBM1047
6389 (@value{GDBP}) show charset
6390 The current host character set is `ASCII'.
6391 The current target character set is `IBM1047'.
6392 (@value{GDBP}) print ascii_hello
6393 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
6394 (@value{GDBP}) print ascii_hello[0]
6396 (@value{GDBP}) print ibm1047_hello
6397 $8 = 0x4016a8 "Hello, world!\n"
6398 (@value{GDBP}) print ibm1047_hello[0]
6403 As above, @value{GDBN} uses the target character set for character and
6404 string literals you use in expressions:
6407 (@value{GDBP}) print '+'
6412 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
6417 @chapter C Preprocessor Macros
6419 Some languages, such as C and C@t{++}, provide a way to define and invoke
6420 ``preprocessor macros'' which expand into strings of tokens.
6421 @value{GDBN} can evaluate expressions containing macro invocations, show
6422 the result of macro expansion, and show a macro's definition, including
6423 where it was defined.
6425 You may need to compile your program specially to provide @value{GDBN}
6426 with information about preprocessor macros. Most compilers do not
6427 include macros in their debugging information, even when you compile
6428 with the @option{-g} flag. @xref{Compilation}.
6430 A program may define a macro at one point, remove that definition later,
6431 and then provide a different definition after that. Thus, at different
6432 points in the program, a macro may have different definitions, or have
6433 no definition at all. If there is a current stack frame, @value{GDBN}
6434 uses the macros in scope at that frame's source code line. Otherwise,
6435 @value{GDBN} uses the macros in scope at the current listing location;
6438 At the moment, @value{GDBN} does not support the @code{##}
6439 token-splicing operator, the @code{#} stringification operator, or
6440 variable-arity macros.
6442 Whenever @value{GDBN} evaluates an expression, it always expands any
6443 macro invocations present in the expression. @value{GDBN} also provides
6444 the following commands for working with macros explicitly.
6448 @kindex macro expand
6449 @cindex macro expansion, showing the results of preprocessor
6450 @cindex preprocessor macro expansion, showing the results of
6451 @cindex expanding preprocessor macros
6452 @item macro expand @var{expression}
6453 @itemx macro exp @var{expression}
6454 Show the results of expanding all preprocessor macro invocations in
6455 @var{expression}. Since @value{GDBN} simply expands macros, but does
6456 not parse the result, @var{expression} need not be a valid expression;
6457 it can be any string of tokens.
6459 @item macro expand-once @var{expression}
6460 @itemx macro exp1 @var{expression}
6461 @cindex expand macro once
6462 @i{(This command is not yet implemented.)} Show the results of
6463 expanding those preprocessor macro invocations that appear explicitly in
6464 @var{expression}. Macro invocations appearing in that expansion are
6465 left unchanged. This command allows you to see the effect of a
6466 particular macro more clearly, without being confused by further
6467 expansions. Since @value{GDBN} simply expands macros, but does not
6468 parse the result, @var{expression} need not be a valid expression; it
6469 can be any string of tokens.
6472 @cindex macro definition, showing
6473 @cindex definition, showing a macro's
6474 @item info macro @var{macro}
6475 Show the definition of the macro named @var{macro}, and describe the
6476 source location where that definition was established.
6478 @kindex macro define
6479 @cindex user-defined macros
6480 @cindex defining macros interactively
6481 @cindex macros, user-defined
6482 @item macro define @var{macro} @var{replacement-list}
6483 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
6484 @i{(This command is not yet implemented.)} Introduce a definition for a
6485 preprocessor macro named @var{macro}, invocations of which are replaced
6486 by the tokens given in @var{replacement-list}. The first form of this
6487 command defines an ``object-like'' macro, which takes no arguments; the
6488 second form defines a ``function-like'' macro, which takes the arguments
6489 given in @var{arglist}.
6491 A definition introduced by this command is in scope in every expression
6492 evaluated in @value{GDBN}, until it is removed with the @command{macro
6493 undef} command, described below. The definition overrides all
6494 definitions for @var{macro} present in the program being debugged, as
6495 well as any previous user-supplied definition.
6498 @item macro undef @var{macro}
6499 @i{(This command is not yet implemented.)} Remove any user-supplied
6500 definition for the macro named @var{macro}. This command only affects
6501 definitions provided with the @command{macro define} command, described
6502 above; it cannot remove definitions present in the program being
6507 @cindex macros, example of debugging with
6508 Here is a transcript showing the above commands in action. First, we
6509 show our source files:
6517 #define ADD(x) (M + x)
6522 printf ("Hello, world!\n");
6524 printf ("We're so creative.\n");
6526 printf ("Goodbye, world!\n");
6533 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
6534 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
6535 compiler includes information about preprocessor macros in the debugging
6539 $ gcc -gdwarf-2 -g3 sample.c -o sample
6543 Now, we start @value{GDBN} on our sample program:
6547 GNU gdb 2002-05-06-cvs
6548 Copyright 2002 Free Software Foundation, Inc.
6549 GDB is free software, @dots{}
6553 We can expand macros and examine their definitions, even when the
6554 program is not running. @value{GDBN} uses the current listing position
6555 to decide which macro definitions are in scope:
6558 (@value{GDBP}) list main
6561 5 #define ADD(x) (M + x)
6566 10 printf ("Hello, world!\n");
6568 12 printf ("We're so creative.\n");
6569 (@value{GDBP}) info macro ADD
6570 Defined at /home/jimb/gdb/macros/play/sample.c:5
6571 #define ADD(x) (M + x)
6572 (@value{GDBP}) info macro Q
6573 Defined at /home/jimb/gdb/macros/play/sample.h:1
6574 included at /home/jimb/gdb/macros/play/sample.c:2
6576 (@value{GDBP}) macro expand ADD(1)
6577 expands to: (42 + 1)
6578 (@value{GDBP}) macro expand-once ADD(1)
6579 expands to: once (M + 1)
6583 In the example above, note that @command{macro expand-once} expands only
6584 the macro invocation explicit in the original text --- the invocation of
6585 @code{ADD} --- but does not expand the invocation of the macro @code{M},
6586 which was introduced by @code{ADD}.
6588 Once the program is running, GDB uses the macro definitions in force at
6589 the source line of the current stack frame:
6592 (@value{GDBP}) break main
6593 Breakpoint 1 at 0x8048370: file sample.c, line 10.
6595 Starting program: /home/jimb/gdb/macros/play/sample
6597 Breakpoint 1, main () at sample.c:10
6598 10 printf ("Hello, world!\n");
6602 At line 10, the definition of the macro @code{N} at line 9 is in force:
6605 (@value{GDBP}) info macro N
6606 Defined at /home/jimb/gdb/macros/play/sample.c:9
6608 (@value{GDBP}) macro expand N Q M
6610 (@value{GDBP}) print N Q M
6615 As we step over directives that remove @code{N}'s definition, and then
6616 give it a new definition, @value{GDBN} finds the definition (or lack
6617 thereof) in force at each point:
6622 12 printf ("We're so creative.\n");
6623 (@value{GDBP}) info macro N
6624 The symbol `N' has no definition as a C/C++ preprocessor macro
6625 at /home/jimb/gdb/macros/play/sample.c:12
6628 14 printf ("Goodbye, world!\n");
6629 (@value{GDBP}) info macro N
6630 Defined at /home/jimb/gdb/macros/play/sample.c:13
6632 (@value{GDBP}) macro expand N Q M
6633 expands to: 1729 < 42
6634 (@value{GDBP}) print N Q M
6641 @chapter Tracepoints
6642 @c This chapter is based on the documentation written by Michael
6643 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
6646 In some applications, it is not feasible for the debugger to interrupt
6647 the program's execution long enough for the developer to learn
6648 anything helpful about its behavior. If the program's correctness
6649 depends on its real-time behavior, delays introduced by a debugger
6650 might cause the program to change its behavior drastically, or perhaps
6651 fail, even when the code itself is correct. It is useful to be able
6652 to observe the program's behavior without interrupting it.
6654 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
6655 specify locations in the program, called @dfn{tracepoints}, and
6656 arbitrary expressions to evaluate when those tracepoints are reached.
6657 Later, using the @code{tfind} command, you can examine the values
6658 those expressions had when the program hit the tracepoints. The
6659 expressions may also denote objects in memory---structures or arrays,
6660 for example---whose values @value{GDBN} should record; while visiting
6661 a particular tracepoint, you may inspect those objects as if they were
6662 in memory at that moment. However, because @value{GDBN} records these
6663 values without interacting with you, it can do so quickly and
6664 unobtrusively, hopefully not disturbing the program's behavior.
6666 The tracepoint facility is currently available only for remote
6667 targets. @xref{Targets}. In addition, your remote target must know how
6668 to collect trace data. This functionality is implemented in the remote
6669 stub; however, none of the stubs distributed with @value{GDBN} support
6670 tracepoints as of this writing.
6672 This chapter describes the tracepoint commands and features.
6676 * Analyze Collected Data::
6677 * Tracepoint Variables::
6680 @node Set Tracepoints
6681 @section Commands to Set Tracepoints
6683 Before running such a @dfn{trace experiment}, an arbitrary number of
6684 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
6685 tracepoint has a number assigned to it by @value{GDBN}. Like with
6686 breakpoints, tracepoint numbers are successive integers starting from
6687 one. Many of the commands associated with tracepoints take the
6688 tracepoint number as their argument, to identify which tracepoint to
6691 For each tracepoint, you can specify, in advance, some arbitrary set
6692 of data that you want the target to collect in the trace buffer when
6693 it hits that tracepoint. The collected data can include registers,
6694 local variables, or global data. Later, you can use @value{GDBN}
6695 commands to examine the values these data had at the time the
6698 This section describes commands to set tracepoints and associated
6699 conditions and actions.
6702 * Create and Delete Tracepoints::
6703 * Enable and Disable Tracepoints::
6704 * Tracepoint Passcounts::
6705 * Tracepoint Actions::
6706 * Listing Tracepoints::
6707 * Starting and Stopping Trace Experiment::
6710 @node Create and Delete Tracepoints
6711 @subsection Create and Delete Tracepoints
6714 @cindex set tracepoint
6717 The @code{trace} command is very similar to the @code{break} command.
6718 Its argument can be a source line, a function name, or an address in
6719 the target program. @xref{Set Breaks}. The @code{trace} command
6720 defines a tracepoint, which is a point in the target program where the
6721 debugger will briefly stop, collect some data, and then allow the
6722 program to continue. Setting a tracepoint or changing its commands
6723 doesn't take effect until the next @code{tstart} command; thus, you
6724 cannot change the tracepoint attributes once a trace experiment is
6727 Here are some examples of using the @code{trace} command:
6730 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
6732 (@value{GDBP}) @b{trace +2} // 2 lines forward
6734 (@value{GDBP}) @b{trace my_function} // first source line of function
6736 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
6738 (@value{GDBP}) @b{trace *0x2117c4} // an address
6742 You can abbreviate @code{trace} as @code{tr}.
6745 @cindex last tracepoint number
6746 @cindex recent tracepoint number
6747 @cindex tracepoint number
6748 The convenience variable @code{$tpnum} records the tracepoint number
6749 of the most recently set tracepoint.
6751 @kindex delete tracepoint
6752 @cindex tracepoint deletion
6753 @item delete tracepoint @r{[}@var{num}@r{]}
6754 Permanently delete one or more tracepoints. With no argument, the
6755 default is to delete all tracepoints.
6760 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
6762 (@value{GDBP}) @b{delete trace} // remove all tracepoints
6766 You can abbreviate this command as @code{del tr}.
6769 @node Enable and Disable Tracepoints
6770 @subsection Enable and Disable Tracepoints
6773 @kindex disable tracepoint
6774 @item disable tracepoint @r{[}@var{num}@r{]}
6775 Disable tracepoint @var{num}, or all tracepoints if no argument
6776 @var{num} is given. A disabled tracepoint will have no effect during
6777 the next trace experiment, but it is not forgotten. You can re-enable
6778 a disabled tracepoint using the @code{enable tracepoint} command.
6780 @kindex enable tracepoint
6781 @item enable tracepoint @r{[}@var{num}@r{]}
6782 Enable tracepoint @var{num}, or all tracepoints. The enabled
6783 tracepoints will become effective the next time a trace experiment is
6787 @node Tracepoint Passcounts
6788 @subsection Tracepoint Passcounts
6792 @cindex tracepoint pass count
6793 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
6794 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
6795 automatically stop a trace experiment. If a tracepoint's passcount is
6796 @var{n}, then the trace experiment will be automatically stopped on
6797 the @var{n}'th time that tracepoint is hit. If the tracepoint number
6798 @var{num} is not specified, the @code{passcount} command sets the
6799 passcount of the most recently defined tracepoint. If no passcount is
6800 given, the trace experiment will run until stopped explicitly by the
6806 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
6807 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
6809 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
6810 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
6811 (@value{GDBP}) @b{trace foo}
6812 (@value{GDBP}) @b{pass 3}
6813 (@value{GDBP}) @b{trace bar}
6814 (@value{GDBP}) @b{pass 2}
6815 (@value{GDBP}) @b{trace baz}
6816 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
6817 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
6818 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
6819 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
6823 @node Tracepoint Actions
6824 @subsection Tracepoint Action Lists
6828 @cindex tracepoint actions
6829 @item actions @r{[}@var{num}@r{]}
6830 This command will prompt for a list of actions to be taken when the
6831 tracepoint is hit. If the tracepoint number @var{num} is not
6832 specified, this command sets the actions for the one that was most
6833 recently defined (so that you can define a tracepoint and then say
6834 @code{actions} without bothering about its number). You specify the
6835 actions themselves on the following lines, one action at a time, and
6836 terminate the actions list with a line containing just @code{end}. So
6837 far, the only defined actions are @code{collect} and
6838 @code{while-stepping}.
6840 @cindex remove actions from a tracepoint
6841 To remove all actions from a tracepoint, type @samp{actions @var{num}}
6842 and follow it immediately with @samp{end}.
6845 (@value{GDBP}) @b{collect @var{data}} // collect some data
6847 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
6849 (@value{GDBP}) @b{end} // signals the end of actions.
6852 In the following example, the action list begins with @code{collect}
6853 commands indicating the things to be collected when the tracepoint is
6854 hit. Then, in order to single-step and collect additional data
6855 following the tracepoint, a @code{while-stepping} command is used,
6856 followed by the list of things to be collected while stepping. The
6857 @code{while-stepping} command is terminated by its own separate
6858 @code{end} command. Lastly, the action list is terminated by an
6862 (@value{GDBP}) @b{trace foo}
6863 (@value{GDBP}) @b{actions}
6864 Enter actions for tracepoint 1, one per line:
6873 @kindex collect @r{(tracepoints)}
6874 @item collect @var{expr1}, @var{expr2}, @dots{}
6875 Collect values of the given expressions when the tracepoint is hit.
6876 This command accepts a comma-separated list of any valid expressions.
6877 In addition to global, static, or local variables, the following
6878 special arguments are supported:
6882 collect all registers
6885 collect all function arguments
6888 collect all local variables.
6891 You can give several consecutive @code{collect} commands, each one
6892 with a single argument, or one @code{collect} command with several
6893 arguments separated by commas: the effect is the same.
6895 The command @code{info scope} (@pxref{Symbols, info scope}) is
6896 particularly useful for figuring out what data to collect.
6898 @kindex while-stepping @r{(tracepoints)}
6899 @item while-stepping @var{n}
6900 Perform @var{n} single-step traces after the tracepoint, collecting
6901 new data at each step. The @code{while-stepping} command is
6902 followed by the list of what to collect while stepping (followed by
6903 its own @code{end} command):
6907 > collect $regs, myglobal
6913 You may abbreviate @code{while-stepping} as @code{ws} or
6917 @node Listing Tracepoints
6918 @subsection Listing Tracepoints
6921 @kindex info tracepoints
6922 @cindex information about tracepoints
6923 @item info tracepoints @r{[}@var{num}@r{]}
6924 Display information about the tracepoint @var{num}. If you don't specify
6925 a tracepoint number, displays information about all the tracepoints
6926 defined so far. For each tracepoint, the following information is
6933 whether it is enabled or disabled
6937 its passcount as given by the @code{passcount @var{n}} command
6939 its step count as given by the @code{while-stepping @var{n}} command
6941 where in the source files is the tracepoint set
6943 its action list as given by the @code{actions} command
6947 (@value{GDBP}) @b{info trace}
6948 Num Enb Address PassC StepC What
6949 1 y 0x002117c4 0 0 <gdb_asm>
6950 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
6951 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
6956 This command can be abbreviated @code{info tp}.
6959 @node Starting and Stopping Trace Experiment
6960 @subsection Starting and Stopping Trace Experiment
6964 @cindex start a new trace experiment
6965 @cindex collected data discarded
6967 This command takes no arguments. It starts the trace experiment, and
6968 begins collecting data. This has the side effect of discarding all
6969 the data collected in the trace buffer during the previous trace
6973 @cindex stop a running trace experiment
6975 This command takes no arguments. It ends the trace experiment, and
6976 stops collecting data.
6978 @strong{Note:} a trace experiment and data collection may stop
6979 automatically if any tracepoint's passcount is reached
6980 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
6983 @cindex status of trace data collection
6984 @cindex trace experiment, status of
6986 This command displays the status of the current trace data
6990 Here is an example of the commands we described so far:
6993 (@value{GDBP}) @b{trace gdb_c_test}
6994 (@value{GDBP}) @b{actions}
6995 Enter actions for tracepoint #1, one per line.
6996 > collect $regs,$locals,$args
7001 (@value{GDBP}) @b{tstart}
7002 [time passes @dots{}]
7003 (@value{GDBP}) @b{tstop}
7007 @node Analyze Collected Data
7008 @section Using the collected data
7010 After the tracepoint experiment ends, you use @value{GDBN} commands
7011 for examining the trace data. The basic idea is that each tracepoint
7012 collects a trace @dfn{snapshot} every time it is hit and another
7013 snapshot every time it single-steps. All these snapshots are
7014 consecutively numbered from zero and go into a buffer, and you can
7015 examine them later. The way you examine them is to @dfn{focus} on a
7016 specific trace snapshot. When the remote stub is focused on a trace
7017 snapshot, it will respond to all @value{GDBN} requests for memory and
7018 registers by reading from the buffer which belongs to that snapshot,
7019 rather than from @emph{real} memory or registers of the program being
7020 debugged. This means that @strong{all} @value{GDBN} commands
7021 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
7022 behave as if we were currently debugging the program state as it was
7023 when the tracepoint occurred. Any requests for data that are not in
7024 the buffer will fail.
7027 * tfind:: How to select a trace snapshot
7028 * tdump:: How to display all data for a snapshot
7029 * save-tracepoints:: How to save tracepoints for a future run
7033 @subsection @code{tfind @var{n}}
7036 @cindex select trace snapshot
7037 @cindex find trace snapshot
7038 The basic command for selecting a trace snapshot from the buffer is
7039 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
7040 counting from zero. If no argument @var{n} is given, the next
7041 snapshot is selected.
7043 Here are the various forms of using the @code{tfind} command.
7047 Find the first snapshot in the buffer. This is a synonym for
7048 @code{tfind 0} (since 0 is the number of the first snapshot).
7051 Stop debugging trace snapshots, resume @emph{live} debugging.
7054 Same as @samp{tfind none}.
7057 No argument means find the next trace snapshot.
7060 Find the previous trace snapshot before the current one. This permits
7061 retracing earlier steps.
7063 @item tfind tracepoint @var{num}
7064 Find the next snapshot associated with tracepoint @var{num}. Search
7065 proceeds forward from the last examined trace snapshot. If no
7066 argument @var{num} is given, it means find the next snapshot collected
7067 for the same tracepoint as the current snapshot.
7069 @item tfind pc @var{addr}
7070 Find the next snapshot associated with the value @var{addr} of the
7071 program counter. Search proceeds forward from the last examined trace
7072 snapshot. If no argument @var{addr} is given, it means find the next
7073 snapshot with the same value of PC as the current snapshot.
7075 @item tfind outside @var{addr1}, @var{addr2}
7076 Find the next snapshot whose PC is outside the given range of
7079 @item tfind range @var{addr1}, @var{addr2}
7080 Find the next snapshot whose PC is between @var{addr1} and
7081 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
7083 @item tfind line @r{[}@var{file}:@r{]}@var{n}
7084 Find the next snapshot associated with the source line @var{n}. If
7085 the optional argument @var{file} is given, refer to line @var{n} in
7086 that source file. Search proceeds forward from the last examined
7087 trace snapshot. If no argument @var{n} is given, it means find the
7088 next line other than the one currently being examined; thus saying
7089 @code{tfind line} repeatedly can appear to have the same effect as
7090 stepping from line to line in a @emph{live} debugging session.
7093 The default arguments for the @code{tfind} commands are specifically
7094 designed to make it easy to scan through the trace buffer. For
7095 instance, @code{tfind} with no argument selects the next trace
7096 snapshot, and @code{tfind -} with no argument selects the previous
7097 trace snapshot. So, by giving one @code{tfind} command, and then
7098 simply hitting @key{RET} repeatedly you can examine all the trace
7099 snapshots in order. Or, by saying @code{tfind -} and then hitting
7100 @key{RET} repeatedly you can examine the snapshots in reverse order.
7101 The @code{tfind line} command with no argument selects the snapshot
7102 for the next source line executed. The @code{tfind pc} command with
7103 no argument selects the next snapshot with the same program counter
7104 (PC) as the current frame. The @code{tfind tracepoint} command with
7105 no argument selects the next trace snapshot collected by the same
7106 tracepoint as the current one.
7108 In addition to letting you scan through the trace buffer manually,
7109 these commands make it easy to construct @value{GDBN} scripts that
7110 scan through the trace buffer and print out whatever collected data
7111 you are interested in. Thus, if we want to examine the PC, FP, and SP
7112 registers from each trace frame in the buffer, we can say this:
7115 (@value{GDBP}) @b{tfind start}
7116 (@value{GDBP}) @b{while ($trace_frame != -1)}
7117 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
7118 $trace_frame, $pc, $sp, $fp
7122 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
7123 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
7124 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
7125 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
7126 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
7127 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
7128 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
7129 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
7130 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
7131 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
7132 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
7135 Or, if we want to examine the variable @code{X} at each source line in
7139 (@value{GDBP}) @b{tfind start}
7140 (@value{GDBP}) @b{while ($trace_frame != -1)}
7141 > printf "Frame %d, X == %d\n", $trace_frame, X
7151 @subsection @code{tdump}
7153 @cindex dump all data collected at tracepoint
7154 @cindex tracepoint data, display
7156 This command takes no arguments. It prints all the data collected at
7157 the current trace snapshot.
7160 (@value{GDBP}) @b{trace 444}
7161 (@value{GDBP}) @b{actions}
7162 Enter actions for tracepoint #2, one per line:
7163 > collect $regs, $locals, $args, gdb_long_test
7166 (@value{GDBP}) @b{tstart}
7168 (@value{GDBP}) @b{tfind line 444}
7169 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
7171 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
7173 (@value{GDBP}) @b{tdump}
7174 Data collected at tracepoint 2, trace frame 1:
7175 d0 0xc4aa0085 -995491707
7179 d4 0x71aea3d 119204413
7184 a1 0x3000668 50333288
7187 a4 0x3000698 50333336
7189 fp 0x30bf3c 0x30bf3c
7190 sp 0x30bf34 0x30bf34
7192 pc 0x20b2c8 0x20b2c8
7196 p = 0x20e5b4 "gdb-test"
7203 gdb_long_test = 17 '\021'
7208 @node save-tracepoints
7209 @subsection @code{save-tracepoints @var{filename}}
7210 @kindex save-tracepoints
7211 @cindex save tracepoints for future sessions
7213 This command saves all current tracepoint definitions together with
7214 their actions and passcounts, into a file @file{@var{filename}}
7215 suitable for use in a later debugging session. To read the saved
7216 tracepoint definitions, use the @code{source} command (@pxref{Command
7219 @node Tracepoint Variables
7220 @section Convenience Variables for Tracepoints
7221 @cindex tracepoint variables
7222 @cindex convenience variables for tracepoints
7225 @vindex $trace_frame
7226 @item (int) $trace_frame
7227 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
7228 snapshot is selected.
7231 @item (int) $tracepoint
7232 The tracepoint for the current trace snapshot.
7235 @item (int) $trace_line
7236 The line number for the current trace snapshot.
7239 @item (char []) $trace_file
7240 The source file for the current trace snapshot.
7243 @item (char []) $trace_func
7244 The name of the function containing @code{$tracepoint}.
7247 Note: @code{$trace_file} is not suitable for use in @code{printf},
7248 use @code{output} instead.
7250 Here's a simple example of using these convenience variables for
7251 stepping through all the trace snapshots and printing some of their
7255 (@value{GDBP}) @b{tfind start}
7257 (@value{GDBP}) @b{while $trace_frame != -1}
7258 > output $trace_file
7259 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
7265 @chapter Debugging Programs That Use Overlays
7268 If your program is too large to fit completely in your target system's
7269 memory, you can sometimes use @dfn{overlays} to work around this
7270 problem. @value{GDBN} provides some support for debugging programs that
7274 * How Overlays Work:: A general explanation of overlays.
7275 * Overlay Commands:: Managing overlays in @value{GDBN}.
7276 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
7277 mapped by asking the inferior.
7278 * Overlay Sample Program:: A sample program using overlays.
7281 @node How Overlays Work
7282 @section How Overlays Work
7283 @cindex mapped overlays
7284 @cindex unmapped overlays
7285 @cindex load address, overlay's
7286 @cindex mapped address
7287 @cindex overlay area
7289 Suppose you have a computer whose instruction address space is only 64
7290 kilobytes long, but which has much more memory which can be accessed by
7291 other means: special instructions, segment registers, or memory
7292 management hardware, for example. Suppose further that you want to
7293 adapt a program which is larger than 64 kilobytes to run on this system.
7295 One solution is to identify modules of your program which are relatively
7296 independent, and need not call each other directly; call these modules
7297 @dfn{overlays}. Separate the overlays from the main program, and place
7298 their machine code in the larger memory. Place your main program in
7299 instruction memory, but leave at least enough space there to hold the
7300 largest overlay as well.
7302 Now, to call a function located in an overlay, you must first copy that
7303 overlay's machine code from the large memory into the space set aside
7304 for it in the instruction memory, and then jump to its entry point
7307 @c NB: In the below the mapped area's size is greater or equal to the
7308 @c size of all overlays. This is intentional to remind the developer
7309 @c that overlays don't necessarily need to be the same size.
7313 Data Instruction Larger
7314 Address Space Address Space Address Space
7315 +-----------+ +-----------+ +-----------+
7317 +-----------+ +-----------+ +-----------+<-- overlay 1
7318 | program | | main | .----| overlay 1 | load address
7319 | variables | | program | | +-----------+
7320 | and heap | | | | | |
7321 +-----------+ | | | +-----------+<-- overlay 2
7322 | | +-----------+ | | | load address
7323 +-----------+ | | | .-| overlay 2 |
7325 mapped --->+-----------+ | | +-----------+
7327 | overlay | <-' | | |
7328 | area | <---' +-----------+<-- overlay 3
7329 | | <---. | | load address
7330 +-----------+ `--| overlay 3 |
7337 @anchor{A code overlay}A code overlay
7341 The diagram (@pxref{A code overlay}) shows a system with separate data
7342 and instruction address spaces. To map an overlay, the program copies
7343 its code from the larger address space to the instruction address space.
7344 Since the overlays shown here all use the same mapped address, only one
7345 may be mapped at a time. For a system with a single address space for
7346 data and instructions, the diagram would be similar, except that the
7347 program variables and heap would share an address space with the main
7348 program and the overlay area.
7350 An overlay loaded into instruction memory and ready for use is called a
7351 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
7352 instruction memory. An overlay not present (or only partially present)
7353 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
7354 is its address in the larger memory. The mapped address is also called
7355 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
7356 called the @dfn{load memory address}, or @dfn{LMA}.
7358 Unfortunately, overlays are not a completely transparent way to adapt a
7359 program to limited instruction memory. They introduce a new set of
7360 global constraints you must keep in mind as you design your program:
7365 Before calling or returning to a function in an overlay, your program
7366 must make sure that overlay is actually mapped. Otherwise, the call or
7367 return will transfer control to the right address, but in the wrong
7368 overlay, and your program will probably crash.
7371 If the process of mapping an overlay is expensive on your system, you
7372 will need to choose your overlays carefully to minimize their effect on
7373 your program's performance.
7376 The executable file you load onto your system must contain each
7377 overlay's instructions, appearing at the overlay's load address, not its
7378 mapped address. However, each overlay's instructions must be relocated
7379 and its symbols defined as if the overlay were at its mapped address.
7380 You can use GNU linker scripts to specify different load and relocation
7381 addresses for pieces of your program; see @ref{Overlay Description,,,
7382 ld.info, Using ld: the GNU linker}.
7385 The procedure for loading executable files onto your system must be able
7386 to load their contents into the larger address space as well as the
7387 instruction and data spaces.
7391 The overlay system described above is rather simple, and could be
7392 improved in many ways:
7397 If your system has suitable bank switch registers or memory management
7398 hardware, you could use those facilities to make an overlay's load area
7399 contents simply appear at their mapped address in instruction space.
7400 This would probably be faster than copying the overlay to its mapped
7401 area in the usual way.
7404 If your overlays are small enough, you could set aside more than one
7405 overlay area, and have more than one overlay mapped at a time.
7408 You can use overlays to manage data, as well as instructions. In
7409 general, data overlays are even less transparent to your design than
7410 code overlays: whereas code overlays only require care when you call or
7411 return to functions, data overlays require care every time you access
7412 the data. Also, if you change the contents of a data overlay, you
7413 must copy its contents back out to its load address before you can copy a
7414 different data overlay into the same mapped area.
7419 @node Overlay Commands
7420 @section Overlay Commands
7422 To use @value{GDBN}'s overlay support, each overlay in your program must
7423 correspond to a separate section of the executable file. The section's
7424 virtual memory address and load memory address must be the overlay's
7425 mapped and load addresses. Identifying overlays with sections allows
7426 @value{GDBN} to determine the appropriate address of a function or
7427 variable, depending on whether the overlay is mapped or not.
7429 @value{GDBN}'s overlay commands all start with the word @code{overlay};
7430 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
7435 Disable @value{GDBN}'s overlay support. When overlay support is
7436 disabled, @value{GDBN} assumes that all functions and variables are
7437 always present at their mapped addresses. By default, @value{GDBN}'s
7438 overlay support is disabled.
7440 @item overlay manual
7441 @cindex manual overlay debugging
7442 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
7443 relies on you to tell it which overlays are mapped, and which are not,
7444 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
7445 commands described below.
7447 @item overlay map-overlay @var{overlay}
7448 @itemx overlay map @var{overlay}
7449 @cindex map an overlay
7450 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
7451 be the name of the object file section containing the overlay. When an
7452 overlay is mapped, @value{GDBN} assumes it can find the overlay's
7453 functions and variables at their mapped addresses. @value{GDBN} assumes
7454 that any other overlays whose mapped ranges overlap that of
7455 @var{overlay} are now unmapped.
7457 @item overlay unmap-overlay @var{overlay}
7458 @itemx overlay unmap @var{overlay}
7459 @cindex unmap an overlay
7460 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
7461 must be the name of the object file section containing the overlay.
7462 When an overlay is unmapped, @value{GDBN} assumes it can find the
7463 overlay's functions and variables at their load addresses.
7466 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
7467 consults a data structure the overlay manager maintains in the inferior
7468 to see which overlays are mapped. For details, see @ref{Automatic
7471 @item overlay load-target
7473 @cindex reloading the overlay table
7474 Re-read the overlay table from the inferior. Normally, @value{GDBN}
7475 re-reads the table @value{GDBN} automatically each time the inferior
7476 stops, so this command should only be necessary if you have changed the
7477 overlay mapping yourself using @value{GDBN}. This command is only
7478 useful when using automatic overlay debugging.
7480 @item overlay list-overlays
7482 @cindex listing mapped overlays
7483 Display a list of the overlays currently mapped, along with their mapped
7484 addresses, load addresses, and sizes.
7488 Normally, when @value{GDBN} prints a code address, it includes the name
7489 of the function the address falls in:
7492 (@value{GDBP}) print main
7493 $3 = @{int ()@} 0x11a0 <main>
7496 When overlay debugging is enabled, @value{GDBN} recognizes code in
7497 unmapped overlays, and prints the names of unmapped functions with
7498 asterisks around them. For example, if @code{foo} is a function in an
7499 unmapped overlay, @value{GDBN} prints it this way:
7502 (@value{GDBP}) overlay list
7503 No sections are mapped.
7504 (@value{GDBP}) print foo
7505 $5 = @{int (int)@} 0x100000 <*foo*>
7508 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
7512 (@value{GDBP}) overlay list
7513 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
7514 mapped at 0x1016 - 0x104a
7515 (@value{GDBP}) print foo
7516 $6 = @{int (int)@} 0x1016 <foo>
7519 When overlay debugging is enabled, @value{GDBN} can find the correct
7520 address for functions and variables in an overlay, whether or not the
7521 overlay is mapped. This allows most @value{GDBN} commands, like
7522 @code{break} and @code{disassemble}, to work normally, even on unmapped
7523 code. However, @value{GDBN}'s breakpoint support has some limitations:
7527 @cindex breakpoints in overlays
7528 @cindex overlays, setting breakpoints in
7529 You can set breakpoints in functions in unmapped overlays, as long as
7530 @value{GDBN} can write to the overlay at its load address.
7532 @value{GDBN} can not set hardware or simulator-based breakpoints in
7533 unmapped overlays. However, if you set a breakpoint at the end of your
7534 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
7535 you are using manual overlay management), @value{GDBN} will re-set its
7536 breakpoints properly.
7540 @node Automatic Overlay Debugging
7541 @section Automatic Overlay Debugging
7542 @cindex automatic overlay debugging
7544 @value{GDBN} can automatically track which overlays are mapped and which
7545 are not, given some simple co-operation from the overlay manager in the
7546 inferior. If you enable automatic overlay debugging with the
7547 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
7548 looks in the inferior's memory for certain variables describing the
7549 current state of the overlays.
7551 Here are the variables your overlay manager must define to support
7552 @value{GDBN}'s automatic overlay debugging:
7556 @item @code{_ovly_table}:
7557 This variable must be an array of the following structures:
7562 /* The overlay's mapped address. */
7565 /* The size of the overlay, in bytes. */
7568 /* The overlay's load address. */
7571 /* Non-zero if the overlay is currently mapped;
7573 unsigned long mapped;
7577 @item @code{_novlys}:
7578 This variable must be a four-byte signed integer, holding the total
7579 number of elements in @code{_ovly_table}.
7583 To decide whether a particular overlay is mapped or not, @value{GDBN}
7584 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
7585 @code{lma} members equal the VMA and LMA of the overlay's section in the
7586 executable file. When @value{GDBN} finds a matching entry, it consults
7587 the entry's @code{mapped} member to determine whether the overlay is
7590 In addition, your overlay manager may define a function called
7591 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
7592 will silently set a breakpoint there. If the overlay manager then
7593 calls this function whenever it has changed the overlay table, this
7594 will enable @value{GDBN} to accurately keep track of which overlays
7595 are in program memory, and update any breakpoints that may be set
7596 in overlays. This will allow breakpoints to work even if the
7597 overlays are kept in ROM or other non-writable memory while they
7598 are not being executed.
7600 @node Overlay Sample Program
7601 @section Overlay Sample Program
7602 @cindex overlay example program
7604 When linking a program which uses overlays, you must place the overlays
7605 at their load addresses, while relocating them to run at their mapped
7606 addresses. To do this, you must write a linker script (@pxref{Overlay
7607 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
7608 since linker scripts are specific to a particular host system, target
7609 architecture, and target memory layout, this manual cannot provide
7610 portable sample code demonstrating @value{GDBN}'s overlay support.
7612 However, the @value{GDBN} source distribution does contain an overlaid
7613 program, with linker scripts for a few systems, as part of its test
7614 suite. The program consists of the following files from
7615 @file{gdb/testsuite/gdb.base}:
7619 The main program file.
7621 A simple overlay manager, used by @file{overlays.c}.
7626 Overlay modules, loaded and used by @file{overlays.c}.
7629 Linker scripts for linking the test program on the @code{d10v-elf}
7630 and @code{m32r-elf} targets.
7633 You can build the test program using the @code{d10v-elf} GCC
7634 cross-compiler like this:
7637 $ d10v-elf-gcc -g -c overlays.c
7638 $ d10v-elf-gcc -g -c ovlymgr.c
7639 $ d10v-elf-gcc -g -c foo.c
7640 $ d10v-elf-gcc -g -c bar.c
7641 $ d10v-elf-gcc -g -c baz.c
7642 $ d10v-elf-gcc -g -c grbx.c
7643 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
7644 baz.o grbx.o -Wl,-Td10v.ld -o overlays
7647 The build process is identical for any other architecture, except that
7648 you must substitute the appropriate compiler and linker script for the
7649 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
7653 @chapter Using @value{GDBN} with Different Languages
7656 Although programming languages generally have common aspects, they are
7657 rarely expressed in the same manner. For instance, in ANSI C,
7658 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
7659 Modula-2, it is accomplished by @code{p^}. Values can also be
7660 represented (and displayed) differently. Hex numbers in C appear as
7661 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
7663 @cindex working language
7664 Language-specific information is built into @value{GDBN} for some languages,
7665 allowing you to express operations like the above in your program's
7666 native language, and allowing @value{GDBN} to output values in a manner
7667 consistent with the syntax of your program's native language. The
7668 language you use to build expressions is called the @dfn{working
7672 * Setting:: Switching between source languages
7673 * Show:: Displaying the language
7674 * Checks:: Type and range checks
7675 * Support:: Supported languages
7676 * Unsupported languages:: Unsupported languages
7680 @section Switching between source languages
7682 There are two ways to control the working language---either have @value{GDBN}
7683 set it automatically, or select it manually yourself. You can use the
7684 @code{set language} command for either purpose. On startup, @value{GDBN}
7685 defaults to setting the language automatically. The working language is
7686 used to determine how expressions you type are interpreted, how values
7689 In addition to the working language, every source file that
7690 @value{GDBN} knows about has its own working language. For some object
7691 file formats, the compiler might indicate which language a particular
7692 source file is in. However, most of the time @value{GDBN} infers the
7693 language from the name of the file. The language of a source file
7694 controls whether C@t{++} names are demangled---this way @code{backtrace} can
7695 show each frame appropriately for its own language. There is no way to
7696 set the language of a source file from within @value{GDBN}, but you can
7697 set the language associated with a filename extension. @xref{Show, ,
7698 Displaying the language}.
7700 This is most commonly a problem when you use a program, such
7701 as @code{cfront} or @code{f2c}, that generates C but is written in
7702 another language. In that case, make the
7703 program use @code{#line} directives in its C output; that way
7704 @value{GDBN} will know the correct language of the source code of the original
7705 program, and will display that source code, not the generated C code.
7708 * Filenames:: Filename extensions and languages.
7709 * Manually:: Setting the working language manually
7710 * Automatically:: Having @value{GDBN} infer the source language
7714 @subsection List of filename extensions and languages
7716 If a source file name ends in one of the following extensions, then
7717 @value{GDBN} infers that its language is the one indicated.
7738 Objective-C source file
7745 Modula-2 source file
7749 Assembler source file. This actually behaves almost like C, but
7750 @value{GDBN} does not skip over function prologues when stepping.
7753 In addition, you may set the language associated with a filename
7754 extension. @xref{Show, , Displaying the language}.
7757 @subsection Setting the working language
7759 If you allow @value{GDBN} to set the language automatically,
7760 expressions are interpreted the same way in your debugging session and
7763 @kindex set language
7764 If you wish, you may set the language manually. To do this, issue the
7765 command @samp{set language @var{lang}}, where @var{lang} is the name of
7767 @code{c} or @code{modula-2}.
7768 For a list of the supported languages, type @samp{set language}.
7770 Setting the language manually prevents @value{GDBN} from updating the working
7771 language automatically. This can lead to confusion if you try
7772 to debug a program when the working language is not the same as the
7773 source language, when an expression is acceptable to both
7774 languages---but means different things. For instance, if the current
7775 source file were written in C, and @value{GDBN} was parsing Modula-2, a
7783 might not have the effect you intended. In C, this means to add
7784 @code{b} and @code{c} and place the result in @code{a}. The result
7785 printed would be the value of @code{a}. In Modula-2, this means to compare
7786 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
7789 @subsection Having @value{GDBN} infer the source language
7791 To have @value{GDBN} set the working language automatically, use
7792 @samp{set language local} or @samp{set language auto}. @value{GDBN}
7793 then infers the working language. That is, when your program stops in a
7794 frame (usually by encountering a breakpoint), @value{GDBN} sets the
7795 working language to the language recorded for the function in that
7796 frame. If the language for a frame is unknown (that is, if the function
7797 or block corresponding to the frame was defined in a source file that
7798 does not have a recognized extension), the current working language is
7799 not changed, and @value{GDBN} issues a warning.
7801 This may not seem necessary for most programs, which are written
7802 entirely in one source language. However, program modules and libraries
7803 written in one source language can be used by a main program written in
7804 a different source language. Using @samp{set language auto} in this
7805 case frees you from having to set the working language manually.
7808 @section Displaying the language
7810 The following commands help you find out which language is the
7811 working language, and also what language source files were written in.
7813 @kindex show language
7816 Display the current working language. This is the
7817 language you can use with commands such as @code{print} to
7818 build and compute expressions that may involve variables in your program.
7821 @kindex info frame@r{, show the source language}
7822 Display the source language for this frame. This language becomes the
7823 working language if you use an identifier from this frame.
7824 @xref{Frame Info, ,Information about a frame}, to identify the other
7825 information listed here.
7828 @kindex info source@r{, show the source language}
7829 Display the source language of this source file.
7830 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
7831 information listed here.
7834 In unusual circumstances, you may have source files with extensions
7835 not in the standard list. You can then set the extension associated
7836 with a language explicitly:
7838 @kindex set extension-language
7839 @kindex info extensions
7841 @item set extension-language @var{.ext} @var{language}
7842 Set source files with extension @var{.ext} to be assumed to be in
7843 the source language @var{language}.
7845 @item info extensions
7846 List all the filename extensions and the associated languages.
7850 @section Type and range checking
7853 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
7854 checking are included, but they do not yet have any effect. This
7855 section documents the intended facilities.
7857 @c FIXME remove warning when type/range code added
7859 Some languages are designed to guard you against making seemingly common
7860 errors through a series of compile- and run-time checks. These include
7861 checking the type of arguments to functions and operators, and making
7862 sure mathematical overflows are caught at run time. Checks such as
7863 these help to ensure a program's correctness once it has been compiled
7864 by eliminating type mismatches, and providing active checks for range
7865 errors when your program is running.
7867 @value{GDBN} can check for conditions like the above if you wish.
7868 Although @value{GDBN} does not check the statements in your program, it
7869 can check expressions entered directly into @value{GDBN} for evaluation via
7870 the @code{print} command, for example. As with the working language,
7871 @value{GDBN} can also decide whether or not to check automatically based on
7872 your program's source language. @xref{Support, ,Supported languages},
7873 for the default settings of supported languages.
7876 * Type Checking:: An overview of type checking
7877 * Range Checking:: An overview of range checking
7880 @cindex type checking
7881 @cindex checks, type
7883 @subsection An overview of type checking
7885 Some languages, such as Modula-2, are strongly typed, meaning that the
7886 arguments to operators and functions have to be of the correct type,
7887 otherwise an error occurs. These checks prevent type mismatch
7888 errors from ever causing any run-time problems. For example,
7896 The second example fails because the @code{CARDINAL} 1 is not
7897 type-compatible with the @code{REAL} 2.3.
7899 For the expressions you use in @value{GDBN} commands, you can tell the
7900 @value{GDBN} type checker to skip checking;
7901 to treat any mismatches as errors and abandon the expression;
7902 or to only issue warnings when type mismatches occur,
7903 but evaluate the expression anyway. When you choose the last of
7904 these, @value{GDBN} evaluates expressions like the second example above, but
7905 also issues a warning.
7907 Even if you turn type checking off, there may be other reasons
7908 related to type that prevent @value{GDBN} from evaluating an expression.
7909 For instance, @value{GDBN} does not know how to add an @code{int} and
7910 a @code{struct foo}. These particular type errors have nothing to do
7911 with the language in use, and usually arise from expressions, such as
7912 the one described above, which make little sense to evaluate anyway.
7914 Each language defines to what degree it is strict about type. For
7915 instance, both Modula-2 and C require the arguments to arithmetical
7916 operators to be numbers. In C, enumerated types and pointers can be
7917 represented as numbers, so that they are valid arguments to mathematical
7918 operators. @xref{Support, ,Supported languages}, for further
7919 details on specific languages.
7921 @value{GDBN} provides some additional commands for controlling the type checker:
7923 @kindex set check type
7924 @kindex show check type
7926 @item set check type auto
7927 Set type checking on or off based on the current working language.
7928 @xref{Support, ,Supported languages}, for the default settings for
7931 @item set check type on
7932 @itemx set check type off
7933 Set type checking on or off, overriding the default setting for the
7934 current working language. Issue a warning if the setting does not
7935 match the language default. If any type mismatches occur in
7936 evaluating an expression while type checking is on, @value{GDBN} prints a
7937 message and aborts evaluation of the expression.
7939 @item set check type warn
7940 Cause the type checker to issue warnings, but to always attempt to
7941 evaluate the expression. Evaluating the expression may still
7942 be impossible for other reasons. For example, @value{GDBN} cannot add
7943 numbers and structures.
7946 Show the current setting of the type checker, and whether or not @value{GDBN}
7947 is setting it automatically.
7950 @cindex range checking
7951 @cindex checks, range
7952 @node Range Checking
7953 @subsection An overview of range checking
7955 In some languages (such as Modula-2), it is an error to exceed the
7956 bounds of a type; this is enforced with run-time checks. Such range
7957 checking is meant to ensure program correctness by making sure
7958 computations do not overflow, or indices on an array element access do
7959 not exceed the bounds of the array.
7961 For expressions you use in @value{GDBN} commands, you can tell
7962 @value{GDBN} to treat range errors in one of three ways: ignore them,
7963 always treat them as errors and abandon the expression, or issue
7964 warnings but evaluate the expression anyway.
7966 A range error can result from numerical overflow, from exceeding an
7967 array index bound, or when you type a constant that is not a member
7968 of any type. Some languages, however, do not treat overflows as an
7969 error. In many implementations of C, mathematical overflow causes the
7970 result to ``wrap around'' to lower values---for example, if @var{m} is
7971 the largest integer value, and @var{s} is the smallest, then
7974 @var{m} + 1 @result{} @var{s}
7977 This, too, is specific to individual languages, and in some cases
7978 specific to individual compilers or machines. @xref{Support, ,
7979 Supported languages}, for further details on specific languages.
7981 @value{GDBN} provides some additional commands for controlling the range checker:
7983 @kindex set check range
7984 @kindex show check range
7986 @item set check range auto
7987 Set range checking on or off based on the current working language.
7988 @xref{Support, ,Supported languages}, for the default settings for
7991 @item set check range on
7992 @itemx set check range off
7993 Set range checking on or off, overriding the default setting for the
7994 current working language. A warning is issued if the setting does not
7995 match the language default. If a range error occurs and range checking is on,
7996 then a message is printed and evaluation of the expression is aborted.
7998 @item set check range warn
7999 Output messages when the @value{GDBN} range checker detects a range error,
8000 but attempt to evaluate the expression anyway. Evaluating the
8001 expression may still be impossible for other reasons, such as accessing
8002 memory that the process does not own (a typical example from many Unix
8006 Show the current setting of the range checker, and whether or not it is
8007 being set automatically by @value{GDBN}.
8011 @section Supported languages
8013 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, assembly, Modula-2, and Ada.
8014 @c This is false ...
8015 Some @value{GDBN} features may be used in expressions regardless of the
8016 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
8017 and the @samp{@{type@}addr} construct (@pxref{Expressions,
8018 ,Expressions}) can be used with the constructs of any supported
8021 The following sections detail to what degree each source language is
8022 supported by @value{GDBN}. These sections are not meant to be language
8023 tutorials or references, but serve only as a reference guide to what the
8024 @value{GDBN} expression parser accepts, and what input and output
8025 formats should look like for different languages. There are many good
8026 books written on each of these languages; please look to these for a
8027 language reference or tutorial.
8031 * Objective-C:: Objective-C
8032 * Modula-2:: Modula-2
8037 @subsection C and C@t{++}
8039 @cindex C and C@t{++}
8040 @cindex expressions in C or C@t{++}
8042 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
8043 to both languages. Whenever this is the case, we discuss those languages
8047 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
8048 @cindex @sc{gnu} C@t{++}
8049 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
8050 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
8051 effectively, you must compile your C@t{++} programs with a supported
8052 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
8053 compiler (@code{aCC}).
8055 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
8056 format; if it doesn't work on your system, try the stabs+ debugging
8057 format. You can select those formats explicitly with the @code{g++}
8058 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
8059 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
8060 CC, gcc.info, Using @sc{gnu} CC}.
8063 * C Operators:: C and C@t{++} operators
8064 * C Constants:: C and C@t{++} constants
8065 * C plus plus expressions:: C@t{++} expressions
8066 * C Defaults:: Default settings for C and C@t{++}
8067 * C Checks:: C and C@t{++} type and range checks
8068 * Debugging C:: @value{GDBN} and C
8069 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
8073 @subsubsection C and C@t{++} operators
8075 @cindex C and C@t{++} operators
8077 Operators must be defined on values of specific types. For instance,
8078 @code{+} is defined on numbers, but not on structures. Operators are
8079 often defined on groups of types.
8081 For the purposes of C and C@t{++}, the following definitions hold:
8086 @emph{Integral types} include @code{int} with any of its storage-class
8087 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
8090 @emph{Floating-point types} include @code{float}, @code{double}, and
8091 @code{long double} (if supported by the target platform).
8094 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
8097 @emph{Scalar types} include all of the above.
8102 The following operators are supported. They are listed here
8103 in order of increasing precedence:
8107 The comma or sequencing operator. Expressions in a comma-separated list
8108 are evaluated from left to right, with the result of the entire
8109 expression being the last expression evaluated.
8112 Assignment. The value of an assignment expression is the value
8113 assigned. Defined on scalar types.
8116 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
8117 and translated to @w{@code{@var{a} = @var{a op b}}}.
8118 @w{@code{@var{op}=}} and @code{=} have the same precedence.
8119 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
8120 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
8123 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
8124 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
8128 Logical @sc{or}. Defined on integral types.
8131 Logical @sc{and}. Defined on integral types.
8134 Bitwise @sc{or}. Defined on integral types.
8137 Bitwise exclusive-@sc{or}. Defined on integral types.
8140 Bitwise @sc{and}. Defined on integral types.
8143 Equality and inequality. Defined on scalar types. The value of these
8144 expressions is 0 for false and non-zero for true.
8146 @item <@r{, }>@r{, }<=@r{, }>=
8147 Less than, greater than, less than or equal, greater than or equal.
8148 Defined on scalar types. The value of these expressions is 0 for false
8149 and non-zero for true.
8152 left shift, and right shift. Defined on integral types.
8155 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8158 Addition and subtraction. Defined on integral types, floating-point types and
8161 @item *@r{, }/@r{, }%
8162 Multiplication, division, and modulus. Multiplication and division are
8163 defined on integral and floating-point types. Modulus is defined on
8167 Increment and decrement. When appearing before a variable, the
8168 operation is performed before the variable is used in an expression;
8169 when appearing after it, the variable's value is used before the
8170 operation takes place.
8173 Pointer dereferencing. Defined on pointer types. Same precedence as
8177 Address operator. Defined on variables. Same precedence as @code{++}.
8179 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
8180 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
8181 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
8182 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
8186 Negative. Defined on integral and floating-point types. Same
8187 precedence as @code{++}.
8190 Logical negation. Defined on integral types. Same precedence as
8194 Bitwise complement operator. Defined on integral types. Same precedence as
8199 Structure member, and pointer-to-structure member. For convenience,
8200 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
8201 pointer based on the stored type information.
8202 Defined on @code{struct} and @code{union} data.
8205 Dereferences of pointers to members.
8208 Array indexing. @code{@var{a}[@var{i}]} is defined as
8209 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
8212 Function parameter list. Same precedence as @code{->}.
8215 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
8216 and @code{class} types.
8219 Doubled colons also represent the @value{GDBN} scope operator
8220 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
8224 If an operator is redefined in the user code, @value{GDBN} usually
8225 attempts to invoke the redefined version instead of using the operator's
8233 @subsubsection C and C@t{++} constants
8235 @cindex C and C@t{++} constants
8237 @value{GDBN} allows you to express the constants of C and C@t{++} in the
8242 Integer constants are a sequence of digits. Octal constants are
8243 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
8244 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
8245 @samp{l}, specifying that the constant should be treated as a
8249 Floating point constants are a sequence of digits, followed by a decimal
8250 point, followed by a sequence of digits, and optionally followed by an
8251 exponent. An exponent is of the form:
8252 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
8253 sequence of digits. The @samp{+} is optional for positive exponents.
8254 A floating-point constant may also end with a letter @samp{f} or
8255 @samp{F}, specifying that the constant should be treated as being of
8256 the @code{float} (as opposed to the default @code{double}) type; or with
8257 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
8261 Enumerated constants consist of enumerated identifiers, or their
8262 integral equivalents.
8265 Character constants are a single character surrounded by single quotes
8266 (@code{'}), or a number---the ordinal value of the corresponding character
8267 (usually its @sc{ascii} value). Within quotes, the single character may
8268 be represented by a letter or by @dfn{escape sequences}, which are of
8269 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
8270 of the character's ordinal value; or of the form @samp{\@var{x}}, where
8271 @samp{@var{x}} is a predefined special character---for example,
8272 @samp{\n} for newline.
8275 String constants are a sequence of character constants surrounded by
8276 double quotes (@code{"}). Any valid character constant (as described
8277 above) may appear. Double quotes within the string must be preceded by
8278 a backslash, so for instance @samp{"a\"b'c"} is a string of five
8282 Pointer constants are an integral value. You can also write pointers
8283 to constants using the C operator @samp{&}.
8286 Array constants are comma-separated lists surrounded by braces @samp{@{}
8287 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
8288 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
8289 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
8293 * C plus plus expressions::
8300 @node C plus plus expressions
8301 @subsubsection C@t{++} expressions
8303 @cindex expressions in C@t{++}
8304 @value{GDBN} expression handling can interpret most C@t{++} expressions.
8306 @cindex debugging C@t{++} programs
8307 @cindex C@t{++} compilers
8308 @cindex debug formats and C@t{++}
8309 @cindex @value{NGCC} and C@t{++}
8311 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
8312 proper compiler and the proper debug format. Currently, @value{GDBN}
8313 works best when debugging C@t{++} code that is compiled with
8314 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
8315 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
8316 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
8317 stabs+ as their default debug format, so you usually don't need to
8318 specify a debug format explicitly. Other compilers and/or debug formats
8319 are likely to work badly or not at all when using @value{GDBN} to debug
8325 @cindex member functions
8327 Member function calls are allowed; you can use expressions like
8330 count = aml->GetOriginal(x, y)
8333 @vindex this@r{, inside C@t{++} member functions}
8334 @cindex namespace in C@t{++}
8336 While a member function is active (in the selected stack frame), your
8337 expressions have the same namespace available as the member function;
8338 that is, @value{GDBN} allows implicit references to the class instance
8339 pointer @code{this} following the same rules as C@t{++}.
8341 @cindex call overloaded functions
8342 @cindex overloaded functions, calling
8343 @cindex type conversions in C@t{++}
8345 You can call overloaded functions; @value{GDBN} resolves the function
8346 call to the right definition, with some restrictions. @value{GDBN} does not
8347 perform overload resolution involving user-defined type conversions,
8348 calls to constructors, or instantiations of templates that do not exist
8349 in the program. It also cannot handle ellipsis argument lists or
8352 It does perform integral conversions and promotions, floating-point
8353 promotions, arithmetic conversions, pointer conversions, conversions of
8354 class objects to base classes, and standard conversions such as those of
8355 functions or arrays to pointers; it requires an exact match on the
8356 number of function arguments.
8358 Overload resolution is always performed, unless you have specified
8359 @code{set overload-resolution off}. @xref{Debugging C plus plus,
8360 ,@value{GDBN} features for C@t{++}}.
8362 You must specify @code{set overload-resolution off} in order to use an
8363 explicit function signature to call an overloaded function, as in
8365 p 'foo(char,int)'('x', 13)
8368 The @value{GDBN} command-completion facility can simplify this;
8369 see @ref{Completion, ,Command completion}.
8371 @cindex reference declarations
8373 @value{GDBN} understands variables declared as C@t{++} references; you can use
8374 them in expressions just as you do in C@t{++} source---they are automatically
8377 In the parameter list shown when @value{GDBN} displays a frame, the values of
8378 reference variables are not displayed (unlike other variables); this
8379 avoids clutter, since references are often used for large structures.
8380 The @emph{address} of a reference variable is always shown, unless
8381 you have specified @samp{set print address off}.
8384 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
8385 expressions can use it just as expressions in your program do. Since
8386 one scope may be defined in another, you can use @code{::} repeatedly if
8387 necessary, for example in an expression like
8388 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
8389 resolving name scope by reference to source files, in both C and C@t{++}
8390 debugging (@pxref{Variables, ,Program variables}).
8393 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
8394 calling virtual functions correctly, printing out virtual bases of
8395 objects, calling functions in a base subobject, casting objects, and
8396 invoking user-defined operators.
8399 @subsubsection C and C@t{++} defaults
8401 @cindex C and C@t{++} defaults
8403 If you allow @value{GDBN} to set type and range checking automatically, they
8404 both default to @code{off} whenever the working language changes to
8405 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
8406 selects the working language.
8408 If you allow @value{GDBN} to set the language automatically, it
8409 recognizes source files whose names end with @file{.c}, @file{.C}, or
8410 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
8411 these files, it sets the working language to C or C@t{++}.
8412 @xref{Automatically, ,Having @value{GDBN} infer the source language},
8413 for further details.
8415 @c Type checking is (a) primarily motivated by Modula-2, and (b)
8416 @c unimplemented. If (b) changes, it might make sense to let this node
8417 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
8420 @subsubsection C and C@t{++} type and range checks
8422 @cindex C and C@t{++} checks
8424 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
8425 is not used. However, if you turn type checking on, @value{GDBN}
8426 considers two variables type equivalent if:
8430 The two variables are structured and have the same structure, union, or
8434 The two variables have the same type name, or types that have been
8435 declared equivalent through @code{typedef}.
8438 @c leaving this out because neither J Gilmore nor R Pesch understand it.
8441 The two @code{struct}, @code{union}, or @code{enum} variables are
8442 declared in the same declaration. (Note: this may not be true for all C
8447 Range checking, if turned on, is done on mathematical operations. Array
8448 indices are not checked, since they are often used to index a pointer
8449 that is not itself an array.
8452 @subsubsection @value{GDBN} and C
8454 The @code{set print union} and @code{show print union} commands apply to
8455 the @code{union} type. When set to @samp{on}, any @code{union} that is
8456 inside a @code{struct} or @code{class} is also printed. Otherwise, it
8457 appears as @samp{@{...@}}.
8459 The @code{@@} operator aids in the debugging of dynamic arrays, formed
8460 with pointers and a memory allocation function. @xref{Expressions,
8464 * Debugging C plus plus::
8467 @node Debugging C plus plus
8468 @subsubsection @value{GDBN} features for C@t{++}
8470 @cindex commands for C@t{++}
8472 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
8473 designed specifically for use with C@t{++}. Here is a summary:
8476 @cindex break in overloaded functions
8477 @item @r{breakpoint menus}
8478 When you want a breakpoint in a function whose name is overloaded,
8479 @value{GDBN} breakpoint menus help you specify which function definition
8480 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
8482 @cindex overloading in C@t{++}
8483 @item rbreak @var{regex}
8484 Setting breakpoints using regular expressions is helpful for setting
8485 breakpoints on overloaded functions that are not members of any special
8487 @xref{Set Breaks, ,Setting breakpoints}.
8489 @cindex C@t{++} exception handling
8492 Debug C@t{++} exception handling using these commands. @xref{Set
8493 Catchpoints, , Setting catchpoints}.
8496 @item ptype @var{typename}
8497 Print inheritance relationships as well as other information for type
8499 @xref{Symbols, ,Examining the Symbol Table}.
8501 @cindex C@t{++} symbol display
8502 @item set print demangle
8503 @itemx show print demangle
8504 @itemx set print asm-demangle
8505 @itemx show print asm-demangle
8506 Control whether C@t{++} symbols display in their source form, both when
8507 displaying code as C@t{++} source and when displaying disassemblies.
8508 @xref{Print Settings, ,Print settings}.
8510 @item set print object
8511 @itemx show print object
8512 Choose whether to print derived (actual) or declared types of objects.
8513 @xref{Print Settings, ,Print settings}.
8515 @item set print vtbl
8516 @itemx show print vtbl
8517 Control the format for printing virtual function tables.
8518 @xref{Print Settings, ,Print settings}.
8519 (The @code{vtbl} commands do not work on programs compiled with the HP
8520 ANSI C@t{++} compiler (@code{aCC}).)
8522 @kindex set overload-resolution
8523 @cindex overloaded functions, overload resolution
8524 @item set overload-resolution on
8525 Enable overload resolution for C@t{++} expression evaluation. The default
8526 is on. For overloaded functions, @value{GDBN} evaluates the arguments
8527 and searches for a function whose signature matches the argument types,
8528 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
8529 expressions}, for details). If it cannot find a match, it emits a
8532 @item set overload-resolution off
8533 Disable overload resolution for C@t{++} expression evaluation. For
8534 overloaded functions that are not class member functions, @value{GDBN}
8535 chooses the first function of the specified name that it finds in the
8536 symbol table, whether or not its arguments are of the correct type. For
8537 overloaded functions that are class member functions, @value{GDBN}
8538 searches for a function whose signature @emph{exactly} matches the
8541 @item @r{Overloaded symbol names}
8542 You can specify a particular definition of an overloaded symbol, using
8543 the same notation that is used to declare such symbols in C@t{++}: type
8544 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
8545 also use the @value{GDBN} command-line word completion facilities to list the
8546 available choices, or to finish the type list for you.
8547 @xref{Completion,, Command completion}, for details on how to do this.
8551 @subsection Objective-C
8554 This section provides information about some commands and command
8555 options that are useful for debugging Objective-C code.
8558 * Method Names in Commands::
8559 * The Print Command with Objective-C::
8562 @node Method Names in Commands, The Print Command with Objective-C, Objective-C, Objective-C
8563 @subsubsection Method Names in Commands
8565 The following commands have been extended to accept Objective-C method
8566 names as line specifications:
8568 @kindex clear@r{, and Objective-C}
8569 @kindex break@r{, and Objective-C}
8570 @kindex info line@r{, and Objective-C}
8571 @kindex jump@r{, and Objective-C}
8572 @kindex list@r{, and Objective-C}
8576 @item @code{info line}
8581 A fully qualified Objective-C method name is specified as
8584 -[@var{Class} @var{methodName}]
8587 where the minus sign is used to indicate an instance method and a
8588 plus sign (not shown) is used to indicate a class method. The class
8589 name @var{Class} and method name @var{methodName} are enclosed in
8590 brackets, similar to the way messages are specified in Objective-C
8591 source code. For example, to set a breakpoint at the @code{create}
8592 instance method of class @code{Fruit} in the program currently being
8596 break -[Fruit create]
8599 To list ten program lines around the @code{initialize} class method,
8603 list +[NSText initialize]
8606 In the current version of @value{GDBN}, the plus or minus sign is
8607 required. In future versions of @value{GDBN}, the plus or minus
8608 sign will be optional, but you can use it to narrow the search. It
8609 is also possible to specify just a method name:
8615 You must specify the complete method name, including any colons. If
8616 your program's source files contain more than one @code{create} method,
8617 you'll be presented with a numbered list of classes that implement that
8618 method. Indicate your choice by number, or type @samp{0} to exit if
8621 As another example, to clear a breakpoint established at the
8622 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
8625 clear -[NSWindow makeKeyAndOrderFront:]
8628 @node The Print Command with Objective-C
8629 @subsubsection The Print Command With Objective-C
8630 @kindex print-object
8631 @kindex po @r{(@code{print-object})}
8633 The print command has also been extended to accept methods. For example:
8636 print -[@var{object} hash]
8639 @cindex print an Objective-C object description
8640 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
8642 will tell @value{GDBN} to send the @code{hash} message to @var{object}
8643 and print the result. Also, an additional command has been added,
8644 @code{print-object} or @code{po} for short, which is meant to print
8645 the description of an object. However, this command may only work
8646 with certain Objective-C libraries that have a particular hook
8647 function, @code{_NSPrintForDebugger}, defined.
8649 @node Modula-2, Ada, Objective-C, Support
8650 @subsection Modula-2
8652 @cindex Modula-2, @value{GDBN} support
8654 The extensions made to @value{GDBN} to support Modula-2 only support
8655 output from the @sc{gnu} Modula-2 compiler (which is currently being
8656 developed). Other Modula-2 compilers are not currently supported, and
8657 attempting to debug executables produced by them is most likely
8658 to give an error as @value{GDBN} reads in the executable's symbol
8661 @cindex expressions in Modula-2
8663 * M2 Operators:: Built-in operators
8664 * Built-In Func/Proc:: Built-in functions and procedures
8665 * M2 Constants:: Modula-2 constants
8666 * M2 Defaults:: Default settings for Modula-2
8667 * Deviations:: Deviations from standard Modula-2
8668 * M2 Checks:: Modula-2 type and range checks
8669 * M2 Scope:: The scope operators @code{::} and @code{.}
8670 * GDB/M2:: @value{GDBN} and Modula-2
8674 @subsubsection Operators
8675 @cindex Modula-2 operators
8677 Operators must be defined on values of specific types. For instance,
8678 @code{+} is defined on numbers, but not on structures. Operators are
8679 often defined on groups of types. For the purposes of Modula-2, the
8680 following definitions hold:
8685 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
8689 @emph{Character types} consist of @code{CHAR} and its subranges.
8692 @emph{Floating-point types} consist of @code{REAL}.
8695 @emph{Pointer types} consist of anything declared as @code{POINTER TO
8699 @emph{Scalar types} consist of all of the above.
8702 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
8705 @emph{Boolean types} consist of @code{BOOLEAN}.
8709 The following operators are supported, and appear in order of
8710 increasing precedence:
8714 Function argument or array index separator.
8717 Assignment. The value of @var{var} @code{:=} @var{value} is
8721 Less than, greater than on integral, floating-point, or enumerated
8725 Less than or equal to, greater than or equal to
8726 on integral, floating-point and enumerated types, or set inclusion on
8727 set types. Same precedence as @code{<}.
8729 @item =@r{, }<>@r{, }#
8730 Equality and two ways of expressing inequality, valid on scalar types.
8731 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
8732 available for inequality, since @code{#} conflicts with the script
8736 Set membership. Defined on set types and the types of their members.
8737 Same precedence as @code{<}.
8740 Boolean disjunction. Defined on boolean types.
8743 Boolean conjunction. Defined on boolean types.
8746 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8749 Addition and subtraction on integral and floating-point types, or union
8750 and difference on set types.
8753 Multiplication on integral and floating-point types, or set intersection
8757 Division on floating-point types, or symmetric set difference on set
8758 types. Same precedence as @code{*}.
8761 Integer division and remainder. Defined on integral types. Same
8762 precedence as @code{*}.
8765 Negative. Defined on @code{INTEGER} and @code{REAL} data.
8768 Pointer dereferencing. Defined on pointer types.
8771 Boolean negation. Defined on boolean types. Same precedence as
8775 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
8776 precedence as @code{^}.
8779 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
8782 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
8786 @value{GDBN} and Modula-2 scope operators.
8790 @emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
8791 treats the use of the operator @code{IN}, or the use of operators
8792 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
8793 @code{<=}, and @code{>=} on sets as an error.
8797 @node Built-In Func/Proc
8798 @subsubsection Built-in functions and procedures
8799 @cindex Modula-2 built-ins
8801 Modula-2 also makes available several built-in procedures and functions.
8802 In describing these, the following metavariables are used:
8807 represents an @code{ARRAY} variable.
8810 represents a @code{CHAR} constant or variable.
8813 represents a variable or constant of integral type.
8816 represents an identifier that belongs to a set. Generally used in the
8817 same function with the metavariable @var{s}. The type of @var{s} should
8818 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
8821 represents a variable or constant of integral or floating-point type.
8824 represents a variable or constant of floating-point type.
8830 represents a variable.
8833 represents a variable or constant of one of many types. See the
8834 explanation of the function for details.
8837 All Modula-2 built-in procedures also return a result, described below.
8841 Returns the absolute value of @var{n}.
8844 If @var{c} is a lower case letter, it returns its upper case
8845 equivalent, otherwise it returns its argument.
8848 Returns the character whose ordinal value is @var{i}.
8851 Decrements the value in the variable @var{v} by one. Returns the new value.
8853 @item DEC(@var{v},@var{i})
8854 Decrements the value in the variable @var{v} by @var{i}. Returns the
8857 @item EXCL(@var{m},@var{s})
8858 Removes the element @var{m} from the set @var{s}. Returns the new
8861 @item FLOAT(@var{i})
8862 Returns the floating point equivalent of the integer @var{i}.
8865 Returns the index of the last member of @var{a}.
8868 Increments the value in the variable @var{v} by one. Returns the new value.
8870 @item INC(@var{v},@var{i})
8871 Increments the value in the variable @var{v} by @var{i}. Returns the
8874 @item INCL(@var{m},@var{s})
8875 Adds the element @var{m} to the set @var{s} if it is not already
8876 there. Returns the new set.
8879 Returns the maximum value of the type @var{t}.
8882 Returns the minimum value of the type @var{t}.
8885 Returns boolean TRUE if @var{i} is an odd number.
8888 Returns the ordinal value of its argument. For example, the ordinal
8889 value of a character is its @sc{ascii} value (on machines supporting the
8890 @sc{ascii} character set). @var{x} must be of an ordered type, which include
8891 integral, character and enumerated types.
8894 Returns the size of its argument. @var{x} can be a variable or a type.
8896 @item TRUNC(@var{r})
8897 Returns the integral part of @var{r}.
8899 @item VAL(@var{t},@var{i})
8900 Returns the member of the type @var{t} whose ordinal value is @var{i}.
8904 @emph{Warning:} Sets and their operations are not yet supported, so
8905 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
8909 @cindex Modula-2 constants
8911 @subsubsection Constants
8913 @value{GDBN} allows you to express the constants of Modula-2 in the following
8919 Integer constants are simply a sequence of digits. When used in an
8920 expression, a constant is interpreted to be type-compatible with the
8921 rest of the expression. Hexadecimal integers are specified by a
8922 trailing @samp{H}, and octal integers by a trailing @samp{B}.
8925 Floating point constants appear as a sequence of digits, followed by a
8926 decimal point and another sequence of digits. An optional exponent can
8927 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
8928 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
8929 digits of the floating point constant must be valid decimal (base 10)
8933 Character constants consist of a single character enclosed by a pair of
8934 like quotes, either single (@code{'}) or double (@code{"}). They may
8935 also be expressed by their ordinal value (their @sc{ascii} value, usually)
8936 followed by a @samp{C}.
8939 String constants consist of a sequence of characters enclosed by a
8940 pair of like quotes, either single (@code{'}) or double (@code{"}).
8941 Escape sequences in the style of C are also allowed. @xref{C
8942 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
8946 Enumerated constants consist of an enumerated identifier.
8949 Boolean constants consist of the identifiers @code{TRUE} and
8953 Pointer constants consist of integral values only.
8956 Set constants are not yet supported.
8960 @subsubsection Modula-2 defaults
8961 @cindex Modula-2 defaults
8963 If type and range checking are set automatically by @value{GDBN}, they
8964 both default to @code{on} whenever the working language changes to
8965 Modula-2. This happens regardless of whether you or @value{GDBN}
8966 selected the working language.
8968 If you allow @value{GDBN} to set the language automatically, then entering
8969 code compiled from a file whose name ends with @file{.mod} sets the
8970 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
8971 the language automatically}, for further details.
8974 @subsubsection Deviations from standard Modula-2
8975 @cindex Modula-2, deviations from
8977 A few changes have been made to make Modula-2 programs easier to debug.
8978 This is done primarily via loosening its type strictness:
8982 Unlike in standard Modula-2, pointer constants can be formed by
8983 integers. This allows you to modify pointer variables during
8984 debugging. (In standard Modula-2, the actual address contained in a
8985 pointer variable is hidden from you; it can only be modified
8986 through direct assignment to another pointer variable or expression that
8987 returned a pointer.)
8990 C escape sequences can be used in strings and characters to represent
8991 non-printable characters. @value{GDBN} prints out strings with these
8992 escape sequences embedded. Single non-printable characters are
8993 printed using the @samp{CHR(@var{nnn})} format.
8996 The assignment operator (@code{:=}) returns the value of its right-hand
9000 All built-in procedures both modify @emph{and} return their argument.
9004 @subsubsection Modula-2 type and range checks
9005 @cindex Modula-2 checks
9008 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
9011 @c FIXME remove warning when type/range checks added
9013 @value{GDBN} considers two Modula-2 variables type equivalent if:
9017 They are of types that have been declared equivalent via a @code{TYPE
9018 @var{t1} = @var{t2}} statement
9021 They have been declared on the same line. (Note: This is true of the
9022 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
9025 As long as type checking is enabled, any attempt to combine variables
9026 whose types are not equivalent is an error.
9028 Range checking is done on all mathematical operations, assignment, array
9029 index bounds, and all built-in functions and procedures.
9032 @subsubsection The scope operators @code{::} and @code{.}
9034 @cindex @code{.}, Modula-2 scope operator
9035 @cindex colon, doubled as scope operator
9037 @vindex colon-colon@r{, in Modula-2}
9038 @c Info cannot handle :: but TeX can.
9041 @vindex ::@r{, in Modula-2}
9044 There are a few subtle differences between the Modula-2 scope operator
9045 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
9050 @var{module} . @var{id}
9051 @var{scope} :: @var{id}
9055 where @var{scope} is the name of a module or a procedure,
9056 @var{module} the name of a module, and @var{id} is any declared
9057 identifier within your program, except another module.
9059 Using the @code{::} operator makes @value{GDBN} search the scope
9060 specified by @var{scope} for the identifier @var{id}. If it is not
9061 found in the specified scope, then @value{GDBN} searches all scopes
9062 enclosing the one specified by @var{scope}.
9064 Using the @code{.} operator makes @value{GDBN} search the current scope for
9065 the identifier specified by @var{id} that was imported from the
9066 definition module specified by @var{module}. With this operator, it is
9067 an error if the identifier @var{id} was not imported from definition
9068 module @var{module}, or if @var{id} is not an identifier in
9072 @subsubsection @value{GDBN} and Modula-2
9074 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
9075 Five subcommands of @code{set print} and @code{show print} apply
9076 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
9077 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
9078 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
9079 analogue in Modula-2.
9081 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
9082 with any language, is not useful with Modula-2. Its
9083 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
9084 created in Modula-2 as they can in C or C@t{++}. However, because an
9085 address can be specified by an integral constant, the construct
9086 @samp{@{@var{type}@}@var{adrexp}} is still useful.
9088 @cindex @code{#} in Modula-2
9089 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
9090 interpreted as the beginning of a comment. Use @code{<>} instead.
9096 The extensions made to @value{GDBN} for Ada only support
9097 output from the @sc{gnu} Ada (GNAT) compiler.
9098 Other Ada compilers are not currently supported, and
9099 attempting to debug executables produced by them is most likely
9103 @cindex expressions in Ada
9105 * Ada Mode Intro:: General remarks on the Ada syntax
9106 and semantics supported by Ada mode
9108 * Omissions from Ada:: Restrictions on the Ada expression syntax.
9109 * Additions to Ada:: Extensions of the Ada expression syntax.
9110 * Stopping Before Main Program:: Debugging the program during elaboration.
9111 * Ada Glitches:: Known peculiarities of Ada mode.
9114 @node Ada Mode Intro
9115 @subsubsection Introduction
9116 @cindex Ada mode, general
9118 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
9119 syntax, with some extensions.
9120 The philosophy behind the design of this subset is
9124 That @value{GDBN} should provide basic literals and access to operations for
9125 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
9126 leaving more sophisticated computations to subprograms written into the
9127 program (which therefore may be called from @value{GDBN}).
9130 That type safety and strict adherence to Ada language restrictions
9131 are not particularly important to the @value{GDBN} user.
9134 That brevity is important to the @value{GDBN} user.
9137 Thus, for brevity, the debugger acts as if there were
9138 implicit @code{with} and @code{use} clauses in effect for all user-written
9139 packages, making it unnecessary to fully qualify most names with
9140 their packages, regardless of context. Where this causes ambiguity,
9141 @value{GDBN} asks the user's intent.
9143 The debugger will start in Ada mode if it detects an Ada main program.
9144 As for other languages, it will enter Ada mode when stopped in a program that
9145 was translated from an Ada source file.
9147 While in Ada mode, you may use `@t{--}' for comments. This is useful
9148 mostly for documenting command files. The standard @value{GDBN} comment
9149 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
9150 middle (to allow based literals).
9152 The debugger supports limited overloading. Given a subprogram call in which
9153 the function symbol has multiple definitions, it will use the number of
9154 actual parameters and some information about their types to attempt to narrow
9155 the set of definitions. It also makes very limited use of context, preferring
9156 procedures to functions in the context of the @code{call} command, and
9157 functions to procedures elsewhere.
9159 @node Omissions from Ada
9160 @subsubsection Omissions from Ada
9161 @cindex Ada, omissions from
9163 Here are the notable omissions from the subset:
9167 Only a subset of the attributes are supported:
9171 @t{'First}, @t{'Last}, and @t{'Length}
9172 on array objects (not on types and subtypes).
9175 @t{'Min} and @t{'Max}.
9178 @t{'Pos} and @t{'Val}.
9184 @t{'Range} on array objects (not subtypes), but only as the right
9185 operand of the membership (@code{in}) operator.
9188 @t{'Access}, @t{'Unchecked_Access}, and
9189 @t{'Unrestricted_Access} (a GNAT extension).
9197 @code{Characters.Latin_1} are not available and
9198 concatenation is not implemented. Thus, escape characters in strings are
9199 not currently available.
9202 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
9203 equality of representations. They will generally work correctly
9204 for strings and arrays whose elements have integer or enumeration types.
9205 They may not work correctly for arrays whose element
9206 types have user-defined equality, for arrays of real values
9207 (in particular, IEEE-conformant floating point, because of negative
9208 zeroes and NaNs), and for arrays whose elements contain unused bits with
9209 indeterminate values.
9212 The other component-by-component array operations (@code{and}, @code{or},
9213 @code{xor}, @code{not}, and relational tests other than equality)
9214 are not implemented.
9217 There are no record or array aggregates.
9220 Calls to dispatching subprograms are not implemented.
9223 The overloading algorithm is much more limited (i.e., less selective)
9224 than that of real Ada. It makes only limited use of the context in which a subexpression
9225 appears to resolve its meaning, and it is much looser in its rules for allowing
9226 type matches. As a result, some function calls will be ambiguous, and the user
9227 will be asked to choose the proper resolution.
9230 The @code{new} operator is not implemented.
9233 Entry calls are not implemented.
9236 Aside from printing, arithmetic operations on the native VAX floating-point
9237 formats are not supported.
9240 It is not possible to slice a packed array.
9243 @node Additions to Ada
9244 @subsubsection Additions to Ada
9245 @cindex Ada, deviations from
9247 As it does for other languages, @value{GDBN} makes certain generic
9248 extensions to Ada (@pxref{Expressions}):
9252 If the expression @var{E} is a variable residing in memory
9253 (typically a local variable or array element) and @var{N} is
9254 a positive integer, then @code{@var{E}@@@var{N}} displays the values of
9255 @var{E} and the @var{N}-1 adjacent variables following it in memory as an array.
9256 In Ada, this operator is generally not necessary, since its prime use
9257 is in displaying parts of an array, and slicing will usually do this in Ada.
9258 However, there are occasional uses when debugging programs
9259 in which certain debugging information has been optimized away.
9262 @code{@var{B}::@var{var}} means ``the variable named @var{var} that appears
9263 in function or file @var{B}.'' When @var{B} is a file name, you must typically
9264 surround it in single quotes.
9267 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
9268 @var{type} that appears at address @var{addr}.''
9271 A name starting with @samp{$} is a convenience variable
9272 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
9275 In addition, @value{GDBN} provides a few other shortcuts and outright additions specific
9280 The assignment statement is allowed as an expression, returning
9281 its right-hand operand as its value. Thus, you may enter
9285 print A(tmp := y + 1)
9289 The semicolon is allowed as an ``operator,'' returning as its value
9290 the value of its right-hand operand.
9291 This allows, for example,
9292 complex conditional breaks:
9296 condition 1 (report(i); k += 1; A(k) > 100)
9300 Rather than use catenation and symbolic character names to introduce special
9301 characters into strings, one may instead use a special bracket notation,
9302 which is also used to print strings. A sequence of characters of the form
9303 @samp{["@var{XX}"]} within a string or character literal denotes the
9304 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
9305 sequence of characters @samp{["""]} also denotes a single quotation mark
9306 in strings. For example,
9308 "One line.["0a"]Next line.["0a"]"
9311 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF}) after each
9315 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
9316 @t{'Max} is optional (and is ignored in any case). For example, it is valid
9324 When printing arrays, @value{GDBN} uses positional notation when the
9325 array has a lower bound of 1, and uses a modified named notation otherwise.
9326 For example, a one-dimensional array of three integers with a lower bound of 3 might print as
9333 That is, in contrast to valid Ada, only the first component has a @code{=>}
9337 You may abbreviate attributes in expressions with any unique,
9338 multi-character subsequence of
9339 their names (an exact match gets preference).
9340 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
9341 in place of @t{a'length}.
9344 @cindex quoting Ada internal identifiers
9345 Since Ada is case-insensitive, the debugger normally maps identifiers you type
9346 to lower case. The GNAT compiler uses upper-case characters for
9347 some of its internal identifiers, which are normally of no interest to users.
9348 For the rare occasions when you actually have to look at them,
9349 enclose them in angle brackets to avoid the lower-case mapping.
9352 @value{GDBP} print <JMPBUF_SAVE>[0]
9356 Printing an object of class-wide type or dereferencing an
9357 access-to-class-wide value will display all the components of the object's
9358 specific type (as indicated by its run-time tag). Likewise, component
9359 selection on such a value will operate on the specific type of the
9364 @node Stopping Before Main Program
9365 @subsubsection Stopping at the Very Beginning
9367 @cindex breakpointing Ada elaboration code
9368 It is sometimes necessary to debug the program during elaboration, and
9369 before reaching the main procedure.
9370 As defined in the Ada Reference
9371 Manual, the elaboration code is invoked from a procedure called
9372 @code{adainit}. To run your program up to the beginning of
9373 elaboration, simply use the following two commands:
9374 @code{tbreak adainit} and @code{run}.
9377 @subsubsection Known Peculiarities of Ada Mode
9378 @cindex Ada, problems
9380 Besides the omissions listed previously (@pxref{Omissions from Ada}),
9381 we know of several problems with and limitations of Ada mode in
9383 some of which will be fixed with planned future releases of the debugger
9384 and the GNU Ada compiler.
9388 Currently, the debugger
9389 has insufficient information to determine whether certain pointers represent
9390 pointers to objects or the objects themselves.
9391 Thus, the user may have to tack an extra @code{.all} after an expression
9392 to get it printed properly.
9395 Static constants that the compiler chooses not to materialize as objects in
9396 storage are invisible to the debugger.
9399 Named parameter associations in function argument lists are ignored (the
9400 argument lists are treated as positional).
9403 Many useful library packages are currently invisible to the debugger.
9406 Fixed-point arithmetic, conversions, input, and output is carried out using
9407 floating-point arithmetic, and may give results that only approximate those on
9411 The type of the @t{'Address} attribute may not be @code{System.Address}.
9414 The GNAT compiler never generates the prefix @code{Standard} for any of
9415 the standard symbols defined by the Ada language. @value{GDBN} knows about
9416 this: it will strip the prefix from names when you use it, and will never
9417 look for a name you have so qualified among local symbols, nor match against
9418 symbols in other packages or subprograms. If you have
9419 defined entities anywhere in your program other than parameters and
9420 local variables whose simple names match names in @code{Standard},
9421 GNAT's lack of qualification here can cause confusion. When this happens,
9422 you can usually resolve the confusion
9423 by qualifying the problematic names with package
9424 @code{Standard} explicitly.
9427 @node Unsupported languages
9428 @section Unsupported languages
9430 @cindex unsupported languages
9431 @cindex minimal language
9432 In addition to the other fully-supported programming languages,
9433 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
9434 It does not represent a real programming language, but provides a set
9435 of capabilities close to what the C or assembly languages provide.
9436 This should allow most simple operations to be performed while debugging
9437 an application that uses a language currently not supported by @value{GDBN}.
9439 If the language is set to @code{auto}, @value{GDBN} will automatically
9440 select this language if the current frame corresponds to an unsupported
9444 @chapter Examining the Symbol Table
9446 The commands described in this chapter allow you to inquire about the
9447 symbols (names of variables, functions and types) defined in your
9448 program. This information is inherent in the text of your program and
9449 does not change as your program executes. @value{GDBN} finds it in your
9450 program's symbol table, in the file indicated when you started @value{GDBN}
9451 (@pxref{File Options, ,Choosing files}), or by one of the
9452 file-management commands (@pxref{Files, ,Commands to specify files}).
9454 @cindex symbol names
9455 @cindex names of symbols
9456 @cindex quoting names
9457 Occasionally, you may need to refer to symbols that contain unusual
9458 characters, which @value{GDBN} ordinarily treats as word delimiters. The
9459 most frequent case is in referring to static variables in other
9460 source files (@pxref{Variables,,Program variables}). File names
9461 are recorded in object files as debugging symbols, but @value{GDBN} would
9462 ordinarily parse a typical file name, like @file{foo.c}, as the three words
9463 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
9464 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
9471 looks up the value of @code{x} in the scope of the file @file{foo.c}.
9474 @kindex info address
9475 @cindex address of a symbol
9476 @item info address @var{symbol}
9477 Describe where the data for @var{symbol} is stored. For a register
9478 variable, this says which register it is kept in. For a non-register
9479 local variable, this prints the stack-frame offset at which the variable
9482 Note the contrast with @samp{print &@var{symbol}}, which does not work
9483 at all for a register variable, and for a stack local variable prints
9484 the exact address of the current instantiation of the variable.
9487 @cindex symbol from address
9488 @item info symbol @var{addr}
9489 Print the name of a symbol which is stored at the address @var{addr}.
9490 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
9491 nearest symbol and an offset from it:
9494 (@value{GDBP}) info symbol 0x54320
9495 _initialize_vx + 396 in section .text
9499 This is the opposite of the @code{info address} command. You can use
9500 it to find out the name of a variable or a function given its address.
9503 @item whatis @var{expr}
9504 Print the data type of expression @var{expr}. @var{expr} is not
9505 actually evaluated, and any side-effecting operations (such as
9506 assignments or function calls) inside it do not take place.
9507 @xref{Expressions, ,Expressions}.
9510 Print the data type of @code{$}, the last value in the value history.
9513 @item ptype @var{typename}
9514 Print a description of data type @var{typename}. @var{typename} may be
9515 the name of a type, or for C code it may have the form @samp{class
9516 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
9517 @var{union-tag}} or @samp{enum @var{enum-tag}}.
9519 @item ptype @var{expr}
9521 Print a description of the type of expression @var{expr}. @code{ptype}
9522 differs from @code{whatis} by printing a detailed description, instead
9523 of just the name of the type.
9525 For example, for this variable declaration:
9528 struct complex @{double real; double imag;@} v;
9532 the two commands give this output:
9536 (@value{GDBP}) whatis v
9537 type = struct complex
9538 (@value{GDBP}) ptype v
9539 type = struct complex @{
9547 As with @code{whatis}, using @code{ptype} without an argument refers to
9548 the type of @code{$}, the last value in the value history.
9551 @item info types @var{regexp}
9553 Print a brief description of all types whose names match @var{regexp}
9554 (or all types in your program, if you supply no argument). Each
9555 complete typename is matched as though it were a complete line; thus,
9556 @samp{i type value} gives information on all types in your program whose
9557 names include the string @code{value}, but @samp{i type ^value$} gives
9558 information only on types whose complete name is @code{value}.
9560 This command differs from @code{ptype} in two ways: first, like
9561 @code{whatis}, it does not print a detailed description; second, it
9562 lists all source files where a type is defined.
9565 @cindex local variables
9566 @item info scope @var{addr}
9567 List all the variables local to a particular scope. This command
9568 accepts a location---a function name, a source line, or an address
9569 preceded by a @samp{*}, and prints all the variables local to the
9570 scope defined by that location. For example:
9573 (@value{GDBP}) @b{info scope command_line_handler}
9574 Scope for command_line_handler:
9575 Symbol rl is an argument at stack/frame offset 8, length 4.
9576 Symbol linebuffer is in static storage at address 0x150a18, length 4.
9577 Symbol linelength is in static storage at address 0x150a1c, length 4.
9578 Symbol p is a local variable in register $esi, length 4.
9579 Symbol p1 is a local variable in register $ebx, length 4.
9580 Symbol nline is a local variable in register $edx, length 4.
9581 Symbol repeat is a local variable at frame offset -8, length 4.
9585 This command is especially useful for determining what data to collect
9586 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
9591 Show information about the current source file---that is, the source file for
9592 the function containing the current point of execution:
9595 the name of the source file, and the directory containing it,
9597 the directory it was compiled in,
9599 its length, in lines,
9601 which programming language it is written in,
9603 whether the executable includes debugging information for that file, and
9604 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
9606 whether the debugging information includes information about
9607 preprocessor macros.
9611 @kindex info sources
9613 Print the names of all source files in your program for which there is
9614 debugging information, organized into two lists: files whose symbols
9615 have already been read, and files whose symbols will be read when needed.
9617 @kindex info functions
9618 @item info functions
9619 Print the names and data types of all defined functions.
9621 @item info functions @var{regexp}
9622 Print the names and data types of all defined functions
9623 whose names contain a match for regular expression @var{regexp}.
9624 Thus, @samp{info fun step} finds all functions whose names
9625 include @code{step}; @samp{info fun ^step} finds those whose names
9626 start with @code{step}. If a function name contains characters
9627 that conflict with the regular expression language (eg.
9628 @samp{operator*()}), they may be quoted with a backslash.
9630 @kindex info variables
9631 @item info variables
9632 Print the names and data types of all variables that are declared
9633 outside of functions (i.e.@: excluding local variables).
9635 @item info variables @var{regexp}
9636 Print the names and data types of all variables (except for local
9637 variables) whose names contain a match for regular expression
9640 @kindex info classes
9642 @itemx info classes @var{regexp}
9643 Display all Objective-C classes in your program, or
9644 (with the @var{regexp} argument) all those matching a particular regular
9647 @kindex info selectors
9648 @item info selectors
9649 @itemx info selectors @var{regexp}
9650 Display all Objective-C selectors in your program, or
9651 (with the @var{regexp} argument) all those matching a particular regular
9655 This was never implemented.
9656 @kindex info methods
9658 @itemx info methods @var{regexp}
9659 The @code{info methods} command permits the user to examine all defined
9660 methods within C@t{++} program, or (with the @var{regexp} argument) a
9661 specific set of methods found in the various C@t{++} classes. Many
9662 C@t{++} classes provide a large number of methods. Thus, the output
9663 from the @code{ptype} command can be overwhelming and hard to use. The
9664 @code{info-methods} command filters the methods, printing only those
9665 which match the regular-expression @var{regexp}.
9668 @cindex reloading symbols
9669 Some systems allow individual object files that make up your program to
9670 be replaced without stopping and restarting your program. For example,
9671 in VxWorks you can simply recompile a defective object file and keep on
9672 running. If you are running on one of these systems, you can allow
9673 @value{GDBN} to reload the symbols for automatically relinked modules:
9676 @kindex set symbol-reloading
9677 @item set symbol-reloading on
9678 Replace symbol definitions for the corresponding source file when an
9679 object file with a particular name is seen again.
9681 @item set symbol-reloading off
9682 Do not replace symbol definitions when encountering object files of the
9683 same name more than once. This is the default state; if you are not
9684 running on a system that permits automatic relinking of modules, you
9685 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
9686 may discard symbols when linking large programs, that may contain
9687 several modules (from different directories or libraries) with the same
9690 @kindex show symbol-reloading
9691 @item show symbol-reloading
9692 Show the current @code{on} or @code{off} setting.
9695 @kindex set opaque-type-resolution
9696 @item set opaque-type-resolution on
9697 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
9698 declared as a pointer to a @code{struct}, @code{class}, or
9699 @code{union}---for example, @code{struct MyType *}---that is used in one
9700 source file although the full declaration of @code{struct MyType} is in
9701 another source file. The default is on.
9703 A change in the setting of this subcommand will not take effect until
9704 the next time symbols for a file are loaded.
9706 @item set opaque-type-resolution off
9707 Tell @value{GDBN} not to resolve opaque types. In this case, the type
9708 is printed as follows:
9710 @{<no data fields>@}
9713 @kindex show opaque-type-resolution
9714 @item show opaque-type-resolution
9715 Show whether opaque types are resolved or not.
9717 @kindex maint print symbols
9719 @kindex maint print psymbols
9720 @cindex partial symbol dump
9721 @item maint print symbols @var{filename}
9722 @itemx maint print psymbols @var{filename}
9723 @itemx maint print msymbols @var{filename}
9724 Write a dump of debugging symbol data into the file @var{filename}.
9725 These commands are used to debug the @value{GDBN} symbol-reading code. Only
9726 symbols with debugging data are included. If you use @samp{maint print
9727 symbols}, @value{GDBN} includes all the symbols for which it has already
9728 collected full details: that is, @var{filename} reflects symbols for
9729 only those files whose symbols @value{GDBN} has read. You can use the
9730 command @code{info sources} to find out which files these are. If you
9731 use @samp{maint print psymbols} instead, the dump shows information about
9732 symbols that @value{GDBN} only knows partially---that is, symbols defined in
9733 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
9734 @samp{maint print msymbols} dumps just the minimal symbol information
9735 required for each object file from which @value{GDBN} has read some symbols.
9736 @xref{Files, ,Commands to specify files}, for a discussion of how
9737 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
9739 @kindex maint info symtabs
9740 @kindex maint info psymtabs
9741 @cindex listing @value{GDBN}'s internal symbol tables
9742 @cindex symbol tables, listing @value{GDBN}'s internal
9743 @cindex full symbol tables, listing @value{GDBN}'s internal
9744 @cindex partial symbol tables, listing @value{GDBN}'s internal
9745 @item maint info symtabs @r{[} @var{regexp} @r{]}
9746 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
9748 List the @code{struct symtab} or @code{struct partial_symtab}
9749 structures whose names match @var{regexp}. If @var{regexp} is not
9750 given, list them all. The output includes expressions which you can
9751 copy into a @value{GDBN} debugging this one to examine a particular
9752 structure in more detail. For example:
9755 (@value{GDBP}) maint info psymtabs dwarf2read
9756 @{ objfile /home/gnu/build/gdb/gdb
9757 ((struct objfile *) 0x82e69d0)
9758 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
9759 ((struct partial_symtab *) 0x8474b10)
9762 text addresses 0x814d3c8 -- 0x8158074
9763 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
9764 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
9768 (@value{GDBP}) maint info symtabs
9772 We see that there is one partial symbol table whose filename contains
9773 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
9774 and we see that @value{GDBN} has not read in any symtabs yet at all.
9775 If we set a breakpoint on a function, that will cause @value{GDBN} to
9776 read the symtab for the compilation unit containing that function:
9779 (@value{GDBP}) break dwarf2_psymtab_to_symtab
9780 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
9782 (@value{GDBP}) maint info symtabs
9783 @{ objfile /home/gnu/build/gdb/gdb
9784 ((struct objfile *) 0x82e69d0)
9785 @{ symtab /home/gnu/src/gdb/dwarf2read.c
9786 ((struct symtab *) 0x86c1f38)
9789 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
9799 @chapter Altering Execution
9801 Once you think you have found an error in your program, you might want to
9802 find out for certain whether correcting the apparent error would lead to
9803 correct results in the rest of the run. You can find the answer by
9804 experiment, using the @value{GDBN} features for altering execution of the
9807 For example, you can store new values into variables or memory
9808 locations, give your program a signal, restart it at a different
9809 address, or even return prematurely from a function.
9812 * Assignment:: Assignment to variables
9813 * Jumping:: Continuing at a different address
9814 * Signaling:: Giving your program a signal
9815 * Returning:: Returning from a function
9816 * Calling:: Calling your program's functions
9817 * Patching:: Patching your program
9821 @section Assignment to variables
9824 @cindex setting variables
9825 To alter the value of a variable, evaluate an assignment expression.
9826 @xref{Expressions, ,Expressions}. For example,
9833 stores the value 4 into the variable @code{x}, and then prints the
9834 value of the assignment expression (which is 4).
9835 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
9836 information on operators in supported languages.
9838 @kindex set variable
9839 @cindex variables, setting
9840 If you are not interested in seeing the value of the assignment, use the
9841 @code{set} command instead of the @code{print} command. @code{set} is
9842 really the same as @code{print} except that the expression's value is
9843 not printed and is not put in the value history (@pxref{Value History,
9844 ,Value history}). The expression is evaluated only for its effects.
9846 If the beginning of the argument string of the @code{set} command
9847 appears identical to a @code{set} subcommand, use the @code{set
9848 variable} command instead of just @code{set}. This command is identical
9849 to @code{set} except for its lack of subcommands. For example, if your
9850 program has a variable @code{width}, you get an error if you try to set
9851 a new value with just @samp{set width=13}, because @value{GDBN} has the
9852 command @code{set width}:
9855 (@value{GDBP}) whatis width
9857 (@value{GDBP}) p width
9859 (@value{GDBP}) set width=47
9860 Invalid syntax in expression.
9864 The invalid expression, of course, is @samp{=47}. In
9865 order to actually set the program's variable @code{width}, use
9868 (@value{GDBP}) set var width=47
9871 Because the @code{set} command has many subcommands that can conflict
9872 with the names of program variables, it is a good idea to use the
9873 @code{set variable} command instead of just @code{set}. For example, if
9874 your program has a variable @code{g}, you run into problems if you try
9875 to set a new value with just @samp{set g=4}, because @value{GDBN} has
9876 the command @code{set gnutarget}, abbreviated @code{set g}:
9880 (@value{GDBP}) whatis g
9884 (@value{GDBP}) set g=4
9888 The program being debugged has been started already.
9889 Start it from the beginning? (y or n) y
9890 Starting program: /home/smith/cc_progs/a.out
9891 "/home/smith/cc_progs/a.out": can't open to read symbols:
9893 (@value{GDBP}) show g
9894 The current BFD target is "=4".
9899 The program variable @code{g} did not change, and you silently set the
9900 @code{gnutarget} to an invalid value. In order to set the variable
9904 (@value{GDBP}) set var g=4
9907 @value{GDBN} allows more implicit conversions in assignments than C; you can
9908 freely store an integer value into a pointer variable or vice versa,
9909 and you can convert any structure to any other structure that is the
9910 same length or shorter.
9911 @comment FIXME: how do structs align/pad in these conversions?
9912 @comment /doc@cygnus.com 18dec1990
9914 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
9915 construct to generate a value of specified type at a specified address
9916 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
9917 to memory location @code{0x83040} as an integer (which implies a certain size
9918 and representation in memory), and
9921 set @{int@}0x83040 = 4
9925 stores the value 4 into that memory location.
9928 @section Continuing at a different address
9930 Ordinarily, when you continue your program, you do so at the place where
9931 it stopped, with the @code{continue} command. You can instead continue at
9932 an address of your own choosing, with the following commands:
9936 @item jump @var{linespec}
9937 Resume execution at line @var{linespec}. Execution stops again
9938 immediately if there is a breakpoint there. @xref{List, ,Printing
9939 source lines}, for a description of the different forms of
9940 @var{linespec}. It is common practice to use the @code{tbreak} command
9941 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
9944 The @code{jump} command does not change the current stack frame, or
9945 the stack pointer, or the contents of any memory location or any
9946 register other than the program counter. If line @var{linespec} is in
9947 a different function from the one currently executing, the results may
9948 be bizarre if the two functions expect different patterns of arguments or
9949 of local variables. For this reason, the @code{jump} command requests
9950 confirmation if the specified line is not in the function currently
9951 executing. However, even bizarre results are predictable if you are
9952 well acquainted with the machine-language code of your program.
9954 @item jump *@var{address}
9955 Resume execution at the instruction at address @var{address}.
9958 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
9959 On many systems, you can get much the same effect as the @code{jump}
9960 command by storing a new value into the register @code{$pc}. The
9961 difference is that this does not start your program running; it only
9962 changes the address of where it @emph{will} run when you continue. For
9970 makes the next @code{continue} command or stepping command execute at
9971 address @code{0x485}, rather than at the address where your program stopped.
9972 @xref{Continuing and Stepping, ,Continuing and stepping}.
9974 The most common occasion to use the @code{jump} command is to back
9975 up---perhaps with more breakpoints set---over a portion of a program
9976 that has already executed, in order to examine its execution in more
9981 @section Giving your program a signal
9985 @item signal @var{signal}
9986 Resume execution where your program stopped, but immediately give it the
9987 signal @var{signal}. @var{signal} can be the name or the number of a
9988 signal. For example, on many systems @code{signal 2} and @code{signal
9989 SIGINT} are both ways of sending an interrupt signal.
9991 Alternatively, if @var{signal} is zero, continue execution without
9992 giving a signal. This is useful when your program stopped on account of
9993 a signal and would ordinary see the signal when resumed with the
9994 @code{continue} command; @samp{signal 0} causes it to resume without a
9997 @code{signal} does not repeat when you press @key{RET} a second time
9998 after executing the command.
10002 Invoking the @code{signal} command is not the same as invoking the
10003 @code{kill} utility from the shell. Sending a signal with @code{kill}
10004 causes @value{GDBN} to decide what to do with the signal depending on
10005 the signal handling tables (@pxref{Signals}). The @code{signal} command
10006 passes the signal directly to your program.
10010 @section Returning from a function
10013 @cindex returning from a function
10016 @itemx return @var{expression}
10017 You can cancel execution of a function call with the @code{return}
10018 command. If you give an
10019 @var{expression} argument, its value is used as the function's return
10023 When you use @code{return}, @value{GDBN} discards the selected stack frame
10024 (and all frames within it). You can think of this as making the
10025 discarded frame return prematurely. If you wish to specify a value to
10026 be returned, give that value as the argument to @code{return}.
10028 This pops the selected stack frame (@pxref{Selection, ,Selecting a
10029 frame}), and any other frames inside of it, leaving its caller as the
10030 innermost remaining frame. That frame becomes selected. The
10031 specified value is stored in the registers used for returning values
10034 The @code{return} command does not resume execution; it leaves the
10035 program stopped in the state that would exist if the function had just
10036 returned. In contrast, the @code{finish} command (@pxref{Continuing
10037 and Stepping, ,Continuing and stepping}) resumes execution until the
10038 selected stack frame returns naturally.
10041 @section Calling program functions
10043 @cindex calling functions
10046 @item call @var{expr}
10047 Evaluate the expression @var{expr} without displaying @code{void}
10051 You can use this variant of the @code{print} command if you want to
10052 execute a function from your program, but without cluttering the output
10053 with @code{void} returned values. If the result is not void, it
10054 is printed and saved in the value history.
10057 @section Patching programs
10059 @cindex patching binaries
10060 @cindex writing into executables
10061 @cindex writing into corefiles
10063 By default, @value{GDBN} opens the file containing your program's
10064 executable code (or the corefile) read-only. This prevents accidental
10065 alterations to machine code; but it also prevents you from intentionally
10066 patching your program's binary.
10068 If you'd like to be able to patch the binary, you can specify that
10069 explicitly with the @code{set write} command. For example, you might
10070 want to turn on internal debugging flags, or even to make emergency
10076 @itemx set write off
10077 If you specify @samp{set write on}, @value{GDBN} opens executable and
10078 core files for both reading and writing; if you specify @samp{set write
10079 off} (the default), @value{GDBN} opens them read-only.
10081 If you have already loaded a file, you must load it again (using the
10082 @code{exec-file} or @code{core-file} command) after changing @code{set
10083 write}, for your new setting to take effect.
10087 Display whether executable files and core files are opened for writing
10088 as well as reading.
10092 @chapter @value{GDBN} Files
10094 @value{GDBN} needs to know the file name of the program to be debugged,
10095 both in order to read its symbol table and in order to start your
10096 program. To debug a core dump of a previous run, you must also tell
10097 @value{GDBN} the name of the core dump file.
10100 * Files:: Commands to specify files
10101 * Separate Debug Files:: Debugging information in separate files
10102 * Symbol Errors:: Errors reading symbol files
10106 @section Commands to specify files
10108 @cindex symbol table
10109 @cindex core dump file
10111 You may want to specify executable and core dump file names. The usual
10112 way to do this is at start-up time, using the arguments to
10113 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
10114 Out of @value{GDBN}}).
10116 Occasionally it is necessary to change to a different file during a
10117 @value{GDBN} session. Or you may run @value{GDBN} and forget to specify
10118 a file you want to use. In these situations the @value{GDBN} commands
10119 to specify new files are useful.
10122 @cindex executable file
10124 @item file @var{filename}
10125 Use @var{filename} as the program to be debugged. It is read for its
10126 symbols and for the contents of pure memory. It is also the program
10127 executed when you use the @code{run} command. If you do not specify a
10128 directory and the file is not found in the @value{GDBN} working directory,
10129 @value{GDBN} uses the environment variable @code{PATH} as a list of
10130 directories to search, just as the shell does when looking for a program
10131 to run. You can change the value of this variable, for both @value{GDBN}
10132 and your program, using the @code{path} command.
10134 On systems with memory-mapped files, an auxiliary file named
10135 @file{@var{filename}.syms} may hold symbol table information for
10136 @var{filename}. If so, @value{GDBN} maps in the symbol table from
10137 @file{@var{filename}.syms}, starting up more quickly. See the
10138 descriptions of the file options @samp{-mapped} and @samp{-readnow}
10139 (available on the command line, and with the commands @code{file},
10140 @code{symbol-file}, or @code{add-symbol-file}, described below),
10141 for more information.
10144 @code{file} with no argument makes @value{GDBN} discard any information it
10145 has on both executable file and the symbol table.
10148 @item exec-file @r{[} @var{filename} @r{]}
10149 Specify that the program to be run (but not the symbol table) is found
10150 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
10151 if necessary to locate your program. Omitting @var{filename} means to
10152 discard information on the executable file.
10154 @kindex symbol-file
10155 @item symbol-file @r{[} @var{filename} @r{]}
10156 Read symbol table information from file @var{filename}. @code{PATH} is
10157 searched when necessary. Use the @code{file} command to get both symbol
10158 table and program to run from the same file.
10160 @code{symbol-file} with no argument clears out @value{GDBN} information on your
10161 program's symbol table.
10163 The @code{symbol-file} command causes @value{GDBN} to forget the contents
10164 of its convenience variables, the value history, and all breakpoints and
10165 auto-display expressions. This is because they may contain pointers to
10166 the internal data recording symbols and data types, which are part of
10167 the old symbol table data being discarded inside @value{GDBN}.
10169 @code{symbol-file} does not repeat if you press @key{RET} again after
10172 When @value{GDBN} is configured for a particular environment, it
10173 understands debugging information in whatever format is the standard
10174 generated for that environment; you may use either a @sc{gnu} compiler, or
10175 other compilers that adhere to the local conventions.
10176 Best results are usually obtained from @sc{gnu} compilers; for example,
10177 using @code{@value{GCC}} you can generate debugging information for
10180 For most kinds of object files, with the exception of old SVR3 systems
10181 using COFF, the @code{symbol-file} command does not normally read the
10182 symbol table in full right away. Instead, it scans the symbol table
10183 quickly to find which source files and which symbols are present. The
10184 details are read later, one source file at a time, as they are needed.
10186 The purpose of this two-stage reading strategy is to make @value{GDBN}
10187 start up faster. For the most part, it is invisible except for
10188 occasional pauses while the symbol table details for a particular source
10189 file are being read. (The @code{set verbose} command can turn these
10190 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
10191 warnings and messages}.)
10193 We have not implemented the two-stage strategy for COFF yet. When the
10194 symbol table is stored in COFF format, @code{symbol-file} reads the
10195 symbol table data in full right away. Note that ``stabs-in-COFF''
10196 still does the two-stage strategy, since the debug info is actually
10200 @cindex reading symbols immediately
10201 @cindex symbols, reading immediately
10203 @cindex memory-mapped symbol file
10204 @cindex saving symbol table
10205 @item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10206 @itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10207 You can override the @value{GDBN} two-stage strategy for reading symbol
10208 tables by using the @samp{-readnow} option with any of the commands that
10209 load symbol table information, if you want to be sure @value{GDBN} has the
10210 entire symbol table available.
10212 If memory-mapped files are available on your system through the
10213 @code{mmap} system call, you can use another option, @samp{-mapped}, to
10214 cause @value{GDBN} to write the symbols for your program into a reusable
10215 file. Future @value{GDBN} debugging sessions map in symbol information
10216 from this auxiliary symbol file (if the program has not changed), rather
10217 than spending time reading the symbol table from the executable
10218 program. Using the @samp{-mapped} option has the same effect as
10219 starting @value{GDBN} with the @samp{-mapped} command-line option.
10221 You can use both options together, to make sure the auxiliary symbol
10222 file has all the symbol information for your program.
10224 The auxiliary symbol file for a program called @var{myprog} is called
10225 @samp{@var{myprog}.syms}. Once this file exists (so long as it is newer
10226 than the corresponding executable), @value{GDBN} always attempts to use
10227 it when you debug @var{myprog}; no special options or commands are
10230 The @file{.syms} file is specific to the host machine where you run
10231 @value{GDBN}. It holds an exact image of the internal @value{GDBN}
10232 symbol table. It cannot be shared across multiple host platforms.
10234 @c FIXME: for now no mention of directories, since this seems to be in
10235 @c flux. 13mar1992 status is that in theory GDB would look either in
10236 @c current dir or in same dir as myprog; but issues like competing
10237 @c GDB's, or clutter in system dirs, mean that in practice right now
10238 @c only current dir is used. FFish says maybe a special GDB hierarchy
10239 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
10243 @item core-file @r{[} @var{filename} @r{]}
10245 Specify the whereabouts of a core dump file to be used as the ``contents
10246 of memory''. Traditionally, core files contain only some parts of the
10247 address space of the process that generated them; @value{GDBN} can access the
10248 executable file itself for other parts.
10250 @code{core-file} with no argument specifies that no core file is
10253 Note that the core file is ignored when your program is actually running
10254 under @value{GDBN}. So, if you have been running your program and you
10255 wish to debug a core file instead, you must kill the subprocess in which
10256 the program is running. To do this, use the @code{kill} command
10257 (@pxref{Kill Process, ,Killing the child process}).
10259 @kindex add-symbol-file
10260 @cindex dynamic linking
10261 @item add-symbol-file @var{filename} @var{address}
10262 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10263 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
10264 The @code{add-symbol-file} command reads additional symbol table
10265 information from the file @var{filename}. You would use this command
10266 when @var{filename} has been dynamically loaded (by some other means)
10267 into the program that is running. @var{address} should be the memory
10268 address at which the file has been loaded; @value{GDBN} cannot figure
10269 this out for itself. You can additionally specify an arbitrary number
10270 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
10271 section name and base address for that section. You can specify any
10272 @var{address} as an expression.
10274 The symbol table of the file @var{filename} is added to the symbol table
10275 originally read with the @code{symbol-file} command. You can use the
10276 @code{add-symbol-file} command any number of times; the new symbol data
10277 thus read keeps adding to the old. To discard all old symbol data
10278 instead, use the @code{symbol-file} command without any arguments.
10280 @cindex relocatable object files, reading symbols from
10281 @cindex object files, relocatable, reading symbols from
10282 @cindex reading symbols from relocatable object files
10283 @cindex symbols, reading from relocatable object files
10284 @cindex @file{.o} files, reading symbols from
10285 Although @var{filename} is typically a shared library file, an
10286 executable file, or some other object file which has been fully
10287 relocated for loading into a process, you can also load symbolic
10288 information from relocatable @file{.o} files, as long as:
10292 the file's symbolic information refers only to linker symbols defined in
10293 that file, not to symbols defined by other object files,
10295 every section the file's symbolic information refers to has actually
10296 been loaded into the inferior, as it appears in the file, and
10298 you can determine the address at which every section was loaded, and
10299 provide these to the @code{add-symbol-file} command.
10303 Some embedded operating systems, like Sun Chorus and VxWorks, can load
10304 relocatable files into an already running program; such systems
10305 typically make the requirements above easy to meet. However, it's
10306 important to recognize that many native systems use complex link
10307 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
10308 assembly, for example) that make the requirements difficult to meet. In
10309 general, one cannot assume that using @code{add-symbol-file} to read a
10310 relocatable object file's symbolic information will have the same effect
10311 as linking the relocatable object file into the program in the normal
10314 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
10316 You can use the @samp{-mapped} and @samp{-readnow} options just as with
10317 the @code{symbol-file} command, to change how @value{GDBN} manages the symbol
10318 table information for @var{filename}.
10320 @kindex add-shared-symbol-file
10321 @item add-shared-symbol-file
10322 The @code{add-shared-symbol-file} command can be used only under Harris' CXUX
10323 operating system for the Motorola 88k. @value{GDBN} automatically looks for
10324 shared libraries, however if @value{GDBN} does not find yours, you can run
10325 @code{add-shared-symbol-file}. It takes no arguments.
10329 The @code{section} command changes the base address of section SECTION of
10330 the exec file to ADDR. This can be used if the exec file does not contain
10331 section addresses, (such as in the a.out format), or when the addresses
10332 specified in the file itself are wrong. Each section must be changed
10333 separately. The @code{info files} command, described below, lists all
10334 the sections and their addresses.
10337 @kindex info target
10340 @code{info files} and @code{info target} are synonymous; both print the
10341 current target (@pxref{Targets, ,Specifying a Debugging Target}),
10342 including the names of the executable and core dump files currently in
10343 use by @value{GDBN}, and the files from which symbols were loaded. The
10344 command @code{help target} lists all possible targets rather than
10347 @kindex maint info sections
10348 @item maint info sections
10349 Another command that can give you extra information about program sections
10350 is @code{maint info sections}. In addition to the section information
10351 displayed by @code{info files}, this command displays the flags and file
10352 offset of each section in the executable and core dump files. In addition,
10353 @code{maint info sections} provides the following command options (which
10354 may be arbitrarily combined):
10358 Display sections for all loaded object files, including shared libraries.
10359 @item @var{sections}
10360 Display info only for named @var{sections}.
10361 @item @var{section-flags}
10362 Display info only for sections for which @var{section-flags} are true.
10363 The section flags that @value{GDBN} currently knows about are:
10366 Section will have space allocated in the process when loaded.
10367 Set for all sections except those containing debug information.
10369 Section will be loaded from the file into the child process memory.
10370 Set for pre-initialized code and data, clear for @code{.bss} sections.
10372 Section needs to be relocated before loading.
10374 Section cannot be modified by the child process.
10376 Section contains executable code only.
10378 Section contains data only (no executable code).
10380 Section will reside in ROM.
10382 Section contains data for constructor/destructor lists.
10384 Section is not empty.
10386 An instruction to the linker to not output the section.
10387 @item COFF_SHARED_LIBRARY
10388 A notification to the linker that the section contains
10389 COFF shared library information.
10391 Section contains common symbols.
10394 @kindex set trust-readonly-sections
10395 @item set trust-readonly-sections on
10396 Tell @value{GDBN} that readonly sections in your object file
10397 really are read-only (i.e.@: that their contents will not change).
10398 In that case, @value{GDBN} can fetch values from these sections
10399 out of the object file, rather than from the target program.
10400 For some targets (notably embedded ones), this can be a significant
10401 enhancement to debugging performance.
10403 The default is off.
10405 @item set trust-readonly-sections off
10406 Tell @value{GDBN} not to trust readonly sections. This means that
10407 the contents of the section might change while the program is running,
10408 and must therefore be fetched from the target when needed.
10411 All file-specifying commands allow both absolute and relative file names
10412 as arguments. @value{GDBN} always converts the file name to an absolute file
10413 name and remembers it that way.
10415 @cindex shared libraries
10416 @value{GDBN} supports HP-UX, SunOS, SVr4, Irix 5, and IBM RS/6000 shared
10419 @value{GDBN} automatically loads symbol definitions from shared libraries
10420 when you use the @code{run} command, or when you examine a core file.
10421 (Before you issue the @code{run} command, @value{GDBN} does not understand
10422 references to a function in a shared library, however---unless you are
10423 debugging a core file).
10425 On HP-UX, if the program loads a library explicitly, @value{GDBN}
10426 automatically loads the symbols at the time of the @code{shl_load} call.
10428 @c FIXME: some @value{GDBN} release may permit some refs to undef
10429 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
10430 @c FIXME...lib; check this from time to time when updating manual
10432 There are times, however, when you may wish to not automatically load
10433 symbol definitions from shared libraries, such as when they are
10434 particularly large or there are many of them.
10436 To control the automatic loading of shared library symbols, use the
10440 @kindex set auto-solib-add
10441 @item set auto-solib-add @var{mode}
10442 If @var{mode} is @code{on}, symbols from all shared object libraries
10443 will be loaded automatically when the inferior begins execution, you
10444 attach to an independently started inferior, or when the dynamic linker
10445 informs @value{GDBN} that a new library has been loaded. If @var{mode}
10446 is @code{off}, symbols must be loaded manually, using the
10447 @code{sharedlibrary} command. The default value is @code{on}.
10449 @kindex show auto-solib-add
10450 @item show auto-solib-add
10451 Display the current autoloading mode.
10454 To explicitly load shared library symbols, use the @code{sharedlibrary}
10458 @kindex info sharedlibrary
10461 @itemx info sharedlibrary
10462 Print the names of the shared libraries which are currently loaded.
10464 @kindex sharedlibrary
10466 @item sharedlibrary @var{regex}
10467 @itemx share @var{regex}
10468 Load shared object library symbols for files matching a
10469 Unix regular expression.
10470 As with files loaded automatically, it only loads shared libraries
10471 required by your program for a core file or after typing @code{run}. If
10472 @var{regex} is omitted all shared libraries required by your program are
10476 On some systems, such as HP-UX systems, @value{GDBN} supports
10477 autoloading shared library symbols until a limiting threshold size is
10478 reached. This provides the benefit of allowing autoloading to remain on
10479 by default, but avoids autoloading excessively large shared libraries,
10480 up to a threshold that is initially set, but which you can modify if you
10483 Beyond that threshold, symbols from shared libraries must be explicitly
10484 loaded. To load these symbols, use the command @code{sharedlibrary
10485 @var{filename}}. The base address of the shared library is determined
10486 automatically by @value{GDBN} and need not be specified.
10488 To display or set the threshold, use the commands:
10491 @kindex set auto-solib-limit
10492 @item set auto-solib-limit @var{threshold}
10493 Set the autoloading size threshold, in an integral number of megabytes.
10494 If @var{threshold} is nonzero and shared library autoloading is enabled,
10495 symbols from all shared object libraries will be loaded until the total
10496 size of the loaded shared library symbols exceeds this threshold.
10497 Otherwise, symbols must be loaded manually, using the
10498 @code{sharedlibrary} command. The default threshold is 100 (i.e.@: 100
10501 @kindex show auto-solib-limit
10502 @item show auto-solib-limit
10503 Display the current autoloading size threshold, in megabytes.
10506 Shared libraries are also supported in many cross or remote debugging
10507 configurations. A copy of the target's libraries need to be present on the
10508 host system; they need to be the same as the target libraries, although the
10509 copies on the target can be stripped as long as the copies on the host are
10512 You need to tell @value{GDBN} where the target libraries are, so that it can
10513 load the correct copies---otherwise, it may try to load the host's libraries.
10514 @value{GDBN} has two variables to specify the search directories for target
10518 @kindex set solib-absolute-prefix
10519 @item set solib-absolute-prefix @var{path}
10520 If this variable is set, @var{path} will be used as a prefix for any
10521 absolute shared library paths; many runtime loaders store the absolute
10522 paths to the shared library in the target program's memory. If you use
10523 @samp{solib-absolute-prefix} to find shared libraries, they need to be laid
10524 out in the same way that they are on the target, with e.g.@: a
10525 @file{/usr/lib} hierarchy under @var{path}.
10527 You can set the default value of @samp{solib-absolute-prefix} by using the
10528 configure-time @samp{--with-sysroot} option.
10530 @kindex show solib-absolute-prefix
10531 @item show solib-absolute-prefix
10532 Display the current shared library prefix.
10534 @kindex set solib-search-path
10535 @item set solib-search-path @var{path}
10536 If this variable is set, @var{path} is a colon-separated list of directories
10537 to search for shared libraries. @samp{solib-search-path} is used after
10538 @samp{solib-absolute-prefix} fails to locate the library, or if the path to
10539 the library is relative instead of absolute. If you want to use
10540 @samp{solib-search-path} instead of @samp{solib-absolute-prefix}, be sure to
10541 set @samp{solib-absolute-prefix} to a nonexistant directory to prevent
10542 @value{GDBN} from finding your host's libraries.
10544 @kindex show solib-search-path
10545 @item show solib-search-path
10546 Display the current shared library search path.
10550 @node Separate Debug Files
10551 @section Debugging Information in Separate Files
10552 @cindex separate debugging information files
10553 @cindex debugging information in separate files
10554 @cindex @file{.debug} subdirectories
10555 @cindex debugging information directory, global
10556 @cindex global debugging information directory
10558 @value{GDBN} allows you to put a program's debugging information in a
10559 file separate from the executable itself, in a way that allows
10560 @value{GDBN} to find and load the debugging information automatically.
10561 Since debugging information can be very large --- sometimes larger
10562 than the executable code itself --- some systems distribute debugging
10563 information for their executables in separate files, which users can
10564 install only when they need to debug a problem.
10566 If an executable's debugging information has been extracted to a
10567 separate file, the executable should contain a @dfn{debug link} giving
10568 the name of the debugging information file (with no directory
10569 components), and a checksum of its contents. (The exact form of a
10570 debug link is described below.) If the full name of the directory
10571 containing the executable is @var{execdir}, and the executable has a
10572 debug link that specifies the name @var{debugfile}, then @value{GDBN}
10573 will automatically search for the debugging information file in three
10578 the directory containing the executable file (that is, it will look
10579 for a file named @file{@var{execdir}/@var{debugfile}},
10581 a subdirectory of that directory named @file{.debug} (that is, the
10582 file @file{@var{execdir}/.debug/@var{debugfile}}, and
10584 a subdirectory of the global debug file directory that includes the
10585 executable's full path, and the name from the link (that is, the file
10586 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
10587 @var{globaldebugdir} is the global debug file directory, and
10588 @var{execdir} has been turned into a relative path).
10591 @value{GDBN} checks under each of these names for a debugging
10592 information file whose checksum matches that given in the link, and
10593 reads the debugging information from the first one it finds.
10595 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
10596 which has a link containing the name @file{ls.debug}, and the global
10597 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
10598 for debug information in @file{/usr/bin/ls.debug},
10599 @file{/usr/bin/.debug/ls.debug}, and
10600 @file{/usr/lib/debug/usr/bin/ls.debug}.
10602 You can set the global debugging info directory's name, and view the
10603 name @value{GDBN} is currently using.
10607 @kindex set debug-file-directory
10608 @item set debug-file-directory @var{directory}
10609 Set the directory which @value{GDBN} searches for separate debugging
10610 information files to @var{directory}.
10612 @kindex show debug-file-directory
10613 @item show debug-file-directory
10614 Show the directory @value{GDBN} searches for separate debugging
10619 @cindex @code{.gnu_debuglink} sections
10620 @cindex debug links
10621 A debug link is a special section of the executable file named
10622 @code{.gnu_debuglink}. The section must contain:
10626 A filename, with any leading directory components removed, followed by
10629 zero to three bytes of padding, as needed to reach the next four-byte
10630 boundary within the section, and
10632 a four-byte CRC checksum, stored in the same endianness used for the
10633 executable file itself. The checksum is computed on the debugging
10634 information file's full contents by the function given below, passing
10635 zero as the @var{crc} argument.
10638 Any executable file format can carry a debug link, as long as it can
10639 contain a section named @code{.gnu_debuglink} with the contents
10642 The debugging information file itself should be an ordinary
10643 executable, containing a full set of linker symbols, sections, and
10644 debugging information. The sections of the debugging information file
10645 should have the same names, addresses and sizes as the original file,
10646 but they need not contain any data --- much like a @code{.bss} section
10647 in an ordinary executable.
10649 As of December 2002, there is no standard GNU utility to produce
10650 separated executable / debugging information file pairs. Ulrich
10651 Drepper's @file{elfutils} package, starting with version 0.53,
10652 contains a version of the @code{strip} command such that the command
10653 @kbd{strip foo -f foo.debug} removes the debugging information from
10654 the executable file @file{foo}, places it in the file
10655 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
10657 Since there are many different ways to compute CRC's (different
10658 polynomials, reversals, byte ordering, etc.), the simplest way to
10659 describe the CRC used in @code{.gnu_debuglink} sections is to give the
10660 complete code for a function that computes it:
10662 @kindex gnu_debuglink_crc32
10665 gnu_debuglink_crc32 (unsigned long crc,
10666 unsigned char *buf, size_t len)
10668 static const unsigned long crc32_table[256] =
10670 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
10671 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
10672 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
10673 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
10674 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
10675 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
10676 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
10677 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
10678 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
10679 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
10680 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
10681 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
10682 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
10683 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
10684 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
10685 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
10686 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
10687 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
10688 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
10689 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
10690 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
10691 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
10692 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
10693 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
10694 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
10695 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
10696 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
10697 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
10698 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
10699 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
10700 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
10701 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
10702 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
10703 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
10704 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
10705 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
10706 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
10707 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
10708 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
10709 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
10710 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
10711 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
10712 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
10713 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
10714 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
10715 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
10716 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
10717 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
10718 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
10719 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
10720 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
10723 unsigned char *end;
10725 crc = ~crc & 0xffffffff;
10726 for (end = buf + len; buf < end; ++buf)
10727 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
10728 return ~crc & 0xffffffff;
10733 @node Symbol Errors
10734 @section Errors reading symbol files
10736 While reading a symbol file, @value{GDBN} occasionally encounters problems,
10737 such as symbol types it does not recognize, or known bugs in compiler
10738 output. By default, @value{GDBN} does not notify you of such problems, since
10739 they are relatively common and primarily of interest to people
10740 debugging compilers. If you are interested in seeing information
10741 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
10742 only one message about each such type of problem, no matter how many
10743 times the problem occurs; or you can ask @value{GDBN} to print more messages,
10744 to see how many times the problems occur, with the @code{set
10745 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
10748 The messages currently printed, and their meanings, include:
10751 @item inner block not inside outer block in @var{symbol}
10753 The symbol information shows where symbol scopes begin and end
10754 (such as at the start of a function or a block of statements). This
10755 error indicates that an inner scope block is not fully contained
10756 in its outer scope blocks.
10758 @value{GDBN} circumvents the problem by treating the inner block as if it had
10759 the same scope as the outer block. In the error message, @var{symbol}
10760 may be shown as ``@code{(don't know)}'' if the outer block is not a
10763 @item block at @var{address} out of order
10765 The symbol information for symbol scope blocks should occur in
10766 order of increasing addresses. This error indicates that it does not
10769 @value{GDBN} does not circumvent this problem, and has trouble
10770 locating symbols in the source file whose symbols it is reading. (You
10771 can often determine what source file is affected by specifying
10772 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
10775 @item bad block start address patched
10777 The symbol information for a symbol scope block has a start address
10778 smaller than the address of the preceding source line. This is known
10779 to occur in the SunOS 4.1.1 (and earlier) C compiler.
10781 @value{GDBN} circumvents the problem by treating the symbol scope block as
10782 starting on the previous source line.
10784 @item bad string table offset in symbol @var{n}
10787 Symbol number @var{n} contains a pointer into the string table which is
10788 larger than the size of the string table.
10790 @value{GDBN} circumvents the problem by considering the symbol to have the
10791 name @code{foo}, which may cause other problems if many symbols end up
10794 @item unknown symbol type @code{0x@var{nn}}
10796 The symbol information contains new data types that @value{GDBN} does
10797 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
10798 uncomprehended information, in hexadecimal.
10800 @value{GDBN} circumvents the error by ignoring this symbol information.
10801 This usually allows you to debug your program, though certain symbols
10802 are not accessible. If you encounter such a problem and feel like
10803 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
10804 on @code{complain}, then go up to the function @code{read_dbx_symtab}
10805 and examine @code{*bufp} to see the symbol.
10807 @item stub type has NULL name
10809 @value{GDBN} could not find the full definition for a struct or class.
10811 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
10812 The symbol information for a C@t{++} member function is missing some
10813 information that recent versions of the compiler should have output for
10816 @item info mismatch between compiler and debugger
10818 @value{GDBN} could not parse a type specification output by the compiler.
10823 @chapter Specifying a Debugging Target
10825 @cindex debugging target
10828 A @dfn{target} is the execution environment occupied by your program.
10830 Often, @value{GDBN} runs in the same host environment as your program;
10831 in that case, the debugging target is specified as a side effect when
10832 you use the @code{file} or @code{core} commands. When you need more
10833 flexibility---for example, running @value{GDBN} on a physically separate
10834 host, or controlling a standalone system over a serial port or a
10835 realtime system over a TCP/IP connection---you can use the @code{target}
10836 command to specify one of the target types configured for @value{GDBN}
10837 (@pxref{Target Commands, ,Commands for managing targets}).
10840 * Active Targets:: Active targets
10841 * Target Commands:: Commands for managing targets
10842 * Byte Order:: Choosing target byte order
10843 * Remote:: Remote debugging
10844 * KOD:: Kernel Object Display
10848 @node Active Targets
10849 @section Active targets
10851 @cindex stacking targets
10852 @cindex active targets
10853 @cindex multiple targets
10855 There are three classes of targets: processes, core files, and
10856 executable files. @value{GDBN} can work concurrently on up to three
10857 active targets, one in each class. This allows you to (for example)
10858 start a process and inspect its activity without abandoning your work on
10861 For example, if you execute @samp{gdb a.out}, then the executable file
10862 @code{a.out} is the only active target. If you designate a core file as
10863 well---presumably from a prior run that crashed and coredumped---then
10864 @value{GDBN} has two active targets and uses them in tandem, looking
10865 first in the corefile target, then in the executable file, to satisfy
10866 requests for memory addresses. (Typically, these two classes of target
10867 are complementary, since core files contain only a program's
10868 read-write memory---variables and so on---plus machine status, while
10869 executable files contain only the program text and initialized data.)
10871 When you type @code{run}, your executable file becomes an active process
10872 target as well. When a process target is active, all @value{GDBN}
10873 commands requesting memory addresses refer to that target; addresses in
10874 an active core file or executable file target are obscured while the
10875 process target is active.
10877 Use the @code{core-file} and @code{exec-file} commands to select a new
10878 core file or executable target (@pxref{Files, ,Commands to specify
10879 files}). To specify as a target a process that is already running, use
10880 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
10883 @node Target Commands
10884 @section Commands for managing targets
10887 @item target @var{type} @var{parameters}
10888 Connects the @value{GDBN} host environment to a target machine or
10889 process. A target is typically a protocol for talking to debugging
10890 facilities. You use the argument @var{type} to specify the type or
10891 protocol of the target machine.
10893 Further @var{parameters} are interpreted by the target protocol, but
10894 typically include things like device names or host names to connect
10895 with, process numbers, and baud rates.
10897 The @code{target} command does not repeat if you press @key{RET} again
10898 after executing the command.
10900 @kindex help target
10902 Displays the names of all targets available. To display targets
10903 currently selected, use either @code{info target} or @code{info files}
10904 (@pxref{Files, ,Commands to specify files}).
10906 @item help target @var{name}
10907 Describe a particular target, including any parameters necessary to
10910 @kindex set gnutarget
10911 @item set gnutarget @var{args}
10912 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
10913 knows whether it is reading an @dfn{executable},
10914 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
10915 with the @code{set gnutarget} command. Unlike most @code{target} commands,
10916 with @code{gnutarget} the @code{target} refers to a program, not a machine.
10919 @emph{Warning:} To specify a file format with @code{set gnutarget},
10920 you must know the actual BFD name.
10924 @xref{Files, , Commands to specify files}.
10926 @kindex show gnutarget
10927 @item show gnutarget
10928 Use the @code{show gnutarget} command to display what file format
10929 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
10930 @value{GDBN} will determine the file format for each file automatically,
10931 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
10934 @cindex common targets
10935 Here are some common targets (available, or not, depending on the GDB
10940 @item target exec @var{program}
10941 @cindex executable file target
10942 An executable file. @samp{target exec @var{program}} is the same as
10943 @samp{exec-file @var{program}}.
10945 @item target core @var{filename}
10946 @cindex core dump file target
10947 A core dump file. @samp{target core @var{filename}} is the same as
10948 @samp{core-file @var{filename}}.
10950 @item target remote @var{dev}
10951 @cindex remote target
10952 Remote serial target in GDB-specific protocol. The argument @var{dev}
10953 specifies what serial device to use for the connection (e.g.
10954 @file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote}
10955 supports the @code{load} command. This is only useful if you have
10956 some other way of getting the stub to the target system, and you can put
10957 it somewhere in memory where it won't get clobbered by the download.
10960 @cindex built-in simulator target
10961 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
10969 works; however, you cannot assume that a specific memory map, device
10970 drivers, or even basic I/O is available, although some simulators do
10971 provide these. For info about any processor-specific simulator details,
10972 see the appropriate section in @ref{Embedded Processors, ,Embedded
10977 Some configurations may include these targets as well:
10981 @item target nrom @var{dev}
10982 @cindex NetROM ROM emulator target
10983 NetROM ROM emulator. This target only supports downloading.
10987 Different targets are available on different configurations of @value{GDBN};
10988 your configuration may have more or fewer targets.
10990 Many remote targets require you to download the executable's code
10991 once you've successfully established a connection.
10995 @kindex load @var{filename}
10996 @item load @var{filename}
10997 Depending on what remote debugging facilities are configured into
10998 @value{GDBN}, the @code{load} command may be available. Where it exists, it
10999 is meant to make @var{filename} (an executable) available for debugging
11000 on the remote system---by downloading, or dynamic linking, for example.
11001 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
11002 the @code{add-symbol-file} command.
11004 If your @value{GDBN} does not have a @code{load} command, attempting to
11005 execute it gets the error message ``@code{You can't do that when your
11006 target is @dots{}}''
11008 The file is loaded at whatever address is specified in the executable.
11009 For some object file formats, you can specify the load address when you
11010 link the program; for other formats, like a.out, the object file format
11011 specifies a fixed address.
11012 @c FIXME! This would be a good place for an xref to the GNU linker doc.
11014 @code{load} does not repeat if you press @key{RET} again after using it.
11018 @section Choosing target byte order
11020 @cindex choosing target byte order
11021 @cindex target byte order
11023 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
11024 offer the ability to run either big-endian or little-endian byte
11025 orders. Usually the executable or symbol will include a bit to
11026 designate the endian-ness, and you will not need to worry about
11027 which to use. However, you may still find it useful to adjust
11028 @value{GDBN}'s idea of processor endian-ness manually.
11032 @item set endian big
11033 Instruct @value{GDBN} to assume the target is big-endian.
11035 @item set endian little
11036 Instruct @value{GDBN} to assume the target is little-endian.
11038 @item set endian auto
11039 Instruct @value{GDBN} to use the byte order associated with the
11043 Display @value{GDBN}'s current idea of the target byte order.
11047 Note that these commands merely adjust interpretation of symbolic
11048 data on the host, and that they have absolutely no effect on the
11052 @section Remote debugging
11053 @cindex remote debugging
11055 If you are trying to debug a program running on a machine that cannot run
11056 @value{GDBN} in the usual way, it is often useful to use remote debugging.
11057 For example, you might use remote debugging on an operating system kernel,
11058 or on a small system which does not have a general purpose operating system
11059 powerful enough to run a full-featured debugger.
11061 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
11062 to make this work with particular debugging targets. In addition,
11063 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
11064 but not specific to any particular target system) which you can use if you
11065 write the remote stubs---the code that runs on the remote system to
11066 communicate with @value{GDBN}.
11068 Other remote targets may be available in your
11069 configuration of @value{GDBN}; use @code{help target} to list them.
11072 @section Kernel Object Display
11073 @cindex kernel object display
11076 Some targets support kernel object display. Using this facility,
11077 @value{GDBN} communicates specially with the underlying operating system
11078 and can display information about operating system-level objects such as
11079 mutexes and other synchronization objects. Exactly which objects can be
11080 displayed is determined on a per-OS basis.
11083 Use the @code{set os} command to set the operating system. This tells
11084 @value{GDBN} which kernel object display module to initialize:
11087 (@value{GDBP}) set os cisco
11091 The associated command @code{show os} displays the operating system
11092 set with the @code{set os} command; if no operating system has been
11093 set, @code{show os} will display an empty string @samp{""}.
11095 If @code{set os} succeeds, @value{GDBN} will display some information
11096 about the operating system, and will create a new @code{info} command
11097 which can be used to query the target. The @code{info} command is named
11098 after the operating system:
11102 (@value{GDBP}) info cisco
11103 List of Cisco Kernel Objects
11105 any Any and all objects
11108 Further subcommands can be used to query about particular objects known
11111 There is currently no way to determine whether a given operating
11112 system is supported other than to try setting it with @kbd{set os
11113 @var{name}}, where @var{name} is the name of the operating system you
11117 @node Remote Debugging
11118 @chapter Debugging remote programs
11121 * Connecting:: Connecting to a remote target
11122 * Server:: Using the gdbserver program
11123 * NetWare:: Using the gdbserve.nlm program
11124 * Remote configuration:: Remote configuration
11125 * remote stub:: Implementing a remote stub
11129 @section Connecting to a remote target
11131 On the @value{GDBN} host machine, you will need an unstripped copy of
11132 your program, since @value{GDBN} needs symobl and debugging information.
11133 Start up @value{GDBN} as usual, using the name of the local copy of your
11134 program as the first argument.
11136 @cindex serial line, @code{target remote}
11137 If you're using a serial line, you may want to give @value{GDBN} the
11138 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
11139 before the @code{target} command.
11141 After that, use @code{target remote} to establish communications with
11142 the target machine. Its argument specifies how to communicate---either
11143 via a devicename attached to a direct serial line, or a TCP or UDP port
11144 (possibly to a terminal server which in turn has a serial line to the
11145 target). For example, to use a serial line connected to the device
11146 named @file{/dev/ttyb}:
11149 target remote /dev/ttyb
11152 @cindex TCP port, @code{target remote}
11153 To use a TCP connection, use an argument of the form
11154 @code{@var{host}:@var{port}} or @code{tcp:@var{host}:@var{port}}.
11155 For example, to connect to port 2828 on a
11156 terminal server named @code{manyfarms}:
11159 target remote manyfarms:2828
11162 If your remote target is actually running on the same machine as
11163 your debugger session (e.g.@: a simulator of your target running on
11164 the same host), you can omit the hostname. For example, to connect
11165 to port 1234 on your local machine:
11168 target remote :1234
11172 Note that the colon is still required here.
11174 @cindex UDP port, @code{target remote}
11175 To use a UDP connection, use an argument of the form
11176 @code{udp:@var{host}:@var{port}}. For example, to connect to UDP port 2828
11177 on a terminal server named @code{manyfarms}:
11180 target remote udp:manyfarms:2828
11183 When using a UDP connection for remote debugging, you should keep in mind
11184 that the `U' stands for ``Unreliable''. UDP can silently drop packets on
11185 busy or unreliable networks, which will cause havoc with your debugging
11188 Now you can use all the usual commands to examine and change data and to
11189 step and continue the remote program.
11191 @cindex interrupting remote programs
11192 @cindex remote programs, interrupting
11193 Whenever @value{GDBN} is waiting for the remote program, if you type the
11194 interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
11195 program. This may or may not succeed, depending in part on the hardware
11196 and the serial drivers the remote system uses. If you type the
11197 interrupt character once again, @value{GDBN} displays this prompt:
11200 Interrupted while waiting for the program.
11201 Give up (and stop debugging it)? (y or n)
11204 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
11205 (If you decide you want to try again later, you can use @samp{target
11206 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
11207 goes back to waiting.
11210 @kindex detach (remote)
11212 When you have finished debugging the remote program, you can use the
11213 @code{detach} command to release it from @value{GDBN} control.
11214 Detaching from the target normally resumes its execution, but the results
11215 will depend on your particular remote stub. After the @code{detach}
11216 command, @value{GDBN} is free to connect to another target.
11220 The @code{disconnect} command behaves like @code{detach}, except that
11221 the target is generally not resumed. It will wait for @value{GDBN}
11222 (this instance or another one) to connect and continue debugging. After
11223 the @code{disconnect} command, @value{GDBN} is again free to connect to
11228 @section Using the @code{gdbserver} program
11231 @cindex remote connection without stubs
11232 @code{gdbserver} is a control program for Unix-like systems, which
11233 allows you to connect your program with a remote @value{GDBN} via
11234 @code{target remote}---but without linking in the usual debugging stub.
11236 @code{gdbserver} is not a complete replacement for the debugging stubs,
11237 because it requires essentially the same operating-system facilities
11238 that @value{GDBN} itself does. In fact, a system that can run
11239 @code{gdbserver} to connect to a remote @value{GDBN} could also run
11240 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
11241 because it is a much smaller program than @value{GDBN} itself. It is
11242 also easier to port than all of @value{GDBN}, so you may be able to get
11243 started more quickly on a new system by using @code{gdbserver}.
11244 Finally, if you develop code for real-time systems, you may find that
11245 the tradeoffs involved in real-time operation make it more convenient to
11246 do as much development work as possible on another system, for example
11247 by cross-compiling. You can use @code{gdbserver} to make a similar
11248 choice for debugging.
11250 @value{GDBN} and @code{gdbserver} communicate via either a serial line
11251 or a TCP connection, using the standard @value{GDBN} remote serial
11255 @item On the target machine,
11256 you need to have a copy of the program you want to debug.
11257 @code{gdbserver} does not need your program's symbol table, so you can
11258 strip the program if necessary to save space. @value{GDBN} on the host
11259 system does all the symbol handling.
11261 To use the server, you must tell it how to communicate with @value{GDBN};
11262 the name of your program; and the arguments for your program. The usual
11266 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
11269 @var{comm} is either a device name (to use a serial line) or a TCP
11270 hostname and portnumber. For example, to debug Emacs with the argument
11271 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
11275 target> gdbserver /dev/com1 emacs foo.txt
11278 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
11281 To use a TCP connection instead of a serial line:
11284 target> gdbserver host:2345 emacs foo.txt
11287 The only difference from the previous example is the first argument,
11288 specifying that you are communicating with the host @value{GDBN} via
11289 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
11290 expect a TCP connection from machine @samp{host} to local TCP port 2345.
11291 (Currently, the @samp{host} part is ignored.) You can choose any number
11292 you want for the port number as long as it does not conflict with any
11293 TCP ports already in use on the target system (for example, @code{23} is
11294 reserved for @code{telnet}).@footnote{If you choose a port number that
11295 conflicts with another service, @code{gdbserver} prints an error message
11296 and exits.} You must use the same port number with the host @value{GDBN}
11297 @code{target remote} command.
11299 On some targets, @code{gdbserver} can also attach to running programs.
11300 This is accomplished via the @code{--attach} argument. The syntax is:
11303 target> gdbserver @var{comm} --attach @var{pid}
11306 @var{pid} is the process ID of a currently running process. It isn't necessary
11307 to point @code{gdbserver} at a binary for the running process.
11310 @cindex attach to a program by name
11311 You can debug processes by name instead of process ID if your target has the
11312 @code{pidof} utility:
11315 target> gdbserver @var{comm} --attach `pidof @var{PROGRAM}`
11318 In case more than one copy of @var{PROGRAM} is running, or @var{PROGRAM}
11319 has multiple threads, most versions of @code{pidof} support the
11320 @code{-s} option to only return the first process ID.
11322 @item On the host machine,
11323 connect to your target (@pxref{Connecting,,Connecting to a remote target}).
11324 For TCP connections, you must start up @code{gdbserver} prior to using
11325 the @code{target remote} command. Otherwise you may get an error whose
11326 text depends on the host system, but which usually looks something like
11327 @samp{Connection refused}. You don't need to use the @code{load}
11328 command in @value{GDBN} when using gdbserver, since the program is
11329 already on the target.
11334 @section Using the @code{gdbserve.nlm} program
11336 @kindex gdbserve.nlm
11337 @code{gdbserve.nlm} is a control program for NetWare systems, which
11338 allows you to connect your program with a remote @value{GDBN} via
11339 @code{target remote}.
11341 @value{GDBN} and @code{gdbserve.nlm} communicate via a serial line,
11342 using the standard @value{GDBN} remote serial protocol.
11345 @item On the target machine,
11346 you need to have a copy of the program you want to debug.
11347 @code{gdbserve.nlm} does not need your program's symbol table, so you
11348 can strip the program if necessary to save space. @value{GDBN} on the
11349 host system does all the symbol handling.
11351 To use the server, you must tell it how to communicate with
11352 @value{GDBN}; the name of your program; and the arguments for your
11353 program. The syntax is:
11356 load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ]
11357 [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ]
11360 @var{board} and @var{port} specify the serial line; @var{baud} specifies
11361 the baud rate used by the connection. @var{port} and @var{node} default
11362 to 0, @var{baud} defaults to 9600@dmn{bps}.
11364 For example, to debug Emacs with the argument @samp{foo.txt}and
11365 communicate with @value{GDBN} over serial port number 2 or board 1
11366 using a 19200@dmn{bps} connection:
11369 load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
11373 On the @value{GDBN} host machine, connect to your target (@pxref{Connecting,,
11374 Connecting to a remote target}).
11378 @node Remote configuration
11379 @section Remote configuration
11381 The following configuration options are available when debugging remote
11385 @kindex set remote hardware-watchpoint-limit
11386 @kindex set remote hardware-breakpoint-limit
11387 @anchor{set remote hardware-watchpoint-limit}
11388 @anchor{set remote hardware-breakpoint-limit}
11389 @item set remote hardware-watchpoint-limit @var{limit}
11390 @itemx set remote hardware-breakpoint-limit @var{limit}
11391 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
11392 watchpoints. A limit of -1, the default, is treated as unlimited.
11396 @section Implementing a remote stub
11398 @cindex debugging stub, example
11399 @cindex remote stub, example
11400 @cindex stub example, remote debugging
11401 The stub files provided with @value{GDBN} implement the target side of the
11402 communication protocol, and the @value{GDBN} side is implemented in the
11403 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
11404 these subroutines to communicate, and ignore the details. (If you're
11405 implementing your own stub file, you can still ignore the details: start
11406 with one of the existing stub files. @file{sparc-stub.c} is the best
11407 organized, and therefore the easiest to read.)
11409 @cindex remote serial debugging, overview
11410 To debug a program running on another machine (the debugging
11411 @dfn{target} machine), you must first arrange for all the usual
11412 prerequisites for the program to run by itself. For example, for a C
11417 A startup routine to set up the C runtime environment; these usually
11418 have a name like @file{crt0}. The startup routine may be supplied by
11419 your hardware supplier, or you may have to write your own.
11422 A C subroutine library to support your program's
11423 subroutine calls, notably managing input and output.
11426 A way of getting your program to the other machine---for example, a
11427 download program. These are often supplied by the hardware
11428 manufacturer, but you may have to write your own from hardware
11432 The next step is to arrange for your program to use a serial port to
11433 communicate with the machine where @value{GDBN} is running (the @dfn{host}
11434 machine). In general terms, the scheme looks like this:
11438 @value{GDBN} already understands how to use this protocol; when everything
11439 else is set up, you can simply use the @samp{target remote} command
11440 (@pxref{Targets,,Specifying a Debugging Target}).
11442 @item On the target,
11443 you must link with your program a few special-purpose subroutines that
11444 implement the @value{GDBN} remote serial protocol. The file containing these
11445 subroutines is called a @dfn{debugging stub}.
11447 On certain remote targets, you can use an auxiliary program
11448 @code{gdbserver} instead of linking a stub into your program.
11449 @xref{Server,,Using the @code{gdbserver} program}, for details.
11452 The debugging stub is specific to the architecture of the remote
11453 machine; for example, use @file{sparc-stub.c} to debug programs on
11456 @cindex remote serial stub list
11457 These working remote stubs are distributed with @value{GDBN}:
11462 @cindex @file{i386-stub.c}
11465 For Intel 386 and compatible architectures.
11468 @cindex @file{m68k-stub.c}
11469 @cindex Motorola 680x0
11471 For Motorola 680x0 architectures.
11474 @cindex @file{sh-stub.c}
11477 For Renesas SH architectures.
11480 @cindex @file{sparc-stub.c}
11482 For @sc{sparc} architectures.
11484 @item sparcl-stub.c
11485 @cindex @file{sparcl-stub.c}
11488 For Fujitsu @sc{sparclite} architectures.
11492 The @file{README} file in the @value{GDBN} distribution may list other
11493 recently added stubs.
11496 * Stub Contents:: What the stub can do for you
11497 * Bootstrapping:: What you must do for the stub
11498 * Debug Session:: Putting it all together
11501 @node Stub Contents
11502 @subsection What the stub can do for you
11504 @cindex remote serial stub
11505 The debugging stub for your architecture supplies these three
11509 @item set_debug_traps
11510 @findex set_debug_traps
11511 @cindex remote serial stub, initialization
11512 This routine arranges for @code{handle_exception} to run when your
11513 program stops. You must call this subroutine explicitly near the
11514 beginning of your program.
11516 @item handle_exception
11517 @findex handle_exception
11518 @cindex remote serial stub, main routine
11519 This is the central workhorse, but your program never calls it
11520 explicitly---the setup code arranges for @code{handle_exception} to
11521 run when a trap is triggered.
11523 @code{handle_exception} takes control when your program stops during
11524 execution (for example, on a breakpoint), and mediates communications
11525 with @value{GDBN} on the host machine. This is where the communications
11526 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
11527 representative on the target machine. It begins by sending summary
11528 information on the state of your program, then continues to execute,
11529 retrieving and transmitting any information @value{GDBN} needs, until you
11530 execute a @value{GDBN} command that makes your program resume; at that point,
11531 @code{handle_exception} returns control to your own code on the target
11535 @cindex @code{breakpoint} subroutine, remote
11536 Use this auxiliary subroutine to make your program contain a
11537 breakpoint. Depending on the particular situation, this may be the only
11538 way for @value{GDBN} to get control. For instance, if your target
11539 machine has some sort of interrupt button, you won't need to call this;
11540 pressing the interrupt button transfers control to
11541 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
11542 simply receiving characters on the serial port may also trigger a trap;
11543 again, in that situation, you don't need to call @code{breakpoint} from
11544 your own program---simply running @samp{target remote} from the host
11545 @value{GDBN} session gets control.
11547 Call @code{breakpoint} if none of these is true, or if you simply want
11548 to make certain your program stops at a predetermined point for the
11549 start of your debugging session.
11552 @node Bootstrapping
11553 @subsection What you must do for the stub
11555 @cindex remote stub, support routines
11556 The debugging stubs that come with @value{GDBN} are set up for a particular
11557 chip architecture, but they have no information about the rest of your
11558 debugging target machine.
11560 First of all you need to tell the stub how to communicate with the
11564 @item int getDebugChar()
11565 @findex getDebugChar
11566 Write this subroutine to read a single character from the serial port.
11567 It may be identical to @code{getchar} for your target system; a
11568 different name is used to allow you to distinguish the two if you wish.
11570 @item void putDebugChar(int)
11571 @findex putDebugChar
11572 Write this subroutine to write a single character to the serial port.
11573 It may be identical to @code{putchar} for your target system; a
11574 different name is used to allow you to distinguish the two if you wish.
11577 @cindex control C, and remote debugging
11578 @cindex interrupting remote targets
11579 If you want @value{GDBN} to be able to stop your program while it is
11580 running, you need to use an interrupt-driven serial driver, and arrange
11581 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
11582 character). That is the character which @value{GDBN} uses to tell the
11583 remote system to stop.
11585 Getting the debugging target to return the proper status to @value{GDBN}
11586 probably requires changes to the standard stub; one quick and dirty way
11587 is to just execute a breakpoint instruction (the ``dirty'' part is that
11588 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
11590 Other routines you need to supply are:
11593 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
11594 @findex exceptionHandler
11595 Write this function to install @var{exception_address} in the exception
11596 handling tables. You need to do this because the stub does not have any
11597 way of knowing what the exception handling tables on your target system
11598 are like (for example, the processor's table might be in @sc{rom},
11599 containing entries which point to a table in @sc{ram}).
11600 @var{exception_number} is the exception number which should be changed;
11601 its meaning is architecture-dependent (for example, different numbers
11602 might represent divide by zero, misaligned access, etc). When this
11603 exception occurs, control should be transferred directly to
11604 @var{exception_address}, and the processor state (stack, registers,
11605 and so on) should be just as it is when a processor exception occurs. So if
11606 you want to use a jump instruction to reach @var{exception_address}, it
11607 should be a simple jump, not a jump to subroutine.
11609 For the 386, @var{exception_address} should be installed as an interrupt
11610 gate so that interrupts are masked while the handler runs. The gate
11611 should be at privilege level 0 (the most privileged level). The
11612 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
11613 help from @code{exceptionHandler}.
11615 @item void flush_i_cache()
11616 @findex flush_i_cache
11617 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
11618 instruction cache, if any, on your target machine. If there is no
11619 instruction cache, this subroutine may be a no-op.
11621 On target machines that have instruction caches, @value{GDBN} requires this
11622 function to make certain that the state of your program is stable.
11626 You must also make sure this library routine is available:
11629 @item void *memset(void *, int, int)
11631 This is the standard library function @code{memset} that sets an area of
11632 memory to a known value. If you have one of the free versions of
11633 @code{libc.a}, @code{memset} can be found there; otherwise, you must
11634 either obtain it from your hardware manufacturer, or write your own.
11637 If you do not use the GNU C compiler, you may need other standard
11638 library subroutines as well; this varies from one stub to another,
11639 but in general the stubs are likely to use any of the common library
11640 subroutines which @code{@value{GCC}} generates as inline code.
11643 @node Debug Session
11644 @subsection Putting it all together
11646 @cindex remote serial debugging summary
11647 In summary, when your program is ready to debug, you must follow these
11652 Make sure you have defined the supporting low-level routines
11653 (@pxref{Bootstrapping,,What you must do for the stub}):
11655 @code{getDebugChar}, @code{putDebugChar},
11656 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
11660 Insert these lines near the top of your program:
11668 For the 680x0 stub only, you need to provide a variable called
11669 @code{exceptionHook}. Normally you just use:
11672 void (*exceptionHook)() = 0;
11676 but if before calling @code{set_debug_traps}, you set it to point to a
11677 function in your program, that function is called when
11678 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
11679 error). The function indicated by @code{exceptionHook} is called with
11680 one parameter: an @code{int} which is the exception number.
11683 Compile and link together: your program, the @value{GDBN} debugging stub for
11684 your target architecture, and the supporting subroutines.
11687 Make sure you have a serial connection between your target machine and
11688 the @value{GDBN} host, and identify the serial port on the host.
11691 @c The "remote" target now provides a `load' command, so we should
11692 @c document that. FIXME.
11693 Download your program to your target machine (or get it there by
11694 whatever means the manufacturer provides), and start it.
11697 Start @value{GDBN} on the host, and connect to the target
11698 (@pxref{Connecting,,Connecting to a remote target}).
11702 @node Configurations
11703 @chapter Configuration-Specific Information
11705 While nearly all @value{GDBN} commands are available for all native and
11706 cross versions of the debugger, there are some exceptions. This chapter
11707 describes things that are only available in certain configurations.
11709 There are three major categories of configurations: native
11710 configurations, where the host and target are the same, embedded
11711 operating system configurations, which are usually the same for several
11712 different processor architectures, and bare embedded processors, which
11713 are quite different from each other.
11718 * Embedded Processors::
11725 This section describes details specific to particular native
11730 * BSD libkvm Interface:: Debugging BSD kernel memory images
11731 * SVR4 Process Information:: SVR4 process information
11732 * DJGPP Native:: Features specific to the DJGPP port
11733 * Cygwin Native:: Features specific to the Cygwin port
11739 On HP-UX systems, if you refer to a function or variable name that
11740 begins with a dollar sign, @value{GDBN} searches for a user or system
11741 name first, before it searches for a convenience variable.
11743 @node BSD libkvm Interface
11744 @subsection BSD libkvm Interface
11747 @cindex kernel memory image
11748 @cindex kernel crash dump
11750 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
11751 interface that provides a uniform interface for accessing kernel virtual
11752 memory images, including live systems and crash dumps. @value{GDBN}
11753 uses this interface to allow you to debug live kernels and kernel crash
11754 dumps on many native BSD configurations. This is implemented as a
11755 special @code{kvm} debugging target. For debugging a live system, load
11756 the currently running kernel into @value{GDBN} and connect to the
11760 (@value{GDBP}) @b{target kvm}
11763 For debugging crash dumps, provide the file name of the crash dump as an
11767 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
11770 Once connected to the @code{kvm} target, the following commands are
11776 Set current context from pcb address.
11779 Set current context from proc address. This command isn't available on
11780 modern FreeBSD systems.
11783 @node SVR4 Process Information
11784 @subsection SVR4 process information
11787 @cindex process image
11789 Many versions of SVR4 provide a facility called @samp{/proc} that can be
11790 used to examine the image of a running process using file-system
11791 subroutines. If @value{GDBN} is configured for an operating system with
11792 this facility, the command @code{info proc} is available to report on
11793 several kinds of information about the process running your program.
11794 @code{info proc} works only on SVR4 systems that include the
11795 @code{procfs} code. This includes OSF/1 (Digital Unix), Solaris, Irix,
11796 and Unixware, but not HP-UX or @sc{gnu}/Linux, for example.
11801 Summarize available information about the process.
11803 @kindex info proc mappings
11804 @item info proc mappings
11805 Report on the address ranges accessible in the program, with information
11806 on whether your program may read, write, or execute each range.
11808 @comment These sub-options of 'info proc' were not included when
11809 @comment procfs.c was re-written. Keep their descriptions around
11810 @comment against the day when someone finds the time to put them back in.
11811 @kindex info proc times
11812 @item info proc times
11813 Starting time, user CPU time, and system CPU time for your program and
11816 @kindex info proc id
11818 Report on the process IDs related to your program: its own process ID,
11819 the ID of its parent, the process group ID, and the session ID.
11821 @kindex info proc status
11822 @item info proc status
11823 General information on the state of the process. If the process is
11824 stopped, this report includes the reason for stopping, and any signal
11827 @item info proc all
11828 Show all the above information about the process.
11833 @subsection Features for Debugging @sc{djgpp} Programs
11834 @cindex @sc{djgpp} debugging
11835 @cindex native @sc{djgpp} debugging
11836 @cindex MS-DOS-specific commands
11838 @sc{djgpp} is the port of @sc{gnu} development tools to MS-DOS and
11839 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
11840 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
11841 top of real-mode DOS systems and their emulations.
11843 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
11844 defines a few commands specific to the @sc{djgpp} port. This
11845 subsection describes those commands.
11850 This is a prefix of @sc{djgpp}-specific commands which print
11851 information about the target system and important OS structures.
11854 @cindex MS-DOS system info
11855 @cindex free memory information (MS-DOS)
11856 @item info dos sysinfo
11857 This command displays assorted information about the underlying
11858 platform: the CPU type and features, the OS version and flavor, the
11859 DPMI version, and the available conventional and DPMI memory.
11864 @cindex segment descriptor tables
11865 @cindex descriptor tables display
11867 @itemx info dos ldt
11868 @itemx info dos idt
11869 These 3 commands display entries from, respectively, Global, Local,
11870 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
11871 tables are data structures which store a descriptor for each segment
11872 that is currently in use. The segment's selector is an index into a
11873 descriptor table; the table entry for that index holds the
11874 descriptor's base address and limit, and its attributes and access
11877 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
11878 segment (used for both data and the stack), and a DOS segment (which
11879 allows access to DOS/BIOS data structures and absolute addresses in
11880 conventional memory). However, the DPMI host will usually define
11881 additional segments in order to support the DPMI environment.
11883 @cindex garbled pointers
11884 These commands allow to display entries from the descriptor tables.
11885 Without an argument, all entries from the specified table are
11886 displayed. An argument, which should be an integer expression, means
11887 display a single entry whose index is given by the argument. For
11888 example, here's a convenient way to display information about the
11889 debugged program's data segment:
11892 @exdent @code{(@value{GDBP}) info dos ldt $ds}
11893 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
11897 This comes in handy when you want to see whether a pointer is outside
11898 the data segment's limit (i.e.@: @dfn{garbled}).
11900 @cindex page tables display (MS-DOS)
11902 @itemx info dos pte
11903 These two commands display entries from, respectively, the Page
11904 Directory and the Page Tables. Page Directories and Page Tables are
11905 data structures which control how virtual memory addresses are mapped
11906 into physical addresses. A Page Table includes an entry for every
11907 page of memory that is mapped into the program's address space; there
11908 may be several Page Tables, each one holding up to 4096 entries. A
11909 Page Directory has up to 4096 entries, one each for every Page Table
11910 that is currently in use.
11912 Without an argument, @kbd{info dos pde} displays the entire Page
11913 Directory, and @kbd{info dos pte} displays all the entries in all of
11914 the Page Tables. An argument, an integer expression, given to the
11915 @kbd{info dos pde} command means display only that entry from the Page
11916 Directory table. An argument given to the @kbd{info dos pte} command
11917 means display entries from a single Page Table, the one pointed to by
11918 the specified entry in the Page Directory.
11920 @cindex direct memory access (DMA) on MS-DOS
11921 These commands are useful when your program uses @dfn{DMA} (Direct
11922 Memory Access), which needs physical addresses to program the DMA
11925 These commands are supported only with some DPMI servers.
11927 @cindex physical address from linear address
11928 @item info dos address-pte @var{addr}
11929 This command displays the Page Table entry for a specified linear
11930 address. The argument linear address @var{addr} should already have the
11931 appropriate segment's base address added to it, because this command
11932 accepts addresses which may belong to @emph{any} segment. For
11933 example, here's how to display the Page Table entry for the page where
11934 the variable @code{i} is stored:
11937 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
11938 @exdent @code{Page Table entry for address 0x11a00d30:}
11939 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
11943 This says that @code{i} is stored at offset @code{0xd30} from the page
11944 whose physical base address is @code{0x02698000}, and prints all the
11945 attributes of that page.
11947 Note that you must cast the addresses of variables to a @code{char *},
11948 since otherwise the value of @code{__djgpp_base_address}, the base
11949 address of all variables and functions in a @sc{djgpp} program, will
11950 be added using the rules of C pointer arithmetics: if @code{i} is
11951 declared an @code{int}, @value{GDBN} will add 4 times the value of
11952 @code{__djgpp_base_address} to the address of @code{i}.
11954 Here's another example, it displays the Page Table entry for the
11958 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
11959 @exdent @code{Page Table entry for address 0x29110:}
11960 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
11964 (The @code{+ 3} offset is because the transfer buffer's address is the
11965 3rd member of the @code{_go32_info_block} structure.) The output of
11966 this command clearly shows that addresses in conventional memory are
11967 mapped 1:1, i.e.@: the physical and linear addresses are identical.
11969 This command is supported only with some DPMI servers.
11972 @node Cygwin Native
11973 @subsection Features for Debugging MS Windows PE executables
11974 @cindex MS Windows debugging
11975 @cindex native Cygwin debugging
11976 @cindex Cygwin-specific commands
11978 @value{GDBN} supports native debugging of MS Windows programs, including
11979 DLLs with and without symbolic debugging information. There are various
11980 additional Cygwin-specific commands, described in this subsection. The
11981 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
11982 that have no debugging symbols.
11988 This is a prefix of MS Windows specific commands which print
11989 information about the target system and important OS structures.
11991 @item info w32 selector
11992 This command displays information returned by
11993 the Win32 API @code{GetThreadSelectorEntry} function.
11994 It takes an optional argument that is evaluated to
11995 a long value to give the information about this given selector.
11996 Without argument, this command displays information
11997 about the the six segment registers.
12001 This is a Cygwin specific alias of info shared.
12003 @kindex dll-symbols
12005 This command loads symbols from a dll similarly to
12006 add-sym command but without the need to specify a base address.
12008 @kindex set new-console
12009 @item set new-console @var{mode}
12010 If @var{mode} is @code{on} the debuggee will
12011 be started in a new console on next start.
12012 If @var{mode} is @code{off}i, the debuggee will
12013 be started in the same console as the debugger.
12015 @kindex show new-console
12016 @item show new-console
12017 Displays whether a new console is used
12018 when the debuggee is started.
12020 @kindex set new-group
12021 @item set new-group @var{mode}
12022 This boolean value controls whether the debuggee should
12023 start a new group or stay in the same group as the debugger.
12024 This affects the way the Windows OS handles
12027 @kindex show new-group
12028 @item show new-group
12029 Displays current value of new-group boolean.
12031 @kindex set debugevents
12032 @item set debugevents
12033 This boolean value adds debug output concerning events seen by the debugger.
12035 @kindex set debugexec
12036 @item set debugexec
12037 This boolean value adds debug output concerning execute events
12038 seen by the debugger.
12040 @kindex set debugexceptions
12041 @item set debugexceptions
12042 This boolean value adds debug ouptut concerning exception events
12043 seen by the debugger.
12045 @kindex set debugmemory
12046 @item set debugmemory
12047 This boolean value adds debug ouptut concerning memory events
12048 seen by the debugger.
12052 This boolean values specifies whether the debuggee is called
12053 via a shell or directly (default value is on).
12057 Displays if the debuggee will be started with a shell.
12062 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
12065 @node Non-debug DLL symbols
12066 @subsubsection Support for DLLs without debugging symbols
12067 @cindex DLLs with no debugging symbols
12068 @cindex Minimal symbols and DLLs
12070 Very often on windows, some of the DLLs that your program relies on do
12071 not include symbolic debugging information (for example,
12072 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
12073 symbols in a DLL, it relies on the minimal amount of symbolic
12074 information contained in the DLL's export table. This subsubsection
12075 describes working with such symbols, known internally to @value{GDBN} as
12076 ``minimal symbols''.
12078 Note that before the debugged program has started execution, no DLLs
12079 will have been loaded. The easiest way around this problem is simply to
12080 start the program --- either by setting a breakpoint or letting the
12081 program run once to completion. It is also possible to force
12082 @value{GDBN} to load a particular DLL before starting the executable ---
12083 see the shared library information in @pxref{Files} or the
12084 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
12085 explicitly loading symbols from a DLL with no debugging information will
12086 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
12087 which may adversely affect symbol lookup performance.
12089 @subsubsection DLL name prefixes
12091 In keeping with the naming conventions used by the Microsoft debugging
12092 tools, DLL export symbols are made available with a prefix based on the
12093 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
12094 also entered into the symbol table, so @code{CreateFileA} is often
12095 sufficient. In some cases there will be name clashes within a program
12096 (particularly if the executable itself includes full debugging symbols)
12097 necessitating the use of the fully qualified name when referring to the
12098 contents of the DLL. Use single-quotes around the name to avoid the
12099 exclamation mark (``!'') being interpreted as a language operator.
12101 Note that the internal name of the DLL may be all upper-case, even
12102 though the file name of the DLL is lower-case, or vice-versa. Since
12103 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
12104 some confusion. If in doubt, try the @code{info functions} and
12105 @code{info variables} commands or even @code{maint print msymbols} (see
12106 @pxref{Symbols}). Here's an example:
12109 (@value{GDBP}) info function CreateFileA
12110 All functions matching regular expression "CreateFileA":
12112 Non-debugging symbols:
12113 0x77e885f4 CreateFileA
12114 0x77e885f4 KERNEL32!CreateFileA
12118 (@value{GDBP}) info function !
12119 All functions matching regular expression "!":
12121 Non-debugging symbols:
12122 0x6100114c cygwin1!__assert
12123 0x61004034 cygwin1!_dll_crt0@@0
12124 0x61004240 cygwin1!dll_crt0(per_process *)
12128 @subsubsection Working with minimal symbols
12130 Symbols extracted from a DLL's export table do not contain very much
12131 type information. All that @value{GDBN} can do is guess whether a symbol
12132 refers to a function or variable depending on the linker section that
12133 contains the symbol. Also note that the actual contents of the memory
12134 contained in a DLL are not available unless the program is running. This
12135 means that you cannot examine the contents of a variable or disassemble
12136 a function within a DLL without a running program.
12138 Variables are generally treated as pointers and dereferenced
12139 automatically. For this reason, it is often necessary to prefix a
12140 variable name with the address-of operator (``&'') and provide explicit
12141 type information in the command. Here's an example of the type of
12145 (@value{GDBP}) print 'cygwin1!__argv'
12150 (@value{GDBP}) x 'cygwin1!__argv'
12151 0x10021610: "\230y\""
12154 And two possible solutions:
12157 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
12158 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
12162 (@value{GDBP}) x/2x &'cygwin1!__argv'
12163 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
12164 (@value{GDBP}) x/x 0x10021608
12165 0x10021608: 0x0022fd98
12166 (@value{GDBP}) x/s 0x0022fd98
12167 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
12170 Setting a break point within a DLL is possible even before the program
12171 starts execution. However, under these circumstances, @value{GDBN} can't
12172 examine the initial instructions of the function in order to skip the
12173 function's frame set-up code. You can work around this by using ``*&''
12174 to set the breakpoint at a raw memory address:
12177 (@value{GDBP}) break *&'python22!PyOS_Readline'
12178 Breakpoint 1 at 0x1e04eff0
12181 The author of these extensions is not entirely convinced that setting a
12182 break point within a shared DLL like @file{kernel32.dll} is completely
12186 @section Embedded Operating Systems
12188 This section describes configurations involving the debugging of
12189 embedded operating systems that are available for several different
12193 * VxWorks:: Using @value{GDBN} with VxWorks
12196 @value{GDBN} includes the ability to debug programs running on
12197 various real-time operating systems.
12200 @subsection Using @value{GDBN} with VxWorks
12206 @kindex target vxworks
12207 @item target vxworks @var{machinename}
12208 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
12209 is the target system's machine name or IP address.
12213 On VxWorks, @code{load} links @var{filename} dynamically on the
12214 current target system as well as adding its symbols in @value{GDBN}.
12216 @value{GDBN} enables developers to spawn and debug tasks running on networked
12217 VxWorks targets from a Unix host. Already-running tasks spawned from
12218 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
12219 both the Unix host and on the VxWorks target. The program
12220 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
12221 installed with the name @code{vxgdb}, to distinguish it from a
12222 @value{GDBN} for debugging programs on the host itself.)
12225 @item VxWorks-timeout @var{args}
12226 @kindex vxworks-timeout
12227 All VxWorks-based targets now support the option @code{vxworks-timeout}.
12228 This option is set by the user, and @var{args} represents the number of
12229 seconds @value{GDBN} waits for responses to rpc's. You might use this if
12230 your VxWorks target is a slow software simulator or is on the far side
12231 of a thin network line.
12234 The following information on connecting to VxWorks was current when
12235 this manual was produced; newer releases of VxWorks may use revised
12238 @findex INCLUDE_RDB
12239 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
12240 to include the remote debugging interface routines in the VxWorks
12241 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
12242 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
12243 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
12244 source debugging task @code{tRdbTask} when VxWorks is booted. For more
12245 information on configuring and remaking VxWorks, see the manufacturer's
12247 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
12249 Once you have included @file{rdb.a} in your VxWorks system image and set
12250 your Unix execution search path to find @value{GDBN}, you are ready to
12251 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
12252 @code{vxgdb}, depending on your installation).
12254 @value{GDBN} comes up showing the prompt:
12261 * VxWorks Connection:: Connecting to VxWorks
12262 * VxWorks Download:: VxWorks download
12263 * VxWorks Attach:: Running tasks
12266 @node VxWorks Connection
12267 @subsubsection Connecting to VxWorks
12269 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
12270 network. To connect to a target whose host name is ``@code{tt}'', type:
12273 (vxgdb) target vxworks tt
12277 @value{GDBN} displays messages like these:
12280 Attaching remote machine across net...
12285 @value{GDBN} then attempts to read the symbol tables of any object modules
12286 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
12287 these files by searching the directories listed in the command search
12288 path (@pxref{Environment, ,Your program's environment}); if it fails
12289 to find an object file, it displays a message such as:
12292 prog.o: No such file or directory.
12295 When this happens, add the appropriate directory to the search path with
12296 the @value{GDBN} command @code{path}, and execute the @code{target}
12299 @node VxWorks Download
12300 @subsubsection VxWorks download
12302 @cindex download to VxWorks
12303 If you have connected to the VxWorks target and you want to debug an
12304 object that has not yet been loaded, you can use the @value{GDBN}
12305 @code{load} command to download a file from Unix to VxWorks
12306 incrementally. The object file given as an argument to the @code{load}
12307 command is actually opened twice: first by the VxWorks target in order
12308 to download the code, then by @value{GDBN} in order to read the symbol
12309 table. This can lead to problems if the current working directories on
12310 the two systems differ. If both systems have NFS mounted the same
12311 filesystems, you can avoid these problems by using absolute paths.
12312 Otherwise, it is simplest to set the working directory on both systems
12313 to the directory in which the object file resides, and then to reference
12314 the file by its name, without any path. For instance, a program
12315 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
12316 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
12317 program, type this on VxWorks:
12320 -> cd "@var{vxpath}/vw/demo/rdb"
12324 Then, in @value{GDBN}, type:
12327 (vxgdb) cd @var{hostpath}/vw/demo/rdb
12328 (vxgdb) load prog.o
12331 @value{GDBN} displays a response similar to this:
12334 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
12337 You can also use the @code{load} command to reload an object module
12338 after editing and recompiling the corresponding source file. Note that
12339 this makes @value{GDBN} delete all currently-defined breakpoints,
12340 auto-displays, and convenience variables, and to clear the value
12341 history. (This is necessary in order to preserve the integrity of
12342 debugger's data structures that reference the target system's symbol
12345 @node VxWorks Attach
12346 @subsubsection Running tasks
12348 @cindex running VxWorks tasks
12349 You can also attach to an existing task using the @code{attach} command as
12353 (vxgdb) attach @var{task}
12357 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
12358 or suspended when you attach to it. Running tasks are suspended at
12359 the time of attachment.
12361 @node Embedded Processors
12362 @section Embedded Processors
12364 This section goes into details specific to particular embedded
12370 * H8/300:: Renesas H8/300
12371 * H8/500:: Renesas H8/500
12372 * M32R/D:: Renesas M32R/D
12373 * M68K:: Motorola M68K
12374 * MIPS Embedded:: MIPS Embedded
12375 * OpenRISC 1000:: OpenRisc 1000
12376 * PA:: HP PA Embedded
12379 * Sparclet:: Tsqware Sparclet
12380 * Sparclite:: Fujitsu Sparclite
12381 * ST2000:: Tandem ST2000
12382 * Z8000:: Zilog Z8000
12391 @item target rdi @var{dev}
12392 ARM Angel monitor, via RDI library interface to ADP protocol. You may
12393 use this target to communicate with both boards running the Angel
12394 monitor, or with the EmbeddedICE JTAG debug device.
12397 @item target rdp @var{dev}
12403 @subsection Renesas H8/300
12407 @kindex target hms@r{, with H8/300}
12408 @item target hms @var{dev}
12409 A Renesas SH, H8/300, or H8/500 board, attached via serial line to your host.
12410 Use special commands @code{device} and @code{speed} to control the serial
12411 line and the communications speed used.
12413 @kindex target e7000@r{, with H8/300}
12414 @item target e7000 @var{dev}
12415 E7000 emulator for Renesas H8 and SH.
12417 @kindex target sh3@r{, with H8/300}
12418 @kindex target sh3e@r{, with H8/300}
12419 @item target sh3 @var{dev}
12420 @itemx target sh3e @var{dev}
12421 Renesas SH-3 and SH-3E target systems.
12425 @cindex download to H8/300 or H8/500
12426 @cindex H8/300 or H8/500 download
12427 @cindex download to Renesas SH
12428 @cindex Renesas SH download
12429 When you select remote debugging to a Renesas SH, H8/300, or H8/500
12430 board, the @code{load} command downloads your program to the Renesas
12431 board and also opens it as the current executable target for
12432 @value{GDBN} on your host (like the @code{file} command).
12434 @value{GDBN} needs to know these things to talk to your
12435 Renesas SH, H8/300, or H8/500:
12439 that you want to use @samp{target hms}, the remote debugging interface
12440 for Renesas microprocessors, or @samp{target e7000}, the in-circuit
12441 emulator for the Renesas SH and the Renesas 300H. (@samp{target hms} is
12442 the default when @value{GDBN} is configured specifically for the Renesas SH,
12443 H8/300, or H8/500.)
12446 what serial device connects your host to your Renesas board (the first
12447 serial device available on your host is the default).
12450 what speed to use over the serial device.
12454 * Renesas Boards:: Connecting to Renesas boards.
12455 * Renesas ICE:: Using the E7000 In-Circuit Emulator.
12456 * Renesas Special:: Special @value{GDBN} commands for Renesas micros.
12459 @node Renesas Boards
12460 @subsubsection Connecting to Renesas boards
12462 @c only for Unix hosts
12464 @cindex serial device, Renesas micros
12465 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
12466 need to explicitly set the serial device. The default @var{port} is the
12467 first available port on your host. This is only necessary on Unix
12468 hosts, where it is typically something like @file{/dev/ttya}.
12471 @cindex serial line speed, Renesas micros
12472 @code{@value{GDBN}} has another special command to set the communications
12473 speed: @samp{speed @var{bps}}. This command also is only used from Unix
12474 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
12475 the DOS @code{mode} command (for instance,
12476 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
12478 The @samp{device} and @samp{speed} commands are available only when you
12479 use a Unix host to debug your Renesas microprocessor programs. If you
12481 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
12482 called @code{asynctsr} to communicate with the development board
12483 through a PC serial port. You must also use the DOS @code{mode} command
12484 to set up the serial port on the DOS side.
12486 The following sample session illustrates the steps needed to start a
12487 program under @value{GDBN} control on an H8/300. The example uses a
12488 sample H8/300 program called @file{t.x}. The procedure is the same for
12489 the Renesas SH and the H8/500.
12491 First hook up your development board. In this example, we use a
12492 board attached to serial port @code{COM2}; if you use a different serial
12493 port, substitute its name in the argument of the @code{mode} command.
12494 When you call @code{asynctsr}, the auxiliary comms program used by the
12495 debugger, you give it just the numeric part of the serial port's name;
12496 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
12500 C:\H8300\TEST> asynctsr 2
12501 C:\H8300\TEST> mode com2:9600,n,8,1,p
12503 Resident portion of MODE loaded
12505 COM2: 9600, n, 8, 1, p
12510 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
12511 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
12512 disable it, or even boot without it, to use @code{asynctsr} to control
12513 your development board.
12516 @kindex target hms@r{, and serial protocol}
12517 Now that serial communications are set up, and the development board is
12518 connected, you can start up @value{GDBN}. Call @code{@value{GDBP}} with
12519 the name of your program as the argument. @code{@value{GDBN}} prompts
12520 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
12521 commands to begin your debugging session: @samp{target hms} to specify
12522 cross-debugging to the Renesas board, and the @code{load} command to
12523 download your program to the board. @code{load} displays the names of
12524 the program's sections, and a @samp{*} for each 2K of data downloaded.
12525 (If you want to refresh @value{GDBN} data on symbols or on the
12526 executable file without downloading, use the @value{GDBN} commands
12527 @code{file} or @code{symbol-file}. These commands, and @code{load}
12528 itself, are described in @ref{Files,,Commands to specify files}.)
12531 (eg-C:\H8300\TEST) @value{GDBP} t.x
12532 @value{GDBN} is free software and you are welcome to distribute copies
12533 of it under certain conditions; type "show copying" to see
12535 There is absolutely no warranty for @value{GDBN}; type "show warranty"
12537 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
12538 (@value{GDBP}) target hms
12539 Connected to remote H8/300 HMS system.
12540 (@value{GDBP}) load t.x
12541 .text : 0x8000 .. 0xabde ***********
12542 .data : 0xabde .. 0xad30 *
12543 .stack : 0xf000 .. 0xf014 *
12546 At this point, you're ready to run or debug your program. From here on,
12547 you can use all the usual @value{GDBN} commands. The @code{break} command
12548 sets breakpoints; the @code{run} command starts your program;
12549 @code{print} or @code{x} display data; the @code{continue} command
12550 resumes execution after stopping at a breakpoint. You can use the
12551 @code{help} command at any time to find out more about @value{GDBN} commands.
12553 Remember, however, that @emph{operating system} facilities aren't
12554 available on your development board; for example, if your program hangs,
12555 you can't send an interrupt---but you can press the @sc{reset} switch!
12557 Use the @sc{reset} button on the development board
12560 to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
12561 no way to pass an interrupt signal to the development board); and
12564 to return to the @value{GDBN} command prompt after your program finishes
12565 normally. The communications protocol provides no other way for @value{GDBN}
12566 to detect program completion.
12569 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
12570 development board as a ``normal exit'' of your program.
12573 @subsubsection Using the E7000 in-circuit emulator
12575 @kindex target e7000@r{, with Renesas ICE}
12576 You can use the E7000 in-circuit emulator to develop code for either the
12577 Renesas SH or the H8/300H. Use one of these forms of the @samp{target
12578 e7000} command to connect @value{GDBN} to your E7000:
12581 @item target e7000 @var{port} @var{speed}
12582 Use this form if your E7000 is connected to a serial port. The
12583 @var{port} argument identifies what serial port to use (for example,
12584 @samp{com2}). The third argument is the line speed in bits per second
12585 (for example, @samp{9600}).
12587 @item target e7000 @var{hostname}
12588 If your E7000 is installed as a host on a TCP/IP network, you can just
12589 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
12592 @node Renesas Special
12593 @subsubsection Special @value{GDBN} commands for Renesas micros
12595 Some @value{GDBN} commands are available only for the H8/300:
12599 @kindex set machine
12600 @kindex show machine
12601 @item set machine h8300
12602 @itemx set machine h8300h
12603 Condition @value{GDBN} for one of the two variants of the H8/300
12604 architecture with @samp{set machine}. You can use @samp{show machine}
12605 to check which variant is currently in effect.
12614 @kindex set memory @var{mod}
12615 @cindex memory models, H8/500
12616 @item set memory @var{mod}
12618 Specify which H8/500 memory model (@var{mod}) you are using with
12619 @samp{set memory}; check which memory model is in effect with @samp{show
12620 memory}. The accepted values for @var{mod} are @code{small},
12621 @code{big}, @code{medium}, and @code{compact}.
12626 @subsection Renesas M32R/D
12630 @kindex target m32r
12631 @item target m32r @var{dev}
12632 Renesas M32R/D ROM monitor.
12634 @kindex target m32rsdi
12635 @item target m32rsdi @var{dev}
12636 Renesas M32R SDI server, connected via parallel port to the board.
12643 The Motorola m68k configuration includes ColdFire support, and
12644 target command for the following ROM monitors.
12648 @kindex target abug
12649 @item target abug @var{dev}
12650 ABug ROM monitor for M68K.
12652 @kindex target cpu32bug
12653 @item target cpu32bug @var{dev}
12654 CPU32BUG monitor, running on a CPU32 (M68K) board.
12656 @kindex target dbug
12657 @item target dbug @var{dev}
12658 dBUG ROM monitor for Motorola ColdFire.
12661 @item target est @var{dev}
12662 EST-300 ICE monitor, running on a CPU32 (M68K) board.
12664 @kindex target rom68k
12665 @item target rom68k @var{dev}
12666 ROM 68K monitor, running on an M68K IDP board.
12672 @kindex target rombug
12673 @item target rombug @var{dev}
12674 ROMBUG ROM monitor for OS/9000.
12678 @node MIPS Embedded
12679 @subsection MIPS Embedded
12681 @cindex MIPS boards
12682 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
12683 MIPS board attached to a serial line. This is available when
12684 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
12687 Use these @value{GDBN} commands to specify the connection to your target board:
12690 @item target mips @var{port}
12691 @kindex target mips @var{port}
12692 To run a program on the board, start up @code{@value{GDBP}} with the
12693 name of your program as the argument. To connect to the board, use the
12694 command @samp{target mips @var{port}}, where @var{port} is the name of
12695 the serial port connected to the board. If the program has not already
12696 been downloaded to the board, you may use the @code{load} command to
12697 download it. You can then use all the usual @value{GDBN} commands.
12699 For example, this sequence connects to the target board through a serial
12700 port, and loads and runs a program called @var{prog} through the
12704 host$ @value{GDBP} @var{prog}
12705 @value{GDBN} is free software and @dots{}
12706 (@value{GDBP}) target mips /dev/ttyb
12707 (@value{GDBP}) load @var{prog}
12711 @item target mips @var{hostname}:@var{portnumber}
12712 On some @value{GDBN} host configurations, you can specify a TCP
12713 connection (for instance, to a serial line managed by a terminal
12714 concentrator) instead of a serial port, using the syntax
12715 @samp{@var{hostname}:@var{portnumber}}.
12717 @item target pmon @var{port}
12718 @kindex target pmon @var{port}
12721 @item target ddb @var{port}
12722 @kindex target ddb @var{port}
12723 NEC's DDB variant of PMON for Vr4300.
12725 @item target lsi @var{port}
12726 @kindex target lsi @var{port}
12727 LSI variant of PMON.
12729 @kindex target r3900
12730 @item target r3900 @var{dev}
12731 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
12733 @kindex target array
12734 @item target array @var{dev}
12735 Array Tech LSI33K RAID controller board.
12741 @value{GDBN} also supports these special commands for MIPS targets:
12744 @item set processor @var{args}
12745 @itemx show processor
12746 @kindex set processor @var{args}
12747 @kindex show processor
12748 Use the @code{set processor} command to set the type of MIPS
12749 processor when you want to access processor-type-specific registers.
12750 For example, @code{set processor @var{r3041}} tells @value{GDBN}
12751 to use the CPU registers appropriate for the 3041 chip.
12752 Use the @code{show processor} command to see what MIPS processor @value{GDBN}
12753 is using. Use the @code{info reg} command to see what registers
12754 @value{GDBN} is using.
12756 @item set mipsfpu double
12757 @itemx set mipsfpu single
12758 @itemx set mipsfpu none
12759 @itemx show mipsfpu
12760 @kindex set mipsfpu
12761 @kindex show mipsfpu
12762 @cindex MIPS remote floating point
12763 @cindex floating point, MIPS remote
12764 If your target board does not support the MIPS floating point
12765 coprocessor, you should use the command @samp{set mipsfpu none} (if you
12766 need this, you may wish to put the command in your @value{GDBN} init
12767 file). This tells @value{GDBN} how to find the return value of
12768 functions which return floating point values. It also allows
12769 @value{GDBN} to avoid saving the floating point registers when calling
12770 functions on the board. If you are using a floating point coprocessor
12771 with only single precision floating point support, as on the @sc{r4650}
12772 processor, use the command @samp{set mipsfpu single}. The default
12773 double precision floating point coprocessor may be selected using
12774 @samp{set mipsfpu double}.
12776 In previous versions the only choices were double precision or no
12777 floating point, so @samp{set mipsfpu on} will select double precision
12778 and @samp{set mipsfpu off} will select no floating point.
12780 As usual, you can inquire about the @code{mipsfpu} variable with
12781 @samp{show mipsfpu}.
12783 @item set remotedebug @var{n}
12784 @itemx show remotedebug
12785 @kindex set remotedebug@r{, MIPS protocol}
12786 @kindex show remotedebug@r{, MIPS protocol}
12787 @cindex @code{remotedebug}, MIPS protocol
12788 @cindex MIPS @code{remotedebug} protocol
12789 @c FIXME! For this to be useful, you must know something about the MIPS
12790 @c FIXME...protocol. Where is it described?
12791 You can see some debugging information about communications with the board
12792 by setting the @code{remotedebug} variable. If you set it to @code{1} using
12793 @samp{set remotedebug 1}, every packet is displayed. If you set it
12794 to @code{2}, every character is displayed. You can check the current value
12795 at any time with the command @samp{show remotedebug}.
12797 @item set timeout @var{seconds}
12798 @itemx set retransmit-timeout @var{seconds}
12799 @itemx show timeout
12800 @itemx show retransmit-timeout
12801 @cindex @code{timeout}, MIPS protocol
12802 @cindex @code{retransmit-timeout}, MIPS protocol
12803 @kindex set timeout
12804 @kindex show timeout
12805 @kindex set retransmit-timeout
12806 @kindex show retransmit-timeout
12807 You can control the timeout used while waiting for a packet, in the MIPS
12808 remote protocol, with the @code{set timeout @var{seconds}} command. The
12809 default is 5 seconds. Similarly, you can control the timeout used while
12810 waiting for an acknowledgement of a packet with the @code{set
12811 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
12812 You can inspect both values with @code{show timeout} and @code{show
12813 retransmit-timeout}. (These commands are @emph{only} available when
12814 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
12816 The timeout set by @code{set timeout} does not apply when @value{GDBN}
12817 is waiting for your program to stop. In that case, @value{GDBN} waits
12818 forever because it has no way of knowing how long the program is going
12819 to run before stopping.
12822 @node OpenRISC 1000
12823 @subsection OpenRISC 1000
12824 @cindex OpenRISC 1000
12826 @cindex or1k boards
12827 See OR1k Architecture document (@uref{www.opencores.org}) for more information
12828 about platform and commands.
12832 @kindex target jtag
12833 @item target jtag jtag://@var{host}:@var{port}
12835 Connects to remote JTAG server.
12836 JTAG remote server can be either an or1ksim or JTAG server,
12837 connected via parallel port to the board.
12839 Example: @code{target jtag jtag://localhost:9999}
12842 @item or1ksim @var{command}
12843 If connected to @code{or1ksim} OpenRISC 1000 Architectural
12844 Simulator, proprietary commands can be executed.
12846 @kindex info or1k spr
12847 @item info or1k spr
12848 Displays spr groups.
12850 @item info or1k spr @var{group}
12851 @itemx info or1k spr @var{groupno}
12852 Displays register names in selected group.
12854 @item info or1k spr @var{group} @var{register}
12855 @itemx info or1k spr @var{register}
12856 @itemx info or1k spr @var{groupno} @var{registerno}
12857 @itemx info or1k spr @var{registerno}
12858 Shows information about specified spr register.
12861 @item spr @var{group} @var{register} @var{value}
12862 @itemx spr @var{register @var{value}}
12863 @itemx spr @var{groupno} @var{registerno @var{value}}
12864 @itemx spr @var{registerno @var{value}}
12865 Writes @var{value} to specified spr register.
12868 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
12869 It is very similar to @value{GDBN} trace, except it does not interfere with normal
12870 program execution and is thus much faster. Hardware breakpoints/watchpoint
12871 triggers can be set using:
12874 Load effective address/data
12876 Store effective address/data
12878 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
12883 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
12884 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
12886 @code{htrace} commands:
12887 @cindex OpenRISC 1000 htrace
12890 @item hwatch @var{conditional}
12891 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
12892 or Data. For example:
12894 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
12896 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
12900 Display information about current HW trace configuration.
12902 @item htrace trigger @var{conditional}
12903 Set starting criteria for HW trace.
12905 @item htrace qualifier @var{conditional}
12906 Set acquisition qualifier for HW trace.
12908 @item htrace stop @var{conditional}
12909 Set HW trace stopping criteria.
12911 @item htrace record [@var{data}]*
12912 Selects the data to be recorded, when qualifier is met and HW trace was
12915 @item htrace enable
12916 @itemx htrace disable
12917 Enables/disables the HW trace.
12919 @item htrace rewind [@var{filename}]
12920 Clears currently recorded trace data.
12922 If filename is specified, new trace file is made and any newly collected data
12923 will be written there.
12925 @item htrace print [@var{start} [@var{len}]]
12926 Prints trace buffer, using current record configuration.
12928 @item htrace mode continuous
12929 Set continuous trace mode.
12931 @item htrace mode suspend
12932 Set suspend trace mode.
12937 @subsection PowerPC
12941 @kindex target dink32
12942 @item target dink32 @var{dev}
12943 DINK32 ROM monitor.
12945 @kindex target ppcbug
12946 @item target ppcbug @var{dev}
12947 @kindex target ppcbug1
12948 @item target ppcbug1 @var{dev}
12949 PPCBUG ROM monitor for PowerPC.
12952 @item target sds @var{dev}
12953 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
12958 @subsection HP PA Embedded
12962 @kindex target op50n
12963 @item target op50n @var{dev}
12964 OP50N monitor, running on an OKI HPPA board.
12966 @kindex target w89k
12967 @item target w89k @var{dev}
12968 W89K monitor, running on a Winbond HPPA board.
12973 @subsection Renesas SH
12977 @kindex target hms@r{, with Renesas SH}
12978 @item target hms @var{dev}
12979 A Renesas SH board attached via serial line to your host. Use special
12980 commands @code{device} and @code{speed} to control the serial line and
12981 the communications speed used.
12983 @kindex target e7000@r{, with Renesas SH}
12984 @item target e7000 @var{dev}
12985 E7000 emulator for Renesas SH.
12987 @kindex target sh3@r{, with SH}
12988 @kindex target sh3e@r{, with SH}
12989 @item target sh3 @var{dev}
12990 @item target sh3e @var{dev}
12991 Renesas SH-3 and SH-3E target systems.
12996 @subsection Tsqware Sparclet
13000 @value{GDBN} enables developers to debug tasks running on
13001 Sparclet targets from a Unix host.
13002 @value{GDBN} uses code that runs on
13003 both the Unix host and on the Sparclet target. The program
13004 @code{@value{GDBP}} is installed and executed on the Unix host.
13007 @item remotetimeout @var{args}
13008 @kindex remotetimeout
13009 @value{GDBN} supports the option @code{remotetimeout}.
13010 This option is set by the user, and @var{args} represents the number of
13011 seconds @value{GDBN} waits for responses.
13014 @cindex compiling, on Sparclet
13015 When compiling for debugging, include the options @samp{-g} to get debug
13016 information and @samp{-Ttext} to relocate the program to where you wish to
13017 load it on the target. You may also want to add the options @samp{-n} or
13018 @samp{-N} in order to reduce the size of the sections. Example:
13021 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
13024 You can use @code{objdump} to verify that the addresses are what you intended:
13027 sparclet-aout-objdump --headers --syms prog
13030 @cindex running, on Sparclet
13032 your Unix execution search path to find @value{GDBN}, you are ready to
13033 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
13034 (or @code{sparclet-aout-gdb}, depending on your installation).
13036 @value{GDBN} comes up showing the prompt:
13043 * Sparclet File:: Setting the file to debug
13044 * Sparclet Connection:: Connecting to Sparclet
13045 * Sparclet Download:: Sparclet download
13046 * Sparclet Execution:: Running and debugging
13049 @node Sparclet File
13050 @subsubsection Setting file to debug
13052 The @value{GDBN} command @code{file} lets you choose with program to debug.
13055 (gdbslet) file prog
13059 @value{GDBN} then attempts to read the symbol table of @file{prog}.
13060 @value{GDBN} locates
13061 the file by searching the directories listed in the command search
13063 If the file was compiled with debug information (option "-g"), source
13064 files will be searched as well.
13065 @value{GDBN} locates
13066 the source files by searching the directories listed in the directory search
13067 path (@pxref{Environment, ,Your program's environment}).
13069 to find a file, it displays a message such as:
13072 prog: No such file or directory.
13075 When this happens, add the appropriate directories to the search paths with
13076 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
13077 @code{target} command again.
13079 @node Sparclet Connection
13080 @subsubsection Connecting to Sparclet
13082 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
13083 To connect to a target on serial port ``@code{ttya}'', type:
13086 (gdbslet) target sparclet /dev/ttya
13087 Remote target sparclet connected to /dev/ttya
13088 main () at ../prog.c:3
13092 @value{GDBN} displays messages like these:
13098 @node Sparclet Download
13099 @subsubsection Sparclet download
13101 @cindex download to Sparclet
13102 Once connected to the Sparclet target,
13103 you can use the @value{GDBN}
13104 @code{load} command to download the file from the host to the target.
13105 The file name and load offset should be given as arguments to the @code{load}
13107 Since the file format is aout, the program must be loaded to the starting
13108 address. You can use @code{objdump} to find out what this value is. The load
13109 offset is an offset which is added to the VMA (virtual memory address)
13110 of each of the file's sections.
13111 For instance, if the program
13112 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
13113 and bss at 0x12010170, in @value{GDBN}, type:
13116 (gdbslet) load prog 0x12010000
13117 Loading section .text, size 0xdb0 vma 0x12010000
13120 If the code is loaded at a different address then what the program was linked
13121 to, you may need to use the @code{section} and @code{add-symbol-file} commands
13122 to tell @value{GDBN} where to map the symbol table.
13124 @node Sparclet Execution
13125 @subsubsection Running and debugging
13127 @cindex running and debugging Sparclet programs
13128 You can now begin debugging the task using @value{GDBN}'s execution control
13129 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
13130 manual for the list of commands.
13134 Breakpoint 1 at 0x12010000: file prog.c, line 3.
13136 Starting program: prog
13137 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
13138 3 char *symarg = 0;
13140 4 char *execarg = "hello!";
13145 @subsection Fujitsu Sparclite
13149 @kindex target sparclite
13150 @item target sparclite @var{dev}
13151 Fujitsu sparclite boards, used only for the purpose of loading.
13152 You must use an additional command to debug the program.
13153 For example: target remote @var{dev} using @value{GDBN} standard
13159 @subsection Tandem ST2000
13161 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
13164 To connect your ST2000 to the host system, see the manufacturer's
13165 manual. Once the ST2000 is physically attached, you can run:
13168 target st2000 @var{dev} @var{speed}
13172 to establish it as your debugging environment. @var{dev} is normally
13173 the name of a serial device, such as @file{/dev/ttya}, connected to the
13174 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
13175 connection (for example, to a serial line attached via a terminal
13176 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
13178 The @code{load} and @code{attach} commands are @emph{not} defined for
13179 this target; you must load your program into the ST2000 as you normally
13180 would for standalone operation. @value{GDBN} reads debugging information
13181 (such as symbols) from a separate, debugging version of the program
13182 available on your host computer.
13183 @c FIXME!! This is terribly vague; what little content is here is
13184 @c basically hearsay.
13186 @cindex ST2000 auxiliary commands
13187 These auxiliary @value{GDBN} commands are available to help you with the ST2000
13191 @item st2000 @var{command}
13192 @kindex st2000 @var{cmd}
13193 @cindex STDBUG commands (ST2000)
13194 @cindex commands to STDBUG (ST2000)
13195 Send a @var{command} to the STDBUG monitor. See the manufacturer's
13196 manual for available commands.
13199 @cindex connect (to STDBUG)
13200 Connect the controlling terminal to the STDBUG command monitor. When
13201 you are done interacting with STDBUG, typing either of two character
13202 sequences gets you back to the @value{GDBN} command prompt:
13203 @kbd{@key{RET}~.} (Return, followed by tilde and period) or
13204 @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
13208 @subsection Zilog Z8000
13211 @cindex simulator, Z8000
13212 @cindex Zilog Z8000 simulator
13214 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
13217 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
13218 unsegmented variant of the Z8000 architecture) or the Z8001 (the
13219 segmented variant). The simulator recognizes which architecture is
13220 appropriate by inspecting the object code.
13223 @item target sim @var{args}
13225 @kindex target sim@r{, with Z8000}
13226 Debug programs on a simulated CPU. If the simulator supports setup
13227 options, specify them via @var{args}.
13231 After specifying this target, you can debug programs for the simulated
13232 CPU in the same style as programs for your host computer; use the
13233 @code{file} command to load a new program image, the @code{run} command
13234 to run your program, and so on.
13236 As well as making available all the usual machine registers
13237 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
13238 additional items of information as specially named registers:
13243 Counts clock-ticks in the simulator.
13246 Counts instructions run in the simulator.
13249 Execution time in 60ths of a second.
13253 You can refer to these values in @value{GDBN} expressions with the usual
13254 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
13255 conditional breakpoint that suspends only after at least 5000
13256 simulated clock ticks.
13258 @node Architectures
13259 @section Architectures
13261 This section describes characteristics of architectures that affect
13262 all uses of @value{GDBN} with the architecture, both native and cross.
13275 @kindex set rstack_high_address
13276 @cindex AMD 29K register stack
13277 @cindex register stack, AMD29K
13278 @item set rstack_high_address @var{address}
13279 On AMD 29000 family processors, registers are saved in a separate
13280 @dfn{register stack}. There is no way for @value{GDBN} to determine the
13281 extent of this stack. Normally, @value{GDBN} just assumes that the
13282 stack is ``large enough''. This may result in @value{GDBN} referencing
13283 memory locations that do not exist. If necessary, you can get around
13284 this problem by specifying the ending address of the register stack with
13285 the @code{set rstack_high_address} command. The argument should be an
13286 address, which you probably want to precede with @samp{0x} to specify in
13289 @kindex show rstack_high_address
13290 @item show rstack_high_address
13291 Display the current limit of the register stack, on AMD 29000 family
13299 See the following section.
13304 @cindex stack on Alpha
13305 @cindex stack on MIPS
13306 @cindex Alpha stack
13308 Alpha- and MIPS-based computers use an unusual stack frame, which
13309 sometimes requires @value{GDBN} to search backward in the object code to
13310 find the beginning of a function.
13312 @cindex response time, MIPS debugging
13313 To improve response time (especially for embedded applications, where
13314 @value{GDBN} may be restricted to a slow serial line for this search)
13315 you may want to limit the size of this search, using one of these
13319 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
13320 @item set heuristic-fence-post @var{limit}
13321 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
13322 search for the beginning of a function. A value of @var{0} (the
13323 default) means there is no limit. However, except for @var{0}, the
13324 larger the limit the more bytes @code{heuristic-fence-post} must search
13325 and therefore the longer it takes to run.
13327 @item show heuristic-fence-post
13328 Display the current limit.
13332 These commands are available @emph{only} when @value{GDBN} is configured
13333 for debugging programs on Alpha or MIPS processors.
13336 @node Controlling GDB
13337 @chapter Controlling @value{GDBN}
13339 You can alter the way @value{GDBN} interacts with you by using the
13340 @code{set} command. For commands controlling how @value{GDBN} displays
13341 data, see @ref{Print Settings, ,Print settings}. Other settings are
13346 * Editing:: Command editing
13347 * History:: Command history
13348 * Screen Size:: Screen size
13349 * Numbers:: Numbers
13350 * ABI:: Configuring the current ABI
13351 * Messages/Warnings:: Optional warnings and messages
13352 * Debugging Output:: Optional messages about internal happenings
13360 @value{GDBN} indicates its readiness to read a command by printing a string
13361 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
13362 can change the prompt string with the @code{set prompt} command. For
13363 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
13364 the prompt in one of the @value{GDBN} sessions so that you can always tell
13365 which one you are talking to.
13367 @emph{Note:} @code{set prompt} does not add a space for you after the
13368 prompt you set. This allows you to set a prompt which ends in a space
13369 or a prompt that does not.
13373 @item set prompt @var{newprompt}
13374 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
13376 @kindex show prompt
13378 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
13382 @section Command editing
13384 @cindex command line editing
13386 @value{GDBN} reads its input commands via the @dfn{readline} interface. This
13387 @sc{gnu} library provides consistent behavior for programs which provide a
13388 command line interface to the user. Advantages are @sc{gnu} Emacs-style
13389 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
13390 substitution, and a storage and recall of command history across
13391 debugging sessions.
13393 You may control the behavior of command line editing in @value{GDBN} with the
13394 command @code{set}.
13397 @kindex set editing
13400 @itemx set editing on
13401 Enable command line editing (enabled by default).
13403 @item set editing off
13404 Disable command line editing.
13406 @kindex show editing
13408 Show whether command line editing is enabled.
13412 @section Command history
13414 @value{GDBN} can keep track of the commands you type during your
13415 debugging sessions, so that you can be certain of precisely what
13416 happened. Use these commands to manage the @value{GDBN} command
13420 @cindex history substitution
13421 @cindex history file
13422 @kindex set history filename
13423 @cindex @env{GDBHISTFILE}, environment variable
13424 @item set history filename @var{fname}
13425 Set the name of the @value{GDBN} command history file to @var{fname}.
13426 This is the file where @value{GDBN} reads an initial command history
13427 list, and where it writes the command history from this session when it
13428 exits. You can access this list through history expansion or through
13429 the history command editing characters listed below. This file defaults
13430 to the value of the environment variable @code{GDBHISTFILE}, or to
13431 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
13434 @cindex history save
13435 @kindex set history
13436 @item set history save
13437 @itemx set history save on
13438 Record command history in a file, whose name may be specified with the
13439 @code{set history filename} command. By default, this option is disabled.
13441 @item set history save off
13442 Stop recording command history in a file.
13444 @cindex history size
13445 @item set history size @var{size}
13446 Set the number of commands which @value{GDBN} keeps in its history list.
13447 This defaults to the value of the environment variable
13448 @code{HISTSIZE}, or to 256 if this variable is not set.
13451 @cindex history expansion
13452 History expansion assigns special meaning to the character @kbd{!}.
13453 @ifset have-readline-appendices
13454 @xref{Event Designators}.
13457 Since @kbd{!} is also the logical not operator in C, history expansion
13458 is off by default. If you decide to enable history expansion with the
13459 @code{set history expansion on} command, you may sometimes need to
13460 follow @kbd{!} (when it is used as logical not, in an expression) with
13461 a space or a tab to prevent it from being expanded. The readline
13462 history facilities do not attempt substitution on the strings
13463 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
13465 The commands to control history expansion are:
13468 @item set history expansion on
13469 @itemx set history expansion
13470 @cindex history expansion
13471 Enable history expansion. History expansion is off by default.
13473 @item set history expansion off
13474 Disable history expansion.
13476 The readline code comes with more complete documentation of
13477 editing and history expansion features. Users unfamiliar with @sc{gnu} Emacs
13478 or @code{vi} may wish to read it.
13479 @ifset have-readline-appendices
13480 @xref{Command Line Editing}.
13484 @kindex show history
13486 @itemx show history filename
13487 @itemx show history save
13488 @itemx show history size
13489 @itemx show history expansion
13490 These commands display the state of the @value{GDBN} history parameters.
13491 @code{show history} by itself displays all four states.
13497 @item show commands
13498 Display the last ten commands in the command history.
13500 @item show commands @var{n}
13501 Print ten commands centered on command number @var{n}.
13503 @item show commands +
13504 Print ten commands just after the commands last printed.
13508 @section Screen size
13509 @cindex size of screen
13510 @cindex pauses in output
13512 Certain commands to @value{GDBN} may produce large amounts of
13513 information output to the screen. To help you read all of it,
13514 @value{GDBN} pauses and asks you for input at the end of each page of
13515 output. Type @key{RET} when you want to continue the output, or @kbd{q}
13516 to discard the remaining output. Also, the screen width setting
13517 determines when to wrap lines of output. Depending on what is being
13518 printed, @value{GDBN} tries to break the line at a readable place,
13519 rather than simply letting it overflow onto the following line.
13521 Normally @value{GDBN} knows the size of the screen from the terminal
13522 driver software. For example, on Unix @value{GDBN} uses the termcap data base
13523 together with the value of the @code{TERM} environment variable and the
13524 @code{stty rows} and @code{stty cols} settings. If this is not correct,
13525 you can override it with the @code{set height} and @code{set
13532 @kindex show height
13533 @item set height @var{lpp}
13535 @itemx set width @var{cpl}
13537 These @code{set} commands specify a screen height of @var{lpp} lines and
13538 a screen width of @var{cpl} characters. The associated @code{show}
13539 commands display the current settings.
13541 If you specify a height of zero lines, @value{GDBN} does not pause during
13542 output no matter how long the output is. This is useful if output is to a
13543 file or to an editor buffer.
13545 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
13546 from wrapping its output.
13551 @cindex number representation
13552 @cindex entering numbers
13554 You can always enter numbers in octal, decimal, or hexadecimal in
13555 @value{GDBN} by the usual conventions: octal numbers begin with
13556 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
13557 begin with @samp{0x}. Numbers that begin with none of these are, by
13558 default, entered in base 10; likewise, the default display for
13559 numbers---when no particular format is specified---is base 10. You can
13560 change the default base for both input and output with the @code{set
13564 @kindex set input-radix
13565 @item set input-radix @var{base}
13566 Set the default base for numeric input. Supported choices
13567 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
13568 specified either unambiguously or using the current default radix; for
13578 sets the base to decimal. On the other hand, @samp{set radix 10}
13579 leaves the radix unchanged no matter what it was.
13581 @kindex set output-radix
13582 @item set output-radix @var{base}
13583 Set the default base for numeric display. Supported choices
13584 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
13585 specified either unambiguously or using the current default radix.
13587 @kindex show input-radix
13588 @item show input-radix
13589 Display the current default base for numeric input.
13591 @kindex show output-radix
13592 @item show output-radix
13593 Display the current default base for numeric display.
13597 @section Configuring the current ABI
13599 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
13600 application automatically. However, sometimes you need to override its
13601 conclusions. Use these commands to manage @value{GDBN}'s view of the
13608 One @value{GDBN} configuration can debug binaries for multiple operating
13609 system targets, either via remote debugging or native emulation.
13610 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
13611 but you can override its conclusion using the @code{set osabi} command.
13612 One example where this is useful is in debugging of binaries which use
13613 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
13614 not have the same identifying marks that the standard C library for your
13619 Show the OS ABI currently in use.
13622 With no argument, show the list of registered available OS ABI's.
13624 @item set osabi @var{abi}
13625 Set the current OS ABI to @var{abi}.
13628 @cindex float promotion
13629 @kindex set coerce-float-to-double
13631 Generally, the way that an argument of type @code{float} is passed to a
13632 function depends on whether the function is prototyped. For a prototyped
13633 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
13634 according to the architecture's convention for @code{float}. For unprototyped
13635 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
13636 @code{double} and then passed.
13638 Unfortunately, some forms of debug information do not reliably indicate whether
13639 a function is prototyped. If @value{GDBN} calls a function that is not marked
13640 as prototyped, it consults @kbd{set coerce-float-to-double}.
13643 @item set coerce-float-to-double
13644 @itemx set coerce-float-to-double on
13645 Arguments of type @code{float} will be promoted to @code{double} when passed
13646 to an unprototyped function. This is the default setting.
13648 @item set coerce-float-to-double off
13649 Arguments of type @code{float} will be passed directly to unprototyped
13654 @kindex show cp-abi
13655 @value{GDBN} needs to know the ABI used for your program's C@t{++}
13656 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
13657 used to build your application. @value{GDBN} only fully supports
13658 programs with a single C@t{++} ABI; if your program contains code using
13659 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
13660 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
13661 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
13662 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
13663 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
13664 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
13669 Show the C@t{++} ABI currently in use.
13672 With no argument, show the list of supported C@t{++} ABI's.
13674 @item set cp-abi @var{abi}
13675 @itemx set cp-abi auto
13676 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
13679 @node Messages/Warnings
13680 @section Optional warnings and messages
13682 By default, @value{GDBN} is silent about its inner workings. If you are
13683 running on a slow machine, you may want to use the @code{set verbose}
13684 command. This makes @value{GDBN} tell you when it does a lengthy
13685 internal operation, so you will not think it has crashed.
13687 Currently, the messages controlled by @code{set verbose} are those
13688 which announce that the symbol table for a source file is being read;
13689 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
13692 @kindex set verbose
13693 @item set verbose on
13694 Enables @value{GDBN} output of certain informational messages.
13696 @item set verbose off
13697 Disables @value{GDBN} output of certain informational messages.
13699 @kindex show verbose
13701 Displays whether @code{set verbose} is on or off.
13704 By default, if @value{GDBN} encounters bugs in the symbol table of an
13705 object file, it is silent; but if you are debugging a compiler, you may
13706 find this information useful (@pxref{Symbol Errors, ,Errors reading
13711 @kindex set complaints
13712 @item set complaints @var{limit}
13713 Permits @value{GDBN} to output @var{limit} complaints about each type of
13714 unusual symbols before becoming silent about the problem. Set
13715 @var{limit} to zero to suppress all complaints; set it to a large number
13716 to prevent complaints from being suppressed.
13718 @kindex show complaints
13719 @item show complaints
13720 Displays how many symbol complaints @value{GDBN} is permitted to produce.
13724 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
13725 lot of stupid questions to confirm certain commands. For example, if
13726 you try to run a program which is already running:
13730 The program being debugged has been started already.
13731 Start it from the beginning? (y or n)
13734 If you are willing to unflinchingly face the consequences of your own
13735 commands, you can disable this ``feature'':
13739 @kindex set confirm
13741 @cindex confirmation
13742 @cindex stupid questions
13743 @item set confirm off
13744 Disables confirmation requests.
13746 @item set confirm on
13747 Enables confirmation requests (the default).
13749 @kindex show confirm
13751 Displays state of confirmation requests.
13755 @node Debugging Output
13756 @section Optional messages about internal happenings
13757 @cindex optional debugging messages
13761 @cindex gdbarch debugging info
13762 @item set debug arch
13763 Turns on or off display of gdbarch debugging info. The default is off
13765 @item show debug arch
13766 Displays the current state of displaying gdbarch debugging info.
13767 @item set debug event
13768 @cindex event debugging info
13769 Turns on or off display of @value{GDBN} event debugging info. The
13771 @item show debug event
13772 Displays the current state of displaying @value{GDBN} event debugging
13774 @item set debug expression
13775 @cindex expression debugging info
13776 Turns on or off display of @value{GDBN} expression debugging info. The
13778 @item show debug expression
13779 Displays the current state of displaying @value{GDBN} expression
13781 @item set debug frame
13782 @cindex frame debugging info
13783 Turns on or off display of @value{GDBN} frame debugging info. The
13785 @item show debug frame
13786 Displays the current state of displaying @value{GDBN} frame debugging
13788 @item set debug observer
13789 @cindex observer debugging info
13790 Turns on or off display of @value{GDBN} observer debugging. This
13791 includes info such as the notification of observable events.
13792 @item show debug observer
13793 Displays the current state of observer debugging.
13794 @item set debug overload
13795 @cindex C@t{++} overload debugging info
13796 Turns on or off display of @value{GDBN} C@t{++} overload debugging
13797 info. This includes info such as ranking of functions, etc. The default
13799 @item show debug overload
13800 Displays the current state of displaying @value{GDBN} C@t{++} overload
13802 @cindex packets, reporting on stdout
13803 @cindex serial connections, debugging
13804 @item set debug remote
13805 Turns on or off display of reports on all packets sent back and forth across
13806 the serial line to the remote machine. The info is printed on the
13807 @value{GDBN} standard output stream. The default is off.
13808 @item show debug remote
13809 Displays the state of display of remote packets.
13810 @item set debug serial
13811 Turns on or off display of @value{GDBN} serial debugging info. The
13813 @item show debug serial
13814 Displays the current state of displaying @value{GDBN} serial debugging
13816 @item set debug target
13817 @cindex target debugging info
13818 Turns on or off display of @value{GDBN} target debugging info. This info
13819 includes what is going on at the target level of GDB, as it happens. The
13820 default is 0. Set it to 1 to track events, and to 2 to also track the
13821 value of large memory transfers. Changes to this flag do not take effect
13822 until the next time you connect to a target or use the @code{run} command.
13823 @item show debug target
13824 Displays the current state of displaying @value{GDBN} target debugging
13826 @item set debug varobj
13827 @cindex variable object debugging info
13828 Turns on or off display of @value{GDBN} variable object debugging
13829 info. The default is off.
13830 @item show debug varobj
13831 Displays the current state of displaying @value{GDBN} variable object
13836 @chapter Canned Sequences of Commands
13838 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
13839 command lists}), @value{GDBN} provides two ways to store sequences of
13840 commands for execution as a unit: user-defined commands and command
13844 * Define:: User-defined commands
13845 * Hooks:: User-defined command hooks
13846 * Command Files:: Command files
13847 * Output:: Commands for controlled output
13851 @section User-defined commands
13853 @cindex user-defined command
13854 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
13855 which you assign a new name as a command. This is done with the
13856 @code{define} command. User commands may accept up to 10 arguments
13857 separated by whitespace. Arguments are accessed within the user command
13858 via @var{$arg0@dots{}$arg9}. A trivial example:
13862 print $arg0 + $arg1 + $arg2
13866 To execute the command use:
13873 This defines the command @code{adder}, which prints the sum of
13874 its three arguments. Note the arguments are text substitutions, so they may
13875 reference variables, use complex expressions, or even perform inferior
13881 @item define @var{commandname}
13882 Define a command named @var{commandname}. If there is already a command
13883 by that name, you are asked to confirm that you want to redefine it.
13885 The definition of the command is made up of other @value{GDBN} command lines,
13886 which are given following the @code{define} command. The end of these
13887 commands is marked by a line containing @code{end}.
13892 Takes a single argument, which is an expression to evaluate.
13893 It is followed by a series of commands that are executed
13894 only if the expression is true (nonzero).
13895 There can then optionally be a line @code{else}, followed
13896 by a series of commands that are only executed if the expression
13897 was false. The end of the list is marked by a line containing @code{end}.
13901 The syntax is similar to @code{if}: the command takes a single argument,
13902 which is an expression to evaluate, and must be followed by the commands to
13903 execute, one per line, terminated by an @code{end}.
13904 The commands are executed repeatedly as long as the expression
13908 @item document @var{commandname}
13909 Document the user-defined command @var{commandname}, so that it can be
13910 accessed by @code{help}. The command @var{commandname} must already be
13911 defined. This command reads lines of documentation just as @code{define}
13912 reads the lines of the command definition, ending with @code{end}.
13913 After the @code{document} command is finished, @code{help} on command
13914 @var{commandname} displays the documentation you have written.
13916 You may use the @code{document} command again to change the
13917 documentation of a command. Redefining the command with @code{define}
13918 does not change the documentation.
13920 @kindex help user-defined
13921 @item help user-defined
13922 List all user-defined commands, with the first line of the documentation
13927 @itemx show user @var{commandname}
13928 Display the @value{GDBN} commands used to define @var{commandname} (but
13929 not its documentation). If no @var{commandname} is given, display the
13930 definitions for all user-defined commands.
13932 @kindex show max-user-call-depth
13933 @kindex set max-user-call-depth
13934 @item show max-user-call-depth
13935 @itemx set max-user-call-depth
13936 The value of @code{max-user-call-depth} controls how many recursion
13937 levels are allowed in user-defined commands before GDB suspects an
13938 infinite recursion and aborts the command.
13942 When user-defined commands are executed, the
13943 commands of the definition are not printed. An error in any command
13944 stops execution of the user-defined command.
13946 If used interactively, commands that would ask for confirmation proceed
13947 without asking when used inside a user-defined command. Many @value{GDBN}
13948 commands that normally print messages to say what they are doing omit the
13949 messages when used in a user-defined command.
13952 @section User-defined command hooks
13953 @cindex command hooks
13954 @cindex hooks, for commands
13955 @cindex hooks, pre-command
13958 You may define @dfn{hooks}, which are a special kind of user-defined
13959 command. Whenever you run the command @samp{foo}, if the user-defined
13960 command @samp{hook-foo} exists, it is executed (with no arguments)
13961 before that command.
13963 @cindex hooks, post-command
13965 A hook may also be defined which is run after the command you executed.
13966 Whenever you run the command @samp{foo}, if the user-defined command
13967 @samp{hookpost-foo} exists, it is executed (with no arguments) after
13968 that command. Post-execution hooks may exist simultaneously with
13969 pre-execution hooks, for the same command.
13971 It is valid for a hook to call the command which it hooks. If this
13972 occurs, the hook is not re-executed, thereby avoiding infinte recursion.
13974 @c It would be nice if hookpost could be passed a parameter indicating
13975 @c if the command it hooks executed properly or not. FIXME!
13977 @kindex stop@r{, a pseudo-command}
13978 In addition, a pseudo-command, @samp{stop} exists. Defining
13979 (@samp{hook-stop}) makes the associated commands execute every time
13980 execution stops in your program: before breakpoint commands are run,
13981 displays are printed, or the stack frame is printed.
13983 For example, to ignore @code{SIGALRM} signals while
13984 single-stepping, but treat them normally during normal execution,
13989 handle SIGALRM nopass
13993 handle SIGALRM pass
13996 define hook-continue
13997 handle SIGLARM pass
14001 As a further example, to hook at the begining and end of the @code{echo}
14002 command, and to add extra text to the beginning and end of the message,
14010 define hookpost-echo
14014 (@value{GDBP}) echo Hello World
14015 <<<---Hello World--->>>
14020 You can define a hook for any single-word command in @value{GDBN}, but
14021 not for command aliases; you should define a hook for the basic command
14022 name, e.g. @code{backtrace} rather than @code{bt}.
14023 @c FIXME! So how does Joe User discover whether a command is an alias
14025 If an error occurs during the execution of your hook, execution of
14026 @value{GDBN} commands stops and @value{GDBN} issues a prompt
14027 (before the command that you actually typed had a chance to run).
14029 If you try to define a hook which does not match any known command, you
14030 get a warning from the @code{define} command.
14032 @node Command Files
14033 @section Command files
14035 @cindex command files
14036 A command file for @value{GDBN} is a file of lines that are @value{GDBN}
14037 commands. Comments (lines starting with @kbd{#}) may also be included.
14038 An empty line in a command file does nothing; it does not mean to repeat
14039 the last command, as it would from the terminal.
14042 @cindex @file{.gdbinit}
14043 @cindex @file{gdb.ini}
14044 When you start @value{GDBN}, it automatically executes commands from its
14045 @dfn{init files}, normally called @file{.gdbinit}@footnote{The DJGPP
14046 port of @value{GDBN} uses the name @file{gdb.ini} instead, due to the
14047 limitations of file names imposed by DOS filesystems.}.
14048 During startup, @value{GDBN} does the following:
14052 Reads the init file (if any) in your home directory@footnote{On
14053 DOS/Windows systems, the home directory is the one pointed to by the
14054 @code{HOME} environment variable.}.
14057 Processes command line options and operands.
14060 Reads the init file (if any) in the current working directory.
14063 Reads command files specified by the @samp{-x} option.
14066 The init file in your home directory can set options (such as @samp{set
14067 complaints}) that affect subsequent processing of command line options
14068 and operands. Init files are not executed if you use the @samp{-nx}
14069 option (@pxref{Mode Options, ,Choosing modes}).
14071 @cindex init file name
14072 On some configurations of @value{GDBN}, the init file is known by a
14073 different name (these are typically environments where a specialized
14074 form of @value{GDBN} may need to coexist with other forms, hence a
14075 different name for the specialized version's init file). These are the
14076 environments with special init file names:
14078 @cindex @file{.vxgdbinit}
14081 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
14083 @cindex @file{.os68gdbinit}
14085 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
14087 @cindex @file{.esgdbinit}
14089 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
14092 You can also request the execution of a command file with the
14093 @code{source} command:
14097 @item source @var{filename}
14098 Execute the command file @var{filename}.
14101 The lines in a command file are executed sequentially. They are not
14102 printed as they are executed. An error in any command terminates
14103 execution of the command file and control is returned to the console.
14105 Commands that would ask for confirmation if used interactively proceed
14106 without asking when used in a command file. Many @value{GDBN} commands that
14107 normally print messages to say what they are doing omit the messages
14108 when called from command files.
14110 @value{GDBN} also accepts command input from standard input. In this
14111 mode, normal output goes to standard output and error output goes to
14112 standard error. Errors in a command file supplied on standard input do
14113 not terminate execution of the command file --- execution continues with
14117 gdb < cmds > log 2>&1
14120 (The syntax above will vary depending on the shell used.) This example
14121 will execute commands from the file @file{cmds}. All output and errors
14122 would be directed to @file{log}.
14125 @section Commands for controlled output
14127 During the execution of a command file or a user-defined command, normal
14128 @value{GDBN} output is suppressed; the only output that appears is what is
14129 explicitly printed by the commands in the definition. This section
14130 describes three commands useful for generating exactly the output you
14135 @item echo @var{text}
14136 @c I do not consider backslash-space a standard C escape sequence
14137 @c because it is not in ANSI.
14138 Print @var{text}. Nonprinting characters can be included in
14139 @var{text} using C escape sequences, such as @samp{\n} to print a
14140 newline. @strong{No newline is printed unless you specify one.}
14141 In addition to the standard C escape sequences, a backslash followed
14142 by a space stands for a space. This is useful for displaying a
14143 string with spaces at the beginning or the end, since leading and
14144 trailing spaces are otherwise trimmed from all arguments.
14145 To print @samp{@w{ }and foo =@w{ }}, use the command
14146 @samp{echo \@w{ }and foo = \@w{ }}.
14148 A backslash at the end of @var{text} can be used, as in C, to continue
14149 the command onto subsequent lines. For example,
14152 echo This is some text\n\
14153 which is continued\n\
14154 onto several lines.\n
14157 produces the same output as
14160 echo This is some text\n
14161 echo which is continued\n
14162 echo onto several lines.\n
14166 @item output @var{expression}
14167 Print the value of @var{expression} and nothing but that value: no
14168 newlines, no @samp{$@var{nn} = }. The value is not entered in the
14169 value history either. @xref{Expressions, ,Expressions}, for more information
14172 @item output/@var{fmt} @var{expression}
14173 Print the value of @var{expression} in format @var{fmt}. You can use
14174 the same formats as for @code{print}. @xref{Output Formats,,Output
14175 formats}, for more information.
14178 @item printf @var{string}, @var{expressions}@dots{}
14179 Print the values of the @var{expressions} under the control of
14180 @var{string}. The @var{expressions} are separated by commas and may be
14181 either numbers or pointers. Their values are printed as specified by
14182 @var{string}, exactly as if your program were to execute the C
14184 @c FIXME: the above implies that at least all ANSI C formats are
14185 @c supported, but it isn't true: %E and %G don't work (or so it seems).
14186 @c Either this is a bug, or the manual should document what formats are
14190 printf (@var{string}, @var{expressions}@dots{});
14193 For example, you can print two values in hex like this:
14196 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
14199 The only backslash-escape sequences that you can use in the format
14200 string are the simple ones that consist of backslash followed by a
14205 @chapter Command Interpreters
14206 @cindex command interpreters
14208 @value{GDBN} supports multiple command interpreters, and some command
14209 infrastructure to allow users or user interface writers to switch
14210 between interpreters or run commands in other interpreters.
14212 @value{GDBN} currently supports two command interpreters, the console
14213 interpreter (sometimes called the command-line interpreter or @sc{cli})
14214 and the machine interface interpreter (or @sc{gdb/mi}). This manual
14215 describes both of these interfaces in great detail.
14217 By default, @value{GDBN} will start with the console interpreter.
14218 However, the user may choose to start @value{GDBN} with another
14219 interpreter by specifying the @option{-i} or @option{--interpreter}
14220 startup options. Defined interpreters include:
14224 @cindex console interpreter
14225 The traditional console or command-line interpreter. This is the most often
14226 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
14227 @value{GDBN} will use this interpreter.
14230 @cindex mi interpreter
14231 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
14232 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
14233 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
14237 @cindex mi2 interpreter
14238 The current @sc{gdb/mi} interface.
14241 @cindex mi1 interpreter
14242 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
14246 @cindex invoke another interpreter
14247 The interpreter being used by @value{GDBN} may not be dynamically
14248 switched at runtime. Although possible, this could lead to a very
14249 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
14250 enters the command "interpreter-set console" in a console view,
14251 @value{GDBN} would switch to using the console interpreter, rendering
14252 the IDE inoperable!
14254 @kindex interpreter-exec
14255 Although you may only choose a single interpreter at startup, you may execute
14256 commands in any interpreter from the current interpreter using the appropriate
14257 command. If you are running the console interpreter, simply use the
14258 @code{interpreter-exec} command:
14261 interpreter-exec mi "-data-list-register-names"
14264 @sc{gdb/mi} has a similar command, although it is only available in versions of
14265 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
14268 @chapter @value{GDBN} Text User Interface
14270 @cindex Text User Interface
14273 * TUI Overview:: TUI overview
14274 * TUI Keys:: TUI key bindings
14275 * TUI Single Key Mode:: TUI single key mode
14276 * TUI Commands:: TUI specific commands
14277 * TUI Configuration:: TUI configuration variables
14280 The @value{GDBN} Text User Interface, TUI in short, is a terminal
14281 interface which uses the @code{curses} library to show the source
14282 file, the assembly output, the program registers and @value{GDBN}
14283 commands in separate text windows.
14285 The TUI is enabled by invoking @value{GDBN} using either
14287 @samp{gdbtui} or @samp{gdb -tui}.
14290 @section TUI overview
14292 The TUI has two display modes that can be switched while
14297 A curses (or TUI) mode in which it displays several text
14298 windows on the terminal.
14301 A standard mode which corresponds to the @value{GDBN} configured without
14305 In the TUI mode, @value{GDBN} can display several text window
14310 This window is the @value{GDBN} command window with the @value{GDBN}
14311 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
14312 managed using readline but through the TUI. The @emph{command}
14313 window is always visible.
14316 The source window shows the source file of the program. The current
14317 line as well as active breakpoints are displayed in this window.
14320 The assembly window shows the disassembly output of the program.
14323 This window shows the processor registers. It detects when
14324 a register is changed and when this is the case, registers that have
14325 changed are highlighted.
14329 The source and assembly windows show the current program position
14330 by highlighting the current line and marking them with the @samp{>} marker.
14331 Breakpoints are also indicated with two markers. A first one
14332 indicates the breakpoint type:
14336 Breakpoint which was hit at least once.
14339 Breakpoint which was never hit.
14342 Hardware breakpoint which was hit at least once.
14345 Hardware breakpoint which was never hit.
14349 The second marker indicates whether the breakpoint is enabled or not:
14353 Breakpoint is enabled.
14356 Breakpoint is disabled.
14360 The source, assembly and register windows are attached to the thread
14361 and the frame position. They are updated when the current thread
14362 changes, when the frame changes or when the program counter changes.
14363 These three windows are arranged by the TUI according to several
14364 layouts. The layout defines which of these three windows are visible.
14365 The following layouts are available:
14375 source and assembly
14378 source and registers
14381 assembly and registers
14385 On top of the command window a status line gives various information
14386 concerning the current process begin debugged. The status line is
14387 updated when the information it shows changes. The following fields
14392 Indicates the current gdb target
14393 (@pxref{Targets, ,Specifying a Debugging Target}).
14396 Gives information about the current process or thread number.
14397 When no process is being debugged, this field is set to @code{No process}.
14400 Gives the current function name for the selected frame.
14401 The name is demangled if demangling is turned on (@pxref{Print Settings}).
14402 When there is no symbol corresponding to the current program counter
14403 the string @code{??} is displayed.
14406 Indicates the current line number for the selected frame.
14407 When the current line number is not known the string @code{??} is displayed.
14410 Indicates the current program counter address.
14415 @section TUI Key Bindings
14416 @cindex TUI key bindings
14418 The TUI installs several key bindings in the readline keymaps
14419 (@pxref{Command Line Editing}).
14420 They allow to leave or enter in the TUI mode or they operate
14421 directly on the TUI layout and windows. The TUI also provides
14422 a @emph{SingleKey} keymap which binds several keys directly to
14423 @value{GDBN} commands. The following key bindings
14424 are installed for both TUI mode and the @value{GDBN} standard mode.
14433 Enter or leave the TUI mode. When the TUI mode is left,
14434 the curses window management is left and @value{GDBN} operates using
14435 its standard mode writing on the terminal directly. When the TUI
14436 mode is entered, the control is given back to the curses windows.
14437 The screen is then refreshed.
14441 Use a TUI layout with only one window. The layout will
14442 either be @samp{source} or @samp{assembly}. When the TUI mode
14443 is not active, it will switch to the TUI mode.
14445 Think of this key binding as the Emacs @kbd{C-x 1} binding.
14449 Use a TUI layout with at least two windows. When the current
14450 layout shows already two windows, a next layout with two windows is used.
14451 When a new layout is chosen, one window will always be common to the
14452 previous layout and the new one.
14454 Think of it as the Emacs @kbd{C-x 2} binding.
14458 Change the active window. The TUI associates several key bindings
14459 (like scrolling and arrow keys) to the active window. This command
14460 gives the focus to the next TUI window.
14462 Think of it as the Emacs @kbd{C-x o} binding.
14466 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
14467 (@pxref{TUI Single Key Mode}).
14471 The following key bindings are handled only by the TUI mode:
14476 Scroll the active window one page up.
14480 Scroll the active window one page down.
14484 Scroll the active window one line up.
14488 Scroll the active window one line down.
14492 Scroll the active window one column left.
14496 Scroll the active window one column right.
14500 Refresh the screen.
14504 In the TUI mode, the arrow keys are used by the active window
14505 for scrolling. This means they are available for readline when the
14506 active window is the command window. When the command window
14507 does not have the focus, it is necessary to use other readline
14508 key bindings such as @key{C-p}, @key{C-n}, @key{C-b} and @key{C-f}.
14510 @node TUI Single Key Mode
14511 @section TUI Single Key Mode
14512 @cindex TUI single key mode
14514 The TUI provides a @emph{SingleKey} mode in which it installs a particular
14515 key binding in the readline keymaps to connect single keys to
14519 @kindex c @r{(SingleKey TUI key)}
14523 @kindex d @r{(SingleKey TUI key)}
14527 @kindex f @r{(SingleKey TUI key)}
14531 @kindex n @r{(SingleKey TUI key)}
14535 @kindex q @r{(SingleKey TUI key)}
14537 exit the @emph{SingleKey} mode.
14539 @kindex r @r{(SingleKey TUI key)}
14543 @kindex s @r{(SingleKey TUI key)}
14547 @kindex u @r{(SingleKey TUI key)}
14551 @kindex v @r{(SingleKey TUI key)}
14555 @kindex w @r{(SingleKey TUI key)}
14561 Other keys temporarily switch to the @value{GDBN} command prompt.
14562 The key that was pressed is inserted in the editing buffer so that
14563 it is possible to type most @value{GDBN} commands without interaction
14564 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
14565 @emph{SingleKey} mode is restored. The only way to permanently leave
14566 this mode is by hitting @key{q} or @samp{@key{C-x} @key{s}}.
14570 @section TUI specific commands
14571 @cindex TUI commands
14573 The TUI has specific commands to control the text windows.
14574 These commands are always available, that is they do not depend on
14575 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
14576 is in the standard mode, using these commands will automatically switch
14582 List and give the size of all displayed windows.
14586 Display the next layout.
14589 Display the previous layout.
14592 Display the source window only.
14595 Display the assembly window only.
14598 Display the source and assembly window.
14601 Display the register window together with the source or assembly window.
14603 @item focus next | prev | src | asm | regs | split
14605 Set the focus to the named window.
14606 This command allows to change the active window so that scrolling keys
14607 can be affected to another window.
14611 Refresh the screen. This is similar to using @key{C-L} key.
14613 @item tui reg float
14615 Show the floating point registers in the register window.
14617 @item tui reg general
14618 Show the general registers in the register window.
14621 Show the next register group. The list of register groups as well as
14622 their order is target specific. The predefined register groups are the
14623 following: @code{general}, @code{float}, @code{system}, @code{vector},
14624 @code{all}, @code{save}, @code{restore}.
14626 @item tui reg system
14627 Show the system registers in the register window.
14631 Update the source window and the current execution point.
14633 @item winheight @var{name} +@var{count}
14634 @itemx winheight @var{name} -@var{count}
14636 Change the height of the window @var{name} by @var{count}
14637 lines. Positive counts increase the height, while negative counts
14642 @node TUI Configuration
14643 @section TUI configuration variables
14644 @cindex TUI configuration variables
14646 The TUI has several configuration variables that control the
14647 appearance of windows on the terminal.
14650 @item set tui border-kind @var{kind}
14651 @kindex set tui border-kind
14652 Select the border appearance for the source, assembly and register windows.
14653 The possible values are the following:
14656 Use a space character to draw the border.
14659 Use ascii characters + - and | to draw the border.
14662 Use the Alternate Character Set to draw the border. The border is
14663 drawn using character line graphics if the terminal supports them.
14667 @item set tui active-border-mode @var{mode}
14668 @kindex set tui active-border-mode
14669 Select the attributes to display the border of the active window.
14670 The possible values are @code{normal}, @code{standout}, @code{reverse},
14671 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
14673 @item set tui border-mode @var{mode}
14674 @kindex set tui border-mode
14675 Select the attributes to display the border of other windows.
14676 The @var{mode} can be one of the following:
14679 Use normal attributes to display the border.
14685 Use reverse video mode.
14688 Use half bright mode.
14690 @item half-standout
14691 Use half bright and standout mode.
14694 Use extra bright or bold mode.
14696 @item bold-standout
14697 Use extra bright or bold and standout mode.
14704 @chapter Using @value{GDBN} under @sc{gnu} Emacs
14707 @cindex @sc{gnu} Emacs
14708 A special interface allows you to use @sc{gnu} Emacs to view (and
14709 edit) the source files for the program you are debugging with
14712 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
14713 executable file you want to debug as an argument. This command starts
14714 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
14715 created Emacs buffer.
14716 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
14718 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
14723 All ``terminal'' input and output goes through the Emacs buffer.
14726 This applies both to @value{GDBN} commands and their output, and to the input
14727 and output done by the program you are debugging.
14729 This is useful because it means that you can copy the text of previous
14730 commands and input them again; you can even use parts of the output
14733 All the facilities of Emacs' Shell mode are available for interacting
14734 with your program. In particular, you can send signals the usual
14735 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
14740 @value{GDBN} displays source code through Emacs.
14743 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
14744 source file for that frame and puts an arrow (@samp{=>}) at the
14745 left margin of the current line. Emacs uses a separate buffer for
14746 source display, and splits the screen to show both your @value{GDBN} session
14749 Explicit @value{GDBN} @code{list} or search commands still produce output as
14750 usual, but you probably have no reason to use them from Emacs.
14752 If you specify an absolute file name when prompted for the @kbd{M-x
14753 gdb} argument, then Emacs sets your current working directory to where
14754 your program resides. If you only specify the file name, then Emacs
14755 sets your current working directory to to the directory associated
14756 with the previous buffer. In this case, @value{GDBN} may find your
14757 program by searching your environment's @code{PATH} variable, but on
14758 some operating systems it might not find the source. So, although the
14759 @value{GDBN} input and output session proceeds normally, the auxiliary
14760 buffer does not display the current source and line of execution.
14762 The initial working directory of @value{GDBN} is printed on the top
14763 line of the @value{GDBN} I/O buffer and this serves as a default for
14764 the commands that specify files for @value{GDBN} to operate
14765 on. @xref{Files, ,Commands to specify files}.
14767 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
14768 need to call @value{GDBN} by a different name (for example, if you
14769 keep several configurations around, with different names) you can
14770 customize the Emacs variable @code{gud-gdb-command-name} to run the
14773 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
14774 addition to the standard Shell mode commands:
14778 Describe the features of Emacs' @value{GDBN} Mode.
14781 Execute to another source line, like the @value{GDBN} @code{step} command; also
14782 update the display window to show the current file and location.
14785 Execute to next source line in this function, skipping all function
14786 calls, like the @value{GDBN} @code{next} command. Then update the display window
14787 to show the current file and location.
14790 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
14791 display window accordingly.
14794 Execute until exit from the selected stack frame, like the @value{GDBN}
14795 @code{finish} command.
14798 Continue execution of your program, like the @value{GDBN} @code{continue}
14802 Go up the number of frames indicated by the numeric argument
14803 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
14804 like the @value{GDBN} @code{up} command.
14807 Go down the number of frames indicated by the numeric argument, like the
14808 @value{GDBN} @code{down} command.
14811 In any source file, the Emacs command @kbd{C-x SPC} (@code{gud-break})
14812 tells @value{GDBN} to set a breakpoint on the source line point is on.
14814 If you type @kbd{M-x speedbar}, then Emacs displays a separate frame which
14815 shows a backtrace when the @value{GDBN} I/O buffer is current. Move
14816 point to any frame in the stack and type @key{RET} to make it become the
14817 current frame and display the associated source in the source buffer.
14818 Alternatively, click @kbd{Mouse-2} to make the selected frame become the
14821 If you accidentally delete the source-display buffer, an easy way to get
14822 it back is to type the command @code{f} in the @value{GDBN} buffer, to
14823 request a frame display; when you run under Emacs, this recreates
14824 the source buffer if necessary to show you the context of the current
14827 The source files displayed in Emacs are in ordinary Emacs buffers
14828 which are visiting the source files in the usual way. You can edit
14829 the files with these buffers if you wish; but keep in mind that @value{GDBN}
14830 communicates with Emacs in terms of line numbers. If you add or
14831 delete lines from the text, the line numbers that @value{GDBN} knows cease
14832 to correspond properly with the code.
14834 The description given here is for GNU Emacs version 21.3 and a more
14835 detailed description of its interaction with @value{GDBN} is given in
14836 the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu} Emacs Manual}).
14838 @c The following dropped because Epoch is nonstandard. Reactivate
14839 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
14841 @kindex Emacs Epoch environment
14845 Version 18 of @sc{gnu} Emacs has a built-in window system
14846 called the @code{epoch}
14847 environment. Users of this environment can use a new command,
14848 @code{inspect} which performs identically to @code{print} except that
14849 each value is printed in its own window.
14854 @chapter The @sc{gdb/mi} Interface
14856 @unnumberedsec Function and Purpose
14858 @cindex @sc{gdb/mi}, its purpose
14859 @sc{gdb/mi} is a line based machine oriented text interface to @value{GDBN}. It is
14860 specifically intended to support the development of systems which use
14861 the debugger as just one small component of a larger system.
14863 This chapter is a specification of the @sc{gdb/mi} interface. It is written
14864 in the form of a reference manual.
14866 Note that @sc{gdb/mi} is still under construction, so some of the
14867 features described below are incomplete and subject to change.
14869 @unnumberedsec Notation and Terminology
14871 @cindex notational conventions, for @sc{gdb/mi}
14872 This chapter uses the following notation:
14876 @code{|} separates two alternatives.
14879 @code{[ @var{something} ]} indicates that @var{something} is optional:
14880 it may or may not be given.
14883 @code{( @var{group} )*} means that @var{group} inside the parentheses
14884 may repeat zero or more times.
14887 @code{( @var{group} )+} means that @var{group} inside the parentheses
14888 may repeat one or more times.
14891 @code{"@var{string}"} means a literal @var{string}.
14895 @heading Dependencies
14898 @heading Acknowledgments
14900 In alphabetic order: Andrew Cagney, Fernando Nasser, Stan Shebs and
14904 * GDB/MI Command Syntax::
14905 * GDB/MI Compatibility with CLI::
14906 * GDB/MI Output Records::
14907 * GDB/MI Command Description Format::
14908 * GDB/MI Breakpoint Table Commands::
14909 * GDB/MI Data Manipulation::
14910 * GDB/MI Program Control::
14911 * GDB/MI Miscellaneous Commands::
14913 * GDB/MI Kod Commands::
14914 * GDB/MI Memory Overlay Commands::
14915 * GDB/MI Signal Handling Commands::
14917 * GDB/MI Stack Manipulation::
14918 * GDB/MI Symbol Query::
14919 * GDB/MI Target Manipulation::
14920 * GDB/MI Thread Commands::
14921 * GDB/MI Tracepoint Commands::
14922 * GDB/MI Variable Objects::
14925 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14926 @node GDB/MI Command Syntax
14927 @section @sc{gdb/mi} Command Syntax
14930 * GDB/MI Input Syntax::
14931 * GDB/MI Output Syntax::
14932 * GDB/MI Simple Examples::
14935 @node GDB/MI Input Syntax
14936 @subsection @sc{gdb/mi} Input Syntax
14938 @cindex input syntax for @sc{gdb/mi}
14939 @cindex @sc{gdb/mi}, input syntax
14941 @item @var{command} @expansion{}
14942 @code{@var{cli-command} | @var{mi-command}}
14944 @item @var{cli-command} @expansion{}
14945 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
14946 @var{cli-command} is any existing @value{GDBN} CLI command.
14948 @item @var{mi-command} @expansion{}
14949 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
14950 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
14952 @item @var{token} @expansion{}
14953 "any sequence of digits"
14955 @item @var{option} @expansion{}
14956 @code{"-" @var{parameter} [ " " @var{parameter} ]}
14958 @item @var{parameter} @expansion{}
14959 @code{@var{non-blank-sequence} | @var{c-string}}
14961 @item @var{operation} @expansion{}
14962 @emph{any of the operations described in this chapter}
14964 @item @var{non-blank-sequence} @expansion{}
14965 @emph{anything, provided it doesn't contain special characters such as
14966 "-", @var{nl}, """ and of course " "}
14968 @item @var{c-string} @expansion{}
14969 @code{""" @var{seven-bit-iso-c-string-content} """}
14971 @item @var{nl} @expansion{}
14980 The CLI commands are still handled by the @sc{mi} interpreter; their
14981 output is described below.
14984 The @code{@var{token}}, when present, is passed back when the command
14988 Some @sc{mi} commands accept optional arguments as part of the parameter
14989 list. Each option is identified by a leading @samp{-} (dash) and may be
14990 followed by an optional argument parameter. Options occur first in the
14991 parameter list and can be delimited from normal parameters using
14992 @samp{--} (this is useful when some parameters begin with a dash).
14999 We want easy access to the existing CLI syntax (for debugging).
15002 We want it to be easy to spot a @sc{mi} operation.
15005 @node GDB/MI Output Syntax
15006 @subsection @sc{gdb/mi} Output Syntax
15008 @cindex output syntax of @sc{gdb/mi}
15009 @cindex @sc{gdb/mi}, output syntax
15010 The output from @sc{gdb/mi} consists of zero or more out-of-band records
15011 followed, optionally, by a single result record. This result record
15012 is for the most recent command. The sequence of output records is
15013 terminated by @samp{(@value{GDBP})}.
15015 If an input command was prefixed with a @code{@var{token}} then the
15016 corresponding output for that command will also be prefixed by that same
15020 @item @var{output} @expansion{}
15021 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(@value{GDBP})" @var{nl}}
15023 @item @var{result-record} @expansion{}
15024 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
15026 @item @var{out-of-band-record} @expansion{}
15027 @code{@var{async-record} | @var{stream-record}}
15029 @item @var{async-record} @expansion{}
15030 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
15032 @item @var{exec-async-output} @expansion{}
15033 @code{[ @var{token} ] "*" @var{async-output}}
15035 @item @var{status-async-output} @expansion{}
15036 @code{[ @var{token} ] "+" @var{async-output}}
15038 @item @var{notify-async-output} @expansion{}
15039 @code{[ @var{token} ] "=" @var{async-output}}
15041 @item @var{async-output} @expansion{}
15042 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
15044 @item @var{result-class} @expansion{}
15045 @code{"done" | "running" | "connected" | "error" | "exit"}
15047 @item @var{async-class} @expansion{}
15048 @code{"stopped" | @var{others}} (where @var{others} will be added
15049 depending on the needs---this is still in development).
15051 @item @var{result} @expansion{}
15052 @code{ @var{variable} "=" @var{value}}
15054 @item @var{variable} @expansion{}
15055 @code{ @var{string} }
15057 @item @var{value} @expansion{}
15058 @code{ @var{const} | @var{tuple} | @var{list} }
15060 @item @var{const} @expansion{}
15061 @code{@var{c-string}}
15063 @item @var{tuple} @expansion{}
15064 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
15066 @item @var{list} @expansion{}
15067 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
15068 @var{result} ( "," @var{result} )* "]" }
15070 @item @var{stream-record} @expansion{}
15071 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
15073 @item @var{console-stream-output} @expansion{}
15074 @code{"~" @var{c-string}}
15076 @item @var{target-stream-output} @expansion{}
15077 @code{"@@" @var{c-string}}
15079 @item @var{log-stream-output} @expansion{}
15080 @code{"&" @var{c-string}}
15082 @item @var{nl} @expansion{}
15085 @item @var{token} @expansion{}
15086 @emph{any sequence of digits}.
15094 All output sequences end in a single line containing a period.
15097 The @code{@var{token}} is from the corresponding request. If an execution
15098 command is interrupted by the @samp{-exec-interrupt} command, the
15099 @var{token} associated with the @samp{*stopped} message is the one of the
15100 original execution command, not the one of the interrupt command.
15103 @cindex status output in @sc{gdb/mi}
15104 @var{status-async-output} contains on-going status information about the
15105 progress of a slow operation. It can be discarded. All status output is
15106 prefixed by @samp{+}.
15109 @cindex async output in @sc{gdb/mi}
15110 @var{exec-async-output} contains asynchronous state change on the target
15111 (stopped, started, disappeared). All async output is prefixed by
15115 @cindex notify output in @sc{gdb/mi}
15116 @var{notify-async-output} contains supplementary information that the
15117 client should handle (e.g., a new breakpoint information). All notify
15118 output is prefixed by @samp{=}.
15121 @cindex console output in @sc{gdb/mi}
15122 @var{console-stream-output} is output that should be displayed as is in the
15123 console. It is the textual response to a CLI command. All the console
15124 output is prefixed by @samp{~}.
15127 @cindex target output in @sc{gdb/mi}
15128 @var{target-stream-output} is the output produced by the target program.
15129 All the target output is prefixed by @samp{@@}.
15132 @cindex log output in @sc{gdb/mi}
15133 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
15134 instance messages that should be displayed as part of an error log. All
15135 the log output is prefixed by @samp{&}.
15138 @cindex list output in @sc{gdb/mi}
15139 New @sc{gdb/mi} commands should only output @var{lists} containing
15145 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
15146 details about the various output records.
15148 @node GDB/MI Simple Examples
15149 @subsection Simple Examples of @sc{gdb/mi} Interaction
15150 @cindex @sc{gdb/mi}, simple examples
15152 This subsection presents several simple examples of interaction using
15153 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
15154 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
15155 the output received from @sc{gdb/mi}.
15157 @subsubheading Target Stop
15158 @c Ummm... There is no "-stop" command. This assumes async, no?
15159 Here's an example of stopping the inferior process:
15170 <- *stop,reason="stop",address="0x123",source="a.c:123"
15174 @subsubheading Simple CLI Command
15176 Here's an example of a simple CLI command being passed through
15177 @sc{gdb/mi} and on to the CLI.
15187 @subsubheading Command With Side Effects
15190 -> -symbol-file xyz.exe
15191 <- *breakpoint,nr="3",address="0x123",source="a.c:123"
15195 @subsubheading A Bad Command
15197 Here's what happens if you pass a non-existent command:
15201 <- ^error,msg="Undefined MI command: rubbish"
15205 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15206 @node GDB/MI Compatibility with CLI
15207 @section @sc{gdb/mi} Compatibility with CLI
15209 @cindex compatibility, @sc{gdb/mi} and CLI
15210 @cindex @sc{gdb/mi}, compatibility with CLI
15211 To help users familiar with @value{GDBN}'s existing CLI interface, @sc{gdb/mi}
15212 accepts existing CLI commands. As specified by the syntax, such
15213 commands can be directly entered into the @sc{gdb/mi} interface and @value{GDBN} will
15216 This mechanism is provided as an aid to developers of @sc{gdb/mi}
15217 clients and not as a reliable interface into the CLI. Since the command
15218 is being interpreteted in an environment that assumes @sc{gdb/mi}
15219 behaviour, the exact output of such commands is likely to end up being
15220 an un-supported hybrid of @sc{gdb/mi} and CLI output.
15222 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15223 @node GDB/MI Output Records
15224 @section @sc{gdb/mi} Output Records
15227 * GDB/MI Result Records::
15228 * GDB/MI Stream Records::
15229 * GDB/MI Out-of-band Records::
15232 @node GDB/MI Result Records
15233 @subsection @sc{gdb/mi} Result Records
15235 @cindex result records in @sc{gdb/mi}
15236 @cindex @sc{gdb/mi}, result records
15237 In addition to a number of out-of-band notifications, the response to a
15238 @sc{gdb/mi} command includes one of the following result indications:
15242 @item "^done" [ "," @var{results} ]
15243 The synchronous operation was successful, @code{@var{results}} are the return
15248 @c Is this one correct? Should it be an out-of-band notification?
15249 The asynchronous operation was successfully started. The target is
15252 @item "^error" "," @var{c-string}
15254 The operation failed. The @code{@var{c-string}} contains the corresponding
15258 @node GDB/MI Stream Records
15259 @subsection @sc{gdb/mi} Stream Records
15261 @cindex @sc{gdb/mi}, stream records
15262 @cindex stream records in @sc{gdb/mi}
15263 @value{GDBN} internally maintains a number of output streams: the console, the
15264 target, and the log. The output intended for each of these streams is
15265 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
15267 Each stream record begins with a unique @dfn{prefix character} which
15268 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
15269 Syntax}). In addition to the prefix, each stream record contains a
15270 @code{@var{string-output}}. This is either raw text (with an implicit new
15271 line) or a quoted C string (which does not contain an implicit newline).
15274 @item "~" @var{string-output}
15275 The console output stream contains text that should be displayed in the
15276 CLI console window. It contains the textual responses to CLI commands.
15278 @item "@@" @var{string-output}
15279 The target output stream contains any textual output from the running
15282 @item "&" @var{string-output}
15283 The log stream contains debugging messages being produced by @value{GDBN}'s
15287 @node GDB/MI Out-of-band Records
15288 @subsection @sc{gdb/mi} Out-of-band Records
15290 @cindex out-of-band records in @sc{gdb/mi}
15291 @cindex @sc{gdb/mi}, out-of-band records
15292 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
15293 additional changes that have occurred. Those changes can either be a
15294 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
15295 target activity (e.g., target stopped).
15297 The following is a preliminary list of possible out-of-band records.
15304 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15305 @node GDB/MI Command Description Format
15306 @section @sc{gdb/mi} Command Description Format
15308 The remaining sections describe blocks of commands. Each block of
15309 commands is laid out in a fashion similar to this section.
15311 Note the the line breaks shown in the examples are here only for
15312 readability. They don't appear in the real output.
15313 Also note that the commands with a non-available example (N.A.@:) are
15314 not yet implemented.
15316 @subheading Motivation
15318 The motivation for this collection of commands.
15320 @subheading Introduction
15322 A brief introduction to this collection of commands as a whole.
15324 @subheading Commands
15326 For each command in the block, the following is described:
15328 @subsubheading Synopsis
15331 -command @var{args}@dots{}
15334 @subsubheading @value{GDBN} Command
15336 The corresponding @value{GDBN} CLI command.
15338 @subsubheading Result
15340 @subsubheading Out-of-band
15342 @subsubheading Notes
15344 @subsubheading Example
15347 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15348 @node GDB/MI Breakpoint Table Commands
15349 @section @sc{gdb/mi} Breakpoint table commands
15351 @cindex breakpoint commands for @sc{gdb/mi}
15352 @cindex @sc{gdb/mi}, breakpoint commands
15353 This section documents @sc{gdb/mi} commands for manipulating
15356 @subheading The @code{-break-after} Command
15357 @findex -break-after
15359 @subsubheading Synopsis
15362 -break-after @var{number} @var{count}
15365 The breakpoint number @var{number} is not in effect until it has been
15366 hit @var{count} times. To see how this is reflected in the output of
15367 the @samp{-break-list} command, see the description of the
15368 @samp{-break-list} command below.
15370 @subsubheading @value{GDBN} Command
15372 The corresponding @value{GDBN} command is @samp{ignore}.
15374 @subsubheading Example
15379 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",line="5"@}
15386 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15387 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15388 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15389 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15390 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15391 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15392 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15393 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15394 addr="0x000100d0",func="main",file="hello.c",line="5",times="0",
15400 @subheading The @code{-break-catch} Command
15401 @findex -break-catch
15403 @subheading The @code{-break-commands} Command
15404 @findex -break-commands
15408 @subheading The @code{-break-condition} Command
15409 @findex -break-condition
15411 @subsubheading Synopsis
15414 -break-condition @var{number} @var{expr}
15417 Breakpoint @var{number} will stop the program only if the condition in
15418 @var{expr} is true. The condition becomes part of the
15419 @samp{-break-list} output (see the description of the @samp{-break-list}
15422 @subsubheading @value{GDBN} Command
15424 The corresponding @value{GDBN} command is @samp{condition}.
15426 @subsubheading Example
15430 -break-condition 1 1
15434 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15435 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15436 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15437 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15438 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15439 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15440 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15441 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15442 addr="0x000100d0",func="main",file="hello.c",line="5",cond="1",
15443 times="0",ignore="3"@}]@}
15447 @subheading The @code{-break-delete} Command
15448 @findex -break-delete
15450 @subsubheading Synopsis
15453 -break-delete ( @var{breakpoint} )+
15456 Delete the breakpoint(s) whose number(s) are specified in the argument
15457 list. This is obviously reflected in the breakpoint list.
15459 @subsubheading @value{GDBN} command
15461 The corresponding @value{GDBN} command is @samp{delete}.
15463 @subsubheading Example
15471 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
15472 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15473 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15474 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15475 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15476 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15477 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15482 @subheading The @code{-break-disable} Command
15483 @findex -break-disable
15485 @subsubheading Synopsis
15488 -break-disable ( @var{breakpoint} )+
15491 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
15492 break list is now set to @samp{n} for the named @var{breakpoint}(s).
15494 @subsubheading @value{GDBN} Command
15496 The corresponding @value{GDBN} command is @samp{disable}.
15498 @subsubheading Example
15506 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15507 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15508 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15509 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15510 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15511 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15512 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15513 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
15514 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
15518 @subheading The @code{-break-enable} Command
15519 @findex -break-enable
15521 @subsubheading Synopsis
15524 -break-enable ( @var{breakpoint} )+
15527 Enable (previously disabled) @var{breakpoint}(s).
15529 @subsubheading @value{GDBN} Command
15531 The corresponding @value{GDBN} command is @samp{enable}.
15533 @subsubheading Example
15541 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15542 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15543 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15544 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15545 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15546 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15547 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15548 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
15549 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
15553 @subheading The @code{-break-info} Command
15554 @findex -break-info
15556 @subsubheading Synopsis
15559 -break-info @var{breakpoint}
15563 Get information about a single breakpoint.
15565 @subsubheading @value{GDBN} command
15567 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
15569 @subsubheading Example
15572 @subheading The @code{-break-insert} Command
15573 @findex -break-insert
15575 @subsubheading Synopsis
15578 -break-insert [ -t ] [ -h ] [ -r ]
15579 [ -c @var{condition} ] [ -i @var{ignore-count} ]
15580 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
15584 If specified, @var{line}, can be one of:
15591 @item filename:linenum
15592 @item filename:function
15596 The possible optional parameters of this command are:
15600 Insert a tempoary breakpoint.
15602 Insert a hardware breakpoint.
15603 @item -c @var{condition}
15604 Make the breakpoint conditional on @var{condition}.
15605 @item -i @var{ignore-count}
15606 Initialize the @var{ignore-count}.
15608 Insert a regular breakpoint in all the functions whose names match the
15609 given regular expression. Other flags are not applicable to regular
15613 @subsubheading Result
15615 The result is in the form:
15618 ^done,bkptno="@var{number}",func="@var{funcname}",
15619 file="@var{filename}",line="@var{lineno}"
15623 where @var{number} is the @value{GDBN} number for this breakpoint, @var{funcname}
15624 is the name of the function where the breakpoint was inserted,
15625 @var{filename} is the name of the source file which contains this
15626 function, and @var{lineno} is the source line number within that file.
15628 Note: this format is open to change.
15629 @c An out-of-band breakpoint instead of part of the result?
15631 @subsubheading @value{GDBN} Command
15633 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
15634 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
15636 @subsubheading Example
15641 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
15643 -break-insert -t foo
15644 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",line="11"@}
15647 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15648 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15649 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15650 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15651 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15652 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15653 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15654 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15655 addr="0x0001072c", func="main",file="recursive2.c",line="4",times="0"@},
15656 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
15657 addr="0x00010774",func="foo",file="recursive2.c",line="11",times="0"@}]@}
15659 -break-insert -r foo.*
15660 ~int foo(int, int);
15661 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c",line="11"@}
15665 @subheading The @code{-break-list} Command
15666 @findex -break-list
15668 @subsubheading Synopsis
15674 Displays the list of inserted breakpoints, showing the following fields:
15678 number of the breakpoint
15680 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
15682 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
15685 is the breakpoint enabled or no: @samp{y} or @samp{n}
15687 memory location at which the breakpoint is set
15689 logical location of the breakpoint, expressed by function name, file
15692 number of times the breakpoint has been hit
15695 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
15696 @code{body} field is an empty list.
15698 @subsubheading @value{GDBN} Command
15700 The corresponding @value{GDBN} command is @samp{info break}.
15702 @subsubheading Example
15707 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15708 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15709 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15710 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15711 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15712 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15713 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15714 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15715 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
15716 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
15717 addr="0x00010114",func="foo",file="hello.c",line="13",times="0"@}]@}
15721 Here's an example of the result when there are no breakpoints:
15726 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
15727 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15728 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15729 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15730 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15731 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15732 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15737 @subheading The @code{-break-watch} Command
15738 @findex -break-watch
15740 @subsubheading Synopsis
15743 -break-watch [ -a | -r ]
15746 Create a watchpoint. With the @samp{-a} option it will create an
15747 @dfn{access} watchpoint, i.e. a watchpoint that triggers either on a
15748 read from or on a write to the memory location. With the @samp{-r}
15749 option, the watchpoint created is a @dfn{read} watchpoint, i.e. it will
15750 trigger only when the memory location is accessed for reading. Without
15751 either of the options, the watchpoint created is a regular watchpoint,
15752 i.e. it will trigger when the memory location is accessed for writing.
15753 @xref{Set Watchpoints, , Setting watchpoints}.
15755 Note that @samp{-break-list} will report a single list of watchpoints and
15756 breakpoints inserted.
15758 @subsubheading @value{GDBN} Command
15760 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
15763 @subsubheading Example
15765 Setting a watchpoint on a variable in the @code{main} function:
15770 ^done,wpt=@{number="2",exp="x"@}
15774 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
15775 value=@{old="-268439212",new="55"@},
15776 frame=@{func="main",args=[],file="recursive2.c",line="5"@}
15780 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
15781 the program execution twice: first for the variable changing value, then
15782 for the watchpoint going out of scope.
15787 ^done,wpt=@{number="5",exp="C"@}
15791 ^done,reason="watchpoint-trigger",
15792 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
15793 frame=@{func="callee4",args=[],
15794 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
15798 ^done,reason="watchpoint-scope",wpnum="5",
15799 frame=@{func="callee3",args=[@{name="strarg",
15800 value="0x11940 \"A string argument.\""@}],
15801 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
15805 Listing breakpoints and watchpoints, at different points in the program
15806 execution. Note that once the watchpoint goes out of scope, it is
15812 ^done,wpt=@{number="2",exp="C"@}
15815 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15816 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15817 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15818 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15819 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15820 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15821 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15822 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15823 addr="0x00010734",func="callee4",
15824 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
15825 bkpt=@{number="2",type="watchpoint",disp="keep",
15826 enabled="y",addr="",what="C",times="0"@}]@}
15830 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
15831 value=@{old="-276895068",new="3"@},
15832 frame=@{func="callee4",args=[],
15833 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
15836 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15837 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15838 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15839 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15840 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15841 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15842 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15843 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15844 addr="0x00010734",func="callee4",
15845 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
15846 bkpt=@{number="2",type="watchpoint",disp="keep",
15847 enabled="y",addr="",what="C",times="-5"@}]@}
15851 ^done,reason="watchpoint-scope",wpnum="2",
15852 frame=@{func="callee3",args=[@{name="strarg",
15853 value="0x11940 \"A string argument.\""@}],
15854 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
15857 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15858 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15859 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15860 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15861 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15862 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15863 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15864 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15865 addr="0x00010734",func="callee4",
15866 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@}]@}
15870 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15871 @node GDB/MI Data Manipulation
15872 @section @sc{gdb/mi} Data Manipulation
15874 @cindex data manipulation, in @sc{gdb/mi}
15875 @cindex @sc{gdb/mi}, data manipulation
15876 This section describes the @sc{gdb/mi} commands that manipulate data:
15877 examine memory and registers, evaluate expressions, etc.
15879 @c REMOVED FROM THE INTERFACE.
15880 @c @subheading -data-assign
15881 @c Change the value of a program variable. Plenty of side effects.
15882 @c @subsubheading GDB command
15884 @c @subsubheading Example
15887 @subheading The @code{-data-disassemble} Command
15888 @findex -data-disassemble
15890 @subsubheading Synopsis
15894 [ -s @var{start-addr} -e @var{end-addr} ]
15895 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
15903 @item @var{start-addr}
15904 is the beginning address (or @code{$pc})
15905 @item @var{end-addr}
15907 @item @var{filename}
15908 is the name of the file to disassemble
15909 @item @var{linenum}
15910 is the line number to disassemble around
15912 is the the number of disassembly lines to be produced. If it is -1,
15913 the whole function will be disassembled, in case no @var{end-addr} is
15914 specified. If @var{end-addr} is specified as a non-zero value, and
15915 @var{lines} is lower than the number of disassembly lines between
15916 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
15917 displayed; if @var{lines} is higher than the number of lines between
15918 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
15921 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
15925 @subsubheading Result
15927 The output for each instruction is composed of four fields:
15936 Note that whatever included in the instruction field, is not manipulated
15937 directely by @sc{gdb/mi}, i.e. it is not possible to adjust its format.
15939 @subsubheading @value{GDBN} Command
15941 There's no direct mapping from this command to the CLI.
15943 @subsubheading Example
15945 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
15949 -data-disassemble -s $pc -e "$pc + 20" -- 0
15952 @{address="0x000107c0",func-name="main",offset="4",
15953 inst="mov 2, %o0"@},
15954 @{address="0x000107c4",func-name="main",offset="8",
15955 inst="sethi %hi(0x11800), %o2"@},
15956 @{address="0x000107c8",func-name="main",offset="12",
15957 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
15958 @{address="0x000107cc",func-name="main",offset="16",
15959 inst="sethi %hi(0x11800), %o2"@},
15960 @{address="0x000107d0",func-name="main",offset="20",
15961 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
15965 Disassemble the whole @code{main} function. Line 32 is part of
15969 -data-disassemble -f basics.c -l 32 -- 0
15971 @{address="0x000107bc",func-name="main",offset="0",
15972 inst="save %sp, -112, %sp"@},
15973 @{address="0x000107c0",func-name="main",offset="4",
15974 inst="mov 2, %o0"@},
15975 @{address="0x000107c4",func-name="main",offset="8",
15976 inst="sethi %hi(0x11800), %o2"@},
15978 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
15979 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
15983 Disassemble 3 instructions from the start of @code{main}:
15987 -data-disassemble -f basics.c -l 32 -n 3 -- 0
15989 @{address="0x000107bc",func-name="main",offset="0",
15990 inst="save %sp, -112, %sp"@},
15991 @{address="0x000107c0",func-name="main",offset="4",
15992 inst="mov 2, %o0"@},
15993 @{address="0x000107c4",func-name="main",offset="8",
15994 inst="sethi %hi(0x11800), %o2"@}]
15998 Disassemble 3 instructions from the start of @code{main} in mixed mode:
16002 -data-disassemble -f basics.c -l 32 -n 3 -- 1
16004 src_and_asm_line=@{line="31",
16005 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
16006 testsuite/gdb.mi/basics.c",line_asm_insn=[
16007 @{address="0x000107bc",func-name="main",offset="0",
16008 inst="save %sp, -112, %sp"@}]@},
16009 src_and_asm_line=@{line="32",
16010 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
16011 testsuite/gdb.mi/basics.c",line_asm_insn=[
16012 @{address="0x000107c0",func-name="main",offset="4",
16013 inst="mov 2, %o0"@},
16014 @{address="0x000107c4",func-name="main",offset="8",
16015 inst="sethi %hi(0x11800), %o2"@}]@}]
16020 @subheading The @code{-data-evaluate-expression} Command
16021 @findex -data-evaluate-expression
16023 @subsubheading Synopsis
16026 -data-evaluate-expression @var{expr}
16029 Evaluate @var{expr} as an expression. The expression could contain an
16030 inferior function call. The function call will execute synchronously.
16031 If the expression contains spaces, it must be enclosed in double quotes.
16033 @subsubheading @value{GDBN} Command
16035 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
16036 @samp{call}. In @code{gdbtk} only, there's a corresponding
16037 @samp{gdb_eval} command.
16039 @subsubheading Example
16041 In the following example, the numbers that precede the commands are the
16042 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
16043 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
16047 211-data-evaluate-expression A
16050 311-data-evaluate-expression &A
16051 311^done,value="0xefffeb7c"
16053 411-data-evaluate-expression A+3
16056 511-data-evaluate-expression "A + 3"
16062 @subheading The @code{-data-list-changed-registers} Command
16063 @findex -data-list-changed-registers
16065 @subsubheading Synopsis
16068 -data-list-changed-registers
16071 Display a list of the registers that have changed.
16073 @subsubheading @value{GDBN} Command
16075 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
16076 has the corresponding command @samp{gdb_changed_register_list}.
16078 @subsubheading Example
16080 On a PPC MBX board:
16088 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
16089 args=[],file="try.c",line="5"@}
16091 -data-list-changed-registers
16092 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
16093 "10","11","13","14","15","16","17","18","19","20","21","22","23",
16094 "24","25","26","27","28","30","31","64","65","66","67","69"]
16099 @subheading The @code{-data-list-register-names} Command
16100 @findex -data-list-register-names
16102 @subsubheading Synopsis
16105 -data-list-register-names [ ( @var{regno} )+ ]
16108 Show a list of register names for the current target. If no arguments
16109 are given, it shows a list of the names of all the registers. If
16110 integer numbers are given as arguments, it will print a list of the
16111 names of the registers corresponding to the arguments. To ensure
16112 consistency between a register name and its number, the output list may
16113 include empty register names.
16115 @subsubheading @value{GDBN} Command
16117 @value{GDBN} does not have a command which corresponds to
16118 @samp{-data-list-register-names}. In @code{gdbtk} there is a
16119 corresponding command @samp{gdb_regnames}.
16121 @subsubheading Example
16123 For the PPC MBX board:
16126 -data-list-register-names
16127 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
16128 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
16129 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
16130 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
16131 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
16132 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
16133 "", "pc","ps","cr","lr","ctr","xer"]
16135 -data-list-register-names 1 2 3
16136 ^done,register-names=["r1","r2","r3"]
16140 @subheading The @code{-data-list-register-values} Command
16141 @findex -data-list-register-values
16143 @subsubheading Synopsis
16146 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
16149 Display the registers' contents. @var{fmt} is the format according to
16150 which the registers' contents are to be returned, followed by an optional
16151 list of numbers specifying the registers to display. A missing list of
16152 numbers indicates that the contents of all the registers must be returned.
16154 Allowed formats for @var{fmt} are:
16171 @subsubheading @value{GDBN} Command
16173 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
16174 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
16176 @subsubheading Example
16178 For a PPC MBX board (note: line breaks are for readability only, they
16179 don't appear in the actual output):
16183 -data-list-register-values r 64 65
16184 ^done,register-values=[@{number="64",value="0xfe00a300"@},
16185 @{number="65",value="0x00029002"@}]
16187 -data-list-register-values x
16188 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
16189 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
16190 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
16191 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
16192 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
16193 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
16194 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
16195 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
16196 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
16197 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
16198 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
16199 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
16200 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
16201 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
16202 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
16203 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
16204 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
16205 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
16206 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
16207 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
16208 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
16209 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
16210 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
16211 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
16212 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
16213 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
16214 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
16215 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
16216 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
16217 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
16218 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
16219 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
16220 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
16221 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
16222 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
16223 @{number="69",value="0x20002b03"@}]
16228 @subheading The @code{-data-read-memory} Command
16229 @findex -data-read-memory
16231 @subsubheading Synopsis
16234 -data-read-memory [ -o @var{byte-offset} ]
16235 @var{address} @var{word-format} @var{word-size}
16236 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
16243 @item @var{address}
16244 An expression specifying the address of the first memory word to be
16245 read. Complex expressions containing embedded white space should be
16246 quoted using the C convention.
16248 @item @var{word-format}
16249 The format to be used to print the memory words. The notation is the
16250 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
16253 @item @var{word-size}
16254 The size of each memory word in bytes.
16256 @item @var{nr-rows}
16257 The number of rows in the output table.
16259 @item @var{nr-cols}
16260 The number of columns in the output table.
16263 If present, indicates that each row should include an @sc{ascii} dump. The
16264 value of @var{aschar} is used as a padding character when a byte is not a
16265 member of the printable @sc{ascii} character set (printable @sc{ascii}
16266 characters are those whose code is between 32 and 126, inclusively).
16268 @item @var{byte-offset}
16269 An offset to add to the @var{address} before fetching memory.
16272 This command displays memory contents as a table of @var{nr-rows} by
16273 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
16274 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
16275 (returned as @samp{total-bytes}). Should less than the requested number
16276 of bytes be returned by the target, the missing words are identified
16277 using @samp{N/A}. The number of bytes read from the target is returned
16278 in @samp{nr-bytes} and the starting address used to read memory in
16281 The address of the next/previous row or page is available in
16282 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
16285 @subsubheading @value{GDBN} Command
16287 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
16288 @samp{gdb_get_mem} memory read command.
16290 @subsubheading Example
16292 Read six bytes of memory starting at @code{bytes+6} but then offset by
16293 @code{-6} bytes. Format as three rows of two columns. One byte per
16294 word. Display each word in hex.
16298 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
16299 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
16300 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
16301 prev-page="0x0000138a",memory=[
16302 @{addr="0x00001390",data=["0x00","0x01"]@},
16303 @{addr="0x00001392",data=["0x02","0x03"]@},
16304 @{addr="0x00001394",data=["0x04","0x05"]@}]
16308 Read two bytes of memory starting at address @code{shorts + 64} and
16309 display as a single word formatted in decimal.
16313 5-data-read-memory shorts+64 d 2 1 1
16314 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
16315 next-row="0x00001512",prev-row="0x0000150e",
16316 next-page="0x00001512",prev-page="0x0000150e",memory=[
16317 @{addr="0x00001510",data=["128"]@}]
16321 Read thirty two bytes of memory starting at @code{bytes+16} and format
16322 as eight rows of four columns. Include a string encoding with @samp{x}
16323 used as the non-printable character.
16327 4-data-read-memory bytes+16 x 1 8 4 x
16328 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
16329 next-row="0x000013c0",prev-row="0x0000139c",
16330 next-page="0x000013c0",prev-page="0x00001380",memory=[
16331 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
16332 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
16333 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
16334 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
16335 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
16336 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
16337 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
16338 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
16342 @subheading The @code{-display-delete} Command
16343 @findex -display-delete
16345 @subsubheading Synopsis
16348 -display-delete @var{number}
16351 Delete the display @var{number}.
16353 @subsubheading @value{GDBN} Command
16355 The corresponding @value{GDBN} command is @samp{delete display}.
16357 @subsubheading Example
16361 @subheading The @code{-display-disable} Command
16362 @findex -display-disable
16364 @subsubheading Synopsis
16367 -display-disable @var{number}
16370 Disable display @var{number}.
16372 @subsubheading @value{GDBN} Command
16374 The corresponding @value{GDBN} command is @samp{disable display}.
16376 @subsubheading Example
16380 @subheading The @code{-display-enable} Command
16381 @findex -display-enable
16383 @subsubheading Synopsis
16386 -display-enable @var{number}
16389 Enable display @var{number}.
16391 @subsubheading @value{GDBN} Command
16393 The corresponding @value{GDBN} command is @samp{enable display}.
16395 @subsubheading Example
16399 @subheading The @code{-display-insert} Command
16400 @findex -display-insert
16402 @subsubheading Synopsis
16405 -display-insert @var{expression}
16408 Display @var{expression} every time the program stops.
16410 @subsubheading @value{GDBN} Command
16412 The corresponding @value{GDBN} command is @samp{display}.
16414 @subsubheading Example
16418 @subheading The @code{-display-list} Command
16419 @findex -display-list
16421 @subsubheading Synopsis
16427 List the displays. Do not show the current values.
16429 @subsubheading @value{GDBN} Command
16431 The corresponding @value{GDBN} command is @samp{info display}.
16433 @subsubheading Example
16437 @subheading The @code{-environment-cd} Command
16438 @findex -environment-cd
16440 @subsubheading Synopsis
16443 -environment-cd @var{pathdir}
16446 Set @value{GDBN}'s working directory.
16448 @subsubheading @value{GDBN} Command
16450 The corresponding @value{GDBN} command is @samp{cd}.
16452 @subsubheading Example
16456 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
16462 @subheading The @code{-environment-directory} Command
16463 @findex -environment-directory
16465 @subsubheading Synopsis
16468 -environment-directory [ -r ] [ @var{pathdir} ]+
16471 Add directories @var{pathdir} to beginning of search path for source files.
16472 If the @samp{-r} option is used, the search path is reset to the default
16473 search path. If directories @var{pathdir} are supplied in addition to the
16474 @samp{-r} option, the search path is first reset and then addition
16476 Multiple directories may be specified, separated by blanks. Specifying
16477 multiple directories in a single command
16478 results in the directories added to the beginning of the
16479 search path in the same order they were presented in the command.
16480 If blanks are needed as
16481 part of a directory name, double-quotes should be used around
16482 the name. In the command output, the path will show up separated
16483 by the system directory-separator character. The directory-seperator
16484 character must not be used
16485 in any directory name.
16486 If no directories are specified, the current search path is displayed.
16488 @subsubheading @value{GDBN} Command
16490 The corresponding @value{GDBN} command is @samp{dir}.
16492 @subsubheading Example
16496 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
16497 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
16499 -environment-directory ""
16500 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
16502 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
16503 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
16505 -environment-directory -r
16506 ^done,source-path="$cdir:$cwd"
16511 @subheading The @code{-environment-path} Command
16512 @findex -environment-path
16514 @subsubheading Synopsis
16517 -environment-path [ -r ] [ @var{pathdir} ]+
16520 Add directories @var{pathdir} to beginning of search path for object files.
16521 If the @samp{-r} option is used, the search path is reset to the original
16522 search path that existed at gdb start-up. If directories @var{pathdir} are
16523 supplied in addition to the
16524 @samp{-r} option, the search path is first reset and then addition
16526 Multiple directories may be specified, separated by blanks. Specifying
16527 multiple directories in a single command
16528 results in the directories added to the beginning of the
16529 search path in the same order they were presented in the command.
16530 If blanks are needed as
16531 part of a directory name, double-quotes should be used around
16532 the name. In the command output, the path will show up separated
16533 by the system directory-separator character. The directory-seperator
16534 character must not be used
16535 in any directory name.
16536 If no directories are specified, the current path is displayed.
16539 @subsubheading @value{GDBN} Command
16541 The corresponding @value{GDBN} command is @samp{path}.
16543 @subsubheading Example
16548 ^done,path="/usr/bin"
16550 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
16551 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
16553 -environment-path -r /usr/local/bin
16554 ^done,path="/usr/local/bin:/usr/bin"
16559 @subheading The @code{-environment-pwd} Command
16560 @findex -environment-pwd
16562 @subsubheading Synopsis
16568 Show the current working directory.
16570 @subsubheading @value{GDBN} command
16572 The corresponding @value{GDBN} command is @samp{pwd}.
16574 @subsubheading Example
16579 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
16583 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16584 @node GDB/MI Program Control
16585 @section @sc{gdb/mi} Program control
16587 @subsubheading Program termination
16589 As a result of execution, the inferior program can run to completion, if
16590 it doesn't encounter any breakpoints. In this case the output will
16591 include an exit code, if the program has exited exceptionally.
16593 @subsubheading Examples
16596 Program exited normally:
16604 *stopped,reason="exited-normally"
16609 Program exited exceptionally:
16617 *stopped,reason="exited",exit-code="01"
16621 Another way the program can terminate is if it receives a signal such as
16622 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
16626 *stopped,reason="exited-signalled",signal-name="SIGINT",
16627 signal-meaning="Interrupt"
16631 @subheading The @code{-exec-abort} Command
16632 @findex -exec-abort
16634 @subsubheading Synopsis
16640 Kill the inferior running program.
16642 @subsubheading @value{GDBN} Command
16644 The corresponding @value{GDBN} command is @samp{kill}.
16646 @subsubheading Example
16650 @subheading The @code{-exec-arguments} Command
16651 @findex -exec-arguments
16653 @subsubheading Synopsis
16656 -exec-arguments @var{args}
16659 Set the inferior program arguments, to be used in the next
16662 @subsubheading @value{GDBN} Command
16664 The corresponding @value{GDBN} command is @samp{set args}.
16666 @subsubheading Example
16669 Don't have one around.
16672 @subheading The @code{-exec-continue} Command
16673 @findex -exec-continue
16675 @subsubheading Synopsis
16681 Asynchronous command. Resumes the execution of the inferior program
16682 until a breakpoint is encountered, or until the inferior exits.
16684 @subsubheading @value{GDBN} Command
16686 The corresponding @value{GDBN} corresponding is @samp{continue}.
16688 @subsubheading Example
16695 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
16696 file="hello.c",line="13"@}
16701 @subheading The @code{-exec-finish} Command
16702 @findex -exec-finish
16704 @subsubheading Synopsis
16710 Asynchronous command. Resumes the execution of the inferior program
16711 until the current function is exited. Displays the results returned by
16714 @subsubheading @value{GDBN} Command
16716 The corresponding @value{GDBN} command is @samp{finish}.
16718 @subsubheading Example
16720 Function returning @code{void}.
16727 *stopped,reason="function-finished",frame=@{func="main",args=[],
16728 file="hello.c",line="7"@}
16732 Function returning other than @code{void}. The name of the internal
16733 @value{GDBN} variable storing the result is printed, together with the
16740 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
16741 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
16742 file="recursive2.c",line="14"@},
16743 gdb-result-var="$1",return-value="0"
16748 @subheading The @code{-exec-interrupt} Command
16749 @findex -exec-interrupt
16751 @subsubheading Synopsis
16757 Asynchronous command. Interrupts the background execution of the target.
16758 Note how the token associated with the stop message is the one for the
16759 execution command that has been interrupted. The token for the interrupt
16760 itself only appears in the @samp{^done} output. If the user is trying to
16761 interrupt a non-running program, an error message will be printed.
16763 @subsubheading @value{GDBN} Command
16765 The corresponding @value{GDBN} command is @samp{interrupt}.
16767 @subsubheading Example
16778 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
16779 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",line="13"@}
16784 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
16789 @subheading The @code{-exec-next} Command
16792 @subsubheading Synopsis
16798 Asynchronous command. Resumes execution of the inferior program, stopping
16799 when the beginning of the next source line is reached.
16801 @subsubheading @value{GDBN} Command
16803 The corresponding @value{GDBN} command is @samp{next}.
16805 @subsubheading Example
16811 *stopped,reason="end-stepping-range",line="8",file="hello.c"
16816 @subheading The @code{-exec-next-instruction} Command
16817 @findex -exec-next-instruction
16819 @subsubheading Synopsis
16822 -exec-next-instruction
16825 Asynchronous command. Executes one machine instruction. If the
16826 instruction is a function call continues until the function returns. If
16827 the program stops at an instruction in the middle of a source line, the
16828 address will be printed as well.
16830 @subsubheading @value{GDBN} Command
16832 The corresponding @value{GDBN} command is @samp{nexti}.
16834 @subsubheading Example
16838 -exec-next-instruction
16842 *stopped,reason="end-stepping-range",
16843 addr="0x000100d4",line="5",file="hello.c"
16848 @subheading The @code{-exec-return} Command
16849 @findex -exec-return
16851 @subsubheading Synopsis
16857 Makes current function return immediately. Doesn't execute the inferior.
16858 Displays the new current frame.
16860 @subsubheading @value{GDBN} Command
16862 The corresponding @value{GDBN} command is @samp{return}.
16864 @subsubheading Example
16868 200-break-insert callee4
16869 200^done,bkpt=@{number="1",addr="0x00010734",
16870 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
16875 000*stopped,reason="breakpoint-hit",bkptno="1",
16876 frame=@{func="callee4",args=[],
16877 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
16883 111^done,frame=@{level="0",func="callee3",
16884 args=[@{name="strarg",
16885 value="0x11940 \"A string argument.\""@}],
16886 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
16891 @subheading The @code{-exec-run} Command
16894 @subsubheading Synopsis
16900 Asynchronous command. Starts execution of the inferior from the
16901 beginning. The inferior executes until either a breakpoint is
16902 encountered or the program exits.
16904 @subsubheading @value{GDBN} Command
16906 The corresponding @value{GDBN} command is @samp{run}.
16908 @subsubheading Example
16913 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
16918 *stopped,reason="breakpoint-hit",bkptno="1",
16919 frame=@{func="main",args=[],file="recursive2.c",line="4"@}
16924 @subheading The @code{-exec-show-arguments} Command
16925 @findex -exec-show-arguments
16927 @subsubheading Synopsis
16930 -exec-show-arguments
16933 Print the arguments of the program.
16935 @subsubheading @value{GDBN} Command
16937 The corresponding @value{GDBN} command is @samp{show args}.
16939 @subsubheading Example
16942 @c @subheading -exec-signal
16944 @subheading The @code{-exec-step} Command
16947 @subsubheading Synopsis
16953 Asynchronous command. Resumes execution of the inferior program, stopping
16954 when the beginning of the next source line is reached, if the next
16955 source line is not a function call. If it is, stop at the first
16956 instruction of the called function.
16958 @subsubheading @value{GDBN} Command
16960 The corresponding @value{GDBN} command is @samp{step}.
16962 @subsubheading Example
16964 Stepping into a function:
16970 *stopped,reason="end-stepping-range",
16971 frame=@{func="foo",args=[@{name="a",value="10"@},
16972 @{name="b",value="0"@}],file="recursive2.c",line="11"@}
16982 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
16987 @subheading The @code{-exec-step-instruction} Command
16988 @findex -exec-step-instruction
16990 @subsubheading Synopsis
16993 -exec-step-instruction
16996 Asynchronous command. Resumes the inferior which executes one machine
16997 instruction. The output, once @value{GDBN} has stopped, will vary depending on
16998 whether we have stopped in the middle of a source line or not. In the
16999 former case, the address at which the program stopped will be printed as
17002 @subsubheading @value{GDBN} Command
17004 The corresponding @value{GDBN} command is @samp{stepi}.
17006 @subsubheading Example
17010 -exec-step-instruction
17014 *stopped,reason="end-stepping-range",
17015 frame=@{func="foo",args=[],file="try.c",line="10"@}
17017 -exec-step-instruction
17021 *stopped,reason="end-stepping-range",
17022 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",line="10"@}
17027 @subheading The @code{-exec-until} Command
17028 @findex -exec-until
17030 @subsubheading Synopsis
17033 -exec-until [ @var{location} ]
17036 Asynchronous command. Executes the inferior until the @var{location}
17037 specified in the argument is reached. If there is no argument, the inferior
17038 executes until a source line greater than the current one is reached.
17039 The reason for stopping in this case will be @samp{location-reached}.
17041 @subsubheading @value{GDBN} Command
17043 The corresponding @value{GDBN} command is @samp{until}.
17045 @subsubheading Example
17049 -exec-until recursive2.c:6
17053 *stopped,reason="location-reached",frame=@{func="main",args=[],
17054 file="recursive2.c",line="6"@}
17059 @subheading -file-clear
17060 Is this going away????
17064 @subheading The @code{-file-exec-and-symbols} Command
17065 @findex -file-exec-and-symbols
17067 @subsubheading Synopsis
17070 -file-exec-and-symbols @var{file}
17073 Specify the executable file to be debugged. This file is the one from
17074 which the symbol table is also read. If no file is specified, the
17075 command clears the executable and symbol information. If breakpoints
17076 are set when using this command with no arguments, @value{GDBN} will produce
17077 error messages. Otherwise, no output is produced, except a completion
17080 @subsubheading @value{GDBN} Command
17082 The corresponding @value{GDBN} command is @samp{file}.
17084 @subsubheading Example
17088 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
17094 @subheading The @code{-file-exec-file} Command
17095 @findex -file-exec-file
17097 @subsubheading Synopsis
17100 -file-exec-file @var{file}
17103 Specify the executable file to be debugged. Unlike
17104 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
17105 from this file. If used without argument, @value{GDBN} clears the information
17106 about the executable file. No output is produced, except a completion
17109 @subsubheading @value{GDBN} Command
17111 The corresponding @value{GDBN} command is @samp{exec-file}.
17113 @subsubheading Example
17117 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
17123 @subheading The @code{-file-list-exec-sections} Command
17124 @findex -file-list-exec-sections
17126 @subsubheading Synopsis
17129 -file-list-exec-sections
17132 List the sections of the current executable file.
17134 @subsubheading @value{GDBN} Command
17136 The @value{GDBN} command @samp{info file} shows, among the rest, the same
17137 information as this command. @code{gdbtk} has a corresponding command
17138 @samp{gdb_load_info}.
17140 @subsubheading Example
17144 @subheading The @code{-file-list-exec-source-file} Command
17145 @findex -file-list-exec-source-file
17147 @subsubheading Synopsis
17150 -file-list-exec-source-file
17153 List the line number, the current source file, and the absolute path
17154 to the current source file for the current executable.
17156 @subsubheading @value{GDBN} Command
17158 There's no @value{GDBN} command which directly corresponds to this one.
17160 @subsubheading Example
17164 123-file-list-exec-source-file
17165 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
17170 @subheading The @code{-file-list-exec-source-files} Command
17171 @findex -file-list-exec-source-files
17173 @subsubheading Synopsis
17176 -file-list-exec-source-files
17179 List the source files for the current executable.
17181 It will always output the filename, but only when GDB can find the absolute
17182 file name of a source file, will it output the fullname.
17184 @subsubheading @value{GDBN} Command
17186 There's no @value{GDBN} command which directly corresponds to this one.
17187 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
17189 @subsubheading Example
17192 -file-list-exec-source-files
17194 @{file=foo.c,fullname=/home/foo.c@},
17195 @{file=/home/bar.c,fullname=/home/bar.c@},
17196 @{file=gdb_could_not_find_fullpath.c@}]
17200 @subheading The @code{-file-list-shared-libraries} Command
17201 @findex -file-list-shared-libraries
17203 @subsubheading Synopsis
17206 -file-list-shared-libraries
17209 List the shared libraries in the program.
17211 @subsubheading @value{GDBN} Command
17213 The corresponding @value{GDBN} command is @samp{info shared}.
17215 @subsubheading Example
17219 @subheading The @code{-file-list-symbol-files} Command
17220 @findex -file-list-symbol-files
17222 @subsubheading Synopsis
17225 -file-list-symbol-files
17230 @subsubheading @value{GDBN} Command
17232 The corresponding @value{GDBN} command is @samp{info file} (part of it).
17234 @subsubheading Example
17238 @subheading The @code{-file-symbol-file} Command
17239 @findex -file-symbol-file
17241 @subsubheading Synopsis
17244 -file-symbol-file @var{file}
17247 Read symbol table info from the specified @var{file} argument. When
17248 used without arguments, clears @value{GDBN}'s symbol table info. No output is
17249 produced, except for a completion notification.
17251 @subsubheading @value{GDBN} Command
17253 The corresponding @value{GDBN} command is @samp{symbol-file}.
17255 @subsubheading Example
17259 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
17264 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17265 @node GDB/MI Miscellaneous Commands
17266 @section Miscellaneous @value{GDBN} commands in @sc{gdb/mi}
17268 @c @subheading -gdb-complete
17270 @subheading The @code{-gdb-exit} Command
17273 @subsubheading Synopsis
17279 Exit @value{GDBN} immediately.
17281 @subsubheading @value{GDBN} Command
17283 Approximately corresponds to @samp{quit}.
17285 @subsubheading Example
17292 @subheading The @code{-gdb-set} Command
17295 @subsubheading Synopsis
17301 Set an internal @value{GDBN} variable.
17302 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
17304 @subsubheading @value{GDBN} Command
17306 The corresponding @value{GDBN} command is @samp{set}.
17308 @subsubheading Example
17318 @subheading The @code{-gdb-show} Command
17321 @subsubheading Synopsis
17327 Show the current value of a @value{GDBN} variable.
17329 @subsubheading @value{GDBN} command
17331 The corresponding @value{GDBN} command is @samp{show}.
17333 @subsubheading Example
17342 @c @subheading -gdb-source
17345 @subheading The @code{-gdb-version} Command
17346 @findex -gdb-version
17348 @subsubheading Synopsis
17354 Show version information for @value{GDBN}. Used mostly in testing.
17356 @subsubheading @value{GDBN} Command
17358 There's no equivalent @value{GDBN} command. @value{GDBN} by default shows this
17359 information when you start an interactive session.
17361 @subsubheading Example
17363 @c This example modifies the actual output from GDB to avoid overfull
17369 ~Copyright 2000 Free Software Foundation, Inc.
17370 ~GDB is free software, covered by the GNU General Public License, and
17371 ~you are welcome to change it and/or distribute copies of it under
17372 ~ certain conditions.
17373 ~Type "show copying" to see the conditions.
17374 ~There is absolutely no warranty for GDB. Type "show warranty" for
17376 ~This GDB was configured as
17377 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
17382 @subheading The @code{-interpreter-exec} Command
17383 @findex -interpreter-exec
17385 @subheading Synopsis
17388 -interpreter-exec @var{interpreter} @var{command}
17391 Execute the specified @var{command} in the given @var{interpreter}.
17393 @subheading @value{GDBN} Command
17395 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
17397 @subheading Example
17401 -interpreter-exec console "break main"
17402 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
17403 &"During symbol reading, bad structure-type format.\n"
17404 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
17410 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17411 @node GDB/MI Kod Commands
17412 @section @sc{gdb/mi} Kod Commands
17414 The Kod commands are not implemented.
17416 @c @subheading -kod-info
17418 @c @subheading -kod-list
17420 @c @subheading -kod-list-object-types
17422 @c @subheading -kod-show
17424 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17425 @node GDB/MI Memory Overlay Commands
17426 @section @sc{gdb/mi} Memory Overlay Commands
17428 The memory overlay commands are not implemented.
17430 @c @subheading -overlay-auto
17432 @c @subheading -overlay-list-mapping-state
17434 @c @subheading -overlay-list-overlays
17436 @c @subheading -overlay-map
17438 @c @subheading -overlay-off
17440 @c @subheading -overlay-on
17442 @c @subheading -overlay-unmap
17444 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17445 @node GDB/MI Signal Handling Commands
17446 @section @sc{gdb/mi} Signal Handling Commands
17448 Signal handling commands are not implemented.
17450 @c @subheading -signal-handle
17452 @c @subheading -signal-list-handle-actions
17454 @c @subheading -signal-list-signal-types
17458 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17459 @node GDB/MI Stack Manipulation
17460 @section @sc{gdb/mi} Stack Manipulation Commands
17463 @subheading The @code{-stack-info-frame} Command
17464 @findex -stack-info-frame
17466 @subsubheading Synopsis
17472 Get info on the current frame.
17474 @subsubheading @value{GDBN} Command
17476 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
17477 (without arguments).
17479 @subsubheading Example
17482 @subheading The @code{-stack-info-depth} Command
17483 @findex -stack-info-depth
17485 @subsubheading Synopsis
17488 -stack-info-depth [ @var{max-depth} ]
17491 Return the depth of the stack. If the integer argument @var{max-depth}
17492 is specified, do not count beyond @var{max-depth} frames.
17494 @subsubheading @value{GDBN} Command
17496 There's no equivalent @value{GDBN} command.
17498 @subsubheading Example
17500 For a stack with frame levels 0 through 11:
17507 -stack-info-depth 4
17510 -stack-info-depth 12
17513 -stack-info-depth 11
17516 -stack-info-depth 13
17521 @subheading The @code{-stack-list-arguments} Command
17522 @findex -stack-list-arguments
17524 @subsubheading Synopsis
17527 -stack-list-arguments @var{show-values}
17528 [ @var{low-frame} @var{high-frame} ]
17531 Display a list of the arguments for the frames between @var{low-frame}
17532 and @var{high-frame} (inclusive). If @var{low-frame} and
17533 @var{high-frame} are not provided, list the arguments for the whole call
17536 The @var{show-values} argument must have a value of 0 or 1. A value of
17537 0 means that only the names of the arguments are listed, a value of 1
17538 means that both names and values of the arguments are printed.
17540 @subsubheading @value{GDBN} Command
17542 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
17543 @samp{gdb_get_args} command which partially overlaps with the
17544 functionality of @samp{-stack-list-arguments}.
17546 @subsubheading Example
17553 frame=@{level="0",addr="0x00010734",func="callee4",
17554 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
17555 frame=@{level="1",addr="0x0001076c",func="callee3",
17556 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
17557 frame=@{level="2",addr="0x0001078c",func="callee2",
17558 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
17559 frame=@{level="3",addr="0x000107b4",func="callee1",
17560 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
17561 frame=@{level="4",addr="0x000107e0",func="main",
17562 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
17564 -stack-list-arguments 0
17567 frame=@{level="0",args=[]@},
17568 frame=@{level="1",args=[name="strarg"]@},
17569 frame=@{level="2",args=[name="intarg",name="strarg"]@},
17570 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
17571 frame=@{level="4",args=[]@}]
17573 -stack-list-arguments 1
17576 frame=@{level="0",args=[]@},
17578 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
17579 frame=@{level="2",args=[
17580 @{name="intarg",value="2"@},
17581 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
17582 @{frame=@{level="3",args=[
17583 @{name="intarg",value="2"@},
17584 @{name="strarg",value="0x11940 \"A string argument.\""@},
17585 @{name="fltarg",value="3.5"@}]@},
17586 frame=@{level="4",args=[]@}]
17588 -stack-list-arguments 0 2 2
17589 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
17591 -stack-list-arguments 1 2 2
17592 ^done,stack-args=[frame=@{level="2",
17593 args=[@{name="intarg",value="2"@},
17594 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
17598 @c @subheading -stack-list-exception-handlers
17601 @subheading The @code{-stack-list-frames} Command
17602 @findex -stack-list-frames
17604 @subsubheading Synopsis
17607 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
17610 List the frames currently on the stack. For each frame it displays the
17615 The frame number, 0 being the topmost frame, i.e. the innermost function.
17617 The @code{$pc} value for that frame.
17621 File name of the source file where the function lives.
17623 Line number corresponding to the @code{$pc}.
17626 If invoked without arguments, this command prints a backtrace for the
17627 whole stack. If given two integer arguments, it shows the frames whose
17628 levels are between the two arguments (inclusive). If the two arguments
17629 are equal, it shows the single frame at the corresponding level.
17631 @subsubheading @value{GDBN} Command
17633 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
17635 @subsubheading Example
17637 Full stack backtrace:
17643 [frame=@{level="0",addr="0x0001076c",func="foo",
17644 file="recursive2.c",line="11"@},
17645 frame=@{level="1",addr="0x000107a4",func="foo",
17646 file="recursive2.c",line="14"@},
17647 frame=@{level="2",addr="0x000107a4",func="foo",
17648 file="recursive2.c",line="14"@},
17649 frame=@{level="3",addr="0x000107a4",func="foo",
17650 file="recursive2.c",line="14"@},
17651 frame=@{level="4",addr="0x000107a4",func="foo",
17652 file="recursive2.c",line="14"@},
17653 frame=@{level="5",addr="0x000107a4",func="foo",
17654 file="recursive2.c",line="14"@},
17655 frame=@{level="6",addr="0x000107a4",func="foo",
17656 file="recursive2.c",line="14"@},
17657 frame=@{level="7",addr="0x000107a4",func="foo",
17658 file="recursive2.c",line="14"@},
17659 frame=@{level="8",addr="0x000107a4",func="foo",
17660 file="recursive2.c",line="14"@},
17661 frame=@{level="9",addr="0x000107a4",func="foo",
17662 file="recursive2.c",line="14"@},
17663 frame=@{level="10",addr="0x000107a4",func="foo",
17664 file="recursive2.c",line="14"@},
17665 frame=@{level="11",addr="0x00010738",func="main",
17666 file="recursive2.c",line="4"@}]
17670 Show frames between @var{low_frame} and @var{high_frame}:
17674 -stack-list-frames 3 5
17676 [frame=@{level="3",addr="0x000107a4",func="foo",
17677 file="recursive2.c",line="14"@},
17678 frame=@{level="4",addr="0x000107a4",func="foo",
17679 file="recursive2.c",line="14"@},
17680 frame=@{level="5",addr="0x000107a4",func="foo",
17681 file="recursive2.c",line="14"@}]
17685 Show a single frame:
17689 -stack-list-frames 3 3
17691 [frame=@{level="3",addr="0x000107a4",func="foo",
17692 file="recursive2.c",line="14"@}]
17697 @subheading The @code{-stack-list-locals} Command
17698 @findex -stack-list-locals
17700 @subsubheading Synopsis
17703 -stack-list-locals @var{print-values}
17706 Display the local variable names for the current frame. With an
17707 argument of 0 or @code{--no-values}, prints only the names of the variables.
17708 With argument of 1 or @code{--all-values}, prints also their values. With
17709 argument of 2 or @code{--simple-values}, prints the name, type and value for
17710 simple data types and the name and type for arrays, structures and
17711 unions. In this last case, the idea is that the user can see the
17712 value of simple data types immediately and he can create variable
17713 objects for other data types if he wishes to explore their values in
17716 @subsubheading @value{GDBN} Command
17718 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
17720 @subsubheading Example
17724 -stack-list-locals 0
17725 ^done,locals=[name="A",name="B",name="C"]
17727 -stack-list-locals --all-values
17728 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
17729 @{name="C",value="@{1, 2, 3@}"@}]
17730 -stack-list-locals --simple-values
17731 ^done,locals=[@{name="A",type="int",value="1"@},
17732 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
17737 @subheading The @code{-stack-select-frame} Command
17738 @findex -stack-select-frame
17740 @subsubheading Synopsis
17743 -stack-select-frame @var{framenum}
17746 Change the current frame. Select a different frame @var{framenum} on
17749 @subsubheading @value{GDBN} Command
17751 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
17752 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
17754 @subsubheading Example
17758 -stack-select-frame 2
17763 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17764 @node GDB/MI Symbol Query
17765 @section @sc{gdb/mi} Symbol Query Commands
17768 @subheading The @code{-symbol-info-address} Command
17769 @findex -symbol-info-address
17771 @subsubheading Synopsis
17774 -symbol-info-address @var{symbol}
17777 Describe where @var{symbol} is stored.
17779 @subsubheading @value{GDBN} Command
17781 The corresponding @value{GDBN} command is @samp{info address}.
17783 @subsubheading Example
17787 @subheading The @code{-symbol-info-file} Command
17788 @findex -symbol-info-file
17790 @subsubheading Synopsis
17796 Show the file for the symbol.
17798 @subsubheading @value{GDBN} Command
17800 There's no equivalent @value{GDBN} command. @code{gdbtk} has
17801 @samp{gdb_find_file}.
17803 @subsubheading Example
17807 @subheading The @code{-symbol-info-function} Command
17808 @findex -symbol-info-function
17810 @subsubheading Synopsis
17813 -symbol-info-function
17816 Show which function the symbol lives in.
17818 @subsubheading @value{GDBN} Command
17820 @samp{gdb_get_function} in @code{gdbtk}.
17822 @subsubheading Example
17826 @subheading The @code{-symbol-info-line} Command
17827 @findex -symbol-info-line
17829 @subsubheading Synopsis
17835 Show the core addresses of the code for a source line.
17837 @subsubheading @value{GDBN} Command
17839 The corresponding @value{GDBN} command is @samp{info line}.
17840 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
17842 @subsubheading Example
17846 @subheading The @code{-symbol-info-symbol} Command
17847 @findex -symbol-info-symbol
17849 @subsubheading Synopsis
17852 -symbol-info-symbol @var{addr}
17855 Describe what symbol is at location @var{addr}.
17857 @subsubheading @value{GDBN} Command
17859 The corresponding @value{GDBN} command is @samp{info symbol}.
17861 @subsubheading Example
17865 @subheading The @code{-symbol-list-functions} Command
17866 @findex -symbol-list-functions
17868 @subsubheading Synopsis
17871 -symbol-list-functions
17874 List the functions in the executable.
17876 @subsubheading @value{GDBN} Command
17878 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
17879 @samp{gdb_search} in @code{gdbtk}.
17881 @subsubheading Example
17885 @subheading The @code{-symbol-list-lines} Command
17886 @findex -symbol-list-lines
17888 @subsubheading Synopsis
17891 -symbol-list-lines @var{filename}
17894 Print the list of lines that contain code and their associated program
17895 addresses for the given source filename. The entries are sorted in
17896 ascending PC order.
17898 @subsubheading @value{GDBN} Command
17900 There is no corresponding @value{GDBN} command.
17902 @subsubheading Example
17905 -symbol-list-lines basics.c
17906 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
17911 @subheading The @code{-symbol-list-types} Command
17912 @findex -symbol-list-types
17914 @subsubheading Synopsis
17920 List all the type names.
17922 @subsubheading @value{GDBN} Command
17924 The corresponding commands are @samp{info types} in @value{GDBN},
17925 @samp{gdb_search} in @code{gdbtk}.
17927 @subsubheading Example
17931 @subheading The @code{-symbol-list-variables} Command
17932 @findex -symbol-list-variables
17934 @subsubheading Synopsis
17937 -symbol-list-variables
17940 List all the global and static variable names.
17942 @subsubheading @value{GDBN} Command
17944 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
17946 @subsubheading Example
17950 @subheading The @code{-symbol-locate} Command
17951 @findex -symbol-locate
17953 @subsubheading Synopsis
17959 @subsubheading @value{GDBN} Command
17961 @samp{gdb_loc} in @code{gdbtk}.
17963 @subsubheading Example
17967 @subheading The @code{-symbol-type} Command
17968 @findex -symbol-type
17970 @subsubheading Synopsis
17973 -symbol-type @var{variable}
17976 Show type of @var{variable}.
17978 @subsubheading @value{GDBN} Command
17980 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
17981 @samp{gdb_obj_variable}.
17983 @subsubheading Example
17987 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17988 @node GDB/MI Target Manipulation
17989 @section @sc{gdb/mi} Target Manipulation Commands
17992 @subheading The @code{-target-attach} Command
17993 @findex -target-attach
17995 @subsubheading Synopsis
17998 -target-attach @var{pid} | @var{file}
18001 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
18003 @subsubheading @value{GDBN} command
18005 The corresponding @value{GDBN} command is @samp{attach}.
18007 @subsubheading Example
18011 @subheading The @code{-target-compare-sections} Command
18012 @findex -target-compare-sections
18014 @subsubheading Synopsis
18017 -target-compare-sections [ @var{section} ]
18020 Compare data of section @var{section} on target to the exec file.
18021 Without the argument, all sections are compared.
18023 @subsubheading @value{GDBN} Command
18025 The @value{GDBN} equivalent is @samp{compare-sections}.
18027 @subsubheading Example
18031 @subheading The @code{-target-detach} Command
18032 @findex -target-detach
18034 @subsubheading Synopsis
18040 Disconnect from the remote target. There's no output.
18042 @subsubheading @value{GDBN} command
18044 The corresponding @value{GDBN} command is @samp{detach}.
18046 @subsubheading Example
18056 @subheading The @code{-target-disconnect} Command
18057 @findex -target-disconnect
18059 @subsubheading Synopsis
18065 Disconnect from the remote target. There's no output.
18067 @subsubheading @value{GDBN} command
18069 The corresponding @value{GDBN} command is @samp{disconnect}.
18071 @subsubheading Example
18081 @subheading The @code{-target-download} Command
18082 @findex -target-download
18084 @subsubheading Synopsis
18090 Loads the executable onto the remote target.
18091 It prints out an update message every half second, which includes the fields:
18095 The name of the section.
18097 The size of what has been sent so far for that section.
18099 The size of the section.
18101 The total size of what was sent so far (the current and the previous sections).
18103 The size of the overall executable to download.
18107 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
18108 @sc{gdb/mi} Output Syntax}).
18110 In addition, it prints the name and size of the sections, as they are
18111 downloaded. These messages include the following fields:
18115 The name of the section.
18117 The size of the section.
18119 The size of the overall executable to download.
18123 At the end, a summary is printed.
18125 @subsubheading @value{GDBN} Command
18127 The corresponding @value{GDBN} command is @samp{load}.
18129 @subsubheading Example
18131 Note: each status message appears on a single line. Here the messages
18132 have been broken down so that they can fit onto a page.
18137 +download,@{section=".text",section-size="6668",total-size="9880"@}
18138 +download,@{section=".text",section-sent="512",section-size="6668",
18139 total-sent="512",total-size="9880"@}
18140 +download,@{section=".text",section-sent="1024",section-size="6668",
18141 total-sent="1024",total-size="9880"@}
18142 +download,@{section=".text",section-sent="1536",section-size="6668",
18143 total-sent="1536",total-size="9880"@}
18144 +download,@{section=".text",section-sent="2048",section-size="6668",
18145 total-sent="2048",total-size="9880"@}
18146 +download,@{section=".text",section-sent="2560",section-size="6668",
18147 total-sent="2560",total-size="9880"@}
18148 +download,@{section=".text",section-sent="3072",section-size="6668",
18149 total-sent="3072",total-size="9880"@}
18150 +download,@{section=".text",section-sent="3584",section-size="6668",
18151 total-sent="3584",total-size="9880"@}
18152 +download,@{section=".text",section-sent="4096",section-size="6668",
18153 total-sent="4096",total-size="9880"@}
18154 +download,@{section=".text",section-sent="4608",section-size="6668",
18155 total-sent="4608",total-size="9880"@}
18156 +download,@{section=".text",section-sent="5120",section-size="6668",
18157 total-sent="5120",total-size="9880"@}
18158 +download,@{section=".text",section-sent="5632",section-size="6668",
18159 total-sent="5632",total-size="9880"@}
18160 +download,@{section=".text",section-sent="6144",section-size="6668",
18161 total-sent="6144",total-size="9880"@}
18162 +download,@{section=".text",section-sent="6656",section-size="6668",
18163 total-sent="6656",total-size="9880"@}
18164 +download,@{section=".init",section-size="28",total-size="9880"@}
18165 +download,@{section=".fini",section-size="28",total-size="9880"@}
18166 +download,@{section=".data",section-size="3156",total-size="9880"@}
18167 +download,@{section=".data",section-sent="512",section-size="3156",
18168 total-sent="7236",total-size="9880"@}
18169 +download,@{section=".data",section-sent="1024",section-size="3156",
18170 total-sent="7748",total-size="9880"@}
18171 +download,@{section=".data",section-sent="1536",section-size="3156",
18172 total-sent="8260",total-size="9880"@}
18173 +download,@{section=".data",section-sent="2048",section-size="3156",
18174 total-sent="8772",total-size="9880"@}
18175 +download,@{section=".data",section-sent="2560",section-size="3156",
18176 total-sent="9284",total-size="9880"@}
18177 +download,@{section=".data",section-sent="3072",section-size="3156",
18178 total-sent="9796",total-size="9880"@}
18179 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
18185 @subheading The @code{-target-exec-status} Command
18186 @findex -target-exec-status
18188 @subsubheading Synopsis
18191 -target-exec-status
18194 Provide information on the state of the target (whether it is running or
18195 not, for instance).
18197 @subsubheading @value{GDBN} Command
18199 There's no equivalent @value{GDBN} command.
18201 @subsubheading Example
18205 @subheading The @code{-target-list-available-targets} Command
18206 @findex -target-list-available-targets
18208 @subsubheading Synopsis
18211 -target-list-available-targets
18214 List the possible targets to connect to.
18216 @subsubheading @value{GDBN} Command
18218 The corresponding @value{GDBN} command is @samp{help target}.
18220 @subsubheading Example
18224 @subheading The @code{-target-list-current-targets} Command
18225 @findex -target-list-current-targets
18227 @subsubheading Synopsis
18230 -target-list-current-targets
18233 Describe the current target.
18235 @subsubheading @value{GDBN} Command
18237 The corresponding information is printed by @samp{info file} (among
18240 @subsubheading Example
18244 @subheading The @code{-target-list-parameters} Command
18245 @findex -target-list-parameters
18247 @subsubheading Synopsis
18250 -target-list-parameters
18255 @subsubheading @value{GDBN} Command
18259 @subsubheading Example
18263 @subheading The @code{-target-select} Command
18264 @findex -target-select
18266 @subsubheading Synopsis
18269 -target-select @var{type} @var{parameters @dots{}}
18272 Connect @value{GDBN} to the remote target. This command takes two args:
18276 The type of target, for instance @samp{async}, @samp{remote}, etc.
18277 @item @var{parameters}
18278 Device names, host names and the like. @xref{Target Commands, ,
18279 Commands for managing targets}, for more details.
18282 The output is a connection notification, followed by the address at
18283 which the target program is, in the following form:
18286 ^connected,addr="@var{address}",func="@var{function name}",
18287 args=[@var{arg list}]
18290 @subsubheading @value{GDBN} Command
18292 The corresponding @value{GDBN} command is @samp{target}.
18294 @subsubheading Example
18298 -target-select async /dev/ttya
18299 ^connected,addr="0xfe00a300",func="??",args=[]
18303 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18304 @node GDB/MI Thread Commands
18305 @section @sc{gdb/mi} Thread Commands
18308 @subheading The @code{-thread-info} Command
18309 @findex -thread-info
18311 @subsubheading Synopsis
18317 @subsubheading @value{GDBN} command
18321 @subsubheading Example
18325 @subheading The @code{-thread-list-all-threads} Command
18326 @findex -thread-list-all-threads
18328 @subsubheading Synopsis
18331 -thread-list-all-threads
18334 @subsubheading @value{GDBN} Command
18336 The equivalent @value{GDBN} command is @samp{info threads}.
18338 @subsubheading Example
18342 @subheading The @code{-thread-list-ids} Command
18343 @findex -thread-list-ids
18345 @subsubheading Synopsis
18351 Produces a list of the currently known @value{GDBN} thread ids. At the
18352 end of the list it also prints the total number of such threads.
18354 @subsubheading @value{GDBN} Command
18356 Part of @samp{info threads} supplies the same information.
18358 @subsubheading Example
18360 No threads present, besides the main process:
18365 ^done,thread-ids=@{@},number-of-threads="0"
18375 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18376 number-of-threads="3"
18381 @subheading The @code{-thread-select} Command
18382 @findex -thread-select
18384 @subsubheading Synopsis
18387 -thread-select @var{threadnum}
18390 Make @var{threadnum} the current thread. It prints the number of the new
18391 current thread, and the topmost frame for that thread.
18393 @subsubheading @value{GDBN} Command
18395 The corresponding @value{GDBN} command is @samp{thread}.
18397 @subsubheading Example
18404 *stopped,reason="end-stepping-range",thread-id="2",line="187",
18405 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
18409 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18410 number-of-threads="3"
18413 ^done,new-thread-id="3",
18414 frame=@{level="0",func="vprintf",
18415 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
18416 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
18420 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18421 @node GDB/MI Tracepoint Commands
18422 @section @sc{gdb/mi} Tracepoint Commands
18424 The tracepoint commands are not yet implemented.
18426 @c @subheading -trace-actions
18428 @c @subheading -trace-delete
18430 @c @subheading -trace-disable
18432 @c @subheading -trace-dump
18434 @c @subheading -trace-enable
18436 @c @subheading -trace-exists
18438 @c @subheading -trace-find
18440 @c @subheading -trace-frame-number
18442 @c @subheading -trace-info
18444 @c @subheading -trace-insert
18446 @c @subheading -trace-list
18448 @c @subheading -trace-pass-count
18450 @c @subheading -trace-save
18452 @c @subheading -trace-start
18454 @c @subheading -trace-stop
18457 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18458 @node GDB/MI Variable Objects
18459 @section @sc{gdb/mi} Variable Objects
18462 @subheading Motivation for Variable Objects in @sc{gdb/mi}
18464 For the implementation of a variable debugger window (locals, watched
18465 expressions, etc.), we are proposing the adaptation of the existing code
18466 used by @code{Insight}.
18468 The two main reasons for that are:
18472 It has been proven in practice (it is already on its second generation).
18475 It will shorten development time (needless to say how important it is
18479 The original interface was designed to be used by Tcl code, so it was
18480 slightly changed so it could be used through @sc{gdb/mi}. This section
18481 describes the @sc{gdb/mi} operations that will be available and gives some
18482 hints about their use.
18484 @emph{Note}: In addition to the set of operations described here, we
18485 expect the @sc{gui} implementation of a variable window to require, at
18486 least, the following operations:
18489 @item @code{-gdb-show} @code{output-radix}
18490 @item @code{-stack-list-arguments}
18491 @item @code{-stack-list-locals}
18492 @item @code{-stack-select-frame}
18495 @subheading Introduction to Variable Objects in @sc{gdb/mi}
18497 @cindex variable objects in @sc{gdb/mi}
18498 The basic idea behind variable objects is the creation of a named object
18499 to represent a variable, an expression, a memory location or even a CPU
18500 register. For each object created, a set of operations is available for
18501 examining or changing its properties.
18503 Furthermore, complex data types, such as C structures, are represented
18504 in a tree format. For instance, the @code{struct} type variable is the
18505 root and the children will represent the struct members. If a child
18506 is itself of a complex type, it will also have children of its own.
18507 Appropriate language differences are handled for C, C@t{++} and Java.
18509 When returning the actual values of the objects, this facility allows
18510 for the individual selection of the display format used in the result
18511 creation. It can be chosen among: binary, decimal, hexadecimal, octal
18512 and natural. Natural refers to a default format automatically
18513 chosen based on the variable type (like decimal for an @code{int}, hex
18514 for pointers, etc.).
18516 The following is the complete set of @sc{gdb/mi} operations defined to
18517 access this functionality:
18519 @multitable @columnfractions .4 .6
18520 @item @strong{Operation}
18521 @tab @strong{Description}
18523 @item @code{-var-create}
18524 @tab create a variable object
18525 @item @code{-var-delete}
18526 @tab delete the variable object and its children
18527 @item @code{-var-set-format}
18528 @tab set the display format of this variable
18529 @item @code{-var-show-format}
18530 @tab show the display format of this variable
18531 @item @code{-var-info-num-children}
18532 @tab tells how many children this object has
18533 @item @code{-var-list-children}
18534 @tab return a list of the object's children
18535 @item @code{-var-info-type}
18536 @tab show the type of this variable object
18537 @item @code{-var-info-expression}
18538 @tab print what this variable object represents
18539 @item @code{-var-show-attributes}
18540 @tab is this variable editable? does it exist here?
18541 @item @code{-var-evaluate-expression}
18542 @tab get the value of this variable
18543 @item @code{-var-assign}
18544 @tab set the value of this variable
18545 @item @code{-var-update}
18546 @tab update the variable and its children
18549 In the next subsection we describe each operation in detail and suggest
18550 how it can be used.
18552 @subheading Description And Use of Operations on Variable Objects
18554 @subheading The @code{-var-create} Command
18555 @findex -var-create
18557 @subsubheading Synopsis
18560 -var-create @{@var{name} | "-"@}
18561 @{@var{frame-addr} | "*"@} @var{expression}
18564 This operation creates a variable object, which allows the monitoring of
18565 a variable, the result of an expression, a memory cell or a CPU
18568 The @var{name} parameter is the string by which the object can be
18569 referenced. It must be unique. If @samp{-} is specified, the varobj
18570 system will generate a string ``varNNNNNN'' automatically. It will be
18571 unique provided that one does not specify @var{name} on that format.
18572 The command fails if a duplicate name is found.
18574 The frame under which the expression should be evaluated can be
18575 specified by @var{frame-addr}. A @samp{*} indicates that the current
18576 frame should be used.
18578 @var{expression} is any expression valid on the current language set (must not
18579 begin with a @samp{*}), or one of the following:
18583 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
18586 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
18589 @samp{$@var{regname}} --- a CPU register name
18592 @subsubheading Result
18594 This operation returns the name, number of children and the type of the
18595 object created. Type is returned as a string as the ones generated by
18596 the @value{GDBN} CLI:
18599 name="@var{name}",numchild="N",type="@var{type}"
18603 @subheading The @code{-var-delete} Command
18604 @findex -var-delete
18606 @subsubheading Synopsis
18609 -var-delete @var{name}
18612 Deletes a previously created variable object and all of its children.
18614 Returns an error if the object @var{name} is not found.
18617 @subheading The @code{-var-set-format} Command
18618 @findex -var-set-format
18620 @subsubheading Synopsis
18623 -var-set-format @var{name} @var{format-spec}
18626 Sets the output format for the value of the object @var{name} to be
18629 The syntax for the @var{format-spec} is as follows:
18632 @var{format-spec} @expansion{}
18633 @{binary | decimal | hexadecimal | octal | natural@}
18637 @subheading The @code{-var-show-format} Command
18638 @findex -var-show-format
18640 @subsubheading Synopsis
18643 -var-show-format @var{name}
18646 Returns the format used to display the value of the object @var{name}.
18649 @var{format} @expansion{}
18654 @subheading The @code{-var-info-num-children} Command
18655 @findex -var-info-num-children
18657 @subsubheading Synopsis
18660 -var-info-num-children @var{name}
18663 Returns the number of children of a variable object @var{name}:
18670 @subheading The @code{-var-list-children} Command
18671 @findex -var-list-children
18673 @subsubheading Synopsis
18676 -var-list-children [@var{print-values}] @var{name}
18679 Returns a list of the children of the specified variable object. With
18680 just the variable object name as an argument or with an optional
18681 preceding argument of 0 or @code{--no-values}, prints only the names of the
18682 variables. With an optional preceding argument of 1 or @code{--all-values},
18683 also prints their values.
18685 @subsubheading Example
18689 -var-list-children n
18690 numchild=@var{n},children=[@{name=@var{name},
18691 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
18693 -var-list-children --all-values n
18694 numchild=@var{n},children=[@{name=@var{name},
18695 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
18699 @subheading The @code{-var-info-type} Command
18700 @findex -var-info-type
18702 @subsubheading Synopsis
18705 -var-info-type @var{name}
18708 Returns the type of the specified variable @var{name}. The type is
18709 returned as a string in the same format as it is output by the
18713 type=@var{typename}
18717 @subheading The @code{-var-info-expression} Command
18718 @findex -var-info-expression
18720 @subsubheading Synopsis
18723 -var-info-expression @var{name}
18726 Returns what is represented by the variable object @var{name}:
18729 lang=@var{lang-spec},exp=@var{expression}
18733 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
18735 @subheading The @code{-var-show-attributes} Command
18736 @findex -var-show-attributes
18738 @subsubheading Synopsis
18741 -var-show-attributes @var{name}
18744 List attributes of the specified variable object @var{name}:
18747 status=@var{attr} [ ( ,@var{attr} )* ]
18751 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
18753 @subheading The @code{-var-evaluate-expression} Command
18754 @findex -var-evaluate-expression
18756 @subsubheading Synopsis
18759 -var-evaluate-expression @var{name}
18762 Evaluates the expression that is represented by the specified variable
18763 object and returns its value as a string in the current format specified
18770 Note that one must invoke @code{-var-list-children} for a variable
18771 before the value of a child variable can be evaluated.
18773 @subheading The @code{-var-assign} Command
18774 @findex -var-assign
18776 @subsubheading Synopsis
18779 -var-assign @var{name} @var{expression}
18782 Assigns the value of @var{expression} to the variable object specified
18783 by @var{name}. The object must be @samp{editable}. If the variable's
18784 value is altered by the assign, the variable will show up in any
18785 subsequent @code{-var-update} list.
18787 @subsubheading Example
18795 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
18799 @subheading The @code{-var-update} Command
18800 @findex -var-update
18802 @subsubheading Synopsis
18805 -var-update @{@var{name} | "*"@}
18808 Update the value of the variable object @var{name} by evaluating its
18809 expression after fetching all the new values from memory or registers.
18810 A @samp{*} causes all existing variable objects to be updated.
18814 @chapter @value{GDBN} Annotations
18816 This chapter describes annotations in @value{GDBN}. Annotations were
18817 designed to interface @value{GDBN} to graphical user interfaces or other
18818 similar programs which want to interact with @value{GDBN} at a
18819 relatively high level.
18821 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
18825 This is Edition @value{EDITION}, @value{DATE}.
18829 * Annotations Overview:: What annotations are; the general syntax.
18830 * Server Prefix:: Issuing a command without affecting user state.
18831 * Prompting:: Annotations marking @value{GDBN}'s need for input.
18832 * Errors:: Annotations for error messages.
18833 * Invalidation:: Some annotations describe things now invalid.
18834 * Annotations for Running::
18835 Whether the program is running, how it stopped, etc.
18836 * Source Annotations:: Annotations describing source code.
18839 @node Annotations Overview
18840 @section What is an Annotation?
18841 @cindex annotations
18843 Annotations start with a newline character, two @samp{control-z}
18844 characters, and the name of the annotation. If there is no additional
18845 information associated with this annotation, the name of the annotation
18846 is followed immediately by a newline. If there is additional
18847 information, the name of the annotation is followed by a space, the
18848 additional information, and a newline. The additional information
18849 cannot contain newline characters.
18851 Any output not beginning with a newline and two @samp{control-z}
18852 characters denotes literal output from @value{GDBN}. Currently there is
18853 no need for @value{GDBN} to output a newline followed by two
18854 @samp{control-z} characters, but if there was such a need, the
18855 annotations could be extended with an @samp{escape} annotation which
18856 means those three characters as output.
18858 The annotation @var{level}, which is specified using the
18859 @option{--annotate} command line option (@pxref{Mode Options}), controls
18860 how much information @value{GDBN} prints together with its prompt,
18861 values of expressions, source lines, and other types of output. Level 0
18862 is for no anntations, level 1 is for use when @value{GDBN} is run as a
18863 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
18864 for programs that control @value{GDBN}, and level 2 annotations have
18865 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
18866 Interface, annotate, GDB's Obsolete Annotations}). This chapter
18867 describes level 3 annotations.
18869 A simple example of starting up @value{GDBN} with annotations is:
18872 $ @kbd{gdb --annotate=3}
18874 Copyright 2003 Free Software Foundation, Inc.
18875 GDB is free software, covered by the GNU General Public License,
18876 and you are welcome to change it and/or distribute copies of it
18877 under certain conditions.
18878 Type "show copying" to see the conditions.
18879 There is absolutely no warranty for GDB. Type "show warranty"
18881 This GDB was configured as "i386-pc-linux-gnu"
18892 Here @samp{quit} is input to @value{GDBN}; the rest is output from
18893 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
18894 denotes a @samp{control-z} character) are annotations; the rest is
18895 output from @value{GDBN}.
18897 @node Server Prefix
18898 @section The Server Prefix
18899 @cindex server prefix for annotations
18901 To issue a command to @value{GDBN} without affecting certain aspects of
18902 the state which is seen by users, prefix it with @samp{server }. This
18903 means that this command will not affect the command history, nor will it
18904 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
18905 pressed on a line by itself.
18907 The server prefix does not affect the recording of values into the value
18908 history; to print a value without recording it into the value history,
18909 use the @code{output} command instead of the @code{print} command.
18912 @section Annotation for @value{GDBN} Input
18914 @cindex annotations for prompts
18915 When @value{GDBN} prompts for input, it annotates this fact so it is possible
18916 to know when to send output, when the output from a given command is
18919 Different kinds of input each have a different @dfn{input type}. Each
18920 input type has three annotations: a @code{pre-} annotation, which
18921 denotes the beginning of any prompt which is being output, a plain
18922 annotation, which denotes the end of the prompt, and then a @code{post-}
18923 annotation which denotes the end of any echo which may (or may not) be
18924 associated with the input. For example, the @code{prompt} input type
18925 features the following annotations:
18933 The input types are
18938 @findex post-prompt
18940 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
18942 @findex pre-commands
18944 @findex post-commands
18946 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
18947 command. The annotations are repeated for each command which is input.
18949 @findex pre-overload-choice
18950 @findex overload-choice
18951 @findex post-overload-choice
18952 @item overload-choice
18953 When @value{GDBN} wants the user to select between various overloaded functions.
18959 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
18961 @findex pre-prompt-for-continue
18962 @findex prompt-for-continue
18963 @findex post-prompt-for-continue
18964 @item prompt-for-continue
18965 When @value{GDBN} is asking the user to press return to continue. Note: Don't
18966 expect this to work well; instead use @code{set height 0} to disable
18967 prompting. This is because the counting of lines is buggy in the
18968 presence of annotations.
18973 @cindex annotations for errors, warnings and interrupts
18980 This annotation occurs right before @value{GDBN} responds to an interrupt.
18987 This annotation occurs right before @value{GDBN} responds to an error.
18989 Quit and error annotations indicate that any annotations which @value{GDBN} was
18990 in the middle of may end abruptly. For example, if a
18991 @code{value-history-begin} annotation is followed by a @code{error}, one
18992 cannot expect to receive the matching @code{value-history-end}. One
18993 cannot expect not to receive it either, however; an error annotation
18994 does not necessarily mean that @value{GDBN} is immediately returning all the way
18997 @findex error-begin
18998 A quit or error annotation may be preceded by
19004 Any output between that and the quit or error annotation is the error
19007 Warning messages are not yet annotated.
19008 @c If we want to change that, need to fix warning(), type_error(),
19009 @c range_error(), and possibly other places.
19012 @section Invalidation Notices
19014 @cindex annotations for invalidation messages
19015 The following annotations say that certain pieces of state may have
19019 @findex frames-invalid
19020 @item ^Z^Zframes-invalid
19022 The frames (for example, output from the @code{backtrace} command) may
19025 @findex breakpoints-invalid
19026 @item ^Z^Zbreakpoints-invalid
19028 The breakpoints may have changed. For example, the user just added or
19029 deleted a breakpoint.
19032 @node Annotations for Running
19033 @section Running the Program
19034 @cindex annotations for running programs
19038 When the program starts executing due to a @value{GDBN} command such as
19039 @code{step} or @code{continue},
19045 is output. When the program stops,
19051 is output. Before the @code{stopped} annotation, a variety of
19052 annotations describe how the program stopped.
19056 @item ^Z^Zexited @var{exit-status}
19057 The program exited, and @var{exit-status} is the exit status (zero for
19058 successful exit, otherwise nonzero).
19061 @findex signal-name
19062 @findex signal-name-end
19063 @findex signal-string
19064 @findex signal-string-end
19065 @item ^Z^Zsignalled
19066 The program exited with a signal. After the @code{^Z^Zsignalled}, the
19067 annotation continues:
19073 ^Z^Zsignal-name-end
19077 ^Z^Zsignal-string-end
19082 where @var{name} is the name of the signal, such as @code{SIGILL} or
19083 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
19084 as @code{Illegal Instruction} or @code{Segmentation fault}.
19085 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
19086 user's benefit and have no particular format.
19090 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
19091 just saying that the program received the signal, not that it was
19092 terminated with it.
19095 @item ^Z^Zbreakpoint @var{number}
19096 The program hit breakpoint number @var{number}.
19099 @item ^Z^Zwatchpoint @var{number}
19100 The program hit watchpoint number @var{number}.
19103 @node Source Annotations
19104 @section Displaying Source
19105 @cindex annotations for source display
19108 The following annotation is used instead of displaying source code:
19111 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
19114 where @var{filename} is an absolute file name indicating which source
19115 file, @var{line} is the line number within that file (where 1 is the
19116 first line in the file), @var{character} is the character position
19117 within the file (where 0 is the first character in the file) (for most
19118 debug formats this will necessarily point to the beginning of a line),
19119 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
19120 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
19121 @var{addr} is the address in the target program associated with the
19122 source which is being displayed. @var{addr} is in the form @samp{0x}
19123 followed by one or more lowercase hex digits (note that this does not
19124 depend on the language).
19127 @chapter Reporting Bugs in @value{GDBN}
19128 @cindex bugs in @value{GDBN}
19129 @cindex reporting bugs in @value{GDBN}
19131 Your bug reports play an essential role in making @value{GDBN} reliable.
19133 Reporting a bug may help you by bringing a solution to your problem, or it
19134 may not. But in any case the principal function of a bug report is to help
19135 the entire community by making the next version of @value{GDBN} work better. Bug
19136 reports are your contribution to the maintenance of @value{GDBN}.
19138 In order for a bug report to serve its purpose, you must include the
19139 information that enables us to fix the bug.
19142 * Bug Criteria:: Have you found a bug?
19143 * Bug Reporting:: How to report bugs
19147 @section Have you found a bug?
19148 @cindex bug criteria
19150 If you are not sure whether you have found a bug, here are some guidelines:
19153 @cindex fatal signal
19154 @cindex debugger crash
19155 @cindex crash of debugger
19157 If the debugger gets a fatal signal, for any input whatever, that is a
19158 @value{GDBN} bug. Reliable debuggers never crash.
19160 @cindex error on valid input
19162 If @value{GDBN} produces an error message for valid input, that is a
19163 bug. (Note that if you're cross debugging, the problem may also be
19164 somewhere in the connection to the target.)
19166 @cindex invalid input
19168 If @value{GDBN} does not produce an error message for invalid input,
19169 that is a bug. However, you should note that your idea of
19170 ``invalid input'' might be our idea of ``an extension'' or ``support
19171 for traditional practice''.
19174 If you are an experienced user of debugging tools, your suggestions
19175 for improvement of @value{GDBN} are welcome in any case.
19178 @node Bug Reporting
19179 @section How to report bugs
19180 @cindex bug reports
19181 @cindex @value{GDBN} bugs, reporting
19183 A number of companies and individuals offer support for @sc{gnu} products.
19184 If you obtained @value{GDBN} from a support organization, we recommend you
19185 contact that organization first.
19187 You can find contact information for many support companies and
19188 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
19190 @c should add a web page ref...
19192 In any event, we also recommend that you submit bug reports for
19193 @value{GDBN}. The prefered method is to submit them directly using
19194 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
19195 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
19198 @strong{Do not send bug reports to @samp{info-gdb}, or to
19199 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
19200 not want to receive bug reports. Those that do have arranged to receive
19203 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
19204 serves as a repeater. The mailing list and the newsgroup carry exactly
19205 the same messages. Often people think of posting bug reports to the
19206 newsgroup instead of mailing them. This appears to work, but it has one
19207 problem which can be crucial: a newsgroup posting often lacks a mail
19208 path back to the sender. Thus, if we need to ask for more information,
19209 we may be unable to reach you. For this reason, it is better to send
19210 bug reports to the mailing list.
19212 The fundamental principle of reporting bugs usefully is this:
19213 @strong{report all the facts}. If you are not sure whether to state a
19214 fact or leave it out, state it!
19216 Often people omit facts because they think they know what causes the
19217 problem and assume that some details do not matter. Thus, you might
19218 assume that the name of the variable you use in an example does not matter.
19219 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
19220 stray memory reference which happens to fetch from the location where that
19221 name is stored in memory; perhaps, if the name were different, the contents
19222 of that location would fool the debugger into doing the right thing despite
19223 the bug. Play it safe and give a specific, complete example. That is the
19224 easiest thing for you to do, and the most helpful.
19226 Keep in mind that the purpose of a bug report is to enable us to fix the
19227 bug. It may be that the bug has been reported previously, but neither
19228 you nor we can know that unless your bug report is complete and
19231 Sometimes people give a few sketchy facts and ask, ``Does this ring a
19232 bell?'' Those bug reports are useless, and we urge everyone to
19233 @emph{refuse to respond to them} except to chide the sender to report
19236 To enable us to fix the bug, you should include all these things:
19240 The version of @value{GDBN}. @value{GDBN} announces it if you start
19241 with no arguments; you can also print it at any time using @code{show
19244 Without this, we will not know whether there is any point in looking for
19245 the bug in the current version of @value{GDBN}.
19248 The type of machine you are using, and the operating system name and
19252 What compiler (and its version) was used to compile @value{GDBN}---e.g.
19253 ``@value{GCC}--2.8.1''.
19256 What compiler (and its version) was used to compile the program you are
19257 debugging---e.g. ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
19258 C Compiler''. For GCC, you can say @code{gcc --version} to get this
19259 information; for other compilers, see the documentation for those
19263 The command arguments you gave the compiler to compile your example and
19264 observe the bug. For example, did you use @samp{-O}? To guarantee
19265 you will not omit something important, list them all. A copy of the
19266 Makefile (or the output from make) is sufficient.
19268 If we were to try to guess the arguments, we would probably guess wrong
19269 and then we might not encounter the bug.
19272 A complete input script, and all necessary source files, that will
19276 A description of what behavior you observe that you believe is
19277 incorrect. For example, ``It gets a fatal signal.''
19279 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
19280 will certainly notice it. But if the bug is incorrect output, we might
19281 not notice unless it is glaringly wrong. You might as well not give us
19282 a chance to make a mistake.
19284 Even if the problem you experience is a fatal signal, you should still
19285 say so explicitly. Suppose something strange is going on, such as, your
19286 copy of @value{GDBN} is out of synch, or you have encountered a bug in
19287 the C library on your system. (This has happened!) Your copy might
19288 crash and ours would not. If you told us to expect a crash, then when
19289 ours fails to crash, we would know that the bug was not happening for
19290 us. If you had not told us to expect a crash, then we would not be able
19291 to draw any conclusion from our observations.
19294 @cindex recording a session script
19295 To collect all this information, you can use a session recording program
19296 such as @command{script}, which is available on many Unix systems.
19297 Just run your @value{GDBN} session inside @command{script} and then
19298 include the @file{typescript} file with your bug report.
19300 Another way to record a @value{GDBN} session is to run @value{GDBN}
19301 inside Emacs and then save the entire buffer to a file.
19304 If you wish to suggest changes to the @value{GDBN} source, send us context
19305 diffs. If you even discuss something in the @value{GDBN} source, refer to
19306 it by context, not by line number.
19308 The line numbers in our development sources will not match those in your
19309 sources. Your line numbers would convey no useful information to us.
19313 Here are some things that are not necessary:
19317 A description of the envelope of the bug.
19319 Often people who encounter a bug spend a lot of time investigating
19320 which changes to the input file will make the bug go away and which
19321 changes will not affect it.
19323 This is often time consuming and not very useful, because the way we
19324 will find the bug is by running a single example under the debugger
19325 with breakpoints, not by pure deduction from a series of examples.
19326 We recommend that you save your time for something else.
19328 Of course, if you can find a simpler example to report @emph{instead}
19329 of the original one, that is a convenience for us. Errors in the
19330 output will be easier to spot, running under the debugger will take
19331 less time, and so on.
19333 However, simplification is not vital; if you do not want to do this,
19334 report the bug anyway and send us the entire test case you used.
19337 A patch for the bug.
19339 A patch for the bug does help us if it is a good one. But do not omit
19340 the necessary information, such as the test case, on the assumption that
19341 a patch is all we need. We might see problems with your patch and decide
19342 to fix the problem another way, or we might not understand it at all.
19344 Sometimes with a program as complicated as @value{GDBN} it is very hard to
19345 construct an example that will make the program follow a certain path
19346 through the code. If you do not send us the example, we will not be able
19347 to construct one, so we will not be able to verify that the bug is fixed.
19349 And if we cannot understand what bug you are trying to fix, or why your
19350 patch should be an improvement, we will not install it. A test case will
19351 help us to understand.
19354 A guess about what the bug is or what it depends on.
19356 Such guesses are usually wrong. Even we cannot guess right about such
19357 things without first using the debugger to find the facts.
19360 @c The readline documentation is distributed with the readline code
19361 @c and consists of the two following files:
19363 @c inc-hist.texinfo
19364 @c Use -I with makeinfo to point to the appropriate directory,
19365 @c environment var TEXINPUTS with TeX.
19366 @include rluser.texinfo
19367 @include inc-hist.texinfo
19370 @node Formatting Documentation
19371 @appendix Formatting Documentation
19373 @cindex @value{GDBN} reference card
19374 @cindex reference card
19375 The @value{GDBN} 4 release includes an already-formatted reference card, ready
19376 for printing with PostScript or Ghostscript, in the @file{gdb}
19377 subdirectory of the main source directory@footnote{In
19378 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
19379 release.}. If you can use PostScript or Ghostscript with your printer,
19380 you can print the reference card immediately with @file{refcard.ps}.
19382 The release also includes the source for the reference card. You
19383 can format it, using @TeX{}, by typing:
19389 The @value{GDBN} reference card is designed to print in @dfn{landscape}
19390 mode on US ``letter'' size paper;
19391 that is, on a sheet 11 inches wide by 8.5 inches
19392 high. You will need to specify this form of printing as an option to
19393 your @sc{dvi} output program.
19395 @cindex documentation
19397 All the documentation for @value{GDBN} comes as part of the machine-readable
19398 distribution. The documentation is written in Texinfo format, which is
19399 a documentation system that uses a single source file to produce both
19400 on-line information and a printed manual. You can use one of the Info
19401 formatting commands to create the on-line version of the documentation
19402 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
19404 @value{GDBN} includes an already formatted copy of the on-line Info
19405 version of this manual in the @file{gdb} subdirectory. The main Info
19406 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
19407 subordinate files matching @samp{gdb.info*} in the same directory. If
19408 necessary, you can print out these files, or read them with any editor;
19409 but they are easier to read using the @code{info} subsystem in @sc{gnu}
19410 Emacs or the standalone @code{info} program, available as part of the
19411 @sc{gnu} Texinfo distribution.
19413 If you want to format these Info files yourself, you need one of the
19414 Info formatting programs, such as @code{texinfo-format-buffer} or
19417 If you have @code{makeinfo} installed, and are in the top level
19418 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
19419 version @value{GDBVN}), you can make the Info file by typing:
19426 If you want to typeset and print copies of this manual, you need @TeX{},
19427 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
19428 Texinfo definitions file.
19430 @TeX{} is a typesetting program; it does not print files directly, but
19431 produces output files called @sc{dvi} files. To print a typeset
19432 document, you need a program to print @sc{dvi} files. If your system
19433 has @TeX{} installed, chances are it has such a program. The precise
19434 command to use depends on your system; @kbd{lpr -d} is common; another
19435 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
19436 require a file name without any extension or a @samp{.dvi} extension.
19438 @TeX{} also requires a macro definitions file called
19439 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
19440 written in Texinfo format. On its own, @TeX{} cannot either read or
19441 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
19442 and is located in the @file{gdb-@var{version-number}/texinfo}
19445 If you have @TeX{} and a @sc{dvi} printer program installed, you can
19446 typeset and print this manual. First switch to the the @file{gdb}
19447 subdirectory of the main source directory (for example, to
19448 @file{gdb-@value{GDBVN}/gdb}) and type:
19454 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
19456 @node Installing GDB
19457 @appendix Installing @value{GDBN}
19458 @cindex configuring @value{GDBN}
19459 @cindex installation
19460 @cindex configuring @value{GDBN}, and source tree subdirectories
19462 @value{GDBN} comes with a @code{configure} script that automates the process
19463 of preparing @value{GDBN} for installation; you can then use @code{make} to
19464 build the @code{gdb} program.
19466 @c irrelevant in info file; it's as current as the code it lives with.
19467 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
19468 look at the @file{README} file in the sources; we may have improved the
19469 installation procedures since publishing this manual.}
19472 The @value{GDBN} distribution includes all the source code you need for
19473 @value{GDBN} in a single directory, whose name is usually composed by
19474 appending the version number to @samp{gdb}.
19476 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
19477 @file{gdb-@value{GDBVN}} directory. That directory contains:
19480 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
19481 script for configuring @value{GDBN} and all its supporting libraries
19483 @item gdb-@value{GDBVN}/gdb
19484 the source specific to @value{GDBN} itself
19486 @item gdb-@value{GDBVN}/bfd
19487 source for the Binary File Descriptor library
19489 @item gdb-@value{GDBVN}/include
19490 @sc{gnu} include files
19492 @item gdb-@value{GDBVN}/libiberty
19493 source for the @samp{-liberty} free software library
19495 @item gdb-@value{GDBVN}/opcodes
19496 source for the library of opcode tables and disassemblers
19498 @item gdb-@value{GDBVN}/readline
19499 source for the @sc{gnu} command-line interface
19501 @item gdb-@value{GDBVN}/glob
19502 source for the @sc{gnu} filename pattern-matching subroutine
19504 @item gdb-@value{GDBVN}/mmalloc
19505 source for the @sc{gnu} memory-mapped malloc package
19508 The simplest way to configure and build @value{GDBN} is to run @code{configure}
19509 from the @file{gdb-@var{version-number}} source directory, which in
19510 this example is the @file{gdb-@value{GDBVN}} directory.
19512 First switch to the @file{gdb-@var{version-number}} source directory
19513 if you are not already in it; then run @code{configure}. Pass the
19514 identifier for the platform on which @value{GDBN} will run as an
19520 cd gdb-@value{GDBVN}
19521 ./configure @var{host}
19526 where @var{host} is an identifier such as @samp{sun4} or
19527 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
19528 (You can often leave off @var{host}; @code{configure} tries to guess the
19529 correct value by examining your system.)
19531 Running @samp{configure @var{host}} and then running @code{make} builds the
19532 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
19533 libraries, then @code{gdb} itself. The configured source files, and the
19534 binaries, are left in the corresponding source directories.
19537 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
19538 system does not recognize this automatically when you run a different
19539 shell, you may need to run @code{sh} on it explicitly:
19542 sh configure @var{host}
19545 If you run @code{configure} from a directory that contains source
19546 directories for multiple libraries or programs, such as the
19547 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
19548 creates configuration files for every directory level underneath (unless
19549 you tell it not to, with the @samp{--norecursion} option).
19551 You should run the @code{configure} script from the top directory in the
19552 source tree, the @file{gdb-@var{version-number}} directory. If you run
19553 @code{configure} from one of the subdirectories, you will configure only
19554 that subdirectory. That is usually not what you want. In particular,
19555 if you run the first @code{configure} from the @file{gdb} subdirectory
19556 of the @file{gdb-@var{version-number}} directory, you will omit the
19557 configuration of @file{bfd}, @file{readline}, and other sibling
19558 directories of the @file{gdb} subdirectory. This leads to build errors
19559 about missing include files such as @file{bfd/bfd.h}.
19561 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
19562 However, you should make sure that the shell on your path (named by
19563 the @samp{SHELL} environment variable) is publicly readable. Remember
19564 that @value{GDBN} uses the shell to start your program---some systems refuse to
19565 let @value{GDBN} debug child processes whose programs are not readable.
19568 * Separate Objdir:: Compiling @value{GDBN} in another directory
19569 * Config Names:: Specifying names for hosts and targets
19570 * Configure Options:: Summary of options for configure
19573 @node Separate Objdir
19574 @section Compiling @value{GDBN} in another directory
19576 If you want to run @value{GDBN} versions for several host or target machines,
19577 you need a different @code{gdb} compiled for each combination of
19578 host and target. @code{configure} is designed to make this easy by
19579 allowing you to generate each configuration in a separate subdirectory,
19580 rather than in the source directory. If your @code{make} program
19581 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
19582 @code{make} in each of these directories builds the @code{gdb}
19583 program specified there.
19585 To build @code{gdb} in a separate directory, run @code{configure}
19586 with the @samp{--srcdir} option to specify where to find the source.
19587 (You also need to specify a path to find @code{configure}
19588 itself from your working directory. If the path to @code{configure}
19589 would be the same as the argument to @samp{--srcdir}, you can leave out
19590 the @samp{--srcdir} option; it is assumed.)
19592 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
19593 separate directory for a Sun 4 like this:
19597 cd gdb-@value{GDBVN}
19600 ../gdb-@value{GDBVN}/configure sun4
19605 When @code{configure} builds a configuration using a remote source
19606 directory, it creates a tree for the binaries with the same structure
19607 (and using the same names) as the tree under the source directory. In
19608 the example, you'd find the Sun 4 library @file{libiberty.a} in the
19609 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
19610 @file{gdb-sun4/gdb}.
19612 Make sure that your path to the @file{configure} script has just one
19613 instance of @file{gdb} in it. If your path to @file{configure} looks
19614 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
19615 one subdirectory of @value{GDBN}, not the whole package. This leads to
19616 build errors about missing include files such as @file{bfd/bfd.h}.
19618 One popular reason to build several @value{GDBN} configurations in separate
19619 directories is to configure @value{GDBN} for cross-compiling (where
19620 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
19621 programs that run on another machine---the @dfn{target}).
19622 You specify a cross-debugging target by
19623 giving the @samp{--target=@var{target}} option to @code{configure}.
19625 When you run @code{make} to build a program or library, you must run
19626 it in a configured directory---whatever directory you were in when you
19627 called @code{configure} (or one of its subdirectories).
19629 The @code{Makefile} that @code{configure} generates in each source
19630 directory also runs recursively. If you type @code{make} in a source
19631 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
19632 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
19633 will build all the required libraries, and then build GDB.
19635 When you have multiple hosts or targets configured in separate
19636 directories, you can run @code{make} on them in parallel (for example,
19637 if they are NFS-mounted on each of the hosts); they will not interfere
19641 @section Specifying names for hosts and targets
19643 The specifications used for hosts and targets in the @code{configure}
19644 script are based on a three-part naming scheme, but some short predefined
19645 aliases are also supported. The full naming scheme encodes three pieces
19646 of information in the following pattern:
19649 @var{architecture}-@var{vendor}-@var{os}
19652 For example, you can use the alias @code{sun4} as a @var{host} argument,
19653 or as the value for @var{target} in a @code{--target=@var{target}}
19654 option. The equivalent full name is @samp{sparc-sun-sunos4}.
19656 The @code{configure} script accompanying @value{GDBN} does not provide
19657 any query facility to list all supported host and target names or
19658 aliases. @code{configure} calls the Bourne shell script
19659 @code{config.sub} to map abbreviations to full names; you can read the
19660 script, if you wish, or you can use it to test your guesses on
19661 abbreviations---for example:
19664 % sh config.sub i386-linux
19666 % sh config.sub alpha-linux
19667 alpha-unknown-linux-gnu
19668 % sh config.sub hp9k700
19670 % sh config.sub sun4
19671 sparc-sun-sunos4.1.1
19672 % sh config.sub sun3
19673 m68k-sun-sunos4.1.1
19674 % sh config.sub i986v
19675 Invalid configuration `i986v': machine `i986v' not recognized
19679 @code{config.sub} is also distributed in the @value{GDBN} source
19680 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
19682 @node Configure Options
19683 @section @code{configure} options
19685 Here is a summary of the @code{configure} options and arguments that
19686 are most often useful for building @value{GDBN}. @code{configure} also has
19687 several other options not listed here. @inforef{What Configure
19688 Does,,configure.info}, for a full explanation of @code{configure}.
19691 configure @r{[}--help@r{]}
19692 @r{[}--prefix=@var{dir}@r{]}
19693 @r{[}--exec-prefix=@var{dir}@r{]}
19694 @r{[}--srcdir=@var{dirname}@r{]}
19695 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
19696 @r{[}--target=@var{target}@r{]}
19701 You may introduce options with a single @samp{-} rather than
19702 @samp{--} if you prefer; but you may abbreviate option names if you use
19707 Display a quick summary of how to invoke @code{configure}.
19709 @item --prefix=@var{dir}
19710 Configure the source to install programs and files under directory
19713 @item --exec-prefix=@var{dir}
19714 Configure the source to install programs under directory
19717 @c avoid splitting the warning from the explanation:
19719 @item --srcdir=@var{dirname}
19720 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
19721 @code{make} that implements the @code{VPATH} feature.}@*
19722 Use this option to make configurations in directories separate from the
19723 @value{GDBN} source directories. Among other things, you can use this to
19724 build (or maintain) several configurations simultaneously, in separate
19725 directories. @code{configure} writes configuration specific files in
19726 the current directory, but arranges for them to use the source in the
19727 directory @var{dirname}. @code{configure} creates directories under
19728 the working directory in parallel to the source directories below
19731 @item --norecursion
19732 Configure only the directory level where @code{configure} is executed; do not
19733 propagate configuration to subdirectories.
19735 @item --target=@var{target}
19736 Configure @value{GDBN} for cross-debugging programs running on the specified
19737 @var{target}. Without this option, @value{GDBN} is configured to debug
19738 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
19740 There is no convenient way to generate a list of all available targets.
19742 @item @var{host} @dots{}
19743 Configure @value{GDBN} to run on the specified @var{host}.
19745 There is no convenient way to generate a list of all available hosts.
19748 There are many other options available as well, but they are generally
19749 needed for special purposes only.
19751 @node Maintenance Commands
19752 @appendix Maintenance Commands
19753 @cindex maintenance commands
19754 @cindex internal commands
19756 In addition to commands intended for @value{GDBN} users, @value{GDBN}
19757 includes a number of commands intended for @value{GDBN} developers.
19758 These commands are provided here for reference.
19761 @kindex maint info breakpoints
19762 @item @anchor{maint info breakpoints}maint info breakpoints
19763 Using the same format as @samp{info breakpoints}, display both the
19764 breakpoints you've set explicitly, and those @value{GDBN} is using for
19765 internal purposes. Internal breakpoints are shown with negative
19766 breakpoint numbers. The type column identifies what kind of breakpoint
19771 Normal, explicitly set breakpoint.
19774 Normal, explicitly set watchpoint.
19777 Internal breakpoint, used to handle correctly stepping through
19778 @code{longjmp} calls.
19780 @item longjmp resume
19781 Internal breakpoint at the target of a @code{longjmp}.
19784 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
19787 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
19790 Shared library events.
19794 @kindex maint internal-error
19795 @kindex maint internal-warning
19796 @item maint internal-error
19797 @itemx maint internal-warning
19798 Cause @value{GDBN} to call the internal function @code{internal_error}
19799 or @code{internal_warning} and hence behave as though an internal error
19800 or internal warning has been detected. In addition to reporting the
19801 internal problem, these functions give the user the opportunity to
19802 either quit @value{GDBN} or create a core file of the current
19803 @value{GDBN} session.
19806 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
19807 @dots{}/maint.c:121: internal-error: testing, 1, 2
19808 A problem internal to GDB has been detected. Further
19809 debugging may prove unreliable.
19810 Quit this debugging session? (y or n) @kbd{n}
19811 Create a core file? (y or n) @kbd{n}
19815 Takes an optional parameter that is used as the text of the error or
19818 @kindex maint print dummy-frames
19819 @item maint print dummy-frames
19821 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
19824 (@value{GDBP}) @kbd{b add}
19826 (@value{GDBP}) @kbd{print add(2,3)}
19827 Breakpoint 2, add (a=2, b=3) at @dots{}
19829 The program being debugged stopped while in a function called from GDB.
19831 (@value{GDBP}) @kbd{maint print dummy-frames}
19832 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
19833 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
19834 call_lo=0x01014000 call_hi=0x01014001
19838 Takes an optional file parameter.
19840 @kindex maint print registers
19841 @kindex maint print raw-registers
19842 @kindex maint print cooked-registers
19843 @kindex maint print register-groups
19844 @item maint print registers
19845 @itemx maint print raw-registers
19846 @itemx maint print cooked-registers
19847 @itemx maint print register-groups
19848 Print @value{GDBN}'s internal register data structures.
19850 The command @code{maint print raw-registers} includes the contents of
19851 the raw register cache; the command @code{maint print cooked-registers}
19852 includes the (cooked) value of all registers; and the command
19853 @code{maint print register-groups} includes the groups that each
19854 register is a member of. @xref{Registers,, Registers, gdbint,
19855 @value{GDBN} Internals}.
19857 Takes an optional file parameter.
19859 @kindex maint print reggroups
19860 @item maint print reggroups
19861 Print @value{GDBN}'s internal register group data structures.
19863 Takes an optional file parameter.
19866 (@value{GDBP}) @kbd{maint print reggroups}
19877 @kindex maint set profile
19878 @kindex maint show profile
19879 @cindex profiling GDB
19880 @item maint set profile
19881 @itemx maint show profile
19882 Control profiling of @value{GDBN}.
19884 Profiling will be disabled until you use the @samp{maint set profile}
19885 command to enable it. When you enable profiling, the system will begin
19886 collecting timing and execution count data; when you disable profiling or
19887 exit @value{GDBN}, the results will be written to a log file. Remember that
19888 if you use profiling, @value{GDBN} will overwrite the profiling log file
19889 (often called @file{gmon.out}). If you have a record of important profiling
19890 data in a @file{gmon.out} file, be sure to move it to a safe location.
19892 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
19893 compiled with the @samp{-pg} compiler option.
19895 @kindex maint set dwarf2 max-cache-age
19896 @kindex maint show dwarf2 max-cache-age
19897 @item maint set dwarf2 max-cache-age
19898 @itemx maint show dwarf2 max-cache-age
19899 Control the DWARF 2 compilation unit cache.
19901 In object files with inter-compilation-unit references, such as those
19902 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
19903 reader needs to frequently refer to previously read compilation units.
19904 This setting controls how long a compilation unit will remain in the cache
19905 if it is not referenced. Setting it to zero disables caching, which will
19906 slow down @value{GDBN} startup but reduce memory consumption.
19911 @node Remote Protocol
19912 @appendix @value{GDBN} Remote Serial Protocol
19917 * Stop Reply Packets::
19918 * General Query Packets::
19919 * Register Packet Format::
19921 * File-I/O remote protocol extension::
19927 There may be occasions when you need to know something about the
19928 protocol---for example, if there is only one serial port to your target
19929 machine, you might want your program to do something special if it
19930 recognizes a packet meant for @value{GDBN}.
19932 In the examples below, @samp{->} and @samp{<-} are used to indicate
19933 transmitted and received data respectfully.
19935 @cindex protocol, @value{GDBN} remote serial
19936 @cindex serial protocol, @value{GDBN} remote
19937 @cindex remote serial protocol
19938 All @value{GDBN} commands and responses (other than acknowledgments) are
19939 sent as a @var{packet}. A @var{packet} is introduced with the character
19940 @samp{$}, the actual @var{packet-data}, and the terminating character
19941 @samp{#} followed by a two-digit @var{checksum}:
19944 @code{$}@var{packet-data}@code{#}@var{checksum}
19948 @cindex checksum, for @value{GDBN} remote
19950 The two-digit @var{checksum} is computed as the modulo 256 sum of all
19951 characters between the leading @samp{$} and the trailing @samp{#} (an
19952 eight bit unsigned checksum).
19954 Implementors should note that prior to @value{GDBN} 5.0 the protocol
19955 specification also included an optional two-digit @var{sequence-id}:
19958 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
19961 @cindex sequence-id, for @value{GDBN} remote
19963 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
19964 has never output @var{sequence-id}s. Stubs that handle packets added
19965 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
19967 @cindex acknowledgment, for @value{GDBN} remote
19968 When either the host or the target machine receives a packet, the first
19969 response expected is an acknowledgment: either @samp{+} (to indicate
19970 the package was received correctly) or @samp{-} (to request
19974 -> @code{$}@var{packet-data}@code{#}@var{checksum}
19979 The host (@value{GDBN}) sends @var{command}s, and the target (the
19980 debugging stub incorporated in your program) sends a @var{response}. In
19981 the case of step and continue @var{command}s, the response is only sent
19982 when the operation has completed (the target has again stopped).
19984 @var{packet-data} consists of a sequence of characters with the
19985 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
19988 Fields within the packet should be separated using @samp{,} @samp{;} or
19989 @cindex remote protocol, field separator
19990 @samp{:}. Except where otherwise noted all numbers are represented in
19991 @sc{hex} with leading zeros suppressed.
19993 Implementors should note that prior to @value{GDBN} 5.0, the character
19994 @samp{:} could not appear as the third character in a packet (as it
19995 would potentially conflict with the @var{sequence-id}).
19997 Response @var{data} can be run-length encoded to save space. A @samp{*}
19998 means that the next character is an @sc{ascii} encoding giving a repeat count
19999 which stands for that many repetitions of the character preceding the
20000 @samp{*}. The encoding is @code{n+29}, yielding a printable character
20001 where @code{n >=3} (which is where rle starts to win). The printable
20002 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
20003 value greater than 126 should not be used.
20010 means the same as "0000".
20012 The error response returned for some packets includes a two character
20013 error number. That number is not well defined.
20015 For any @var{command} not supported by the stub, an empty response
20016 (@samp{$#00}) should be returned. That way it is possible to extend the
20017 protocol. A newer @value{GDBN} can tell if a packet is supported based
20020 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
20021 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
20027 The following table provides a complete list of all currently defined
20028 @var{command}s and their corresponding response @var{data}.
20032 @item @code{!} --- extended mode
20033 @cindex @code{!} packet
20035 Enable extended mode. In extended mode, the remote server is made
20036 persistent. The @samp{R} packet is used to restart the program being
20042 The remote target both supports and has enabled extended mode.
20045 @item @code{?} --- last signal
20046 @cindex @code{?} packet
20048 Indicate the reason the target halted. The reply is the same as for
20052 @xref{Stop Reply Packets}, for the reply specifications.
20054 @item @code{a} --- reserved
20056 Reserved for future use.
20058 @item @code{A}@var{arglen}@code{,}@var{argnum}@code{,}@var{arg}@code{,@dots{}} --- set program arguments @strong{(reserved)}
20059 @cindex @code{A} packet
20061 Initialized @samp{argv[]} array passed into program. @var{arglen}
20062 specifies the number of bytes in the hex encoded byte stream @var{arg}.
20063 See @code{gdbserver} for more details.
20071 @item @code{b}@var{baud} --- set baud @strong{(deprecated)}
20072 @cindex @code{b} packet
20074 Change the serial line speed to @var{baud}.
20076 JTC: @emph{When does the transport layer state change? When it's
20077 received, or after the ACK is transmitted. In either case, there are
20078 problems if the command or the acknowledgment packet is dropped.}
20080 Stan: @emph{If people really wanted to add something like this, and get
20081 it working for the first time, they ought to modify ser-unix.c to send
20082 some kind of out-of-band message to a specially-setup stub and have the
20083 switch happen "in between" packets, so that from remote protocol's point
20084 of view, nothing actually happened.}
20086 @item @code{B}@var{addr},@var{mode} --- set breakpoint @strong{(deprecated)}
20087 @cindex @code{B} packet
20089 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
20090 breakpoint at @var{addr}.
20092 This packet has been replaced by the @samp{Z} and @samp{z} packets
20093 (@pxref{insert breakpoint or watchpoint packet}).
20095 @item @code{c}@var{addr} --- continue
20096 @cindex @code{c} packet
20098 @var{addr} is address to resume. If @var{addr} is omitted, resume at
20102 @xref{Stop Reply Packets}, for the reply specifications.
20104 @item @code{C}@var{sig}@code{;}@var{addr} --- continue with signal
20105 @cindex @code{C} packet
20107 Continue with signal @var{sig} (hex signal number). If
20108 @code{;}@var{addr} is omitted, resume at same address.
20111 @xref{Stop Reply Packets}, for the reply specifications.
20113 @item @code{d} --- toggle debug @strong{(deprecated)}
20114 @cindex @code{d} packet
20118 @item @code{D} --- detach
20119 @cindex @code{D} packet
20121 Detach @value{GDBN} from the remote system. Sent to the remote target
20122 before @value{GDBN} disconnects via the @code{detach} command.
20126 @item @emph{no response}
20127 @value{GDBN} does not check for any response after sending this packet.
20130 @item @code{e} --- reserved
20132 Reserved for future use.
20134 @item @code{E} --- reserved
20136 Reserved for future use.
20138 @item @code{f} --- reserved
20140 Reserved for future use.
20142 @item @code{F}@var{RC}@code{,}@var{EE}@code{,}@var{CF}@code{;}@var{XX} --- Reply to target's F packet.
20143 @cindex @code{F} packet
20145 This packet is send by @value{GDBN} as reply to a @code{F} request packet
20146 sent by the target. This is part of the File-I/O protocol extension.
20147 @xref{File-I/O remote protocol extension}, for the specification.
20149 @item @code{g} --- read registers
20150 @anchor{read registers packet}
20151 @cindex @code{g} packet
20153 Read general registers.
20157 @item @var{XX@dots{}}
20158 Each byte of register data is described by two hex digits. The bytes
20159 with the register are transmitted in target byte order. The size of
20160 each register and their position within the @samp{g} @var{packet} are
20161 determined by the @value{GDBN} internal macros
20162 @var{DEPRECATED_REGISTER_RAW_SIZE} and @var{REGISTER_NAME} macros. The
20163 specification of several standard @code{g} packets is specified below.
20168 @item @code{G}@var{XX@dots{}} --- write regs
20169 @cindex @code{G} packet
20171 @xref{read registers packet}, for a description of the @var{XX@dots{}}
20182 @item @code{h} --- reserved
20184 Reserved for future use.
20186 @item @code{H}@var{c}@var{t@dots{}} --- set thread
20187 @cindex @code{H} packet
20189 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
20190 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
20191 should be @samp{c} for step and continue operations, @samp{g} for other
20192 operations. The thread designator @var{t@dots{}} may be -1, meaning all
20193 the threads, a thread number, or zero which means pick any thread.
20204 @c 'H': How restrictive (or permissive) is the thread model. If a
20205 @c thread is selected and stopped, are other threads allowed
20206 @c to continue to execute? As I mentioned above, I think the
20207 @c semantics of each command when a thread is selected must be
20208 @c described. For example:
20210 @c 'g': If the stub supports threads and a specific thread is
20211 @c selected, returns the register block from that thread;
20212 @c otherwise returns current registers.
20214 @c 'G' If the stub supports threads and a specific thread is
20215 @c selected, sets the registers of the register block of
20216 @c that thread; otherwise sets current registers.
20218 @item @code{i}@var{addr}@code{,}@var{nnn} --- cycle step @strong{(draft)}
20219 @anchor{cycle step packet}
20220 @cindex @code{i} packet
20222 Step the remote target by a single clock cycle. If @code{,}@var{nnn} is
20223 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
20224 step starting at that address.
20226 @item @code{I} --- signal then cycle step @strong{(reserved)}
20227 @cindex @code{I} packet
20229 @xref{step with signal packet}. @xref{cycle step packet}.
20231 @item @code{j} --- reserved
20233 Reserved for future use.
20235 @item @code{J} --- reserved
20237 Reserved for future use.
20239 @item @code{k} --- kill request
20240 @cindex @code{k} packet
20242 FIXME: @emph{There is no description of how to operate when a specific
20243 thread context has been selected (i.e.@: does 'k' kill only that
20246 @item @code{K} --- reserved
20248 Reserved for future use.
20250 @item @code{l} --- reserved
20252 Reserved for future use.
20254 @item @code{L} --- reserved
20256 Reserved for future use.
20258 @item @code{m}@var{addr}@code{,}@var{length} --- read memory
20259 @cindex @code{m} packet
20261 Read @var{length} bytes of memory starting at address @var{addr}.
20262 Neither @value{GDBN} nor the stub assume that sized memory transfers are
20263 assumed using word aligned accesses. FIXME: @emph{A word aligned memory
20264 transfer mechanism is needed.}
20268 @item @var{XX@dots{}}
20269 @var{XX@dots{}} is mem contents. Can be fewer bytes than requested if able
20270 to read only part of the data. Neither @value{GDBN} nor the stub assume
20271 that sized memory transfers are assumed using word aligned
20272 accesses. FIXME: @emph{A word aligned memory transfer mechanism is
20278 @item @code{M}@var{addr},@var{length}@code{:}@var{XX@dots{}} --- write mem
20279 @cindex @code{M} packet
20281 Write @var{length} bytes of memory starting at address @var{addr}.
20282 @var{XX@dots{}} is the data.
20289 for an error (this includes the case where only part of the data was
20293 @item @code{n} --- reserved
20295 Reserved for future use.
20297 @item @code{N} --- reserved
20299 Reserved for future use.
20301 @item @code{o} --- reserved
20303 Reserved for future use.
20305 @item @code{O} --- reserved
20307 @item @code{p}@var{hex number of register} --- read register packet
20308 @cindex @code{p} packet
20310 @xref{read registers packet}, for a description of how the returned
20311 register value is encoded.
20315 @item @var{XX@dots{}}
20316 the register's value
20320 Indicating an unrecognized @var{query}.
20323 @item @code{P}@var{n@dots{}}@code{=}@var{r@dots{}} --- write register
20324 @anchor{write register packet}
20325 @cindex @code{P} packet
20327 Write register @var{n@dots{}} with value @var{r@dots{}}, which contains two hex
20328 digits for each byte in the register (target byte order).
20338 @item @code{q}@var{query} --- general query
20339 @anchor{general query packet}
20340 @cindex @code{q} packet
20342 Request info about @var{query}. In general @value{GDBN} queries have a
20343 leading upper case letter. Custom vendor queries should use a company
20344 prefix (in lower case) ex: @samp{qfsf.var}. @var{query} may optionally
20345 be followed by a @samp{,} or @samp{;} separated list. Stubs must ensure
20346 that they match the full @var{query} name.
20350 @item @var{XX@dots{}}
20351 Hex encoded data from query. The reply can not be empty.
20355 Indicating an unrecognized @var{query}.
20358 @item @code{Q}@var{var}@code{=}@var{val} --- general set
20359 @cindex @code{Q} packet
20361 Set value of @var{var} to @var{val}.
20363 @xref{general query packet}, for a discussion of naming conventions.
20365 @item @code{r} --- reset @strong{(deprecated)}
20366 @cindex @code{r} packet
20368 Reset the entire system.
20370 @item @code{R}@var{XX} --- remote restart
20371 @cindex @code{R} packet
20373 Restart the program being debugged. @var{XX}, while needed, is ignored.
20374 This packet is only available in extended mode.
20378 @item @emph{no reply}
20379 The @samp{R} packet has no reply.
20382 @item @code{s}@var{addr} --- step
20383 @cindex @code{s} packet
20385 @var{addr} is address to resume. If @var{addr} is omitted, resume at
20389 @xref{Stop Reply Packets}, for the reply specifications.
20391 @item @code{S}@var{sig}@code{;}@var{addr} --- step with signal
20392 @anchor{step with signal packet}
20393 @cindex @code{S} packet
20395 Like @samp{C} but step not continue.
20398 @xref{Stop Reply Packets}, for the reply specifications.
20400 @item @code{t}@var{addr}@code{:}@var{PP}@code{,}@var{MM} --- search
20401 @cindex @code{t} packet
20403 Search backwards starting at address @var{addr} for a match with pattern
20404 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
20405 @var{addr} must be at least 3 digits.
20407 @item @code{T}@var{XX} --- thread alive
20408 @cindex @code{T} packet
20410 Find out if the thread XX is alive.
20415 thread is still alive
20420 @item @code{u} --- reserved
20422 Reserved for future use.
20424 @item @code{U} --- reserved
20426 Reserved for future use.
20428 @item @code{v} --- verbose packet prefix
20430 Packets starting with @code{v} are identified by a multi-letter name,
20431 up to the first @code{;} or @code{?} (or the end of the packet).
20433 @item @code{vCont}[;@var{action}[@code{:}@var{tid}]]... --- extended resume
20434 @cindex @code{vCont} packet
20436 Resume the inferior. Different actions may be specified for each thread.
20437 If an action is specified with no @var{tid}, then it is applied to any
20438 threads that don't have a specific action specified; if no default action is
20439 specified then other threads should remain stopped. Specifying multiple
20440 default actions is an error; specifying no actions is also an error.
20441 Thread IDs are specified in hexadecimal. Currently supported actions are:
20447 Continue with signal @var{sig}. @var{sig} should be two hex digits.
20451 Step with signal @var{sig}. @var{sig} should be two hex digits.
20454 The optional @var{addr} argument normally associated with these packets is
20455 not supported in @code{vCont}.
20458 @xref{Stop Reply Packets}, for the reply specifications.
20460 @item @code{vCont?} --- extended resume query
20461 @cindex @code{vCont?} packet
20463 Query support for the @code{vCont} packet.
20467 @item @code{vCont}[;@var{action}]...
20468 The @code{vCont} packet is supported. Each @var{action} is a supported
20469 command in the @code{vCont} packet.
20471 The @code{vCont} packet is not supported.
20474 @item @code{V} --- reserved
20476 Reserved for future use.
20478 @item @code{w} --- reserved
20480 Reserved for future use.
20482 @item @code{W} --- reserved
20484 Reserved for future use.
20486 @item @code{x} --- reserved
20488 Reserved for future use.
20490 @item @code{X}@var{addr}@code{,}@var{length}@var{:}@var{XX@dots{}} --- write mem (binary)
20491 @cindex @code{X} packet
20493 @var{addr} is address, @var{length} is number of bytes, @var{XX@dots{}}
20494 is binary data. The characters @code{$}, @code{#}, and @code{0x7d} are
20495 escaped using @code{0x7d}.
20505 @item @code{y} --- reserved
20507 Reserved for future use.
20509 @item @code{Y} reserved
20511 Reserved for future use.
20513 @item @code{z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- remove breakpoint or watchpoint @strong{(draft)}
20514 @itemx @code{Z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- insert breakpoint or watchpoint @strong{(draft)}
20515 @anchor{insert breakpoint or watchpoint packet}
20516 @cindex @code{z} packet
20517 @cindex @code{Z} packets
20519 Insert (@code{Z}) or remove (@code{z}) a @var{type} breakpoint or
20520 watchpoint starting at address @var{address} and covering the next
20521 @var{length} bytes.
20523 Each breakpoint and watchpoint packet @var{type} is documented
20526 @emph{Implementation notes: A remote target shall return an empty string
20527 for an unrecognized breakpoint or watchpoint packet @var{type}. A
20528 remote target shall support either both or neither of a given
20529 @code{Z}@var{type}@dots{} and @code{z}@var{type}@dots{} packet pair. To
20530 avoid potential problems with duplicate packets, the operations should
20531 be implemented in an idempotent way.}
20533 @item @code{z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- remove memory breakpoint @strong{(draft)}
20534 @item @code{Z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- insert memory breakpoint @strong{(draft)}
20535 @cindex @code{z0} packet
20536 @cindex @code{Z0} packet
20538 Insert (@code{Z0}) or remove (@code{z0}) a memory breakpoint at address
20539 @code{addr} of size @code{length}.
20541 A memory breakpoint is implemented by replacing the instruction at
20542 @var{addr} with a software breakpoint or trap instruction. The
20543 @code{length} is used by targets that indicates the size of the
20544 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
20545 @sc{mips} can insert either a 2 or 4 byte breakpoint).
20547 @emph{Implementation note: It is possible for a target to copy or move
20548 code that contains memory breakpoints (e.g., when implementing
20549 overlays). The behavior of this packet, in the presence of such a
20550 target, is not defined.}
20562 @item @code{z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- remove hardware breakpoint @strong{(draft)}
20563 @item @code{Z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- insert hardware breakpoint @strong{(draft)}
20564 @cindex @code{z1} packet
20565 @cindex @code{Z1} packet
20567 Insert (@code{Z1}) or remove (@code{z1}) a hardware breakpoint at
20568 address @code{addr} of size @code{length}.
20570 A hardware breakpoint is implemented using a mechanism that is not
20571 dependant on being able to modify the target's memory.
20573 @emph{Implementation note: A hardware breakpoint is not affected by code
20586 @item @code{z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- remove write watchpoint @strong{(draft)}
20587 @item @code{Z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- insert write watchpoint @strong{(draft)}
20588 @cindex @code{z2} packet
20589 @cindex @code{Z2} packet
20591 Insert (@code{Z2}) or remove (@code{z2}) a write watchpoint.
20603 @item @code{z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- remove read watchpoint @strong{(draft)}
20604 @item @code{Z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- insert read watchpoint @strong{(draft)}
20605 @cindex @code{z3} packet
20606 @cindex @code{Z3} packet
20608 Insert (@code{Z3}) or remove (@code{z3}) a read watchpoint.
20620 @item @code{z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- remove access watchpoint @strong{(draft)}
20621 @item @code{Z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- insert access watchpoint @strong{(draft)}
20622 @cindex @code{z4} packet
20623 @cindex @code{Z4} packet
20625 Insert (@code{Z4}) or remove (@code{z4}) an access watchpoint.
20639 @node Stop Reply Packets
20640 @section Stop Reply Packets
20641 @cindex stop reply packets
20643 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
20644 receive any of the below as a reply. In the case of the @samp{C},
20645 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
20646 when the target halts. In the below the exact meaning of @samp{signal
20647 number} is poorly defined. In general one of the UNIX signal numbering
20648 conventions is used.
20653 @var{AA} is the signal number
20655 @item @code{T}@var{AA}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}
20656 @cindex @code{T} packet reply
20658 @var{AA} = two hex digit signal number; @var{n...} = register number
20659 (hex), @var{r...} = target byte ordered register contents, size defined
20660 by @code{DEPRECATED_REGISTER_RAW_SIZE}; @var{n...} = @samp{thread},
20661 @var{r...} = thread process ID, this is a hex integer; @var{n...} =
20662 (@samp{watch} | @samp{rwatch} | @samp{awatch}, @var{r...} = data
20663 address, this is a hex integer; @var{n...} = other string not starting
20664 with valid hex digit. @value{GDBN} should ignore this @var{n...},
20665 @var{r...} pair and go on to the next. This way we can extend the
20670 The process exited, and @var{AA} is the exit status. This is only
20671 applicable to certain targets.
20675 The process terminated with signal @var{AA}.
20677 @item O@var{XX@dots{}}
20679 @var{XX@dots{}} is hex encoding of @sc{ascii} data. This can happen at
20680 any time while the program is running and the debugger should continue
20681 to wait for @samp{W}, @samp{T}, etc.
20683 @item F@var{call-id}@code{,}@var{parameter@dots{}}
20685 @var{call-id} is the identifier which says which host system call should
20686 be called. This is just the name of the function. Translation into the
20687 correct system call is only applicable as it's defined in @value{GDBN}.
20688 @xref{File-I/O remote protocol extension}, for a list of implemented
20691 @var{parameter@dots{}} is a list of parameters as defined for this very
20694 The target replies with this packet when it expects @value{GDBN} to call
20695 a host system call on behalf of the target. @value{GDBN} replies with
20696 an appropriate @code{F} packet and keeps up waiting for the next reply
20697 packet from the target. The latest @samp{C}, @samp{c}, @samp{S} or
20698 @samp{s} action is expected to be continued.
20699 @xref{File-I/O remote protocol extension}, for more details.
20703 @node General Query Packets
20704 @section General Query Packets
20706 The following set and query packets have already been defined.
20710 @item @code{q}@code{C} --- current thread
20712 Return the current thread id.
20716 @item @code{QC}@var{pid}
20717 Where @var{pid} is a HEX encoded 16 bit process id.
20719 Any other reply implies the old pid.
20722 @item @code{q}@code{fThreadInfo} -- all thread ids
20724 @code{q}@code{sThreadInfo}
20726 Obtain a list of active thread ids from the target (OS). Since there
20727 may be too many active threads to fit into one reply packet, this query
20728 works iteratively: it may require more than one query/reply sequence to
20729 obtain the entire list of threads. The first query of the sequence will
20730 be the @code{qf}@code{ThreadInfo} query; subsequent queries in the
20731 sequence will be the @code{qs}@code{ThreadInfo} query.
20733 NOTE: replaces the @code{qL} query (see below).
20737 @item @code{m}@var{id}
20739 @item @code{m}@var{id},@var{id}@dots{}
20740 a comma-separated list of thread ids
20742 (lower case 'el') denotes end of list.
20745 In response to each query, the target will reply with a list of one or
20746 more thread ids, in big-endian hex, separated by commas. @value{GDBN}
20747 will respond to each reply with a request for more thread ids (using the
20748 @code{qs} form of the query), until the target responds with @code{l}
20749 (lower-case el, for @code{'last'}).
20751 @item @code{q}@code{ThreadExtraInfo}@code{,}@var{id} --- extra thread info
20753 Where @var{id} is a thread-id in big-endian hex. Obtain a printable
20754 string description of a thread's attributes from the target OS. This
20755 string may contain anything that the target OS thinks is interesting for
20756 @value{GDBN} to tell the user about the thread. The string is displayed
20757 in @value{GDBN}'s @samp{info threads} display. Some examples of
20758 possible thread extra info strings are ``Runnable'', or ``Blocked on
20763 @item @var{XX@dots{}}
20764 Where @var{XX@dots{}} is a hex encoding of @sc{ascii} data, comprising
20765 the printable string containing the extra information about the thread's
20769 @item @code{q}@code{L}@var{startflag}@var{threadcount}@var{nextthread} --- query @var{LIST} or @var{threadLIST} @strong{(deprecated)}
20771 Obtain thread information from RTOS. Where: @var{startflag} (one hex
20772 digit) is one to indicate the first query and zero to indicate a
20773 subsequent query; @var{threadcount} (two hex digits) is the maximum
20774 number of threads the response packet can contain; and @var{nextthread}
20775 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
20776 returned in the response as @var{argthread}.
20778 NOTE: this query is replaced by the @code{q}@code{fThreadInfo} query
20783 @item @code{q}@code{M}@var{count}@var{done}@var{argthread}@var{thread@dots{}}
20784 Where: @var{count} (two hex digits) is the number of threads being
20785 returned; @var{done} (one hex digit) is zero to indicate more threads
20786 and one indicates no further threads; @var{argthreadid} (eight hex
20787 digits) is @var{nextthread} from the request packet; @var{thread@dots{}}
20788 is a sequence of thread IDs from the target. @var{threadid} (eight hex
20789 digits). See @code{remote.c:parse_threadlist_response()}.
20792 @item @code{q}@code{CRC:}@var{addr}@code{,}@var{length} --- compute CRC of memory block
20796 @item @code{E}@var{NN}
20797 An error (such as memory fault)
20798 @item @code{C}@var{CRC32}
20799 A 32 bit cyclic redundancy check of the specified memory region.
20802 @item @code{q}@code{Offsets} --- query sect offs
20804 Get section offsets that the target used when re-locating the downloaded
20805 image. @emph{Note: while a @code{Bss} offset is included in the
20806 response, @value{GDBN} ignores this and instead applies the @code{Data}
20807 offset to the @code{Bss} section.}
20811 @item @code{Text=}@var{xxx}@code{;Data=}@var{yyy}@code{;Bss=}@var{zzz}
20814 @item @code{q}@code{P}@var{mode}@var{threadid} --- thread info request
20816 Returns information on @var{threadid}. Where: @var{mode} is a hex
20817 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
20824 See @code{remote.c:remote_unpack_thread_info_response()}.
20826 @item @code{q}@code{Rcmd,}@var{command} --- remote command
20828 @var{command} (hex encoded) is passed to the local interpreter for
20829 execution. Invalid commands should be reported using the output string.
20830 Before the final result packet, the target may also respond with a
20831 number of intermediate @code{O}@var{output} console output packets.
20832 @emph{Implementors should note that providing access to a stubs's
20833 interpreter may have security implications}.
20838 A command response with no output.
20840 A command response with the hex encoded output string @var{OUTPUT}.
20841 @item @code{E}@var{NN}
20842 Indicate a badly formed request.
20844 When @samp{q}@samp{Rcmd} is not recognized.
20847 @item @code{qSymbol::} --- symbol lookup
20849 Notify the target that @value{GDBN} is prepared to serve symbol lookup
20850 requests. Accept requests from the target for the values of symbols.
20855 The target does not need to look up any (more) symbols.
20856 @item @code{qSymbol:}@var{sym_name}
20857 The target requests the value of symbol @var{sym_name} (hex encoded).
20858 @value{GDBN} may provide the value by using the
20859 @code{qSymbol:}@var{sym_value}:@var{sym_name} message, described below.
20862 @item @code{qSymbol:}@var{sym_value}:@var{sym_name} --- symbol value
20864 Set the value of @var{sym_name} to @var{sym_value}.
20866 @var{sym_name} (hex encoded) is the name of a symbol whose value the
20867 target has previously requested.
20869 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
20870 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
20876 The target does not need to look up any (more) symbols.
20877 @item @code{qSymbol:}@var{sym_name}
20878 The target requests the value of a new symbol @var{sym_name} (hex
20879 encoded). @value{GDBN} will continue to supply the values of symbols
20880 (if available), until the target ceases to request them.
20883 @item @code{qPart}:@var{object}:@code{read}:@var{annex}:@var{offset},@var{length} --- read special data
20885 Read uninterpreted bytes from the target's special data area
20886 identified by the keyword @code{object}.
20887 Request @var{length} bytes starting at @var{offset} bytes into the data.
20888 The content and encoding of @var{annex} is specific to the object;
20889 it can supply additional details about what data to access.
20891 Here are the specific requests of this form defined so far.
20892 All @samp{@code{qPart}:@var{object}:@code{read}:@dots{}}
20893 requests use the same reply formats, listed below.
20896 @item @code{qPart}:@code{auxv}:@code{read}::@var{offset},@var{length}
20897 Access the target's @dfn{auxiliary vector}. @xref{Auxiliary Vector}.
20898 Note @var{annex} must be empty.
20904 The @var{offset} in the request is at the end of the data.
20905 There is no more data to be read.
20907 @item @var{XX@dots{}}
20908 Hex encoded data bytes read.
20909 This may be fewer bytes than the @var{length} in the request.
20912 The request was malformed, or @var{annex} was invalid.
20914 @item @code{E}@var{nn}
20915 The offset was invalid, or there was an error encountered reading the data.
20916 @var{nn} is a hex-encoded @code{errno} value.
20918 @item @code{""} (empty)
20919 An empty reply indicates the @var{object} or @var{annex} string was not
20920 recognized by the stub.
20923 @item @code{qPart}:@var{object}:@code{write}:@var{annex}:@var{offset}:@var{data@dots{}}
20925 Write uninterpreted bytes into the target's special data area
20926 identified by the keyword @code{object},
20927 starting at @var{offset} bytes into the data.
20928 @var{data@dots{}} is the hex-encoded data to be written.
20929 The content and encoding of @var{annex} is specific to the object;
20930 it can supply additional details about what data to access.
20932 No requests of this form are presently in use. This specification
20933 serves as a placeholder to document the common format that new
20934 specific request specifications ought to use.
20939 @var{nn} (hex encoded) is the number of bytes written.
20940 This may be fewer bytes than supplied in the request.
20943 The request was malformed, or @var{annex} was invalid.
20945 @item @code{E}@var{nn}
20946 The offset was invalid, or there was an error encountered writing the data.
20947 @var{nn} is a hex-encoded @code{errno} value.
20949 @item @code{""} (empty)
20950 An empty reply indicates the @var{object} or @var{annex} string was not
20951 recognized by the stub, or that the object does not support writing.
20954 @item @code{qPart}:@var{object}:@var{operation}:@dots{}
20955 Requests of this form may be added in the future. When a stub does
20956 not recognize the @var{object} keyword, or its support for
20957 @var{object} does not recognize the @var{operation} keyword,
20958 the stub must respond with an empty packet.
20961 @node Register Packet Format
20962 @section Register Packet Format
20964 The following @samp{g}/@samp{G} packets have previously been defined.
20965 In the below, some thirty-two bit registers are transferred as
20966 sixty-four bits. Those registers should be zero/sign extended (which?)
20967 to fill the space allocated. Register bytes are transfered in target
20968 byte order. The two nibbles within a register byte are transfered
20969 most-significant - least-significant.
20975 All registers are transfered as thirty-two bit quantities in the order:
20976 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
20977 registers; fsr; fir; fp.
20981 All registers are transfered as sixty-four bit quantities (including
20982 thirty-two bit registers such as @code{sr}). The ordering is the same
20990 Example sequence of a target being re-started. Notice how the restart
20991 does not get any direct output:
20996 @emph{target restarts}
20999 <- @code{T001:1234123412341234}
21003 Example sequence of a target being stepped by a single instruction:
21006 -> @code{G1445@dots{}}
21011 <- @code{T001:1234123412341234}
21015 <- @code{1455@dots{}}
21019 @node File-I/O remote protocol extension
21020 @section File-I/O remote protocol extension
21021 @cindex File-I/O remote protocol extension
21024 * File-I/O Overview::
21025 * Protocol basics::
21026 * The F request packet::
21027 * The F reply packet::
21028 * Memory transfer::
21029 * The Ctrl-C message::
21031 * The isatty call::
21032 * The system call::
21033 * List of supported calls::
21034 * Protocol specific representation of datatypes::
21036 * File-I/O Examples::
21039 @node File-I/O Overview
21040 @subsection File-I/O Overview
21041 @cindex file-i/o overview
21043 The File I/O remote protocol extension (short: File-I/O) allows the
21044 target to use the hosts file system and console I/O when calling various
21045 system calls. System calls on the target system are translated into a
21046 remote protocol packet to the host system which then performs the needed
21047 actions and returns with an adequate response packet to the target system.
21048 This simulates file system operations even on targets that lack file systems.
21050 The protocol is defined host- and target-system independent. It uses
21051 it's own independent representation of datatypes and values. Both,
21052 @value{GDBN} and the target's @value{GDBN} stub are responsible for
21053 translating the system dependent values into the unified protocol values
21054 when data is transmitted.
21056 The communication is synchronous. A system call is possible only
21057 when GDB is waiting for the @samp{C}, @samp{c}, @samp{S} or @samp{s}
21058 packets. While @value{GDBN} handles the request for a system call,
21059 the target is stopped to allow deterministic access to the target's
21060 memory. Therefore File-I/O is not interuptible by target signals. It
21061 is possible to interrupt File-I/O by a user interrupt (Ctrl-C), though.
21063 The target's request to perform a host system call does not finish
21064 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
21065 after finishing the system call, the target returns to continuing the
21066 previous activity (continue, step). No additional continue or step
21067 request from @value{GDBN} is required.
21070 (@value{GDBP}) continue
21071 <- target requests 'system call X'
21072 target is stopped, @value{GDBN} executes system call
21073 -> GDB returns result
21074 ... target continues, GDB returns to wait for the target
21075 <- target hits breakpoint and sends a Txx packet
21078 The protocol is only used for files on the host file system and
21079 for I/O on the console. Character or block special devices, pipes,
21080 named pipes or sockets or any other communication method on the host
21081 system are not supported by this protocol.
21083 @node Protocol basics
21084 @subsection Protocol basics
21085 @cindex protocol basics, file-i/o
21087 The File-I/O protocol uses the @code{F} packet, as request as well
21088 as as reply packet. Since a File-I/O system call can only occur when
21089 @value{GDBN} is waiting for the continuing or stepping target, the
21090 File-I/O request is a reply that @value{GDBN} has to expect as a result
21091 of a former @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
21092 This @code{F} packet contains all information needed to allow @value{GDBN}
21093 to call the appropriate host system call:
21097 A unique identifier for the requested system call.
21100 All parameters to the system call. Pointers are given as addresses
21101 in the target memory address space. Pointers to strings are given as
21102 pointer/length pair. Numerical values are given as they are.
21103 Numerical control values are given in a protocol specific representation.
21107 At that point @value{GDBN} has to perform the following actions.
21111 If parameter pointer values are given, which point to data needed as input
21112 to a system call, @value{GDBN} requests this data from the target with a
21113 standard @code{m} packet request. This additional communication has to be
21114 expected by the target implementation and is handled as any other @code{m}
21118 @value{GDBN} translates all value from protocol representation to host
21119 representation as needed. Datatypes are coerced into the host types.
21122 @value{GDBN} calls the system call
21125 It then coerces datatypes back to protocol representation.
21128 If pointer parameters in the request packet point to buffer space in which
21129 a system call is expected to copy data to, the data is transmitted to the
21130 target using a @code{M} or @code{X} packet. This packet has to be expected
21131 by the target implementation and is handled as any other @code{M} or @code{X}
21136 Eventually @value{GDBN} replies with another @code{F} packet which contains all
21137 necessary information for the target to continue. This at least contains
21144 @code{errno}, if has been changed by the system call.
21151 After having done the needed type and value coercion, the target continues
21152 the latest continue or step action.
21154 @node The F request packet
21155 @subsection The @code{F} request packet
21156 @cindex file-i/o request packet
21157 @cindex @code{F} request packet
21159 The @code{F} request packet has the following format:
21164 @code{F}@var{call-id}@code{,}@var{parameter@dots{}}
21167 @var{call-id} is the identifier to indicate the host system call to be called.
21168 This is just the name of the function.
21170 @var{parameter@dots{}} are the parameters to the system call.
21174 Parameters are hexadecimal integer values, either the real values in case
21175 of scalar datatypes, as pointers to target buffer space in case of compound
21176 datatypes and unspecified memory areas or as pointer/length pairs in case
21177 of string parameters. These are appended to the call-id, each separated
21178 from its predecessor by a comma. All values are transmitted in ASCII
21179 string representation, pointer/length pairs separated by a slash.
21181 @node The F reply packet
21182 @subsection The @code{F} reply packet
21183 @cindex file-i/o reply packet
21184 @cindex @code{F} reply packet
21186 The @code{F} reply packet has the following format:
21191 @code{F}@var{retcode}@code{,}@var{errno}@code{,}@var{Ctrl-C flag}@code{;}@var{call specific attachment}
21194 @var{retcode} is the return code of the system call as hexadecimal value.
21196 @var{errno} is the errno set by the call, in protocol specific representation.
21197 This parameter can be omitted if the call was successful.
21199 @var{Ctrl-C flag} is only send if the user requested a break. In this
21200 case, @var{errno} must be send as well, even if the call was successful.
21201 The @var{Ctrl-C flag} itself consists of the character 'C':
21208 or, if the call was interupted before the host call has been performed:
21215 assuming 4 is the protocol specific representation of @code{EINTR}.
21219 @node Memory transfer
21220 @subsection Memory transfer
21221 @cindex memory transfer, in file-i/o protocol
21223 Structured data which is transferred using a memory read or write as e.g.@:
21224 a @code{struct stat} is expected to be in a protocol specific format with
21225 all scalar multibyte datatypes being big endian. This should be done by
21226 the target before the @code{F} packet is sent resp.@: by @value{GDBN} before
21227 it transfers memory to the target. Transferred pointers to structured
21228 data should point to the already coerced data at any time.
21230 @node The Ctrl-C message
21231 @subsection The Ctrl-C message
21232 @cindex ctrl-c message, in file-i/o protocol
21234 A special case is, if the @var{Ctrl-C flag} is set in the @value{GDBN}
21235 reply packet. In this case the target should behave, as if it had
21236 gotten a break message. The meaning for the target is ``system call
21237 interupted by @code{SIGINT}''. Consequentially, the target should actually stop
21238 (as with a break message) and return to @value{GDBN} with a @code{T02}
21239 packet. In this case, it's important for the target to know, in which
21240 state the system call was interrupted. Since this action is by design
21241 not an atomic operation, we have to differ between two cases:
21245 The system call hasn't been performed on the host yet.
21248 The system call on the host has been finished.
21252 These two states can be distinguished by the target by the value of the
21253 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
21254 call hasn't been performed. This is equivalent to the @code{EINTR} handling
21255 on POSIX systems. In any other case, the target may presume that the
21256 system call has been finished --- successful or not --- and should behave
21257 as if the break message arrived right after the system call.
21259 @value{GDBN} must behave reliable. If the system call has not been called
21260 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
21261 @code{errno} in the packet. If the system call on the host has been finished
21262 before the user requests a break, the full action must be finshed by
21263 @value{GDBN}. This requires sending @code{M} or @code{X} packets as they fit.
21264 The @code{F} packet may only be send when either nothing has happened
21265 or the full action has been completed.
21268 @subsection Console I/O
21269 @cindex console i/o as part of file-i/o
21271 By default and if not explicitely closed by the target system, the file
21272 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
21273 on the @value{GDBN} console is handled as any other file output operation
21274 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
21275 by @value{GDBN} so that after the target read request from file descriptor
21276 0 all following typing is buffered until either one of the following
21281 The user presses @kbd{Ctrl-C}. The behaviour is as explained above, the
21283 system call is treated as finished.
21286 The user presses @kbd{Enter}. This is treated as end of input with a trailing
21290 The user presses @kbd{Ctrl-D}. This is treated as end of input. No trailing
21291 character, especially no Ctrl-D is appended to the input.
21295 If the user has typed more characters as fit in the buffer given to
21296 the read call, the trailing characters are buffered in @value{GDBN} until
21297 either another @code{read(0, @dots{})} is requested by the target or debugging
21298 is stopped on users request.
21300 @node The isatty call
21301 @subsection The isatty(3) call
21302 @cindex isatty call, file-i/o protocol
21304 A special case in this protocol is the library call @code{isatty} which
21305 is implemented as it's own call inside of this protocol. It returns
21306 1 to the target if the file descriptor given as parameter is attached
21307 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
21308 would require implementing @code{ioctl} and would be more complex than
21311 @node The system call
21312 @subsection The system(3) call
21313 @cindex system call, file-i/o protocol
21315 The other special case in this protocol is the @code{system} call which
21316 is implemented as it's own call, too. @value{GDBN} is taking over the full
21317 task of calling the necessary host calls to perform the @code{system}
21318 call. The return value of @code{system} is simplified before it's returned
21319 to the target. Basically, the only signal transmitted back is @code{EINTR}
21320 in case the user pressed @kbd{Ctrl-C}. Otherwise the return value consists
21321 entirely of the exit status of the called command.
21323 Due to security concerns, the @code{system} call is refused to be called
21324 by @value{GDBN} by default. The user has to allow this call explicitly by
21328 @kindex set remote system-call-allowed 1
21329 @item @code{set remote system-call-allowed 1}
21332 Disabling the @code{system} call is done by
21335 @kindex set remote system-call-allowed 0
21336 @item @code{set remote system-call-allowed 0}
21339 The current setting is shown by typing
21342 @kindex show remote system-call-allowed
21343 @item @code{show remote system-call-allowed}
21346 @node List of supported calls
21347 @subsection List of supported calls
21348 @cindex list of supported file-i/o calls
21365 @unnumberedsubsubsec open
21366 @cindex open, file-i/o system call
21370 int open(const char *pathname, int flags);
21371 int open(const char *pathname, int flags, mode_t mode);
21374 Fopen,pathptr/len,flags,mode
21378 @code{flags} is the bitwise or of the following values:
21382 If the file does not exist it will be created. The host
21383 rules apply as far as file ownership and time stamps
21387 When used with O_CREAT, if the file already exists it is
21388 an error and open() fails.
21391 If the file already exists and the open mode allows
21392 writing (O_RDWR or O_WRONLY is given) it will be
21393 truncated to length 0.
21396 The file is opened in append mode.
21399 The file is opened for reading only.
21402 The file is opened for writing only.
21405 The file is opened for reading and writing.
21408 Each other bit is silently ignored.
21413 @code{mode} is the bitwise or of the following values:
21417 User has read permission.
21420 User has write permission.
21423 Group has read permission.
21426 Group has write permission.
21429 Others have read permission.
21432 Others have write permission.
21435 Each other bit is silently ignored.
21440 @exdent Return value:
21441 open returns the new file descriptor or -1 if an error
21449 pathname already exists and O_CREAT and O_EXCL were used.
21452 pathname refers to a directory.
21455 The requested access is not allowed.
21458 pathname was too long.
21461 A directory component in pathname does not exist.
21464 pathname refers to a device, pipe, named pipe or socket.
21467 pathname refers to a file on a read-only filesystem and
21468 write access was requested.
21471 pathname is an invalid pointer value.
21474 No space on device to create the file.
21477 The process already has the maximum number of files open.
21480 The limit on the total number of files open on the system
21484 The call was interrupted by the user.
21488 @unnumberedsubsubsec close
21489 @cindex close, file-i/o system call
21498 @exdent Return value:
21499 close returns zero on success, or -1 if an error occurred.
21506 fd isn't a valid open file descriptor.
21509 The call was interrupted by the user.
21513 @unnumberedsubsubsec read
21514 @cindex read, file-i/o system call
21518 int read(int fd, void *buf, unsigned int count);
21521 Fread,fd,bufptr,count
21523 @exdent Return value:
21524 On success, the number of bytes read is returned.
21525 Zero indicates end of file. If count is zero, read
21526 returns zero as well. On error, -1 is returned.
21533 fd is not a valid file descriptor or is not open for
21537 buf is an invalid pointer value.
21540 The call was interrupted by the user.
21544 @unnumberedsubsubsec write
21545 @cindex write, file-i/o system call
21549 int write(int fd, const void *buf, unsigned int count);
21552 Fwrite,fd,bufptr,count
21554 @exdent Return value:
21555 On success, the number of bytes written are returned.
21556 Zero indicates nothing was written. On error, -1
21564 fd is not a valid file descriptor or is not open for
21568 buf is an invalid pointer value.
21571 An attempt was made to write a file that exceeds the
21572 host specific maximum file size allowed.
21575 No space on device to write the data.
21578 The call was interrupted by the user.
21582 @unnumberedsubsubsec lseek
21583 @cindex lseek, file-i/o system call
21587 long lseek (int fd, long offset, int flag);
21590 Flseek,fd,offset,flag
21593 @code{flag} is one of:
21597 The offset is set to offset bytes.
21600 The offset is set to its current location plus offset
21604 The offset is set to the size of the file plus offset
21609 @exdent Return value:
21610 On success, the resulting unsigned offset in bytes from
21611 the beginning of the file is returned. Otherwise, a
21612 value of -1 is returned.
21619 fd is not a valid open file descriptor.
21622 fd is associated with the @value{GDBN} console.
21625 flag is not a proper value.
21628 The call was interrupted by the user.
21632 @unnumberedsubsubsec rename
21633 @cindex rename, file-i/o system call
21637 int rename(const char *oldpath, const char *newpath);
21640 Frename,oldpathptr/len,newpathptr/len
21642 @exdent Return value:
21643 On success, zero is returned. On error, -1 is returned.
21650 newpath is an existing directory, but oldpath is not a
21654 newpath is a non-empty directory.
21657 oldpath or newpath is a directory that is in use by some
21661 An attempt was made to make a directory a subdirectory
21665 A component used as a directory in oldpath or new
21666 path is not a directory. Or oldpath is a directory
21667 and newpath exists but is not a directory.
21670 oldpathptr or newpathptr are invalid pointer values.
21673 No access to the file or the path of the file.
21677 oldpath or newpath was too long.
21680 A directory component in oldpath or newpath does not exist.
21683 The file is on a read-only filesystem.
21686 The device containing the file has no room for the new
21690 The call was interrupted by the user.
21694 @unnumberedsubsubsec unlink
21695 @cindex unlink, file-i/o system call
21699 int unlink(const char *pathname);
21702 Funlink,pathnameptr/len
21704 @exdent Return value:
21705 On success, zero is returned. On error, -1 is returned.
21712 No access to the file or the path of the file.
21715 The system does not allow unlinking of directories.
21718 The file pathname cannot be unlinked because it's
21719 being used by another process.
21722 pathnameptr is an invalid pointer value.
21725 pathname was too long.
21728 A directory component in pathname does not exist.
21731 A component of the path is not a directory.
21734 The file is on a read-only filesystem.
21737 The call was interrupted by the user.
21741 @unnumberedsubsubsec stat/fstat
21742 @cindex fstat, file-i/o system call
21743 @cindex stat, file-i/o system call
21747 int stat(const char *pathname, struct stat *buf);
21748 int fstat(int fd, struct stat *buf);
21751 Fstat,pathnameptr/len,bufptr
21754 @exdent Return value:
21755 On success, zero is returned. On error, -1 is returned.
21762 fd is not a valid open file.
21765 A directory component in pathname does not exist or the
21766 path is an empty string.
21769 A component of the path is not a directory.
21772 pathnameptr is an invalid pointer value.
21775 No access to the file or the path of the file.
21778 pathname was too long.
21781 The call was interrupted by the user.
21785 @unnumberedsubsubsec gettimeofday
21786 @cindex gettimeofday, file-i/o system call
21790 int gettimeofday(struct timeval *tv, void *tz);
21793 Fgettimeofday,tvptr,tzptr
21795 @exdent Return value:
21796 On success, 0 is returned, -1 otherwise.
21803 tz is a non-NULL pointer.
21806 tvptr and/or tzptr is an invalid pointer value.
21810 @unnumberedsubsubsec isatty
21811 @cindex isatty, file-i/o system call
21815 int isatty(int fd);
21820 @exdent Return value:
21821 Returns 1 if fd refers to the @value{GDBN} console, 0 otherwise.
21828 The call was interrupted by the user.
21832 @unnumberedsubsubsec system
21833 @cindex system, file-i/o system call
21837 int system(const char *command);
21840 Fsystem,commandptr/len
21842 @exdent Return value:
21843 The value returned is -1 on error and the return status
21844 of the command otherwise. Only the exit status of the
21845 command is returned, which is extracted from the hosts
21846 system return value by calling WEXITSTATUS(retval).
21847 In case /bin/sh could not be executed, 127 is returned.
21854 The call was interrupted by the user.
21857 @node Protocol specific representation of datatypes
21858 @subsection Protocol specific representation of datatypes
21859 @cindex protocol specific representation of datatypes, in file-i/o protocol
21862 * Integral datatypes::
21868 @node Integral datatypes
21869 @unnumberedsubsubsec Integral datatypes
21870 @cindex integral datatypes, in file-i/o protocol
21872 The integral datatypes used in the system calls are
21875 int@r{,} unsigned int@r{,} long@r{,} unsigned long@r{,} mode_t @r{and} time_t
21878 @code{Int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
21879 implemented as 32 bit values in this protocol.
21881 @code{Long} and @code{unsigned long} are implemented as 64 bit types.
21883 @xref{Limits}, for corresponding MIN and MAX values (similar to those
21884 in @file{limits.h}) to allow range checking on host and target.
21886 @code{time_t} datatypes are defined as seconds since the Epoch.
21888 All integral datatypes transferred as part of a memory read or write of a
21889 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
21892 @node Pointer values
21893 @unnumberedsubsubsec Pointer values
21894 @cindex pointer values, in file-i/o protocol
21896 Pointers to target data are transmitted as they are. An exception
21897 is made for pointers to buffers for which the length isn't
21898 transmitted as part of the function call, namely strings. Strings
21899 are transmitted as a pointer/length pair, both as hex values, e.g.@:
21906 which is a pointer to data of length 18 bytes at position 0x1aaf.
21907 The length is defined as the full string length in bytes, including
21908 the trailing null byte. Example:
21911 ``hello, world'' at address 0x123456
21922 @unnumberedsubsubsec struct stat
21923 @cindex struct stat, in file-i/o protocol
21925 The buffer of type struct stat used by the target and @value{GDBN} is defined
21930 unsigned int st_dev; /* device */
21931 unsigned int st_ino; /* inode */
21932 mode_t st_mode; /* protection */
21933 unsigned int st_nlink; /* number of hard links */
21934 unsigned int st_uid; /* user ID of owner */
21935 unsigned int st_gid; /* group ID of owner */
21936 unsigned int st_rdev; /* device type (if inode device) */
21937 unsigned long st_size; /* total size, in bytes */
21938 unsigned long st_blksize; /* blocksize for filesystem I/O */
21939 unsigned long st_blocks; /* number of blocks allocated */
21940 time_t st_atime; /* time of last access */
21941 time_t st_mtime; /* time of last modification */
21942 time_t st_ctime; /* time of last change */
21946 The integral datatypes are conforming to the definitions given in the
21947 approriate section (see @ref{Integral datatypes}, for details) so this
21948 structure is of size 64 bytes.
21950 The values of several fields have a restricted meaning and/or
21957 st_ino: No valid meaning for the target. Transmitted unchanged.
21959 st_mode: Valid mode bits are described in Appendix C. Any other
21960 bits have currently no meaning for the target.
21962 st_uid: No valid meaning for the target. Transmitted unchanged.
21964 st_gid: No valid meaning for the target. Transmitted unchanged.
21966 st_rdev: No valid meaning for the target. Transmitted unchanged.
21968 st_atime, st_mtime, st_ctime:
21969 These values have a host and file system dependent
21970 accuracy. Especially on Windows hosts the file systems
21971 don't support exact timing values.
21974 The target gets a struct stat of the above representation and is
21975 responsible to coerce it to the target representation before
21978 Note that due to size differences between the host and target
21979 representation of stat members, these members could eventually
21980 get truncated on the target.
21982 @node struct timeval
21983 @unnumberedsubsubsec struct timeval
21984 @cindex struct timeval, in file-i/o protocol
21986 The buffer of type struct timeval used by the target and @value{GDBN}
21987 is defined as follows:
21991 time_t tv_sec; /* second */
21992 long tv_usec; /* microsecond */
21996 The integral datatypes are conforming to the definitions given in the
21997 approriate section (see @ref{Integral datatypes}, for details) so this
21998 structure is of size 8 bytes.
22001 @subsection Constants
22002 @cindex constants, in file-i/o protocol
22004 The following values are used for the constants inside of the
22005 protocol. @value{GDBN} and target are resposible to translate these
22006 values before and after the call as needed.
22017 @unnumberedsubsubsec Open flags
22018 @cindex open flags, in file-i/o protocol
22020 All values are given in hexadecimal representation.
22032 @node mode_t values
22033 @unnumberedsubsubsec mode_t values
22034 @cindex mode_t values, in file-i/o protocol
22036 All values are given in octal representation.
22053 @unnumberedsubsubsec Errno values
22054 @cindex errno values, in file-i/o protocol
22056 All values are given in decimal representation.
22081 EUNKNOWN is used as a fallback error value if a host system returns
22082 any error value not in the list of supported error numbers.
22085 @unnumberedsubsubsec Lseek flags
22086 @cindex lseek flags, in file-i/o protocol
22095 @unnumberedsubsubsec Limits
22096 @cindex limits, in file-i/o protocol
22098 All values are given in decimal representation.
22101 INT_MIN -2147483648
22103 UINT_MAX 4294967295
22104 LONG_MIN -9223372036854775808
22105 LONG_MAX 9223372036854775807
22106 ULONG_MAX 18446744073709551615
22109 @node File-I/O Examples
22110 @subsection File-I/O Examples
22111 @cindex file-i/o examples
22113 Example sequence of a write call, file descriptor 3, buffer is at target
22114 address 0x1234, 6 bytes should be written:
22117 <- @code{Fwrite,3,1234,6}
22118 @emph{request memory read from target}
22121 @emph{return "6 bytes written"}
22125 Example sequence of a read call, file descriptor 3, buffer is at target
22126 address 0x1234, 6 bytes should be read:
22129 <- @code{Fread,3,1234,6}
22130 @emph{request memory write to target}
22131 -> @code{X1234,6:XXXXXX}
22132 @emph{return "6 bytes read"}
22136 Example sequence of a read call, call fails on the host due to invalid
22137 file descriptor (EBADF):
22140 <- @code{Fread,3,1234,6}
22144 Example sequence of a read call, user presses Ctrl-C before syscall on
22148 <- @code{Fread,3,1234,6}
22153 Example sequence of a read call, user presses Ctrl-C after syscall on
22157 <- @code{Fread,3,1234,6}
22158 -> @code{X1234,6:XXXXXX}
22162 @include agentexpr.texi
22176 % I think something like @colophon should be in texinfo. In the
22178 \long\def\colophon{\hbox to0pt{}\vfill
22179 \centerline{The body of this manual is set in}
22180 \centerline{\fontname\tenrm,}
22181 \centerline{with headings in {\bf\fontname\tenbf}}
22182 \centerline{and examples in {\tt\fontname\tentt}.}
22183 \centerline{{\it\fontname\tenit\/},}
22184 \centerline{{\bf\fontname\tenbf}, and}
22185 \centerline{{\sl\fontname\tensl\/}}
22186 \centerline{are used for emphasis.}\vfill}
22188 % Blame: doc@cygnus.com, 1991.