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 Programming & development tools.
43 * Gdb: (gdb). The @sc{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 6.0, 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 terminal user interface: Ben Krepp, Richard Title,
449 John Bishop, Susan Macchia, Kathy Mann, Satish Pai, India Paul, Steve
450 Rehrauer, and Elena Zannoni. Kim Haase provided HP-specific
451 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{--async}
1070 Use the asynchronous event loop for the command-line interface.
1071 @value{GDBN} processes all events, such as user keyboard input, via a
1072 special event loop. This allows @value{GDBN} to accept and process user
1073 commands in parallel with the debugged process being
1074 run@footnote{@value{GDBN} built with @sc{djgpp} tools for
1075 MS-DOS/MS-Windows supports this mode of operation, but the event loop is
1076 suspended when the debuggee runs.}, so you don't need to wait for
1077 control to return to @value{GDBN} before you type the next command.
1078 (@emph{Note:} as of version 5.1, the target side of the asynchronous
1079 operation is not yet in place, so @samp{-async} does not work fully
1081 @c FIXME: when the target side of the event loop is done, the above NOTE
1082 @c should be removed.
1084 When the standard input is connected to a terminal device, @value{GDBN}
1085 uses the asynchronous event loop by default, unless disabled by the
1086 @samp{-noasync} option.
1089 @cindex @code{--noasync}
1090 Disable the asynchronous event loop for the command-line interface.
1093 @cindex @code{--args}
1094 Change interpretation of command line so that arguments following the
1095 executable file are passed as command line arguments to the inferior.
1096 This option stops option processing.
1098 @item -baud @var{bps}
1100 @cindex @code{--baud}
1102 Set the line speed (baud rate or bits per second) of any serial
1103 interface used by @value{GDBN} for remote debugging.
1105 @item -tty @var{device}
1106 @itemx -t @var{device}
1107 @cindex @code{--tty}
1109 Run using @var{device} for your program's standard input and output.
1110 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1112 @c resolve the situation of these eventually
1114 @cindex @code{--tui}
1115 Activate the Terminal User Interface when starting.
1116 The Terminal User Interface manages several text windows on the terminal,
1117 showing source, assembly, registers and @value{GDBN} command outputs
1118 (@pxref{TUI, ,@value{GDBN} Text User Interface}).
1119 Do not use this option if you run @value{GDBN} from Emacs
1120 (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1123 @c @cindex @code{--xdb}
1124 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1125 @c For information, see the file @file{xdb_trans.html}, which is usually
1126 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1129 @item -interpreter @var{interp}
1130 @cindex @code{--interpreter}
1131 Use the interpreter @var{interp} for interface with the controlling
1132 program or device. This option is meant to be set by programs which
1133 communicate with @value{GDBN} using it as a back end.
1134 @xref{Interpreters, , Command Interpreters}.
1136 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1137 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1138 The @sc{gdb/mi} Interface}) included in @var{GDBN} version 6.0. The
1139 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3,
1140 can be selected with @samp{--interpreter=mi1}. Earlier @sc{gdb/mi}
1141 interfaces are not supported.
1144 @cindex @code{--write}
1145 Open the executable and core files for both reading and writing. This
1146 is equivalent to the @samp{set write on} command inside @value{GDBN}
1150 @cindex @code{--statistics}
1151 This option causes @value{GDBN} to print statistics about time and
1152 memory usage after it completes each command and returns to the prompt.
1155 @cindex @code{--version}
1156 This option causes @value{GDBN} to print its version number and
1157 no-warranty blurb, and exit.
1162 @section Quitting @value{GDBN}
1163 @cindex exiting @value{GDBN}
1164 @cindex leaving @value{GDBN}
1167 @kindex quit @r{[}@var{expression}@r{]}
1168 @kindex q @r{(@code{quit})}
1169 @item quit @r{[}@var{expression}@r{]}
1171 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1172 @code{q}), or type an end-of-file character (usually @kbd{C-d}). If you
1173 do not supply @var{expression}, @value{GDBN} will terminate normally;
1174 otherwise it will terminate using the result of @var{expression} as the
1179 An interrupt (often @kbd{C-c}) does not exit from @value{GDBN}, but rather
1180 terminates the action of any @value{GDBN} command that is in progress and
1181 returns to @value{GDBN} command level. It is safe to type the interrupt
1182 character at any time because @value{GDBN} does not allow it to take effect
1183 until a time when it is safe.
1185 If you have been using @value{GDBN} to control an attached process or
1186 device, you can release it with the @code{detach} command
1187 (@pxref{Attach, ,Debugging an already-running process}).
1189 @node Shell Commands
1190 @section Shell commands
1192 If you need to execute occasional shell commands during your
1193 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1194 just use the @code{shell} command.
1198 @cindex shell escape
1199 @item shell @var{command string}
1200 Invoke a standard shell to execute @var{command string}.
1201 If it exists, the environment variable @code{SHELL} determines which
1202 shell to run. Otherwise @value{GDBN} uses the default shell
1203 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1206 The utility @code{make} is often needed in development environments.
1207 You do not have to use the @code{shell} command for this purpose in
1212 @cindex calling make
1213 @item make @var{make-args}
1214 Execute the @code{make} program with the specified
1215 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1218 @node Logging output
1219 @section Logging output
1220 @cindex logging @value{GDBN} output
1222 You may want to save the output of @value{GDBN} commands to a file.
1223 There are several commands to control @value{GDBN}'s logging.
1227 @item set logging on
1229 @item set logging off
1231 @item set logging file @var{file}
1232 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1233 @item set logging overwrite [on|off]
1234 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1235 you want @code{set logging on} to overwrite the logfile instead.
1236 @item set logging redirect [on|off]
1237 By default, @value{GDBN} output will go to both the terminal and the logfile.
1238 Set @code{redirect} if you want output to go only to the log file.
1239 @kindex show logging
1241 Show the current values of the logging settings.
1245 @chapter @value{GDBN} Commands
1247 You can abbreviate a @value{GDBN} command to the first few letters of the command
1248 name, if that abbreviation is unambiguous; and you can repeat certain
1249 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1250 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1251 show you the alternatives available, if there is more than one possibility).
1254 * Command Syntax:: How to give commands to @value{GDBN}
1255 * Completion:: Command completion
1256 * Help:: How to ask @value{GDBN} for help
1259 @node Command Syntax
1260 @section Command syntax
1262 A @value{GDBN} command is a single line of input. There is no limit on
1263 how long it can be. It starts with a command name, which is followed by
1264 arguments whose meaning depends on the command name. For example, the
1265 command @code{step} accepts an argument which is the number of times to
1266 step, as in @samp{step 5}. You can also use the @code{step} command
1267 with no arguments. Some commands do not allow any arguments.
1269 @cindex abbreviation
1270 @value{GDBN} command names may always be truncated if that abbreviation is
1271 unambiguous. Other possible command abbreviations are listed in the
1272 documentation for individual commands. In some cases, even ambiguous
1273 abbreviations are allowed; for example, @code{s} is specially defined as
1274 equivalent to @code{step} even though there are other commands whose
1275 names start with @code{s}. You can test abbreviations by using them as
1276 arguments to the @code{help} command.
1278 @cindex repeating commands
1279 @kindex RET @r{(repeat last command)}
1280 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1281 repeat the previous command. Certain commands (for example, @code{run})
1282 will not repeat this way; these are commands whose unintentional
1283 repetition might cause trouble and which you are unlikely to want to
1286 The @code{list} and @code{x} commands, when you repeat them with
1287 @key{RET}, construct new arguments rather than repeating
1288 exactly as typed. This permits easy scanning of source or memory.
1290 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1291 output, in a way similar to the common utility @code{more}
1292 (@pxref{Screen Size,,Screen size}). Since it is easy to press one
1293 @key{RET} too many in this situation, @value{GDBN} disables command
1294 repetition after any command that generates this sort of display.
1296 @kindex # @r{(a comment)}
1298 Any text from a @kbd{#} to the end of the line is a comment; it does
1299 nothing. This is useful mainly in command files (@pxref{Command
1300 Files,,Command files}).
1302 @cindex repeating command sequences
1303 @kindex C-o @r{(operate-and-get-next)}
1304 The @kbd{C-o} binding is useful for repeating a complex sequence of
1305 commands. This command accepts the current line, like @kbd{RET}, and
1306 then fetches the next line relative to the current line from the history
1310 @section Command completion
1313 @cindex word completion
1314 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1315 only one possibility; it can also show you what the valid possibilities
1316 are for the next word in a command, at any time. This works for @value{GDBN}
1317 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1319 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1320 of a word. If there is only one possibility, @value{GDBN} fills in the
1321 word, and waits for you to finish the command (or press @key{RET} to
1322 enter it). For example, if you type
1324 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1325 @c complete accuracy in these examples; space introduced for clarity.
1326 @c If texinfo enhancements make it unnecessary, it would be nice to
1327 @c replace " @key" by "@key" in the following...
1329 (@value{GDBP}) info bre @key{TAB}
1333 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1334 the only @code{info} subcommand beginning with @samp{bre}:
1337 (@value{GDBP}) info breakpoints
1341 You can either press @key{RET} at this point, to run the @code{info
1342 breakpoints} command, or backspace and enter something else, if
1343 @samp{breakpoints} does not look like the command you expected. (If you
1344 were sure you wanted @code{info breakpoints} in the first place, you
1345 might as well just type @key{RET} immediately after @samp{info bre},
1346 to exploit command abbreviations rather than command completion).
1348 If there is more than one possibility for the next word when you press
1349 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1350 characters and try again, or just press @key{TAB} a second time;
1351 @value{GDBN} displays all the possible completions for that word. For
1352 example, you might want to set a breakpoint on a subroutine whose name
1353 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1354 just sounds the bell. Typing @key{TAB} again displays all the
1355 function names in your program that begin with those characters, for
1359 (@value{GDBP}) b make_ @key{TAB}
1360 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1361 make_a_section_from_file make_environ
1362 make_abs_section make_function_type
1363 make_blockvector make_pointer_type
1364 make_cleanup make_reference_type
1365 make_command make_symbol_completion_list
1366 (@value{GDBP}) b make_
1370 After displaying the available possibilities, @value{GDBN} copies your
1371 partial input (@samp{b make_} in the example) so you can finish the
1374 If you just want to see the list of alternatives in the first place, you
1375 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1376 means @kbd{@key{META} ?}. You can type this either by holding down a
1377 key designated as the @key{META} shift on your keyboard (if there is
1378 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1380 @cindex quotes in commands
1381 @cindex completion of quoted strings
1382 Sometimes the string you need, while logically a ``word'', may contain
1383 parentheses or other characters that @value{GDBN} normally excludes from
1384 its notion of a word. To permit word completion to work in this
1385 situation, you may enclose words in @code{'} (single quote marks) in
1386 @value{GDBN} commands.
1388 The most likely situation where you might need this is in typing the
1389 name of a C@t{++} function. This is because C@t{++} allows function
1390 overloading (multiple definitions of the same function, distinguished
1391 by argument type). For example, when you want to set a breakpoint you
1392 may need to distinguish whether you mean the version of @code{name}
1393 that takes an @code{int} parameter, @code{name(int)}, or the version
1394 that takes a @code{float} parameter, @code{name(float)}. To use the
1395 word-completion facilities in this situation, type a single quote
1396 @code{'} at the beginning of the function name. This alerts
1397 @value{GDBN} that it may need to consider more information than usual
1398 when you press @key{TAB} or @kbd{M-?} to request word completion:
1401 (@value{GDBP}) b 'bubble( @kbd{M-?}
1402 bubble(double,double) bubble(int,int)
1403 (@value{GDBP}) b 'bubble(
1406 In some cases, @value{GDBN} can tell that completing a name requires using
1407 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1408 completing as much as it can) if you do not type the quote in the first
1412 (@value{GDBP}) b bub @key{TAB}
1413 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1414 (@value{GDBP}) b 'bubble(
1418 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1419 you have not yet started typing the argument list when you ask for
1420 completion on an overloaded symbol.
1422 For more information about overloaded functions, see @ref{C plus plus
1423 expressions, ,C@t{++} expressions}. You can use the command @code{set
1424 overload-resolution off} to disable overload resolution;
1425 see @ref{Debugging C plus plus, ,@value{GDBN} features for C@t{++}}.
1429 @section Getting help
1430 @cindex online documentation
1433 You can always ask @value{GDBN} itself for information on its commands,
1434 using the command @code{help}.
1437 @kindex h @r{(@code{help})}
1440 You can use @code{help} (abbreviated @code{h}) with no arguments to
1441 display a short list of named classes of commands:
1445 List of classes of commands:
1447 aliases -- Aliases of other commands
1448 breakpoints -- Making program stop at certain points
1449 data -- Examining data
1450 files -- Specifying and examining files
1451 internals -- Maintenance commands
1452 obscure -- Obscure features
1453 running -- Running the program
1454 stack -- Examining the stack
1455 status -- Status inquiries
1456 support -- Support facilities
1457 tracepoints -- Tracing of program execution without@*
1458 stopping the program
1459 user-defined -- User-defined commands
1461 Type "help" followed by a class name for a list of
1462 commands in that class.
1463 Type "help" followed by command name for full
1465 Command name abbreviations are allowed if unambiguous.
1468 @c the above line break eliminates huge line overfull...
1470 @item help @var{class}
1471 Using one of the general help classes as an argument, you can get a
1472 list of the individual commands in that class. For example, here is the
1473 help display for the class @code{status}:
1476 (@value{GDBP}) help status
1481 @c Line break in "show" line falsifies real output, but needed
1482 @c to fit in smallbook page size.
1483 info -- Generic command for showing things
1484 about the program being debugged
1485 show -- Generic command for showing things
1488 Type "help" followed by command name for full
1490 Command name abbreviations are allowed if unambiguous.
1494 @item help @var{command}
1495 With a command name as @code{help} argument, @value{GDBN} displays a
1496 short paragraph on how to use that command.
1499 @item apropos @var{args}
1500 The @code{apropos @var{args}} command searches through all of the @value{GDBN}
1501 commands, and their documentation, for the regular expression specified in
1502 @var{args}. It prints out all matches found. For example:
1513 set symbol-reloading -- Set dynamic symbol table reloading
1514 multiple times in one run
1515 show symbol-reloading -- Show dynamic symbol table reloading
1516 multiple times in one run
1521 @item complete @var{args}
1522 The @code{complete @var{args}} command lists all the possible completions
1523 for the beginning of a command. Use @var{args} to specify the beginning of the
1524 command you want completed. For example:
1530 @noindent results in:
1541 @noindent This is intended for use by @sc{gnu} Emacs.
1544 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1545 and @code{show} to inquire about the state of your program, or the state
1546 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1547 manual introduces each of them in the appropriate context. The listings
1548 under @code{info} and under @code{show} in the Index point to
1549 all the sub-commands. @xref{Index}.
1554 @kindex i @r{(@code{info})}
1556 This command (abbreviated @code{i}) is for describing the state of your
1557 program. For example, you can list the arguments given to your program
1558 with @code{info args}, list the registers currently in use with @code{info
1559 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1560 You can get a complete list of the @code{info} sub-commands with
1561 @w{@code{help info}}.
1565 You can assign the result of an expression to an environment variable with
1566 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1567 @code{set prompt $}.
1571 In contrast to @code{info}, @code{show} is for describing the state of
1572 @value{GDBN} itself.
1573 You can change most of the things you can @code{show}, by using the
1574 related command @code{set}; for example, you can control what number
1575 system is used for displays with @code{set radix}, or simply inquire
1576 which is currently in use with @code{show radix}.
1579 To display all the settable parameters and their current
1580 values, you can use @code{show} with no arguments; you may also use
1581 @code{info set}. Both commands produce the same display.
1582 @c FIXME: "info set" violates the rule that "info" is for state of
1583 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1584 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1588 Here are three miscellaneous @code{show} subcommands, all of which are
1589 exceptional in lacking corresponding @code{set} commands:
1592 @kindex show version
1593 @cindex version number
1595 Show what version of @value{GDBN} is running. You should include this
1596 information in @value{GDBN} bug-reports. If multiple versions of
1597 @value{GDBN} are in use at your site, you may need to determine which
1598 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1599 commands are introduced, and old ones may wither away. Also, many
1600 system vendors ship variant versions of @value{GDBN}, and there are
1601 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1602 The version number is the same as the one announced when you start
1605 @kindex show copying
1607 Display information about permission for copying @value{GDBN}.
1609 @kindex show warranty
1611 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1612 if your version of @value{GDBN} comes with one.
1617 @chapter Running Programs Under @value{GDBN}
1619 When you run a program under @value{GDBN}, you must first generate
1620 debugging information when you compile it.
1622 You may start @value{GDBN} with its arguments, if any, in an environment
1623 of your choice. If you are doing native debugging, you may redirect
1624 your program's input and output, debug an already running process, or
1625 kill a child process.
1628 * Compilation:: Compiling for debugging
1629 * Starting:: Starting your program
1630 * Arguments:: Your program's arguments
1631 * Environment:: Your program's environment
1633 * Working Directory:: Your program's working directory
1634 * Input/Output:: Your program's input and output
1635 * Attach:: Debugging an already-running process
1636 * Kill Process:: Killing the child process
1638 * Threads:: Debugging programs with multiple threads
1639 * Processes:: Debugging programs with multiple processes
1643 @section Compiling for debugging
1645 In order to debug a program effectively, you need to generate
1646 debugging information when you compile it. This debugging information
1647 is stored in the object file; it describes the data type of each
1648 variable or function and the correspondence between source line numbers
1649 and addresses in the executable code.
1651 To request debugging information, specify the @samp{-g} option when you run
1654 Most compilers do not include information about preprocessor macros in
1655 the debugging information if you specify the @option{-g} flag alone,
1656 because this information is rather large. Version 3.1 of @value{NGCC},
1657 the @sc{gnu} C compiler, provides macro information if you specify the
1658 options @option{-gdwarf-2} and @option{-g3}; the former option requests
1659 debugging information in the Dwarf 2 format, and the latter requests
1660 ``extra information''. In the future, we hope to find more compact ways
1661 to represent macro information, so that it can be included with
1664 Many C compilers are unable to handle the @samp{-g} and @samp{-O}
1665 options together. Using those compilers, you cannot generate optimized
1666 executables containing debugging information.
1668 @value{NGCC}, the @sc{gnu} C compiler, supports @samp{-g} with or
1669 without @samp{-O}, making it possible to debug optimized code. We
1670 recommend that you @emph{always} use @samp{-g} whenever you compile a
1671 program. You may think your program is correct, but there is no sense
1672 in pushing your luck.
1674 @cindex optimized code, debugging
1675 @cindex debugging optimized code
1676 When you debug a program compiled with @samp{-g -O}, remember that the
1677 optimizer is rearranging your code; the debugger shows you what is
1678 really there. Do not be too surprised when the execution path does not
1679 exactly match your source file! An extreme example: if you define a
1680 variable, but never use it, @value{GDBN} never sees that
1681 variable---because the compiler optimizes it out of existence.
1683 Some things do not work as well with @samp{-g -O} as with just
1684 @samp{-g}, particularly on machines with instruction scheduling. If in
1685 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1686 please report it to us as a bug (including a test case!).
1688 Older versions of the @sc{gnu} C compiler permitted a variant option
1689 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1690 format; if your @sc{gnu} C compiler has this option, do not use it.
1694 @section Starting your program
1700 @kindex r @r{(@code{run})}
1703 Use the @code{run} command to start your program under @value{GDBN}.
1704 You must first specify the program name (except on VxWorks) with an
1705 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1706 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1707 (@pxref{Files, ,Commands to specify files}).
1711 If you are running your program in an execution environment that
1712 supports processes, @code{run} creates an inferior process and makes
1713 that process run your program. (In environments without processes,
1714 @code{run} jumps to the start of your program.)
1716 The execution of a program is affected by certain information it
1717 receives from its superior. @value{GDBN} provides ways to specify this
1718 information, which you must do @emph{before} starting your program. (You
1719 can change it after starting your program, but such changes only affect
1720 your program the next time you start it.) This information may be
1721 divided into four categories:
1724 @item The @emph{arguments.}
1725 Specify the arguments to give your program as the arguments of the
1726 @code{run} command. If a shell is available on your target, the shell
1727 is used to pass the arguments, so that you may use normal conventions
1728 (such as wildcard expansion or variable substitution) in describing
1730 In Unix systems, you can control which shell is used with the
1731 @code{SHELL} environment variable.
1732 @xref{Arguments, ,Your program's arguments}.
1734 @item The @emph{environment.}
1735 Your program normally inherits its environment from @value{GDBN}, but you can
1736 use the @value{GDBN} commands @code{set environment} and @code{unset
1737 environment} to change parts of the environment that affect
1738 your program. @xref{Environment, ,Your program's environment}.
1740 @item The @emph{working directory.}
1741 Your program inherits its working directory from @value{GDBN}. You can set
1742 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1743 @xref{Working Directory, ,Your program's working directory}.
1745 @item The @emph{standard input and output.}
1746 Your program normally uses the same device for standard input and
1747 standard output as @value{GDBN} is using. You can redirect input and output
1748 in the @code{run} command line, or you can use the @code{tty} command to
1749 set a different device for your program.
1750 @xref{Input/Output, ,Your program's input and output}.
1753 @emph{Warning:} While input and output redirection work, you cannot use
1754 pipes to pass the output of the program you are debugging to another
1755 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1759 When you issue the @code{run} command, your program begins to execute
1760 immediately. @xref{Stopping, ,Stopping and continuing}, for discussion
1761 of how to arrange for your program to stop. Once your program has
1762 stopped, you may call functions in your program, using the @code{print}
1763 or @code{call} commands. @xref{Data, ,Examining Data}.
1765 If the modification time of your symbol file has changed since the last
1766 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1767 table, and reads it again. When it does this, @value{GDBN} tries to retain
1768 your current breakpoints.
1771 @section Your program's arguments
1773 @cindex arguments (to your program)
1774 The arguments to your program can be specified by the arguments of the
1776 They are passed to a shell, which expands wildcard characters and
1777 performs redirection of I/O, and thence to your program. Your
1778 @code{SHELL} environment variable (if it exists) specifies what shell
1779 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1780 the default shell (@file{/bin/sh} on Unix).
1782 On non-Unix systems, the program is usually invoked directly by
1783 @value{GDBN}, which emulates I/O redirection via the appropriate system
1784 calls, and the wildcard characters are expanded by the startup code of
1785 the program, not by the shell.
1787 @code{run} with no arguments uses the same arguments used by the previous
1788 @code{run}, or those set by the @code{set args} command.
1793 Specify the arguments to be used the next time your program is run. If
1794 @code{set args} has no arguments, @code{run} executes your program
1795 with no arguments. Once you have run your program with arguments,
1796 using @code{set args} before the next @code{run} is the only way to run
1797 it again without arguments.
1801 Show the arguments to give your program when it is started.
1805 @section Your program's environment
1807 @cindex environment (of your program)
1808 The @dfn{environment} consists of a set of environment variables and
1809 their values. Environment variables conventionally record such things as
1810 your user name, your home directory, your terminal type, and your search
1811 path for programs to run. Usually you set up environment variables with
1812 the shell and they are inherited by all the other programs you run. When
1813 debugging, it can be useful to try running your program with a modified
1814 environment without having to start @value{GDBN} over again.
1818 @item path @var{directory}
1819 Add @var{directory} to the front of the @code{PATH} environment variable
1820 (the search path for executables) that will be passed to your program.
1821 The value of @code{PATH} used by @value{GDBN} does not change.
1822 You may specify several directory names, separated by whitespace or by a
1823 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1824 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1825 is moved to the front, so it is searched sooner.
1827 You can use the string @samp{$cwd} to refer to whatever is the current
1828 working directory at the time @value{GDBN} searches the path. If you
1829 use @samp{.} instead, it refers to the directory where you executed the
1830 @code{path} command. @value{GDBN} replaces @samp{.} in the
1831 @var{directory} argument (with the current path) before adding
1832 @var{directory} to the search path.
1833 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1834 @c document that, since repeating it would be a no-op.
1838 Display the list of search paths for executables (the @code{PATH}
1839 environment variable).
1841 @kindex show environment
1842 @item show environment @r{[}@var{varname}@r{]}
1843 Print the value of environment variable @var{varname} to be given to
1844 your program when it starts. If you do not supply @var{varname},
1845 print the names and values of all environment variables to be given to
1846 your program. You can abbreviate @code{environment} as @code{env}.
1848 @kindex set environment
1849 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1850 Set environment variable @var{varname} to @var{value}. The value
1851 changes for your program only, not for @value{GDBN} itself. @var{value} may
1852 be any string; the values of environment variables are just strings, and
1853 any interpretation is supplied by your program itself. The @var{value}
1854 parameter is optional; if it is eliminated, the variable is set to a
1856 @c "any string" here does not include leading, trailing
1857 @c blanks. Gnu asks: does anyone care?
1859 For example, this command:
1866 tells the debugged program, when subsequently run, that its user is named
1867 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
1868 are not actually required.)
1870 @kindex unset environment
1871 @item unset environment @var{varname}
1872 Remove variable @var{varname} from the environment to be passed to your
1873 program. This is different from @samp{set env @var{varname} =};
1874 @code{unset environment} removes the variable from the environment,
1875 rather than assigning it an empty value.
1878 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
1880 by your @code{SHELL} environment variable if it exists (or
1881 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
1882 that runs an initialization file---such as @file{.cshrc} for C-shell, or
1883 @file{.bashrc} for BASH---any variables you set in that file affect
1884 your program. You may wish to move setting of environment variables to
1885 files that are only run when you sign on, such as @file{.login} or
1888 @node Working Directory
1889 @section Your program's working directory
1891 @cindex working directory (of your program)
1892 Each time you start your program with @code{run}, it inherits its
1893 working directory from the current working directory of @value{GDBN}.
1894 The @value{GDBN} working directory is initially whatever it inherited
1895 from its parent process (typically the shell), but you can specify a new
1896 working directory in @value{GDBN} with the @code{cd} command.
1898 The @value{GDBN} working directory also serves as a default for the commands
1899 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
1904 @item cd @var{directory}
1905 Set the @value{GDBN} working directory to @var{directory}.
1909 Print the @value{GDBN} working directory.
1913 @section Your program's input and output
1918 By default, the program you run under @value{GDBN} does input and output to
1919 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
1920 to its own terminal modes to interact with you, but it records the terminal
1921 modes your program was using and switches back to them when you continue
1922 running your program.
1925 @kindex info terminal
1927 Displays information recorded by @value{GDBN} about the terminal modes your
1931 You can redirect your program's input and/or output using shell
1932 redirection with the @code{run} command. For example,
1939 starts your program, diverting its output to the file @file{outfile}.
1942 @cindex controlling terminal
1943 Another way to specify where your program should do input and output is
1944 with the @code{tty} command. This command accepts a file name as
1945 argument, and causes this file to be the default for future @code{run}
1946 commands. It also resets the controlling terminal for the child
1947 process, for future @code{run} commands. For example,
1954 directs that processes started with subsequent @code{run} commands
1955 default to do input and output on the terminal @file{/dev/ttyb} and have
1956 that as their controlling terminal.
1958 An explicit redirection in @code{run} overrides the @code{tty} command's
1959 effect on the input/output device, but not its effect on the controlling
1962 When you use the @code{tty} command or redirect input in the @code{run}
1963 command, only the input @emph{for your program} is affected. The input
1964 for @value{GDBN} still comes from your terminal.
1967 @section Debugging an already-running process
1972 @item attach @var{process-id}
1973 This command attaches to a running process---one that was started
1974 outside @value{GDBN}. (@code{info files} shows your active
1975 targets.) The command takes as argument a process ID. The usual way to
1976 find out the process-id of a Unix process is with the @code{ps} utility,
1977 or with the @samp{jobs -l} shell command.
1979 @code{attach} does not repeat if you press @key{RET} a second time after
1980 executing the command.
1983 To use @code{attach}, your program must be running in an environment
1984 which supports processes; for example, @code{attach} does not work for
1985 programs on bare-board targets that lack an operating system. You must
1986 also have permission to send the process a signal.
1988 When you use @code{attach}, the debugger finds the program running in
1989 the process first by looking in the current working directory, then (if
1990 the program is not found) by using the source file search path
1991 (@pxref{Source Path, ,Specifying source directories}). You can also use
1992 the @code{file} command to load the program. @xref{Files, ,Commands to
1995 The first thing @value{GDBN} does after arranging to debug the specified
1996 process is to stop it. You can examine and modify an attached process
1997 with all the @value{GDBN} commands that are ordinarily available when
1998 you start processes with @code{run}. You can insert breakpoints; you
1999 can step and continue; you can modify storage. If you would rather the
2000 process continue running, you may use the @code{continue} command after
2001 attaching @value{GDBN} to the process.
2006 When you have finished debugging the attached process, you can use the
2007 @code{detach} command to release it from @value{GDBN} control. Detaching
2008 the process continues its execution. After the @code{detach} command,
2009 that process and @value{GDBN} become completely independent once more, and you
2010 are ready to @code{attach} another process or start one with @code{run}.
2011 @code{detach} does not repeat if you press @key{RET} again after
2012 executing the command.
2015 If you exit @value{GDBN} or use the @code{run} command while you have an
2016 attached process, you kill that process. By default, @value{GDBN} asks
2017 for confirmation if you try to do either of these things; you can
2018 control whether or not you need to confirm by using the @code{set
2019 confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
2023 @section Killing the child process
2028 Kill the child process in which your program is running under @value{GDBN}.
2031 This command is useful if you wish to debug a core dump instead of a
2032 running process. @value{GDBN} ignores any core dump file while your program
2035 On some operating systems, a program cannot be executed outside @value{GDBN}
2036 while you have breakpoints set on it inside @value{GDBN}. You can use the
2037 @code{kill} command in this situation to permit running your program
2038 outside the debugger.
2040 The @code{kill} command is also useful if you wish to recompile and
2041 relink your program, since on many systems it is impossible to modify an
2042 executable file while it is running in a process. In this case, when you
2043 next type @code{run}, @value{GDBN} notices that the file has changed, and
2044 reads the symbol table again (while trying to preserve your current
2045 breakpoint settings).
2048 @section Debugging programs with multiple threads
2050 @cindex threads of execution
2051 @cindex multiple threads
2052 @cindex switching threads
2053 In some operating systems, such as HP-UX and Solaris, a single program
2054 may have more than one @dfn{thread} of execution. The precise semantics
2055 of threads differ from one operating system to another, but in general
2056 the threads of a single program are akin to multiple processes---except
2057 that they share one address space (that is, they can all examine and
2058 modify the same variables). On the other hand, each thread has its own
2059 registers and execution stack, and perhaps private memory.
2061 @value{GDBN} provides these facilities for debugging multi-thread
2065 @item automatic notification of new threads
2066 @item @samp{thread @var{threadno}}, a command to switch among threads
2067 @item @samp{info threads}, a command to inquire about existing threads
2068 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2069 a command to apply a command to a list of threads
2070 @item thread-specific breakpoints
2074 @emph{Warning:} These facilities are not yet available on every
2075 @value{GDBN} configuration where the operating system supports threads.
2076 If your @value{GDBN} does not support threads, these commands have no
2077 effect. For example, a system without thread support shows no output
2078 from @samp{info threads}, and always rejects the @code{thread} command,
2082 (@value{GDBP}) info threads
2083 (@value{GDBP}) thread 1
2084 Thread ID 1 not known. Use the "info threads" command to
2085 see the IDs of currently known threads.
2087 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2088 @c doesn't support threads"?
2091 @cindex focus of debugging
2092 @cindex current thread
2093 The @value{GDBN} thread debugging facility allows you to observe all
2094 threads while your program runs---but whenever @value{GDBN} takes
2095 control, one thread in particular is always the focus of debugging.
2096 This thread is called the @dfn{current thread}. Debugging commands show
2097 program information from the perspective of the current thread.
2099 @cindex @code{New} @var{systag} message
2100 @cindex thread identifier (system)
2101 @c FIXME-implementors!! It would be more helpful if the [New...] message
2102 @c included GDB's numeric thread handle, so you could just go to that
2103 @c thread without first checking `info threads'.
2104 Whenever @value{GDBN} detects a new thread in your program, it displays
2105 the target system's identification for the thread with a message in the
2106 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2107 whose form varies depending on the particular system. For example, on
2108 LynxOS, you might see
2111 [New process 35 thread 27]
2115 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2116 the @var{systag} is simply something like @samp{process 368}, with no
2119 @c FIXME!! (1) Does the [New...] message appear even for the very first
2120 @c thread of a program, or does it only appear for the
2121 @c second---i.e.@: when it becomes obvious we have a multithread
2123 @c (2) *Is* there necessarily a first thread always? Or do some
2124 @c multithread systems permit starting a program with multiple
2125 @c threads ab initio?
2127 @cindex thread number
2128 @cindex thread identifier (GDB)
2129 For debugging purposes, @value{GDBN} associates its own thread
2130 number---always a single integer---with each thread in your program.
2133 @kindex info threads
2135 Display a summary of all threads currently in your
2136 program. @value{GDBN} displays for each thread (in this order):
2139 @item the thread number assigned by @value{GDBN}
2141 @item the target system's thread identifier (@var{systag})
2143 @item the current stack frame summary for that thread
2147 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2148 indicates the current thread.
2152 @c end table here to get a little more width for example
2155 (@value{GDBP}) info threads
2156 3 process 35 thread 27 0x34e5 in sigpause ()
2157 2 process 35 thread 23 0x34e5 in sigpause ()
2158 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2164 @cindex thread number
2165 @cindex thread identifier (GDB)
2166 For debugging purposes, @value{GDBN} associates its own thread
2167 number---a small integer assigned in thread-creation order---with each
2168 thread in your program.
2170 @cindex @code{New} @var{systag} message, on HP-UX
2171 @cindex thread identifier (system), on HP-UX
2172 @c FIXME-implementors!! It would be more helpful if the [New...] message
2173 @c included GDB's numeric thread handle, so you could just go to that
2174 @c thread without first checking `info threads'.
2175 Whenever @value{GDBN} detects a new thread in your program, it displays
2176 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2177 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2178 whose form varies depending on the particular system. For example, on
2182 [New thread 2 (system thread 26594)]
2186 when @value{GDBN} notices a new thread.
2189 @kindex info threads
2191 Display a summary of all threads currently in your
2192 program. @value{GDBN} displays for each thread (in this order):
2195 @item the thread number assigned by @value{GDBN}
2197 @item the target system's thread identifier (@var{systag})
2199 @item the current stack frame summary for that thread
2203 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2204 indicates the current thread.
2208 @c end table here to get a little more width for example
2211 (@value{GDBP}) info threads
2212 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2214 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2215 from /usr/lib/libc.2
2216 1 system thread 27905 0x7b003498 in _brk () \@*
2217 from /usr/lib/libc.2
2221 @kindex thread @var{threadno}
2222 @item thread @var{threadno}
2223 Make thread number @var{threadno} the current thread. The command
2224 argument @var{threadno} is the internal @value{GDBN} thread number, as
2225 shown in the first field of the @samp{info threads} display.
2226 @value{GDBN} responds by displaying the system identifier of the thread
2227 you selected, and its current stack frame summary:
2230 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2231 (@value{GDBP}) thread 2
2232 [Switching to process 35 thread 23]
2233 0x34e5 in sigpause ()
2237 As with the @samp{[New @dots{}]} message, the form of the text after
2238 @samp{Switching to} depends on your system's conventions for identifying
2241 @kindex thread apply
2242 @item thread apply [@var{threadno}] [@var{all}] @var{args}
2243 The @code{thread apply} command allows you to apply a command to one or
2244 more threads. Specify the numbers of the threads that you want affected
2245 with the command argument @var{threadno}. @var{threadno} is the internal
2246 @value{GDBN} thread number, as shown in the first field of the @samp{info
2247 threads} display. To apply a command to all threads, use
2248 @code{thread apply all} @var{args}.
2251 @cindex automatic thread selection
2252 @cindex switching threads automatically
2253 @cindex threads, automatic switching
2254 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2255 signal, it automatically selects the thread where that breakpoint or
2256 signal happened. @value{GDBN} alerts you to the context switch with a
2257 message of the form @samp{[Switching to @var{systag}]} to identify the
2260 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2261 more information about how @value{GDBN} behaves when you stop and start
2262 programs with multiple threads.
2264 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2265 watchpoints in programs with multiple threads.
2268 @section Debugging programs with multiple processes
2270 @cindex fork, debugging programs which call
2271 @cindex multiple processes
2272 @cindex processes, multiple
2273 On most systems, @value{GDBN} has no special support for debugging
2274 programs which create additional processes using the @code{fork}
2275 function. When a program forks, @value{GDBN} will continue to debug the
2276 parent process and the child process will run unimpeded. If you have
2277 set a breakpoint in any code which the child then executes, the child
2278 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2279 will cause it to terminate.
2281 However, if you want to debug the child process there is a workaround
2282 which isn't too painful. Put a call to @code{sleep} in the code which
2283 the child process executes after the fork. It may be useful to sleep
2284 only if a certain environment variable is set, or a certain file exists,
2285 so that the delay need not occur when you don't want to run @value{GDBN}
2286 on the child. While the child is sleeping, use the @code{ps} program to
2287 get its process ID. Then tell @value{GDBN} (a new invocation of
2288 @value{GDBN} if you are also debugging the parent process) to attach to
2289 the child process (@pxref{Attach}). From that point on you can debug
2290 the child process just like any other process which you attached to.
2292 On some systems, @value{GDBN} provides support for debugging programs that
2293 create additional processes using the @code{fork} or @code{vfork} functions.
2294 Currently, the only platforms with this feature are HP-UX (11.x and later
2295 only?) and GNU/Linux (kernel version 2.5.60 and later).
2297 By default, when a program forks, @value{GDBN} will continue to debug
2298 the parent process and the child process will run unimpeded.
2300 If you want to follow the child process instead of the parent process,
2301 use the command @w{@code{set follow-fork-mode}}.
2304 @kindex set follow-fork-mode
2305 @item set follow-fork-mode @var{mode}
2306 Set the debugger response to a program call of @code{fork} or
2307 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2308 process. The @var{mode} can be:
2312 The original process is debugged after a fork. The child process runs
2313 unimpeded. This is the default.
2316 The new process is debugged after a fork. The parent process runs
2321 @item show follow-fork-mode
2322 Display the current debugger response to a @code{fork} or @code{vfork} call.
2325 If you ask to debug a child process and a @code{vfork} is followed by an
2326 @code{exec}, @value{GDBN} executes the new target up to the first
2327 breakpoint in the new target. If you have a breakpoint set on
2328 @code{main} in your original program, the breakpoint will also be set on
2329 the child process's @code{main}.
2331 When a child process is spawned by @code{vfork}, you cannot debug the
2332 child or parent until an @code{exec} call completes.
2334 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2335 call executes, the new target restarts. To restart the parent process,
2336 use the @code{file} command with the parent executable name as its
2339 You can use the @code{catch} command to make @value{GDBN} stop whenever
2340 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2341 Catchpoints, ,Setting catchpoints}.
2344 @chapter Stopping and Continuing
2346 The principal purposes of using a debugger are so that you can stop your
2347 program before it terminates; or so that, if your program runs into
2348 trouble, you can investigate and find out why.
2350 Inside @value{GDBN}, your program may stop for any of several reasons,
2351 such as a signal, a breakpoint, or reaching a new line after a
2352 @value{GDBN} command such as @code{step}. You may then examine and
2353 change variables, set new breakpoints or remove old ones, and then
2354 continue execution. Usually, the messages shown by @value{GDBN} provide
2355 ample explanation of the status of your program---but you can also
2356 explicitly request this information at any time.
2359 @kindex info program
2361 Display information about the status of your program: whether it is
2362 running or not, what process it is, and why it stopped.
2366 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2367 * Continuing and Stepping:: Resuming execution
2369 * Thread Stops:: Stopping and starting multi-thread programs
2373 @section Breakpoints, watchpoints, and catchpoints
2376 A @dfn{breakpoint} makes your program stop whenever a certain point in
2377 the program is reached. For each breakpoint, you can add conditions to
2378 control in finer detail whether your program stops. You can set
2379 breakpoints with the @code{break} command and its variants (@pxref{Set
2380 Breaks, ,Setting breakpoints}), to specify the place where your program
2381 should stop by line number, function name or exact address in the
2384 In HP-UX, SunOS 4.x, SVR4, and Alpha OSF/1 configurations, you can set
2385 breakpoints in shared libraries before the executable is run. There is
2386 a minor limitation on HP-UX systems: you must wait until the executable
2387 is run in order to set breakpoints in shared library routines that are
2388 not called directly by the program (for example, routines that are
2389 arguments in a @code{pthread_create} call).
2392 @cindex memory tracing
2393 @cindex breakpoint on memory address
2394 @cindex breakpoint on variable modification
2395 A @dfn{watchpoint} is a special breakpoint that stops your program
2396 when the value of an expression changes. You must use a different
2397 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
2398 watchpoints}), but aside from that, you can manage a watchpoint like
2399 any other breakpoint: you enable, disable, and delete both breakpoints
2400 and watchpoints using the same commands.
2402 You can arrange to have values from your program displayed automatically
2403 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2407 @cindex breakpoint on events
2408 A @dfn{catchpoint} is another special breakpoint that stops your program
2409 when a certain kind of event occurs, such as the throwing of a C@t{++}
2410 exception or the loading of a library. As with watchpoints, you use a
2411 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2412 catchpoints}), but aside from that, you can manage a catchpoint like any
2413 other breakpoint. (To stop when your program receives a signal, use the
2414 @code{handle} command; see @ref{Signals, ,Signals}.)
2416 @cindex breakpoint numbers
2417 @cindex numbers for breakpoints
2418 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2419 catchpoint when you create it; these numbers are successive integers
2420 starting with one. In many of the commands for controlling various
2421 features of breakpoints you use the breakpoint number to say which
2422 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2423 @dfn{disabled}; if disabled, it has no effect on your program until you
2426 @cindex breakpoint ranges
2427 @cindex ranges of breakpoints
2428 Some @value{GDBN} commands accept a range of breakpoints on which to
2429 operate. A breakpoint range is either a single breakpoint number, like
2430 @samp{5}, or two such numbers, in increasing order, separated by a
2431 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2432 all breakpoint in that range are operated on.
2435 * Set Breaks:: Setting breakpoints
2436 * Set Watchpoints:: Setting watchpoints
2437 * Set Catchpoints:: Setting catchpoints
2438 * Delete Breaks:: Deleting breakpoints
2439 * Disabling:: Disabling breakpoints
2440 * Conditions:: Break conditions
2441 * Break Commands:: Breakpoint command lists
2442 * Breakpoint Menus:: Breakpoint menus
2443 * Error in Breakpoints:: ``Cannot insert breakpoints''
2444 * Breakpoint related warnings:: ``Breakpoint address adjusted...''
2448 @subsection Setting breakpoints
2450 @c FIXME LMB what does GDB do if no code on line of breakpt?
2451 @c consider in particular declaration with/without initialization.
2453 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2456 @kindex b @r{(@code{break})}
2457 @vindex $bpnum@r{, convenience variable}
2458 @cindex latest breakpoint
2459 Breakpoints are set with the @code{break} command (abbreviated
2460 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2461 number of the breakpoint you've set most recently; see @ref{Convenience
2462 Vars,, Convenience variables}, for a discussion of what you can do with
2463 convenience variables.
2465 You have several ways to say where the breakpoint should go.
2468 @item break @var{function}
2469 Set a breakpoint at entry to function @var{function}.
2470 When using source languages that permit overloading of symbols, such as
2471 C@t{++}, @var{function} may refer to more than one possible place to break.
2472 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2474 @item break +@var{offset}
2475 @itemx break -@var{offset}
2476 Set a breakpoint some number of lines forward or back from the position
2477 at which execution stopped in the currently selected @dfn{stack frame}.
2478 (@xref{Frames, ,Frames}, for a description of stack frames.)
2480 @item break @var{linenum}
2481 Set a breakpoint at line @var{linenum} in the current source file.
2482 The current source file is the last file whose source text was printed.
2483 The breakpoint will stop your program just before it executes any of the
2486 @item break @var{filename}:@var{linenum}
2487 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2489 @item break @var{filename}:@var{function}
2490 Set a breakpoint at entry to function @var{function} found in file
2491 @var{filename}. Specifying a file name as well as a function name is
2492 superfluous except when multiple files contain similarly named
2495 @item break *@var{address}
2496 Set a breakpoint at address @var{address}. You can use this to set
2497 breakpoints in parts of your program which do not have debugging
2498 information or source files.
2501 When called without any arguments, @code{break} sets a breakpoint at
2502 the next instruction to be executed in the selected stack frame
2503 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2504 innermost, this makes your program stop as soon as control
2505 returns to that frame. This is similar to the effect of a
2506 @code{finish} command in the frame inside the selected frame---except
2507 that @code{finish} does not leave an active breakpoint. If you use
2508 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2509 the next time it reaches the current location; this may be useful
2512 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2513 least one instruction has been executed. If it did not do this, you
2514 would be unable to proceed past a breakpoint without first disabling the
2515 breakpoint. This rule applies whether or not the breakpoint already
2516 existed when your program stopped.
2518 @item break @dots{} if @var{cond}
2519 Set a breakpoint with condition @var{cond}; evaluate the expression
2520 @var{cond} each time the breakpoint is reached, and stop only if the
2521 value is nonzero---that is, if @var{cond} evaluates as true.
2522 @samp{@dots{}} stands for one of the possible arguments described
2523 above (or no argument) specifying where to break. @xref{Conditions,
2524 ,Break conditions}, for more information on breakpoint conditions.
2527 @item tbreak @var{args}
2528 Set a breakpoint enabled only for one stop. @var{args} are the
2529 same as for the @code{break} command, and the breakpoint is set in the same
2530 way, but the breakpoint is automatically deleted after the first time your
2531 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2534 @item hbreak @var{args}
2535 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2536 @code{break} command and the breakpoint is set in the same way, but the
2537 breakpoint requires hardware support and some target hardware may not
2538 have this support. The main purpose of this is EPROM/ROM code
2539 debugging, so you can set a breakpoint at an instruction without
2540 changing the instruction. This can be used with the new trap-generation
2541 provided by SPARClite DSU and some x86-based targets. These targets
2542 will generate traps when a program accesses some data or instruction
2543 address that is assigned to the debug registers. However the hardware
2544 breakpoint registers can take a limited number of breakpoints. For
2545 example, on the DSU, only two data breakpoints can be set at a time, and
2546 @value{GDBN} will reject this command if more than two are used. Delete
2547 or disable unused hardware breakpoints before setting new ones
2548 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2549 @xref{set remote hardware-breakpoint-limit}.
2553 @item thbreak @var{args}
2554 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2555 are the same as for the @code{hbreak} command and the breakpoint is set in
2556 the same way. However, like the @code{tbreak} command,
2557 the breakpoint is automatically deleted after the
2558 first time your program stops there. Also, like the @code{hbreak}
2559 command, the breakpoint requires hardware support and some target hardware
2560 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2561 See also @ref{Conditions, ,Break conditions}.
2564 @cindex regular expression
2565 @item rbreak @var{regex}
2566 Set breakpoints on all functions matching the regular expression
2567 @var{regex}. This command sets an unconditional breakpoint on all
2568 matches, printing a list of all breakpoints it set. Once these
2569 breakpoints are set, they are treated just like the breakpoints set with
2570 the @code{break} command. You can delete them, disable them, or make
2571 them conditional the same way as any other breakpoint.
2573 The syntax of the regular expression is the standard one used with tools
2574 like @file{grep}. Note that this is different from the syntax used by
2575 shells, so for instance @code{foo*} matches all functions that include
2576 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2577 @code{.*} leading and trailing the regular expression you supply, so to
2578 match only functions that begin with @code{foo}, use @code{^foo}.
2580 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2581 breakpoints on overloaded functions that are not members of any special
2584 @kindex info breakpoints
2585 @cindex @code{$_} and @code{info breakpoints}
2586 @item info breakpoints @r{[}@var{n}@r{]}
2587 @itemx info break @r{[}@var{n}@r{]}
2588 @itemx info watchpoints @r{[}@var{n}@r{]}
2589 Print a table of all breakpoints, watchpoints, and catchpoints set and
2590 not deleted, with the following columns for each breakpoint:
2593 @item Breakpoint Numbers
2595 Breakpoint, watchpoint, or catchpoint.
2597 Whether the breakpoint is marked to be disabled or deleted when hit.
2598 @item Enabled or Disabled
2599 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2600 that are not enabled.
2602 Where the breakpoint is in your program, as a memory address. If the
2603 breakpoint is pending (see below for details) on a future load of a shared library, the address
2604 will be listed as @samp{<PENDING>}.
2606 Where the breakpoint is in the source for your program, as a file and
2607 line number. For a pending breakpoint, the original string passed to
2608 the breakpoint command will be listed as it cannot be resolved until
2609 the appropriate shared library is loaded in the future.
2613 If a breakpoint is conditional, @code{info break} shows the condition on
2614 the line following the affected breakpoint; breakpoint commands, if any,
2615 are listed after that. A pending breakpoint is allowed to have a condition
2616 specified for it. The condition is not parsed for validity until a shared
2617 library is loaded that allows the pending breakpoint to resolve to a
2621 @code{info break} with a breakpoint
2622 number @var{n} as argument lists only that breakpoint. The
2623 convenience variable @code{$_} and the default examining-address for
2624 the @code{x} command are set to the address of the last breakpoint
2625 listed (@pxref{Memory, ,Examining memory}).
2628 @code{info break} displays a count of the number of times the breakpoint
2629 has been hit. This is especially useful in conjunction with the
2630 @code{ignore} command. You can ignore a large number of breakpoint
2631 hits, look at the breakpoint info to see how many times the breakpoint
2632 was hit, and then run again, ignoring one less than that number. This
2633 will get you quickly to the last hit of that breakpoint.
2636 @value{GDBN} allows you to set any number of breakpoints at the same place in
2637 your program. There is nothing silly or meaningless about this. When
2638 the breakpoints are conditional, this is even useful
2639 (@pxref{Conditions, ,Break conditions}).
2641 @cindex pending breakpoints
2642 If a specified breakpoint location cannot be found, @value{GDBN} will
2644 as to whether to make the breakpoint pending on a future shared
2645 library load. This is useful for setting breakpoints at the start of your
2646 @value{GDBN} session for locations that you know will be dynamically loaded
2647 later by the program being debugged. When shared libraries are loaded,
2648 a check is made to see if the load resoloves any pending breakpoint locations.
2649 If a pending breakpoint location has been resolved,
2650 a real breakpoint is created and the original pending breakpoint is removed.
2652 @cindex operations allowed on pending breakpoints
2653 Normal breakpoint operations apply to pending breakpoints as well. You may
2654 specify a condition for a pending breakpoint and/or commands to run when the
2655 breakpoint is reached. You can also enable or disable
2656 the pending breakpoint. When you specify a condition for a pending breakpoint,
2657 the parsing of the condition will be deferred until the point where the
2658 pending breakpoint location is resolved. Disabling a pending breakpoint
2659 tells @value{GDBN} to not attempt to resolve the breakpoint on any subsequent
2660 shared library load. When a pending breakpoint is re-enabled,
2661 @value{GDBN} checks to see if the location is already resolved.
2662 This is done because any number of shared library loads could have
2663 occurred since the time the breakpoint was disabled and one or more
2664 of these loads could resolve the location.
2666 @cindex negative breakpoint numbers
2667 @cindex internal @value{GDBN} breakpoints
2668 @value{GDBN} itself sometimes sets breakpoints in your program for
2669 special purposes, such as proper handling of @code{longjmp} (in C
2670 programs). These internal breakpoints are assigned negative numbers,
2671 starting with @code{-1}; @samp{info breakpoints} does not display them.
2672 You can see these breakpoints with the @value{GDBN} maintenance command
2673 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
2676 @node Set Watchpoints
2677 @subsection Setting watchpoints
2679 @cindex setting watchpoints
2680 @cindex software watchpoints
2681 @cindex hardware watchpoints
2682 You can use a watchpoint to stop execution whenever the value of an
2683 expression changes, without having to predict a particular place where
2686 Depending on your system, watchpoints may be implemented in software or
2687 hardware. @value{GDBN} does software watchpointing by single-stepping your
2688 program and testing the variable's value each time, which is hundreds of
2689 times slower than normal execution. (But this may still be worth it, to
2690 catch errors where you have no clue what part of your program is the
2693 On some systems, such as HP-UX, @sc{gnu}/Linux and some other x86-based targets,
2694 @value{GDBN} includes support for
2695 hardware watchpoints, which do not slow down the running of your
2700 @item watch @var{expr}
2701 Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
2702 is written into by the program and its value changes.
2705 @item rwatch @var{expr}
2706 Set a watchpoint that will break when watch @var{expr} is read by the program.
2709 @item awatch @var{expr}
2710 Set a watchpoint that will break when @var{expr} is either read or written into
2713 @kindex info watchpoints
2714 @item info watchpoints
2715 This command prints a list of watchpoints, breakpoints, and catchpoints;
2716 it is the same as @code{info break}.
2719 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
2720 watchpoints execute very quickly, and the debugger reports a change in
2721 value at the exact instruction where the change occurs. If @value{GDBN}
2722 cannot set a hardware watchpoint, it sets a software watchpoint, which
2723 executes more slowly and reports the change in value at the next
2724 statement, not the instruction, after the change occurs.
2726 When you issue the @code{watch} command, @value{GDBN} reports
2729 Hardware watchpoint @var{num}: @var{expr}
2733 if it was able to set a hardware watchpoint.
2735 Currently, the @code{awatch} and @code{rwatch} commands can only set
2736 hardware watchpoints, because accesses to data that don't change the
2737 value of the watched expression cannot be detected without examining
2738 every instruction as it is being executed, and @value{GDBN} does not do
2739 that currently. If @value{GDBN} finds that it is unable to set a
2740 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
2741 will print a message like this:
2744 Expression cannot be implemented with read/access watchpoint.
2747 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
2748 data type of the watched expression is wider than what a hardware
2749 watchpoint on the target machine can handle. For example, some systems
2750 can only watch regions that are up to 4 bytes wide; on such systems you
2751 cannot set hardware watchpoints for an expression that yields a
2752 double-precision floating-point number (which is typically 8 bytes
2753 wide). As a work-around, it might be possible to break the large region
2754 into a series of smaller ones and watch them with separate watchpoints.
2756 If you set too many hardware watchpoints, @value{GDBN} might be unable
2757 to insert all of them when you resume the execution of your program.
2758 Since the precise number of active watchpoints is unknown until such
2759 time as the program is about to be resumed, @value{GDBN} might not be
2760 able to warn you about this when you set the watchpoints, and the
2761 warning will be printed only when the program is resumed:
2764 Hardware watchpoint @var{num}: Could not insert watchpoint
2768 If this happens, delete or disable some of the watchpoints.
2770 The SPARClite DSU will generate traps when a program accesses some data
2771 or instruction address that is assigned to the debug registers. For the
2772 data addresses, DSU facilitates the @code{watch} command. However the
2773 hardware breakpoint registers can only take two data watchpoints, and
2774 both watchpoints must be the same kind. For example, you can set two
2775 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
2776 @strong{or} two with @code{awatch} commands, but you cannot set one
2777 watchpoint with one command and the other with a different command.
2778 @value{GDBN} will reject the command if you try to mix watchpoints.
2779 Delete or disable unused watchpoint commands before setting new ones.
2781 If you call a function interactively using @code{print} or @code{call},
2782 any watchpoints you have set will be inactive until @value{GDBN} reaches another
2783 kind of breakpoint or the call completes.
2785 @value{GDBN} automatically deletes watchpoints that watch local
2786 (automatic) variables, or expressions that involve such variables, when
2787 they go out of scope, that is, when the execution leaves the block in
2788 which these variables were defined. In particular, when the program
2789 being debugged terminates, @emph{all} local variables go out of scope,
2790 and so only watchpoints that watch global variables remain set. If you
2791 rerun the program, you will need to set all such watchpoints again. One
2792 way of doing that would be to set a code breakpoint at the entry to the
2793 @code{main} function and when it breaks, set all the watchpoints.
2796 @cindex watchpoints and threads
2797 @cindex threads and watchpoints
2798 @emph{Warning:} In multi-thread programs, watchpoints have only limited
2799 usefulness. With the current watchpoint implementation, @value{GDBN}
2800 can only watch the value of an expression @emph{in a single thread}. If
2801 you are confident that the expression can only change due to the current
2802 thread's activity (and if you are also confident that no other thread
2803 can become current), then you can use watchpoints as usual. However,
2804 @value{GDBN} may not notice when a non-current thread's activity changes
2807 @c FIXME: this is almost identical to the previous paragraph.
2808 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
2809 have only limited usefulness. If @value{GDBN} creates a software
2810 watchpoint, it can only watch the value of an expression @emph{in a
2811 single thread}. If you are confident that the expression can only
2812 change due to the current thread's activity (and if you are also
2813 confident that no other thread can become current), then you can use
2814 software watchpoints as usual. However, @value{GDBN} may not notice
2815 when a non-current thread's activity changes the expression. (Hardware
2816 watchpoints, in contrast, watch an expression in all threads.)
2819 @xref{set remote hardware-watchpoint-limit}.
2821 @node Set Catchpoints
2822 @subsection Setting catchpoints
2823 @cindex catchpoints, setting
2824 @cindex exception handlers
2825 @cindex event handling
2827 You can use @dfn{catchpoints} to cause the debugger to stop for certain
2828 kinds of program events, such as C@t{++} exceptions or the loading of a
2829 shared library. Use the @code{catch} command to set a catchpoint.
2833 @item catch @var{event}
2834 Stop when @var{event} occurs. @var{event} can be any of the following:
2838 The throwing of a C@t{++} exception.
2842 The catching of a C@t{++} exception.
2846 A call to @code{exec}. This is currently only available for HP-UX.
2850 A call to @code{fork}. This is currently only available for HP-UX.
2854 A call to @code{vfork}. This is currently only available for HP-UX.
2857 @itemx load @var{libname}
2859 The dynamic loading of any shared library, or the loading of the library
2860 @var{libname}. This is currently only available for HP-UX.
2863 @itemx unload @var{libname}
2864 @kindex catch unload
2865 The unloading of any dynamically loaded shared library, or the unloading
2866 of the library @var{libname}. This is currently only available for HP-UX.
2869 @item tcatch @var{event}
2870 Set a catchpoint that is enabled only for one stop. The catchpoint is
2871 automatically deleted after the first time the event is caught.
2875 Use the @code{info break} command to list the current catchpoints.
2877 There are currently some limitations to C@t{++} exception handling
2878 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
2882 If you call a function interactively, @value{GDBN} normally returns
2883 control to you when the function has finished executing. If the call
2884 raises an exception, however, the call may bypass the mechanism that
2885 returns control to you and cause your program either to abort or to
2886 simply continue running until it hits a breakpoint, catches a signal
2887 that @value{GDBN} is listening for, or exits. This is the case even if
2888 you set a catchpoint for the exception; catchpoints on exceptions are
2889 disabled within interactive calls.
2892 You cannot raise an exception interactively.
2895 You cannot install an exception handler interactively.
2898 @cindex raise exceptions
2899 Sometimes @code{catch} is not the best way to debug exception handling:
2900 if you need to know exactly where an exception is raised, it is better to
2901 stop @emph{before} the exception handler is called, since that way you
2902 can see the stack before any unwinding takes place. If you set a
2903 breakpoint in an exception handler instead, it may not be easy to find
2904 out where the exception was raised.
2906 To stop just before an exception handler is called, you need some
2907 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
2908 raised by calling a library function named @code{__raise_exception}
2909 which has the following ANSI C interface:
2912 /* @var{addr} is where the exception identifier is stored.
2913 @var{id} is the exception identifier. */
2914 void __raise_exception (void **addr, void *id);
2918 To make the debugger catch all exceptions before any stack
2919 unwinding takes place, set a breakpoint on @code{__raise_exception}
2920 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
2922 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
2923 that depends on the value of @var{id}, you can stop your program when
2924 a specific exception is raised. You can use multiple conditional
2925 breakpoints to stop your program when any of a number of exceptions are
2930 @subsection Deleting breakpoints
2932 @cindex clearing breakpoints, watchpoints, catchpoints
2933 @cindex deleting breakpoints, watchpoints, catchpoints
2934 It is often necessary to eliminate a breakpoint, watchpoint, or
2935 catchpoint once it has done its job and you no longer want your program
2936 to stop there. This is called @dfn{deleting} the breakpoint. A
2937 breakpoint that has been deleted no longer exists; it is forgotten.
2939 With the @code{clear} command you can delete breakpoints according to
2940 where they are in your program. With the @code{delete} command you can
2941 delete individual breakpoints, watchpoints, or catchpoints by specifying
2942 their breakpoint numbers.
2944 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
2945 automatically ignores breakpoints on the first instruction to be executed
2946 when you continue execution without changing the execution address.
2951 Delete any breakpoints at the next instruction to be executed in the
2952 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
2953 the innermost frame is selected, this is a good way to delete a
2954 breakpoint where your program just stopped.
2956 @item clear @var{function}
2957 @itemx clear @var{filename}:@var{function}
2958 Delete any breakpoints set at entry to the function @var{function}.
2960 @item clear @var{linenum}
2961 @itemx clear @var{filename}:@var{linenum}
2962 Delete any breakpoints set at or within the code of the specified line.
2964 @cindex delete breakpoints
2966 @kindex d @r{(@code{delete})}
2967 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
2968 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
2969 ranges specified as arguments. If no argument is specified, delete all
2970 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
2971 confirm off}). You can abbreviate this command as @code{d}.
2975 @subsection Disabling breakpoints
2977 @kindex disable breakpoints
2978 @kindex enable breakpoints
2979 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
2980 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
2981 it had been deleted, but remembers the information on the breakpoint so
2982 that you can @dfn{enable} it again later.
2984 You disable and enable breakpoints, watchpoints, and catchpoints with
2985 the @code{enable} and @code{disable} commands, optionally specifying one
2986 or more breakpoint numbers as arguments. Use @code{info break} or
2987 @code{info watch} to print a list of breakpoints, watchpoints, and
2988 catchpoints if you do not know which numbers to use.
2990 A breakpoint, watchpoint, or catchpoint can have any of four different
2991 states of enablement:
2995 Enabled. The breakpoint stops your program. A breakpoint set
2996 with the @code{break} command starts out in this state.
2998 Disabled. The breakpoint has no effect on your program.
3000 Enabled once. The breakpoint stops your program, but then becomes
3003 Enabled for deletion. The breakpoint stops your program, but
3004 immediately after it does so it is deleted permanently. A breakpoint
3005 set with the @code{tbreak} command starts out in this state.
3008 You can use the following commands to enable or disable breakpoints,
3009 watchpoints, and catchpoints:
3012 @kindex disable breakpoints
3014 @kindex dis @r{(@code{disable})}
3015 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3016 Disable the specified breakpoints---or all breakpoints, if none are
3017 listed. A disabled breakpoint has no effect but is not forgotten. All
3018 options such as ignore-counts, conditions and commands are remembered in
3019 case the breakpoint is enabled again later. You may abbreviate
3020 @code{disable} as @code{dis}.
3022 @kindex enable breakpoints
3024 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3025 Enable the specified breakpoints (or all defined breakpoints). They
3026 become effective once again in stopping your program.
3028 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3029 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3030 of these breakpoints immediately after stopping your program.
3032 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3033 Enable the specified breakpoints to work once, then die. @value{GDBN}
3034 deletes any of these breakpoints as soon as your program stops there.
3037 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3038 @c confusing: tbreak is also initially enabled.
3039 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3040 ,Setting breakpoints}), breakpoints that you set are initially enabled;
3041 subsequently, they become disabled or enabled only when you use one of
3042 the commands above. (The command @code{until} can set and delete a
3043 breakpoint of its own, but it does not change the state of your other
3044 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3048 @subsection Break conditions
3049 @cindex conditional breakpoints
3050 @cindex breakpoint conditions
3052 @c FIXME what is scope of break condition expr? Context where wanted?
3053 @c in particular for a watchpoint?
3054 The simplest sort of breakpoint breaks every time your program reaches a
3055 specified place. You can also specify a @dfn{condition} for a
3056 breakpoint. A condition is just a Boolean expression in your
3057 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3058 a condition evaluates the expression each time your program reaches it,
3059 and your program stops only if the condition is @emph{true}.
3061 This is the converse of using assertions for program validation; in that
3062 situation, you want to stop when the assertion is violated---that is,
3063 when the condition is false. In C, if you want to test an assertion expressed
3064 by the condition @var{assert}, you should set the condition
3065 @samp{! @var{assert}} on the appropriate breakpoint.
3067 Conditions are also accepted for watchpoints; you may not need them,
3068 since a watchpoint is inspecting the value of an expression anyhow---but
3069 it might be simpler, say, to just set a watchpoint on a variable name,
3070 and specify a condition that tests whether the new value is an interesting
3073 Break conditions can have side effects, and may even call functions in
3074 your program. This can be useful, for example, to activate functions
3075 that log program progress, or to use your own print functions to
3076 format special data structures. The effects are completely predictable
3077 unless there is another enabled breakpoint at the same address. (In
3078 that case, @value{GDBN} might see the other breakpoint first and stop your
3079 program without checking the condition of this one.) Note that
3080 breakpoint commands are usually more convenient and flexible than break
3082 purpose of performing side effects when a breakpoint is reached
3083 (@pxref{Break Commands, ,Breakpoint command lists}).
3085 Break conditions can be specified when a breakpoint is set, by using
3086 @samp{if} in the arguments to the @code{break} command. @xref{Set
3087 Breaks, ,Setting breakpoints}. They can also be changed at any time
3088 with the @code{condition} command.
3090 You can also use the @code{if} keyword with the @code{watch} command.
3091 The @code{catch} command does not recognize the @code{if} keyword;
3092 @code{condition} is the only way to impose a further condition on a
3097 @item condition @var{bnum} @var{expression}
3098 Specify @var{expression} as the break condition for breakpoint,
3099 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3100 breakpoint @var{bnum} stops your program only if the value of
3101 @var{expression} is true (nonzero, in C). When you use
3102 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3103 syntactic correctness, and to determine whether symbols in it have
3104 referents in the context of your breakpoint. If @var{expression} uses
3105 symbols not referenced in the context of the breakpoint, @value{GDBN}
3106 prints an error message:
3109 No symbol "foo" in current context.
3114 not actually evaluate @var{expression} at the time the @code{condition}
3115 command (or a command that sets a breakpoint with a condition, like
3116 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3118 @item condition @var{bnum}
3119 Remove the condition from breakpoint number @var{bnum}. It becomes
3120 an ordinary unconditional breakpoint.
3123 @cindex ignore count (of breakpoint)
3124 A special case of a breakpoint condition is to stop only when the
3125 breakpoint has been reached a certain number of times. This is so
3126 useful that there is a special way to do it, using the @dfn{ignore
3127 count} of the breakpoint. Every breakpoint has an ignore count, which
3128 is an integer. Most of the time, the ignore count is zero, and
3129 therefore has no effect. But if your program reaches a breakpoint whose
3130 ignore count is positive, then instead of stopping, it just decrements
3131 the ignore count by one and continues. As a result, if the ignore count
3132 value is @var{n}, the breakpoint does not stop the next @var{n} times
3133 your program reaches it.
3137 @item ignore @var{bnum} @var{count}
3138 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3139 The next @var{count} times the breakpoint is reached, your program's
3140 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3143 To make the breakpoint stop the next time it is reached, specify
3146 When you use @code{continue} to resume execution of your program from a
3147 breakpoint, you can specify an ignore count directly as an argument to
3148 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3149 Stepping,,Continuing and stepping}.
3151 If a breakpoint has a positive ignore count and a condition, the
3152 condition is not checked. Once the ignore count reaches zero,
3153 @value{GDBN} resumes checking the condition.
3155 You could achieve the effect of the ignore count with a condition such
3156 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3157 is decremented each time. @xref{Convenience Vars, ,Convenience
3161 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3164 @node Break Commands
3165 @subsection Breakpoint command lists
3167 @cindex breakpoint commands
3168 You can give any breakpoint (or watchpoint or catchpoint) a series of
3169 commands to execute when your program stops due to that breakpoint. For
3170 example, you might want to print the values of certain expressions, or
3171 enable other breakpoints.
3176 @item commands @r{[}@var{bnum}@r{]}
3177 @itemx @dots{} @var{command-list} @dots{}
3179 Specify a list of commands for breakpoint number @var{bnum}. The commands
3180 themselves appear on the following lines. Type a line containing just
3181 @code{end} to terminate the commands.
3183 To remove all commands from a breakpoint, type @code{commands} and
3184 follow it immediately with @code{end}; that is, give no commands.
3186 With no @var{bnum} argument, @code{commands} refers to the last
3187 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3188 recently encountered).
3191 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3192 disabled within a @var{command-list}.
3194 You can use breakpoint commands to start your program up again. Simply
3195 use the @code{continue} command, or @code{step}, or any other command
3196 that resumes execution.
3198 Any other commands in the command list, after a command that resumes
3199 execution, are ignored. This is because any time you resume execution
3200 (even with a simple @code{next} or @code{step}), you may encounter
3201 another breakpoint---which could have its own command list, leading to
3202 ambiguities about which list to execute.
3205 If the first command you specify in a command list is @code{silent}, the
3206 usual message about stopping at a breakpoint is not printed. This may
3207 be desirable for breakpoints that are to print a specific message and
3208 then continue. If none of the remaining commands print anything, you
3209 see no sign that the breakpoint was reached. @code{silent} is
3210 meaningful only at the beginning of a breakpoint command list.
3212 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3213 print precisely controlled output, and are often useful in silent
3214 breakpoints. @xref{Output, ,Commands for controlled output}.
3216 For example, here is how you could use breakpoint commands to print the
3217 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3223 printf "x is %d\n",x
3228 One application for breakpoint commands is to compensate for one bug so
3229 you can test for another. Put a breakpoint just after the erroneous line
3230 of code, give it a condition to detect the case in which something
3231 erroneous has been done, and give it commands to assign correct values
3232 to any variables that need them. End with the @code{continue} command
3233 so that your program does not stop, and start with the @code{silent}
3234 command so that no output is produced. Here is an example:
3245 @node Breakpoint Menus
3246 @subsection Breakpoint menus
3248 @cindex symbol overloading
3250 Some programming languages (notably C@t{++} and Objective-C) permit a
3251 single function name
3252 to be defined several times, for application in different contexts.
3253 This is called @dfn{overloading}. When a function name is overloaded,
3254 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3255 a breakpoint. If you realize this is a problem, you can use
3256 something like @samp{break @var{function}(@var{types})} to specify which
3257 particular version of the function you want. Otherwise, @value{GDBN} offers
3258 you a menu of numbered choices for different possible breakpoints, and
3259 waits for your selection with the prompt @samp{>}. The first two
3260 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3261 sets a breakpoint at each definition of @var{function}, and typing
3262 @kbd{0} aborts the @code{break} command without setting any new
3265 For example, the following session excerpt shows an attempt to set a
3266 breakpoint at the overloaded symbol @code{String::after}.
3267 We choose three particular definitions of that function name:
3269 @c FIXME! This is likely to change to show arg type lists, at least
3272 (@value{GDBP}) b String::after
3275 [2] file:String.cc; line number:867
3276 [3] file:String.cc; line number:860
3277 [4] file:String.cc; line number:875
3278 [5] file:String.cc; line number:853
3279 [6] file:String.cc; line number:846
3280 [7] file:String.cc; line number:735
3282 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3283 Breakpoint 2 at 0xb344: file String.cc, line 875.
3284 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3285 Multiple breakpoints were set.
3286 Use the "delete" command to delete unwanted
3292 @c @ifclear BARETARGET
3293 @node Error in Breakpoints
3294 @subsection ``Cannot insert breakpoints''
3296 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3298 Under some operating systems, breakpoints cannot be used in a program if
3299 any other process is running that program. In this situation,
3300 attempting to run or continue a program with a breakpoint causes
3301 @value{GDBN} to print an error message:
3304 Cannot insert breakpoints.
3305 The same program may be running in another process.
3308 When this happens, you have three ways to proceed:
3312 Remove or disable the breakpoints, then continue.
3315 Suspend @value{GDBN}, and copy the file containing your program to a new
3316 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3317 that @value{GDBN} should run your program under that name.
3318 Then start your program again.
3321 Relink your program so that the text segment is nonsharable, using the
3322 linker option @samp{-N}. The operating system limitation may not apply
3323 to nonsharable executables.
3327 A similar message can be printed if you request too many active
3328 hardware-assisted breakpoints and watchpoints:
3330 @c FIXME: the precise wording of this message may change; the relevant
3331 @c source change is not committed yet (Sep 3, 1999).
3333 Stopped; cannot insert breakpoints.
3334 You may have requested too many hardware breakpoints and watchpoints.
3338 This message is printed when you attempt to resume the program, since
3339 only then @value{GDBN} knows exactly how many hardware breakpoints and
3340 watchpoints it needs to insert.
3342 When this message is printed, you need to disable or remove some of the
3343 hardware-assisted breakpoints and watchpoints, and then continue.
3345 @node Breakpoint related warnings
3346 @subsection ``Breakpoint address adjusted...''
3347 @cindex breakpoint address adjusted
3349 Some processor architectures place constraints on the addresses at
3350 which breakpoints may be placed. For architectures thus constrained,
3351 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3352 with the constraints dictated by the architecture.
3354 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3355 a VLIW architecture in which a number of RISC-like instructions may be
3356 bundled together for parallel execution. The FR-V architecture
3357 constrains the location of a breakpoint instruction within such a
3358 bundle to the instruction with the lowest address. @value{GDBN}
3359 honors this constraint by adjusting a breakpoint's address to the
3360 first in the bundle.
3362 It is not uncommon for optimized code to have bundles which contain
3363 instructions from different source statements, thus it may happen that
3364 a breakpoint's address will be adjusted from one source statement to
3365 another. Since this adjustment may significantly alter @value{GDBN}'s
3366 breakpoint related behavior from what the user expects, a warning is
3367 printed when the breakpoint is first set and also when the breakpoint
3370 A warning like the one below is printed when setting a breakpoint
3371 that's been subject to address adjustment:
3374 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3377 Such warnings are printed both for user settable and @value{GDBN}'s
3378 internal breakpoints. If you see one of these warnings, you should
3379 verify that a breakpoint set at the adjusted address will have the
3380 desired affect. If not, the breakpoint in question may be removed and
3381 other breakpoints may be set which will have the desired behavior.
3382 E.g., it may be sufficient to place the breakpoint at a later
3383 instruction. A conditional breakpoint may also be useful in some
3384 cases to prevent the breakpoint from triggering too often.
3386 @value{GDBN} will also issue a warning when stopping at one of these
3387 adjusted breakpoints:
3390 warning: Breakpoint 1 address previously adjusted from 0x00010414
3394 When this warning is encountered, it may be too late to take remedial
3395 action except in cases where the breakpoint is hit earlier or more
3396 frequently than expected.
3398 @node Continuing and Stepping
3399 @section Continuing and stepping
3403 @cindex resuming execution
3404 @dfn{Continuing} means resuming program execution until your program
3405 completes normally. In contrast, @dfn{stepping} means executing just
3406 one more ``step'' of your program, where ``step'' may mean either one
3407 line of source code, or one machine instruction (depending on what
3408 particular command you use). Either when continuing or when stepping,
3409 your program may stop even sooner, due to a breakpoint or a signal. (If
3410 it stops due to a signal, you may want to use @code{handle}, or use
3411 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3415 @kindex c @r{(@code{continue})}
3416 @kindex fg @r{(resume foreground execution)}
3417 @item continue @r{[}@var{ignore-count}@r{]}
3418 @itemx c @r{[}@var{ignore-count}@r{]}
3419 @itemx fg @r{[}@var{ignore-count}@r{]}
3420 Resume program execution, at the address where your program last stopped;
3421 any breakpoints set at that address are bypassed. The optional argument
3422 @var{ignore-count} allows you to specify a further number of times to
3423 ignore a breakpoint at this location; its effect is like that of
3424 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3426 The argument @var{ignore-count} is meaningful only when your program
3427 stopped due to a breakpoint. At other times, the argument to
3428 @code{continue} is ignored.
3430 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3431 debugged program is deemed to be the foreground program) are provided
3432 purely for convenience, and have exactly the same behavior as
3436 To resume execution at a different place, you can use @code{return}
3437 (@pxref{Returning, ,Returning from a function}) to go back to the
3438 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3439 different address}) to go to an arbitrary location in your program.
3441 A typical technique for using stepping is to set a breakpoint
3442 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3443 beginning of the function or the section of your program where a problem
3444 is believed to lie, run your program until it stops at that breakpoint,
3445 and then step through the suspect area, examining the variables that are
3446 interesting, until you see the problem happen.
3450 @kindex s @r{(@code{step})}
3452 Continue running your program until control reaches a different source
3453 line, then stop it and return control to @value{GDBN}. This command is
3454 abbreviated @code{s}.
3457 @c "without debugging information" is imprecise; actually "without line
3458 @c numbers in the debugging information". (gcc -g1 has debugging info but
3459 @c not line numbers). But it seems complex to try to make that
3460 @c distinction here.
3461 @emph{Warning:} If you use the @code{step} command while control is
3462 within a function that was compiled without debugging information,
3463 execution proceeds until control reaches a function that does have
3464 debugging information. Likewise, it will not step into a function which
3465 is compiled without debugging information. To step through functions
3466 without debugging information, use the @code{stepi} command, described
3470 The @code{step} command only stops at the first instruction of a source
3471 line. This prevents the multiple stops that could otherwise occur in
3472 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3473 to stop if a function that has debugging information is called within
3474 the line. In other words, @code{step} @emph{steps inside} any functions
3475 called within the line.
3477 Also, the @code{step} command only enters a function if there is line
3478 number information for the function. Otherwise it acts like the
3479 @code{next} command. This avoids problems when using @code{cc -gl}
3480 on MIPS machines. Previously, @code{step} entered subroutines if there
3481 was any debugging information about the routine.
3483 @item step @var{count}
3484 Continue running as in @code{step}, but do so @var{count} times. If a
3485 breakpoint is reached, or a signal not related to stepping occurs before
3486 @var{count} steps, stepping stops right away.
3489 @kindex n @r{(@code{next})}
3490 @item next @r{[}@var{count}@r{]}
3491 Continue to the next source line in the current (innermost) stack frame.
3492 This is similar to @code{step}, but function calls that appear within
3493 the line of code are executed without stopping. Execution stops when
3494 control reaches a different line of code at the original stack level
3495 that was executing when you gave the @code{next} command. This command
3496 is abbreviated @code{n}.
3498 An argument @var{count} is a repeat count, as for @code{step}.
3501 @c FIX ME!! Do we delete this, or is there a way it fits in with
3502 @c the following paragraph? --- Vctoria
3504 @c @code{next} within a function that lacks debugging information acts like
3505 @c @code{step}, but any function calls appearing within the code of the
3506 @c function are executed without stopping.
3508 The @code{next} command only stops at the first instruction of a
3509 source line. This prevents multiple stops that could otherwise occur in
3510 @code{switch} statements, @code{for} loops, etc.
3512 @kindex set step-mode
3514 @cindex functions without line info, and stepping
3515 @cindex stepping into functions with no line info
3516 @itemx set step-mode on
3517 The @code{set step-mode on} command causes the @code{step} command to
3518 stop at the first instruction of a function which contains no debug line
3519 information rather than stepping over it.
3521 This is useful in cases where you may be interested in inspecting the
3522 machine instructions of a function which has no symbolic info and do not
3523 want @value{GDBN} to automatically skip over this function.
3525 @item set step-mode off
3526 Causes the @code{step} command to step over any functions which contains no
3527 debug information. This is the default.
3531 Continue running until just after function in the selected stack frame
3532 returns. Print the returned value (if any).
3534 Contrast this with the @code{return} command (@pxref{Returning,
3535 ,Returning from a function}).
3538 @kindex u @r{(@code{until})}
3541 Continue running until a source line past the current line, in the
3542 current stack frame, is reached. This command is used to avoid single
3543 stepping through a loop more than once. It is like the @code{next}
3544 command, except that when @code{until} encounters a jump, it
3545 automatically continues execution until the program counter is greater
3546 than the address of the jump.
3548 This means that when you reach the end of a loop after single stepping
3549 though it, @code{until} makes your program continue execution until it
3550 exits the loop. In contrast, a @code{next} command at the end of a loop
3551 simply steps back to the beginning of the loop, which forces you to step
3552 through the next iteration.
3554 @code{until} always stops your program if it attempts to exit the current
3557 @code{until} may produce somewhat counterintuitive results if the order
3558 of machine code does not match the order of the source lines. For
3559 example, in the following excerpt from a debugging session, the @code{f}
3560 (@code{frame}) command shows that execution is stopped at line
3561 @code{206}; yet when we use @code{until}, we get to line @code{195}:
3565 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
3567 (@value{GDBP}) until
3568 195 for ( ; argc > 0; NEXTARG) @{
3571 This happened because, for execution efficiency, the compiler had
3572 generated code for the loop closure test at the end, rather than the
3573 start, of the loop---even though the test in a C @code{for}-loop is
3574 written before the body of the loop. The @code{until} command appeared
3575 to step back to the beginning of the loop when it advanced to this
3576 expression; however, it has not really gone to an earlier
3577 statement---not in terms of the actual machine code.
3579 @code{until} with no argument works by means of single
3580 instruction stepping, and hence is slower than @code{until} with an
3583 @item until @var{location}
3584 @itemx u @var{location}
3585 Continue running your program until either the specified location is
3586 reached, or the current stack frame returns. @var{location} is any of
3587 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
3588 ,Setting breakpoints}). This form of the command uses breakpoints, and
3589 hence is quicker than @code{until} without an argument. The specified
3590 location is actually reached only if it is in the current frame. This
3591 implies that @code{until} can be used to skip over recursive function
3592 invocations. For instance in the code below, if the current location is
3593 line @code{96}, issuing @code{until 99} will execute the program up to
3594 line @code{99} in the same invocation of factorial, i.e. after the inner
3595 invocations have returned.
3598 94 int factorial (int value)
3600 96 if (value > 1) @{
3601 97 value *= factorial (value - 1);
3608 @kindex advance @var{location}
3609 @itemx advance @var{location}
3610 Continue running the program up to the given location. An argument is
3611 required, anything of the same form as arguments for the @code{break}
3612 command. Execution will also stop upon exit from the current stack
3613 frame. This command is similar to @code{until}, but @code{advance} will
3614 not skip over recursive function calls, and the target location doesn't
3615 have to be in the same frame as the current one.
3619 @kindex si @r{(@code{stepi})}
3621 @itemx stepi @var{arg}
3623 Execute one machine instruction, then stop and return to the debugger.
3625 It is often useful to do @samp{display/i $pc} when stepping by machine
3626 instructions. This makes @value{GDBN} automatically display the next
3627 instruction to be executed, each time your program stops. @xref{Auto
3628 Display,, Automatic display}.
3630 An argument is a repeat count, as in @code{step}.
3634 @kindex ni @r{(@code{nexti})}
3636 @itemx nexti @var{arg}
3638 Execute one machine instruction, but if it is a function call,
3639 proceed until the function returns.
3641 An argument is a repeat count, as in @code{next}.
3648 A signal is an asynchronous event that can happen in a program. The
3649 operating system defines the possible kinds of signals, and gives each
3650 kind a name and a number. For example, in Unix @code{SIGINT} is the
3651 signal a program gets when you type an interrupt character (often @kbd{C-c});
3652 @code{SIGSEGV} is the signal a program gets from referencing a place in
3653 memory far away from all the areas in use; @code{SIGALRM} occurs when
3654 the alarm clock timer goes off (which happens only if your program has
3655 requested an alarm).
3657 @cindex fatal signals
3658 Some signals, including @code{SIGALRM}, are a normal part of the
3659 functioning of your program. Others, such as @code{SIGSEGV}, indicate
3660 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
3661 program has not specified in advance some other way to handle the signal.
3662 @code{SIGINT} does not indicate an error in your program, but it is normally
3663 fatal so it can carry out the purpose of the interrupt: to kill the program.
3665 @value{GDBN} has the ability to detect any occurrence of a signal in your
3666 program. You can tell @value{GDBN} in advance what to do for each kind of
3669 @cindex handling signals
3670 Normally, @value{GDBN} is set up to let the non-erroneous signals like
3671 @code{SIGALRM} be silently passed to your program
3672 (so as not to interfere with their role in the program's functioning)
3673 but to stop your program immediately whenever an error signal happens.
3674 You can change these settings with the @code{handle} command.
3677 @kindex info signals
3680 Print a table of all the kinds of signals and how @value{GDBN} has been told to
3681 handle each one. You can use this to see the signal numbers of all
3682 the defined types of signals.
3684 @code{info handle} is an alias for @code{info signals}.
3687 @item handle @var{signal} @var{keywords}@dots{}
3688 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
3689 can be the number of a signal or its name (with or without the
3690 @samp{SIG} at the beginning); a list of signal numbers of the form
3691 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
3692 known signals. The @var{keywords} say what change to make.
3696 The keywords allowed by the @code{handle} command can be abbreviated.
3697 Their full names are:
3701 @value{GDBN} should not stop your program when this signal happens. It may
3702 still print a message telling you that the signal has come in.
3705 @value{GDBN} should stop your program when this signal happens. This implies
3706 the @code{print} keyword as well.
3709 @value{GDBN} should print a message when this signal happens.
3712 @value{GDBN} should not mention the occurrence of the signal at all. This
3713 implies the @code{nostop} keyword as well.
3717 @value{GDBN} should allow your program to see this signal; your program
3718 can handle the signal, or else it may terminate if the signal is fatal
3719 and not handled. @code{pass} and @code{noignore} are synonyms.
3723 @value{GDBN} should not allow your program to see this signal.
3724 @code{nopass} and @code{ignore} are synonyms.
3728 When a signal stops your program, the signal is not visible to the
3730 continue. Your program sees the signal then, if @code{pass} is in
3731 effect for the signal in question @emph{at that time}. In other words,
3732 after @value{GDBN} reports a signal, you can use the @code{handle}
3733 command with @code{pass} or @code{nopass} to control whether your
3734 program sees that signal when you continue.
3736 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
3737 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
3738 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
3741 You can also use the @code{signal} command to prevent your program from
3742 seeing a signal, or cause it to see a signal it normally would not see,
3743 or to give it any signal at any time. For example, if your program stopped
3744 due to some sort of memory reference error, you might store correct
3745 values into the erroneous variables and continue, hoping to see more
3746 execution; but your program would probably terminate immediately as
3747 a result of the fatal signal once it saw the signal. To prevent this,
3748 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
3752 @section Stopping and starting multi-thread programs
3754 When your program has multiple threads (@pxref{Threads,, Debugging
3755 programs with multiple threads}), you can choose whether to set
3756 breakpoints on all threads, or on a particular thread.
3759 @cindex breakpoints and threads
3760 @cindex thread breakpoints
3761 @kindex break @dots{} thread @var{threadno}
3762 @item break @var{linespec} thread @var{threadno}
3763 @itemx break @var{linespec} thread @var{threadno} if @dots{}
3764 @var{linespec} specifies source lines; there are several ways of
3765 writing them, but the effect is always to specify some source line.
3767 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
3768 to specify that you only want @value{GDBN} to stop the program when a
3769 particular thread reaches this breakpoint. @var{threadno} is one of the
3770 numeric thread identifiers assigned by @value{GDBN}, shown in the first
3771 column of the @samp{info threads} display.
3773 If you do not specify @samp{thread @var{threadno}} when you set a
3774 breakpoint, the breakpoint applies to @emph{all} threads of your
3777 You can use the @code{thread} qualifier on conditional breakpoints as
3778 well; in this case, place @samp{thread @var{threadno}} before the
3779 breakpoint condition, like this:
3782 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
3787 @cindex stopped threads
3788 @cindex threads, stopped
3789 Whenever your program stops under @value{GDBN} for any reason,
3790 @emph{all} threads of execution stop, not just the current thread. This
3791 allows you to examine the overall state of the program, including
3792 switching between threads, without worrying that things may change
3795 @cindex thread breakpoints and system calls
3796 @cindex system calls and thread breakpoints
3797 @cindex premature return from system calls
3798 There is an unfortunate side effect. If one thread stops for a
3799 breakpoint, or for some other reason, and another thread is blocked in a
3800 system call, then the system call may return prematurely. This is a
3801 consequence of the interaction between multiple threads and the signals
3802 that @value{GDBN} uses to implement breakpoints and other events that
3805 To handle this problem, your program should check the return value of
3806 each system call and react appropriately. This is good programming
3809 For example, do not write code like this:
3815 The call to @code{sleep} will return early if a different thread stops
3816 at a breakpoint or for some other reason.
3818 Instead, write this:
3823 unslept = sleep (unslept);
3826 A system call is allowed to return early, so the system is still
3827 conforming to its specification. But @value{GDBN} does cause your
3828 multi-threaded program to behave differently than it would without
3831 Also, @value{GDBN} uses internal breakpoints in the thread library to
3832 monitor certain events such as thread creation and thread destruction.
3833 When such an event happens, a system call in another thread may return
3834 prematurely, even though your program does not appear to stop.
3836 @cindex continuing threads
3837 @cindex threads, continuing
3838 Conversely, whenever you restart the program, @emph{all} threads start
3839 executing. @emph{This is true even when single-stepping} with commands
3840 like @code{step} or @code{next}.
3842 In particular, @value{GDBN} cannot single-step all threads in lockstep.
3843 Since thread scheduling is up to your debugging target's operating
3844 system (not controlled by @value{GDBN}), other threads may
3845 execute more than one statement while the current thread completes a
3846 single step. Moreover, in general other threads stop in the middle of a
3847 statement, rather than at a clean statement boundary, when the program
3850 You might even find your program stopped in another thread after
3851 continuing or even single-stepping. This happens whenever some other
3852 thread runs into a breakpoint, a signal, or an exception before the
3853 first thread completes whatever you requested.
3855 On some OSes, you can lock the OS scheduler and thus allow only a single
3859 @item set scheduler-locking @var{mode}
3860 Set the scheduler locking mode. If it is @code{off}, then there is no
3861 locking and any thread may run at any time. If @code{on}, then only the
3862 current thread may run when the inferior is resumed. The @code{step}
3863 mode optimizes for single-stepping. It stops other threads from
3864 ``seizing the prompt'' by preempting the current thread while you are
3865 stepping. Other threads will only rarely (or never) get a chance to run
3866 when you step. They are more likely to run when you @samp{next} over a
3867 function call, and they are completely free to run when you use commands
3868 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
3869 thread hits a breakpoint during its timeslice, they will never steal the
3870 @value{GDBN} prompt away from the thread that you are debugging.
3872 @item show scheduler-locking
3873 Display the current scheduler locking mode.
3878 @chapter Examining the Stack
3880 When your program has stopped, the first thing you need to know is where it
3881 stopped and how it got there.
3884 Each time your program performs a function call, information about the call
3886 That information includes the location of the call in your program,
3887 the arguments of the call,
3888 and the local variables of the function being called.
3889 The information is saved in a block of data called a @dfn{stack frame}.
3890 The stack frames are allocated in a region of memory called the @dfn{call
3893 When your program stops, the @value{GDBN} commands for examining the
3894 stack allow you to see all of this information.
3896 @cindex selected frame
3897 One of the stack frames is @dfn{selected} by @value{GDBN} and many
3898 @value{GDBN} commands refer implicitly to the selected frame. In
3899 particular, whenever you ask @value{GDBN} for the value of a variable in
3900 your program, the value is found in the selected frame. There are
3901 special @value{GDBN} commands to select whichever frame you are
3902 interested in. @xref{Selection, ,Selecting a frame}.
3904 When your program stops, @value{GDBN} automatically selects the
3905 currently executing frame and describes it briefly, similar to the
3906 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
3909 * Frames:: Stack frames
3910 * Backtrace:: Backtraces
3911 * Selection:: Selecting a frame
3912 * Frame Info:: Information on a frame
3917 @section Stack frames
3919 @cindex frame, definition
3921 The call stack is divided up into contiguous pieces called @dfn{stack
3922 frames}, or @dfn{frames} for short; each frame is the data associated
3923 with one call to one function. The frame contains the arguments given
3924 to the function, the function's local variables, and the address at
3925 which the function is executing.
3927 @cindex initial frame
3928 @cindex outermost frame
3929 @cindex innermost frame
3930 When your program is started, the stack has only one frame, that of the
3931 function @code{main}. This is called the @dfn{initial} frame or the
3932 @dfn{outermost} frame. Each time a function is called, a new frame is
3933 made. Each time a function returns, the frame for that function invocation
3934 is eliminated. If a function is recursive, there can be many frames for
3935 the same function. The frame for the function in which execution is
3936 actually occurring is called the @dfn{innermost} frame. This is the most
3937 recently created of all the stack frames that still exist.
3939 @cindex frame pointer
3940 Inside your program, stack frames are identified by their addresses. A
3941 stack frame consists of many bytes, each of which has its own address; each
3942 kind of computer has a convention for choosing one byte whose
3943 address serves as the address of the frame. Usually this address is kept
3944 in a register called the @dfn{frame pointer register} while execution is
3945 going on in that frame.
3947 @cindex frame number
3948 @value{GDBN} assigns numbers to all existing stack frames, starting with
3949 zero for the innermost frame, one for the frame that called it,
3950 and so on upward. These numbers do not really exist in your program;
3951 they are assigned by @value{GDBN} to give you a way of designating stack
3952 frames in @value{GDBN} commands.
3954 @c The -fomit-frame-pointer below perennially causes hbox overflow
3955 @c underflow problems.
3956 @cindex frameless execution
3957 Some compilers provide a way to compile functions so that they operate
3958 without stack frames. (For example, the @value{GCC} option
3960 @samp{-fomit-frame-pointer}
3962 generates functions without a frame.)
3963 This is occasionally done with heavily used library functions to save
3964 the frame setup time. @value{GDBN} has limited facilities for dealing
3965 with these function invocations. If the innermost function invocation
3966 has no stack frame, @value{GDBN} nevertheless regards it as though
3967 it had a separate frame, which is numbered zero as usual, allowing
3968 correct tracing of the function call chain. However, @value{GDBN} has
3969 no provision for frameless functions elsewhere in the stack.
3972 @kindex frame@r{, command}
3973 @cindex current stack frame
3974 @item frame @var{args}
3975 The @code{frame} command allows you to move from one stack frame to another,
3976 and to print the stack frame you select. @var{args} may be either the
3977 address of the frame or the stack frame number. Without an argument,
3978 @code{frame} prints the current stack frame.
3980 @kindex select-frame
3981 @cindex selecting frame silently
3983 The @code{select-frame} command allows you to move from one stack frame
3984 to another without printing the frame. This is the silent version of
3993 @cindex stack traces
3994 A backtrace is a summary of how your program got where it is. It shows one
3995 line per frame, for many frames, starting with the currently executing
3996 frame (frame zero), followed by its caller (frame one), and on up the
4001 @kindex bt @r{(@code{backtrace})}
4004 Print a backtrace of the entire stack: one line per frame for all
4005 frames in the stack.
4007 You can stop the backtrace at any time by typing the system interrupt
4008 character, normally @kbd{C-c}.
4010 @item backtrace @var{n}
4012 Similar, but print only the innermost @var{n} frames.
4014 @item backtrace -@var{n}
4016 Similar, but print only the outermost @var{n} frames.
4021 @kindex info s @r{(@code{info stack})}
4022 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4023 are additional aliases for @code{backtrace}.
4025 Each line in the backtrace shows the frame number and the function name.
4026 The program counter value is also shown---unless you use @code{set
4027 print address off}. The backtrace also shows the source file name and
4028 line number, as well as the arguments to the function. The program
4029 counter value is omitted if it is at the beginning of the code for that
4032 Here is an example of a backtrace. It was made with the command
4033 @samp{bt 3}, so it shows the innermost three frames.
4037 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4039 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4040 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4042 (More stack frames follow...)
4047 The display for frame zero does not begin with a program counter
4048 value, indicating that your program has stopped at the beginning of the
4049 code for line @code{993} of @code{builtin.c}.
4051 @kindex set backtrace past-main
4052 @kindex show backtrace past-main
4053 @kindex set backtrace limit
4054 @kindex show backtrace limit
4056 Most programs have a standard user entry point---a place where system
4057 libraries and startup code transition into user code. For C this is
4058 @code{main}. When @value{GDBN} finds the entry function in a backtrace
4059 it will terminate the backtrace, to avoid tracing into highly
4060 system-specific (and generally uninteresting) code.
4062 If you need to examine the startup code, or limit the number of levels
4063 in a backtrace, you can change this behavior:
4066 @item set backtrace past-main
4067 @itemx set backtrace past-main on
4068 Backtraces will continue past the user entry point.
4070 @item set backtrace past-main off
4071 Backtraces will stop when they encounter the user entry point. This is the
4074 @item show backtrace past-main
4075 Display the current user entry point backtrace policy.
4077 @item set backtrace limit @var{n}
4078 @itemx set backtrace limit 0
4079 @cindex backtrace limit
4080 Limit the backtrace to @var{n} levels. A value of zero means
4083 @item show backtrace limit
4084 Display the current limit on backtrace levels.
4088 @section Selecting a frame
4090 Most commands for examining the stack and other data in your program work on
4091 whichever stack frame is selected at the moment. Here are the commands for
4092 selecting a stack frame; all of them finish by printing a brief description
4093 of the stack frame just selected.
4096 @kindex frame@r{, selecting}
4097 @kindex f @r{(@code{frame})}
4100 Select frame number @var{n}. Recall that frame zero is the innermost
4101 (currently executing) frame, frame one is the frame that called the
4102 innermost one, and so on. The highest-numbered frame is the one for
4105 @item frame @var{addr}
4107 Select the frame at address @var{addr}. This is useful mainly if the
4108 chaining of stack frames has been damaged by a bug, making it
4109 impossible for @value{GDBN} to assign numbers properly to all frames. In
4110 addition, this can be useful when your program has multiple stacks and
4111 switches between them.
4113 On the SPARC architecture, @code{frame} needs two addresses to
4114 select an arbitrary frame: a frame pointer and a stack pointer.
4116 On the MIPS and Alpha architecture, it needs two addresses: a stack
4117 pointer and a program counter.
4119 On the 29k architecture, it needs three addresses: a register stack
4120 pointer, a program counter, and a memory stack pointer.
4121 @c note to future updaters: this is conditioned on a flag
4122 @c SETUP_ARBITRARY_FRAME in the tm-*.h files. The above is up to date
4123 @c as of 27 Jan 1994.
4127 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4128 advances toward the outermost frame, to higher frame numbers, to frames
4129 that have existed longer. @var{n} defaults to one.
4132 @kindex do @r{(@code{down})}
4134 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4135 advances toward the innermost frame, to lower frame numbers, to frames
4136 that were created more recently. @var{n} defaults to one. You may
4137 abbreviate @code{down} as @code{do}.
4140 All of these commands end by printing two lines of output describing the
4141 frame. The first line shows the frame number, the function name, the
4142 arguments, and the source file and line number of execution in that
4143 frame. The second line shows the text of that source line.
4151 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4153 10 read_input_file (argv[i]);
4157 After such a printout, the @code{list} command with no arguments
4158 prints ten lines centered on the point of execution in the frame.
4159 You can also edit the program at the point of execution with your favorite
4160 editing program by typing @code{edit}.
4161 @xref{List, ,Printing source lines},
4165 @kindex down-silently
4167 @item up-silently @var{n}
4168 @itemx down-silently @var{n}
4169 These two commands are variants of @code{up} and @code{down},
4170 respectively; they differ in that they do their work silently, without
4171 causing display of the new frame. They are intended primarily for use
4172 in @value{GDBN} command scripts, where the output might be unnecessary and
4177 @section Information about a frame
4179 There are several other commands to print information about the selected
4185 When used without any argument, this command does not change which
4186 frame is selected, but prints a brief description of the currently
4187 selected stack frame. It can be abbreviated @code{f}. With an
4188 argument, this command is used to select a stack frame.
4189 @xref{Selection, ,Selecting a frame}.
4192 @kindex info f @r{(@code{info frame})}
4195 This command prints a verbose description of the selected stack frame,
4200 the address of the frame
4202 the address of the next frame down (called by this frame)
4204 the address of the next frame up (caller of this frame)
4206 the language in which the source code corresponding to this frame is written
4208 the address of the frame's arguments
4210 the address of the frame's local variables
4212 the program counter saved in it (the address of execution in the caller frame)
4214 which registers were saved in the frame
4217 @noindent The verbose description is useful when
4218 something has gone wrong that has made the stack format fail to fit
4219 the usual conventions.
4221 @item info frame @var{addr}
4222 @itemx info f @var{addr}
4223 Print a verbose description of the frame at address @var{addr}, without
4224 selecting that frame. The selected frame remains unchanged by this
4225 command. This requires the same kind of address (more than one for some
4226 architectures) that you specify in the @code{frame} command.
4227 @xref{Selection, ,Selecting a frame}.
4231 Print the arguments of the selected frame, each on a separate line.
4235 Print the local variables of the selected frame, each on a separate
4236 line. These are all variables (declared either static or automatic)
4237 accessible at the point of execution of the selected frame.
4240 @cindex catch exceptions, list active handlers
4241 @cindex exception handlers, how to list
4243 Print a list of all the exception handlers that are active in the
4244 current stack frame at the current point of execution. To see other
4245 exception handlers, visit the associated frame (using the @code{up},
4246 @code{down}, or @code{frame} commands); then type @code{info catch}.
4247 @xref{Set Catchpoints, , Setting catchpoints}.
4253 @chapter Examining Source Files
4255 @value{GDBN} can print parts of your program's source, since the debugging
4256 information recorded in the program tells @value{GDBN} what source files were
4257 used to build it. When your program stops, @value{GDBN} spontaneously prints
4258 the line where it stopped. Likewise, when you select a stack frame
4259 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4260 execution in that frame has stopped. You can print other portions of
4261 source files by explicit command.
4263 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4264 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4265 @value{GDBN} under @sc{gnu} Emacs}.
4268 * List:: Printing source lines
4269 * Edit:: Editing source files
4270 * Search:: Searching source files
4271 * Source Path:: Specifying source directories
4272 * Machine Code:: Source and machine code
4276 @section Printing source lines
4279 @kindex l @r{(@code{list})}
4280 To print lines from a source file, use the @code{list} command
4281 (abbreviated @code{l}). By default, ten lines are printed.
4282 There are several ways to specify what part of the file you want to print.
4284 Here are the forms of the @code{list} command most commonly used:
4287 @item list @var{linenum}
4288 Print lines centered around line number @var{linenum} in the
4289 current source file.
4291 @item list @var{function}
4292 Print lines centered around the beginning of function
4296 Print more lines. If the last lines printed were printed with a
4297 @code{list} command, this prints lines following the last lines
4298 printed; however, if the last line printed was a solitary line printed
4299 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4300 Stack}), this prints lines centered around that line.
4303 Print lines just before the lines last printed.
4306 By default, @value{GDBN} prints ten source lines with any of these forms of
4307 the @code{list} command. You can change this using @code{set listsize}:
4310 @kindex set listsize
4311 @item set listsize @var{count}
4312 Make the @code{list} command display @var{count} source lines (unless
4313 the @code{list} argument explicitly specifies some other number).
4315 @kindex show listsize
4317 Display the number of lines that @code{list} prints.
4320 Repeating a @code{list} command with @key{RET} discards the argument,
4321 so it is equivalent to typing just @code{list}. This is more useful
4322 than listing the same lines again. An exception is made for an
4323 argument of @samp{-}; that argument is preserved in repetition so that
4324 each repetition moves up in the source file.
4327 In general, the @code{list} command expects you to supply zero, one or two
4328 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4329 of writing them, but the effect is always to specify some source line.
4330 Here is a complete description of the possible arguments for @code{list}:
4333 @item list @var{linespec}
4334 Print lines centered around the line specified by @var{linespec}.
4336 @item list @var{first},@var{last}
4337 Print lines from @var{first} to @var{last}. Both arguments are
4340 @item list ,@var{last}
4341 Print lines ending with @var{last}.
4343 @item list @var{first},
4344 Print lines starting with @var{first}.
4347 Print lines just after the lines last printed.
4350 Print lines just before the lines last printed.
4353 As described in the preceding table.
4356 Here are the ways of specifying a single source line---all the
4361 Specifies line @var{number} of the current source file.
4362 When a @code{list} command has two linespecs, this refers to
4363 the same source file as the first linespec.
4366 Specifies the line @var{offset} lines after the last line printed.
4367 When used as the second linespec in a @code{list} command that has
4368 two, this specifies the line @var{offset} lines down from the
4372 Specifies the line @var{offset} lines before the last line printed.
4374 @item @var{filename}:@var{number}
4375 Specifies line @var{number} in the source file @var{filename}.
4377 @item @var{function}
4378 Specifies the line that begins the body of the function @var{function}.
4379 For example: in C, this is the line with the open brace.
4381 @item @var{filename}:@var{function}
4382 Specifies the line of the open-brace that begins the body of the
4383 function @var{function} in the file @var{filename}. You only need the
4384 file name with a function name to avoid ambiguity when there are
4385 identically named functions in different source files.
4387 @item *@var{address}
4388 Specifies the line containing the program address @var{address}.
4389 @var{address} may be any expression.
4393 @section Editing source files
4394 @cindex editing source files
4397 @kindex e @r{(@code{edit})}
4398 To edit the lines in a source file, use the @code{edit} command.
4399 The editing program of your choice
4400 is invoked with the current line set to
4401 the active line in the program.
4402 Alternatively, there are several ways to specify what part of the file you
4403 want to print if you want to see other parts of the program.
4405 Here are the forms of the @code{edit} command most commonly used:
4409 Edit the current source file at the active line number in the program.
4411 @item edit @var{number}
4412 Edit the current source file with @var{number} as the active line number.
4414 @item edit @var{function}
4415 Edit the file containing @var{function} at the beginning of its definition.
4417 @item edit @var{filename}:@var{number}
4418 Specifies line @var{number} in the source file @var{filename}.
4420 @item edit @var{filename}:@var{function}
4421 Specifies the line that begins the body of the
4422 function @var{function} in the file @var{filename}. You only need the
4423 file name with a function name to avoid ambiguity when there are
4424 identically named functions in different source files.
4426 @item edit *@var{address}
4427 Specifies the line containing the program address @var{address}.
4428 @var{address} may be any expression.
4431 @subsection Choosing your editor
4432 You can customize @value{GDBN} to use any editor you want
4434 The only restriction is that your editor (say @code{ex}), recognizes the
4435 following command-line syntax:
4437 ex +@var{number} file
4439 The optional numeric value +@var{number} designates the active line in
4440 the file.}. By default, it is @value{EDITOR}, but you can change this
4441 by setting the environment variable @code{EDITOR} before using
4442 @value{GDBN}. For example, to configure @value{GDBN} to use the
4443 @code{vi} editor, you could use these commands with the @code{sh} shell:
4449 or in the @code{csh} shell,
4451 setenv EDITOR /usr/bin/vi
4456 @section Searching source files
4458 @kindex reverse-search
4460 There are two commands for searching through the current source file for a
4465 @kindex forward-search
4466 @item forward-search @var{regexp}
4467 @itemx search @var{regexp}
4468 The command @samp{forward-search @var{regexp}} checks each line,
4469 starting with the one following the last line listed, for a match for
4470 @var{regexp}. It lists the line that is found. You can use the
4471 synonym @samp{search @var{regexp}} or abbreviate the command name as
4474 @item reverse-search @var{regexp}
4475 The command @samp{reverse-search @var{regexp}} checks each line, starting
4476 with the one before the last line listed and going backward, for a match
4477 for @var{regexp}. It lists the line that is found. You can abbreviate
4478 this command as @code{rev}.
4482 @section Specifying source directories
4485 @cindex directories for source files
4486 Executable programs sometimes do not record the directories of the source
4487 files from which they were compiled, just the names. Even when they do,
4488 the directories could be moved between the compilation and your debugging
4489 session. @value{GDBN} has a list of directories to search for source files;
4490 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
4491 it tries all the directories in the list, in the order they are present
4492 in the list, until it finds a file with the desired name. Note that
4493 the executable search path is @emph{not} used for this purpose. Neither is
4494 the current working directory, unless it happens to be in the source
4497 If @value{GDBN} cannot find a source file in the source path, and the
4498 object program records a directory, @value{GDBN} tries that directory
4499 too. If the source path is empty, and there is no record of the
4500 compilation directory, @value{GDBN} looks in the current directory as a
4503 Whenever you reset or rearrange the source path, @value{GDBN} clears out
4504 any information it has cached about where source files are found and where
4505 each line is in the file.
4509 When you start @value{GDBN}, its source path includes only @samp{cdir}
4510 and @samp{cwd}, in that order.
4511 To add other directories, use the @code{directory} command.
4514 @item directory @var{dirname} @dots{}
4515 @item dir @var{dirname} @dots{}
4516 Add directory @var{dirname} to the front of the source path. Several
4517 directory names may be given to this command, separated by @samp{:}
4518 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
4519 part of absolute file names) or
4520 whitespace. You may specify a directory that is already in the source
4521 path; this moves it forward, so @value{GDBN} searches it sooner.
4525 @vindex $cdir@r{, convenience variable}
4526 @vindex $cwdr@r{, convenience variable}
4527 @cindex compilation directory
4528 @cindex current directory
4529 @cindex working directory
4530 @cindex directory, current
4531 @cindex directory, compilation
4532 You can use the string @samp{$cdir} to refer to the compilation
4533 directory (if one is recorded), and @samp{$cwd} to refer to the current
4534 working directory. @samp{$cwd} is not the same as @samp{.}---the former
4535 tracks the current working directory as it changes during your @value{GDBN}
4536 session, while the latter is immediately expanded to the current
4537 directory at the time you add an entry to the source path.
4540 Reset the source path to empty again. This requires confirmation.
4542 @c RET-repeat for @code{directory} is explicitly disabled, but since
4543 @c repeating it would be a no-op we do not say that. (thanks to RMS)
4545 @item show directories
4546 @kindex show directories
4547 Print the source path: show which directories it contains.
4550 If your source path is cluttered with directories that are no longer of
4551 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
4552 versions of source. You can correct the situation as follows:
4556 Use @code{directory} with no argument to reset the source path to empty.
4559 Use @code{directory} with suitable arguments to reinstall the
4560 directories you want in the source path. You can add all the
4561 directories in one command.
4565 @section Source and machine code
4567 You can use the command @code{info line} to map source lines to program
4568 addresses (and vice versa), and the command @code{disassemble} to display
4569 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
4570 mode, the @code{info line} command causes the arrow to point to the
4571 line specified. Also, @code{info line} prints addresses in symbolic form as
4576 @item info line @var{linespec}
4577 Print the starting and ending addresses of the compiled code for
4578 source line @var{linespec}. You can specify source lines in any of
4579 the ways understood by the @code{list} command (@pxref{List, ,Printing
4583 For example, we can use @code{info line} to discover the location of
4584 the object code for the first line of function
4585 @code{m4_changequote}:
4587 @c FIXME: I think this example should also show the addresses in
4588 @c symbolic form, as they usually would be displayed.
4590 (@value{GDBP}) info line m4_changequote
4591 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
4595 We can also inquire (using @code{*@var{addr}} as the form for
4596 @var{linespec}) what source line covers a particular address:
4598 (@value{GDBP}) info line *0x63ff
4599 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
4602 @cindex @code{$_} and @code{info line}
4603 @kindex x@r{(examine), and} info line
4604 After @code{info line}, the default address for the @code{x} command
4605 is changed to the starting address of the line, so that @samp{x/i} is
4606 sufficient to begin examining the machine code (@pxref{Memory,
4607 ,Examining memory}). Also, this address is saved as the value of the
4608 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
4613 @cindex assembly instructions
4614 @cindex instructions, assembly
4615 @cindex machine instructions
4616 @cindex listing machine instructions
4618 This specialized command dumps a range of memory as machine
4619 instructions. The default memory range is the function surrounding the
4620 program counter of the selected frame. A single argument to this
4621 command is a program counter value; @value{GDBN} dumps the function
4622 surrounding this value. Two arguments specify a range of addresses
4623 (first inclusive, second exclusive) to dump.
4626 The following example shows the disassembly of a range of addresses of
4627 HP PA-RISC 2.0 code:
4630 (@value{GDBP}) disas 0x32c4 0x32e4
4631 Dump of assembler code from 0x32c4 to 0x32e4:
4632 0x32c4 <main+204>: addil 0,dp
4633 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
4634 0x32cc <main+212>: ldil 0x3000,r31
4635 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
4636 0x32d4 <main+220>: ldo 0(r31),rp
4637 0x32d8 <main+224>: addil -0x800,dp
4638 0x32dc <main+228>: ldo 0x588(r1),r26
4639 0x32e0 <main+232>: ldil 0x3000,r31
4640 End of assembler dump.
4643 Some architectures have more than one commonly-used set of instruction
4644 mnemonics or other syntax.
4647 @kindex set disassembly-flavor
4648 @cindex assembly instructions
4649 @cindex instructions, assembly
4650 @cindex machine instructions
4651 @cindex listing machine instructions
4652 @cindex Intel disassembly flavor
4653 @cindex AT&T disassembly flavor
4654 @item set disassembly-flavor @var{instruction-set}
4655 Select the instruction set to use when disassembling the
4656 program via the @code{disassemble} or @code{x/i} commands.
4658 Currently this command is only defined for the Intel x86 family. You
4659 can set @var{instruction-set} to either @code{intel} or @code{att}.
4660 The default is @code{att}, the AT&T flavor used by default by Unix
4661 assemblers for x86-based targets.
4666 @chapter Examining Data
4668 @cindex printing data
4669 @cindex examining data
4672 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
4673 @c document because it is nonstandard... Under Epoch it displays in a
4674 @c different window or something like that.
4675 The usual way to examine data in your program is with the @code{print}
4676 command (abbreviated @code{p}), or its synonym @code{inspect}. It
4677 evaluates and prints the value of an expression of the language your
4678 program is written in (@pxref{Languages, ,Using @value{GDBN} with
4679 Different Languages}).
4682 @item print @var{expr}
4683 @itemx print /@var{f} @var{expr}
4684 @var{expr} is an expression (in the source language). By default the
4685 value of @var{expr} is printed in a format appropriate to its data type;
4686 you can choose a different format by specifying @samp{/@var{f}}, where
4687 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
4691 @itemx print /@var{f}
4692 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
4693 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
4694 conveniently inspect the same value in an alternative format.
4697 A more low-level way of examining data is with the @code{x} command.
4698 It examines data in memory at a specified address and prints it in a
4699 specified format. @xref{Memory, ,Examining memory}.
4701 If you are interested in information about types, or about how the
4702 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
4703 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
4707 * Expressions:: Expressions
4708 * Variables:: Program variables
4709 * Arrays:: Artificial arrays
4710 * Output Formats:: Output formats
4711 * Memory:: Examining memory
4712 * Auto Display:: Automatic display
4713 * Print Settings:: Print settings
4714 * Value History:: Value history
4715 * Convenience Vars:: Convenience variables
4716 * Registers:: Registers
4717 * Floating Point Hardware:: Floating point hardware
4718 * Vector Unit:: Vector Unit
4719 * Auxiliary Vector:: Auxiliary data provided by operating system
4720 * Memory Region Attributes:: Memory region attributes
4721 * Dump/Restore Files:: Copy between memory and a file
4722 * Character Sets:: Debugging programs that use a different
4723 character set than GDB does
4727 @section Expressions
4730 @code{print} and many other @value{GDBN} commands accept an expression and
4731 compute its value. Any kind of constant, variable or operator defined
4732 by the programming language you are using is valid in an expression in
4733 @value{GDBN}. This includes conditional expressions, function calls,
4734 casts, and string constants. It also includes preprocessor macros, if
4735 you compiled your program to include this information; see
4738 @value{GDBN} supports array constants in expressions input by
4739 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
4740 you can use the command @code{print @{1, 2, 3@}} to build up an array in
4741 memory that is @code{malloc}ed in the target program.
4743 Because C is so widespread, most of the expressions shown in examples in
4744 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
4745 Languages}, for information on how to use expressions in other
4748 In this section, we discuss operators that you can use in @value{GDBN}
4749 expressions regardless of your programming language.
4751 Casts are supported in all languages, not just in C, because it is so
4752 useful to cast a number into a pointer in order to examine a structure
4753 at that address in memory.
4754 @c FIXME: casts supported---Mod2 true?
4756 @value{GDBN} supports these operators, in addition to those common
4757 to programming languages:
4761 @samp{@@} is a binary operator for treating parts of memory as arrays.
4762 @xref{Arrays, ,Artificial arrays}, for more information.
4765 @samp{::} allows you to specify a variable in terms of the file or
4766 function where it is defined. @xref{Variables, ,Program variables}.
4768 @cindex @{@var{type}@}
4769 @cindex type casting memory
4770 @cindex memory, viewing as typed object
4771 @cindex casts, to view memory
4772 @item @{@var{type}@} @var{addr}
4773 Refers to an object of type @var{type} stored at address @var{addr} in
4774 memory. @var{addr} may be any expression whose value is an integer or
4775 pointer (but parentheses are required around binary operators, just as in
4776 a cast). This construct is allowed regardless of what kind of data is
4777 normally supposed to reside at @var{addr}.
4781 @section Program variables
4783 The most common kind of expression to use is the name of a variable
4786 Variables in expressions are understood in the selected stack frame
4787 (@pxref{Selection, ,Selecting a frame}); they must be either:
4791 global (or file-static)
4798 visible according to the scope rules of the
4799 programming language from the point of execution in that frame
4802 @noindent This means that in the function
4817 you can examine and use the variable @code{a} whenever your program is
4818 executing within the function @code{foo}, but you can only use or
4819 examine the variable @code{b} while your program is executing inside
4820 the block where @code{b} is declared.
4822 @cindex variable name conflict
4823 There is an exception: you can refer to a variable or function whose
4824 scope is a single source file even if the current execution point is not
4825 in this file. But it is possible to have more than one such variable or
4826 function with the same name (in different source files). If that
4827 happens, referring to that name has unpredictable effects. If you wish,
4828 you can specify a static variable in a particular function or file,
4829 using the colon-colon notation:
4831 @cindex colon-colon, context for variables/functions
4833 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
4834 @cindex @code{::}, context for variables/functions
4837 @var{file}::@var{variable}
4838 @var{function}::@var{variable}
4842 Here @var{file} or @var{function} is the name of the context for the
4843 static @var{variable}. In the case of file names, you can use quotes to
4844 make sure @value{GDBN} parses the file name as a single word---for example,
4845 to print a global value of @code{x} defined in @file{f2.c}:
4848 (@value{GDBP}) p 'f2.c'::x
4851 @cindex C@t{++} scope resolution
4852 This use of @samp{::} is very rarely in conflict with the very similar
4853 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
4854 scope resolution operator in @value{GDBN} expressions.
4855 @c FIXME: Um, so what happens in one of those rare cases where it's in
4858 @cindex wrong values
4859 @cindex variable values, wrong
4861 @emph{Warning:} Occasionally, a local variable may appear to have the
4862 wrong value at certain points in a function---just after entry to a new
4863 scope, and just before exit.
4865 You may see this problem when you are stepping by machine instructions.
4866 This is because, on most machines, it takes more than one instruction to
4867 set up a stack frame (including local variable definitions); if you are
4868 stepping by machine instructions, variables may appear to have the wrong
4869 values until the stack frame is completely built. On exit, it usually
4870 also takes more than one machine instruction to destroy a stack frame;
4871 after you begin stepping through that group of instructions, local
4872 variable definitions may be gone.
4874 This may also happen when the compiler does significant optimizations.
4875 To be sure of always seeing accurate values, turn off all optimization
4878 @cindex ``No symbol "foo" in current context''
4879 Another possible effect of compiler optimizations is to optimize
4880 unused variables out of existence, or assign variables to registers (as
4881 opposed to memory addresses). Depending on the support for such cases
4882 offered by the debug info format used by the compiler, @value{GDBN}
4883 might not be able to display values for such local variables. If that
4884 happens, @value{GDBN} will print a message like this:
4887 No symbol "foo" in current context.
4890 To solve such problems, either recompile without optimizations, or use a
4891 different debug info format, if the compiler supports several such
4892 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler
4893 usually supports the @option{-gstabs+} option. @option{-gstabs+}
4894 produces debug info in a format that is superior to formats such as
4895 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
4896 an effective form for debug info. @xref{Debugging Options,,Options
4897 for Debugging Your Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}.
4901 @section Artificial arrays
4903 @cindex artificial array
4904 @kindex @@@r{, referencing memory as an array}
4905 It is often useful to print out several successive objects of the
4906 same type in memory; a section of an array, or an array of
4907 dynamically determined size for which only a pointer exists in the
4910 You can do this by referring to a contiguous span of memory as an
4911 @dfn{artificial array}, using the binary operator @samp{@@}. The left
4912 operand of @samp{@@} should be the first element of the desired array
4913 and be an individual object. The right operand should be the desired length
4914 of the array. The result is an array value whose elements are all of
4915 the type of the left argument. The first element is actually the left
4916 argument; the second element comes from bytes of memory immediately
4917 following those that hold the first element, and so on. Here is an
4918 example. If a program says
4921 int *array = (int *) malloc (len * sizeof (int));
4925 you can print the contents of @code{array} with
4931 The left operand of @samp{@@} must reside in memory. Array values made
4932 with @samp{@@} in this way behave just like other arrays in terms of
4933 subscripting, and are coerced to pointers when used in expressions.
4934 Artificial arrays most often appear in expressions via the value history
4935 (@pxref{Value History, ,Value history}), after printing one out.
4937 Another way to create an artificial array is to use a cast.
4938 This re-interprets a value as if it were an array.
4939 The value need not be in memory:
4941 (@value{GDBP}) p/x (short[2])0x12345678
4942 $1 = @{0x1234, 0x5678@}
4945 As a convenience, if you leave the array length out (as in
4946 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
4947 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
4949 (@value{GDBP}) p/x (short[])0x12345678
4950 $2 = @{0x1234, 0x5678@}
4953 Sometimes the artificial array mechanism is not quite enough; in
4954 moderately complex data structures, the elements of interest may not
4955 actually be adjacent---for example, if you are interested in the values
4956 of pointers in an array. One useful work-around in this situation is
4957 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
4958 variables}) as a counter in an expression that prints the first
4959 interesting value, and then repeat that expression via @key{RET}. For
4960 instance, suppose you have an array @code{dtab} of pointers to
4961 structures, and you are interested in the values of a field @code{fv}
4962 in each structure. Here is an example of what you might type:
4972 @node Output Formats
4973 @section Output formats
4975 @cindex formatted output
4976 @cindex output formats
4977 By default, @value{GDBN} prints a value according to its data type. Sometimes
4978 this is not what you want. For example, you might want to print a number
4979 in hex, or a pointer in decimal. Or you might want to view data in memory
4980 at a certain address as a character string or as an instruction. To do
4981 these things, specify an @dfn{output format} when you print a value.
4983 The simplest use of output formats is to say how to print a value
4984 already computed. This is done by starting the arguments of the
4985 @code{print} command with a slash and a format letter. The format
4986 letters supported are:
4990 Regard the bits of the value as an integer, and print the integer in
4994 Print as integer in signed decimal.
4997 Print as integer in unsigned decimal.
5000 Print as integer in octal.
5003 Print as integer in binary. The letter @samp{t} stands for ``two''.
5004 @footnote{@samp{b} cannot be used because these format letters are also
5005 used with the @code{x} command, where @samp{b} stands for ``byte'';
5006 see @ref{Memory,,Examining memory}.}
5009 @cindex unknown address, locating
5010 @cindex locate address
5011 Print as an address, both absolute in hexadecimal and as an offset from
5012 the nearest preceding symbol. You can use this format used to discover
5013 where (in what function) an unknown address is located:
5016 (@value{GDBP}) p/a 0x54320
5017 $3 = 0x54320 <_initialize_vx+396>
5021 The command @code{info symbol 0x54320} yields similar results.
5022 @xref{Symbols, info symbol}.
5025 Regard as an integer and print it as a character constant.
5028 Regard the bits of the value as a floating point number and print
5029 using typical floating point syntax.
5032 For example, to print the program counter in hex (@pxref{Registers}), type
5039 Note that no space is required before the slash; this is because command
5040 names in @value{GDBN} cannot contain a slash.
5042 To reprint the last value in the value history with a different format,
5043 you can use the @code{print} command with just a format and no
5044 expression. For example, @samp{p/x} reprints the last value in hex.
5047 @section Examining memory
5049 You can use the command @code{x} (for ``examine'') to examine memory in
5050 any of several formats, independently of your program's data types.
5052 @cindex examining memory
5054 @kindex x @r{(examine memory)}
5055 @item x/@var{nfu} @var{addr}
5058 Use the @code{x} command to examine memory.
5061 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5062 much memory to display and how to format it; @var{addr} is an
5063 expression giving the address where you want to start displaying memory.
5064 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5065 Several commands set convenient defaults for @var{addr}.
5068 @item @var{n}, the repeat count
5069 The repeat count is a decimal integer; the default is 1. It specifies
5070 how much memory (counting by units @var{u}) to display.
5071 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5074 @item @var{f}, the display format
5075 The display format is one of the formats used by @code{print},
5076 @samp{s} (null-terminated string), or @samp{i} (machine instruction).
5077 The default is @samp{x} (hexadecimal) initially.
5078 The default changes each time you use either @code{x} or @code{print}.
5080 @item @var{u}, the unit size
5081 The unit size is any of
5087 Halfwords (two bytes).
5089 Words (four bytes). This is the initial default.
5091 Giant words (eight bytes).
5094 Each time you specify a unit size with @code{x}, that size becomes the
5095 default unit the next time you use @code{x}. (For the @samp{s} and
5096 @samp{i} formats, the unit size is ignored and is normally not written.)
5098 @item @var{addr}, starting display address
5099 @var{addr} is the address where you want @value{GDBN} to begin displaying
5100 memory. The expression need not have a pointer value (though it may);
5101 it is always interpreted as an integer address of a byte of memory.
5102 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5103 @var{addr} is usually just after the last address examined---but several
5104 other commands also set the default address: @code{info breakpoints} (to
5105 the address of the last breakpoint listed), @code{info line} (to the
5106 starting address of a line), and @code{print} (if you use it to display
5107 a value from memory).
5110 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5111 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5112 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5113 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5114 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5116 Since the letters indicating unit sizes are all distinct from the
5117 letters specifying output formats, you do not have to remember whether
5118 unit size or format comes first; either order works. The output
5119 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5120 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5122 Even though the unit size @var{u} is ignored for the formats @samp{s}
5123 and @samp{i}, you might still want to use a count @var{n}; for example,
5124 @samp{3i} specifies that you want to see three machine instructions,
5125 including any operands. The command @code{disassemble} gives an
5126 alternative way of inspecting machine instructions; see @ref{Machine
5127 Code,,Source and machine code}.
5129 All the defaults for the arguments to @code{x} are designed to make it
5130 easy to continue scanning memory with minimal specifications each time
5131 you use @code{x}. For example, after you have inspected three machine
5132 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5133 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5134 the repeat count @var{n} is used again; the other arguments default as
5135 for successive uses of @code{x}.
5137 @cindex @code{$_}, @code{$__}, and value history
5138 The addresses and contents printed by the @code{x} command are not saved
5139 in the value history because there is often too much of them and they
5140 would get in the way. Instead, @value{GDBN} makes these values available for
5141 subsequent use in expressions as values of the convenience variables
5142 @code{$_} and @code{$__}. After an @code{x} command, the last address
5143 examined is available for use in expressions in the convenience variable
5144 @code{$_}. The contents of that address, as examined, are available in
5145 the convenience variable @code{$__}.
5147 If the @code{x} command has a repeat count, the address and contents saved
5148 are from the last memory unit printed; this is not the same as the last
5149 address printed if several units were printed on the last line of output.
5152 @section Automatic display
5153 @cindex automatic display
5154 @cindex display of expressions
5156 If you find that you want to print the value of an expression frequently
5157 (to see how it changes), you might want to add it to the @dfn{automatic
5158 display list} so that @value{GDBN} prints its value each time your program stops.
5159 Each expression added to the list is given a number to identify it;
5160 to remove an expression from the list, you specify that number.
5161 The automatic display looks like this:
5165 3: bar[5] = (struct hack *) 0x3804
5169 This display shows item numbers, expressions and their current values. As with
5170 displays you request manually using @code{x} or @code{print}, you can
5171 specify the output format you prefer; in fact, @code{display} decides
5172 whether to use @code{print} or @code{x} depending on how elaborate your
5173 format specification is---it uses @code{x} if you specify a unit size,
5174 or one of the two formats (@samp{i} and @samp{s}) that are only
5175 supported by @code{x}; otherwise it uses @code{print}.
5179 @item display @var{expr}
5180 Add the expression @var{expr} to the list of expressions to display
5181 each time your program stops. @xref{Expressions, ,Expressions}.
5183 @code{display} does not repeat if you press @key{RET} again after using it.
5185 @item display/@var{fmt} @var{expr}
5186 For @var{fmt} specifying only a display format and not a size or
5187 count, add the expression @var{expr} to the auto-display list but
5188 arrange to display it each time in the specified format @var{fmt}.
5189 @xref{Output Formats,,Output formats}.
5191 @item display/@var{fmt} @var{addr}
5192 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5193 number of units, add the expression @var{addr} as a memory address to
5194 be examined each time your program stops. Examining means in effect
5195 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5198 For example, @samp{display/i $pc} can be helpful, to see the machine
5199 instruction about to be executed each time execution stops (@samp{$pc}
5200 is a common name for the program counter; @pxref{Registers, ,Registers}).
5203 @kindex delete display
5205 @item undisplay @var{dnums}@dots{}
5206 @itemx delete display @var{dnums}@dots{}
5207 Remove item numbers @var{dnums} from the list of expressions to display.
5209 @code{undisplay} does not repeat if you press @key{RET} after using it.
5210 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5212 @kindex disable display
5213 @item disable display @var{dnums}@dots{}
5214 Disable the display of item numbers @var{dnums}. A disabled display
5215 item is not printed automatically, but is not forgotten. It may be
5216 enabled again later.
5218 @kindex enable display
5219 @item enable display @var{dnums}@dots{}
5220 Enable display of item numbers @var{dnums}. It becomes effective once
5221 again in auto display of its expression, until you specify otherwise.
5224 Display the current values of the expressions on the list, just as is
5225 done when your program stops.
5227 @kindex info display
5229 Print the list of expressions previously set up to display
5230 automatically, each one with its item number, but without showing the
5231 values. This includes disabled expressions, which are marked as such.
5232 It also includes expressions which would not be displayed right now
5233 because they refer to automatic variables not currently available.
5236 If a display expression refers to local variables, then it does not make
5237 sense outside the lexical context for which it was set up. Such an
5238 expression is disabled when execution enters a context where one of its
5239 variables is not defined. For example, if you give the command
5240 @code{display last_char} while inside a function with an argument
5241 @code{last_char}, @value{GDBN} displays this argument while your program
5242 continues to stop inside that function. When it stops elsewhere---where
5243 there is no variable @code{last_char}---the display is disabled
5244 automatically. The next time your program stops where @code{last_char}
5245 is meaningful, you can enable the display expression once again.
5247 @node Print Settings
5248 @section Print settings
5250 @cindex format options
5251 @cindex print settings
5252 @value{GDBN} provides the following ways to control how arrays, structures,
5253 and symbols are printed.
5256 These settings are useful for debugging programs in any language:
5259 @kindex set print address
5260 @item set print address
5261 @itemx set print address on
5262 @value{GDBN} prints memory addresses showing the location of stack
5263 traces, structure values, pointer values, breakpoints, and so forth,
5264 even when it also displays the contents of those addresses. The default
5265 is @code{on}. For example, this is what a stack frame display looks like with
5266 @code{set print address on}:
5271 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
5273 530 if (lquote != def_lquote)
5277 @item set print address off
5278 Do not print addresses when displaying their contents. For example,
5279 this is the same stack frame displayed with @code{set print address off}:
5283 (@value{GDBP}) set print addr off
5285 #0 set_quotes (lq="<<", rq=">>") at input.c:530
5286 530 if (lquote != def_lquote)
5290 You can use @samp{set print address off} to eliminate all machine
5291 dependent displays from the @value{GDBN} interface. For example, with
5292 @code{print address off}, you should get the same text for backtraces on
5293 all machines---whether or not they involve pointer arguments.
5295 @kindex show print address
5296 @item show print address
5297 Show whether or not addresses are to be printed.
5300 When @value{GDBN} prints a symbolic address, it normally prints the
5301 closest earlier symbol plus an offset. If that symbol does not uniquely
5302 identify the address (for example, it is a name whose scope is a single
5303 source file), you may need to clarify. One way to do this is with
5304 @code{info line}, for example @samp{info line *0x4537}. Alternately,
5305 you can set @value{GDBN} to print the source file and line number when
5306 it prints a symbolic address:
5309 @kindex set print symbol-filename
5310 @item set print symbol-filename on
5311 Tell @value{GDBN} to print the source file name and line number of a
5312 symbol in the symbolic form of an address.
5314 @item set print symbol-filename off
5315 Do not print source file name and line number of a symbol. This is the
5318 @kindex show print symbol-filename
5319 @item show print symbol-filename
5320 Show whether or not @value{GDBN} will print the source file name and
5321 line number of a symbol in the symbolic form of an address.
5324 Another situation where it is helpful to show symbol filenames and line
5325 numbers is when disassembling code; @value{GDBN} shows you the line
5326 number and source file that corresponds to each instruction.
5328 Also, you may wish to see the symbolic form only if the address being
5329 printed is reasonably close to the closest earlier symbol:
5332 @kindex set print max-symbolic-offset
5333 @item set print max-symbolic-offset @var{max-offset}
5334 Tell @value{GDBN} to only display the symbolic form of an address if the
5335 offset between the closest earlier symbol and the address is less than
5336 @var{max-offset}. The default is 0, which tells @value{GDBN}
5337 to always print the symbolic form of an address if any symbol precedes it.
5339 @kindex show print max-symbolic-offset
5340 @item show print max-symbolic-offset
5341 Ask how large the maximum offset is that @value{GDBN} prints in a
5345 @cindex wild pointer, interpreting
5346 @cindex pointer, finding referent
5347 If you have a pointer and you are not sure where it points, try
5348 @samp{set print symbol-filename on}. Then you can determine the name
5349 and source file location of the variable where it points, using
5350 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
5351 For example, here @value{GDBN} shows that a variable @code{ptt} points
5352 at another variable @code{t}, defined in @file{hi2.c}:
5355 (@value{GDBP}) set print symbol-filename on
5356 (@value{GDBP}) p/a ptt
5357 $4 = 0xe008 <t in hi2.c>
5361 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
5362 does not show the symbol name and filename of the referent, even with
5363 the appropriate @code{set print} options turned on.
5366 Other settings control how different kinds of objects are printed:
5369 @kindex set print array
5370 @item set print array
5371 @itemx set print array on
5372 Pretty print arrays. This format is more convenient to read,
5373 but uses more space. The default is off.
5375 @item set print array off
5376 Return to compressed format for arrays.
5378 @kindex show print array
5379 @item show print array
5380 Show whether compressed or pretty format is selected for displaying
5383 @kindex set print elements
5384 @item set print elements @var{number-of-elements}
5385 Set a limit on how many elements of an array @value{GDBN} will print.
5386 If @value{GDBN} is printing a large array, it stops printing after it has
5387 printed the number of elements set by the @code{set print elements} command.
5388 This limit also applies to the display of strings.
5389 When @value{GDBN} starts, this limit is set to 200.
5390 Setting @var{number-of-elements} to zero means that the printing is unlimited.
5392 @kindex show print elements
5393 @item show print elements
5394 Display the number of elements of a large array that @value{GDBN} will print.
5395 If the number is 0, then the printing is unlimited.
5397 @kindex set print null-stop
5398 @item set print null-stop
5399 Cause @value{GDBN} to stop printing the characters of an array when the first
5400 @sc{null} is encountered. This is useful when large arrays actually
5401 contain only short strings.
5404 @kindex set print pretty
5405 @item set print pretty on
5406 Cause @value{GDBN} to print structures in an indented format with one member
5407 per line, like this:
5422 @item set print pretty off
5423 Cause @value{GDBN} to print structures in a compact format, like this:
5427 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
5428 meat = 0x54 "Pork"@}
5433 This is the default format.
5435 @kindex show print pretty
5436 @item show print pretty
5437 Show which format @value{GDBN} is using to print structures.
5439 @kindex set print sevenbit-strings
5440 @item set print sevenbit-strings on
5441 Print using only seven-bit characters; if this option is set,
5442 @value{GDBN} displays any eight-bit characters (in strings or
5443 character values) using the notation @code{\}@var{nnn}. This setting is
5444 best if you are working in English (@sc{ascii}) and you use the
5445 high-order bit of characters as a marker or ``meta'' bit.
5447 @item set print sevenbit-strings off
5448 Print full eight-bit characters. This allows the use of more
5449 international character sets, and is the default.
5451 @kindex show print sevenbit-strings
5452 @item show print sevenbit-strings
5453 Show whether or not @value{GDBN} is printing only seven-bit characters.
5455 @kindex set print union
5456 @item set print union on
5457 Tell @value{GDBN} to print unions which are contained in structures. This
5458 is the default setting.
5460 @item set print union off
5461 Tell @value{GDBN} not to print unions which are contained in structures.
5463 @kindex show print union
5464 @item show print union
5465 Ask @value{GDBN} whether or not it will print unions which are contained in
5468 For example, given the declarations
5471 typedef enum @{Tree, Bug@} Species;
5472 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
5473 typedef enum @{Caterpillar, Cocoon, Butterfly@}
5484 struct thing foo = @{Tree, @{Acorn@}@};
5488 with @code{set print union on} in effect @samp{p foo} would print
5491 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
5495 and with @code{set print union off} in effect it would print
5498 $1 = @{it = Tree, form = @{...@}@}
5504 These settings are of interest when debugging C@t{++} programs:
5508 @kindex set print demangle
5509 @item set print demangle
5510 @itemx set print demangle on
5511 Print C@t{++} names in their source form rather than in the encoded
5512 (``mangled'') form passed to the assembler and linker for type-safe
5513 linkage. The default is on.
5515 @kindex show print demangle
5516 @item show print demangle
5517 Show whether C@t{++} names are printed in mangled or demangled form.
5519 @kindex set print asm-demangle
5520 @item set print asm-demangle
5521 @itemx set print asm-demangle on
5522 Print C@t{++} names in their source form rather than their mangled form, even
5523 in assembler code printouts such as instruction disassemblies.
5526 @kindex show print asm-demangle
5527 @item show print asm-demangle
5528 Show whether C@t{++} names in assembly listings are printed in mangled
5531 @kindex set demangle-style
5532 @cindex C@t{++} symbol decoding style
5533 @cindex symbol decoding style, C@t{++}
5534 @item set demangle-style @var{style}
5535 Choose among several encoding schemes used by different compilers to
5536 represent C@t{++} names. The choices for @var{style} are currently:
5540 Allow @value{GDBN} to choose a decoding style by inspecting your program.
5543 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
5544 This is the default.
5547 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
5550 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
5553 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
5554 @strong{Warning:} this setting alone is not sufficient to allow
5555 debugging @code{cfront}-generated executables. @value{GDBN} would
5556 require further enhancement to permit that.
5559 If you omit @var{style}, you will see a list of possible formats.
5561 @kindex show demangle-style
5562 @item show demangle-style
5563 Display the encoding style currently in use for decoding C@t{++} symbols.
5565 @kindex set print object
5566 @item set print object
5567 @itemx set print object on
5568 When displaying a pointer to an object, identify the @emph{actual}
5569 (derived) type of the object rather than the @emph{declared} type, using
5570 the virtual function table.
5572 @item set print object off
5573 Display only the declared type of objects, without reference to the
5574 virtual function table. This is the default setting.
5576 @kindex show print object
5577 @item show print object
5578 Show whether actual, or declared, object types are displayed.
5580 @kindex set print static-members
5581 @item set print static-members
5582 @itemx set print static-members on
5583 Print static members when displaying a C@t{++} object. The default is on.
5585 @item set print static-members off
5586 Do not print static members when displaying a C@t{++} object.
5588 @kindex show print static-members
5589 @item show print static-members
5590 Show whether C@t{++} static members are printed, or not.
5592 @c These don't work with HP ANSI C++ yet.
5593 @kindex set print vtbl
5594 @item set print vtbl
5595 @itemx set print vtbl on
5596 Pretty print C@t{++} virtual function tables. The default is off.
5597 (The @code{vtbl} commands do not work on programs compiled with the HP
5598 ANSI C@t{++} compiler (@code{aCC}).)
5600 @item set print vtbl off
5601 Do not pretty print C@t{++} virtual function tables.
5603 @kindex show print vtbl
5604 @item show print vtbl
5605 Show whether C@t{++} virtual function tables are pretty printed, or not.
5609 @section Value history
5611 @cindex value history
5612 Values printed by the @code{print} command are saved in the @value{GDBN}
5613 @dfn{value history}. This allows you to refer to them in other expressions.
5614 Values are kept until the symbol table is re-read or discarded
5615 (for example with the @code{file} or @code{symbol-file} commands).
5616 When the symbol table changes, the value history is discarded,
5617 since the values may contain pointers back to the types defined in the
5622 @cindex history number
5623 The values printed are given @dfn{history numbers} by which you can
5624 refer to them. These are successive integers starting with one.
5625 @code{print} shows you the history number assigned to a value by
5626 printing @samp{$@var{num} = } before the value; here @var{num} is the
5629 To refer to any previous value, use @samp{$} followed by the value's
5630 history number. The way @code{print} labels its output is designed to
5631 remind you of this. Just @code{$} refers to the most recent value in
5632 the history, and @code{$$} refers to the value before that.
5633 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
5634 is the value just prior to @code{$$}, @code{$$1} is equivalent to
5635 @code{$$}, and @code{$$0} is equivalent to @code{$}.
5637 For example, suppose you have just printed a pointer to a structure and
5638 want to see the contents of the structure. It suffices to type
5644 If you have a chain of structures where the component @code{next} points
5645 to the next one, you can print the contents of the next one with this:
5652 You can print successive links in the chain by repeating this
5653 command---which you can do by just typing @key{RET}.
5655 Note that the history records values, not expressions. If the value of
5656 @code{x} is 4 and you type these commands:
5664 then the value recorded in the value history by the @code{print} command
5665 remains 4 even though the value of @code{x} has changed.
5670 Print the last ten values in the value history, with their item numbers.
5671 This is like @samp{p@ $$9} repeated ten times, except that @code{show
5672 values} does not change the history.
5674 @item show values @var{n}
5675 Print ten history values centered on history item number @var{n}.
5678 Print ten history values just after the values last printed. If no more
5679 values are available, @code{show values +} produces no display.
5682 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
5683 same effect as @samp{show values +}.
5685 @node Convenience Vars
5686 @section Convenience variables
5688 @cindex convenience variables
5689 @value{GDBN} provides @dfn{convenience variables} that you can use within
5690 @value{GDBN} to hold on to a value and refer to it later. These variables
5691 exist entirely within @value{GDBN}; they are not part of your program, and
5692 setting a convenience variable has no direct effect on further execution
5693 of your program. That is why you can use them freely.
5695 Convenience variables are prefixed with @samp{$}. Any name preceded by
5696 @samp{$} can be used for a convenience variable, unless it is one of
5697 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
5698 (Value history references, in contrast, are @emph{numbers} preceded
5699 by @samp{$}. @xref{Value History, ,Value history}.)
5701 You can save a value in a convenience variable with an assignment
5702 expression, just as you would set a variable in your program.
5706 set $foo = *object_ptr
5710 would save in @code{$foo} the value contained in the object pointed to by
5713 Using a convenience variable for the first time creates it, but its
5714 value is @code{void} until you assign a new value. You can alter the
5715 value with another assignment at any time.
5717 Convenience variables have no fixed types. You can assign a convenience
5718 variable any type of value, including structures and arrays, even if
5719 that variable already has a value of a different type. The convenience
5720 variable, when used as an expression, has the type of its current value.
5723 @kindex show convenience
5724 @item show convenience
5725 Print a list of convenience variables used so far, and their values.
5726 Abbreviated @code{show conv}.
5729 One of the ways to use a convenience variable is as a counter to be
5730 incremented or a pointer to be advanced. For example, to print
5731 a field from successive elements of an array of structures:
5735 print bar[$i++]->contents
5739 Repeat that command by typing @key{RET}.
5741 Some convenience variables are created automatically by @value{GDBN} and given
5742 values likely to be useful.
5745 @vindex $_@r{, convenience variable}
5747 The variable @code{$_} is automatically set by the @code{x} command to
5748 the last address examined (@pxref{Memory, ,Examining memory}). Other
5749 commands which provide a default address for @code{x} to examine also
5750 set @code{$_} to that address; these commands include @code{info line}
5751 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
5752 except when set by the @code{x} command, in which case it is a pointer
5753 to the type of @code{$__}.
5755 @vindex $__@r{, convenience variable}
5757 The variable @code{$__} is automatically set by the @code{x} command
5758 to the value found in the last address examined. Its type is chosen
5759 to match the format in which the data was printed.
5762 @vindex $_exitcode@r{, convenience variable}
5763 The variable @code{$_exitcode} is automatically set to the exit code when
5764 the program being debugged terminates.
5767 On HP-UX systems, if you refer to a function or variable name that
5768 begins with a dollar sign, @value{GDBN} searches for a user or system
5769 name first, before it searches for a convenience variable.
5775 You can refer to machine register contents, in expressions, as variables
5776 with names starting with @samp{$}. The names of registers are different
5777 for each machine; use @code{info registers} to see the names used on
5781 @kindex info registers
5782 @item info registers
5783 Print the names and values of all registers except floating-point
5784 and vector registers (in the selected stack frame).
5786 @kindex info all-registers
5787 @cindex floating point registers
5788 @item info all-registers
5789 Print the names and values of all registers, including floating-point
5790 and vector registers (in the selected stack frame).
5792 @item info registers @var{regname} @dots{}
5793 Print the @dfn{relativized} value of each specified register @var{regname}.
5794 As discussed in detail below, register values are normally relative to
5795 the selected stack frame. @var{regname} may be any register name valid on
5796 the machine you are using, with or without the initial @samp{$}.
5799 @value{GDBN} has four ``standard'' register names that are available (in
5800 expressions) on most machines---whenever they do not conflict with an
5801 architecture's canonical mnemonics for registers. The register names
5802 @code{$pc} and @code{$sp} are used for the program counter register and
5803 the stack pointer. @code{$fp} is used for a register that contains a
5804 pointer to the current stack frame, and @code{$ps} is used for a
5805 register that contains the processor status. For example,
5806 you could print the program counter in hex with
5813 or print the instruction to be executed next with
5820 or add four to the stack pointer@footnote{This is a way of removing
5821 one word from the stack, on machines where stacks grow downward in
5822 memory (most machines, nowadays). This assumes that the innermost
5823 stack frame is selected; setting @code{$sp} is not allowed when other
5824 stack frames are selected. To pop entire frames off the stack,
5825 regardless of machine architecture, use @code{return};
5826 see @ref{Returning, ,Returning from a function}.} with
5832 Whenever possible, these four standard register names are available on
5833 your machine even though the machine has different canonical mnemonics,
5834 so long as there is no conflict. The @code{info registers} command
5835 shows the canonical names. For example, on the SPARC, @code{info
5836 registers} displays the processor status register as @code{$psr} but you
5837 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
5838 is an alias for the @sc{eflags} register.
5840 @value{GDBN} always considers the contents of an ordinary register as an
5841 integer when the register is examined in this way. Some machines have
5842 special registers which can hold nothing but floating point; these
5843 registers are considered to have floating point values. There is no way
5844 to refer to the contents of an ordinary register as floating point value
5845 (although you can @emph{print} it as a floating point value with
5846 @samp{print/f $@var{regname}}).
5848 Some registers have distinct ``raw'' and ``virtual'' data formats. This
5849 means that the data format in which the register contents are saved by
5850 the operating system is not the same one that your program normally
5851 sees. For example, the registers of the 68881 floating point
5852 coprocessor are always saved in ``extended'' (raw) format, but all C
5853 programs expect to work with ``double'' (virtual) format. In such
5854 cases, @value{GDBN} normally works with the virtual format only (the format
5855 that makes sense for your program), but the @code{info registers} command
5856 prints the data in both formats.
5858 Normally, register values are relative to the selected stack frame
5859 (@pxref{Selection, ,Selecting a frame}). This means that you get the
5860 value that the register would contain if all stack frames farther in
5861 were exited and their saved registers restored. In order to see the
5862 true contents of hardware registers, you must select the innermost
5863 frame (with @samp{frame 0}).
5865 However, @value{GDBN} must deduce where registers are saved, from the machine
5866 code generated by your compiler. If some registers are not saved, or if
5867 @value{GDBN} is unable to locate the saved registers, the selected stack
5868 frame makes no difference.
5870 @node Floating Point Hardware
5871 @section Floating point hardware
5872 @cindex floating point
5874 Depending on the configuration, @value{GDBN} may be able to give
5875 you more information about the status of the floating point hardware.
5880 Display hardware-dependent information about the floating
5881 point unit. The exact contents and layout vary depending on the
5882 floating point chip. Currently, @samp{info float} is supported on
5883 the ARM and x86 machines.
5887 @section Vector Unit
5890 Depending on the configuration, @value{GDBN} may be able to give you
5891 more information about the status of the vector unit.
5896 Display information about the vector unit. The exact contents and
5897 layout vary depending on the hardware.
5900 @node Auxiliary Vector
5901 @section Operating system auxiliary vector
5902 @cindex auxiliary vector
5903 @cindex vector, auxiliary
5905 Some operating systems supply an @dfn{auxiliary vector} to programs at
5906 startup. This is akin to the arguments and environment that you
5907 specify for a program, but contains a system-dependent variety of
5908 binary values that tell system libraries important details about the
5909 hardware, operating system, and process. Each value's purpose is
5910 identified by an integer tag; the meanings are well-known but system-specific.
5911 Depending on the configuration and operating system facilities,
5912 @value{GDBN} may be able to show you this information.
5917 Display the auxiliary vector of the inferior, which can be either a
5918 live process or a core dump file. @value{GDBN} prints each tag value
5919 numerically, and also shows names and text descriptions for recognized
5920 tags. Some values in the vector are numbers, some bit masks, and some
5921 pointers to strings or other data. @value{GDBN} displays each value in the
5922 most appropriate form for a recognized tag, and in hexadecimal for
5923 an unrecognized tag.
5926 @node Memory Region Attributes
5927 @section Memory region attributes
5928 @cindex memory region attributes
5930 @dfn{Memory region attributes} allow you to describe special handling
5931 required by regions of your target's memory. @value{GDBN} uses attributes
5932 to determine whether to allow certain types of memory accesses; whether to
5933 use specific width accesses; and whether to cache target memory.
5935 Defined memory regions can be individually enabled and disabled. When a
5936 memory region is disabled, @value{GDBN} uses the default attributes when
5937 accessing memory in that region. Similarly, if no memory regions have
5938 been defined, @value{GDBN} uses the default attributes when accessing
5941 When a memory region is defined, it is given a number to identify it;
5942 to enable, disable, or remove a memory region, you specify that number.
5946 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
5947 Define memory region bounded by @var{lower} and @var{upper} with
5948 attributes @var{attributes}@dots{}. Note that @var{upper} == 0 is a
5949 special case: it is treated as the the target's maximum memory address.
5950 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
5953 @item delete mem @var{nums}@dots{}
5954 Remove memory regions @var{nums}@dots{}.
5957 @item disable mem @var{nums}@dots{}
5958 Disable memory regions @var{nums}@dots{}.
5959 A disabled memory region is not forgotten.
5960 It may be enabled again later.
5963 @item enable mem @var{nums}@dots{}
5964 Enable memory regions @var{nums}@dots{}.
5968 Print a table of all defined memory regions, with the following columns
5972 @item Memory Region Number
5973 @item Enabled or Disabled.
5974 Enabled memory regions are marked with @samp{y}.
5975 Disabled memory regions are marked with @samp{n}.
5978 The address defining the inclusive lower bound of the memory region.
5981 The address defining the exclusive upper bound of the memory region.
5984 The list of attributes set for this memory region.
5989 @subsection Attributes
5991 @subsubsection Memory Access Mode
5992 The access mode attributes set whether @value{GDBN} may make read or
5993 write accesses to a memory region.
5995 While these attributes prevent @value{GDBN} from performing invalid
5996 memory accesses, they do nothing to prevent the target system, I/O DMA,
5997 etc. from accessing memory.
6001 Memory is read only.
6003 Memory is write only.
6005 Memory is read/write. This is the default.
6008 @subsubsection Memory Access Size
6009 The acccess size attributes tells @value{GDBN} to use specific sized
6010 accesses in the memory region. Often memory mapped device registers
6011 require specific sized accesses. If no access size attribute is
6012 specified, @value{GDBN} may use accesses of any size.
6016 Use 8 bit memory accesses.
6018 Use 16 bit memory accesses.
6020 Use 32 bit memory accesses.
6022 Use 64 bit memory accesses.
6025 @c @subsubsection Hardware/Software Breakpoints
6026 @c The hardware/software breakpoint attributes set whether @value{GDBN}
6027 @c will use hardware or software breakpoints for the internal breakpoints
6028 @c used by the step, next, finish, until, etc. commands.
6032 @c Always use hardware breakpoints
6033 @c @item swbreak (default)
6036 @subsubsection Data Cache
6037 The data cache attributes set whether @value{GDBN} will cache target
6038 memory. While this generally improves performance by reducing debug
6039 protocol overhead, it can lead to incorrect results because @value{GDBN}
6040 does not know about volatile variables or memory mapped device
6045 Enable @value{GDBN} to cache target memory.
6047 Disable @value{GDBN} from caching target memory. This is the default.
6050 @c @subsubsection Memory Write Verification
6051 @c The memory write verification attributes set whether @value{GDBN}
6052 @c will re-reads data after each write to verify the write was successful.
6056 @c @item noverify (default)
6059 @node Dump/Restore Files
6060 @section Copy between memory and a file
6061 @cindex dump/restore files
6062 @cindex append data to a file
6063 @cindex dump data to a file
6064 @cindex restore data from a file
6066 You can use the commands @code{dump}, @code{append}, and
6067 @code{restore} to copy data between target memory and a file. The
6068 @code{dump} and @code{append} commands write data to a file, and the
6069 @code{restore} command reads data from a file back into the inferior's
6070 memory. Files may be in binary, Motorola S-record, Intel hex, or
6071 Tektronix Hex format; however, @value{GDBN} can only append to binary
6077 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6078 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
6079 Dump the contents of memory from @var{start_addr} to @var{end_addr},
6080 or the value of @var{expr}, to @var{filename} in the given format.
6082 The @var{format} parameter may be any one of:
6089 Motorola S-record format.
6091 Tektronix Hex format.
6094 @value{GDBN} uses the same definitions of these formats as the
6095 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
6096 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
6100 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6101 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
6102 Append the contents of memory from @var{start_addr} to @var{end_addr},
6103 or the value of @var{expr}, to @var{filename}, in raw binary form.
6104 (@value{GDBN} can only append data to files in raw binary form.)
6107 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
6108 Restore the contents of file @var{filename} into memory. The
6109 @code{restore} command can automatically recognize any known @sc{bfd}
6110 file format, except for raw binary. To restore a raw binary file you
6111 must specify the optional keyword @code{binary} after the filename.
6113 If @var{bias} is non-zero, its value will be added to the addresses
6114 contained in the file. Binary files always start at address zero, so
6115 they will be restored at address @var{bias}. Other bfd files have
6116 a built-in location; they will be restored at offset @var{bias}
6119 If @var{start} and/or @var{end} are non-zero, then only data between
6120 file offset @var{start} and file offset @var{end} will be restored.
6121 These offsets are relative to the addresses in the file, before
6122 the @var{bias} argument is applied.
6126 @node Character Sets
6127 @section Character Sets
6128 @cindex character sets
6130 @cindex translating between character sets
6131 @cindex host character set
6132 @cindex target character set
6134 If the program you are debugging uses a different character set to
6135 represent characters and strings than the one @value{GDBN} uses itself,
6136 @value{GDBN} can automatically translate between the character sets for
6137 you. The character set @value{GDBN} uses we call the @dfn{host
6138 character set}; the one the inferior program uses we call the
6139 @dfn{target character set}.
6141 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
6142 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
6143 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
6144 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
6145 then the host character set is Latin-1, and the target character set is
6146 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
6147 target-charset EBCDIC-US}, then @value{GDBN} translates between
6148 @sc{ebcdic} and Latin 1 as you print character or string values, or use
6149 character and string literals in expressions.
6151 @value{GDBN} has no way to automatically recognize which character set
6152 the inferior program uses; you must tell it, using the @code{set
6153 target-charset} command, described below.
6155 Here are the commands for controlling @value{GDBN}'s character set
6159 @item set target-charset @var{charset}
6160 @kindex set target-charset
6161 Set the current target character set to @var{charset}. We list the
6162 character set names @value{GDBN} recognizes below, but if you type
6163 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6164 list the target character sets it supports.
6168 @item set host-charset @var{charset}
6169 @kindex set host-charset
6170 Set the current host character set to @var{charset}.
6172 By default, @value{GDBN} uses a host character set appropriate to the
6173 system it is running on; you can override that default using the
6174 @code{set host-charset} command.
6176 @value{GDBN} can only use certain character sets as its host character
6177 set. We list the character set names @value{GDBN} recognizes below, and
6178 indicate which can be host character sets, but if you type
6179 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6180 list the host character sets it supports.
6182 @item set charset @var{charset}
6184 Set the current host and target character sets to @var{charset}. As
6185 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
6186 @value{GDBN} will list the name of the character sets that can be used
6187 for both host and target.
6191 @kindex show charset
6192 Show the names of the current host and target charsets.
6194 @itemx show host-charset
6195 @kindex show host-charset
6196 Show the name of the current host charset.
6198 @itemx show target-charset
6199 @kindex show target-charset
6200 Show the name of the current target charset.
6204 @value{GDBN} currently includes support for the following character
6210 @cindex ASCII character set
6211 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
6215 @cindex ISO 8859-1 character set
6216 @cindex ISO Latin 1 character set
6217 The ISO Latin 1 character set. This extends @sc{ascii} with accented
6218 characters needed for French, German, and Spanish. @value{GDBN} can use
6219 this as its host character set.
6223 @cindex EBCDIC character set
6224 @cindex IBM1047 character set
6225 Variants of the @sc{ebcdic} character set, used on some of IBM's
6226 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
6227 @value{GDBN} cannot use these as its host character set.
6231 Note that these are all single-byte character sets. More work inside
6232 GDB is needed to support multi-byte or variable-width character
6233 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
6235 Here is an example of @value{GDBN}'s character set support in action.
6236 Assume that the following source code has been placed in the file
6237 @file{charset-test.c}:
6243 = @{72, 101, 108, 108, 111, 44, 32, 119,
6244 111, 114, 108, 100, 33, 10, 0@};
6245 char ibm1047_hello[]
6246 = @{200, 133, 147, 147, 150, 107, 64, 166,
6247 150, 153, 147, 132, 90, 37, 0@};
6251 printf ("Hello, world!\n");
6255 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
6256 containing the string @samp{Hello, world!} followed by a newline,
6257 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
6259 We compile the program, and invoke the debugger on it:
6262 $ gcc -g charset-test.c -o charset-test
6263 $ gdb -nw charset-test
6264 GNU gdb 2001-12-19-cvs
6265 Copyright 2001 Free Software Foundation, Inc.
6270 We can use the @code{show charset} command to see what character sets
6271 @value{GDBN} is currently using to interpret and display characters and
6276 The current host and target character set is `ISO-8859-1'.
6280 For the sake of printing this manual, let's use @sc{ascii} as our
6281 initial character set:
6283 (gdb) set charset ASCII
6285 The current host and target character set is `ASCII'.
6289 Let's assume that @sc{ascii} is indeed the correct character set for our
6290 host system --- in other words, let's assume that if @value{GDBN} prints
6291 characters using the @sc{ascii} character set, our terminal will display
6292 them properly. Since our current target character set is also
6293 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
6296 (gdb) print ascii_hello
6297 $1 = 0x401698 "Hello, world!\n"
6298 (gdb) print ascii_hello[0]
6303 @value{GDBN} uses the target character set for character and string
6304 literals you use in expressions:
6312 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
6315 @value{GDBN} relies on the user to tell it which character set the
6316 target program uses. If we print @code{ibm1047_hello} while our target
6317 character set is still @sc{ascii}, we get jibberish:
6320 (gdb) print ibm1047_hello
6321 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
6322 (gdb) print ibm1047_hello[0]
6327 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
6328 @value{GDBN} tells us the character sets it supports:
6331 (gdb) set target-charset
6332 ASCII EBCDIC-US IBM1047 ISO-8859-1
6333 (gdb) set target-charset
6336 We can select @sc{ibm1047} as our target character set, and examine the
6337 program's strings again. Now the @sc{ascii} string is wrong, but
6338 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
6339 target character set, @sc{ibm1047}, to the host character set,
6340 @sc{ascii}, and they display correctly:
6343 (gdb) set target-charset IBM1047
6345 The current host character set is `ASCII'.
6346 The current target character set is `IBM1047'.
6347 (gdb) print ascii_hello
6348 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
6349 (gdb) print ascii_hello[0]
6351 (gdb) print ibm1047_hello
6352 $8 = 0x4016a8 "Hello, world!\n"
6353 (gdb) print ibm1047_hello[0]
6358 As above, @value{GDBN} uses the target character set for character and
6359 string literals you use in expressions:
6367 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
6372 @chapter C Preprocessor Macros
6374 Some languages, such as C and C@t{++}, provide a way to define and invoke
6375 ``preprocessor macros'' which expand into strings of tokens.
6376 @value{GDBN} can evaluate expressions containing macro invocations, show
6377 the result of macro expansion, and show a macro's definition, including
6378 where it was defined.
6380 You may need to compile your program specially to provide @value{GDBN}
6381 with information about preprocessor macros. Most compilers do not
6382 include macros in their debugging information, even when you compile
6383 with the @option{-g} flag. @xref{Compilation}.
6385 A program may define a macro at one point, remove that definition later,
6386 and then provide a different definition after that. Thus, at different
6387 points in the program, a macro may have different definitions, or have
6388 no definition at all. If there is a current stack frame, @value{GDBN}
6389 uses the macros in scope at that frame's source code line. Otherwise,
6390 @value{GDBN} uses the macros in scope at the current listing location;
6393 At the moment, @value{GDBN} does not support the @code{##}
6394 token-splicing operator, the @code{#} stringification operator, or
6395 variable-arity macros.
6397 Whenever @value{GDBN} evaluates an expression, it always expands any
6398 macro invocations present in the expression. @value{GDBN} also provides
6399 the following commands for working with macros explicitly.
6403 @kindex macro expand
6404 @cindex macro expansion, showing the results of preprocessor
6405 @cindex preprocessor macro expansion, showing the results of
6406 @cindex expanding preprocessor macros
6407 @item macro expand @var{expression}
6408 @itemx macro exp @var{expression}
6409 Show the results of expanding all preprocessor macro invocations in
6410 @var{expression}. Since @value{GDBN} simply expands macros, but does
6411 not parse the result, @var{expression} need not be a valid expression;
6412 it can be any string of tokens.
6414 @kindex macro expand-once
6415 @item macro expand-once @var{expression}
6416 @itemx macro exp1 @var{expression}
6417 @i{(This command is not yet implemented.)} Show the results of
6418 expanding those preprocessor macro invocations that appear explicitly in
6419 @var{expression}. Macro invocations appearing in that expansion are
6420 left unchanged. This command allows you to see the effect of a
6421 particular macro more clearly, without being confused by further
6422 expansions. Since @value{GDBN} simply expands macros, but does not
6423 parse the result, @var{expression} need not be a valid expression; it
6424 can be any string of tokens.
6427 @cindex macro definition, showing
6428 @cindex definition, showing a macro's
6429 @item info macro @var{macro}
6430 Show the definition of the macro named @var{macro}, and describe the
6431 source location where that definition was established.
6433 @kindex macro define
6434 @cindex user-defined macros
6435 @cindex defining macros interactively
6436 @cindex macros, user-defined
6437 @item macro define @var{macro} @var{replacement-list}
6438 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
6439 @i{(This command is not yet implemented.)} Introduce a definition for a
6440 preprocessor macro named @var{macro}, invocations of which are replaced
6441 by the tokens given in @var{replacement-list}. The first form of this
6442 command defines an ``object-like'' macro, which takes no arguments; the
6443 second form defines a ``function-like'' macro, which takes the arguments
6444 given in @var{arglist}.
6446 A definition introduced by this command is in scope in every expression
6447 evaluated in @value{GDBN}, until it is removed with the @command{macro
6448 undef} command, described below. The definition overrides all
6449 definitions for @var{macro} present in the program being debugged, as
6450 well as any previous user-supplied definition.
6453 @item macro undef @var{macro}
6454 @i{(This command is not yet implemented.)} Remove any user-supplied
6455 definition for the macro named @var{macro}. This command only affects
6456 definitions provided with the @command{macro define} command, described
6457 above; it cannot remove definitions present in the program being
6462 @cindex macros, example of debugging with
6463 Here is a transcript showing the above commands in action. First, we
6464 show our source files:
6472 #define ADD(x) (M + x)
6477 printf ("Hello, world!\n");
6479 printf ("We're so creative.\n");
6481 printf ("Goodbye, world!\n");
6488 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
6489 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
6490 compiler includes information about preprocessor macros in the debugging
6494 $ gcc -gdwarf-2 -g3 sample.c -o sample
6498 Now, we start @value{GDBN} on our sample program:
6502 GNU gdb 2002-05-06-cvs
6503 Copyright 2002 Free Software Foundation, Inc.
6504 GDB is free software, @dots{}
6508 We can expand macros and examine their definitions, even when the
6509 program is not running. @value{GDBN} uses the current listing position
6510 to decide which macro definitions are in scope:
6516 5 #define ADD(x) (M + x)
6521 10 printf ("Hello, world!\n");
6523 12 printf ("We're so creative.\n");
6524 (gdb) info macro ADD
6525 Defined at /home/jimb/gdb/macros/play/sample.c:5
6526 #define ADD(x) (M + x)
6528 Defined at /home/jimb/gdb/macros/play/sample.h:1
6529 included at /home/jimb/gdb/macros/play/sample.c:2
6531 (gdb) macro expand ADD(1)
6532 expands to: (42 + 1)
6533 (gdb) macro expand-once ADD(1)
6534 expands to: once (M + 1)
6538 In the example above, note that @command{macro expand-once} expands only
6539 the macro invocation explicit in the original text --- the invocation of
6540 @code{ADD} --- but does not expand the invocation of the macro @code{M},
6541 which was introduced by @code{ADD}.
6543 Once the program is running, GDB uses the macro definitions in force at
6544 the source line of the current stack frame:
6548 Breakpoint 1 at 0x8048370: file sample.c, line 10.
6550 Starting program: /home/jimb/gdb/macros/play/sample
6552 Breakpoint 1, main () at sample.c:10
6553 10 printf ("Hello, world!\n");
6557 At line 10, the definition of the macro @code{N} at line 9 is in force:
6561 Defined at /home/jimb/gdb/macros/play/sample.c:9
6563 (gdb) macro expand N Q M
6570 As we step over directives that remove @code{N}'s definition, and then
6571 give it a new definition, @value{GDBN} finds the definition (or lack
6572 thereof) in force at each point:
6577 12 printf ("We're so creative.\n");
6579 The symbol `N' has no definition as a C/C++ preprocessor macro
6580 at /home/jimb/gdb/macros/play/sample.c:12
6583 14 printf ("Goodbye, world!\n");
6585 Defined at /home/jimb/gdb/macros/play/sample.c:13
6587 (gdb) macro expand N Q M
6588 expands to: 1729 < 42
6596 @chapter Tracepoints
6597 @c This chapter is based on the documentation written by Michael
6598 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
6601 In some applications, it is not feasible for the debugger to interrupt
6602 the program's execution long enough for the developer to learn
6603 anything helpful about its behavior. If the program's correctness
6604 depends on its real-time behavior, delays introduced by a debugger
6605 might cause the program to change its behavior drastically, or perhaps
6606 fail, even when the code itself is correct. It is useful to be able
6607 to observe the program's behavior without interrupting it.
6609 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
6610 specify locations in the program, called @dfn{tracepoints}, and
6611 arbitrary expressions to evaluate when those tracepoints are reached.
6612 Later, using the @code{tfind} command, you can examine the values
6613 those expressions had when the program hit the tracepoints. The
6614 expressions may also denote objects in memory---structures or arrays,
6615 for example---whose values @value{GDBN} should record; while visiting
6616 a particular tracepoint, you may inspect those objects as if they were
6617 in memory at that moment. However, because @value{GDBN} records these
6618 values without interacting with you, it can do so quickly and
6619 unobtrusively, hopefully not disturbing the program's behavior.
6621 The tracepoint facility is currently available only for remote
6622 targets. @xref{Targets}. In addition, your remote target must know how
6623 to collect trace data. This functionality is implemented in the remote
6624 stub; however, none of the stubs distributed with @value{GDBN} support
6625 tracepoints as of this writing.
6627 This chapter describes the tracepoint commands and features.
6631 * Analyze Collected Data::
6632 * Tracepoint Variables::
6635 @node Set Tracepoints
6636 @section Commands to Set Tracepoints
6638 Before running such a @dfn{trace experiment}, an arbitrary number of
6639 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
6640 tracepoint has a number assigned to it by @value{GDBN}. Like with
6641 breakpoints, tracepoint numbers are successive integers starting from
6642 one. Many of the commands associated with tracepoints take the
6643 tracepoint number as their argument, to identify which tracepoint to
6646 For each tracepoint, you can specify, in advance, some arbitrary set
6647 of data that you want the target to collect in the trace buffer when
6648 it hits that tracepoint. The collected data can include registers,
6649 local variables, or global data. Later, you can use @value{GDBN}
6650 commands to examine the values these data had at the time the
6653 This section describes commands to set tracepoints and associated
6654 conditions and actions.
6657 * Create and Delete Tracepoints::
6658 * Enable and Disable Tracepoints::
6659 * Tracepoint Passcounts::
6660 * Tracepoint Actions::
6661 * Listing Tracepoints::
6662 * Starting and Stopping Trace Experiment::
6665 @node Create and Delete Tracepoints
6666 @subsection Create and Delete Tracepoints
6669 @cindex set tracepoint
6672 The @code{trace} command is very similar to the @code{break} command.
6673 Its argument can be a source line, a function name, or an address in
6674 the target program. @xref{Set Breaks}. The @code{trace} command
6675 defines a tracepoint, which is a point in the target program where the
6676 debugger will briefly stop, collect some data, and then allow the
6677 program to continue. Setting a tracepoint or changing its commands
6678 doesn't take effect until the next @code{tstart} command; thus, you
6679 cannot change the tracepoint attributes once a trace experiment is
6682 Here are some examples of using the @code{trace} command:
6685 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
6687 (@value{GDBP}) @b{trace +2} // 2 lines forward
6689 (@value{GDBP}) @b{trace my_function} // first source line of function
6691 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
6693 (@value{GDBP}) @b{trace *0x2117c4} // an address
6697 You can abbreviate @code{trace} as @code{tr}.
6700 @cindex last tracepoint number
6701 @cindex recent tracepoint number
6702 @cindex tracepoint number
6703 The convenience variable @code{$tpnum} records the tracepoint number
6704 of the most recently set tracepoint.
6706 @kindex delete tracepoint
6707 @cindex tracepoint deletion
6708 @item delete tracepoint @r{[}@var{num}@r{]}
6709 Permanently delete one or more tracepoints. With no argument, the
6710 default is to delete all tracepoints.
6715 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
6717 (@value{GDBP}) @b{delete trace} // remove all tracepoints
6721 You can abbreviate this command as @code{del tr}.
6724 @node Enable and Disable Tracepoints
6725 @subsection Enable and Disable Tracepoints
6728 @kindex disable tracepoint
6729 @item disable tracepoint @r{[}@var{num}@r{]}
6730 Disable tracepoint @var{num}, or all tracepoints if no argument
6731 @var{num} is given. A disabled tracepoint will have no effect during
6732 the next trace experiment, but it is not forgotten. You can re-enable
6733 a disabled tracepoint using the @code{enable tracepoint} command.
6735 @kindex enable tracepoint
6736 @item enable tracepoint @r{[}@var{num}@r{]}
6737 Enable tracepoint @var{num}, or all tracepoints. The enabled
6738 tracepoints will become effective the next time a trace experiment is
6742 @node Tracepoint Passcounts
6743 @subsection Tracepoint Passcounts
6747 @cindex tracepoint pass count
6748 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
6749 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
6750 automatically stop a trace experiment. If a tracepoint's passcount is
6751 @var{n}, then the trace experiment will be automatically stopped on
6752 the @var{n}'th time that tracepoint is hit. If the tracepoint number
6753 @var{num} is not specified, the @code{passcount} command sets the
6754 passcount of the most recently defined tracepoint. If no passcount is
6755 given, the trace experiment will run until stopped explicitly by the
6761 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
6762 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
6764 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
6765 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
6766 (@value{GDBP}) @b{trace foo}
6767 (@value{GDBP}) @b{pass 3}
6768 (@value{GDBP}) @b{trace bar}
6769 (@value{GDBP}) @b{pass 2}
6770 (@value{GDBP}) @b{trace baz}
6771 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
6772 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
6773 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
6774 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
6778 @node Tracepoint Actions
6779 @subsection Tracepoint Action Lists
6783 @cindex tracepoint actions
6784 @item actions @r{[}@var{num}@r{]}
6785 This command will prompt for a list of actions to be taken when the
6786 tracepoint is hit. If the tracepoint number @var{num} is not
6787 specified, this command sets the actions for the one that was most
6788 recently defined (so that you can define a tracepoint and then say
6789 @code{actions} without bothering about its number). You specify the
6790 actions themselves on the following lines, one action at a time, and
6791 terminate the actions list with a line containing just @code{end}. So
6792 far, the only defined actions are @code{collect} and
6793 @code{while-stepping}.
6795 @cindex remove actions from a tracepoint
6796 To remove all actions from a tracepoint, type @samp{actions @var{num}}
6797 and follow it immediately with @samp{end}.
6800 (@value{GDBP}) @b{collect @var{data}} // collect some data
6802 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
6804 (@value{GDBP}) @b{end} // signals the end of actions.
6807 In the following example, the action list begins with @code{collect}
6808 commands indicating the things to be collected when the tracepoint is
6809 hit. Then, in order to single-step and collect additional data
6810 following the tracepoint, a @code{while-stepping} command is used,
6811 followed by the list of things to be collected while stepping. The
6812 @code{while-stepping} command is terminated by its own separate
6813 @code{end} command. Lastly, the action list is terminated by an
6817 (@value{GDBP}) @b{trace foo}
6818 (@value{GDBP}) @b{actions}
6819 Enter actions for tracepoint 1, one per line:
6828 @kindex collect @r{(tracepoints)}
6829 @item collect @var{expr1}, @var{expr2}, @dots{}
6830 Collect values of the given expressions when the tracepoint is hit.
6831 This command accepts a comma-separated list of any valid expressions.
6832 In addition to global, static, or local variables, the following
6833 special arguments are supported:
6837 collect all registers
6840 collect all function arguments
6843 collect all local variables.
6846 You can give several consecutive @code{collect} commands, each one
6847 with a single argument, or one @code{collect} command with several
6848 arguments separated by commas: the effect is the same.
6850 The command @code{info scope} (@pxref{Symbols, info scope}) is
6851 particularly useful for figuring out what data to collect.
6853 @kindex while-stepping @r{(tracepoints)}
6854 @item while-stepping @var{n}
6855 Perform @var{n} single-step traces after the tracepoint, collecting
6856 new data at each step. The @code{while-stepping} command is
6857 followed by the list of what to collect while stepping (followed by
6858 its own @code{end} command):
6862 > collect $regs, myglobal
6868 You may abbreviate @code{while-stepping} as @code{ws} or
6872 @node Listing Tracepoints
6873 @subsection Listing Tracepoints
6876 @kindex info tracepoints
6877 @cindex information about tracepoints
6878 @item info tracepoints @r{[}@var{num}@r{]}
6879 Display information about the tracepoint @var{num}. If you don't specify
6880 a tracepoint number, displays information about all the tracepoints
6881 defined so far. For each tracepoint, the following information is
6888 whether it is enabled or disabled
6892 its passcount as given by the @code{passcount @var{n}} command
6894 its step count as given by the @code{while-stepping @var{n}} command
6896 where in the source files is the tracepoint set
6898 its action list as given by the @code{actions} command
6902 (@value{GDBP}) @b{info trace}
6903 Num Enb Address PassC StepC What
6904 1 y 0x002117c4 0 0 <gdb_asm>
6905 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
6906 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
6911 This command can be abbreviated @code{info tp}.
6914 @node Starting and Stopping Trace Experiment
6915 @subsection Starting and Stopping Trace Experiment
6919 @cindex start a new trace experiment
6920 @cindex collected data discarded
6922 This command takes no arguments. It starts the trace experiment, and
6923 begins collecting data. This has the side effect of discarding all
6924 the data collected in the trace buffer during the previous trace
6928 @cindex stop a running trace experiment
6930 This command takes no arguments. It ends the trace experiment, and
6931 stops collecting data.
6933 @strong{Note:} a trace experiment and data collection may stop
6934 automatically if any tracepoint's passcount is reached
6935 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
6938 @cindex status of trace data collection
6939 @cindex trace experiment, status of
6941 This command displays the status of the current trace data
6945 Here is an example of the commands we described so far:
6948 (@value{GDBP}) @b{trace gdb_c_test}
6949 (@value{GDBP}) @b{actions}
6950 Enter actions for tracepoint #1, one per line.
6951 > collect $regs,$locals,$args
6956 (@value{GDBP}) @b{tstart}
6957 [time passes @dots{}]
6958 (@value{GDBP}) @b{tstop}
6962 @node Analyze Collected Data
6963 @section Using the collected data
6965 After the tracepoint experiment ends, you use @value{GDBN} commands
6966 for examining the trace data. The basic idea is that each tracepoint
6967 collects a trace @dfn{snapshot} every time it is hit and another
6968 snapshot every time it single-steps. All these snapshots are
6969 consecutively numbered from zero and go into a buffer, and you can
6970 examine them later. The way you examine them is to @dfn{focus} on a
6971 specific trace snapshot. When the remote stub is focused on a trace
6972 snapshot, it will respond to all @value{GDBN} requests for memory and
6973 registers by reading from the buffer which belongs to that snapshot,
6974 rather than from @emph{real} memory or registers of the program being
6975 debugged. This means that @strong{all} @value{GDBN} commands
6976 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
6977 behave as if we were currently debugging the program state as it was
6978 when the tracepoint occurred. Any requests for data that are not in
6979 the buffer will fail.
6982 * tfind:: How to select a trace snapshot
6983 * tdump:: How to display all data for a snapshot
6984 * save-tracepoints:: How to save tracepoints for a future run
6988 @subsection @code{tfind @var{n}}
6991 @cindex select trace snapshot
6992 @cindex find trace snapshot
6993 The basic command for selecting a trace snapshot from the buffer is
6994 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
6995 counting from zero. If no argument @var{n} is given, the next
6996 snapshot is selected.
6998 Here are the various forms of using the @code{tfind} command.
7002 Find the first snapshot in the buffer. This is a synonym for
7003 @code{tfind 0} (since 0 is the number of the first snapshot).
7006 Stop debugging trace snapshots, resume @emph{live} debugging.
7009 Same as @samp{tfind none}.
7012 No argument means find the next trace snapshot.
7015 Find the previous trace snapshot before the current one. This permits
7016 retracing earlier steps.
7018 @item tfind tracepoint @var{num}
7019 Find the next snapshot associated with tracepoint @var{num}. Search
7020 proceeds forward from the last examined trace snapshot. If no
7021 argument @var{num} is given, it means find the next snapshot collected
7022 for the same tracepoint as the current snapshot.
7024 @item tfind pc @var{addr}
7025 Find the next snapshot associated with the value @var{addr} of the
7026 program counter. Search proceeds forward from the last examined trace
7027 snapshot. If no argument @var{addr} is given, it means find the next
7028 snapshot with the same value of PC as the current snapshot.
7030 @item tfind outside @var{addr1}, @var{addr2}
7031 Find the next snapshot whose PC is outside the given range of
7034 @item tfind range @var{addr1}, @var{addr2}
7035 Find the next snapshot whose PC is between @var{addr1} and
7036 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
7038 @item tfind line @r{[}@var{file}:@r{]}@var{n}
7039 Find the next snapshot associated with the source line @var{n}. If
7040 the optional argument @var{file} is given, refer to line @var{n} in
7041 that source file. Search proceeds forward from the last examined
7042 trace snapshot. If no argument @var{n} is given, it means find the
7043 next line other than the one currently being examined; thus saying
7044 @code{tfind line} repeatedly can appear to have the same effect as
7045 stepping from line to line in a @emph{live} debugging session.
7048 The default arguments for the @code{tfind} commands are specifically
7049 designed to make it easy to scan through the trace buffer. For
7050 instance, @code{tfind} with no argument selects the next trace
7051 snapshot, and @code{tfind -} with no argument selects the previous
7052 trace snapshot. So, by giving one @code{tfind} command, and then
7053 simply hitting @key{RET} repeatedly you can examine all the trace
7054 snapshots in order. Or, by saying @code{tfind -} and then hitting
7055 @key{RET} repeatedly you can examine the snapshots in reverse order.
7056 The @code{tfind line} command with no argument selects the snapshot
7057 for the next source line executed. The @code{tfind pc} command with
7058 no argument selects the next snapshot with the same program counter
7059 (PC) as the current frame. The @code{tfind tracepoint} command with
7060 no argument selects the next trace snapshot collected by the same
7061 tracepoint as the current one.
7063 In addition to letting you scan through the trace buffer manually,
7064 these commands make it easy to construct @value{GDBN} scripts that
7065 scan through the trace buffer and print out whatever collected data
7066 you are interested in. Thus, if we want to examine the PC, FP, and SP
7067 registers from each trace frame in the buffer, we can say this:
7070 (@value{GDBP}) @b{tfind start}
7071 (@value{GDBP}) @b{while ($trace_frame != -1)}
7072 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
7073 $trace_frame, $pc, $sp, $fp
7077 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
7078 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
7079 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
7080 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
7081 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
7082 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
7083 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
7084 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
7085 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
7086 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
7087 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
7090 Or, if we want to examine the variable @code{X} at each source line in
7094 (@value{GDBP}) @b{tfind start}
7095 (@value{GDBP}) @b{while ($trace_frame != -1)}
7096 > printf "Frame %d, X == %d\n", $trace_frame, X
7106 @subsection @code{tdump}
7108 @cindex dump all data collected at tracepoint
7109 @cindex tracepoint data, display
7111 This command takes no arguments. It prints all the data collected at
7112 the current trace snapshot.
7115 (@value{GDBP}) @b{trace 444}
7116 (@value{GDBP}) @b{actions}
7117 Enter actions for tracepoint #2, one per line:
7118 > collect $regs, $locals, $args, gdb_long_test
7121 (@value{GDBP}) @b{tstart}
7123 (@value{GDBP}) @b{tfind line 444}
7124 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
7126 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
7128 (@value{GDBP}) @b{tdump}
7129 Data collected at tracepoint 2, trace frame 1:
7130 d0 0xc4aa0085 -995491707
7134 d4 0x71aea3d 119204413
7139 a1 0x3000668 50333288
7142 a4 0x3000698 50333336
7144 fp 0x30bf3c 0x30bf3c
7145 sp 0x30bf34 0x30bf34
7147 pc 0x20b2c8 0x20b2c8
7151 p = 0x20e5b4 "gdb-test"
7158 gdb_long_test = 17 '\021'
7163 @node save-tracepoints
7164 @subsection @code{save-tracepoints @var{filename}}
7165 @kindex save-tracepoints
7166 @cindex save tracepoints for future sessions
7168 This command saves all current tracepoint definitions together with
7169 their actions and passcounts, into a file @file{@var{filename}}
7170 suitable for use in a later debugging session. To read the saved
7171 tracepoint definitions, use the @code{source} command (@pxref{Command
7174 @node Tracepoint Variables
7175 @section Convenience Variables for Tracepoints
7176 @cindex tracepoint variables
7177 @cindex convenience variables for tracepoints
7180 @vindex $trace_frame
7181 @item (int) $trace_frame
7182 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
7183 snapshot is selected.
7186 @item (int) $tracepoint
7187 The tracepoint for the current trace snapshot.
7190 @item (int) $trace_line
7191 The line number for the current trace snapshot.
7194 @item (char []) $trace_file
7195 The source file for the current trace snapshot.
7198 @item (char []) $trace_func
7199 The name of the function containing @code{$tracepoint}.
7202 Note: @code{$trace_file} is not suitable for use in @code{printf},
7203 use @code{output} instead.
7205 Here's a simple example of using these convenience variables for
7206 stepping through all the trace snapshots and printing some of their
7210 (@value{GDBP}) @b{tfind start}
7212 (@value{GDBP}) @b{while $trace_frame != -1}
7213 > output $trace_file
7214 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
7220 @chapter Debugging Programs That Use Overlays
7223 If your program is too large to fit completely in your target system's
7224 memory, you can sometimes use @dfn{overlays} to work around this
7225 problem. @value{GDBN} provides some support for debugging programs that
7229 * How Overlays Work:: A general explanation of overlays.
7230 * Overlay Commands:: Managing overlays in @value{GDBN}.
7231 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
7232 mapped by asking the inferior.
7233 * Overlay Sample Program:: A sample program using overlays.
7236 @node How Overlays Work
7237 @section How Overlays Work
7238 @cindex mapped overlays
7239 @cindex unmapped overlays
7240 @cindex load address, overlay's
7241 @cindex mapped address
7242 @cindex overlay area
7244 Suppose you have a computer whose instruction address space is only 64
7245 kilobytes long, but which has much more memory which can be accessed by
7246 other means: special instructions, segment registers, or memory
7247 management hardware, for example. Suppose further that you want to
7248 adapt a program which is larger than 64 kilobytes to run on this system.
7250 One solution is to identify modules of your program which are relatively
7251 independent, and need not call each other directly; call these modules
7252 @dfn{overlays}. Separate the overlays from the main program, and place
7253 their machine code in the larger memory. Place your main program in
7254 instruction memory, but leave at least enough space there to hold the
7255 largest overlay as well.
7257 Now, to call a function located in an overlay, you must first copy that
7258 overlay's machine code from the large memory into the space set aside
7259 for it in the instruction memory, and then jump to its entry point
7262 @c NB: In the below the mapped area's size is greater or equal to the
7263 @c size of all overlays. This is intentional to remind the developer
7264 @c that overlays don't necessarily need to be the same size.
7268 Data Instruction Larger
7269 Address Space Address Space Address Space
7270 +-----------+ +-----------+ +-----------+
7272 +-----------+ +-----------+ +-----------+<-- overlay 1
7273 | program | | main | .----| overlay 1 | load address
7274 | variables | | program | | +-----------+
7275 | and heap | | | | | |
7276 +-----------+ | | | +-----------+<-- overlay 2
7277 | | +-----------+ | | | load address
7278 +-----------+ | | | .-| overlay 2 |
7280 mapped --->+-----------+ | | +-----------+
7282 | overlay | <-' | | |
7283 | area | <---' +-----------+<-- overlay 3
7284 | | <---. | | load address
7285 +-----------+ `--| overlay 3 |
7292 @anchor{A code overlay}A code overlay
7296 The diagram (@pxref{A code overlay}) shows a system with separate data
7297 and instruction address spaces. To map an overlay, the program copies
7298 its code from the larger address space to the instruction address space.
7299 Since the overlays shown here all use the same mapped address, only one
7300 may be mapped at a time. For a system with a single address space for
7301 data and instructions, the diagram would be similar, except that the
7302 program variables and heap would share an address space with the main
7303 program and the overlay area.
7305 An overlay loaded into instruction memory and ready for use is called a
7306 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
7307 instruction memory. An overlay not present (or only partially present)
7308 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
7309 is its address in the larger memory. The mapped address is also called
7310 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
7311 called the @dfn{load memory address}, or @dfn{LMA}.
7313 Unfortunately, overlays are not a completely transparent way to adapt a
7314 program to limited instruction memory. They introduce a new set of
7315 global constraints you must keep in mind as you design your program:
7320 Before calling or returning to a function in an overlay, your program
7321 must make sure that overlay is actually mapped. Otherwise, the call or
7322 return will transfer control to the right address, but in the wrong
7323 overlay, and your program will probably crash.
7326 If the process of mapping an overlay is expensive on your system, you
7327 will need to choose your overlays carefully to minimize their effect on
7328 your program's performance.
7331 The executable file you load onto your system must contain each
7332 overlay's instructions, appearing at the overlay's load address, not its
7333 mapped address. However, each overlay's instructions must be relocated
7334 and its symbols defined as if the overlay were at its mapped address.
7335 You can use GNU linker scripts to specify different load and relocation
7336 addresses for pieces of your program; see @ref{Overlay Description,,,
7337 ld.info, Using ld: the GNU linker}.
7340 The procedure for loading executable files onto your system must be able
7341 to load their contents into the larger address space as well as the
7342 instruction and data spaces.
7346 The overlay system described above is rather simple, and could be
7347 improved in many ways:
7352 If your system has suitable bank switch registers or memory management
7353 hardware, you could use those facilities to make an overlay's load area
7354 contents simply appear at their mapped address in instruction space.
7355 This would probably be faster than copying the overlay to its mapped
7356 area in the usual way.
7359 If your overlays are small enough, you could set aside more than one
7360 overlay area, and have more than one overlay mapped at a time.
7363 You can use overlays to manage data, as well as instructions. In
7364 general, data overlays are even less transparent to your design than
7365 code overlays: whereas code overlays only require care when you call or
7366 return to functions, data overlays require care every time you access
7367 the data. Also, if you change the contents of a data overlay, you
7368 must copy its contents back out to its load address before you can copy a
7369 different data overlay into the same mapped area.
7374 @node Overlay Commands
7375 @section Overlay Commands
7377 To use @value{GDBN}'s overlay support, each overlay in your program must
7378 correspond to a separate section of the executable file. The section's
7379 virtual memory address and load memory address must be the overlay's
7380 mapped and load addresses. Identifying overlays with sections allows
7381 @value{GDBN} to determine the appropriate address of a function or
7382 variable, depending on whether the overlay is mapped or not.
7384 @value{GDBN}'s overlay commands all start with the word @code{overlay};
7385 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
7390 Disable @value{GDBN}'s overlay support. When overlay support is
7391 disabled, @value{GDBN} assumes that all functions and variables are
7392 always present at their mapped addresses. By default, @value{GDBN}'s
7393 overlay support is disabled.
7395 @item overlay manual
7396 @kindex overlay manual
7397 @cindex manual overlay debugging
7398 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
7399 relies on you to tell it which overlays are mapped, and which are not,
7400 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
7401 commands described below.
7403 @item overlay map-overlay @var{overlay}
7404 @itemx overlay map @var{overlay}
7405 @kindex overlay map-overlay
7406 @cindex map an overlay
7407 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
7408 be the name of the object file section containing the overlay. When an
7409 overlay is mapped, @value{GDBN} assumes it can find the overlay's
7410 functions and variables at their mapped addresses. @value{GDBN} assumes
7411 that any other overlays whose mapped ranges overlap that of
7412 @var{overlay} are now unmapped.
7414 @item overlay unmap-overlay @var{overlay}
7415 @itemx overlay unmap @var{overlay}
7416 @kindex overlay unmap-overlay
7417 @cindex unmap an overlay
7418 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
7419 must be the name of the object file section containing the overlay.
7420 When an overlay is unmapped, @value{GDBN} assumes it can find the
7421 overlay's functions and variables at their load addresses.
7424 @kindex overlay auto
7425 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
7426 consults a data structure the overlay manager maintains in the inferior
7427 to see which overlays are mapped. For details, see @ref{Automatic
7430 @item overlay load-target
7432 @kindex overlay load-target
7433 @cindex reloading the overlay table
7434 Re-read the overlay table from the inferior. Normally, @value{GDBN}
7435 re-reads the table @value{GDBN} automatically each time the inferior
7436 stops, so this command should only be necessary if you have changed the
7437 overlay mapping yourself using @value{GDBN}. This command is only
7438 useful when using automatic overlay debugging.
7440 @item overlay list-overlays
7442 @cindex listing mapped overlays
7443 Display a list of the overlays currently mapped, along with their mapped
7444 addresses, load addresses, and sizes.
7448 Normally, when @value{GDBN} prints a code address, it includes the name
7449 of the function the address falls in:
7453 $3 = @{int ()@} 0x11a0 <main>
7456 When overlay debugging is enabled, @value{GDBN} recognizes code in
7457 unmapped overlays, and prints the names of unmapped functions with
7458 asterisks around them. For example, if @code{foo} is a function in an
7459 unmapped overlay, @value{GDBN} prints it this way:
7463 No sections are mapped.
7465 $5 = @{int (int)@} 0x100000 <*foo*>
7468 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
7473 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
7474 mapped at 0x1016 - 0x104a
7476 $6 = @{int (int)@} 0x1016 <foo>
7479 When overlay debugging is enabled, @value{GDBN} can find the correct
7480 address for functions and variables in an overlay, whether or not the
7481 overlay is mapped. This allows most @value{GDBN} commands, like
7482 @code{break} and @code{disassemble}, to work normally, even on unmapped
7483 code. However, @value{GDBN}'s breakpoint support has some limitations:
7487 @cindex breakpoints in overlays
7488 @cindex overlays, setting breakpoints in
7489 You can set breakpoints in functions in unmapped overlays, as long as
7490 @value{GDBN} can write to the overlay at its load address.
7492 @value{GDBN} can not set hardware or simulator-based breakpoints in
7493 unmapped overlays. However, if you set a breakpoint at the end of your
7494 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
7495 you are using manual overlay management), @value{GDBN} will re-set its
7496 breakpoints properly.
7500 @node Automatic Overlay Debugging
7501 @section Automatic Overlay Debugging
7502 @cindex automatic overlay debugging
7504 @value{GDBN} can automatically track which overlays are mapped and which
7505 are not, given some simple co-operation from the overlay manager in the
7506 inferior. If you enable automatic overlay debugging with the
7507 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
7508 looks in the inferior's memory for certain variables describing the
7509 current state of the overlays.
7511 Here are the variables your overlay manager must define to support
7512 @value{GDBN}'s automatic overlay debugging:
7516 @item @code{_ovly_table}:
7517 This variable must be an array of the following structures:
7522 /* The overlay's mapped address. */
7525 /* The size of the overlay, in bytes. */
7528 /* The overlay's load address. */
7531 /* Non-zero if the overlay is currently mapped;
7533 unsigned long mapped;
7537 @item @code{_novlys}:
7538 This variable must be a four-byte signed integer, holding the total
7539 number of elements in @code{_ovly_table}.
7543 To decide whether a particular overlay is mapped or not, @value{GDBN}
7544 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
7545 @code{lma} members equal the VMA and LMA of the overlay's section in the
7546 executable file. When @value{GDBN} finds a matching entry, it consults
7547 the entry's @code{mapped} member to determine whether the overlay is
7550 In addition, your overlay manager may define a function called
7551 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
7552 will silently set a breakpoint there. If the overlay manager then
7553 calls this function whenever it has changed the overlay table, this
7554 will enable @value{GDBN} to accurately keep track of which overlays
7555 are in program memory, and update any breakpoints that may be set
7556 in overlays. This will allow breakpoints to work even if the
7557 overlays are kept in ROM or other non-writable memory while they
7558 are not being executed.
7560 @node Overlay Sample Program
7561 @section Overlay Sample Program
7562 @cindex overlay example program
7564 When linking a program which uses overlays, you must place the overlays
7565 at their load addresses, while relocating them to run at their mapped
7566 addresses. To do this, you must write a linker script (@pxref{Overlay
7567 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
7568 since linker scripts are specific to a particular host system, target
7569 architecture, and target memory layout, this manual cannot provide
7570 portable sample code demonstrating @value{GDBN}'s overlay support.
7572 However, the @value{GDBN} source distribution does contain an overlaid
7573 program, with linker scripts for a few systems, as part of its test
7574 suite. The program consists of the following files from
7575 @file{gdb/testsuite/gdb.base}:
7579 The main program file.
7581 A simple overlay manager, used by @file{overlays.c}.
7586 Overlay modules, loaded and used by @file{overlays.c}.
7589 Linker scripts for linking the test program on the @code{d10v-elf}
7590 and @code{m32r-elf} targets.
7593 You can build the test program using the @code{d10v-elf} GCC
7594 cross-compiler like this:
7597 $ d10v-elf-gcc -g -c overlays.c
7598 $ d10v-elf-gcc -g -c ovlymgr.c
7599 $ d10v-elf-gcc -g -c foo.c
7600 $ d10v-elf-gcc -g -c bar.c
7601 $ d10v-elf-gcc -g -c baz.c
7602 $ d10v-elf-gcc -g -c grbx.c
7603 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
7604 baz.o grbx.o -Wl,-Td10v.ld -o overlays
7607 The build process is identical for any other architecture, except that
7608 you must substitute the appropriate compiler and linker script for the
7609 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
7613 @chapter Using @value{GDBN} with Different Languages
7616 Although programming languages generally have common aspects, they are
7617 rarely expressed in the same manner. For instance, in ANSI C,
7618 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
7619 Modula-2, it is accomplished by @code{p^}. Values can also be
7620 represented (and displayed) differently. Hex numbers in C appear as
7621 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
7623 @cindex working language
7624 Language-specific information is built into @value{GDBN} for some languages,
7625 allowing you to express operations like the above in your program's
7626 native language, and allowing @value{GDBN} to output values in a manner
7627 consistent with the syntax of your program's native language. The
7628 language you use to build expressions is called the @dfn{working
7632 * Setting:: Switching between source languages
7633 * Show:: Displaying the language
7634 * Checks:: Type and range checks
7635 * Support:: Supported languages
7636 * Unsupported languages:: Unsupported languages
7640 @section Switching between source languages
7642 There are two ways to control the working language---either have @value{GDBN}
7643 set it automatically, or select it manually yourself. You can use the
7644 @code{set language} command for either purpose. On startup, @value{GDBN}
7645 defaults to setting the language automatically. The working language is
7646 used to determine how expressions you type are interpreted, how values
7649 In addition to the working language, every source file that
7650 @value{GDBN} knows about has its own working language. For some object
7651 file formats, the compiler might indicate which language a particular
7652 source file is in. However, most of the time @value{GDBN} infers the
7653 language from the name of the file. The language of a source file
7654 controls whether C@t{++} names are demangled---this way @code{backtrace} can
7655 show each frame appropriately for its own language. There is no way to
7656 set the language of a source file from within @value{GDBN}, but you can
7657 set the language associated with a filename extension. @xref{Show, ,
7658 Displaying the language}.
7660 This is most commonly a problem when you use a program, such
7661 as @code{cfront} or @code{f2c}, that generates C but is written in
7662 another language. In that case, make the
7663 program use @code{#line} directives in its C output; that way
7664 @value{GDBN} will know the correct language of the source code of the original
7665 program, and will display that source code, not the generated C code.
7668 * Filenames:: Filename extensions and languages.
7669 * Manually:: Setting the working language manually
7670 * Automatically:: Having @value{GDBN} infer the source language
7674 @subsection List of filename extensions and languages
7676 If a source file name ends in one of the following extensions, then
7677 @value{GDBN} infers that its language is the one indicated.
7693 Objective-C source file
7700 Modula-2 source file
7704 Assembler source file. This actually behaves almost like C, but
7705 @value{GDBN} does not skip over function prologues when stepping.
7708 In addition, you may set the language associated with a filename
7709 extension. @xref{Show, , Displaying the language}.
7712 @subsection Setting the working language
7714 If you allow @value{GDBN} to set the language automatically,
7715 expressions are interpreted the same way in your debugging session and
7718 @kindex set language
7719 If you wish, you may set the language manually. To do this, issue the
7720 command @samp{set language @var{lang}}, where @var{lang} is the name of
7722 @code{c} or @code{modula-2}.
7723 For a list of the supported languages, type @samp{set language}.
7725 Setting the language manually prevents @value{GDBN} from updating the working
7726 language automatically. This can lead to confusion if you try
7727 to debug a program when the working language is not the same as the
7728 source language, when an expression is acceptable to both
7729 languages---but means different things. For instance, if the current
7730 source file were written in C, and @value{GDBN} was parsing Modula-2, a
7738 might not have the effect you intended. In C, this means to add
7739 @code{b} and @code{c} and place the result in @code{a}. The result
7740 printed would be the value of @code{a}. In Modula-2, this means to compare
7741 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
7744 @subsection Having @value{GDBN} infer the source language
7746 To have @value{GDBN} set the working language automatically, use
7747 @samp{set language local} or @samp{set language auto}. @value{GDBN}
7748 then infers the working language. That is, when your program stops in a
7749 frame (usually by encountering a breakpoint), @value{GDBN} sets the
7750 working language to the language recorded for the function in that
7751 frame. If the language for a frame is unknown (that is, if the function
7752 or block corresponding to the frame was defined in a source file that
7753 does not have a recognized extension), the current working language is
7754 not changed, and @value{GDBN} issues a warning.
7756 This may not seem necessary for most programs, which are written
7757 entirely in one source language. However, program modules and libraries
7758 written in one source language can be used by a main program written in
7759 a different source language. Using @samp{set language auto} in this
7760 case frees you from having to set the working language manually.
7763 @section Displaying the language
7765 The following commands help you find out which language is the
7766 working language, and also what language source files were written in.
7768 @kindex show language
7769 @kindex info frame@r{, show the source language}
7770 @kindex info source@r{, show the source language}
7773 Display the current working language. This is the
7774 language you can use with commands such as @code{print} to
7775 build and compute expressions that may involve variables in your program.
7778 Display the source language for this frame. This language becomes the
7779 working language if you use an identifier from this frame.
7780 @xref{Frame Info, ,Information about a frame}, to identify the other
7781 information listed here.
7784 Display the source language of this source file.
7785 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
7786 information listed here.
7789 In unusual circumstances, you may have source files with extensions
7790 not in the standard list. You can then set the extension associated
7791 with a language explicitly:
7793 @kindex set extension-language
7794 @kindex info extensions
7796 @item set extension-language @var{.ext} @var{language}
7797 Set source files with extension @var{.ext} to be assumed to be in
7798 the source language @var{language}.
7800 @item info extensions
7801 List all the filename extensions and the associated languages.
7805 @section Type and range checking
7808 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
7809 checking are included, but they do not yet have any effect. This
7810 section documents the intended facilities.
7812 @c FIXME remove warning when type/range code added
7814 Some languages are designed to guard you against making seemingly common
7815 errors through a series of compile- and run-time checks. These include
7816 checking the type of arguments to functions and operators, and making
7817 sure mathematical overflows are caught at run time. Checks such as
7818 these help to ensure a program's correctness once it has been compiled
7819 by eliminating type mismatches, and providing active checks for range
7820 errors when your program is running.
7822 @value{GDBN} can check for conditions like the above if you wish.
7823 Although @value{GDBN} does not check the statements in your program, it
7824 can check expressions entered directly into @value{GDBN} for evaluation via
7825 the @code{print} command, for example. As with the working language,
7826 @value{GDBN} can also decide whether or not to check automatically based on
7827 your program's source language. @xref{Support, ,Supported languages},
7828 for the default settings of supported languages.
7831 * Type Checking:: An overview of type checking
7832 * Range Checking:: An overview of range checking
7835 @cindex type checking
7836 @cindex checks, type
7838 @subsection An overview of type checking
7840 Some languages, such as Modula-2, are strongly typed, meaning that the
7841 arguments to operators and functions have to be of the correct type,
7842 otherwise an error occurs. These checks prevent type mismatch
7843 errors from ever causing any run-time problems. For example,
7851 The second example fails because the @code{CARDINAL} 1 is not
7852 type-compatible with the @code{REAL} 2.3.
7854 For the expressions you use in @value{GDBN} commands, you can tell the
7855 @value{GDBN} type checker to skip checking;
7856 to treat any mismatches as errors and abandon the expression;
7857 or to only issue warnings when type mismatches occur,
7858 but evaluate the expression anyway. When you choose the last of
7859 these, @value{GDBN} evaluates expressions like the second example above, but
7860 also issues a warning.
7862 Even if you turn type checking off, there may be other reasons
7863 related to type that prevent @value{GDBN} from evaluating an expression.
7864 For instance, @value{GDBN} does not know how to add an @code{int} and
7865 a @code{struct foo}. These particular type errors have nothing to do
7866 with the language in use, and usually arise from expressions, such as
7867 the one described above, which make little sense to evaluate anyway.
7869 Each language defines to what degree it is strict about type. For
7870 instance, both Modula-2 and C require the arguments to arithmetical
7871 operators to be numbers. In C, enumerated types and pointers can be
7872 represented as numbers, so that they are valid arguments to mathematical
7873 operators. @xref{Support, ,Supported languages}, for further
7874 details on specific languages.
7876 @value{GDBN} provides some additional commands for controlling the type checker:
7878 @kindex set check@r{, type}
7879 @kindex set check type
7880 @kindex show check type
7882 @item set check type auto
7883 Set type checking on or off based on the current working language.
7884 @xref{Support, ,Supported languages}, for the default settings for
7887 @item set check type on
7888 @itemx set check type off
7889 Set type checking on or off, overriding the default setting for the
7890 current working language. Issue a warning if the setting does not
7891 match the language default. If any type mismatches occur in
7892 evaluating an expression while type checking is on, @value{GDBN} prints a
7893 message and aborts evaluation of the expression.
7895 @item set check type warn
7896 Cause the type checker to issue warnings, but to always attempt to
7897 evaluate the expression. Evaluating the expression may still
7898 be impossible for other reasons. For example, @value{GDBN} cannot add
7899 numbers and structures.
7902 Show the current setting of the type checker, and whether or not @value{GDBN}
7903 is setting it automatically.
7906 @cindex range checking
7907 @cindex checks, range
7908 @node Range Checking
7909 @subsection An overview of range checking
7911 In some languages (such as Modula-2), it is an error to exceed the
7912 bounds of a type; this is enforced with run-time checks. Such range
7913 checking is meant to ensure program correctness by making sure
7914 computations do not overflow, or indices on an array element access do
7915 not exceed the bounds of the array.
7917 For expressions you use in @value{GDBN} commands, you can tell
7918 @value{GDBN} to treat range errors in one of three ways: ignore them,
7919 always treat them as errors and abandon the expression, or issue
7920 warnings but evaluate the expression anyway.
7922 A range error can result from numerical overflow, from exceeding an
7923 array index bound, or when you type a constant that is not a member
7924 of any type. Some languages, however, do not treat overflows as an
7925 error. In many implementations of C, mathematical overflow causes the
7926 result to ``wrap around'' to lower values---for example, if @var{m} is
7927 the largest integer value, and @var{s} is the smallest, then
7930 @var{m} + 1 @result{} @var{s}
7933 This, too, is specific to individual languages, and in some cases
7934 specific to individual compilers or machines. @xref{Support, ,
7935 Supported languages}, for further details on specific languages.
7937 @value{GDBN} provides some additional commands for controlling the range checker:
7939 @kindex set check@r{, range}
7940 @kindex set check range
7941 @kindex show check range
7943 @item set check range auto
7944 Set range checking on or off based on the current working language.
7945 @xref{Support, ,Supported languages}, for the default settings for
7948 @item set check range on
7949 @itemx set check range off
7950 Set range checking on or off, overriding the default setting for the
7951 current working language. A warning is issued if the setting does not
7952 match the language default. If a range error occurs and range checking is on,
7953 then a message is printed and evaluation of the expression is aborted.
7955 @item set check range warn
7956 Output messages when the @value{GDBN} range checker detects a range error,
7957 but attempt to evaluate the expression anyway. Evaluating the
7958 expression may still be impossible for other reasons, such as accessing
7959 memory that the process does not own (a typical example from many Unix
7963 Show the current setting of the range checker, and whether or not it is
7964 being set automatically by @value{GDBN}.
7968 @section Supported languages
7970 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, assembly, and Modula-2.
7971 @c This is false ...
7972 Some @value{GDBN} features may be used in expressions regardless of the
7973 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
7974 and the @samp{@{type@}addr} construct (@pxref{Expressions,
7975 ,Expressions}) can be used with the constructs of any supported
7978 The following sections detail to what degree each source language is
7979 supported by @value{GDBN}. These sections are not meant to be language
7980 tutorials or references, but serve only as a reference guide to what the
7981 @value{GDBN} expression parser accepts, and what input and output
7982 formats should look like for different languages. There are many good
7983 books written on each of these languages; please look to these for a
7984 language reference or tutorial.
7988 * Objective-C:: Objective-C
7989 * Modula-2:: Modula-2
7993 @subsection C and C@t{++}
7995 @cindex C and C@t{++}
7996 @cindex expressions in C or C@t{++}
7998 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
7999 to both languages. Whenever this is the case, we discuss those languages
8003 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
8004 @cindex @sc{gnu} C@t{++}
8005 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
8006 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
8007 effectively, you must compile your C@t{++} programs with a supported
8008 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
8009 compiler (@code{aCC}).
8011 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
8012 format; if it doesn't work on your system, try the stabs+ debugging
8013 format. You can select those formats explicitly with the @code{g++}
8014 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
8015 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
8016 CC, gcc.info, Using @sc{gnu} CC}.
8019 * C Operators:: C and C@t{++} operators
8020 * C Constants:: C and C@t{++} constants
8021 * C plus plus expressions:: C@t{++} expressions
8022 * C Defaults:: Default settings for C and C@t{++}
8023 * C Checks:: C and C@t{++} type and range checks
8024 * Debugging C:: @value{GDBN} and C
8025 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
8029 @subsubsection C and C@t{++} operators
8031 @cindex C and C@t{++} operators
8033 Operators must be defined on values of specific types. For instance,
8034 @code{+} is defined on numbers, but not on structures. Operators are
8035 often defined on groups of types.
8037 For the purposes of C and C@t{++}, the following definitions hold:
8042 @emph{Integral types} include @code{int} with any of its storage-class
8043 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
8046 @emph{Floating-point types} include @code{float}, @code{double}, and
8047 @code{long double} (if supported by the target platform).
8050 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
8053 @emph{Scalar types} include all of the above.
8058 The following operators are supported. They are listed here
8059 in order of increasing precedence:
8063 The comma or sequencing operator. Expressions in a comma-separated list
8064 are evaluated from left to right, with the result of the entire
8065 expression being the last expression evaluated.
8068 Assignment. The value of an assignment expression is the value
8069 assigned. Defined on scalar types.
8072 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
8073 and translated to @w{@code{@var{a} = @var{a op b}}}.
8074 @w{@code{@var{op}=}} and @code{=} have the same precedence.
8075 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
8076 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
8079 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
8080 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
8084 Logical @sc{or}. Defined on integral types.
8087 Logical @sc{and}. Defined on integral types.
8090 Bitwise @sc{or}. Defined on integral types.
8093 Bitwise exclusive-@sc{or}. Defined on integral types.
8096 Bitwise @sc{and}. Defined on integral types.
8099 Equality and inequality. Defined on scalar types. The value of these
8100 expressions is 0 for false and non-zero for true.
8102 @item <@r{, }>@r{, }<=@r{, }>=
8103 Less than, greater than, less than or equal, greater than or equal.
8104 Defined on scalar types. The value of these expressions is 0 for false
8105 and non-zero for true.
8108 left shift, and right shift. Defined on integral types.
8111 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8114 Addition and subtraction. Defined on integral types, floating-point types and
8117 @item *@r{, }/@r{, }%
8118 Multiplication, division, and modulus. Multiplication and division are
8119 defined on integral and floating-point types. Modulus is defined on
8123 Increment and decrement. When appearing before a variable, the
8124 operation is performed before the variable is used in an expression;
8125 when appearing after it, the variable's value is used before the
8126 operation takes place.
8129 Pointer dereferencing. Defined on pointer types. Same precedence as
8133 Address operator. Defined on variables. Same precedence as @code{++}.
8135 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
8136 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
8137 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
8138 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
8142 Negative. Defined on integral and floating-point types. Same
8143 precedence as @code{++}.
8146 Logical negation. Defined on integral types. Same precedence as
8150 Bitwise complement operator. Defined on integral types. Same precedence as
8155 Structure member, and pointer-to-structure member. For convenience,
8156 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
8157 pointer based on the stored type information.
8158 Defined on @code{struct} and @code{union} data.
8161 Dereferences of pointers to members.
8164 Array indexing. @code{@var{a}[@var{i}]} is defined as
8165 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
8168 Function parameter list. Same precedence as @code{->}.
8171 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
8172 and @code{class} types.
8175 Doubled colons also represent the @value{GDBN} scope operator
8176 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
8180 If an operator is redefined in the user code, @value{GDBN} usually
8181 attempts to invoke the redefined version instead of using the operator's
8189 @subsubsection C and C@t{++} constants
8191 @cindex C and C@t{++} constants
8193 @value{GDBN} allows you to express the constants of C and C@t{++} in the
8198 Integer constants are a sequence of digits. Octal constants are
8199 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
8200 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
8201 @samp{l}, specifying that the constant should be treated as a
8205 Floating point constants are a sequence of digits, followed by a decimal
8206 point, followed by a sequence of digits, and optionally followed by an
8207 exponent. An exponent is of the form:
8208 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
8209 sequence of digits. The @samp{+} is optional for positive exponents.
8210 A floating-point constant may also end with a letter @samp{f} or
8211 @samp{F}, specifying that the constant should be treated as being of
8212 the @code{float} (as opposed to the default @code{double}) type; or with
8213 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
8217 Enumerated constants consist of enumerated identifiers, or their
8218 integral equivalents.
8221 Character constants are a single character surrounded by single quotes
8222 (@code{'}), or a number---the ordinal value of the corresponding character
8223 (usually its @sc{ascii} value). Within quotes, the single character may
8224 be represented by a letter or by @dfn{escape sequences}, which are of
8225 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
8226 of the character's ordinal value; or of the form @samp{\@var{x}}, where
8227 @samp{@var{x}} is a predefined special character---for example,
8228 @samp{\n} for newline.
8231 String constants are a sequence of character constants surrounded by
8232 double quotes (@code{"}). Any valid character constant (as described
8233 above) may appear. Double quotes within the string must be preceded by
8234 a backslash, so for instance @samp{"a\"b'c"} is a string of five
8238 Pointer constants are an integral value. You can also write pointers
8239 to constants using the C operator @samp{&}.
8242 Array constants are comma-separated lists surrounded by braces @samp{@{}
8243 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
8244 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
8245 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
8249 * C plus plus expressions::
8256 @node C plus plus expressions
8257 @subsubsection C@t{++} expressions
8259 @cindex expressions in C@t{++}
8260 @value{GDBN} expression handling can interpret most C@t{++} expressions.
8262 @cindex debugging C@t{++} programs
8263 @cindex C@t{++} compilers
8264 @cindex debug formats and C@t{++}
8265 @cindex @value{NGCC} and C@t{++}
8267 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
8268 proper compiler and the proper debug format. Currently, @value{GDBN}
8269 works best when debugging C@t{++} code that is compiled with
8270 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
8271 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
8272 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
8273 stabs+ as their default debug format, so you usually don't need to
8274 specify a debug format explicitly. Other compilers and/or debug formats
8275 are likely to work badly or not at all when using @value{GDBN} to debug
8281 @cindex member functions
8283 Member function calls are allowed; you can use expressions like
8286 count = aml->GetOriginal(x, y)
8289 @vindex this@r{, inside C@t{++} member functions}
8290 @cindex namespace in C@t{++}
8292 While a member function is active (in the selected stack frame), your
8293 expressions have the same namespace available as the member function;
8294 that is, @value{GDBN} allows implicit references to the class instance
8295 pointer @code{this} following the same rules as C@t{++}.
8297 @cindex call overloaded functions
8298 @cindex overloaded functions, calling
8299 @cindex type conversions in C@t{++}
8301 You can call overloaded functions; @value{GDBN} resolves the function
8302 call to the right definition, with some restrictions. @value{GDBN} does not
8303 perform overload resolution involving user-defined type conversions,
8304 calls to constructors, or instantiations of templates that do not exist
8305 in the program. It also cannot handle ellipsis argument lists or
8308 It does perform integral conversions and promotions, floating-point
8309 promotions, arithmetic conversions, pointer conversions, conversions of
8310 class objects to base classes, and standard conversions such as those of
8311 functions or arrays to pointers; it requires an exact match on the
8312 number of function arguments.
8314 Overload resolution is always performed, unless you have specified
8315 @code{set overload-resolution off}. @xref{Debugging C plus plus,
8316 ,@value{GDBN} features for C@t{++}}.
8318 You must specify @code{set overload-resolution off} in order to use an
8319 explicit function signature to call an overloaded function, as in
8321 p 'foo(char,int)'('x', 13)
8324 The @value{GDBN} command-completion facility can simplify this;
8325 see @ref{Completion, ,Command completion}.
8327 @cindex reference declarations
8329 @value{GDBN} understands variables declared as C@t{++} references; you can use
8330 them in expressions just as you do in C@t{++} source---they are automatically
8333 In the parameter list shown when @value{GDBN} displays a frame, the values of
8334 reference variables are not displayed (unlike other variables); this
8335 avoids clutter, since references are often used for large structures.
8336 The @emph{address} of a reference variable is always shown, unless
8337 you have specified @samp{set print address off}.
8340 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
8341 expressions can use it just as expressions in your program do. Since
8342 one scope may be defined in another, you can use @code{::} repeatedly if
8343 necessary, for example in an expression like
8344 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
8345 resolving name scope by reference to source files, in both C and C@t{++}
8346 debugging (@pxref{Variables, ,Program variables}).
8349 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
8350 calling virtual functions correctly, printing out virtual bases of
8351 objects, calling functions in a base subobject, casting objects, and
8352 invoking user-defined operators.
8355 @subsubsection C and C@t{++} defaults
8357 @cindex C and C@t{++} defaults
8359 If you allow @value{GDBN} to set type and range checking automatically, they
8360 both default to @code{off} whenever the working language changes to
8361 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
8362 selects the working language.
8364 If you allow @value{GDBN} to set the language automatically, it
8365 recognizes source files whose names end with @file{.c}, @file{.C}, or
8366 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
8367 these files, it sets the working language to C or C@t{++}.
8368 @xref{Automatically, ,Having @value{GDBN} infer the source language},
8369 for further details.
8371 @c Type checking is (a) primarily motivated by Modula-2, and (b)
8372 @c unimplemented. If (b) changes, it might make sense to let this node
8373 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
8376 @subsubsection C and C@t{++} type and range checks
8378 @cindex C and C@t{++} checks
8380 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
8381 is not used. However, if you turn type checking on, @value{GDBN}
8382 considers two variables type equivalent if:
8386 The two variables are structured and have the same structure, union, or
8390 The two variables have the same type name, or types that have been
8391 declared equivalent through @code{typedef}.
8394 @c leaving this out because neither J Gilmore nor R Pesch understand it.
8397 The two @code{struct}, @code{union}, or @code{enum} variables are
8398 declared in the same declaration. (Note: this may not be true for all C
8403 Range checking, if turned on, is done on mathematical operations. Array
8404 indices are not checked, since they are often used to index a pointer
8405 that is not itself an array.
8408 @subsubsection @value{GDBN} and C
8410 The @code{set print union} and @code{show print union} commands apply to
8411 the @code{union} type. When set to @samp{on}, any @code{union} that is
8412 inside a @code{struct} or @code{class} is also printed. Otherwise, it
8413 appears as @samp{@{...@}}.
8415 The @code{@@} operator aids in the debugging of dynamic arrays, formed
8416 with pointers and a memory allocation function. @xref{Expressions,
8420 * Debugging C plus plus::
8423 @node Debugging C plus plus
8424 @subsubsection @value{GDBN} features for C@t{++}
8426 @cindex commands for C@t{++}
8428 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
8429 designed specifically for use with C@t{++}. Here is a summary:
8432 @cindex break in overloaded functions
8433 @item @r{breakpoint menus}
8434 When you want a breakpoint in a function whose name is overloaded,
8435 @value{GDBN} breakpoint menus help you specify which function definition
8436 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
8438 @cindex overloading in C@t{++}
8439 @item rbreak @var{regex}
8440 Setting breakpoints using regular expressions is helpful for setting
8441 breakpoints on overloaded functions that are not members of any special
8443 @xref{Set Breaks, ,Setting breakpoints}.
8445 @cindex C@t{++} exception handling
8448 Debug C@t{++} exception handling using these commands. @xref{Set
8449 Catchpoints, , Setting catchpoints}.
8452 @item ptype @var{typename}
8453 Print inheritance relationships as well as other information for type
8455 @xref{Symbols, ,Examining the Symbol Table}.
8457 @cindex C@t{++} symbol display
8458 @item set print demangle
8459 @itemx show print demangle
8460 @itemx set print asm-demangle
8461 @itemx show print asm-demangle
8462 Control whether C@t{++} symbols display in their source form, both when
8463 displaying code as C@t{++} source and when displaying disassemblies.
8464 @xref{Print Settings, ,Print settings}.
8466 @item set print object
8467 @itemx show print object
8468 Choose whether to print derived (actual) or declared types of objects.
8469 @xref{Print Settings, ,Print settings}.
8471 @item set print vtbl
8472 @itemx show print vtbl
8473 Control the format for printing virtual function tables.
8474 @xref{Print Settings, ,Print settings}.
8475 (The @code{vtbl} commands do not work on programs compiled with the HP
8476 ANSI C@t{++} compiler (@code{aCC}).)
8478 @kindex set overload-resolution
8479 @cindex overloaded functions, overload resolution
8480 @item set overload-resolution on
8481 Enable overload resolution for C@t{++} expression evaluation. The default
8482 is on. For overloaded functions, @value{GDBN} evaluates the arguments
8483 and searches for a function whose signature matches the argument types,
8484 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
8485 expressions}, for details). If it cannot find a match, it emits a
8488 @item set overload-resolution off
8489 Disable overload resolution for C@t{++} expression evaluation. For
8490 overloaded functions that are not class member functions, @value{GDBN}
8491 chooses the first function of the specified name that it finds in the
8492 symbol table, whether or not its arguments are of the correct type. For
8493 overloaded functions that are class member functions, @value{GDBN}
8494 searches for a function whose signature @emph{exactly} matches the
8497 @item @r{Overloaded symbol names}
8498 You can specify a particular definition of an overloaded symbol, using
8499 the same notation that is used to declare such symbols in C@t{++}: type
8500 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
8501 also use the @value{GDBN} command-line word completion facilities to list the
8502 available choices, or to finish the type list for you.
8503 @xref{Completion,, Command completion}, for details on how to do this.
8507 @subsection Objective-C
8510 This section provides information about some commands and command
8511 options that are useful for debugging Objective-C code.
8514 * Method Names in Commands::
8515 * The Print Command with Objective-C::
8518 @node Method Names in Commands, The Print Command with Objective-C, Objective-C, Objective-C
8519 @subsubsection Method Names in Commands
8521 The following commands have been extended to accept Objective-C method
8522 names as line specifications:
8524 @kindex clear@r{, and Objective-C}
8525 @kindex break@r{, and Objective-C}
8526 @kindex info line@r{, and Objective-C}
8527 @kindex jump@r{, and Objective-C}
8528 @kindex list@r{, and Objective-C}
8532 @item @code{info line}
8537 A fully qualified Objective-C method name is specified as
8540 -[@var{Class} @var{methodName}]
8543 where the minus sign is used to indicate an instance method and a
8544 plus sign (not shown) is used to indicate a class method. The class
8545 name @var{Class} and method name @var{methodName} are enclosed in
8546 brackets, similar to the way messages are specified in Objective-C
8547 source code. For example, to set a breakpoint at the @code{create}
8548 instance method of class @code{Fruit} in the program currently being
8552 break -[Fruit create]
8555 To list ten program lines around the @code{initialize} class method,
8559 list +[NSText initialize]
8562 In the current version of @value{GDBN}, the plus or minus sign is
8563 required. In future versions of @value{GDBN}, the plus or minus
8564 sign will be optional, but you can use it to narrow the search. It
8565 is also possible to specify just a method name:
8571 You must specify the complete method name, including any colons. If
8572 your program's source files contain more than one @code{create} method,
8573 you'll be presented with a numbered list of classes that implement that
8574 method. Indicate your choice by number, or type @samp{0} to exit if
8577 As another example, to clear a breakpoint established at the
8578 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
8581 clear -[NSWindow makeKeyAndOrderFront:]
8584 @node The Print Command with Objective-C
8585 @subsubsection The Print Command With Objective-C
8586 @kindex print-object
8587 @kindex po @r{(@code{print-object})}
8589 The print command has also been extended to accept methods. For example:
8592 print -[@var{object} hash]
8595 @cindex print an Objective-C object description
8596 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
8598 will tell @value{GDBN} to send the @code{hash} message to @var{object}
8599 and print the result. Also, an additional command has been added,
8600 @code{print-object} or @code{po} for short, which is meant to print
8601 the description of an object. However, this command may only work
8602 with certain Objective-C libraries that have a particular hook
8603 function, @code{_NSPrintForDebugger}, defined.
8605 @node Modula-2, , Objective-C, Support
8606 @subsection Modula-2
8608 @cindex Modula-2, @value{GDBN} support
8610 The extensions made to @value{GDBN} to support Modula-2 only support
8611 output from the @sc{gnu} Modula-2 compiler (which is currently being
8612 developed). Other Modula-2 compilers are not currently supported, and
8613 attempting to debug executables produced by them is most likely
8614 to give an error as @value{GDBN} reads in the executable's symbol
8617 @cindex expressions in Modula-2
8619 * M2 Operators:: Built-in operators
8620 * Built-In Func/Proc:: Built-in functions and procedures
8621 * M2 Constants:: Modula-2 constants
8622 * M2 Defaults:: Default settings for Modula-2
8623 * Deviations:: Deviations from standard Modula-2
8624 * M2 Checks:: Modula-2 type and range checks
8625 * M2 Scope:: The scope operators @code{::} and @code{.}
8626 * GDB/M2:: @value{GDBN} and Modula-2
8630 @subsubsection Operators
8631 @cindex Modula-2 operators
8633 Operators must be defined on values of specific types. For instance,
8634 @code{+} is defined on numbers, but not on structures. Operators are
8635 often defined on groups of types. For the purposes of Modula-2, the
8636 following definitions hold:
8641 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
8645 @emph{Character types} consist of @code{CHAR} and its subranges.
8648 @emph{Floating-point types} consist of @code{REAL}.
8651 @emph{Pointer types} consist of anything declared as @code{POINTER TO
8655 @emph{Scalar types} consist of all of the above.
8658 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
8661 @emph{Boolean types} consist of @code{BOOLEAN}.
8665 The following operators are supported, and appear in order of
8666 increasing precedence:
8670 Function argument or array index separator.
8673 Assignment. The value of @var{var} @code{:=} @var{value} is
8677 Less than, greater than on integral, floating-point, or enumerated
8681 Less than or equal to, greater than or equal to
8682 on integral, floating-point and enumerated types, or set inclusion on
8683 set types. Same precedence as @code{<}.
8685 @item =@r{, }<>@r{, }#
8686 Equality and two ways of expressing inequality, valid on scalar types.
8687 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
8688 available for inequality, since @code{#} conflicts with the script
8692 Set membership. Defined on set types and the types of their members.
8693 Same precedence as @code{<}.
8696 Boolean disjunction. Defined on boolean types.
8699 Boolean conjunction. Defined on boolean types.
8702 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8705 Addition and subtraction on integral and floating-point types, or union
8706 and difference on set types.
8709 Multiplication on integral and floating-point types, or set intersection
8713 Division on floating-point types, or symmetric set difference on set
8714 types. Same precedence as @code{*}.
8717 Integer division and remainder. Defined on integral types. Same
8718 precedence as @code{*}.
8721 Negative. Defined on @code{INTEGER} and @code{REAL} data.
8724 Pointer dereferencing. Defined on pointer types.
8727 Boolean negation. Defined on boolean types. Same precedence as
8731 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
8732 precedence as @code{^}.
8735 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
8738 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
8742 @value{GDBN} and Modula-2 scope operators.
8746 @emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
8747 treats the use of the operator @code{IN}, or the use of operators
8748 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
8749 @code{<=}, and @code{>=} on sets as an error.
8753 @node Built-In Func/Proc
8754 @subsubsection Built-in functions and procedures
8755 @cindex Modula-2 built-ins
8757 Modula-2 also makes available several built-in procedures and functions.
8758 In describing these, the following metavariables are used:
8763 represents an @code{ARRAY} variable.
8766 represents a @code{CHAR} constant or variable.
8769 represents a variable or constant of integral type.
8772 represents an identifier that belongs to a set. Generally used in the
8773 same function with the metavariable @var{s}. The type of @var{s} should
8774 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
8777 represents a variable or constant of integral or floating-point type.
8780 represents a variable or constant of floating-point type.
8786 represents a variable.
8789 represents a variable or constant of one of many types. See the
8790 explanation of the function for details.
8793 All Modula-2 built-in procedures also return a result, described below.
8797 Returns the absolute value of @var{n}.
8800 If @var{c} is a lower case letter, it returns its upper case
8801 equivalent, otherwise it returns its argument.
8804 Returns the character whose ordinal value is @var{i}.
8807 Decrements the value in the variable @var{v} by one. Returns the new value.
8809 @item DEC(@var{v},@var{i})
8810 Decrements the value in the variable @var{v} by @var{i}. Returns the
8813 @item EXCL(@var{m},@var{s})
8814 Removes the element @var{m} from the set @var{s}. Returns the new
8817 @item FLOAT(@var{i})
8818 Returns the floating point equivalent of the integer @var{i}.
8821 Returns the index of the last member of @var{a}.
8824 Increments the value in the variable @var{v} by one. Returns the new value.
8826 @item INC(@var{v},@var{i})
8827 Increments the value in the variable @var{v} by @var{i}. Returns the
8830 @item INCL(@var{m},@var{s})
8831 Adds the element @var{m} to the set @var{s} if it is not already
8832 there. Returns the new set.
8835 Returns the maximum value of the type @var{t}.
8838 Returns the minimum value of the type @var{t}.
8841 Returns boolean TRUE if @var{i} is an odd number.
8844 Returns the ordinal value of its argument. For example, the ordinal
8845 value of a character is its @sc{ascii} value (on machines supporting the
8846 @sc{ascii} character set). @var{x} must be of an ordered type, which include
8847 integral, character and enumerated types.
8850 Returns the size of its argument. @var{x} can be a variable or a type.
8852 @item TRUNC(@var{r})
8853 Returns the integral part of @var{r}.
8855 @item VAL(@var{t},@var{i})
8856 Returns the member of the type @var{t} whose ordinal value is @var{i}.
8860 @emph{Warning:} Sets and their operations are not yet supported, so
8861 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
8865 @cindex Modula-2 constants
8867 @subsubsection Constants
8869 @value{GDBN} allows you to express the constants of Modula-2 in the following
8875 Integer constants are simply a sequence of digits. When used in an
8876 expression, a constant is interpreted to be type-compatible with the
8877 rest of the expression. Hexadecimal integers are specified by a
8878 trailing @samp{H}, and octal integers by a trailing @samp{B}.
8881 Floating point constants appear as a sequence of digits, followed by a
8882 decimal point and another sequence of digits. An optional exponent can
8883 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
8884 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
8885 digits of the floating point constant must be valid decimal (base 10)
8889 Character constants consist of a single character enclosed by a pair of
8890 like quotes, either single (@code{'}) or double (@code{"}). They may
8891 also be expressed by their ordinal value (their @sc{ascii} value, usually)
8892 followed by a @samp{C}.
8895 String constants consist of a sequence of characters enclosed by a
8896 pair of like quotes, either single (@code{'}) or double (@code{"}).
8897 Escape sequences in the style of C are also allowed. @xref{C
8898 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
8902 Enumerated constants consist of an enumerated identifier.
8905 Boolean constants consist of the identifiers @code{TRUE} and
8909 Pointer constants consist of integral values only.
8912 Set constants are not yet supported.
8916 @subsubsection Modula-2 defaults
8917 @cindex Modula-2 defaults
8919 If type and range checking are set automatically by @value{GDBN}, they
8920 both default to @code{on} whenever the working language changes to
8921 Modula-2. This happens regardless of whether you or @value{GDBN}
8922 selected the working language.
8924 If you allow @value{GDBN} to set the language automatically, then entering
8925 code compiled from a file whose name ends with @file{.mod} sets the
8926 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
8927 the language automatically}, for further details.
8930 @subsubsection Deviations from standard Modula-2
8931 @cindex Modula-2, deviations from
8933 A few changes have been made to make Modula-2 programs easier to debug.
8934 This is done primarily via loosening its type strictness:
8938 Unlike in standard Modula-2, pointer constants can be formed by
8939 integers. This allows you to modify pointer variables during
8940 debugging. (In standard Modula-2, the actual address contained in a
8941 pointer variable is hidden from you; it can only be modified
8942 through direct assignment to another pointer variable or expression that
8943 returned a pointer.)
8946 C escape sequences can be used in strings and characters to represent
8947 non-printable characters. @value{GDBN} prints out strings with these
8948 escape sequences embedded. Single non-printable characters are
8949 printed using the @samp{CHR(@var{nnn})} format.
8952 The assignment operator (@code{:=}) returns the value of its right-hand
8956 All built-in procedures both modify @emph{and} return their argument.
8960 @subsubsection Modula-2 type and range checks
8961 @cindex Modula-2 checks
8964 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
8967 @c FIXME remove warning when type/range checks added
8969 @value{GDBN} considers two Modula-2 variables type equivalent if:
8973 They are of types that have been declared equivalent via a @code{TYPE
8974 @var{t1} = @var{t2}} statement
8977 They have been declared on the same line. (Note: This is true of the
8978 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
8981 As long as type checking is enabled, any attempt to combine variables
8982 whose types are not equivalent is an error.
8984 Range checking is done on all mathematical operations, assignment, array
8985 index bounds, and all built-in functions and procedures.
8988 @subsubsection The scope operators @code{::} and @code{.}
8990 @cindex @code{.}, Modula-2 scope operator
8991 @cindex colon, doubled as scope operator
8993 @vindex colon-colon@r{, in Modula-2}
8994 @c Info cannot handle :: but TeX can.
8997 @vindex ::@r{, in Modula-2}
9000 There are a few subtle differences between the Modula-2 scope operator
9001 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
9006 @var{module} . @var{id}
9007 @var{scope} :: @var{id}
9011 where @var{scope} is the name of a module or a procedure,
9012 @var{module} the name of a module, and @var{id} is any declared
9013 identifier within your program, except another module.
9015 Using the @code{::} operator makes @value{GDBN} search the scope
9016 specified by @var{scope} for the identifier @var{id}. If it is not
9017 found in the specified scope, then @value{GDBN} searches all scopes
9018 enclosing the one specified by @var{scope}.
9020 Using the @code{.} operator makes @value{GDBN} search the current scope for
9021 the identifier specified by @var{id} that was imported from the
9022 definition module specified by @var{module}. With this operator, it is
9023 an error if the identifier @var{id} was not imported from definition
9024 module @var{module}, or if @var{id} is not an identifier in
9028 @subsubsection @value{GDBN} and Modula-2
9030 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
9031 Five subcommands of @code{set print} and @code{show print} apply
9032 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
9033 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
9034 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
9035 analogue in Modula-2.
9037 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
9038 with any language, is not useful with Modula-2. Its
9039 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
9040 created in Modula-2 as they can in C or C@t{++}. However, because an
9041 address can be specified by an integral constant, the construct
9042 @samp{@{@var{type}@}@var{adrexp}} is still useful.
9044 @cindex @code{#} in Modula-2
9045 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
9046 interpreted as the beginning of a comment. Use @code{<>} instead.
9048 @node Unsupported languages
9049 @section Unsupported languages
9051 @cindex unsupported languages
9052 @cindex minimal language
9053 In addition to the other fully-supported programming languages,
9054 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
9055 It does not represent a real programming language, but provides a set
9056 of capabilities close to what the C or assembly languages provide.
9057 This should allow most simple operations to be performed while debugging
9058 an application that uses a language currently not supported by @value{GDBN}.
9060 If the language is set to @code{auto}, @value{GDBN} will automatically
9061 select this language if the current frame corresponds to an unsupported
9065 @chapter Examining the Symbol Table
9067 The commands described in this chapter allow you to inquire about the
9068 symbols (names of variables, functions and types) defined in your
9069 program. This information is inherent in the text of your program and
9070 does not change as your program executes. @value{GDBN} finds it in your
9071 program's symbol table, in the file indicated when you started @value{GDBN}
9072 (@pxref{File Options, ,Choosing files}), or by one of the
9073 file-management commands (@pxref{Files, ,Commands to specify files}).
9075 @cindex symbol names
9076 @cindex names of symbols
9077 @cindex quoting names
9078 Occasionally, you may need to refer to symbols that contain unusual
9079 characters, which @value{GDBN} ordinarily treats as word delimiters. The
9080 most frequent case is in referring to static variables in other
9081 source files (@pxref{Variables,,Program variables}). File names
9082 are recorded in object files as debugging symbols, but @value{GDBN} would
9083 ordinarily parse a typical file name, like @file{foo.c}, as the three words
9084 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
9085 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
9092 looks up the value of @code{x} in the scope of the file @file{foo.c}.
9095 @kindex info address
9096 @cindex address of a symbol
9097 @item info address @var{symbol}
9098 Describe where the data for @var{symbol} is stored. For a register
9099 variable, this says which register it is kept in. For a non-register
9100 local variable, this prints the stack-frame offset at which the variable
9103 Note the contrast with @samp{print &@var{symbol}}, which does not work
9104 at all for a register variable, and for a stack local variable prints
9105 the exact address of the current instantiation of the variable.
9108 @cindex symbol from address
9109 @item info symbol @var{addr}
9110 Print the name of a symbol which is stored at the address @var{addr}.
9111 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
9112 nearest symbol and an offset from it:
9115 (@value{GDBP}) info symbol 0x54320
9116 _initialize_vx + 396 in section .text
9120 This is the opposite of the @code{info address} command. You can use
9121 it to find out the name of a variable or a function given its address.
9124 @item whatis @var{expr}
9125 Print the data type of expression @var{expr}. @var{expr} is not
9126 actually evaluated, and any side-effecting operations (such as
9127 assignments or function calls) inside it do not take place.
9128 @xref{Expressions, ,Expressions}.
9131 Print the data type of @code{$}, the last value in the value history.
9134 @item ptype @var{typename}
9135 Print a description of data type @var{typename}. @var{typename} may be
9136 the name of a type, or for C code it may have the form @samp{class
9137 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
9138 @var{union-tag}} or @samp{enum @var{enum-tag}}.
9140 @item ptype @var{expr}
9142 Print a description of the type of expression @var{expr}. @code{ptype}
9143 differs from @code{whatis} by printing a detailed description, instead
9144 of just the name of the type.
9146 For example, for this variable declaration:
9149 struct complex @{double real; double imag;@} v;
9153 the two commands give this output:
9157 (@value{GDBP}) whatis v
9158 type = struct complex
9159 (@value{GDBP}) ptype v
9160 type = struct complex @{
9168 As with @code{whatis}, using @code{ptype} without an argument refers to
9169 the type of @code{$}, the last value in the value history.
9172 @item info types @var{regexp}
9174 Print a brief description of all types whose names match @var{regexp}
9175 (or all types in your program, if you supply no argument). Each
9176 complete typename is matched as though it were a complete line; thus,
9177 @samp{i type value} gives information on all types in your program whose
9178 names include the string @code{value}, but @samp{i type ^value$} gives
9179 information only on types whose complete name is @code{value}.
9181 This command differs from @code{ptype} in two ways: first, like
9182 @code{whatis}, it does not print a detailed description; second, it
9183 lists all source files where a type is defined.
9186 @cindex local variables
9187 @item info scope @var{addr}
9188 List all the variables local to a particular scope. This command
9189 accepts a location---a function name, a source line, or an address
9190 preceded by a @samp{*}, and prints all the variables local to the
9191 scope defined by that location. For example:
9194 (@value{GDBP}) @b{info scope command_line_handler}
9195 Scope for command_line_handler:
9196 Symbol rl is an argument at stack/frame offset 8, length 4.
9197 Symbol linebuffer is in static storage at address 0x150a18, length 4.
9198 Symbol linelength is in static storage at address 0x150a1c, length 4.
9199 Symbol p is a local variable in register $esi, length 4.
9200 Symbol p1 is a local variable in register $ebx, length 4.
9201 Symbol nline is a local variable in register $edx, length 4.
9202 Symbol repeat is a local variable at frame offset -8, length 4.
9206 This command is especially useful for determining what data to collect
9207 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
9212 Show information about the current source file---that is, the source file for
9213 the function containing the current point of execution:
9216 the name of the source file, and the directory containing it,
9218 the directory it was compiled in,
9220 its length, in lines,
9222 which programming language it is written in,
9224 whether the executable includes debugging information for that file, and
9225 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
9227 whether the debugging information includes information about
9228 preprocessor macros.
9232 @kindex info sources
9234 Print the names of all source files in your program for which there is
9235 debugging information, organized into two lists: files whose symbols
9236 have already been read, and files whose symbols will be read when needed.
9238 @kindex info functions
9239 @item info functions
9240 Print the names and data types of all defined functions.
9242 @item info functions @var{regexp}
9243 Print the names and data types of all defined functions
9244 whose names contain a match for regular expression @var{regexp}.
9245 Thus, @samp{info fun step} finds all functions whose names
9246 include @code{step}; @samp{info fun ^step} finds those whose names
9247 start with @code{step}. If a function name contains characters
9248 that conflict with the regular expression language (eg.
9249 @samp{operator*()}), they may be quoted with a backslash.
9251 @kindex info variables
9252 @item info variables
9253 Print the names and data types of all variables that are declared
9254 outside of functions (i.e.@: excluding local variables).
9256 @item info variables @var{regexp}
9257 Print the names and data types of all variables (except for local
9258 variables) whose names contain a match for regular expression
9261 @kindex info classes
9263 @itemx info classes @var{regexp}
9264 Display all Objective-C classes in your program, or
9265 (with the @var{regexp} argument) all those matching a particular regular
9268 @kindex info selectors
9269 @item info selectors
9270 @itemx info selectors @var{regexp}
9271 Display all Objective-C selectors in your program, or
9272 (with the @var{regexp} argument) all those matching a particular regular
9276 This was never implemented.
9277 @kindex info methods
9279 @itemx info methods @var{regexp}
9280 The @code{info methods} command permits the user to examine all defined
9281 methods within C@t{++} program, or (with the @var{regexp} argument) a
9282 specific set of methods found in the various C@t{++} classes. Many
9283 C@t{++} classes provide a large number of methods. Thus, the output
9284 from the @code{ptype} command can be overwhelming and hard to use. The
9285 @code{info-methods} command filters the methods, printing only those
9286 which match the regular-expression @var{regexp}.
9289 @cindex reloading symbols
9290 Some systems allow individual object files that make up your program to
9291 be replaced without stopping and restarting your program. For example,
9292 in VxWorks you can simply recompile a defective object file and keep on
9293 running. If you are running on one of these systems, you can allow
9294 @value{GDBN} to reload the symbols for automatically relinked modules:
9297 @kindex set symbol-reloading
9298 @item set symbol-reloading on
9299 Replace symbol definitions for the corresponding source file when an
9300 object file with a particular name is seen again.
9302 @item set symbol-reloading off
9303 Do not replace symbol definitions when encountering object files of the
9304 same name more than once. This is the default state; if you are not
9305 running on a system that permits automatic relinking of modules, you
9306 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
9307 may discard symbols when linking large programs, that may contain
9308 several modules (from different directories or libraries) with the same
9311 @kindex show symbol-reloading
9312 @item show symbol-reloading
9313 Show the current @code{on} or @code{off} setting.
9316 @kindex set opaque-type-resolution
9317 @item set opaque-type-resolution on
9318 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
9319 declared as a pointer to a @code{struct}, @code{class}, or
9320 @code{union}---for example, @code{struct MyType *}---that is used in one
9321 source file although the full declaration of @code{struct MyType} is in
9322 another source file. The default is on.
9324 A change in the setting of this subcommand will not take effect until
9325 the next time symbols for a file are loaded.
9327 @item set opaque-type-resolution off
9328 Tell @value{GDBN} not to resolve opaque types. In this case, the type
9329 is printed as follows:
9331 @{<no data fields>@}
9334 @kindex show opaque-type-resolution
9335 @item show opaque-type-resolution
9336 Show whether opaque types are resolved or not.
9338 @kindex maint print symbols
9340 @kindex maint print psymbols
9341 @cindex partial symbol dump
9342 @item maint print symbols @var{filename}
9343 @itemx maint print psymbols @var{filename}
9344 @itemx maint print msymbols @var{filename}
9345 Write a dump of debugging symbol data into the file @var{filename}.
9346 These commands are used to debug the @value{GDBN} symbol-reading code. Only
9347 symbols with debugging data are included. If you use @samp{maint print
9348 symbols}, @value{GDBN} includes all the symbols for which it has already
9349 collected full details: that is, @var{filename} reflects symbols for
9350 only those files whose symbols @value{GDBN} has read. You can use the
9351 command @code{info sources} to find out which files these are. If you
9352 use @samp{maint print psymbols} instead, the dump shows information about
9353 symbols that @value{GDBN} only knows partially---that is, symbols defined in
9354 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
9355 @samp{maint print msymbols} dumps just the minimal symbol information
9356 required for each object file from which @value{GDBN} has read some symbols.
9357 @xref{Files, ,Commands to specify files}, for a discussion of how
9358 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
9360 @kindex maint info symtabs
9361 @kindex maint info psymtabs
9362 @cindex listing @value{GDBN}'s internal symbol tables
9363 @cindex symbol tables, listing @value{GDBN}'s internal
9364 @cindex full symbol tables, listing @value{GDBN}'s internal
9365 @cindex partial symbol tables, listing @value{GDBN}'s internal
9366 @item maint info symtabs @r{[} @var{regexp} @r{]}
9367 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
9369 List the @code{struct symtab} or @code{struct partial_symtab}
9370 structures whose names match @var{regexp}. If @var{regexp} is not
9371 given, list them all. The output includes expressions which you can
9372 copy into a @value{GDBN} debugging this one to examine a particular
9373 structure in more detail. For example:
9376 (@value{GDBP}) maint info psymtabs dwarf2read
9377 @{ objfile /home/gnu/build/gdb/gdb
9378 ((struct objfile *) 0x82e69d0)
9379 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
9380 ((struct partial_symtab *) 0x8474b10)
9383 text addresses 0x814d3c8 -- 0x8158074
9384 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
9385 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
9389 (@value{GDBP}) maint info symtabs
9393 We see that there is one partial symbol table whose filename contains
9394 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
9395 and we see that @value{GDBN} has not read in any symtabs yet at all.
9396 If we set a breakpoint on a function, that will cause @value{GDBN} to
9397 read the symtab for the compilation unit containing that function:
9400 (@value{GDBP}) break dwarf2_psymtab_to_symtab
9401 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
9403 (@value{GDBP}) maint info symtabs
9404 @{ objfile /home/gnu/build/gdb/gdb
9405 ((struct objfile *) 0x82e69d0)
9406 @{ symtab /home/gnu/src/gdb/dwarf2read.c
9407 ((struct symtab *) 0x86c1f38)
9410 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
9420 @chapter Altering Execution
9422 Once you think you have found an error in your program, you might want to
9423 find out for certain whether correcting the apparent error would lead to
9424 correct results in the rest of the run. You can find the answer by
9425 experiment, using the @value{GDBN} features for altering execution of the
9428 For example, you can store new values into variables or memory
9429 locations, give your program a signal, restart it at a different
9430 address, or even return prematurely from a function.
9433 * Assignment:: Assignment to variables
9434 * Jumping:: Continuing at a different address
9435 * Signaling:: Giving your program a signal
9436 * Returning:: Returning from a function
9437 * Calling:: Calling your program's functions
9438 * Patching:: Patching your program
9442 @section Assignment to variables
9445 @cindex setting variables
9446 To alter the value of a variable, evaluate an assignment expression.
9447 @xref{Expressions, ,Expressions}. For example,
9454 stores the value 4 into the variable @code{x}, and then prints the
9455 value of the assignment expression (which is 4).
9456 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
9457 information on operators in supported languages.
9459 @kindex set variable
9460 @cindex variables, setting
9461 If you are not interested in seeing the value of the assignment, use the
9462 @code{set} command instead of the @code{print} command. @code{set} is
9463 really the same as @code{print} except that the expression's value is
9464 not printed and is not put in the value history (@pxref{Value History,
9465 ,Value history}). The expression is evaluated only for its effects.
9467 If the beginning of the argument string of the @code{set} command
9468 appears identical to a @code{set} subcommand, use the @code{set
9469 variable} command instead of just @code{set}. This command is identical
9470 to @code{set} except for its lack of subcommands. For example, if your
9471 program has a variable @code{width}, you get an error if you try to set
9472 a new value with just @samp{set width=13}, because @value{GDBN} has the
9473 command @code{set width}:
9476 (@value{GDBP}) whatis width
9478 (@value{GDBP}) p width
9480 (@value{GDBP}) set width=47
9481 Invalid syntax in expression.
9485 The invalid expression, of course, is @samp{=47}. In
9486 order to actually set the program's variable @code{width}, use
9489 (@value{GDBP}) set var width=47
9492 Because the @code{set} command has many subcommands that can conflict
9493 with the names of program variables, it is a good idea to use the
9494 @code{set variable} command instead of just @code{set}. For example, if
9495 your program has a variable @code{g}, you run into problems if you try
9496 to set a new value with just @samp{set g=4}, because @value{GDBN} has
9497 the command @code{set gnutarget}, abbreviated @code{set g}:
9501 (@value{GDBP}) whatis g
9505 (@value{GDBP}) set g=4
9509 The program being debugged has been started already.
9510 Start it from the beginning? (y or n) y
9511 Starting program: /home/smith/cc_progs/a.out
9512 "/home/smith/cc_progs/a.out": can't open to read symbols:
9514 (@value{GDBP}) show g
9515 The current BFD target is "=4".
9520 The program variable @code{g} did not change, and you silently set the
9521 @code{gnutarget} to an invalid value. In order to set the variable
9525 (@value{GDBP}) set var g=4
9528 @value{GDBN} allows more implicit conversions in assignments than C; you can
9529 freely store an integer value into a pointer variable or vice versa,
9530 and you can convert any structure to any other structure that is the
9531 same length or shorter.
9532 @comment FIXME: how do structs align/pad in these conversions?
9533 @comment /doc@cygnus.com 18dec1990
9535 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
9536 construct to generate a value of specified type at a specified address
9537 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
9538 to memory location @code{0x83040} as an integer (which implies a certain size
9539 and representation in memory), and
9542 set @{int@}0x83040 = 4
9546 stores the value 4 into that memory location.
9549 @section Continuing at a different address
9551 Ordinarily, when you continue your program, you do so at the place where
9552 it stopped, with the @code{continue} command. You can instead continue at
9553 an address of your own choosing, with the following commands:
9557 @item jump @var{linespec}
9558 Resume execution at line @var{linespec}. Execution stops again
9559 immediately if there is a breakpoint there. @xref{List, ,Printing
9560 source lines}, for a description of the different forms of
9561 @var{linespec}. It is common practice to use the @code{tbreak} command
9562 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
9565 The @code{jump} command does not change the current stack frame, or
9566 the stack pointer, or the contents of any memory location or any
9567 register other than the program counter. If line @var{linespec} is in
9568 a different function from the one currently executing, the results may
9569 be bizarre if the two functions expect different patterns of arguments or
9570 of local variables. For this reason, the @code{jump} command requests
9571 confirmation if the specified line is not in the function currently
9572 executing. However, even bizarre results are predictable if you are
9573 well acquainted with the machine-language code of your program.
9575 @item jump *@var{address}
9576 Resume execution at the instruction at address @var{address}.
9579 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
9580 On many systems, you can get much the same effect as the @code{jump}
9581 command by storing a new value into the register @code{$pc}. The
9582 difference is that this does not start your program running; it only
9583 changes the address of where it @emph{will} run when you continue. For
9591 makes the next @code{continue} command or stepping command execute at
9592 address @code{0x485}, rather than at the address where your program stopped.
9593 @xref{Continuing and Stepping, ,Continuing and stepping}.
9595 The most common occasion to use the @code{jump} command is to back
9596 up---perhaps with more breakpoints set---over a portion of a program
9597 that has already executed, in order to examine its execution in more
9602 @section Giving your program a signal
9606 @item signal @var{signal}
9607 Resume execution where your program stopped, but immediately give it the
9608 signal @var{signal}. @var{signal} can be the name or the number of a
9609 signal. For example, on many systems @code{signal 2} and @code{signal
9610 SIGINT} are both ways of sending an interrupt signal.
9612 Alternatively, if @var{signal} is zero, continue execution without
9613 giving a signal. This is useful when your program stopped on account of
9614 a signal and would ordinary see the signal when resumed with the
9615 @code{continue} command; @samp{signal 0} causes it to resume without a
9618 @code{signal} does not repeat when you press @key{RET} a second time
9619 after executing the command.
9623 Invoking the @code{signal} command is not the same as invoking the
9624 @code{kill} utility from the shell. Sending a signal with @code{kill}
9625 causes @value{GDBN} to decide what to do with the signal depending on
9626 the signal handling tables (@pxref{Signals}). The @code{signal} command
9627 passes the signal directly to your program.
9631 @section Returning from a function
9634 @cindex returning from a function
9637 @itemx return @var{expression}
9638 You can cancel execution of a function call with the @code{return}
9639 command. If you give an
9640 @var{expression} argument, its value is used as the function's return
9644 When you use @code{return}, @value{GDBN} discards the selected stack frame
9645 (and all frames within it). You can think of this as making the
9646 discarded frame return prematurely. If you wish to specify a value to
9647 be returned, give that value as the argument to @code{return}.
9649 This pops the selected stack frame (@pxref{Selection, ,Selecting a
9650 frame}), and any other frames inside of it, leaving its caller as the
9651 innermost remaining frame. That frame becomes selected. The
9652 specified value is stored in the registers used for returning values
9655 The @code{return} command does not resume execution; it leaves the
9656 program stopped in the state that would exist if the function had just
9657 returned. In contrast, the @code{finish} command (@pxref{Continuing
9658 and Stepping, ,Continuing and stepping}) resumes execution until the
9659 selected stack frame returns naturally.
9662 @section Calling program functions
9664 @cindex calling functions
9667 @item call @var{expr}
9668 Evaluate the expression @var{expr} without displaying @code{void}
9672 You can use this variant of the @code{print} command if you want to
9673 execute a function from your program, but without cluttering the output
9674 with @code{void} returned values. If the result is not void, it
9675 is printed and saved in the value history.
9678 @section Patching programs
9680 @cindex patching binaries
9681 @cindex writing into executables
9682 @cindex writing into corefiles
9684 By default, @value{GDBN} opens the file containing your program's
9685 executable code (or the corefile) read-only. This prevents accidental
9686 alterations to machine code; but it also prevents you from intentionally
9687 patching your program's binary.
9689 If you'd like to be able to patch the binary, you can specify that
9690 explicitly with the @code{set write} command. For example, you might
9691 want to turn on internal debugging flags, or even to make emergency
9697 @itemx set write off
9698 If you specify @samp{set write on}, @value{GDBN} opens executable and
9699 core files for both reading and writing; if you specify @samp{set write
9700 off} (the default), @value{GDBN} opens them read-only.
9702 If you have already loaded a file, you must load it again (using the
9703 @code{exec-file} or @code{core-file} command) after changing @code{set
9704 write}, for your new setting to take effect.
9708 Display whether executable files and core files are opened for writing
9713 @chapter @value{GDBN} Files
9715 @value{GDBN} needs to know the file name of the program to be debugged,
9716 both in order to read its symbol table and in order to start your
9717 program. To debug a core dump of a previous run, you must also tell
9718 @value{GDBN} the name of the core dump file.
9721 * Files:: Commands to specify files
9722 * Separate Debug Files:: Debugging information in separate files
9723 * Symbol Errors:: Errors reading symbol files
9727 @section Commands to specify files
9729 @cindex symbol table
9730 @cindex core dump file
9732 You may want to specify executable and core dump file names. The usual
9733 way to do this is at start-up time, using the arguments to
9734 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
9735 Out of @value{GDBN}}).
9737 Occasionally it is necessary to change to a different file during a
9738 @value{GDBN} session. Or you may run @value{GDBN} and forget to specify
9739 a file you want to use. In these situations the @value{GDBN} commands
9740 to specify new files are useful.
9743 @cindex executable file
9745 @item file @var{filename}
9746 Use @var{filename} as the program to be debugged. It is read for its
9747 symbols and for the contents of pure memory. It is also the program
9748 executed when you use the @code{run} command. If you do not specify a
9749 directory and the file is not found in the @value{GDBN} working directory,
9750 @value{GDBN} uses the environment variable @code{PATH} as a list of
9751 directories to search, just as the shell does when looking for a program
9752 to run. You can change the value of this variable, for both @value{GDBN}
9753 and your program, using the @code{path} command.
9755 On systems with memory-mapped files, an auxiliary file named
9756 @file{@var{filename}.syms} may hold symbol table information for
9757 @var{filename}. If so, @value{GDBN} maps in the symbol table from
9758 @file{@var{filename}.syms}, starting up more quickly. See the
9759 descriptions of the file options @samp{-mapped} and @samp{-readnow}
9760 (available on the command line, and with the commands @code{file},
9761 @code{symbol-file}, or @code{add-symbol-file}, described below),
9762 for more information.
9765 @code{file} with no argument makes @value{GDBN} discard any information it
9766 has on both executable file and the symbol table.
9769 @item exec-file @r{[} @var{filename} @r{]}
9770 Specify that the program to be run (but not the symbol table) is found
9771 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
9772 if necessary to locate your program. Omitting @var{filename} means to
9773 discard information on the executable file.
9776 @item symbol-file @r{[} @var{filename} @r{]}
9777 Read symbol table information from file @var{filename}. @code{PATH} is
9778 searched when necessary. Use the @code{file} command to get both symbol
9779 table and program to run from the same file.
9781 @code{symbol-file} with no argument clears out @value{GDBN} information on your
9782 program's symbol table.
9784 The @code{symbol-file} command causes @value{GDBN} to forget the contents
9785 of its convenience variables, the value history, and all breakpoints and
9786 auto-display expressions. This is because they may contain pointers to
9787 the internal data recording symbols and data types, which are part of
9788 the old symbol table data being discarded inside @value{GDBN}.
9790 @code{symbol-file} does not repeat if you press @key{RET} again after
9793 When @value{GDBN} is configured for a particular environment, it
9794 understands debugging information in whatever format is the standard
9795 generated for that environment; you may use either a @sc{gnu} compiler, or
9796 other compilers that adhere to the local conventions.
9797 Best results are usually obtained from @sc{gnu} compilers; for example,
9798 using @code{@value{GCC}} you can generate debugging information for
9801 For most kinds of object files, with the exception of old SVR3 systems
9802 using COFF, the @code{symbol-file} command does not normally read the
9803 symbol table in full right away. Instead, it scans the symbol table
9804 quickly to find which source files and which symbols are present. The
9805 details are read later, one source file at a time, as they are needed.
9807 The purpose of this two-stage reading strategy is to make @value{GDBN}
9808 start up faster. For the most part, it is invisible except for
9809 occasional pauses while the symbol table details for a particular source
9810 file are being read. (The @code{set verbose} command can turn these
9811 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
9812 warnings and messages}.)
9814 We have not implemented the two-stage strategy for COFF yet. When the
9815 symbol table is stored in COFF format, @code{symbol-file} reads the
9816 symbol table data in full right away. Note that ``stabs-in-COFF''
9817 still does the two-stage strategy, since the debug info is actually
9821 @cindex reading symbols immediately
9822 @cindex symbols, reading immediately
9824 @cindex memory-mapped symbol file
9825 @cindex saving symbol table
9826 @item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9827 @itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9828 You can override the @value{GDBN} two-stage strategy for reading symbol
9829 tables by using the @samp{-readnow} option with any of the commands that
9830 load symbol table information, if you want to be sure @value{GDBN} has the
9831 entire symbol table available.
9833 If memory-mapped files are available on your system through the
9834 @code{mmap} system call, you can use another option, @samp{-mapped}, to
9835 cause @value{GDBN} to write the symbols for your program into a reusable
9836 file. Future @value{GDBN} debugging sessions map in symbol information
9837 from this auxiliary symbol file (if the program has not changed), rather
9838 than spending time reading the symbol table from the executable
9839 program. Using the @samp{-mapped} option has the same effect as
9840 starting @value{GDBN} with the @samp{-mapped} command-line option.
9842 You can use both options together, to make sure the auxiliary symbol
9843 file has all the symbol information for your program.
9845 The auxiliary symbol file for a program called @var{myprog} is called
9846 @samp{@var{myprog}.syms}. Once this file exists (so long as it is newer
9847 than the corresponding executable), @value{GDBN} always attempts to use
9848 it when you debug @var{myprog}; no special options or commands are
9851 The @file{.syms} file is specific to the host machine where you run
9852 @value{GDBN}. It holds an exact image of the internal @value{GDBN}
9853 symbol table. It cannot be shared across multiple host platforms.
9855 @c FIXME: for now no mention of directories, since this seems to be in
9856 @c flux. 13mar1992 status is that in theory GDB would look either in
9857 @c current dir or in same dir as myprog; but issues like competing
9858 @c GDB's, or clutter in system dirs, mean that in practice right now
9859 @c only current dir is used. FFish says maybe a special GDB hierarchy
9860 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
9865 @item core-file @r{[} @var{filename} @r{]}
9866 Specify the whereabouts of a core dump file to be used as the ``contents
9867 of memory''. Traditionally, core files contain only some parts of the
9868 address space of the process that generated them; @value{GDBN} can access the
9869 executable file itself for other parts.
9871 @code{core-file} with no argument specifies that no core file is
9874 Note that the core file is ignored when your program is actually running
9875 under @value{GDBN}. So, if you have been running your program and you
9876 wish to debug a core file instead, you must kill the subprocess in which
9877 the program is running. To do this, use the @code{kill} command
9878 (@pxref{Kill Process, ,Killing the child process}).
9880 @kindex add-symbol-file
9881 @cindex dynamic linking
9882 @item add-symbol-file @var{filename} @var{address}
9883 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9884 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
9885 The @code{add-symbol-file} command reads additional symbol table
9886 information from the file @var{filename}. You would use this command
9887 when @var{filename} has been dynamically loaded (by some other means)
9888 into the program that is running. @var{address} should be the memory
9889 address at which the file has been loaded; @value{GDBN} cannot figure
9890 this out for itself. You can additionally specify an arbitrary number
9891 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
9892 section name and base address for that section. You can specify any
9893 @var{address} as an expression.
9895 The symbol table of the file @var{filename} is added to the symbol table
9896 originally read with the @code{symbol-file} command. You can use the
9897 @code{add-symbol-file} command any number of times; the new symbol data
9898 thus read keeps adding to the old. To discard all old symbol data
9899 instead, use the @code{symbol-file} command without any arguments.
9901 @cindex relocatable object files, reading symbols from
9902 @cindex object files, relocatable, reading symbols from
9903 @cindex reading symbols from relocatable object files
9904 @cindex symbols, reading from relocatable object files
9905 @cindex @file{.o} files, reading symbols from
9906 Although @var{filename} is typically a shared library file, an
9907 executable file, or some other object file which has been fully
9908 relocated for loading into a process, you can also load symbolic
9909 information from relocatable @file{.o} files, as long as:
9913 the file's symbolic information refers only to linker symbols defined in
9914 that file, not to symbols defined by other object files,
9916 every section the file's symbolic information refers to has actually
9917 been loaded into the inferior, as it appears in the file, and
9919 you can determine the address at which every section was loaded, and
9920 provide these to the @code{add-symbol-file} command.
9924 Some embedded operating systems, like Sun Chorus and VxWorks, can load
9925 relocatable files into an already running program; such systems
9926 typically make the requirements above easy to meet. However, it's
9927 important to recognize that many native systems use complex link
9928 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
9929 assembly, for example) that make the requirements difficult to meet. In
9930 general, one cannot assume that using @code{add-symbol-file} to read a
9931 relocatable object file's symbolic information will have the same effect
9932 as linking the relocatable object file into the program in the normal
9935 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
9937 You can use the @samp{-mapped} and @samp{-readnow} options just as with
9938 the @code{symbol-file} command, to change how @value{GDBN} manages the symbol
9939 table information for @var{filename}.
9941 @kindex add-shared-symbol-file
9942 @item add-shared-symbol-file
9943 The @code{add-shared-symbol-file} command can be used only under Harris' CXUX
9944 operating system for the Motorola 88k. @value{GDBN} automatically looks for
9945 shared libraries, however if @value{GDBN} does not find yours, you can run
9946 @code{add-shared-symbol-file}. It takes no arguments.
9950 The @code{section} command changes the base address of section SECTION of
9951 the exec file to ADDR. This can be used if the exec file does not contain
9952 section addresses, (such as in the a.out format), or when the addresses
9953 specified in the file itself are wrong. Each section must be changed
9954 separately. The @code{info files} command, described below, lists all
9955 the sections and their addresses.
9961 @code{info files} and @code{info target} are synonymous; both print the
9962 current target (@pxref{Targets, ,Specifying a Debugging Target}),
9963 including the names of the executable and core dump files currently in
9964 use by @value{GDBN}, and the files from which symbols were loaded. The
9965 command @code{help target} lists all possible targets rather than
9968 @kindex maint info sections
9969 @item maint info sections
9970 Another command that can give you extra information about program sections
9971 is @code{maint info sections}. In addition to the section information
9972 displayed by @code{info files}, this command displays the flags and file
9973 offset of each section in the executable and core dump files. In addition,
9974 @code{maint info sections} provides the following command options (which
9975 may be arbitrarily combined):
9979 Display sections for all loaded object files, including shared libraries.
9980 @item @var{sections}
9981 Display info only for named @var{sections}.
9982 @item @var{section-flags}
9983 Display info only for sections for which @var{section-flags} are true.
9984 The section flags that @value{GDBN} currently knows about are:
9987 Section will have space allocated in the process when loaded.
9988 Set for all sections except those containing debug information.
9990 Section will be loaded from the file into the child process memory.
9991 Set for pre-initialized code and data, clear for @code{.bss} sections.
9993 Section needs to be relocated before loading.
9995 Section cannot be modified by the child process.
9997 Section contains executable code only.
9999 Section contains data only (no executable code).
10001 Section will reside in ROM.
10003 Section contains data for constructor/destructor lists.
10005 Section is not empty.
10007 An instruction to the linker to not output the section.
10008 @item COFF_SHARED_LIBRARY
10009 A notification to the linker that the section contains
10010 COFF shared library information.
10012 Section contains common symbols.
10015 @kindex set trust-readonly-sections
10016 @item set trust-readonly-sections on
10017 Tell @value{GDBN} that readonly sections in your object file
10018 really are read-only (i.e.@: that their contents will not change).
10019 In that case, @value{GDBN} can fetch values from these sections
10020 out of the object file, rather than from the target program.
10021 For some targets (notably embedded ones), this can be a significant
10022 enhancement to debugging performance.
10024 The default is off.
10026 @item set trust-readonly-sections off
10027 Tell @value{GDBN} not to trust readonly sections. This means that
10028 the contents of the section might change while the program is running,
10029 and must therefore be fetched from the target when needed.
10032 All file-specifying commands allow both absolute and relative file names
10033 as arguments. @value{GDBN} always converts the file name to an absolute file
10034 name and remembers it that way.
10036 @cindex shared libraries
10037 @value{GDBN} supports HP-UX, SunOS, SVr4, Irix 5, and IBM RS/6000 shared
10040 @value{GDBN} automatically loads symbol definitions from shared libraries
10041 when you use the @code{run} command, or when you examine a core file.
10042 (Before you issue the @code{run} command, @value{GDBN} does not understand
10043 references to a function in a shared library, however---unless you are
10044 debugging a core file).
10046 On HP-UX, if the program loads a library explicitly, @value{GDBN}
10047 automatically loads the symbols at the time of the @code{shl_load} call.
10049 @c FIXME: some @value{GDBN} release may permit some refs to undef
10050 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
10051 @c FIXME...lib; check this from time to time when updating manual
10053 There are times, however, when you may wish to not automatically load
10054 symbol definitions from shared libraries, such as when they are
10055 particularly large or there are many of them.
10057 To control the automatic loading of shared library symbols, use the
10061 @kindex set auto-solib-add
10062 @item set auto-solib-add @var{mode}
10063 If @var{mode} is @code{on}, symbols from all shared object libraries
10064 will be loaded automatically when the inferior begins execution, you
10065 attach to an independently started inferior, or when the dynamic linker
10066 informs @value{GDBN} that a new library has been loaded. If @var{mode}
10067 is @code{off}, symbols must be loaded manually, using the
10068 @code{sharedlibrary} command. The default value is @code{on}.
10070 @kindex show auto-solib-add
10071 @item show auto-solib-add
10072 Display the current autoloading mode.
10075 To explicitly load shared library symbols, use the @code{sharedlibrary}
10079 @kindex info sharedlibrary
10082 @itemx info sharedlibrary
10083 Print the names of the shared libraries which are currently loaded.
10085 @kindex sharedlibrary
10087 @item sharedlibrary @var{regex}
10088 @itemx share @var{regex}
10089 Load shared object library symbols for files matching a
10090 Unix regular expression.
10091 As with files loaded automatically, it only loads shared libraries
10092 required by your program for a core file or after typing @code{run}. If
10093 @var{regex} is omitted all shared libraries required by your program are
10097 On some systems, such as HP-UX systems, @value{GDBN} supports
10098 autoloading shared library symbols until a limiting threshold size is
10099 reached. This provides the benefit of allowing autoloading to remain on
10100 by default, but avoids autoloading excessively large shared libraries,
10101 up to a threshold that is initially set, but which you can modify if you
10104 Beyond that threshold, symbols from shared libraries must be explicitly
10105 loaded. To load these symbols, use the command @code{sharedlibrary
10106 @var{filename}}. The base address of the shared library is determined
10107 automatically by @value{GDBN} and need not be specified.
10109 To display or set the threshold, use the commands:
10112 @kindex set auto-solib-limit
10113 @item set auto-solib-limit @var{threshold}
10114 Set the autoloading size threshold, in an integral number of megabytes.
10115 If @var{threshold} is nonzero and shared library autoloading is enabled,
10116 symbols from all shared object libraries will be loaded until the total
10117 size of the loaded shared library symbols exceeds this threshold.
10118 Otherwise, symbols must be loaded manually, using the
10119 @code{sharedlibrary} command. The default threshold is 100 (i.e.@: 100
10122 @kindex show auto-solib-limit
10123 @item show auto-solib-limit
10124 Display the current autoloading size threshold, in megabytes.
10127 Shared libraries are also supported in many cross or remote debugging
10128 configurations. A copy of the target's libraries need to be present on the
10129 host system; they need to be the same as the target libraries, although the
10130 copies on the target can be stripped as long as the copies on the host are
10133 You need to tell @value{GDBN} where the target libraries are, so that it can
10134 load the correct copies---otherwise, it may try to load the host's libraries.
10135 @value{GDBN} has two variables to specify the search directories for target
10139 @kindex set solib-absolute-prefix
10140 @item set solib-absolute-prefix @var{path}
10141 If this variable is set, @var{path} will be used as a prefix for any
10142 absolute shared library paths; many runtime loaders store the absolute
10143 paths to the shared library in the target program's memory. If you use
10144 @samp{solib-absolute-prefix} to find shared libraries, they need to be laid
10145 out in the same way that they are on the target, with e.g.@: a
10146 @file{/usr/lib} hierarchy under @var{path}.
10148 You can set the default value of @samp{solib-absolute-prefix} by using the
10149 configure-time @samp{--with-sysroot} option.
10151 @kindex show solib-absolute-prefix
10152 @item show solib-absolute-prefix
10153 Display the current shared library prefix.
10155 @kindex set solib-search-path
10156 @item set solib-search-path @var{path}
10157 If this variable is set, @var{path} is a colon-separated list of directories
10158 to search for shared libraries. @samp{solib-search-path} is used after
10159 @samp{solib-absolute-prefix} fails to locate the library, or if the path to
10160 the library is relative instead of absolute. If you want to use
10161 @samp{solib-search-path} instead of @samp{solib-absolute-prefix}, be sure to
10162 set @samp{solib-absolute-prefix} to a nonexistant directory to prevent
10163 @value{GDBN} from finding your host's libraries.
10165 @kindex show solib-search-path
10166 @item show solib-search-path
10167 Display the current shared library search path.
10171 @node Separate Debug Files
10172 @section Debugging Information in Separate Files
10173 @cindex separate debugging information files
10174 @cindex debugging information in separate files
10175 @cindex @file{.debug} subdirectories
10176 @cindex debugging information directory, global
10177 @cindex global debugging information directory
10179 @value{GDBN} allows you to put a program's debugging information in a
10180 file separate from the executable itself, in a way that allows
10181 @value{GDBN} to find and load the debugging information automatically.
10182 Since debugging information can be very large --- sometimes larger
10183 than the executable code itself --- some systems distribute debugging
10184 information for their executables in separate files, which users can
10185 install only when they need to debug a problem.
10187 If an executable's debugging information has been extracted to a
10188 separate file, the executable should contain a @dfn{debug link} giving
10189 the name of the debugging information file (with no directory
10190 components), and a checksum of its contents. (The exact form of a
10191 debug link is described below.) If the full name of the directory
10192 containing the executable is @var{execdir}, and the executable has a
10193 debug link that specifies the name @var{debugfile}, then @value{GDBN}
10194 will automatically search for the debugging information file in three
10199 the directory containing the executable file (that is, it will look
10200 for a file named @file{@var{execdir}/@var{debugfile}},
10202 a subdirectory of that directory named @file{.debug} (that is, the
10203 file @file{@var{execdir}/.debug/@var{debugfile}}, and
10205 a subdirectory of the global debug file directory that includes the
10206 executable's full path, and the name from the link (that is, the file
10207 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
10208 @var{globaldebugdir} is the global debug file directory, and
10209 @var{execdir} has been turned into a relative path).
10212 @value{GDBN} checks under each of these names for a debugging
10213 information file whose checksum matches that given in the link, and
10214 reads the debugging information from the first one it finds.
10216 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
10217 which has a link containing the name @file{ls.debug}, and the global
10218 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
10219 for debug information in @file{/usr/bin/ls.debug},
10220 @file{/usr/bin/.debug/ls.debug}, and
10221 @file{/usr/lib/debug/usr/bin/ls.debug}.
10223 You can set the global debugging info directory's name, and view the
10224 name @value{GDBN} is currently using.
10228 @kindex set debug-file-directory
10229 @item set debug-file-directory @var{directory}
10230 Set the directory which @value{GDBN} searches for separate debugging
10231 information files to @var{directory}.
10233 @kindex show debug-file-directory
10234 @item show debug-file-directory
10235 Show the directory @value{GDBN} searches for separate debugging
10240 @cindex @code{.gnu_debuglink} sections
10241 @cindex debug links
10242 A debug link is a special section of the executable file named
10243 @code{.gnu_debuglink}. The section must contain:
10247 A filename, with any leading directory components removed, followed by
10250 zero to three bytes of padding, as needed to reach the next four-byte
10251 boundary within the section, and
10253 a four-byte CRC checksum, stored in the same endianness used for the
10254 executable file itself. The checksum is computed on the debugging
10255 information file's full contents by the function given below, passing
10256 zero as the @var{crc} argument.
10259 Any executable file format can carry a debug link, as long as it can
10260 contain a section named @code{.gnu_debuglink} with the contents
10263 The debugging information file itself should be an ordinary
10264 executable, containing a full set of linker symbols, sections, and
10265 debugging information. The sections of the debugging information file
10266 should have the same names, addresses and sizes as the original file,
10267 but they need not contain any data --- much like a @code{.bss} section
10268 in an ordinary executable.
10270 As of December 2002, there is no standard GNU utility to produce
10271 separated executable / debugging information file pairs. Ulrich
10272 Drepper's @file{elfutils} package, starting with version 0.53,
10273 contains a version of the @code{strip} command such that the command
10274 @kbd{strip foo -f foo.debug} removes the debugging information from
10275 the executable file @file{foo}, places it in the file
10276 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
10278 Since there are many different ways to compute CRC's (different
10279 polynomials, reversals, byte ordering, etc.), the simplest way to
10280 describe the CRC used in @code{.gnu_debuglink} sections is to give the
10281 complete code for a function that computes it:
10283 @kindex @code{gnu_debuglink_crc32}
10286 gnu_debuglink_crc32 (unsigned long crc,
10287 unsigned char *buf, size_t len)
10289 static const unsigned long crc32_table[256] =
10291 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
10292 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
10293 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
10294 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
10295 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
10296 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
10297 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
10298 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
10299 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
10300 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
10301 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
10302 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
10303 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
10304 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
10305 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
10306 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
10307 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
10308 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
10309 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
10310 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
10311 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
10312 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
10313 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
10314 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
10315 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
10316 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
10317 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
10318 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
10319 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
10320 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
10321 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
10322 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
10323 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
10324 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
10325 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
10326 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
10327 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
10328 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
10329 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
10330 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
10331 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
10332 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
10333 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
10334 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
10335 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
10336 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
10337 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
10338 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
10339 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
10340 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
10341 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
10344 unsigned char *end;
10346 crc = ~crc & 0xffffffff;
10347 for (end = buf + len; buf < end; ++buf)
10348 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
10349 return ~crc & 0xffffffff;
10354 @node Symbol Errors
10355 @section Errors reading symbol files
10357 While reading a symbol file, @value{GDBN} occasionally encounters problems,
10358 such as symbol types it does not recognize, or known bugs in compiler
10359 output. By default, @value{GDBN} does not notify you of such problems, since
10360 they are relatively common and primarily of interest to people
10361 debugging compilers. If you are interested in seeing information
10362 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
10363 only one message about each such type of problem, no matter how many
10364 times the problem occurs; or you can ask @value{GDBN} to print more messages,
10365 to see how many times the problems occur, with the @code{set
10366 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
10369 The messages currently printed, and their meanings, include:
10372 @item inner block not inside outer block in @var{symbol}
10374 The symbol information shows where symbol scopes begin and end
10375 (such as at the start of a function or a block of statements). This
10376 error indicates that an inner scope block is not fully contained
10377 in its outer scope blocks.
10379 @value{GDBN} circumvents the problem by treating the inner block as if it had
10380 the same scope as the outer block. In the error message, @var{symbol}
10381 may be shown as ``@code{(don't know)}'' if the outer block is not a
10384 @item block at @var{address} out of order
10386 The symbol information for symbol scope blocks should occur in
10387 order of increasing addresses. This error indicates that it does not
10390 @value{GDBN} does not circumvent this problem, and has trouble
10391 locating symbols in the source file whose symbols it is reading. (You
10392 can often determine what source file is affected by specifying
10393 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
10396 @item bad block start address patched
10398 The symbol information for a symbol scope block has a start address
10399 smaller than the address of the preceding source line. This is known
10400 to occur in the SunOS 4.1.1 (and earlier) C compiler.
10402 @value{GDBN} circumvents the problem by treating the symbol scope block as
10403 starting on the previous source line.
10405 @item bad string table offset in symbol @var{n}
10408 Symbol number @var{n} contains a pointer into the string table which is
10409 larger than the size of the string table.
10411 @value{GDBN} circumvents the problem by considering the symbol to have the
10412 name @code{foo}, which may cause other problems if many symbols end up
10415 @item unknown symbol type @code{0x@var{nn}}
10417 The symbol information contains new data types that @value{GDBN} does
10418 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
10419 uncomprehended information, in hexadecimal.
10421 @value{GDBN} circumvents the error by ignoring this symbol information.
10422 This usually allows you to debug your program, though certain symbols
10423 are not accessible. If you encounter such a problem and feel like
10424 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
10425 on @code{complain}, then go up to the function @code{read_dbx_symtab}
10426 and examine @code{*bufp} to see the symbol.
10428 @item stub type has NULL name
10430 @value{GDBN} could not find the full definition for a struct or class.
10432 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
10433 The symbol information for a C@t{++} member function is missing some
10434 information that recent versions of the compiler should have output for
10437 @item info mismatch between compiler and debugger
10439 @value{GDBN} could not parse a type specification output by the compiler.
10444 @chapter Specifying a Debugging Target
10446 @cindex debugging target
10449 A @dfn{target} is the execution environment occupied by your program.
10451 Often, @value{GDBN} runs in the same host environment as your program;
10452 in that case, the debugging target is specified as a side effect when
10453 you use the @code{file} or @code{core} commands. When you need more
10454 flexibility---for example, running @value{GDBN} on a physically separate
10455 host, or controlling a standalone system over a serial port or a
10456 realtime system over a TCP/IP connection---you can use the @code{target}
10457 command to specify one of the target types configured for @value{GDBN}
10458 (@pxref{Target Commands, ,Commands for managing targets}).
10461 * Active Targets:: Active targets
10462 * Target Commands:: Commands for managing targets
10463 * Byte Order:: Choosing target byte order
10464 * Remote:: Remote debugging
10465 * KOD:: Kernel Object Display
10469 @node Active Targets
10470 @section Active targets
10472 @cindex stacking targets
10473 @cindex active targets
10474 @cindex multiple targets
10476 There are three classes of targets: processes, core files, and
10477 executable files. @value{GDBN} can work concurrently on up to three
10478 active targets, one in each class. This allows you to (for example)
10479 start a process and inspect its activity without abandoning your work on
10482 For example, if you execute @samp{gdb a.out}, then the executable file
10483 @code{a.out} is the only active target. If you designate a core file as
10484 well---presumably from a prior run that crashed and coredumped---then
10485 @value{GDBN} has two active targets and uses them in tandem, looking
10486 first in the corefile target, then in the executable file, to satisfy
10487 requests for memory addresses. (Typically, these two classes of target
10488 are complementary, since core files contain only a program's
10489 read-write memory---variables and so on---plus machine status, while
10490 executable files contain only the program text and initialized data.)
10492 When you type @code{run}, your executable file becomes an active process
10493 target as well. When a process target is active, all @value{GDBN}
10494 commands requesting memory addresses refer to that target; addresses in
10495 an active core file or executable file target are obscured while the
10496 process target is active.
10498 Use the @code{core-file} and @code{exec-file} commands to select a new
10499 core file or executable target (@pxref{Files, ,Commands to specify
10500 files}). To specify as a target a process that is already running, use
10501 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
10504 @node Target Commands
10505 @section Commands for managing targets
10508 @item target @var{type} @var{parameters}
10509 Connects the @value{GDBN} host environment to a target machine or
10510 process. A target is typically a protocol for talking to debugging
10511 facilities. You use the argument @var{type} to specify the type or
10512 protocol of the target machine.
10514 Further @var{parameters} are interpreted by the target protocol, but
10515 typically include things like device names or host names to connect
10516 with, process numbers, and baud rates.
10518 The @code{target} command does not repeat if you press @key{RET} again
10519 after executing the command.
10521 @kindex help target
10523 Displays the names of all targets available. To display targets
10524 currently selected, use either @code{info target} or @code{info files}
10525 (@pxref{Files, ,Commands to specify files}).
10527 @item help target @var{name}
10528 Describe a particular target, including any parameters necessary to
10531 @kindex set gnutarget
10532 @item set gnutarget @var{args}
10533 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
10534 knows whether it is reading an @dfn{executable},
10535 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
10536 with the @code{set gnutarget} command. Unlike most @code{target} commands,
10537 with @code{gnutarget} the @code{target} refers to a program, not a machine.
10540 @emph{Warning:} To specify a file format with @code{set gnutarget},
10541 you must know the actual BFD name.
10545 @xref{Files, , Commands to specify files}.
10547 @kindex show gnutarget
10548 @item show gnutarget
10549 Use the @code{show gnutarget} command to display what file format
10550 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
10551 @value{GDBN} will determine the file format for each file automatically,
10552 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
10555 Here are some common targets (available, or not, depending on the GDB
10559 @kindex target exec
10560 @item target exec @var{program}
10561 An executable file. @samp{target exec @var{program}} is the same as
10562 @samp{exec-file @var{program}}.
10564 @kindex target core
10565 @item target core @var{filename}
10566 A core dump file. @samp{target core @var{filename}} is the same as
10567 @samp{core-file @var{filename}}.
10569 @kindex target remote
10570 @item target remote @var{dev}
10571 Remote serial target in GDB-specific protocol. The argument @var{dev}
10572 specifies what serial device to use for the connection (e.g.
10573 @file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote}
10574 supports the @code{load} command. This is only useful if you have
10575 some other way of getting the stub to the target system, and you can put
10576 it somewhere in memory where it won't get clobbered by the download.
10580 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
10588 works; however, you cannot assume that a specific memory map, device
10589 drivers, or even basic I/O is available, although some simulators do
10590 provide these. For info about any processor-specific simulator details,
10591 see the appropriate section in @ref{Embedded Processors, ,Embedded
10596 Some configurations may include these targets as well:
10600 @kindex target nrom
10601 @item target nrom @var{dev}
10602 NetROM ROM emulator. This target only supports downloading.
10606 Different targets are available on different configurations of @value{GDBN};
10607 your configuration may have more or fewer targets.
10609 Many remote targets require you to download the executable's code
10610 once you've successfully established a connection.
10614 @kindex load @var{filename}
10615 @item load @var{filename}
10616 Depending on what remote debugging facilities are configured into
10617 @value{GDBN}, the @code{load} command may be available. Where it exists, it
10618 is meant to make @var{filename} (an executable) available for debugging
10619 on the remote system---by downloading, or dynamic linking, for example.
10620 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
10621 the @code{add-symbol-file} command.
10623 If your @value{GDBN} does not have a @code{load} command, attempting to
10624 execute it gets the error message ``@code{You can't do that when your
10625 target is @dots{}}''
10627 The file is loaded at whatever address is specified in the executable.
10628 For some object file formats, you can specify the load address when you
10629 link the program; for other formats, like a.out, the object file format
10630 specifies a fixed address.
10631 @c FIXME! This would be a good place for an xref to the GNU linker doc.
10633 @code{load} does not repeat if you press @key{RET} again after using it.
10637 @section Choosing target byte order
10639 @cindex choosing target byte order
10640 @cindex target byte order
10642 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
10643 offer the ability to run either big-endian or little-endian byte
10644 orders. Usually the executable or symbol will include a bit to
10645 designate the endian-ness, and you will not need to worry about
10646 which to use. However, you may still find it useful to adjust
10647 @value{GDBN}'s idea of processor endian-ness manually.
10650 @kindex set endian big
10651 @item set endian big
10652 Instruct @value{GDBN} to assume the target is big-endian.
10654 @kindex set endian little
10655 @item set endian little
10656 Instruct @value{GDBN} to assume the target is little-endian.
10658 @kindex set endian auto
10659 @item set endian auto
10660 Instruct @value{GDBN} to use the byte order associated with the
10664 Display @value{GDBN}'s current idea of the target byte order.
10668 Note that these commands merely adjust interpretation of symbolic
10669 data on the host, and that they have absolutely no effect on the
10673 @section Remote debugging
10674 @cindex remote debugging
10676 If you are trying to debug a program running on a machine that cannot run
10677 @value{GDBN} in the usual way, it is often useful to use remote debugging.
10678 For example, you might use remote debugging on an operating system kernel,
10679 or on a small system which does not have a general purpose operating system
10680 powerful enough to run a full-featured debugger.
10682 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
10683 to make this work with particular debugging targets. In addition,
10684 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
10685 but not specific to any particular target system) which you can use if you
10686 write the remote stubs---the code that runs on the remote system to
10687 communicate with @value{GDBN}.
10689 Other remote targets may be available in your
10690 configuration of @value{GDBN}; use @code{help target} to list them.
10693 @section Kernel Object Display
10694 @cindex kernel object display
10697 Some targets support kernel object display. Using this facility,
10698 @value{GDBN} communicates specially with the underlying operating system
10699 and can display information about operating system-level objects such as
10700 mutexes and other synchronization objects. Exactly which objects can be
10701 displayed is determined on a per-OS basis.
10704 Use the @code{set os} command to set the operating system. This tells
10705 @value{GDBN} which kernel object display module to initialize:
10708 (@value{GDBP}) set os cisco
10712 The associated command @code{show os} displays the operating system
10713 set with the @code{set os} command; if no operating system has been
10714 set, @code{show os} will display an empty string @samp{""}.
10716 If @code{set os} succeeds, @value{GDBN} will display some information
10717 about the operating system, and will create a new @code{info} command
10718 which can be used to query the target. The @code{info} command is named
10719 after the operating system:
10723 (@value{GDBP}) info cisco
10724 List of Cisco Kernel Objects
10726 any Any and all objects
10729 Further subcommands can be used to query about particular objects known
10732 There is currently no way to determine whether a given operating
10733 system is supported other than to try setting it with @kbd{set os
10734 @var{name}}, where @var{name} is the name of the operating system you
10738 @node Remote Debugging
10739 @chapter Debugging remote programs
10742 * Connecting:: Connecting to a remote target
10743 * Server:: Using the gdbserver program
10744 * NetWare:: Using the gdbserve.nlm program
10745 * Remote configuration:: Remote configuration
10746 * remote stub:: Implementing a remote stub
10750 @section Connecting to a remote target
10752 On the @value{GDBN} host machine, you will need an unstripped copy of
10753 your program, since @value{GDBN} needs symobl and debugging information.
10754 Start up @value{GDBN} as usual, using the name of the local copy of your
10755 program as the first argument.
10757 @cindex serial line, @code{target remote}
10758 If you're using a serial line, you may want to give @value{GDBN} the
10759 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
10760 before the @code{target} command.
10762 After that, use @code{target remote} to establish communications with
10763 the target machine. Its argument specifies how to communicate---either
10764 via a devicename attached to a direct serial line, or a TCP or UDP port
10765 (possibly to a terminal server which in turn has a serial line to the
10766 target). For example, to use a serial line connected to the device
10767 named @file{/dev/ttyb}:
10770 target remote /dev/ttyb
10773 @cindex TCP port, @code{target remote}
10774 To use a TCP connection, use an argument of the form
10775 @code{@var{host}:@var{port}} or @code{tcp:@var{host}:@var{port}}.
10776 For example, to connect to port 2828 on a
10777 terminal server named @code{manyfarms}:
10780 target remote manyfarms:2828
10783 If your remote target is actually running on the same machine as
10784 your debugger session (e.g.@: a simulator of your target running on
10785 the same host), you can omit the hostname. For example, to connect
10786 to port 1234 on your local machine:
10789 target remote :1234
10793 Note that the colon is still required here.
10795 @cindex UDP port, @code{target remote}
10796 To use a UDP connection, use an argument of the form
10797 @code{udp:@var{host}:@var{port}}. For example, to connect to UDP port 2828
10798 on a terminal server named @code{manyfarms}:
10801 target remote udp:manyfarms:2828
10804 When using a UDP connection for remote debugging, you should keep in mind
10805 that the `U' stands for ``Unreliable''. UDP can silently drop packets on
10806 busy or unreliable networks, which will cause havoc with your debugging
10809 Now you can use all the usual commands to examine and change data and to
10810 step and continue the remote program.
10812 @cindex interrupting remote programs
10813 @cindex remote programs, interrupting
10814 Whenever @value{GDBN} is waiting for the remote program, if you type the
10815 interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
10816 program. This may or may not succeed, depending in part on the hardware
10817 and the serial drivers the remote system uses. If you type the
10818 interrupt character once again, @value{GDBN} displays this prompt:
10821 Interrupted while waiting for the program.
10822 Give up (and stop debugging it)? (y or n)
10825 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
10826 (If you decide you want to try again later, you can use @samp{target
10827 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
10828 goes back to waiting.
10831 @kindex detach (remote)
10833 When you have finished debugging the remote program, you can use the
10834 @code{detach} command to release it from @value{GDBN} control.
10835 Detaching from the target normally resumes its execution, but the results
10836 will depend on your particular remote stub. After the @code{detach}
10837 command, @value{GDBN} is free to connect to another target.
10841 The @code{disconnect} command behaves like @code{detach}, except that
10842 the target is generally not resumed. It will wait for @value{GDBN}
10843 (this instance or another one) to connect and continue debugging. After
10844 the @code{disconnect} command, @value{GDBN} is again free to connect to
10849 @section Using the @code{gdbserver} program
10852 @cindex remote connection without stubs
10853 @code{gdbserver} is a control program for Unix-like systems, which
10854 allows you to connect your program with a remote @value{GDBN} via
10855 @code{target remote}---but without linking in the usual debugging stub.
10857 @code{gdbserver} is not a complete replacement for the debugging stubs,
10858 because it requires essentially the same operating-system facilities
10859 that @value{GDBN} itself does. In fact, a system that can run
10860 @code{gdbserver} to connect to a remote @value{GDBN} could also run
10861 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
10862 because it is a much smaller program than @value{GDBN} itself. It is
10863 also easier to port than all of @value{GDBN}, so you may be able to get
10864 started more quickly on a new system by using @code{gdbserver}.
10865 Finally, if you develop code for real-time systems, you may find that
10866 the tradeoffs involved in real-time operation make it more convenient to
10867 do as much development work as possible on another system, for example
10868 by cross-compiling. You can use @code{gdbserver} to make a similar
10869 choice for debugging.
10871 @value{GDBN} and @code{gdbserver} communicate via either a serial line
10872 or a TCP connection, using the standard @value{GDBN} remote serial
10876 @item On the target machine,
10877 you need to have a copy of the program you want to debug.
10878 @code{gdbserver} does not need your program's symbol table, so you can
10879 strip the program if necessary to save space. @value{GDBN} on the host
10880 system does all the symbol handling.
10882 To use the server, you must tell it how to communicate with @value{GDBN};
10883 the name of your program; and the arguments for your program. The usual
10887 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
10890 @var{comm} is either a device name (to use a serial line) or a TCP
10891 hostname and portnumber. For example, to debug Emacs with the argument
10892 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
10896 target> gdbserver /dev/com1 emacs foo.txt
10899 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
10902 To use a TCP connection instead of a serial line:
10905 target> gdbserver host:2345 emacs foo.txt
10908 The only difference from the previous example is the first argument,
10909 specifying that you are communicating with the host @value{GDBN} via
10910 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
10911 expect a TCP connection from machine @samp{host} to local TCP port 2345.
10912 (Currently, the @samp{host} part is ignored.) You can choose any number
10913 you want for the port number as long as it does not conflict with any
10914 TCP ports already in use on the target system (for example, @code{23} is
10915 reserved for @code{telnet}).@footnote{If you choose a port number that
10916 conflicts with another service, @code{gdbserver} prints an error message
10917 and exits.} You must use the same port number with the host @value{GDBN}
10918 @code{target remote} command.
10920 On some targets, @code{gdbserver} can also attach to running programs.
10921 This is accomplished via the @code{--attach} argument. The syntax is:
10924 target> gdbserver @var{comm} --attach @var{pid}
10927 @var{pid} is the process ID of a currently running process. It isn't necessary
10928 to point @code{gdbserver} at a binary for the running process.
10931 @cindex attach to a program by name
10932 You can debug processes by name instead of process ID if your target has the
10933 @code{pidof} utility:
10936 target> gdbserver @var{comm} --attach `pidof @var{PROGRAM}`
10939 In case more than one copy of @var{PROGRAM} is running, or @var{PROGRAM}
10940 has multiple threads, most versions of @code{pidof} support the
10941 @code{-s} option to only return the first process ID.
10943 @item On the host machine,
10944 connect to your target (@pxref{Connecting,,Connecting to a remote target}).
10945 For TCP connections, you must start up @code{gdbserver} prior to using
10946 the @code{target remote} command. Otherwise you may get an error whose
10947 text depends on the host system, but which usually looks something like
10948 @samp{Connection refused}. You don't need to use the @code{load}
10949 command in @value{GDBN} when using gdbserver, since the program is
10950 already on the target.
10955 @section Using the @code{gdbserve.nlm} program
10957 @kindex gdbserve.nlm
10958 @code{gdbserve.nlm} is a control program for NetWare systems, which
10959 allows you to connect your program with a remote @value{GDBN} via
10960 @code{target remote}.
10962 @value{GDBN} and @code{gdbserve.nlm} communicate via a serial line,
10963 using the standard @value{GDBN} remote serial protocol.
10966 @item On the target machine,
10967 you need to have a copy of the program you want to debug.
10968 @code{gdbserve.nlm} does not need your program's symbol table, so you
10969 can strip the program if necessary to save space. @value{GDBN} on the
10970 host system does all the symbol handling.
10972 To use the server, you must tell it how to communicate with
10973 @value{GDBN}; the name of your program; and the arguments for your
10974 program. The syntax is:
10977 load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ]
10978 [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ]
10981 @var{board} and @var{port} specify the serial line; @var{baud} specifies
10982 the baud rate used by the connection. @var{port} and @var{node} default
10983 to 0, @var{baud} defaults to 9600@dmn{bps}.
10985 For example, to debug Emacs with the argument @samp{foo.txt}and
10986 communicate with @value{GDBN} over serial port number 2 or board 1
10987 using a 19200@dmn{bps} connection:
10990 load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
10994 On the @value{GDBN} host machine, connect to your target (@pxref{Connecting,,
10995 Connecting to a remote target}).
10999 @node Remote configuration
11000 @section Remote configuration
11002 The following configuration options are available when debugging remote
11006 @kindex set remote hardware-watchpoint-limit
11007 @kindex set remote hardware-breakpoint-limit
11008 @anchor{set remote hardware-watchpoint-limit}
11009 @anchor{set remote hardware-breakpoint-limit}
11010 @item set remote hardware-watchpoint-limit @var{limit}
11011 @itemx set remote hardware-breakpoint-limit @var{limit}
11012 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
11013 watchpoints. A limit of -1, the default, is treated as unlimited.
11017 @section Implementing a remote stub
11019 @cindex debugging stub, example
11020 @cindex remote stub, example
11021 @cindex stub example, remote debugging
11022 The stub files provided with @value{GDBN} implement the target side of the
11023 communication protocol, and the @value{GDBN} side is implemented in the
11024 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
11025 these subroutines to communicate, and ignore the details. (If you're
11026 implementing your own stub file, you can still ignore the details: start
11027 with one of the existing stub files. @file{sparc-stub.c} is the best
11028 organized, and therefore the easiest to read.)
11030 @cindex remote serial debugging, overview
11031 To debug a program running on another machine (the debugging
11032 @dfn{target} machine), you must first arrange for all the usual
11033 prerequisites for the program to run by itself. For example, for a C
11038 A startup routine to set up the C runtime environment; these usually
11039 have a name like @file{crt0}. The startup routine may be supplied by
11040 your hardware supplier, or you may have to write your own.
11043 A C subroutine library to support your program's
11044 subroutine calls, notably managing input and output.
11047 A way of getting your program to the other machine---for example, a
11048 download program. These are often supplied by the hardware
11049 manufacturer, but you may have to write your own from hardware
11053 The next step is to arrange for your program to use a serial port to
11054 communicate with the machine where @value{GDBN} is running (the @dfn{host}
11055 machine). In general terms, the scheme looks like this:
11059 @value{GDBN} already understands how to use this protocol; when everything
11060 else is set up, you can simply use the @samp{target remote} command
11061 (@pxref{Targets,,Specifying a Debugging Target}).
11063 @item On the target,
11064 you must link with your program a few special-purpose subroutines that
11065 implement the @value{GDBN} remote serial protocol. The file containing these
11066 subroutines is called a @dfn{debugging stub}.
11068 On certain remote targets, you can use an auxiliary program
11069 @code{gdbserver} instead of linking a stub into your program.
11070 @xref{Server,,Using the @code{gdbserver} program}, for details.
11073 The debugging stub is specific to the architecture of the remote
11074 machine; for example, use @file{sparc-stub.c} to debug programs on
11077 @cindex remote serial stub list
11078 These working remote stubs are distributed with @value{GDBN}:
11083 @cindex @file{i386-stub.c}
11086 For Intel 386 and compatible architectures.
11089 @cindex @file{m68k-stub.c}
11090 @cindex Motorola 680x0
11092 For Motorola 680x0 architectures.
11095 @cindex @file{sh-stub.c}
11098 For Renesas SH architectures.
11101 @cindex @file{sparc-stub.c}
11103 For @sc{sparc} architectures.
11105 @item sparcl-stub.c
11106 @cindex @file{sparcl-stub.c}
11109 For Fujitsu @sc{sparclite} architectures.
11113 The @file{README} file in the @value{GDBN} distribution may list other
11114 recently added stubs.
11117 * Stub Contents:: What the stub can do for you
11118 * Bootstrapping:: What you must do for the stub
11119 * Debug Session:: Putting it all together
11122 @node Stub Contents
11123 @subsection What the stub can do for you
11125 @cindex remote serial stub
11126 The debugging stub for your architecture supplies these three
11130 @item set_debug_traps
11131 @kindex set_debug_traps
11132 @cindex remote serial stub, initialization
11133 This routine arranges for @code{handle_exception} to run when your
11134 program stops. You must call this subroutine explicitly near the
11135 beginning of your program.
11137 @item handle_exception
11138 @kindex handle_exception
11139 @cindex remote serial stub, main routine
11140 This is the central workhorse, but your program never calls it
11141 explicitly---the setup code arranges for @code{handle_exception} to
11142 run when a trap is triggered.
11144 @code{handle_exception} takes control when your program stops during
11145 execution (for example, on a breakpoint), and mediates communications
11146 with @value{GDBN} on the host machine. This is where the communications
11147 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
11148 representative on the target machine. It begins by sending summary
11149 information on the state of your program, then continues to execute,
11150 retrieving and transmitting any information @value{GDBN} needs, until you
11151 execute a @value{GDBN} command that makes your program resume; at that point,
11152 @code{handle_exception} returns control to your own code on the target
11156 @cindex @code{breakpoint} subroutine, remote
11157 Use this auxiliary subroutine to make your program contain a
11158 breakpoint. Depending on the particular situation, this may be the only
11159 way for @value{GDBN} to get control. For instance, if your target
11160 machine has some sort of interrupt button, you won't need to call this;
11161 pressing the interrupt button transfers control to
11162 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
11163 simply receiving characters on the serial port may also trigger a trap;
11164 again, in that situation, you don't need to call @code{breakpoint} from
11165 your own program---simply running @samp{target remote} from the host
11166 @value{GDBN} session gets control.
11168 Call @code{breakpoint} if none of these is true, or if you simply want
11169 to make certain your program stops at a predetermined point for the
11170 start of your debugging session.
11173 @node Bootstrapping
11174 @subsection What you must do for the stub
11176 @cindex remote stub, support routines
11177 The debugging stubs that come with @value{GDBN} are set up for a particular
11178 chip architecture, but they have no information about the rest of your
11179 debugging target machine.
11181 First of all you need to tell the stub how to communicate with the
11185 @item int getDebugChar()
11186 @kindex getDebugChar
11187 Write this subroutine to read a single character from the serial port.
11188 It may be identical to @code{getchar} for your target system; a
11189 different name is used to allow you to distinguish the two if you wish.
11191 @item void putDebugChar(int)
11192 @kindex putDebugChar
11193 Write this subroutine to write a single character to the serial port.
11194 It may be identical to @code{putchar} for your target system; a
11195 different name is used to allow you to distinguish the two if you wish.
11198 @cindex control C, and remote debugging
11199 @cindex interrupting remote targets
11200 If you want @value{GDBN} to be able to stop your program while it is
11201 running, you need to use an interrupt-driven serial driver, and arrange
11202 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
11203 character). That is the character which @value{GDBN} uses to tell the
11204 remote system to stop.
11206 Getting the debugging target to return the proper status to @value{GDBN}
11207 probably requires changes to the standard stub; one quick and dirty way
11208 is to just execute a breakpoint instruction (the ``dirty'' part is that
11209 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
11211 Other routines you need to supply are:
11214 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
11215 @kindex exceptionHandler
11216 Write this function to install @var{exception_address} in the exception
11217 handling tables. You need to do this because the stub does not have any
11218 way of knowing what the exception handling tables on your target system
11219 are like (for example, the processor's table might be in @sc{rom},
11220 containing entries which point to a table in @sc{ram}).
11221 @var{exception_number} is the exception number which should be changed;
11222 its meaning is architecture-dependent (for example, different numbers
11223 might represent divide by zero, misaligned access, etc). When this
11224 exception occurs, control should be transferred directly to
11225 @var{exception_address}, and the processor state (stack, registers,
11226 and so on) should be just as it is when a processor exception occurs. So if
11227 you want to use a jump instruction to reach @var{exception_address}, it
11228 should be a simple jump, not a jump to subroutine.
11230 For the 386, @var{exception_address} should be installed as an interrupt
11231 gate so that interrupts are masked while the handler runs. The gate
11232 should be at privilege level 0 (the most privileged level). The
11233 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
11234 help from @code{exceptionHandler}.
11236 @item void flush_i_cache()
11237 @kindex flush_i_cache
11238 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
11239 instruction cache, if any, on your target machine. If there is no
11240 instruction cache, this subroutine may be a no-op.
11242 On target machines that have instruction caches, @value{GDBN} requires this
11243 function to make certain that the state of your program is stable.
11247 You must also make sure this library routine is available:
11250 @item void *memset(void *, int, int)
11252 This is the standard library function @code{memset} that sets an area of
11253 memory to a known value. If you have one of the free versions of
11254 @code{libc.a}, @code{memset} can be found there; otherwise, you must
11255 either obtain it from your hardware manufacturer, or write your own.
11258 If you do not use the GNU C compiler, you may need other standard
11259 library subroutines as well; this varies from one stub to another,
11260 but in general the stubs are likely to use any of the common library
11261 subroutines which @code{@value{GCC}} generates as inline code.
11264 @node Debug Session
11265 @subsection Putting it all together
11267 @cindex remote serial debugging summary
11268 In summary, when your program is ready to debug, you must follow these
11273 Make sure you have defined the supporting low-level routines
11274 (@pxref{Bootstrapping,,What you must do for the stub}):
11276 @code{getDebugChar}, @code{putDebugChar},
11277 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
11281 Insert these lines near the top of your program:
11289 For the 680x0 stub only, you need to provide a variable called
11290 @code{exceptionHook}. Normally you just use:
11293 void (*exceptionHook)() = 0;
11297 but if before calling @code{set_debug_traps}, you set it to point to a
11298 function in your program, that function is called when
11299 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
11300 error). The function indicated by @code{exceptionHook} is called with
11301 one parameter: an @code{int} which is the exception number.
11304 Compile and link together: your program, the @value{GDBN} debugging stub for
11305 your target architecture, and the supporting subroutines.
11308 Make sure you have a serial connection between your target machine and
11309 the @value{GDBN} host, and identify the serial port on the host.
11312 @c The "remote" target now provides a `load' command, so we should
11313 @c document that. FIXME.
11314 Download your program to your target machine (or get it there by
11315 whatever means the manufacturer provides), and start it.
11318 Start @value{GDBN} on the host, and connect to the target
11319 (@pxref{Connecting,,Connecting to a remote target}).
11323 @node Configurations
11324 @chapter Configuration-Specific Information
11326 While nearly all @value{GDBN} commands are available for all native and
11327 cross versions of the debugger, there are some exceptions. This chapter
11328 describes things that are only available in certain configurations.
11330 There are three major categories of configurations: native
11331 configurations, where the host and target are the same, embedded
11332 operating system configurations, which are usually the same for several
11333 different processor architectures, and bare embedded processors, which
11334 are quite different from each other.
11339 * Embedded Processors::
11346 This section describes details specific to particular native
11351 * SVR4 Process Information:: SVR4 process information
11352 * DJGPP Native:: Features specific to the DJGPP port
11353 * Cygwin Native:: Features specific to the Cygwin port
11359 On HP-UX systems, if you refer to a function or variable name that
11360 begins with a dollar sign, @value{GDBN} searches for a user or system
11361 name first, before it searches for a convenience variable.
11363 @node SVR4 Process Information
11364 @subsection SVR4 process information
11367 @cindex process image
11369 Many versions of SVR4 provide a facility called @samp{/proc} that can be
11370 used to examine the image of a running process using file-system
11371 subroutines. If @value{GDBN} is configured for an operating system with
11372 this facility, the command @code{info proc} is available to report on
11373 several kinds of information about the process running your program.
11374 @code{info proc} works only on SVR4 systems that include the
11375 @code{procfs} code. This includes OSF/1 (Digital Unix), Solaris, Irix,
11376 and Unixware, but not HP-UX or @sc{gnu}/Linux, for example.
11381 Summarize available information about the process.
11383 @kindex info proc mappings
11384 @item info proc mappings
11385 Report on the address ranges accessible in the program, with information
11386 on whether your program may read, write, or execute each range.
11388 @comment These sub-options of 'info proc' were not included when
11389 @comment procfs.c was re-written. Keep their descriptions around
11390 @comment against the day when someone finds the time to put them back in.
11391 @kindex info proc times
11392 @item info proc times
11393 Starting time, user CPU time, and system CPU time for your program and
11396 @kindex info proc id
11398 Report on the process IDs related to your program: its own process ID,
11399 the ID of its parent, the process group ID, and the session ID.
11401 @kindex info proc status
11402 @item info proc status
11403 General information on the state of the process. If the process is
11404 stopped, this report includes the reason for stopping, and any signal
11407 @item info proc all
11408 Show all the above information about the process.
11413 @subsection Features for Debugging @sc{djgpp} Programs
11414 @cindex @sc{djgpp} debugging
11415 @cindex native @sc{djgpp} debugging
11416 @cindex MS-DOS-specific commands
11418 @sc{djgpp} is the port of @sc{gnu} development tools to MS-DOS and
11419 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
11420 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
11421 top of real-mode DOS systems and their emulations.
11423 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
11424 defines a few commands specific to the @sc{djgpp} port. This
11425 subsection describes those commands.
11430 This is a prefix of @sc{djgpp}-specific commands which print
11431 information about the target system and important OS structures.
11434 @cindex MS-DOS system info
11435 @cindex free memory information (MS-DOS)
11436 @item info dos sysinfo
11437 This command displays assorted information about the underlying
11438 platform: the CPU type and features, the OS version and flavor, the
11439 DPMI version, and the available conventional and DPMI memory.
11444 @cindex segment descriptor tables
11445 @cindex descriptor tables display
11447 @itemx info dos ldt
11448 @itemx info dos idt
11449 These 3 commands display entries from, respectively, Global, Local,
11450 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
11451 tables are data structures which store a descriptor for each segment
11452 that is currently in use. The segment's selector is an index into a
11453 descriptor table; the table entry for that index holds the
11454 descriptor's base address and limit, and its attributes and access
11457 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
11458 segment (used for both data and the stack), and a DOS segment (which
11459 allows access to DOS/BIOS data structures and absolute addresses in
11460 conventional memory). However, the DPMI host will usually define
11461 additional segments in order to support the DPMI environment.
11463 @cindex garbled pointers
11464 These commands allow to display entries from the descriptor tables.
11465 Without an argument, all entries from the specified table are
11466 displayed. An argument, which should be an integer expression, means
11467 display a single entry whose index is given by the argument. For
11468 example, here's a convenient way to display information about the
11469 debugged program's data segment:
11472 @exdent @code{(@value{GDBP}) info dos ldt $ds}
11473 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
11477 This comes in handy when you want to see whether a pointer is outside
11478 the data segment's limit (i.e.@: @dfn{garbled}).
11480 @cindex page tables display (MS-DOS)
11482 @itemx info dos pte
11483 These two commands display entries from, respectively, the Page
11484 Directory and the Page Tables. Page Directories and Page Tables are
11485 data structures which control how virtual memory addresses are mapped
11486 into physical addresses. A Page Table includes an entry for every
11487 page of memory that is mapped into the program's address space; there
11488 may be several Page Tables, each one holding up to 4096 entries. A
11489 Page Directory has up to 4096 entries, one each for every Page Table
11490 that is currently in use.
11492 Without an argument, @kbd{info dos pde} displays the entire Page
11493 Directory, and @kbd{info dos pte} displays all the entries in all of
11494 the Page Tables. An argument, an integer expression, given to the
11495 @kbd{info dos pde} command means display only that entry from the Page
11496 Directory table. An argument given to the @kbd{info dos pte} command
11497 means display entries from a single Page Table, the one pointed to by
11498 the specified entry in the Page Directory.
11500 @cindex direct memory access (DMA) on MS-DOS
11501 These commands are useful when your program uses @dfn{DMA} (Direct
11502 Memory Access), which needs physical addresses to program the DMA
11505 These commands are supported only with some DPMI servers.
11507 @cindex physical address from linear address
11508 @item info dos address-pte @var{addr}
11509 This command displays the Page Table entry for a specified linear
11510 address. The argument linear address @var{addr} should already have the
11511 appropriate segment's base address added to it, because this command
11512 accepts addresses which may belong to @emph{any} segment. For
11513 example, here's how to display the Page Table entry for the page where
11514 the variable @code{i} is stored:
11517 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
11518 @exdent @code{Page Table entry for address 0x11a00d30:}
11519 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
11523 This says that @code{i} is stored at offset @code{0xd30} from the page
11524 whose physical base address is @code{0x02698000}, and prints all the
11525 attributes of that page.
11527 Note that you must cast the addresses of variables to a @code{char *},
11528 since otherwise the value of @code{__djgpp_base_address}, the base
11529 address of all variables and functions in a @sc{djgpp} program, will
11530 be added using the rules of C pointer arithmetics: if @code{i} is
11531 declared an @code{int}, @value{GDBN} will add 4 times the value of
11532 @code{__djgpp_base_address} to the address of @code{i}.
11534 Here's another example, it displays the Page Table entry for the
11538 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
11539 @exdent @code{Page Table entry for address 0x29110:}
11540 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
11544 (The @code{+ 3} offset is because the transfer buffer's address is the
11545 3rd member of the @code{_go32_info_block} structure.) The output of
11546 this command clearly shows that addresses in conventional memory are
11547 mapped 1:1, i.e.@: the physical and linear addresses are identical.
11549 This command is supported only with some DPMI servers.
11552 @node Cygwin Native
11553 @subsection Features for Debugging MS Windows PE executables
11554 @cindex MS Windows debugging
11555 @cindex native Cygwin debugging
11556 @cindex Cygwin-specific commands
11558 @value{GDBN} supports native debugging of MS Windows programs, including
11559 DLLs with and without symbolic debugging information. There are various
11560 additional Cygwin-specific commands, described in this subsection. The
11561 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
11562 that have no debugging symbols.
11568 This is a prefix of MS Windows specific commands which print
11569 information about the target system and important OS structures.
11571 @item info w32 selector
11572 This command displays information returned by
11573 the Win32 API @code{GetThreadSelectorEntry} function.
11574 It takes an optional argument that is evaluated to
11575 a long value to give the information about this given selector.
11576 Without argument, this command displays information
11577 about the the six segment registers.
11581 This is a Cygwin specific alias of info shared.
11583 @kindex dll-symbols
11585 This command loads symbols from a dll similarly to
11586 add-sym command but without the need to specify a base address.
11588 @kindex set new-console
11589 @item set new-console @var{mode}
11590 If @var{mode} is @code{on} the debuggee will
11591 be started in a new console on next start.
11592 If @var{mode} is @code{off}i, the debuggee will
11593 be started in the same console as the debugger.
11595 @kindex show new-console
11596 @item show new-console
11597 Displays whether a new console is used
11598 when the debuggee is started.
11600 @kindex set new-group
11601 @item set new-group @var{mode}
11602 This boolean value controls whether the debuggee should
11603 start a new group or stay in the same group as the debugger.
11604 This affects the way the Windows OS handles
11607 @kindex show new-group
11608 @item show new-group
11609 Displays current value of new-group boolean.
11611 @kindex set debugevents
11612 @item set debugevents
11613 This boolean value adds debug output concerning events seen by the debugger.
11615 @kindex set debugexec
11616 @item set debugexec
11617 This boolean value adds debug output concerning execute events
11618 seen by the debugger.
11620 @kindex set debugexceptions
11621 @item set debugexceptions
11622 This boolean value adds debug ouptut concerning exception events
11623 seen by the debugger.
11625 @kindex set debugmemory
11626 @item set debugmemory
11627 This boolean value adds debug ouptut concerning memory events
11628 seen by the debugger.
11632 This boolean values specifies whether the debuggee is called
11633 via a shell or directly (default value is on).
11637 Displays if the debuggee will be started with a shell.
11642 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
11645 @node Non-debug DLL symbols
11646 @subsubsection Support for DLLs without debugging symbols
11647 @cindex DLLs with no debugging symbols
11648 @cindex Minimal symbols and DLLs
11650 Very often on windows, some of the DLLs that your program relies on do
11651 not include symbolic debugging information (for example,
11652 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
11653 symbols in a DLL, it relies on the minimal amount of symbolic
11654 information contained in the DLL's export table. This subsubsection
11655 describes working with such symbols, known internally to @value{GDBN} as
11656 ``minimal symbols''.
11658 Note that before the debugged program has started execution, no DLLs
11659 will have been loaded. The easiest way around this problem is simply to
11660 start the program --- either by setting a breakpoint or letting the
11661 program run once to completion. It is also possible to force
11662 @value{GDBN} to load a particular DLL before starting the executable ---
11663 see the shared library information in @pxref{Files} or the
11664 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
11665 explicitly loading symbols from a DLL with no debugging information will
11666 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
11667 which may adversely affect symbol lookup performance.
11669 @subsubsection DLL name prefixes
11671 In keeping with the naming conventions used by the Microsoft debugging
11672 tools, DLL export symbols are made available with a prefix based on the
11673 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
11674 also entered into the symbol table, so @code{CreateFileA} is often
11675 sufficient. In some cases there will be name clashes within a program
11676 (particularly if the executable itself includes full debugging symbols)
11677 necessitating the use of the fully qualified name when referring to the
11678 contents of the DLL. Use single-quotes around the name to avoid the
11679 exclamation mark (``!'') being interpreted as a language operator.
11681 Note that the internal name of the DLL may be all upper-case, even
11682 though the file name of the DLL is lower-case, or vice-versa. Since
11683 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
11684 some confusion. If in doubt, try the @code{info functions} and
11685 @code{info variables} commands or even @code{maint print msymbols} (see
11686 @pxref{Symbols}). Here's an example:
11689 (gdb) info function CreateFileA
11690 All functions matching regular expression "CreateFileA":
11692 Non-debugging symbols:
11693 0x77e885f4 CreateFileA
11694 0x77e885f4 KERNEL32!CreateFileA
11698 (gdb) info function !
11699 All functions matching regular expression "!":
11701 Non-debugging symbols:
11702 0x6100114c cygwin1!__assert
11703 0x61004034 cygwin1!_dll_crt0@@0
11704 0x61004240 cygwin1!dll_crt0(per_process *)
11708 @subsubsection Working with minimal symbols
11710 Symbols extracted from a DLL's export table do not contain very much
11711 type information. All that @value{GDBN} can do is guess whether a symbol
11712 refers to a function or variable depending on the linker section that
11713 contains the symbol. Also note that the actual contents of the memory
11714 contained in a DLL are not available unless the program is running. This
11715 means that you cannot examine the contents of a variable or disassemble
11716 a function within a DLL without a running program.
11718 Variables are generally treated as pointers and dereferenced
11719 automatically. For this reason, it is often necessary to prefix a
11720 variable name with the address-of operator (``&'') and provide explicit
11721 type information in the command. Here's an example of the type of
11725 (gdb) print 'cygwin1!__argv'
11730 (gdb) x 'cygwin1!__argv'
11731 0x10021610: "\230y\""
11734 And two possible solutions:
11737 (gdb) print ((char **)'cygwin1!__argv')[0]
11738 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
11742 (gdb) x/2x &'cygwin1!__argv'
11743 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
11744 (gdb) x/x 0x10021608
11745 0x10021608: 0x0022fd98
11746 (gdb) x/s 0x0022fd98
11747 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
11750 Setting a break point within a DLL is possible even before the program
11751 starts execution. However, under these circumstances, @value{GDBN} can't
11752 examine the initial instructions of the function in order to skip the
11753 function's frame set-up code. You can work around this by using ``*&''
11754 to set the breakpoint at a raw memory address:
11757 (gdb) break *&'python22!PyOS_Readline'
11758 Breakpoint 1 at 0x1e04eff0
11761 The author of these extensions is not entirely convinced that setting a
11762 break point within a shared DLL like @file{kernel32.dll} is completely
11766 @section Embedded Operating Systems
11768 This section describes configurations involving the debugging of
11769 embedded operating systems that are available for several different
11773 * VxWorks:: Using @value{GDBN} with VxWorks
11776 @value{GDBN} includes the ability to debug programs running on
11777 various real-time operating systems.
11780 @subsection Using @value{GDBN} with VxWorks
11786 @kindex target vxworks
11787 @item target vxworks @var{machinename}
11788 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
11789 is the target system's machine name or IP address.
11793 On VxWorks, @code{load} links @var{filename} dynamically on the
11794 current target system as well as adding its symbols in @value{GDBN}.
11796 @value{GDBN} enables developers to spawn and debug tasks running on networked
11797 VxWorks targets from a Unix host. Already-running tasks spawned from
11798 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
11799 both the Unix host and on the VxWorks target. The program
11800 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
11801 installed with the name @code{vxgdb}, to distinguish it from a
11802 @value{GDBN} for debugging programs on the host itself.)
11805 @item VxWorks-timeout @var{args}
11806 @kindex vxworks-timeout
11807 All VxWorks-based targets now support the option @code{vxworks-timeout}.
11808 This option is set by the user, and @var{args} represents the number of
11809 seconds @value{GDBN} waits for responses to rpc's. You might use this if
11810 your VxWorks target is a slow software simulator or is on the far side
11811 of a thin network line.
11814 The following information on connecting to VxWorks was current when
11815 this manual was produced; newer releases of VxWorks may use revised
11818 @kindex INCLUDE_RDB
11819 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
11820 to include the remote debugging interface routines in the VxWorks
11821 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
11822 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
11823 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
11824 source debugging task @code{tRdbTask} when VxWorks is booted. For more
11825 information on configuring and remaking VxWorks, see the manufacturer's
11827 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
11829 Once you have included @file{rdb.a} in your VxWorks system image and set
11830 your Unix execution search path to find @value{GDBN}, you are ready to
11831 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
11832 @code{vxgdb}, depending on your installation).
11834 @value{GDBN} comes up showing the prompt:
11841 * VxWorks Connection:: Connecting to VxWorks
11842 * VxWorks Download:: VxWorks download
11843 * VxWorks Attach:: Running tasks
11846 @node VxWorks Connection
11847 @subsubsection Connecting to VxWorks
11849 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
11850 network. To connect to a target whose host name is ``@code{tt}'', type:
11853 (vxgdb) target vxworks tt
11857 @value{GDBN} displays messages like these:
11860 Attaching remote machine across net...
11865 @value{GDBN} then attempts to read the symbol tables of any object modules
11866 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
11867 these files by searching the directories listed in the command search
11868 path (@pxref{Environment, ,Your program's environment}); if it fails
11869 to find an object file, it displays a message such as:
11872 prog.o: No such file or directory.
11875 When this happens, add the appropriate directory to the search path with
11876 the @value{GDBN} command @code{path}, and execute the @code{target}
11879 @node VxWorks Download
11880 @subsubsection VxWorks download
11882 @cindex download to VxWorks
11883 If you have connected to the VxWorks target and you want to debug an
11884 object that has not yet been loaded, you can use the @value{GDBN}
11885 @code{load} command to download a file from Unix to VxWorks
11886 incrementally. The object file given as an argument to the @code{load}
11887 command is actually opened twice: first by the VxWorks target in order
11888 to download the code, then by @value{GDBN} in order to read the symbol
11889 table. This can lead to problems if the current working directories on
11890 the two systems differ. If both systems have NFS mounted the same
11891 filesystems, you can avoid these problems by using absolute paths.
11892 Otherwise, it is simplest to set the working directory on both systems
11893 to the directory in which the object file resides, and then to reference
11894 the file by its name, without any path. For instance, a program
11895 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
11896 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
11897 program, type this on VxWorks:
11900 -> cd "@var{vxpath}/vw/demo/rdb"
11904 Then, in @value{GDBN}, type:
11907 (vxgdb) cd @var{hostpath}/vw/demo/rdb
11908 (vxgdb) load prog.o
11911 @value{GDBN} displays a response similar to this:
11914 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
11917 You can also use the @code{load} command to reload an object module
11918 after editing and recompiling the corresponding source file. Note that
11919 this makes @value{GDBN} delete all currently-defined breakpoints,
11920 auto-displays, and convenience variables, and to clear the value
11921 history. (This is necessary in order to preserve the integrity of
11922 debugger's data structures that reference the target system's symbol
11925 @node VxWorks Attach
11926 @subsubsection Running tasks
11928 @cindex running VxWorks tasks
11929 You can also attach to an existing task using the @code{attach} command as
11933 (vxgdb) attach @var{task}
11937 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
11938 or suspended when you attach to it. Running tasks are suspended at
11939 the time of attachment.
11941 @node Embedded Processors
11942 @section Embedded Processors
11944 This section goes into details specific to particular embedded
11950 * H8/300:: Renesas H8/300
11951 * H8/500:: Renesas H8/500
11952 * M32R/D:: Renesas M32R/D
11953 * M68K:: Motorola M68K
11954 * MIPS Embedded:: MIPS Embedded
11955 * OpenRISC 1000:: OpenRisc 1000
11956 * PA:: HP PA Embedded
11959 * Sparclet:: Tsqware Sparclet
11960 * Sparclite:: Fujitsu Sparclite
11961 * ST2000:: Tandem ST2000
11962 * Z8000:: Zilog Z8000
11971 @item target rdi @var{dev}
11972 ARM Angel monitor, via RDI library interface to ADP protocol. You may
11973 use this target to communicate with both boards running the Angel
11974 monitor, or with the EmbeddedICE JTAG debug device.
11977 @item target rdp @var{dev}
11983 @subsection Renesas H8/300
11987 @kindex target hms@r{, with H8/300}
11988 @item target hms @var{dev}
11989 A Renesas SH, H8/300, or H8/500 board, attached via serial line to your host.
11990 Use special commands @code{device} and @code{speed} to control the serial
11991 line and the communications speed used.
11993 @kindex target e7000@r{, with H8/300}
11994 @item target e7000 @var{dev}
11995 E7000 emulator for Renesas H8 and SH.
11997 @kindex target sh3@r{, with H8/300}
11998 @kindex target sh3e@r{, with H8/300}
11999 @item target sh3 @var{dev}
12000 @itemx target sh3e @var{dev}
12001 Renesas SH-3 and SH-3E target systems.
12005 @cindex download to H8/300 or H8/500
12006 @cindex H8/300 or H8/500 download
12007 @cindex download to Renesas SH
12008 @cindex Renesas SH download
12009 When you select remote debugging to a Renesas SH, H8/300, or H8/500
12010 board, the @code{load} command downloads your program to the Renesas
12011 board and also opens it as the current executable target for
12012 @value{GDBN} on your host (like the @code{file} command).
12014 @value{GDBN} needs to know these things to talk to your
12015 Renesas SH, H8/300, or H8/500:
12019 that you want to use @samp{target hms}, the remote debugging interface
12020 for Renesas microprocessors, or @samp{target e7000}, the in-circuit
12021 emulator for the Renesas SH and the Renesas 300H. (@samp{target hms} is
12022 the default when @value{GDBN} is configured specifically for the Renesas SH,
12023 H8/300, or H8/500.)
12026 what serial device connects your host to your Renesas board (the first
12027 serial device available on your host is the default).
12030 what speed to use over the serial device.
12034 * Renesas Boards:: Connecting to Renesas boards.
12035 * Renesas ICE:: Using the E7000 In-Circuit Emulator.
12036 * Renesas Special:: Special @value{GDBN} commands for Renesas micros.
12039 @node Renesas Boards
12040 @subsubsection Connecting to Renesas boards
12042 @c only for Unix hosts
12044 @cindex serial device, Renesas micros
12045 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
12046 need to explicitly set the serial device. The default @var{port} is the
12047 first available port on your host. This is only necessary on Unix
12048 hosts, where it is typically something like @file{/dev/ttya}.
12051 @cindex serial line speed, Renesas micros
12052 @code{@value{GDBN}} has another special command to set the communications
12053 speed: @samp{speed @var{bps}}. This command also is only used from Unix
12054 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
12055 the DOS @code{mode} command (for instance,
12056 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
12058 The @samp{device} and @samp{speed} commands are available only when you
12059 use a Unix host to debug your Renesas microprocessor programs. If you
12061 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
12062 called @code{asynctsr} to communicate with the development board
12063 through a PC serial port. You must also use the DOS @code{mode} command
12064 to set up the serial port on the DOS side.
12066 The following sample session illustrates the steps needed to start a
12067 program under @value{GDBN} control on an H8/300. The example uses a
12068 sample H8/300 program called @file{t.x}. The procedure is the same for
12069 the Renesas SH and the H8/500.
12071 First hook up your development board. In this example, we use a
12072 board attached to serial port @code{COM2}; if you use a different serial
12073 port, substitute its name in the argument of the @code{mode} command.
12074 When you call @code{asynctsr}, the auxiliary comms program used by the
12075 debugger, you give it just the numeric part of the serial port's name;
12076 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
12080 C:\H8300\TEST> asynctsr 2
12081 C:\H8300\TEST> mode com2:9600,n,8,1,p
12083 Resident portion of MODE loaded
12085 COM2: 9600, n, 8, 1, p
12090 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
12091 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
12092 disable it, or even boot without it, to use @code{asynctsr} to control
12093 your development board.
12096 @kindex target hms@r{, and serial protocol}
12097 Now that serial communications are set up, and the development board is
12098 connected, you can start up @value{GDBN}. Call @code{@value{GDBP}} with
12099 the name of your program as the argument. @code{@value{GDBN}} prompts
12100 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
12101 commands to begin your debugging session: @samp{target hms} to specify
12102 cross-debugging to the Renesas board, and the @code{load} command to
12103 download your program to the board. @code{load} displays the names of
12104 the program's sections, and a @samp{*} for each 2K of data downloaded.
12105 (If you want to refresh @value{GDBN} data on symbols or on the
12106 executable file without downloading, use the @value{GDBN} commands
12107 @code{file} or @code{symbol-file}. These commands, and @code{load}
12108 itself, are described in @ref{Files,,Commands to specify files}.)
12111 (eg-C:\H8300\TEST) @value{GDBP} t.x
12112 @value{GDBN} is free software and you are welcome to distribute copies
12113 of it under certain conditions; type "show copying" to see
12115 There is absolutely no warranty for @value{GDBN}; type "show warranty"
12117 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
12118 (@value{GDBP}) target hms
12119 Connected to remote H8/300 HMS system.
12120 (@value{GDBP}) load t.x
12121 .text : 0x8000 .. 0xabde ***********
12122 .data : 0xabde .. 0xad30 *
12123 .stack : 0xf000 .. 0xf014 *
12126 At this point, you're ready to run or debug your program. From here on,
12127 you can use all the usual @value{GDBN} commands. The @code{break} command
12128 sets breakpoints; the @code{run} command starts your program;
12129 @code{print} or @code{x} display data; the @code{continue} command
12130 resumes execution after stopping at a breakpoint. You can use the
12131 @code{help} command at any time to find out more about @value{GDBN} commands.
12133 Remember, however, that @emph{operating system} facilities aren't
12134 available on your development board; for example, if your program hangs,
12135 you can't send an interrupt---but you can press the @sc{reset} switch!
12137 Use the @sc{reset} button on the development board
12140 to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
12141 no way to pass an interrupt signal to the development board); and
12144 to return to the @value{GDBN} command prompt after your program finishes
12145 normally. The communications protocol provides no other way for @value{GDBN}
12146 to detect program completion.
12149 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
12150 development board as a ``normal exit'' of your program.
12153 @subsubsection Using the E7000 in-circuit emulator
12155 @kindex target e7000@r{, with Renesas ICE}
12156 You can use the E7000 in-circuit emulator to develop code for either the
12157 Renesas SH or the H8/300H. Use one of these forms of the @samp{target
12158 e7000} command to connect @value{GDBN} to your E7000:
12161 @item target e7000 @var{port} @var{speed}
12162 Use this form if your E7000 is connected to a serial port. The
12163 @var{port} argument identifies what serial port to use (for example,
12164 @samp{com2}). The third argument is the line speed in bits per second
12165 (for example, @samp{9600}).
12167 @item target e7000 @var{hostname}
12168 If your E7000 is installed as a host on a TCP/IP network, you can just
12169 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
12172 @node Renesas Special
12173 @subsubsection Special @value{GDBN} commands for Renesas micros
12175 Some @value{GDBN} commands are available only for the H8/300:
12179 @kindex set machine
12180 @kindex show machine
12181 @item set machine h8300
12182 @itemx set machine h8300h
12183 Condition @value{GDBN} for one of the two variants of the H8/300
12184 architecture with @samp{set machine}. You can use @samp{show machine}
12185 to check which variant is currently in effect.
12194 @kindex set memory @var{mod}
12195 @cindex memory models, H8/500
12196 @item set memory @var{mod}
12198 Specify which H8/500 memory model (@var{mod}) you are using with
12199 @samp{set memory}; check which memory model is in effect with @samp{show
12200 memory}. The accepted values for @var{mod} are @code{small},
12201 @code{big}, @code{medium}, and @code{compact}.
12206 @subsection Renesas M32R/D
12210 @kindex target m32r
12211 @item target m32r @var{dev}
12212 Renesas M32R/D ROM monitor.
12214 @kindex target m32rsdi
12215 @item target m32rsdi @var{dev}
12216 Renesas M32R SDI server, connected via parallel port to the board.
12223 The Motorola m68k configuration includes ColdFire support, and
12224 target command for the following ROM monitors.
12228 @kindex target abug
12229 @item target abug @var{dev}
12230 ABug ROM monitor for M68K.
12232 @kindex target cpu32bug
12233 @item target cpu32bug @var{dev}
12234 CPU32BUG monitor, running on a CPU32 (M68K) board.
12236 @kindex target dbug
12237 @item target dbug @var{dev}
12238 dBUG ROM monitor for Motorola ColdFire.
12241 @item target est @var{dev}
12242 EST-300 ICE monitor, running on a CPU32 (M68K) board.
12244 @kindex target rom68k
12245 @item target rom68k @var{dev}
12246 ROM 68K monitor, running on an M68K IDP board.
12252 @kindex target rombug
12253 @item target rombug @var{dev}
12254 ROMBUG ROM monitor for OS/9000.
12258 @node MIPS Embedded
12259 @subsection MIPS Embedded
12261 @cindex MIPS boards
12262 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
12263 MIPS board attached to a serial line. This is available when
12264 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
12267 Use these @value{GDBN} commands to specify the connection to your target board:
12270 @item target mips @var{port}
12271 @kindex target mips @var{port}
12272 To run a program on the board, start up @code{@value{GDBP}} with the
12273 name of your program as the argument. To connect to the board, use the
12274 command @samp{target mips @var{port}}, where @var{port} is the name of
12275 the serial port connected to the board. If the program has not already
12276 been downloaded to the board, you may use the @code{load} command to
12277 download it. You can then use all the usual @value{GDBN} commands.
12279 For example, this sequence connects to the target board through a serial
12280 port, and loads and runs a program called @var{prog} through the
12284 host$ @value{GDBP} @var{prog}
12285 @value{GDBN} is free software and @dots{}
12286 (@value{GDBP}) target mips /dev/ttyb
12287 (@value{GDBP}) load @var{prog}
12291 @item target mips @var{hostname}:@var{portnumber}
12292 On some @value{GDBN} host configurations, you can specify a TCP
12293 connection (for instance, to a serial line managed by a terminal
12294 concentrator) instead of a serial port, using the syntax
12295 @samp{@var{hostname}:@var{portnumber}}.
12297 @item target pmon @var{port}
12298 @kindex target pmon @var{port}
12301 @item target ddb @var{port}
12302 @kindex target ddb @var{port}
12303 NEC's DDB variant of PMON for Vr4300.
12305 @item target lsi @var{port}
12306 @kindex target lsi @var{port}
12307 LSI variant of PMON.
12309 @kindex target r3900
12310 @item target r3900 @var{dev}
12311 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
12313 @kindex target array
12314 @item target array @var{dev}
12315 Array Tech LSI33K RAID controller board.
12321 @value{GDBN} also supports these special commands for MIPS targets:
12324 @item set processor @var{args}
12325 @itemx show processor
12326 @kindex set processor @var{args}
12327 @kindex show processor
12328 Use the @code{set processor} command to set the type of MIPS
12329 processor when you want to access processor-type-specific registers.
12330 For example, @code{set processor @var{r3041}} tells @value{GDBN}
12331 to use the CPU registers appropriate for the 3041 chip.
12332 Use the @code{show processor} command to see what MIPS processor @value{GDBN}
12333 is using. Use the @code{info reg} command to see what registers
12334 @value{GDBN} is using.
12336 @item set mipsfpu double
12337 @itemx set mipsfpu single
12338 @itemx set mipsfpu none
12339 @itemx show mipsfpu
12340 @kindex set mipsfpu
12341 @kindex show mipsfpu
12342 @cindex MIPS remote floating point
12343 @cindex floating point, MIPS remote
12344 If your target board does not support the MIPS floating point
12345 coprocessor, you should use the command @samp{set mipsfpu none} (if you
12346 need this, you may wish to put the command in your @value{GDBN} init
12347 file). This tells @value{GDBN} how to find the return value of
12348 functions which return floating point values. It also allows
12349 @value{GDBN} to avoid saving the floating point registers when calling
12350 functions on the board. If you are using a floating point coprocessor
12351 with only single precision floating point support, as on the @sc{r4650}
12352 processor, use the command @samp{set mipsfpu single}. The default
12353 double precision floating point coprocessor may be selected using
12354 @samp{set mipsfpu double}.
12356 In previous versions the only choices were double precision or no
12357 floating point, so @samp{set mipsfpu on} will select double precision
12358 and @samp{set mipsfpu off} will select no floating point.
12360 As usual, you can inquire about the @code{mipsfpu} variable with
12361 @samp{show mipsfpu}.
12363 @item set remotedebug @var{n}
12364 @itemx show remotedebug
12365 @kindex set remotedebug@r{, MIPS protocol}
12366 @kindex show remotedebug@r{, MIPS protocol}
12367 @cindex @code{remotedebug}, MIPS protocol
12368 @cindex MIPS @code{remotedebug} protocol
12369 @c FIXME! For this to be useful, you must know something about the MIPS
12370 @c FIXME...protocol. Where is it described?
12371 You can see some debugging information about communications with the board
12372 by setting the @code{remotedebug} variable. If you set it to @code{1} using
12373 @samp{set remotedebug 1}, every packet is displayed. If you set it
12374 to @code{2}, every character is displayed. You can check the current value
12375 at any time with the command @samp{show remotedebug}.
12377 @item set timeout @var{seconds}
12378 @itemx set retransmit-timeout @var{seconds}
12379 @itemx show timeout
12380 @itemx show retransmit-timeout
12381 @cindex @code{timeout}, MIPS protocol
12382 @cindex @code{retransmit-timeout}, MIPS protocol
12383 @kindex set timeout
12384 @kindex show timeout
12385 @kindex set retransmit-timeout
12386 @kindex show retransmit-timeout
12387 You can control the timeout used while waiting for a packet, in the MIPS
12388 remote protocol, with the @code{set timeout @var{seconds}} command. The
12389 default is 5 seconds. Similarly, you can control the timeout used while
12390 waiting for an acknowledgement of a packet with the @code{set
12391 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
12392 You can inspect both values with @code{show timeout} and @code{show
12393 retransmit-timeout}. (These commands are @emph{only} available when
12394 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
12396 The timeout set by @code{set timeout} does not apply when @value{GDBN}
12397 is waiting for your program to stop. In that case, @value{GDBN} waits
12398 forever because it has no way of knowing how long the program is going
12399 to run before stopping.
12402 @node OpenRISC 1000
12403 @subsection OpenRISC 1000
12404 @cindex OpenRISC 1000
12406 @cindex or1k boards
12407 See OR1k Architecture document (@uref{www.opencores.org}) for more information
12408 about platform and commands.
12412 @kindex target jtag
12413 @item target jtag jtag://@var{host}:@var{port}
12415 Connects to remote JTAG server.
12416 JTAG remote server can be either an or1ksim or JTAG server,
12417 connected via parallel port to the board.
12419 Example: @code{target jtag jtag://localhost:9999}
12422 @item or1ksim @var{command}
12423 If connected to @code{or1ksim} OpenRISC 1000 Architectural
12424 Simulator, proprietary commands can be executed.
12426 @kindex info or1k spr
12427 @item info or1k spr
12428 Displays spr groups.
12430 @item info or1k spr @var{group}
12431 @itemx info or1k spr @var{groupno}
12432 Displays register names in selected group.
12434 @item info or1k spr @var{group} @var{register}
12435 @itemx info or1k spr @var{register}
12436 @itemx info or1k spr @var{groupno} @var{registerno}
12437 @itemx info or1k spr @var{registerno}
12438 Shows information about specified spr register.
12441 @item spr @var{group} @var{register} @var{value}
12442 @itemx spr @var{register @var{value}}
12443 @itemx spr @var{groupno} @var{registerno @var{value}}
12444 @itemx spr @var{registerno @var{value}}
12445 Writes @var{value} to specified spr register.
12448 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
12449 It is very similar to @value{GDBN} trace, except it does not interfere with normal
12450 program execution and is thus much faster. Hardware breakpoints/watchpoint
12451 triggers can be set using:
12454 Load effective address/data
12456 Store effective address/data
12458 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
12463 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
12464 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
12466 @code{htrace} commands:
12467 @cindex OpenRISC 1000 htrace
12470 @item hwatch @var{conditional}
12471 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
12472 or Data. For example:
12474 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
12476 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
12478 @kindex htrace info
12480 Display information about current HW trace configuration.
12482 @kindex htrace trigger
12483 @item htrace trigger @var{conditional}
12484 Set starting criteria for HW trace.
12486 @kindex htrace qualifier
12487 @item htrace qualifier @var{conditional}
12488 Set acquisition qualifier for HW trace.
12490 @kindex htrace stop
12491 @item htrace stop @var{conditional}
12492 Set HW trace stopping criteria.
12494 @kindex htrace record
12495 @item htrace record [@var{data}]*
12496 Selects the data to be recorded, when qualifier is met and HW trace was
12499 @kindex htrace enable
12500 @item htrace enable
12501 @kindex htrace disable
12502 @itemx htrace disable
12503 Enables/disables the HW trace.
12505 @kindex htrace rewind
12506 @item htrace rewind [@var{filename}]
12507 Clears currently recorded trace data.
12509 If filename is specified, new trace file is made and any newly collected data
12510 will be written there.
12512 @kindex htrace print
12513 @item htrace print [@var{start} [@var{len}]]
12514 Prints trace buffer, using current record configuration.
12516 @kindex htrace mode continuous
12517 @item htrace mode continuous
12518 Set continuous trace mode.
12520 @kindex htrace mode suspend
12521 @item htrace mode suspend
12522 Set suspend trace mode.
12527 @subsection PowerPC
12531 @kindex target dink32
12532 @item target dink32 @var{dev}
12533 DINK32 ROM monitor.
12535 @kindex target ppcbug
12536 @item target ppcbug @var{dev}
12537 @kindex target ppcbug1
12538 @item target ppcbug1 @var{dev}
12539 PPCBUG ROM monitor for PowerPC.
12542 @item target sds @var{dev}
12543 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
12548 @subsection HP PA Embedded
12552 @kindex target op50n
12553 @item target op50n @var{dev}
12554 OP50N monitor, running on an OKI HPPA board.
12556 @kindex target w89k
12557 @item target w89k @var{dev}
12558 W89K monitor, running on a Winbond HPPA board.
12563 @subsection Renesas SH
12567 @kindex target hms@r{, with Renesas SH}
12568 @item target hms @var{dev}
12569 A Renesas SH board attached via serial line to your host. Use special
12570 commands @code{device} and @code{speed} to control the serial line and
12571 the communications speed used.
12573 @kindex target e7000@r{, with Renesas SH}
12574 @item target e7000 @var{dev}
12575 E7000 emulator for Renesas SH.
12577 @kindex target sh3@r{, with SH}
12578 @kindex target sh3e@r{, with SH}
12579 @item target sh3 @var{dev}
12580 @item target sh3e @var{dev}
12581 Renesas SH-3 and SH-3E target systems.
12586 @subsection Tsqware Sparclet
12590 @value{GDBN} enables developers to debug tasks running on
12591 Sparclet targets from a Unix host.
12592 @value{GDBN} uses code that runs on
12593 both the Unix host and on the Sparclet target. The program
12594 @code{@value{GDBP}} is installed and executed on the Unix host.
12597 @item remotetimeout @var{args}
12598 @kindex remotetimeout
12599 @value{GDBN} supports the option @code{remotetimeout}.
12600 This option is set by the user, and @var{args} represents the number of
12601 seconds @value{GDBN} waits for responses.
12604 @cindex compiling, on Sparclet
12605 When compiling for debugging, include the options @samp{-g} to get debug
12606 information and @samp{-Ttext} to relocate the program to where you wish to
12607 load it on the target. You may also want to add the options @samp{-n} or
12608 @samp{-N} in order to reduce the size of the sections. Example:
12611 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
12614 You can use @code{objdump} to verify that the addresses are what you intended:
12617 sparclet-aout-objdump --headers --syms prog
12620 @cindex running, on Sparclet
12622 your Unix execution search path to find @value{GDBN}, you are ready to
12623 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
12624 (or @code{sparclet-aout-gdb}, depending on your installation).
12626 @value{GDBN} comes up showing the prompt:
12633 * Sparclet File:: Setting the file to debug
12634 * Sparclet Connection:: Connecting to Sparclet
12635 * Sparclet Download:: Sparclet download
12636 * Sparclet Execution:: Running and debugging
12639 @node Sparclet File
12640 @subsubsection Setting file to debug
12642 The @value{GDBN} command @code{file} lets you choose with program to debug.
12645 (gdbslet) file prog
12649 @value{GDBN} then attempts to read the symbol table of @file{prog}.
12650 @value{GDBN} locates
12651 the file by searching the directories listed in the command search
12653 If the file was compiled with debug information (option "-g"), source
12654 files will be searched as well.
12655 @value{GDBN} locates
12656 the source files by searching the directories listed in the directory search
12657 path (@pxref{Environment, ,Your program's environment}).
12659 to find a file, it displays a message such as:
12662 prog: No such file or directory.
12665 When this happens, add the appropriate directories to the search paths with
12666 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
12667 @code{target} command again.
12669 @node Sparclet Connection
12670 @subsubsection Connecting to Sparclet
12672 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
12673 To connect to a target on serial port ``@code{ttya}'', type:
12676 (gdbslet) target sparclet /dev/ttya
12677 Remote target sparclet connected to /dev/ttya
12678 main () at ../prog.c:3
12682 @value{GDBN} displays messages like these:
12688 @node Sparclet Download
12689 @subsubsection Sparclet download
12691 @cindex download to Sparclet
12692 Once connected to the Sparclet target,
12693 you can use the @value{GDBN}
12694 @code{load} command to download the file from the host to the target.
12695 The file name and load offset should be given as arguments to the @code{load}
12697 Since the file format is aout, the program must be loaded to the starting
12698 address. You can use @code{objdump} to find out what this value is. The load
12699 offset is an offset which is added to the VMA (virtual memory address)
12700 of each of the file's sections.
12701 For instance, if the program
12702 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
12703 and bss at 0x12010170, in @value{GDBN}, type:
12706 (gdbslet) load prog 0x12010000
12707 Loading section .text, size 0xdb0 vma 0x12010000
12710 If the code is loaded at a different address then what the program was linked
12711 to, you may need to use the @code{section} and @code{add-symbol-file} commands
12712 to tell @value{GDBN} where to map the symbol table.
12714 @node Sparclet Execution
12715 @subsubsection Running and debugging
12717 @cindex running and debugging Sparclet programs
12718 You can now begin debugging the task using @value{GDBN}'s execution control
12719 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
12720 manual for the list of commands.
12724 Breakpoint 1 at 0x12010000: file prog.c, line 3.
12726 Starting program: prog
12727 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
12728 3 char *symarg = 0;
12730 4 char *execarg = "hello!";
12735 @subsection Fujitsu Sparclite
12739 @kindex target sparclite
12740 @item target sparclite @var{dev}
12741 Fujitsu sparclite boards, used only for the purpose of loading.
12742 You must use an additional command to debug the program.
12743 For example: target remote @var{dev} using @value{GDBN} standard
12749 @subsection Tandem ST2000
12751 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
12754 To connect your ST2000 to the host system, see the manufacturer's
12755 manual. Once the ST2000 is physically attached, you can run:
12758 target st2000 @var{dev} @var{speed}
12762 to establish it as your debugging environment. @var{dev} is normally
12763 the name of a serial device, such as @file{/dev/ttya}, connected to the
12764 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
12765 connection (for example, to a serial line attached via a terminal
12766 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
12768 The @code{load} and @code{attach} commands are @emph{not} defined for
12769 this target; you must load your program into the ST2000 as you normally
12770 would for standalone operation. @value{GDBN} reads debugging information
12771 (such as symbols) from a separate, debugging version of the program
12772 available on your host computer.
12773 @c FIXME!! This is terribly vague; what little content is here is
12774 @c basically hearsay.
12776 @cindex ST2000 auxiliary commands
12777 These auxiliary @value{GDBN} commands are available to help you with the ST2000
12781 @item st2000 @var{command}
12782 @kindex st2000 @var{cmd}
12783 @cindex STDBUG commands (ST2000)
12784 @cindex commands to STDBUG (ST2000)
12785 Send a @var{command} to the STDBUG monitor. See the manufacturer's
12786 manual for available commands.
12789 @cindex connect (to STDBUG)
12790 Connect the controlling terminal to the STDBUG command monitor. When
12791 you are done interacting with STDBUG, typing either of two character
12792 sequences gets you back to the @value{GDBN} command prompt:
12793 @kbd{@key{RET}~.} (Return, followed by tilde and period) or
12794 @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
12798 @subsection Zilog Z8000
12801 @cindex simulator, Z8000
12802 @cindex Zilog Z8000 simulator
12804 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
12807 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
12808 unsegmented variant of the Z8000 architecture) or the Z8001 (the
12809 segmented variant). The simulator recognizes which architecture is
12810 appropriate by inspecting the object code.
12813 @item target sim @var{args}
12815 @kindex target sim@r{, with Z8000}
12816 Debug programs on a simulated CPU. If the simulator supports setup
12817 options, specify them via @var{args}.
12821 After specifying this target, you can debug programs for the simulated
12822 CPU in the same style as programs for your host computer; use the
12823 @code{file} command to load a new program image, the @code{run} command
12824 to run your program, and so on.
12826 As well as making available all the usual machine registers
12827 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
12828 additional items of information as specially named registers:
12833 Counts clock-ticks in the simulator.
12836 Counts instructions run in the simulator.
12839 Execution time in 60ths of a second.
12843 You can refer to these values in @value{GDBN} expressions with the usual
12844 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
12845 conditional breakpoint that suspends only after at least 5000
12846 simulated clock ticks.
12848 @node Architectures
12849 @section Architectures
12851 This section describes characteristics of architectures that affect
12852 all uses of @value{GDBN} with the architecture, both native and cross.
12865 @kindex set rstack_high_address
12866 @cindex AMD 29K register stack
12867 @cindex register stack, AMD29K
12868 @item set rstack_high_address @var{address}
12869 On AMD 29000 family processors, registers are saved in a separate
12870 @dfn{register stack}. There is no way for @value{GDBN} to determine the
12871 extent of this stack. Normally, @value{GDBN} just assumes that the
12872 stack is ``large enough''. This may result in @value{GDBN} referencing
12873 memory locations that do not exist. If necessary, you can get around
12874 this problem by specifying the ending address of the register stack with
12875 the @code{set rstack_high_address} command. The argument should be an
12876 address, which you probably want to precede with @samp{0x} to specify in
12879 @kindex show rstack_high_address
12880 @item show rstack_high_address
12881 Display the current limit of the register stack, on AMD 29000 family
12889 See the following section.
12894 @cindex stack on Alpha
12895 @cindex stack on MIPS
12896 @cindex Alpha stack
12898 Alpha- and MIPS-based computers use an unusual stack frame, which
12899 sometimes requires @value{GDBN} to search backward in the object code to
12900 find the beginning of a function.
12902 @cindex response time, MIPS debugging
12903 To improve response time (especially for embedded applications, where
12904 @value{GDBN} may be restricted to a slow serial line for this search)
12905 you may want to limit the size of this search, using one of these
12909 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
12910 @item set heuristic-fence-post @var{limit}
12911 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
12912 search for the beginning of a function. A value of @var{0} (the
12913 default) means there is no limit. However, except for @var{0}, the
12914 larger the limit the more bytes @code{heuristic-fence-post} must search
12915 and therefore the longer it takes to run.
12917 @item show heuristic-fence-post
12918 Display the current limit.
12922 These commands are available @emph{only} when @value{GDBN} is configured
12923 for debugging programs on Alpha or MIPS processors.
12926 @node Controlling GDB
12927 @chapter Controlling @value{GDBN}
12929 You can alter the way @value{GDBN} interacts with you by using the
12930 @code{set} command. For commands controlling how @value{GDBN} displays
12931 data, see @ref{Print Settings, ,Print settings}. Other settings are
12936 * Editing:: Command editing
12937 * History:: Command history
12938 * Screen Size:: Screen size
12939 * Numbers:: Numbers
12940 * ABI:: Configuring the current ABI
12941 * Messages/Warnings:: Optional warnings and messages
12942 * Debugging Output:: Optional messages about internal happenings
12950 @value{GDBN} indicates its readiness to read a command by printing a string
12951 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
12952 can change the prompt string with the @code{set prompt} command. For
12953 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
12954 the prompt in one of the @value{GDBN} sessions so that you can always tell
12955 which one you are talking to.
12957 @emph{Note:} @code{set prompt} does not add a space for you after the
12958 prompt you set. This allows you to set a prompt which ends in a space
12959 or a prompt that does not.
12963 @item set prompt @var{newprompt}
12964 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
12966 @kindex show prompt
12968 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
12972 @section Command editing
12974 @cindex command line editing
12976 @value{GDBN} reads its input commands via the @dfn{readline} interface. This
12977 @sc{gnu} library provides consistent behavior for programs which provide a
12978 command line interface to the user. Advantages are @sc{gnu} Emacs-style
12979 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
12980 substitution, and a storage and recall of command history across
12981 debugging sessions.
12983 You may control the behavior of command line editing in @value{GDBN} with the
12984 command @code{set}.
12987 @kindex set editing
12990 @itemx set editing on
12991 Enable command line editing (enabled by default).
12993 @item set editing off
12994 Disable command line editing.
12996 @kindex show editing
12998 Show whether command line editing is enabled.
13002 @section Command history
13004 @value{GDBN} can keep track of the commands you type during your
13005 debugging sessions, so that you can be certain of precisely what
13006 happened. Use these commands to manage the @value{GDBN} command
13010 @cindex history substitution
13011 @cindex history file
13012 @kindex set history filename
13013 @kindex GDBHISTFILE
13014 @item set history filename @var{fname}
13015 Set the name of the @value{GDBN} command history file to @var{fname}.
13016 This is the file where @value{GDBN} reads an initial command history
13017 list, and where it writes the command history from this session when it
13018 exits. You can access this list through history expansion or through
13019 the history command editing characters listed below. This file defaults
13020 to the value of the environment variable @code{GDBHISTFILE}, or to
13021 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
13024 @cindex history save
13025 @kindex set history save
13026 @item set history save
13027 @itemx set history save on
13028 Record command history in a file, whose name may be specified with the
13029 @code{set history filename} command. By default, this option is disabled.
13031 @item set history save off
13032 Stop recording command history in a file.
13034 @cindex history size
13035 @kindex set history size
13036 @item set history size @var{size}
13037 Set the number of commands which @value{GDBN} keeps in its history list.
13038 This defaults to the value of the environment variable
13039 @code{HISTSIZE}, or to 256 if this variable is not set.
13042 @cindex history expansion
13043 History expansion assigns special meaning to the character @kbd{!}.
13044 @ifset have-readline-appendices
13045 @xref{Event Designators}.
13048 Since @kbd{!} is also the logical not operator in C, history expansion
13049 is off by default. If you decide to enable history expansion with the
13050 @code{set history expansion on} command, you may sometimes need to
13051 follow @kbd{!} (when it is used as logical not, in an expression) with
13052 a space or a tab to prevent it from being expanded. The readline
13053 history facilities do not attempt substitution on the strings
13054 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
13056 The commands to control history expansion are:
13059 @kindex set history expansion
13060 @item set history expansion on
13061 @itemx set history expansion
13062 Enable history expansion. History expansion is off by default.
13064 @item set history expansion off
13065 Disable history expansion.
13067 The readline code comes with more complete documentation of
13068 editing and history expansion features. Users unfamiliar with @sc{gnu} Emacs
13069 or @code{vi} may wish to read it.
13070 @ifset have-readline-appendices
13071 @xref{Command Line Editing}.
13075 @kindex show history
13077 @itemx show history filename
13078 @itemx show history save
13079 @itemx show history size
13080 @itemx show history expansion
13081 These commands display the state of the @value{GDBN} history parameters.
13082 @code{show history} by itself displays all four states.
13088 @item show commands
13089 Display the last ten commands in the command history.
13091 @item show commands @var{n}
13092 Print ten commands centered on command number @var{n}.
13094 @item show commands +
13095 Print ten commands just after the commands last printed.
13099 @section Screen size
13100 @cindex size of screen
13101 @cindex pauses in output
13103 Certain commands to @value{GDBN} may produce large amounts of
13104 information output to the screen. To help you read all of it,
13105 @value{GDBN} pauses and asks you for input at the end of each page of
13106 output. Type @key{RET} when you want to continue the output, or @kbd{q}
13107 to discard the remaining output. Also, the screen width setting
13108 determines when to wrap lines of output. Depending on what is being
13109 printed, @value{GDBN} tries to break the line at a readable place,
13110 rather than simply letting it overflow onto the following line.
13112 Normally @value{GDBN} knows the size of the screen from the terminal
13113 driver software. For example, on Unix @value{GDBN} uses the termcap data base
13114 together with the value of the @code{TERM} environment variable and the
13115 @code{stty rows} and @code{stty cols} settings. If this is not correct,
13116 you can override it with the @code{set height} and @code{set
13123 @kindex show height
13124 @item set height @var{lpp}
13126 @itemx set width @var{cpl}
13128 These @code{set} commands specify a screen height of @var{lpp} lines and
13129 a screen width of @var{cpl} characters. The associated @code{show}
13130 commands display the current settings.
13132 If you specify a height of zero lines, @value{GDBN} does not pause during
13133 output no matter how long the output is. This is useful if output is to a
13134 file or to an editor buffer.
13136 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
13137 from wrapping its output.
13142 @cindex number representation
13143 @cindex entering numbers
13145 You can always enter numbers in octal, decimal, or hexadecimal in
13146 @value{GDBN} by the usual conventions: octal numbers begin with
13147 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
13148 begin with @samp{0x}. Numbers that begin with none of these are, by
13149 default, entered in base 10; likewise, the default display for
13150 numbers---when no particular format is specified---is base 10. You can
13151 change the default base for both input and output with the @code{set
13155 @kindex set input-radix
13156 @item set input-radix @var{base}
13157 Set the default base for numeric input. Supported choices
13158 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
13159 specified either unambiguously or using the current default radix; for
13169 sets the base to decimal. On the other hand, @samp{set radix 10}
13170 leaves the radix unchanged no matter what it was.
13172 @kindex set output-radix
13173 @item set output-radix @var{base}
13174 Set the default base for numeric display. Supported choices
13175 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
13176 specified either unambiguously or using the current default radix.
13178 @kindex show input-radix
13179 @item show input-radix
13180 Display the current default base for numeric input.
13182 @kindex show output-radix
13183 @item show output-radix
13184 Display the current default base for numeric display.
13188 @section Configuring the current ABI
13190 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
13191 application automatically. However, sometimes you need to override its
13192 conclusions. Use these commands to manage @value{GDBN}'s view of the
13199 One @value{GDBN} configuration can debug binaries for multiple operating
13200 system targets, either via remote debugging or native emulation.
13201 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
13202 but you can override its conclusion using the @code{set osabi} command.
13203 One example where this is useful is in debugging of binaries which use
13204 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
13205 not have the same identifying marks that the standard C library for your
13210 Show the OS ABI currently in use.
13213 With no argument, show the list of registered available OS ABI's.
13215 @item set osabi @var{abi}
13216 Set the current OS ABI to @var{abi}.
13219 @cindex float promotion
13220 @kindex set coerce-float-to-double
13222 Generally, the way that an argument of type @code{float} is passed to a
13223 function depends on whether the function is prototyped. For a prototyped
13224 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
13225 according to the architecture's convention for @code{float}. For unprototyped
13226 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
13227 @code{double} and then passed.
13229 Unfortunately, some forms of debug information do not reliably indicate whether
13230 a function is prototyped. If @value{GDBN} calls a function that is not marked
13231 as prototyped, it consults @kbd{set coerce-float-to-double}.
13234 @item set coerce-float-to-double
13235 @itemx set coerce-float-to-double on
13236 Arguments of type @code{float} will be promoted to @code{double} when passed
13237 to an unprototyped function. This is the default setting.
13239 @item set coerce-float-to-double off
13240 Arguments of type @code{float} will be passed directly to unprototyped
13245 @kindex show cp-abi
13246 @value{GDBN} needs to know the ABI used for your program's C@t{++}
13247 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
13248 used to build your application. @value{GDBN} only fully supports
13249 programs with a single C@t{++} ABI; if your program contains code using
13250 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
13251 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
13252 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
13253 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
13254 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
13255 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
13260 Show the C@t{++} ABI currently in use.
13263 With no argument, show the list of supported C@t{++} ABI's.
13265 @item set cp-abi @var{abi}
13266 @itemx set cp-abi auto
13267 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
13270 @node Messages/Warnings
13271 @section Optional warnings and messages
13273 By default, @value{GDBN} is silent about its inner workings. If you are
13274 running on a slow machine, you may want to use the @code{set verbose}
13275 command. This makes @value{GDBN} tell you when it does a lengthy
13276 internal operation, so you will not think it has crashed.
13278 Currently, the messages controlled by @code{set verbose} are those
13279 which announce that the symbol table for a source file is being read;
13280 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
13283 @kindex set verbose
13284 @item set verbose on
13285 Enables @value{GDBN} output of certain informational messages.
13287 @item set verbose off
13288 Disables @value{GDBN} output of certain informational messages.
13290 @kindex show verbose
13292 Displays whether @code{set verbose} is on or off.
13295 By default, if @value{GDBN} encounters bugs in the symbol table of an
13296 object file, it is silent; but if you are debugging a compiler, you may
13297 find this information useful (@pxref{Symbol Errors, ,Errors reading
13302 @kindex set complaints
13303 @item set complaints @var{limit}
13304 Permits @value{GDBN} to output @var{limit} complaints about each type of
13305 unusual symbols before becoming silent about the problem. Set
13306 @var{limit} to zero to suppress all complaints; set it to a large number
13307 to prevent complaints from being suppressed.
13309 @kindex show complaints
13310 @item show complaints
13311 Displays how many symbol complaints @value{GDBN} is permitted to produce.
13315 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
13316 lot of stupid questions to confirm certain commands. For example, if
13317 you try to run a program which is already running:
13321 The program being debugged has been started already.
13322 Start it from the beginning? (y or n)
13325 If you are willing to unflinchingly face the consequences of your own
13326 commands, you can disable this ``feature'':
13330 @kindex set confirm
13332 @cindex confirmation
13333 @cindex stupid questions
13334 @item set confirm off
13335 Disables confirmation requests.
13337 @item set confirm on
13338 Enables confirmation requests (the default).
13340 @kindex show confirm
13342 Displays state of confirmation requests.
13346 @node Debugging Output
13347 @section Optional messages about internal happenings
13349 @kindex set debug arch
13350 @item set debug arch
13351 Turns on or off display of gdbarch debugging info. The default is off
13352 @kindex show debug arch
13353 @item show debug arch
13354 Displays the current state of displaying gdbarch debugging info.
13355 @kindex set debug event
13356 @item set debug event
13357 Turns on or off display of @value{GDBN} event debugging info. The
13359 @kindex show debug event
13360 @item show debug event
13361 Displays the current state of displaying @value{GDBN} event debugging
13363 @kindex set debug expression
13364 @item set debug expression
13365 Turns on or off display of @value{GDBN} expression debugging info. The
13367 @kindex show debug expression
13368 @item show debug expression
13369 Displays the current state of displaying @value{GDBN} expression
13371 @kindex set debug frame
13372 @item set debug frame
13373 Turns on or off display of @value{GDBN} frame debugging info. The
13375 @kindex show debug frame
13376 @item show debug frame
13377 Displays the current state of displaying @value{GDBN} frame debugging
13379 @kindex set debug overload
13380 @item set debug overload
13381 Turns on or off display of @value{GDBN} C@t{++} overload debugging
13382 info. This includes info such as ranking of functions, etc. The default
13384 @kindex show debug overload
13385 @item show debug overload
13386 Displays the current state of displaying @value{GDBN} C@t{++} overload
13388 @kindex set debug remote
13389 @cindex packets, reporting on stdout
13390 @cindex serial connections, debugging
13391 @item set debug remote
13392 Turns on or off display of reports on all packets sent back and forth across
13393 the serial line to the remote machine. The info is printed on the
13394 @value{GDBN} standard output stream. The default is off.
13395 @kindex show debug remote
13396 @item show debug remote
13397 Displays the state of display of remote packets.
13398 @kindex set debug serial
13399 @item set debug serial
13400 Turns on or off display of @value{GDBN} serial debugging info. The
13402 @kindex show debug serial
13403 @item show debug serial
13404 Displays the current state of displaying @value{GDBN} serial debugging
13406 @kindex set debug target
13407 @item set debug target
13408 Turns on or off display of @value{GDBN} target debugging info. This info
13409 includes what is going on at the target level of GDB, as it happens. The
13411 @kindex show debug target
13412 @item show debug target
13413 Displays the current state of displaying @value{GDBN} target debugging
13415 @kindex set debug varobj
13416 @item set debug varobj
13417 Turns on or off display of @value{GDBN} variable object debugging
13418 info. The default is off.
13419 @kindex show debug varobj
13420 @item show debug varobj
13421 Displays the current state of displaying @value{GDBN} variable object
13426 @chapter Canned Sequences of Commands
13428 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
13429 command lists}), @value{GDBN} provides two ways to store sequences of
13430 commands for execution as a unit: user-defined commands and command
13434 * Define:: User-defined commands
13435 * Hooks:: User-defined command hooks
13436 * Command Files:: Command files
13437 * Output:: Commands for controlled output
13441 @section User-defined commands
13443 @cindex user-defined command
13444 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
13445 which you assign a new name as a command. This is done with the
13446 @code{define} command. User commands may accept up to 10 arguments
13447 separated by whitespace. Arguments are accessed within the user command
13448 via @var{$arg0@dots{}$arg9}. A trivial example:
13452 print $arg0 + $arg1 + $arg2
13456 To execute the command use:
13463 This defines the command @code{adder}, which prints the sum of
13464 its three arguments. Note the arguments are text substitutions, so they may
13465 reference variables, use complex expressions, or even perform inferior
13471 @item define @var{commandname}
13472 Define a command named @var{commandname}. If there is already a command
13473 by that name, you are asked to confirm that you want to redefine it.
13475 The definition of the command is made up of other @value{GDBN} command lines,
13476 which are given following the @code{define} command. The end of these
13477 commands is marked by a line containing @code{end}.
13482 Takes a single argument, which is an expression to evaluate.
13483 It is followed by a series of commands that are executed
13484 only if the expression is true (nonzero).
13485 There can then optionally be a line @code{else}, followed
13486 by a series of commands that are only executed if the expression
13487 was false. The end of the list is marked by a line containing @code{end}.
13491 The syntax is similar to @code{if}: the command takes a single argument,
13492 which is an expression to evaluate, and must be followed by the commands to
13493 execute, one per line, terminated by an @code{end}.
13494 The commands are executed repeatedly as long as the expression
13498 @item document @var{commandname}
13499 Document the user-defined command @var{commandname}, so that it can be
13500 accessed by @code{help}. The command @var{commandname} must already be
13501 defined. This command reads lines of documentation just as @code{define}
13502 reads the lines of the command definition, ending with @code{end}.
13503 After the @code{document} command is finished, @code{help} on command
13504 @var{commandname} displays the documentation you have written.
13506 You may use the @code{document} command again to change the
13507 documentation of a command. Redefining the command with @code{define}
13508 does not change the documentation.
13510 @kindex help user-defined
13511 @item help user-defined
13512 List all user-defined commands, with the first line of the documentation
13517 @itemx show user @var{commandname}
13518 Display the @value{GDBN} commands used to define @var{commandname} (but
13519 not its documentation). If no @var{commandname} is given, display the
13520 definitions for all user-defined commands.
13522 @kindex show max-user-call-depth
13523 @kindex set max-user-call-depth
13524 @item show max-user-call-depth
13525 @itemx set max-user-call-depth
13526 The value of @code{max-user-call-depth} controls how many recursion
13527 levels are allowed in user-defined commands before GDB suspects an
13528 infinite recursion and aborts the command.
13532 When user-defined commands are executed, the
13533 commands of the definition are not printed. An error in any command
13534 stops execution of the user-defined command.
13536 If used interactively, commands that would ask for confirmation proceed
13537 without asking when used inside a user-defined command. Many @value{GDBN}
13538 commands that normally print messages to say what they are doing omit the
13539 messages when used in a user-defined command.
13542 @section User-defined command hooks
13543 @cindex command hooks
13544 @cindex hooks, for commands
13545 @cindex hooks, pre-command
13549 You may define @dfn{hooks}, which are a special kind of user-defined
13550 command. Whenever you run the command @samp{foo}, if the user-defined
13551 command @samp{hook-foo} exists, it is executed (with no arguments)
13552 before that command.
13554 @cindex hooks, post-command
13557 A hook may also be defined which is run after the command you executed.
13558 Whenever you run the command @samp{foo}, if the user-defined command
13559 @samp{hookpost-foo} exists, it is executed (with no arguments) after
13560 that command. Post-execution hooks may exist simultaneously with
13561 pre-execution hooks, for the same command.
13563 It is valid for a hook to call the command which it hooks. If this
13564 occurs, the hook is not re-executed, thereby avoiding infinte recursion.
13566 @c It would be nice if hookpost could be passed a parameter indicating
13567 @c if the command it hooks executed properly or not. FIXME!
13569 @kindex stop@r{, a pseudo-command}
13570 In addition, a pseudo-command, @samp{stop} exists. Defining
13571 (@samp{hook-stop}) makes the associated commands execute every time
13572 execution stops in your program: before breakpoint commands are run,
13573 displays are printed, or the stack frame is printed.
13575 For example, to ignore @code{SIGALRM} signals while
13576 single-stepping, but treat them normally during normal execution,
13581 handle SIGALRM nopass
13585 handle SIGALRM pass
13588 define hook-continue
13589 handle SIGLARM pass
13593 As a further example, to hook at the begining and end of the @code{echo}
13594 command, and to add extra text to the beginning and end of the message,
13602 define hookpost-echo
13606 (@value{GDBP}) echo Hello World
13607 <<<---Hello World--->>>
13612 You can define a hook for any single-word command in @value{GDBN}, but
13613 not for command aliases; you should define a hook for the basic command
13614 name, e.g. @code{backtrace} rather than @code{bt}.
13615 @c FIXME! So how does Joe User discover whether a command is an alias
13617 If an error occurs during the execution of your hook, execution of
13618 @value{GDBN} commands stops and @value{GDBN} issues a prompt
13619 (before the command that you actually typed had a chance to run).
13621 If you try to define a hook which does not match any known command, you
13622 get a warning from the @code{define} command.
13624 @node Command Files
13625 @section Command files
13627 @cindex command files
13628 A command file for @value{GDBN} is a file of lines that are @value{GDBN}
13629 commands. Comments (lines starting with @kbd{#}) may also be included.
13630 An empty line in a command file does nothing; it does not mean to repeat
13631 the last command, as it would from the terminal.
13634 @cindex @file{.gdbinit}
13635 @cindex @file{gdb.ini}
13636 When you start @value{GDBN}, it automatically executes commands from its
13637 @dfn{init files}, normally called @file{.gdbinit}@footnote{The DJGPP
13638 port of @value{GDBN} uses the name @file{gdb.ini} instead, due to the
13639 limitations of file names imposed by DOS filesystems.}.
13640 During startup, @value{GDBN} does the following:
13644 Reads the init file (if any) in your home directory@footnote{On
13645 DOS/Windows systems, the home directory is the one pointed to by the
13646 @code{HOME} environment variable.}.
13649 Processes command line options and operands.
13652 Reads the init file (if any) in the current working directory.
13655 Reads command files specified by the @samp{-x} option.
13658 The init file in your home directory can set options (such as @samp{set
13659 complaints}) that affect subsequent processing of command line options
13660 and operands. Init files are not executed if you use the @samp{-nx}
13661 option (@pxref{Mode Options, ,Choosing modes}).
13663 @cindex init file name
13664 On some configurations of @value{GDBN}, the init file is known by a
13665 different name (these are typically environments where a specialized
13666 form of @value{GDBN} may need to coexist with other forms, hence a
13667 different name for the specialized version's init file). These are the
13668 environments with special init file names:
13670 @cindex @file{.vxgdbinit}
13673 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
13675 @cindex @file{.os68gdbinit}
13677 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
13679 @cindex @file{.esgdbinit}
13681 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
13684 You can also request the execution of a command file with the
13685 @code{source} command:
13689 @item source @var{filename}
13690 Execute the command file @var{filename}.
13693 The lines in a command file are executed sequentially. They are not
13694 printed as they are executed. An error in any command terminates
13695 execution of the command file and control is returned to the console.
13697 Commands that would ask for confirmation if used interactively proceed
13698 without asking when used in a command file. Many @value{GDBN} commands that
13699 normally print messages to say what they are doing omit the messages
13700 when called from command files.
13702 @value{GDBN} also accepts command input from standard input. In this
13703 mode, normal output goes to standard output and error output goes to
13704 standard error. Errors in a command file supplied on standard input do
13705 not terminate execution of the command file --- execution continues with
13709 gdb < cmds > log 2>&1
13712 (The syntax above will vary depending on the shell used.) This example
13713 will execute commands from the file @file{cmds}. All output and errors
13714 would be directed to @file{log}.
13717 @section Commands for controlled output
13719 During the execution of a command file or a user-defined command, normal
13720 @value{GDBN} output is suppressed; the only output that appears is what is
13721 explicitly printed by the commands in the definition. This section
13722 describes three commands useful for generating exactly the output you
13727 @item echo @var{text}
13728 @c I do not consider backslash-space a standard C escape sequence
13729 @c because it is not in ANSI.
13730 Print @var{text}. Nonprinting characters can be included in
13731 @var{text} using C escape sequences, such as @samp{\n} to print a
13732 newline. @strong{No newline is printed unless you specify one.}
13733 In addition to the standard C escape sequences, a backslash followed
13734 by a space stands for a space. This is useful for displaying a
13735 string with spaces at the beginning or the end, since leading and
13736 trailing spaces are otherwise trimmed from all arguments.
13737 To print @samp{@w{ }and foo =@w{ }}, use the command
13738 @samp{echo \@w{ }and foo = \@w{ }}.
13740 A backslash at the end of @var{text} can be used, as in C, to continue
13741 the command onto subsequent lines. For example,
13744 echo This is some text\n\
13745 which is continued\n\
13746 onto several lines.\n
13749 produces the same output as
13752 echo This is some text\n
13753 echo which is continued\n
13754 echo onto several lines.\n
13758 @item output @var{expression}
13759 Print the value of @var{expression} and nothing but that value: no
13760 newlines, no @samp{$@var{nn} = }. The value is not entered in the
13761 value history either. @xref{Expressions, ,Expressions}, for more information
13764 @item output/@var{fmt} @var{expression}
13765 Print the value of @var{expression} in format @var{fmt}. You can use
13766 the same formats as for @code{print}. @xref{Output Formats,,Output
13767 formats}, for more information.
13770 @item printf @var{string}, @var{expressions}@dots{}
13771 Print the values of the @var{expressions} under the control of
13772 @var{string}. The @var{expressions} are separated by commas and may be
13773 either numbers or pointers. Their values are printed as specified by
13774 @var{string}, exactly as if your program were to execute the C
13776 @c FIXME: the above implies that at least all ANSI C formats are
13777 @c supported, but it isn't true: %E and %G don't work (or so it seems).
13778 @c Either this is a bug, or the manual should document what formats are
13782 printf (@var{string}, @var{expressions}@dots{});
13785 For example, you can print two values in hex like this:
13788 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
13791 The only backslash-escape sequences that you can use in the format
13792 string are the simple ones that consist of backslash followed by a
13797 @chapter Command Interpreters
13798 @cindex command interpreters
13800 @value{GDBN} supports multiple command interpreters, and some command
13801 infrastructure to allow users or user interface writers to switch
13802 between interpreters or run commands in other interpreters.
13804 @value{GDBN} currently supports two command interpreters, the console
13805 interpreter (sometimes called the command-line interpreter or @sc{cli})
13806 and the machine interface interpreter (or @sc{gdb/mi}). This manual
13807 describes both of these interfaces in great detail.
13809 By default, @value{GDBN} will start with the console interpreter.
13810 However, the user may choose to start @value{GDBN} with another
13811 interpreter by specifying the @option{-i} or @option{--interpreter}
13812 startup options. Defined interpreters include:
13816 @cindex console interpreter
13817 The traditional console or command-line interpreter. This is the most often
13818 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
13819 @value{GDBN} will use this interpreter.
13822 @cindex mi interpreter
13823 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
13824 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
13825 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
13829 @cindex mi2 interpreter
13830 The current @sc{gdb/mi} interface.
13833 @cindex mi1 interpreter
13834 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
13838 @cindex invoke another interpreter
13839 The interpreter being used by @value{GDBN} may not be dynamically
13840 switched at runtime. Although possible, this could lead to a very
13841 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
13842 enters the command "interpreter-set console" in a console view,
13843 @value{GDBN} would switch to using the console interpreter, rendering
13844 the IDE inoperable!
13846 @kindex interpreter-exec
13847 Although you may only choose a single interpreter at startup, you may execute
13848 commands in any interpreter from the current interpreter using the appropriate
13849 command. If you are running the console interpreter, simply use the
13850 @code{interpreter-exec} command:
13853 interpreter-exec mi "-data-list-register-names"
13856 @sc{gdb/mi} has a similar command, although it is only available in versions of
13857 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
13860 @chapter @value{GDBN} Text User Interface
13864 * TUI Overview:: TUI overview
13865 * TUI Keys:: TUI key bindings
13866 * TUI Single Key Mode:: TUI single key mode
13867 * TUI Commands:: TUI specific commands
13868 * TUI Configuration:: TUI configuration variables
13871 The @value{GDBN} Text User Interface, TUI in short,
13872 is a terminal interface which uses the @code{curses} library
13873 to show the source file, the assembly output, the program registers
13874 and @value{GDBN} commands in separate text windows.
13875 The TUI is available only when @value{GDBN} is configured
13876 with the @code{--enable-tui} configure option (@pxref{Configure Options}).
13879 @section TUI overview
13881 The TUI has two display modes that can be switched while
13886 A curses (or TUI) mode in which it displays several text
13887 windows on the terminal.
13890 A standard mode which corresponds to the @value{GDBN} configured without
13894 In the TUI mode, @value{GDBN} can display several text window
13899 This window is the @value{GDBN} command window with the @value{GDBN}
13900 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
13901 managed using readline but through the TUI. The @emph{command}
13902 window is always visible.
13905 The source window shows the source file of the program. The current
13906 line as well as active breakpoints are displayed in this window.
13909 The assembly window shows the disassembly output of the program.
13912 This window shows the processor registers. It detects when
13913 a register is changed and when this is the case, registers that have
13914 changed are highlighted.
13918 The source and assembly windows show the current program position
13919 by highlighting the current line and marking them with the @samp{>} marker.
13920 Breakpoints are also indicated with two markers. A first one
13921 indicates the breakpoint type:
13925 Breakpoint which was hit at least once.
13928 Breakpoint which was never hit.
13931 Hardware breakpoint which was hit at least once.
13934 Hardware breakpoint which was never hit.
13938 The second marker indicates whether the breakpoint is enabled or not:
13942 Breakpoint is enabled.
13945 Breakpoint is disabled.
13949 The source, assembly and register windows are attached to the thread
13950 and the frame position. They are updated when the current thread
13951 changes, when the frame changes or when the program counter changes.
13952 These three windows are arranged by the TUI according to several
13953 layouts. The layout defines which of these three windows are visible.
13954 The following layouts are available:
13964 source and assembly
13967 source and registers
13970 assembly and registers
13974 On top of the command window a status line gives various information
13975 concerning the current process begin debugged. The status line is
13976 updated when the information it shows changes. The following fields
13981 Indicates the current gdb target
13982 (@pxref{Targets, ,Specifying a Debugging Target}).
13985 Gives information about the current process or thread number.
13986 When no process is being debugged, this field is set to @code{No process}.
13989 Gives the current function name for the selected frame.
13990 The name is demangled if demangling is turned on (@pxref{Print Settings}).
13991 When there is no symbol corresponding to the current program counter
13992 the string @code{??} is displayed.
13995 Indicates the current line number for the selected frame.
13996 When the current line number is not known the string @code{??} is displayed.
13999 Indicates the current program counter address.
14004 @section TUI Key Bindings
14005 @cindex TUI key bindings
14007 The TUI installs several key bindings in the readline keymaps
14008 (@pxref{Command Line Editing}).
14009 They allow to leave or enter in the TUI mode or they operate
14010 directly on the TUI layout and windows. The TUI also provides
14011 a @emph{SingleKey} keymap which binds several keys directly to
14012 @value{GDBN} commands. The following key bindings
14013 are installed for both TUI mode and the @value{GDBN} standard mode.
14022 Enter or leave the TUI mode. When the TUI mode is left,
14023 the curses window management is left and @value{GDBN} operates using
14024 its standard mode writing on the terminal directly. When the TUI
14025 mode is entered, the control is given back to the curses windows.
14026 The screen is then refreshed.
14030 Use a TUI layout with only one window. The layout will
14031 either be @samp{source} or @samp{assembly}. When the TUI mode
14032 is not active, it will switch to the TUI mode.
14034 Think of this key binding as the Emacs @kbd{C-x 1} binding.
14038 Use a TUI layout with at least two windows. When the current
14039 layout shows already two windows, a next layout with two windows is used.
14040 When a new layout is chosen, one window will always be common to the
14041 previous layout and the new one.
14043 Think of it as the Emacs @kbd{C-x 2} binding.
14047 Change the active window. The TUI associates several key bindings
14048 (like scrolling and arrow keys) to the active window. This command
14049 gives the focus to the next TUI window.
14051 Think of it as the Emacs @kbd{C-x o} binding.
14055 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
14056 (@pxref{TUI Single Key Mode}).
14060 The following key bindings are handled only by the TUI mode:
14065 Scroll the active window one page up.
14069 Scroll the active window one page down.
14073 Scroll the active window one line up.
14077 Scroll the active window one line down.
14081 Scroll the active window one column left.
14085 Scroll the active window one column right.
14089 Refresh the screen.
14093 In the TUI mode, the arrow keys are used by the active window
14094 for scrolling. This means they are available for readline when the
14095 active window is the command window. When the command window
14096 does not have the focus, it is necessary to use other readline
14097 key bindings such as @key{C-p}, @key{C-n}, @key{C-b} and @key{C-f}.
14099 @node TUI Single Key Mode
14100 @section TUI Single Key Mode
14101 @cindex TUI single key mode
14103 The TUI provides a @emph{SingleKey} mode in which it installs a particular
14104 key binding in the readline keymaps to connect single keys to
14108 @kindex c @r{(SingleKey TUI key)}
14112 @kindex d @r{(SingleKey TUI key)}
14116 @kindex f @r{(SingleKey TUI key)}
14120 @kindex n @r{(SingleKey TUI key)}
14124 @kindex q @r{(SingleKey TUI key)}
14126 exit the @emph{SingleKey} mode.
14128 @kindex r @r{(SingleKey TUI key)}
14132 @kindex s @r{(SingleKey TUI key)}
14136 @kindex u @r{(SingleKey TUI key)}
14140 @kindex v @r{(SingleKey TUI key)}
14144 @kindex w @r{(SingleKey TUI key)}
14150 Other keys temporarily switch to the @value{GDBN} command prompt.
14151 The key that was pressed is inserted in the editing buffer so that
14152 it is possible to type most @value{GDBN} commands without interaction
14153 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
14154 @emph{SingleKey} mode is restored. The only way to permanently leave
14155 this mode is by hitting @key{q} or @samp{@key{C-x} @key{s}}.
14159 @section TUI specific commands
14160 @cindex TUI commands
14162 The TUI has specific commands to control the text windows.
14163 These commands are always available, that is they do not depend on
14164 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
14165 is in the standard mode, using these commands will automatically switch
14171 List and give the size of all displayed windows.
14174 @kindex layout next
14175 Display the next layout.
14178 @kindex layout prev
14179 Display the previous layout.
14183 Display the source window only.
14187 Display the assembly window only.
14190 @kindex layout split
14191 Display the source and assembly window.
14194 @kindex layout regs
14195 Display the register window together with the source or assembly window.
14197 @item focus next | prev | src | asm | regs | split
14199 Set the focus to the named window.
14200 This command allows to change the active window so that scrolling keys
14201 can be affected to another window.
14205 Refresh the screen. This is similar to using @key{C-L} key.
14209 Update the source window and the current execution point.
14211 @item winheight @var{name} +@var{count}
14212 @itemx winheight @var{name} -@var{count}
14214 Change the height of the window @var{name} by @var{count}
14215 lines. Positive counts increase the height, while negative counts
14220 @node TUI Configuration
14221 @section TUI configuration variables
14222 @cindex TUI configuration variables
14224 The TUI has several configuration variables that control the
14225 appearance of windows on the terminal.
14228 @item set tui border-kind @var{kind}
14229 @kindex set tui border-kind
14230 Select the border appearance for the source, assembly and register windows.
14231 The possible values are the following:
14234 Use a space character to draw the border.
14237 Use ascii characters + - and | to draw the border.
14240 Use the Alternate Character Set to draw the border. The border is
14241 drawn using character line graphics if the terminal supports them.
14245 @item set tui active-border-mode @var{mode}
14246 @kindex set tui active-border-mode
14247 Select the attributes to display the border of the active window.
14248 The possible values are @code{normal}, @code{standout}, @code{reverse},
14249 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
14251 @item set tui border-mode @var{mode}
14252 @kindex set tui border-mode
14253 Select the attributes to display the border of other windows.
14254 The @var{mode} can be one of the following:
14257 Use normal attributes to display the border.
14263 Use reverse video mode.
14266 Use half bright mode.
14268 @item half-standout
14269 Use half bright and standout mode.
14272 Use extra bright or bold mode.
14274 @item bold-standout
14275 Use extra bright or bold and standout mode.
14282 @chapter Using @value{GDBN} under @sc{gnu} Emacs
14285 @cindex @sc{gnu} Emacs
14286 A special interface allows you to use @sc{gnu} Emacs to view (and
14287 edit) the source files for the program you are debugging with
14290 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
14291 executable file you want to debug as an argument. This command starts
14292 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
14293 created Emacs buffer.
14294 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
14296 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
14301 All ``terminal'' input and output goes through the Emacs buffer.
14304 This applies both to @value{GDBN} commands and their output, and to the input
14305 and output done by the program you are debugging.
14307 This is useful because it means that you can copy the text of previous
14308 commands and input them again; you can even use parts of the output
14311 All the facilities of Emacs' Shell mode are available for interacting
14312 with your program. In particular, you can send signals the usual
14313 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
14318 @value{GDBN} displays source code through Emacs.
14321 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
14322 source file for that frame and puts an arrow (@samp{=>}) at the
14323 left margin of the current line. Emacs uses a separate buffer for
14324 source display, and splits the screen to show both your @value{GDBN} session
14327 Explicit @value{GDBN} @code{list} or search commands still produce output as
14328 usual, but you probably have no reason to use them from Emacs.
14330 If you specify an absolute file name when prompted for the @kbd{M-x
14331 gdb} argument, then Emacs sets your current working directory to where
14332 your program resides. If you only specify the file name, then Emacs
14333 sets your current working directory to to the directory associated
14334 with the previous buffer. In this case, @value{GDBN} may find your
14335 program by searching your environment's @code{PATH} variable, but on
14336 some operating systems it might not find the source. So, although the
14337 @value{GDBN} input and output session proceeds normally, the auxiliary
14338 buffer does not display the current source and line of execution.
14340 The initial working directory of @value{GDBN} is printed on the top
14341 line of the @value{GDBN} I/O buffer and this serves as a default for
14342 the commands that specify files for @value{GDBN} to operate
14343 on. @xref{Files, ,Commands to specify files}.
14345 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
14346 need to call @value{GDBN} by a different name (for example, if you
14347 keep several configurations around, with different names) you can
14348 customize the Emacs variable @code{gud-gdb-command-name} to run the
14351 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
14352 addition to the standard Shell mode commands:
14356 Describe the features of Emacs' @value{GDBN} Mode.
14359 Execute to another source line, like the @value{GDBN} @code{step} command; also
14360 update the display window to show the current file and location.
14363 Execute to next source line in this function, skipping all function
14364 calls, like the @value{GDBN} @code{next} command. Then update the display window
14365 to show the current file and location.
14368 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
14369 display window accordingly.
14372 Execute until exit from the selected stack frame, like the @value{GDBN}
14373 @code{finish} command.
14376 Continue execution of your program, like the @value{GDBN} @code{continue}
14380 Go up the number of frames indicated by the numeric argument
14381 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
14382 like the @value{GDBN} @code{up} command.
14385 Go down the number of frames indicated by the numeric argument, like the
14386 @value{GDBN} @code{down} command.
14389 In any source file, the Emacs command @kbd{C-x SPC} (@code{gud-break})
14390 tells @value{GDBN} to set a breakpoint on the source line point is on.
14392 If you type @kbd{M-x speedbar}, then Emacs displays a separate frame which
14393 shows a backtrace when the @value{GDBN} I/O buffer is current. Move
14394 point to any frame in the stack and type @key{RET} to make it become the
14395 current frame and display the associated source in the source buffer.
14396 Alternatively, click @kbd{Mouse-2} to make the selected frame become the
14399 If you accidentally delete the source-display buffer, an easy way to get
14400 it back is to type the command @code{f} in the @value{GDBN} buffer, to
14401 request a frame display; when you run under Emacs, this recreates
14402 the source buffer if necessary to show you the context of the current
14405 The source files displayed in Emacs are in ordinary Emacs buffers
14406 which are visiting the source files in the usual way. You can edit
14407 the files with these buffers if you wish; but keep in mind that @value{GDBN}
14408 communicates with Emacs in terms of line numbers. If you add or
14409 delete lines from the text, the line numbers that @value{GDBN} knows cease
14410 to correspond properly with the code.
14412 The description given here is for GNU Emacs version 21.3 and a more
14413 detailed description of its interaction with @value{GDBN} is given in
14414 the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu} Emacs Manual}).
14416 @c The following dropped because Epoch is nonstandard. Reactivate
14417 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
14419 @kindex Emacs Epoch environment
14423 Version 18 of @sc{gnu} Emacs has a built-in window system
14424 called the @code{epoch}
14425 environment. Users of this environment can use a new command,
14426 @code{inspect} which performs identically to @code{print} except that
14427 each value is printed in its own window.
14432 @chapter The @sc{gdb/mi} Interface
14434 @unnumberedsec Function and Purpose
14436 @cindex @sc{gdb/mi}, its purpose
14437 @sc{gdb/mi} is a line based machine oriented text interface to @value{GDBN}. It is
14438 specifically intended to support the development of systems which use
14439 the debugger as just one small component of a larger system.
14441 This chapter is a specification of the @sc{gdb/mi} interface. It is written
14442 in the form of a reference manual.
14444 Note that @sc{gdb/mi} is still under construction, so some of the
14445 features described below are incomplete and subject to change.
14447 @unnumberedsec Notation and Terminology
14449 @cindex notational conventions, for @sc{gdb/mi}
14450 This chapter uses the following notation:
14454 @code{|} separates two alternatives.
14457 @code{[ @var{something} ]} indicates that @var{something} is optional:
14458 it may or may not be given.
14461 @code{( @var{group} )*} means that @var{group} inside the parentheses
14462 may repeat zero or more times.
14465 @code{( @var{group} )+} means that @var{group} inside the parentheses
14466 may repeat one or more times.
14469 @code{"@var{string}"} means a literal @var{string}.
14473 @heading Dependencies
14476 @heading Acknowledgments
14478 In alphabetic order: Andrew Cagney, Fernando Nasser, Stan Shebs and
14482 * GDB/MI Command Syntax::
14483 * GDB/MI Compatibility with CLI::
14484 * GDB/MI Output Records::
14485 * GDB/MI Command Description Format::
14486 * GDB/MI Breakpoint Table Commands::
14487 * GDB/MI Data Manipulation::
14488 * GDB/MI Program Control::
14489 * GDB/MI Miscellaneous Commands::
14491 * GDB/MI Kod Commands::
14492 * GDB/MI Memory Overlay Commands::
14493 * GDB/MI Signal Handling Commands::
14495 * GDB/MI Stack Manipulation::
14496 * GDB/MI Symbol Query::
14497 * GDB/MI Target Manipulation::
14498 * GDB/MI Thread Commands::
14499 * GDB/MI Tracepoint Commands::
14500 * GDB/MI Variable Objects::
14503 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14504 @node GDB/MI Command Syntax
14505 @section @sc{gdb/mi} Command Syntax
14508 * GDB/MI Input Syntax::
14509 * GDB/MI Output Syntax::
14510 * GDB/MI Simple Examples::
14513 @node GDB/MI Input Syntax
14514 @subsection @sc{gdb/mi} Input Syntax
14516 @cindex input syntax for @sc{gdb/mi}
14517 @cindex @sc{gdb/mi}, input syntax
14519 @item @var{command} @expansion{}
14520 @code{@var{cli-command} | @var{mi-command}}
14522 @item @var{cli-command} @expansion{}
14523 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
14524 @var{cli-command} is any existing @value{GDBN} CLI command.
14526 @item @var{mi-command} @expansion{}
14527 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
14528 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
14530 @item @var{token} @expansion{}
14531 "any sequence of digits"
14533 @item @var{option} @expansion{}
14534 @code{"-" @var{parameter} [ " " @var{parameter} ]}
14536 @item @var{parameter} @expansion{}
14537 @code{@var{non-blank-sequence} | @var{c-string}}
14539 @item @var{operation} @expansion{}
14540 @emph{any of the operations described in this chapter}
14542 @item @var{non-blank-sequence} @expansion{}
14543 @emph{anything, provided it doesn't contain special characters such as
14544 "-", @var{nl}, """ and of course " "}
14546 @item @var{c-string} @expansion{}
14547 @code{""" @var{seven-bit-iso-c-string-content} """}
14549 @item @var{nl} @expansion{}
14558 The CLI commands are still handled by the @sc{mi} interpreter; their
14559 output is described below.
14562 The @code{@var{token}}, when present, is passed back when the command
14566 Some @sc{mi} commands accept optional arguments as part of the parameter
14567 list. Each option is identified by a leading @samp{-} (dash) and may be
14568 followed by an optional argument parameter. Options occur first in the
14569 parameter list and can be delimited from normal parameters using
14570 @samp{--} (this is useful when some parameters begin with a dash).
14577 We want easy access to the existing CLI syntax (for debugging).
14580 We want it to be easy to spot a @sc{mi} operation.
14583 @node GDB/MI Output Syntax
14584 @subsection @sc{gdb/mi} Output Syntax
14586 @cindex output syntax of @sc{gdb/mi}
14587 @cindex @sc{gdb/mi}, output syntax
14588 The output from @sc{gdb/mi} consists of zero or more out-of-band records
14589 followed, optionally, by a single result record. This result record
14590 is for the most recent command. The sequence of output records is
14591 terminated by @samp{(@value{GDBP})}.
14593 If an input command was prefixed with a @code{@var{token}} then the
14594 corresponding output for that command will also be prefixed by that same
14598 @item @var{output} @expansion{}
14599 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
14601 @item @var{result-record} @expansion{}
14602 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
14604 @item @var{out-of-band-record} @expansion{}
14605 @code{@var{async-record} | @var{stream-record}}
14607 @item @var{async-record} @expansion{}
14608 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
14610 @item @var{exec-async-output} @expansion{}
14611 @code{[ @var{token} ] "*" @var{async-output}}
14613 @item @var{status-async-output} @expansion{}
14614 @code{[ @var{token} ] "+" @var{async-output}}
14616 @item @var{notify-async-output} @expansion{}
14617 @code{[ @var{token} ] "=" @var{async-output}}
14619 @item @var{async-output} @expansion{}
14620 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
14622 @item @var{result-class} @expansion{}
14623 @code{"done" | "running" | "connected" | "error" | "exit"}
14625 @item @var{async-class} @expansion{}
14626 @code{"stopped" | @var{others}} (where @var{others} will be added
14627 depending on the needs---this is still in development).
14629 @item @var{result} @expansion{}
14630 @code{ @var{variable} "=" @var{value}}
14632 @item @var{variable} @expansion{}
14633 @code{ @var{string} }
14635 @item @var{value} @expansion{}
14636 @code{ @var{const} | @var{tuple} | @var{list} }
14638 @item @var{const} @expansion{}
14639 @code{@var{c-string}}
14641 @item @var{tuple} @expansion{}
14642 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
14644 @item @var{list} @expansion{}
14645 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
14646 @var{result} ( "," @var{result} )* "]" }
14648 @item @var{stream-record} @expansion{}
14649 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
14651 @item @var{console-stream-output} @expansion{}
14652 @code{"~" @var{c-string}}
14654 @item @var{target-stream-output} @expansion{}
14655 @code{"@@" @var{c-string}}
14657 @item @var{log-stream-output} @expansion{}
14658 @code{"&" @var{c-string}}
14660 @item @var{nl} @expansion{}
14663 @item @var{token} @expansion{}
14664 @emph{any sequence of digits}.
14672 All output sequences end in a single line containing a period.
14675 The @code{@var{token}} is from the corresponding request. If an execution
14676 command is interrupted by the @samp{-exec-interrupt} command, the
14677 @var{token} associated with the @samp{*stopped} message is the one of the
14678 original execution command, not the one of the interrupt command.
14681 @cindex status output in @sc{gdb/mi}
14682 @var{status-async-output} contains on-going status information about the
14683 progress of a slow operation. It can be discarded. All status output is
14684 prefixed by @samp{+}.
14687 @cindex async output in @sc{gdb/mi}
14688 @var{exec-async-output} contains asynchronous state change on the target
14689 (stopped, started, disappeared). All async output is prefixed by
14693 @cindex notify output in @sc{gdb/mi}
14694 @var{notify-async-output} contains supplementary information that the
14695 client should handle (e.g., a new breakpoint information). All notify
14696 output is prefixed by @samp{=}.
14699 @cindex console output in @sc{gdb/mi}
14700 @var{console-stream-output} is output that should be displayed as is in the
14701 console. It is the textual response to a CLI command. All the console
14702 output is prefixed by @samp{~}.
14705 @cindex target output in @sc{gdb/mi}
14706 @var{target-stream-output} is the output produced by the target program.
14707 All the target output is prefixed by @samp{@@}.
14710 @cindex log output in @sc{gdb/mi}
14711 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
14712 instance messages that should be displayed as part of an error log. All
14713 the log output is prefixed by @samp{&}.
14716 @cindex list output in @sc{gdb/mi}
14717 New @sc{gdb/mi} commands should only output @var{lists} containing
14723 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
14724 details about the various output records.
14726 @node GDB/MI Simple Examples
14727 @subsection Simple Examples of @sc{gdb/mi} Interaction
14728 @cindex @sc{gdb/mi}, simple examples
14730 This subsection presents several simple examples of interaction using
14731 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
14732 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
14733 the output received from @sc{gdb/mi}.
14735 @subsubheading Target Stop
14736 @c Ummm... There is no "-stop" command. This assumes async, no?
14737 Here's an example of stopping the inferior process:
14748 <- *stop,reason="stop",address="0x123",source="a.c:123"
14752 @subsubheading Simple CLI Command
14754 Here's an example of a simple CLI command being passed through
14755 @sc{gdb/mi} and on to the CLI.
14765 @subsubheading Command With Side Effects
14768 -> -symbol-file xyz.exe
14769 <- *breakpoint,nr="3",address="0x123",source="a.c:123"
14773 @subsubheading A Bad Command
14775 Here's what happens if you pass a non-existent command:
14779 <- ^error,msg="Undefined MI command: rubbish"
14783 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14784 @node GDB/MI Compatibility with CLI
14785 @section @sc{gdb/mi} Compatibility with CLI
14787 @cindex compatibility, @sc{gdb/mi} and CLI
14788 @cindex @sc{gdb/mi}, compatibility with CLI
14789 To help users familiar with @value{GDBN}'s existing CLI interface, @sc{gdb/mi}
14790 accepts existing CLI commands. As specified by the syntax, such
14791 commands can be directly entered into the @sc{gdb/mi} interface and @value{GDBN} will
14794 This mechanism is provided as an aid to developers of @sc{gdb/mi}
14795 clients and not as a reliable interface into the CLI. Since the command
14796 is being interpreteted in an environment that assumes @sc{gdb/mi}
14797 behaviour, the exact output of such commands is likely to end up being
14798 an un-supported hybrid of @sc{gdb/mi} and CLI output.
14800 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14801 @node GDB/MI Output Records
14802 @section @sc{gdb/mi} Output Records
14805 * GDB/MI Result Records::
14806 * GDB/MI Stream Records::
14807 * GDB/MI Out-of-band Records::
14810 @node GDB/MI Result Records
14811 @subsection @sc{gdb/mi} Result Records
14813 @cindex result records in @sc{gdb/mi}
14814 @cindex @sc{gdb/mi}, result records
14815 In addition to a number of out-of-band notifications, the response to a
14816 @sc{gdb/mi} command includes one of the following result indications:
14820 @item "^done" [ "," @var{results} ]
14821 The synchronous operation was successful, @code{@var{results}} are the return
14826 @c Is this one correct? Should it be an out-of-band notification?
14827 The asynchronous operation was successfully started. The target is
14830 @item "^error" "," @var{c-string}
14832 The operation failed. The @code{@var{c-string}} contains the corresponding
14836 @node GDB/MI Stream Records
14837 @subsection @sc{gdb/mi} Stream Records
14839 @cindex @sc{gdb/mi}, stream records
14840 @cindex stream records in @sc{gdb/mi}
14841 @value{GDBN} internally maintains a number of output streams: the console, the
14842 target, and the log. The output intended for each of these streams is
14843 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
14845 Each stream record begins with a unique @dfn{prefix character} which
14846 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
14847 Syntax}). In addition to the prefix, each stream record contains a
14848 @code{@var{string-output}}. This is either raw text (with an implicit new
14849 line) or a quoted C string (which does not contain an implicit newline).
14852 @item "~" @var{string-output}
14853 The console output stream contains text that should be displayed in the
14854 CLI console window. It contains the textual responses to CLI commands.
14856 @item "@@" @var{string-output}
14857 The target output stream contains any textual output from the running
14860 @item "&" @var{string-output}
14861 The log stream contains debugging messages being produced by @value{GDBN}'s
14865 @node GDB/MI Out-of-band Records
14866 @subsection @sc{gdb/mi} Out-of-band Records
14868 @cindex out-of-band records in @sc{gdb/mi}
14869 @cindex @sc{gdb/mi}, out-of-band records
14870 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
14871 additional changes that have occurred. Those changes can either be a
14872 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
14873 target activity (e.g., target stopped).
14875 The following is a preliminary list of possible out-of-band records.
14882 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14883 @node GDB/MI Command Description Format
14884 @section @sc{gdb/mi} Command Description Format
14886 The remaining sections describe blocks of commands. Each block of
14887 commands is laid out in a fashion similar to this section.
14889 Note the the line breaks shown in the examples are here only for
14890 readability. They don't appear in the real output.
14891 Also note that the commands with a non-available example (N.A.@:) are
14892 not yet implemented.
14894 @subheading Motivation
14896 The motivation for this collection of commands.
14898 @subheading Introduction
14900 A brief introduction to this collection of commands as a whole.
14902 @subheading Commands
14904 For each command in the block, the following is described:
14906 @subsubheading Synopsis
14909 -command @var{args}@dots{}
14912 @subsubheading @value{GDBN} Command
14914 The corresponding @value{GDBN} CLI command.
14916 @subsubheading Result
14918 @subsubheading Out-of-band
14920 @subsubheading Notes
14922 @subsubheading Example
14925 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14926 @node GDB/MI Breakpoint Table Commands
14927 @section @sc{gdb/mi} Breakpoint table commands
14929 @cindex breakpoint commands for @sc{gdb/mi}
14930 @cindex @sc{gdb/mi}, breakpoint commands
14931 This section documents @sc{gdb/mi} commands for manipulating
14934 @subheading The @code{-break-after} Command
14935 @findex -break-after
14937 @subsubheading Synopsis
14940 -break-after @var{number} @var{count}
14943 The breakpoint number @var{number} is not in effect until it has been
14944 hit @var{count} times. To see how this is reflected in the output of
14945 the @samp{-break-list} command, see the description of the
14946 @samp{-break-list} command below.
14948 @subsubheading @value{GDBN} Command
14950 The corresponding @value{GDBN} command is @samp{ignore}.
14952 @subsubheading Example
14957 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",line="5"@}
14964 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
14965 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14966 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14967 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14968 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14969 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14970 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14971 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
14972 addr="0x000100d0",func="main",file="hello.c",line="5",times="0",
14978 @subheading The @code{-break-catch} Command
14979 @findex -break-catch
14981 @subheading The @code{-break-commands} Command
14982 @findex -break-commands
14986 @subheading The @code{-break-condition} Command
14987 @findex -break-condition
14989 @subsubheading Synopsis
14992 -break-condition @var{number} @var{expr}
14995 Breakpoint @var{number} will stop the program only if the condition in
14996 @var{expr} is true. The condition becomes part of the
14997 @samp{-break-list} output (see the description of the @samp{-break-list}
15000 @subsubheading @value{GDBN} Command
15002 The corresponding @value{GDBN} command is @samp{condition}.
15004 @subsubheading Example
15008 -break-condition 1 1
15012 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15013 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15014 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15015 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15016 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15017 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15018 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15019 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15020 addr="0x000100d0",func="main",file="hello.c",line="5",cond="1",
15021 times="0",ignore="3"@}]@}
15025 @subheading The @code{-break-delete} Command
15026 @findex -break-delete
15028 @subsubheading Synopsis
15031 -break-delete ( @var{breakpoint} )+
15034 Delete the breakpoint(s) whose number(s) are specified in the argument
15035 list. This is obviously reflected in the breakpoint list.
15037 @subsubheading @value{GDBN} command
15039 The corresponding @value{GDBN} command is @samp{delete}.
15041 @subsubheading Example
15049 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
15050 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15051 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15052 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15053 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15054 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15055 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15060 @subheading The @code{-break-disable} Command
15061 @findex -break-disable
15063 @subsubheading Synopsis
15066 -break-disable ( @var{breakpoint} )+
15069 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
15070 break list is now set to @samp{n} for the named @var{breakpoint}(s).
15072 @subsubheading @value{GDBN} Command
15074 The corresponding @value{GDBN} command is @samp{disable}.
15076 @subsubheading Example
15084 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15085 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15086 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15087 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15088 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15089 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15090 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15091 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
15092 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
15096 @subheading The @code{-break-enable} Command
15097 @findex -break-enable
15099 @subsubheading Synopsis
15102 -break-enable ( @var{breakpoint} )+
15105 Enable (previously disabled) @var{breakpoint}(s).
15107 @subsubheading @value{GDBN} Command
15109 The corresponding @value{GDBN} command is @samp{enable}.
15111 @subsubheading Example
15119 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15120 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15121 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15122 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15123 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15124 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15125 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15126 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
15127 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
15131 @subheading The @code{-break-info} Command
15132 @findex -break-info
15134 @subsubheading Synopsis
15137 -break-info @var{breakpoint}
15141 Get information about a single breakpoint.
15143 @subsubheading @value{GDBN} command
15145 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
15147 @subsubheading Example
15150 @subheading The @code{-break-insert} Command
15151 @findex -break-insert
15153 @subsubheading Synopsis
15156 -break-insert [ -t ] [ -h ] [ -r ]
15157 [ -c @var{condition} ] [ -i @var{ignore-count} ]
15158 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
15162 If specified, @var{line}, can be one of:
15169 @item filename:linenum
15170 @item filename:function
15174 The possible optional parameters of this command are:
15178 Insert a tempoary breakpoint.
15180 Insert a hardware breakpoint.
15181 @item -c @var{condition}
15182 Make the breakpoint conditional on @var{condition}.
15183 @item -i @var{ignore-count}
15184 Initialize the @var{ignore-count}.
15186 Insert a regular breakpoint in all the functions whose names match the
15187 given regular expression. Other flags are not applicable to regular
15191 @subsubheading Result
15193 The result is in the form:
15196 ^done,bkptno="@var{number}",func="@var{funcname}",
15197 file="@var{filename}",line="@var{lineno}"
15201 where @var{number} is the @value{GDBN} number for this breakpoint, @var{funcname}
15202 is the name of the function where the breakpoint was inserted,
15203 @var{filename} is the name of the source file which contains this
15204 function, and @var{lineno} is the source line number within that file.
15206 Note: this format is open to change.
15207 @c An out-of-band breakpoint instead of part of the result?
15209 @subsubheading @value{GDBN} Command
15211 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
15212 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
15214 @subsubheading Example
15219 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
15221 -break-insert -t foo
15222 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",line="11"@}
15225 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15226 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15227 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15228 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15229 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15230 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15231 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15232 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15233 addr="0x0001072c", func="main",file="recursive2.c",line="4",times="0"@},
15234 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
15235 addr="0x00010774",func="foo",file="recursive2.c",line="11",times="0"@}]@}
15237 -break-insert -r foo.*
15238 ~int foo(int, int);
15239 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c",line="11"@}
15243 @subheading The @code{-break-list} Command
15244 @findex -break-list
15246 @subsubheading Synopsis
15252 Displays the list of inserted breakpoints, showing the following fields:
15256 number of the breakpoint
15258 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
15260 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
15263 is the breakpoint enabled or no: @samp{y} or @samp{n}
15265 memory location at which the breakpoint is set
15267 logical location of the breakpoint, expressed by function name, file
15270 number of times the breakpoint has been hit
15273 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
15274 @code{body} field is an empty list.
15276 @subsubheading @value{GDBN} Command
15278 The corresponding @value{GDBN} command is @samp{info break}.
15280 @subsubheading Example
15285 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15286 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15287 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15288 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15289 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15290 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15291 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15292 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15293 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
15294 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
15295 addr="0x00010114",func="foo",file="hello.c",line="13",times="0"@}]@}
15299 Here's an example of the result when there are no breakpoints:
15304 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
15305 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15306 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15307 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15308 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15309 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15310 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15315 @subheading The @code{-break-watch} Command
15316 @findex -break-watch
15318 @subsubheading Synopsis
15321 -break-watch [ -a | -r ]
15324 Create a watchpoint. With the @samp{-a} option it will create an
15325 @dfn{access} watchpoint, i.e. a watchpoint that triggers either on a
15326 read from or on a write to the memory location. With the @samp{-r}
15327 option, the watchpoint created is a @dfn{read} watchpoint, i.e. it will
15328 trigger only when the memory location is accessed for reading. Without
15329 either of the options, the watchpoint created is a regular watchpoint,
15330 i.e. it will trigger when the memory location is accessed for writing.
15331 @xref{Set Watchpoints, , Setting watchpoints}.
15333 Note that @samp{-break-list} will report a single list of watchpoints and
15334 breakpoints inserted.
15336 @subsubheading @value{GDBN} Command
15338 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
15341 @subsubheading Example
15343 Setting a watchpoint on a variable in the @code{main} function:
15348 ^done,wpt=@{number="2",exp="x"@}
15352 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
15353 value=@{old="-268439212",new="55"@},
15354 frame=@{func="main",args=[],file="recursive2.c",line="5"@}
15358 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
15359 the program execution twice: first for the variable changing value, then
15360 for the watchpoint going out of scope.
15365 ^done,wpt=@{number="5",exp="C"@}
15369 ^done,reason="watchpoint-trigger",
15370 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
15371 frame=@{func="callee4",args=[],
15372 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
15376 ^done,reason="watchpoint-scope",wpnum="5",
15377 frame=@{func="callee3",args=[@{name="strarg",
15378 value="0x11940 \"A string argument.\""@}],
15379 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
15383 Listing breakpoints and watchpoints, at different points in the program
15384 execution. Note that once the watchpoint goes out of scope, it is
15390 ^done,wpt=@{number="2",exp="C"@}
15393 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15394 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15395 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15396 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15397 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15398 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15399 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15400 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15401 addr="0x00010734",func="callee4",
15402 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
15403 bkpt=@{number="2",type="watchpoint",disp="keep",
15404 enabled="y",addr="",what="C",times="0"@}]@}
15408 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
15409 value=@{old="-276895068",new="3"@},
15410 frame=@{func="callee4",args=[],
15411 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
15414 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15415 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15416 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15417 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15418 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15419 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15420 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15421 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15422 addr="0x00010734",func="callee4",
15423 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
15424 bkpt=@{number="2",type="watchpoint",disp="keep",
15425 enabled="y",addr="",what="C",times="-5"@}]@}
15429 ^done,reason="watchpoint-scope",wpnum="2",
15430 frame=@{func="callee3",args=[@{name="strarg",
15431 value="0x11940 \"A string argument.\""@}],
15432 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
15435 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15436 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15437 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15438 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15439 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15440 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15441 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15442 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15443 addr="0x00010734",func="callee4",
15444 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@}]@}
15448 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15449 @node GDB/MI Data Manipulation
15450 @section @sc{gdb/mi} Data Manipulation
15452 @cindex data manipulation, in @sc{gdb/mi}
15453 @cindex @sc{gdb/mi}, data manipulation
15454 This section describes the @sc{gdb/mi} commands that manipulate data:
15455 examine memory and registers, evaluate expressions, etc.
15457 @c REMOVED FROM THE INTERFACE.
15458 @c @subheading -data-assign
15459 @c Change the value of a program variable. Plenty of side effects.
15460 @c @subsubheading GDB command
15462 @c @subsubheading Example
15465 @subheading The @code{-data-disassemble} Command
15466 @findex -data-disassemble
15468 @subsubheading Synopsis
15472 [ -s @var{start-addr} -e @var{end-addr} ]
15473 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
15481 @item @var{start-addr}
15482 is the beginning address (or @code{$pc})
15483 @item @var{end-addr}
15485 @item @var{filename}
15486 is the name of the file to disassemble
15487 @item @var{linenum}
15488 is the line number to disassemble around
15490 is the the number of disassembly lines to be produced. If it is -1,
15491 the whole function will be disassembled, in case no @var{end-addr} is
15492 specified. If @var{end-addr} is specified as a non-zero value, and
15493 @var{lines} is lower than the number of disassembly lines between
15494 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
15495 displayed; if @var{lines} is higher than the number of lines between
15496 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
15499 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
15503 @subsubheading Result
15505 The output for each instruction is composed of four fields:
15514 Note that whatever included in the instruction field, is not manipulated
15515 directely by @sc{gdb/mi}, i.e. it is not possible to adjust its format.
15517 @subsubheading @value{GDBN} Command
15519 There's no direct mapping from this command to the CLI.
15521 @subsubheading Example
15523 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
15527 -data-disassemble -s $pc -e "$pc + 20" -- 0
15530 @{address="0x000107c0",func-name="main",offset="4",
15531 inst="mov 2, %o0"@},
15532 @{address="0x000107c4",func-name="main",offset="8",
15533 inst="sethi %hi(0x11800), %o2"@},
15534 @{address="0x000107c8",func-name="main",offset="12",
15535 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
15536 @{address="0x000107cc",func-name="main",offset="16",
15537 inst="sethi %hi(0x11800), %o2"@},
15538 @{address="0x000107d0",func-name="main",offset="20",
15539 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
15543 Disassemble the whole @code{main} function. Line 32 is part of
15547 -data-disassemble -f basics.c -l 32 -- 0
15549 @{address="0x000107bc",func-name="main",offset="0",
15550 inst="save %sp, -112, %sp"@},
15551 @{address="0x000107c0",func-name="main",offset="4",
15552 inst="mov 2, %o0"@},
15553 @{address="0x000107c4",func-name="main",offset="8",
15554 inst="sethi %hi(0x11800), %o2"@},
15556 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
15557 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
15561 Disassemble 3 instructions from the start of @code{main}:
15565 -data-disassemble -f basics.c -l 32 -n 3 -- 0
15567 @{address="0x000107bc",func-name="main",offset="0",
15568 inst="save %sp, -112, %sp"@},
15569 @{address="0x000107c0",func-name="main",offset="4",
15570 inst="mov 2, %o0"@},
15571 @{address="0x000107c4",func-name="main",offset="8",
15572 inst="sethi %hi(0x11800), %o2"@}]
15576 Disassemble 3 instructions from the start of @code{main} in mixed mode:
15580 -data-disassemble -f basics.c -l 32 -n 3 -- 1
15582 src_and_asm_line=@{line="31",
15583 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
15584 testsuite/gdb.mi/basics.c",line_asm_insn=[
15585 @{address="0x000107bc",func-name="main",offset="0",
15586 inst="save %sp, -112, %sp"@}]@},
15587 src_and_asm_line=@{line="32",
15588 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
15589 testsuite/gdb.mi/basics.c",line_asm_insn=[
15590 @{address="0x000107c0",func-name="main",offset="4",
15591 inst="mov 2, %o0"@},
15592 @{address="0x000107c4",func-name="main",offset="8",
15593 inst="sethi %hi(0x11800), %o2"@}]@}]
15598 @subheading The @code{-data-evaluate-expression} Command
15599 @findex -data-evaluate-expression
15601 @subsubheading Synopsis
15604 -data-evaluate-expression @var{expr}
15607 Evaluate @var{expr} as an expression. The expression could contain an
15608 inferior function call. The function call will execute synchronously.
15609 If the expression contains spaces, it must be enclosed in double quotes.
15611 @subsubheading @value{GDBN} Command
15613 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
15614 @samp{call}. In @code{gdbtk} only, there's a corresponding
15615 @samp{gdb_eval} command.
15617 @subsubheading Example
15619 In the following example, the numbers that precede the commands are the
15620 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
15621 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
15625 211-data-evaluate-expression A
15628 311-data-evaluate-expression &A
15629 311^done,value="0xefffeb7c"
15631 411-data-evaluate-expression A+3
15634 511-data-evaluate-expression "A + 3"
15640 @subheading The @code{-data-list-changed-registers} Command
15641 @findex -data-list-changed-registers
15643 @subsubheading Synopsis
15646 -data-list-changed-registers
15649 Display a list of the registers that have changed.
15651 @subsubheading @value{GDBN} Command
15653 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
15654 has the corresponding command @samp{gdb_changed_register_list}.
15656 @subsubheading Example
15658 On a PPC MBX board:
15666 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
15667 args=[],file="try.c",line="5"@}
15669 -data-list-changed-registers
15670 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
15671 "10","11","13","14","15","16","17","18","19","20","21","22","23",
15672 "24","25","26","27","28","30","31","64","65","66","67","69"]
15677 @subheading The @code{-data-list-register-names} Command
15678 @findex -data-list-register-names
15680 @subsubheading Synopsis
15683 -data-list-register-names [ ( @var{regno} )+ ]
15686 Show a list of register names for the current target. If no arguments
15687 are given, it shows a list of the names of all the registers. If
15688 integer numbers are given as arguments, it will print a list of the
15689 names of the registers corresponding to the arguments. To ensure
15690 consistency between a register name and its number, the output list may
15691 include empty register names.
15693 @subsubheading @value{GDBN} Command
15695 @value{GDBN} does not have a command which corresponds to
15696 @samp{-data-list-register-names}. In @code{gdbtk} there is a
15697 corresponding command @samp{gdb_regnames}.
15699 @subsubheading Example
15701 For the PPC MBX board:
15704 -data-list-register-names
15705 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
15706 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
15707 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
15708 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
15709 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
15710 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
15711 "", "pc","ps","cr","lr","ctr","xer"]
15713 -data-list-register-names 1 2 3
15714 ^done,register-names=["r1","r2","r3"]
15718 @subheading The @code{-data-list-register-values} Command
15719 @findex -data-list-register-values
15721 @subsubheading Synopsis
15724 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
15727 Display the registers' contents. @var{fmt} is the format according to
15728 which the registers' contents are to be returned, followed by an optional
15729 list of numbers specifying the registers to display. A missing list of
15730 numbers indicates that the contents of all the registers must be returned.
15732 Allowed formats for @var{fmt} are:
15749 @subsubheading @value{GDBN} Command
15751 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
15752 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
15754 @subsubheading Example
15756 For a PPC MBX board (note: line breaks are for readability only, they
15757 don't appear in the actual output):
15761 -data-list-register-values r 64 65
15762 ^done,register-values=[@{number="64",value="0xfe00a300"@},
15763 @{number="65",value="0x00029002"@}]
15765 -data-list-register-values x
15766 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
15767 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
15768 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
15769 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
15770 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
15771 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
15772 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
15773 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
15774 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
15775 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
15776 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
15777 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
15778 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
15779 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
15780 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
15781 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
15782 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
15783 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
15784 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
15785 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
15786 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
15787 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
15788 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
15789 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
15790 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
15791 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
15792 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
15793 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
15794 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
15795 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
15796 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
15797 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
15798 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
15799 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
15800 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
15801 @{number="69",value="0x20002b03"@}]
15806 @subheading The @code{-data-read-memory} Command
15807 @findex -data-read-memory
15809 @subsubheading Synopsis
15812 -data-read-memory [ -o @var{byte-offset} ]
15813 @var{address} @var{word-format} @var{word-size}
15814 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
15821 @item @var{address}
15822 An expression specifying the address of the first memory word to be
15823 read. Complex expressions containing embedded white space should be
15824 quoted using the C convention.
15826 @item @var{word-format}
15827 The format to be used to print the memory words. The notation is the
15828 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
15831 @item @var{word-size}
15832 The size of each memory word in bytes.
15834 @item @var{nr-rows}
15835 The number of rows in the output table.
15837 @item @var{nr-cols}
15838 The number of columns in the output table.
15841 If present, indicates that each row should include an @sc{ascii} dump. The
15842 value of @var{aschar} is used as a padding character when a byte is not a
15843 member of the printable @sc{ascii} character set (printable @sc{ascii}
15844 characters are those whose code is between 32 and 126, inclusively).
15846 @item @var{byte-offset}
15847 An offset to add to the @var{address} before fetching memory.
15850 This command displays memory contents as a table of @var{nr-rows} by
15851 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
15852 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
15853 (returned as @samp{total-bytes}). Should less than the requested number
15854 of bytes be returned by the target, the missing words are identified
15855 using @samp{N/A}. The number of bytes read from the target is returned
15856 in @samp{nr-bytes} and the starting address used to read memory in
15859 The address of the next/previous row or page is available in
15860 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
15863 @subsubheading @value{GDBN} Command
15865 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
15866 @samp{gdb_get_mem} memory read command.
15868 @subsubheading Example
15870 Read six bytes of memory starting at @code{bytes+6} but then offset by
15871 @code{-6} bytes. Format as three rows of two columns. One byte per
15872 word. Display each word in hex.
15876 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
15877 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
15878 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
15879 prev-page="0x0000138a",memory=[
15880 @{addr="0x00001390",data=["0x00","0x01"]@},
15881 @{addr="0x00001392",data=["0x02","0x03"]@},
15882 @{addr="0x00001394",data=["0x04","0x05"]@}]
15886 Read two bytes of memory starting at address @code{shorts + 64} and
15887 display as a single word formatted in decimal.
15891 5-data-read-memory shorts+64 d 2 1 1
15892 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
15893 next-row="0x00001512",prev-row="0x0000150e",
15894 next-page="0x00001512",prev-page="0x0000150e",memory=[
15895 @{addr="0x00001510",data=["128"]@}]
15899 Read thirty two bytes of memory starting at @code{bytes+16} and format
15900 as eight rows of four columns. Include a string encoding with @samp{x}
15901 used as the non-printable character.
15905 4-data-read-memory bytes+16 x 1 8 4 x
15906 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
15907 next-row="0x000013c0",prev-row="0x0000139c",
15908 next-page="0x000013c0",prev-page="0x00001380",memory=[
15909 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
15910 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
15911 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
15912 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
15913 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
15914 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
15915 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
15916 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
15920 @subheading The @code{-display-delete} Command
15921 @findex -display-delete
15923 @subsubheading Synopsis
15926 -display-delete @var{number}
15929 Delete the display @var{number}.
15931 @subsubheading @value{GDBN} Command
15933 The corresponding @value{GDBN} command is @samp{delete display}.
15935 @subsubheading Example
15939 @subheading The @code{-display-disable} Command
15940 @findex -display-disable
15942 @subsubheading Synopsis
15945 -display-disable @var{number}
15948 Disable display @var{number}.
15950 @subsubheading @value{GDBN} Command
15952 The corresponding @value{GDBN} command is @samp{disable display}.
15954 @subsubheading Example
15958 @subheading The @code{-display-enable} Command
15959 @findex -display-enable
15961 @subsubheading Synopsis
15964 -display-enable @var{number}
15967 Enable display @var{number}.
15969 @subsubheading @value{GDBN} Command
15971 The corresponding @value{GDBN} command is @samp{enable display}.
15973 @subsubheading Example
15977 @subheading The @code{-display-insert} Command
15978 @findex -display-insert
15980 @subsubheading Synopsis
15983 -display-insert @var{expression}
15986 Display @var{expression} every time the program stops.
15988 @subsubheading @value{GDBN} Command
15990 The corresponding @value{GDBN} command is @samp{display}.
15992 @subsubheading Example
15996 @subheading The @code{-display-list} Command
15997 @findex -display-list
15999 @subsubheading Synopsis
16005 List the displays. Do not show the current values.
16007 @subsubheading @value{GDBN} Command
16009 The corresponding @value{GDBN} command is @samp{info display}.
16011 @subsubheading Example
16015 @subheading The @code{-environment-cd} Command
16016 @findex -environment-cd
16018 @subsubheading Synopsis
16021 -environment-cd @var{pathdir}
16024 Set @value{GDBN}'s working directory.
16026 @subsubheading @value{GDBN} Command
16028 The corresponding @value{GDBN} command is @samp{cd}.
16030 @subsubheading Example
16034 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
16040 @subheading The @code{-environment-directory} Command
16041 @findex -environment-directory
16043 @subsubheading Synopsis
16046 -environment-directory [ -r ] [ @var{pathdir} ]+
16049 Add directories @var{pathdir} to beginning of search path for source files.
16050 If the @samp{-r} option is used, the search path is reset to the default
16051 search path. If directories @var{pathdir} are supplied in addition to the
16052 @samp{-r} option, the search path is first reset and then addition
16054 Multiple directories may be specified, separated by blanks. Specifying
16055 multiple directories in a single command
16056 results in the directories added to the beginning of the
16057 search path in the same order they were presented in the command.
16058 If blanks are needed as
16059 part of a directory name, double-quotes should be used around
16060 the name. In the command output, the path will show up separated
16061 by the system directory-separator character. The directory-seperator
16062 character must not be used
16063 in any directory name.
16064 If no directories are specified, the current search path is displayed.
16066 @subsubheading @value{GDBN} Command
16068 The corresponding @value{GDBN} command is @samp{dir}.
16070 @subsubheading Example
16074 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
16075 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
16077 -environment-directory ""
16078 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
16080 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
16081 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
16083 -environment-directory -r
16084 ^done,source-path="$cdir:$cwd"
16089 @subheading The @code{-environment-path} Command
16090 @findex -environment-path
16092 @subsubheading Synopsis
16095 -environment-path [ -r ] [ @var{pathdir} ]+
16098 Add directories @var{pathdir} to beginning of search path for object files.
16099 If the @samp{-r} option is used, the search path is reset to the original
16100 search path that existed at gdb start-up. If directories @var{pathdir} are
16101 supplied in addition to the
16102 @samp{-r} option, the search path is first reset and then addition
16104 Multiple directories may be specified, separated by blanks. Specifying
16105 multiple directories in a single command
16106 results in the directories added to the beginning of the
16107 search path in the same order they were presented in the command.
16108 If blanks are needed as
16109 part of a directory name, double-quotes should be used around
16110 the name. In the command output, the path will show up separated
16111 by the system directory-separator character. The directory-seperator
16112 character must not be used
16113 in any directory name.
16114 If no directories are specified, the current path is displayed.
16117 @subsubheading @value{GDBN} Command
16119 The corresponding @value{GDBN} command is @samp{path}.
16121 @subsubheading Example
16126 ^done,path="/usr/bin"
16128 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
16129 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
16131 -environment-path -r /usr/local/bin
16132 ^done,path="/usr/local/bin:/usr/bin"
16137 @subheading The @code{-environment-pwd} Command
16138 @findex -environment-pwd
16140 @subsubheading Synopsis
16146 Show the current working directory.
16148 @subsubheading @value{GDBN} command
16150 The corresponding @value{GDBN} command is @samp{pwd}.
16152 @subsubheading Example
16157 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
16161 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16162 @node GDB/MI Program Control
16163 @section @sc{gdb/mi} Program control
16165 @subsubheading Program termination
16167 As a result of execution, the inferior program can run to completion, if
16168 it doesn't encounter any breakpoints. In this case the output will
16169 include an exit code, if the program has exited exceptionally.
16171 @subsubheading Examples
16174 Program exited normally:
16182 *stopped,reason="exited-normally"
16187 Program exited exceptionally:
16195 *stopped,reason="exited",exit-code="01"
16199 Another way the program can terminate is if it receives a signal such as
16200 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
16204 *stopped,reason="exited-signalled",signal-name="SIGINT",
16205 signal-meaning="Interrupt"
16209 @subheading The @code{-exec-abort} Command
16210 @findex -exec-abort
16212 @subsubheading Synopsis
16218 Kill the inferior running program.
16220 @subsubheading @value{GDBN} Command
16222 The corresponding @value{GDBN} command is @samp{kill}.
16224 @subsubheading Example
16228 @subheading The @code{-exec-arguments} Command
16229 @findex -exec-arguments
16231 @subsubheading Synopsis
16234 -exec-arguments @var{args}
16237 Set the inferior program arguments, to be used in the next
16240 @subsubheading @value{GDBN} Command
16242 The corresponding @value{GDBN} command is @samp{set args}.
16244 @subsubheading Example
16247 Don't have one around.
16250 @subheading The @code{-exec-continue} Command
16251 @findex -exec-continue
16253 @subsubheading Synopsis
16259 Asynchronous command. Resumes the execution of the inferior program
16260 until a breakpoint is encountered, or until the inferior exits.
16262 @subsubheading @value{GDBN} Command
16264 The corresponding @value{GDBN} corresponding is @samp{continue}.
16266 @subsubheading Example
16273 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
16274 file="hello.c",line="13"@}
16279 @subheading The @code{-exec-finish} Command
16280 @findex -exec-finish
16282 @subsubheading Synopsis
16288 Asynchronous command. Resumes the execution of the inferior program
16289 until the current function is exited. Displays the results returned by
16292 @subsubheading @value{GDBN} Command
16294 The corresponding @value{GDBN} command is @samp{finish}.
16296 @subsubheading Example
16298 Function returning @code{void}.
16305 *stopped,reason="function-finished",frame=@{func="main",args=[],
16306 file="hello.c",line="7"@}
16310 Function returning other than @code{void}. The name of the internal
16311 @value{GDBN} variable storing the result is printed, together with the
16318 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
16319 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
16320 file="recursive2.c",line="14"@},
16321 gdb-result-var="$1",return-value="0"
16326 @subheading The @code{-exec-interrupt} Command
16327 @findex -exec-interrupt
16329 @subsubheading Synopsis
16335 Asynchronous command. Interrupts the background execution of the target.
16336 Note how the token associated with the stop message is the one for the
16337 execution command that has been interrupted. The token for the interrupt
16338 itself only appears in the @samp{^done} output. If the user is trying to
16339 interrupt a non-running program, an error message will be printed.
16341 @subsubheading @value{GDBN} Command
16343 The corresponding @value{GDBN} command is @samp{interrupt}.
16345 @subsubheading Example
16356 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
16357 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",line="13"@}
16362 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
16367 @subheading The @code{-exec-next} Command
16370 @subsubheading Synopsis
16376 Asynchronous command. Resumes execution of the inferior program, stopping
16377 when the beginning of the next source line is reached.
16379 @subsubheading @value{GDBN} Command
16381 The corresponding @value{GDBN} command is @samp{next}.
16383 @subsubheading Example
16389 *stopped,reason="end-stepping-range",line="8",file="hello.c"
16394 @subheading The @code{-exec-next-instruction} Command
16395 @findex -exec-next-instruction
16397 @subsubheading Synopsis
16400 -exec-next-instruction
16403 Asynchronous command. Executes one machine instruction. If the
16404 instruction is a function call continues until the function returns. If
16405 the program stops at an instruction in the middle of a source line, the
16406 address will be printed as well.
16408 @subsubheading @value{GDBN} Command
16410 The corresponding @value{GDBN} command is @samp{nexti}.
16412 @subsubheading Example
16416 -exec-next-instruction
16420 *stopped,reason="end-stepping-range",
16421 addr="0x000100d4",line="5",file="hello.c"
16426 @subheading The @code{-exec-return} Command
16427 @findex -exec-return
16429 @subsubheading Synopsis
16435 Makes current function return immediately. Doesn't execute the inferior.
16436 Displays the new current frame.
16438 @subsubheading @value{GDBN} Command
16440 The corresponding @value{GDBN} command is @samp{return}.
16442 @subsubheading Example
16446 200-break-insert callee4
16447 200^done,bkpt=@{number="1",addr="0x00010734",
16448 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
16453 000*stopped,reason="breakpoint-hit",bkptno="1",
16454 frame=@{func="callee4",args=[],
16455 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
16461 111^done,frame=@{level="0",func="callee3",
16462 args=[@{name="strarg",
16463 value="0x11940 \"A string argument.\""@}],
16464 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
16469 @subheading The @code{-exec-run} Command
16472 @subsubheading Synopsis
16478 Asynchronous command. Starts execution of the inferior from the
16479 beginning. The inferior executes until either a breakpoint is
16480 encountered or the program exits.
16482 @subsubheading @value{GDBN} Command
16484 The corresponding @value{GDBN} command is @samp{run}.
16486 @subsubheading Example
16491 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
16496 *stopped,reason="breakpoint-hit",bkptno="1",
16497 frame=@{func="main",args=[],file="recursive2.c",line="4"@}
16502 @subheading The @code{-exec-show-arguments} Command
16503 @findex -exec-show-arguments
16505 @subsubheading Synopsis
16508 -exec-show-arguments
16511 Print the arguments of the program.
16513 @subsubheading @value{GDBN} Command
16515 The corresponding @value{GDBN} command is @samp{show args}.
16517 @subsubheading Example
16520 @c @subheading -exec-signal
16522 @subheading The @code{-exec-step} Command
16525 @subsubheading Synopsis
16531 Asynchronous command. Resumes execution of the inferior program, stopping
16532 when the beginning of the next source line is reached, if the next
16533 source line is not a function call. If it is, stop at the first
16534 instruction of the called function.
16536 @subsubheading @value{GDBN} Command
16538 The corresponding @value{GDBN} command is @samp{step}.
16540 @subsubheading Example
16542 Stepping into a function:
16548 *stopped,reason="end-stepping-range",
16549 frame=@{func="foo",args=[@{name="a",value="10"@},
16550 @{name="b",value="0"@}],file="recursive2.c",line="11"@}
16560 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
16565 @subheading The @code{-exec-step-instruction} Command
16566 @findex -exec-step-instruction
16568 @subsubheading Synopsis
16571 -exec-step-instruction
16574 Asynchronous command. Resumes the inferior which executes one machine
16575 instruction. The output, once @value{GDBN} has stopped, will vary depending on
16576 whether we have stopped in the middle of a source line or not. In the
16577 former case, the address at which the program stopped will be printed as
16580 @subsubheading @value{GDBN} Command
16582 The corresponding @value{GDBN} command is @samp{stepi}.
16584 @subsubheading Example
16588 -exec-step-instruction
16592 *stopped,reason="end-stepping-range",
16593 frame=@{func="foo",args=[],file="try.c",line="10"@}
16595 -exec-step-instruction
16599 *stopped,reason="end-stepping-range",
16600 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",line="10"@}
16605 @subheading The @code{-exec-until} Command
16606 @findex -exec-until
16608 @subsubheading Synopsis
16611 -exec-until [ @var{location} ]
16614 Asynchronous command. Executes the inferior until the @var{location}
16615 specified in the argument is reached. If there is no argument, the inferior
16616 executes until a source line greater than the current one is reached.
16617 The reason for stopping in this case will be @samp{location-reached}.
16619 @subsubheading @value{GDBN} Command
16621 The corresponding @value{GDBN} command is @samp{until}.
16623 @subsubheading Example
16627 -exec-until recursive2.c:6
16631 *stopped,reason="location-reached",frame=@{func="main",args=[],
16632 file="recursive2.c",line="6"@}
16637 @subheading -file-clear
16638 Is this going away????
16642 @subheading The @code{-file-exec-and-symbols} Command
16643 @findex -file-exec-and-symbols
16645 @subsubheading Synopsis
16648 -file-exec-and-symbols @var{file}
16651 Specify the executable file to be debugged. This file is the one from
16652 which the symbol table is also read. If no file is specified, the
16653 command clears the executable and symbol information. If breakpoints
16654 are set when using this command with no arguments, @value{GDBN} will produce
16655 error messages. Otherwise, no output is produced, except a completion
16658 @subsubheading @value{GDBN} Command
16660 The corresponding @value{GDBN} command is @samp{file}.
16662 @subsubheading Example
16666 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
16672 @subheading The @code{-file-exec-file} Command
16673 @findex -file-exec-file
16675 @subsubheading Synopsis
16678 -file-exec-file @var{file}
16681 Specify the executable file to be debugged. Unlike
16682 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
16683 from this file. If used without argument, @value{GDBN} clears the information
16684 about the executable file. No output is produced, except a completion
16687 @subsubheading @value{GDBN} Command
16689 The corresponding @value{GDBN} command is @samp{exec-file}.
16691 @subsubheading Example
16695 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
16701 @subheading The @code{-file-list-exec-sections} Command
16702 @findex -file-list-exec-sections
16704 @subsubheading Synopsis
16707 -file-list-exec-sections
16710 List the sections of the current executable file.
16712 @subsubheading @value{GDBN} Command
16714 The @value{GDBN} command @samp{info file} shows, among the rest, the same
16715 information as this command. @code{gdbtk} has a corresponding command
16716 @samp{gdb_load_info}.
16718 @subsubheading Example
16722 @subheading The @code{-file-list-exec-source-file} Command
16723 @findex -file-list-exec-source-file
16725 @subsubheading Synopsis
16728 -file-list-exec-source-file
16731 List the line number, the current source file, and the absolute path
16732 to the current source file for the current executable.
16734 @subsubheading @value{GDBN} Command
16736 There's no @value{GDBN} command which directly corresponds to this one.
16738 @subsubheading Example
16742 123-file-list-exec-source-file
16743 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
16748 @subheading The @code{-file-list-exec-source-files} Command
16749 @findex -file-list-exec-source-files
16751 @subsubheading Synopsis
16754 -file-list-exec-source-files
16757 List the source files for the current executable.
16759 @subsubheading @value{GDBN} Command
16761 There's no @value{GDBN} command which directly corresponds to this one.
16762 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
16764 @subsubheading Example
16768 @subheading The @code{-file-list-shared-libraries} Command
16769 @findex -file-list-shared-libraries
16771 @subsubheading Synopsis
16774 -file-list-shared-libraries
16777 List the shared libraries in the program.
16779 @subsubheading @value{GDBN} Command
16781 The corresponding @value{GDBN} command is @samp{info shared}.
16783 @subsubheading Example
16787 @subheading The @code{-file-list-symbol-files} Command
16788 @findex -file-list-symbol-files
16790 @subsubheading Synopsis
16793 -file-list-symbol-files
16798 @subsubheading @value{GDBN} Command
16800 The corresponding @value{GDBN} command is @samp{info file} (part of it).
16802 @subsubheading Example
16806 @subheading The @code{-file-symbol-file} Command
16807 @findex -file-symbol-file
16809 @subsubheading Synopsis
16812 -file-symbol-file @var{file}
16815 Read symbol table info from the specified @var{file} argument. When
16816 used without arguments, clears @value{GDBN}'s symbol table info. No output is
16817 produced, except for a completion notification.
16819 @subsubheading @value{GDBN} Command
16821 The corresponding @value{GDBN} command is @samp{symbol-file}.
16823 @subsubheading Example
16827 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
16832 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16833 @node GDB/MI Miscellaneous Commands
16834 @section Miscellaneous @value{GDBN} commands in @sc{gdb/mi}
16836 @c @subheading -gdb-complete
16838 @subheading The @code{-gdb-exit} Command
16841 @subsubheading Synopsis
16847 Exit @value{GDBN} immediately.
16849 @subsubheading @value{GDBN} Command
16851 Approximately corresponds to @samp{quit}.
16853 @subsubheading Example
16860 @subheading The @code{-gdb-set} Command
16863 @subsubheading Synopsis
16869 Set an internal @value{GDBN} variable.
16870 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
16872 @subsubheading @value{GDBN} Command
16874 The corresponding @value{GDBN} command is @samp{set}.
16876 @subsubheading Example
16886 @subheading The @code{-gdb-show} Command
16889 @subsubheading Synopsis
16895 Show the current value of a @value{GDBN} variable.
16897 @subsubheading @value{GDBN} command
16899 The corresponding @value{GDBN} command is @samp{show}.
16901 @subsubheading Example
16910 @c @subheading -gdb-source
16913 @subheading The @code{-gdb-version} Command
16914 @findex -gdb-version
16916 @subsubheading Synopsis
16922 Show version information for @value{GDBN}. Used mostly in testing.
16924 @subsubheading @value{GDBN} Command
16926 There's no equivalent @value{GDBN} command. @value{GDBN} by default shows this
16927 information when you start an interactive session.
16929 @subsubheading Example
16931 @c This example modifies the actual output from GDB to avoid overfull
16937 ~Copyright 2000 Free Software Foundation, Inc.
16938 ~GDB is free software, covered by the GNU General Public License, and
16939 ~you are welcome to change it and/or distribute copies of it under
16940 ~ certain conditions.
16941 ~Type "show copying" to see the conditions.
16942 ~There is absolutely no warranty for GDB. Type "show warranty" for
16944 ~This GDB was configured as
16945 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
16950 @subheading The @code{-interpreter-exec} Command
16951 @findex -interpreter-exec
16953 @subheading Synopsis
16956 -interpreter-exec @var{interpreter} @var{command}
16959 Execute the specified @var{command} in the given @var{interpreter}.
16961 @subheading @value{GDBN} Command
16963 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
16965 @subheading Example
16969 -interpreter-exec console "break main"
16970 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
16971 &"During symbol reading, bad structure-type format.\n"
16972 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
16978 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16979 @node GDB/MI Kod Commands
16980 @section @sc{gdb/mi} Kod Commands
16982 The Kod commands are not implemented.
16984 @c @subheading -kod-info
16986 @c @subheading -kod-list
16988 @c @subheading -kod-list-object-types
16990 @c @subheading -kod-show
16992 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16993 @node GDB/MI Memory Overlay Commands
16994 @section @sc{gdb/mi} Memory Overlay Commands
16996 The memory overlay commands are not implemented.
16998 @c @subheading -overlay-auto
17000 @c @subheading -overlay-list-mapping-state
17002 @c @subheading -overlay-list-overlays
17004 @c @subheading -overlay-map
17006 @c @subheading -overlay-off
17008 @c @subheading -overlay-on
17010 @c @subheading -overlay-unmap
17012 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17013 @node GDB/MI Signal Handling Commands
17014 @section @sc{gdb/mi} Signal Handling Commands
17016 Signal handling commands are not implemented.
17018 @c @subheading -signal-handle
17020 @c @subheading -signal-list-handle-actions
17022 @c @subheading -signal-list-signal-types
17026 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17027 @node GDB/MI Stack Manipulation
17028 @section @sc{gdb/mi} Stack Manipulation Commands
17031 @subheading The @code{-stack-info-frame} Command
17032 @findex -stack-info-frame
17034 @subsubheading Synopsis
17040 Get info on the current frame.
17042 @subsubheading @value{GDBN} Command
17044 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
17045 (without arguments).
17047 @subsubheading Example
17050 @subheading The @code{-stack-info-depth} Command
17051 @findex -stack-info-depth
17053 @subsubheading Synopsis
17056 -stack-info-depth [ @var{max-depth} ]
17059 Return the depth of the stack. If the integer argument @var{max-depth}
17060 is specified, do not count beyond @var{max-depth} frames.
17062 @subsubheading @value{GDBN} Command
17064 There's no equivalent @value{GDBN} command.
17066 @subsubheading Example
17068 For a stack with frame levels 0 through 11:
17075 -stack-info-depth 4
17078 -stack-info-depth 12
17081 -stack-info-depth 11
17084 -stack-info-depth 13
17089 @subheading The @code{-stack-list-arguments} Command
17090 @findex -stack-list-arguments
17092 @subsubheading Synopsis
17095 -stack-list-arguments @var{show-values}
17096 [ @var{low-frame} @var{high-frame} ]
17099 Display a list of the arguments for the frames between @var{low-frame}
17100 and @var{high-frame} (inclusive). If @var{low-frame} and
17101 @var{high-frame} are not provided, list the arguments for the whole call
17104 The @var{show-values} argument must have a value of 0 or 1. A value of
17105 0 means that only the names of the arguments are listed, a value of 1
17106 means that both names and values of the arguments are printed.
17108 @subsubheading @value{GDBN} Command
17110 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
17111 @samp{gdb_get_args} command which partially overlaps with the
17112 functionality of @samp{-stack-list-arguments}.
17114 @subsubheading Example
17121 frame=@{level="0",addr="0x00010734",func="callee4",
17122 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
17123 frame=@{level="1",addr="0x0001076c",func="callee3",
17124 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
17125 frame=@{level="2",addr="0x0001078c",func="callee2",
17126 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
17127 frame=@{level="3",addr="0x000107b4",func="callee1",
17128 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
17129 frame=@{level="4",addr="0x000107e0",func="main",
17130 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
17132 -stack-list-arguments 0
17135 frame=@{level="0",args=[]@},
17136 frame=@{level="1",args=[name="strarg"]@},
17137 frame=@{level="2",args=[name="intarg",name="strarg"]@},
17138 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
17139 frame=@{level="4",args=[]@}]
17141 -stack-list-arguments 1
17144 frame=@{level="0",args=[]@},
17146 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
17147 frame=@{level="2",args=[
17148 @{name="intarg",value="2"@},
17149 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
17150 @{frame=@{level="3",args=[
17151 @{name="intarg",value="2"@},
17152 @{name="strarg",value="0x11940 \"A string argument.\""@},
17153 @{name="fltarg",value="3.5"@}]@},
17154 frame=@{level="4",args=[]@}]
17156 -stack-list-arguments 0 2 2
17157 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
17159 -stack-list-arguments 1 2 2
17160 ^done,stack-args=[frame=@{level="2",
17161 args=[@{name="intarg",value="2"@},
17162 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
17166 @c @subheading -stack-list-exception-handlers
17169 @subheading The @code{-stack-list-frames} Command
17170 @findex -stack-list-frames
17172 @subsubheading Synopsis
17175 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
17178 List the frames currently on the stack. For each frame it displays the
17183 The frame number, 0 being the topmost frame, i.e. the innermost function.
17185 The @code{$pc} value for that frame.
17189 File name of the source file where the function lives.
17191 Line number corresponding to the @code{$pc}.
17194 If invoked without arguments, this command prints a backtrace for the
17195 whole stack. If given two integer arguments, it shows the frames whose
17196 levels are between the two arguments (inclusive). If the two arguments
17197 are equal, it shows the single frame at the corresponding level.
17199 @subsubheading @value{GDBN} Command
17201 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
17203 @subsubheading Example
17205 Full stack backtrace:
17211 [frame=@{level="0",addr="0x0001076c",func="foo",
17212 file="recursive2.c",line="11"@},
17213 frame=@{level="1",addr="0x000107a4",func="foo",
17214 file="recursive2.c",line="14"@},
17215 frame=@{level="2",addr="0x000107a4",func="foo",
17216 file="recursive2.c",line="14"@},
17217 frame=@{level="3",addr="0x000107a4",func="foo",
17218 file="recursive2.c",line="14"@},
17219 frame=@{level="4",addr="0x000107a4",func="foo",
17220 file="recursive2.c",line="14"@},
17221 frame=@{level="5",addr="0x000107a4",func="foo",
17222 file="recursive2.c",line="14"@},
17223 frame=@{level="6",addr="0x000107a4",func="foo",
17224 file="recursive2.c",line="14"@},
17225 frame=@{level="7",addr="0x000107a4",func="foo",
17226 file="recursive2.c",line="14"@},
17227 frame=@{level="8",addr="0x000107a4",func="foo",
17228 file="recursive2.c",line="14"@},
17229 frame=@{level="9",addr="0x000107a4",func="foo",
17230 file="recursive2.c",line="14"@},
17231 frame=@{level="10",addr="0x000107a4",func="foo",
17232 file="recursive2.c",line="14"@},
17233 frame=@{level="11",addr="0x00010738",func="main",
17234 file="recursive2.c",line="4"@}]
17238 Show frames between @var{low_frame} and @var{high_frame}:
17242 -stack-list-frames 3 5
17244 [frame=@{level="3",addr="0x000107a4",func="foo",
17245 file="recursive2.c",line="14"@},
17246 frame=@{level="4",addr="0x000107a4",func="foo",
17247 file="recursive2.c",line="14"@},
17248 frame=@{level="5",addr="0x000107a4",func="foo",
17249 file="recursive2.c",line="14"@}]
17253 Show a single frame:
17257 -stack-list-frames 3 3
17259 [frame=@{level="3",addr="0x000107a4",func="foo",
17260 file="recursive2.c",line="14"@}]
17265 @subheading The @code{-stack-list-locals} Command
17266 @findex -stack-list-locals
17268 @subsubheading Synopsis
17271 -stack-list-locals @var{print-values}
17274 Display the local variable names for the current frame. With an
17275 argument of 0 or @code{--no-values}, prints only the names of the variables.
17276 With argument of 1 or @code{--all-values}, prints also their values. With
17277 argument of 2 or @code{--simple-values}, prints the name, type and value for
17278 simple data types and the name and type for arrays, structures and
17279 unions. In this last case, the idea is that the user can see the
17280 value of simple data types immediately and he can create variable
17281 objects for other data types if he wishes to explore their values in
17284 @subsubheading @value{GDBN} Command
17286 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
17288 @subsubheading Example
17292 -stack-list-locals 0
17293 ^done,locals=[name="A",name="B",name="C"]
17295 -stack-list-locals --all-values
17296 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
17297 @{name="C",value="@{1, 2, 3@}"@}]
17298 -stack-list-locals --simple-values
17299 ^done,locals=[@{name="A",type="int",value="1"@},
17300 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
17305 @subheading The @code{-stack-select-frame} Command
17306 @findex -stack-select-frame
17308 @subsubheading Synopsis
17311 -stack-select-frame @var{framenum}
17314 Change the current frame. Select a different frame @var{framenum} on
17317 @subsubheading @value{GDBN} Command
17319 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
17320 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
17322 @subsubheading Example
17326 -stack-select-frame 2
17331 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17332 @node GDB/MI Symbol Query
17333 @section @sc{gdb/mi} Symbol Query Commands
17336 @subheading The @code{-symbol-info-address} Command
17337 @findex -symbol-info-address
17339 @subsubheading Synopsis
17342 -symbol-info-address @var{symbol}
17345 Describe where @var{symbol} is stored.
17347 @subsubheading @value{GDBN} Command
17349 The corresponding @value{GDBN} command is @samp{info address}.
17351 @subsubheading Example
17355 @subheading The @code{-symbol-info-file} Command
17356 @findex -symbol-info-file
17358 @subsubheading Synopsis
17364 Show the file for the symbol.
17366 @subsubheading @value{GDBN} Command
17368 There's no equivalent @value{GDBN} command. @code{gdbtk} has
17369 @samp{gdb_find_file}.
17371 @subsubheading Example
17375 @subheading The @code{-symbol-info-function} Command
17376 @findex -symbol-info-function
17378 @subsubheading Synopsis
17381 -symbol-info-function
17384 Show which function the symbol lives in.
17386 @subsubheading @value{GDBN} Command
17388 @samp{gdb_get_function} in @code{gdbtk}.
17390 @subsubheading Example
17394 @subheading The @code{-symbol-info-line} Command
17395 @findex -symbol-info-line
17397 @subsubheading Synopsis
17403 Show the core addresses of the code for a source line.
17405 @subsubheading @value{GDBN} Command
17407 The corresponding @value{GDBN} command is @samp{info line}.
17408 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
17410 @subsubheading Example
17414 @subheading The @code{-symbol-info-symbol} Command
17415 @findex -symbol-info-symbol
17417 @subsubheading Synopsis
17420 -symbol-info-symbol @var{addr}
17423 Describe what symbol is at location @var{addr}.
17425 @subsubheading @value{GDBN} Command
17427 The corresponding @value{GDBN} command is @samp{info symbol}.
17429 @subsubheading Example
17433 @subheading The @code{-symbol-list-functions} Command
17434 @findex -symbol-list-functions
17436 @subsubheading Synopsis
17439 -symbol-list-functions
17442 List the functions in the executable.
17444 @subsubheading @value{GDBN} Command
17446 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
17447 @samp{gdb_search} in @code{gdbtk}.
17449 @subsubheading Example
17453 @subheading The @code{-symbol-list-lines} Command
17454 @findex -symbol-list-lines
17456 @subsubheading Synopsis
17459 -symbol-list-lines @var{filename}
17462 Print the list of lines that contain code and their associated program
17463 addresses for the given source filename. The entries are sorted in
17464 ascending PC order.
17466 @subsubheading @value{GDBN} Command
17468 There is no corresponding @value{GDBN} command.
17470 @subsubheading Example
17473 -symbol-list-lines basics.c
17474 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
17479 @subheading The @code{-symbol-list-types} Command
17480 @findex -symbol-list-types
17482 @subsubheading Synopsis
17488 List all the type names.
17490 @subsubheading @value{GDBN} Command
17492 The corresponding commands are @samp{info types} in @value{GDBN},
17493 @samp{gdb_search} in @code{gdbtk}.
17495 @subsubheading Example
17499 @subheading The @code{-symbol-list-variables} Command
17500 @findex -symbol-list-variables
17502 @subsubheading Synopsis
17505 -symbol-list-variables
17508 List all the global and static variable names.
17510 @subsubheading @value{GDBN} Command
17512 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
17514 @subsubheading Example
17518 @subheading The @code{-symbol-locate} Command
17519 @findex -symbol-locate
17521 @subsubheading Synopsis
17527 @subsubheading @value{GDBN} Command
17529 @samp{gdb_loc} in @code{gdbtk}.
17531 @subsubheading Example
17535 @subheading The @code{-symbol-type} Command
17536 @findex -symbol-type
17538 @subsubheading Synopsis
17541 -symbol-type @var{variable}
17544 Show type of @var{variable}.
17546 @subsubheading @value{GDBN} Command
17548 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
17549 @samp{gdb_obj_variable}.
17551 @subsubheading Example
17555 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17556 @node GDB/MI Target Manipulation
17557 @section @sc{gdb/mi} Target Manipulation Commands
17560 @subheading The @code{-target-attach} Command
17561 @findex -target-attach
17563 @subsubheading Synopsis
17566 -target-attach @var{pid} | @var{file}
17569 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
17571 @subsubheading @value{GDBN} command
17573 The corresponding @value{GDBN} command is @samp{attach}.
17575 @subsubheading Example
17579 @subheading The @code{-target-compare-sections} Command
17580 @findex -target-compare-sections
17582 @subsubheading Synopsis
17585 -target-compare-sections [ @var{section} ]
17588 Compare data of section @var{section} on target to the exec file.
17589 Without the argument, all sections are compared.
17591 @subsubheading @value{GDBN} Command
17593 The @value{GDBN} equivalent is @samp{compare-sections}.
17595 @subsubheading Example
17599 @subheading The @code{-target-detach} Command
17600 @findex -target-detach
17602 @subsubheading Synopsis
17608 Disconnect from the remote target. There's no output.
17610 @subsubheading @value{GDBN} command
17612 The corresponding @value{GDBN} command is @samp{detach}.
17614 @subsubheading Example
17624 @subheading The @code{-target-disconnect} Command
17625 @findex -target-disconnect
17627 @subsubheading Synopsis
17633 Disconnect from the remote target. There's no output.
17635 @subsubheading @value{GDBN} command
17637 The corresponding @value{GDBN} command is @samp{disconnect}.
17639 @subsubheading Example
17649 @subheading The @code{-target-download} Command
17650 @findex -target-download
17652 @subsubheading Synopsis
17658 Loads the executable onto the remote target.
17659 It prints out an update message every half second, which includes the fields:
17663 The name of the section.
17665 The size of what has been sent so far for that section.
17667 The size of the section.
17669 The total size of what was sent so far (the current and the previous sections).
17671 The size of the overall executable to download.
17675 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
17676 @sc{gdb/mi} Output Syntax}).
17678 In addition, it prints the name and size of the sections, as they are
17679 downloaded. These messages include the following fields:
17683 The name of the section.
17685 The size of the section.
17687 The size of the overall executable to download.
17691 At the end, a summary is printed.
17693 @subsubheading @value{GDBN} Command
17695 The corresponding @value{GDBN} command is @samp{load}.
17697 @subsubheading Example
17699 Note: each status message appears on a single line. Here the messages
17700 have been broken down so that they can fit onto a page.
17705 +download,@{section=".text",section-size="6668",total-size="9880"@}
17706 +download,@{section=".text",section-sent="512",section-size="6668",
17707 total-sent="512",total-size="9880"@}
17708 +download,@{section=".text",section-sent="1024",section-size="6668",
17709 total-sent="1024",total-size="9880"@}
17710 +download,@{section=".text",section-sent="1536",section-size="6668",
17711 total-sent="1536",total-size="9880"@}
17712 +download,@{section=".text",section-sent="2048",section-size="6668",
17713 total-sent="2048",total-size="9880"@}
17714 +download,@{section=".text",section-sent="2560",section-size="6668",
17715 total-sent="2560",total-size="9880"@}
17716 +download,@{section=".text",section-sent="3072",section-size="6668",
17717 total-sent="3072",total-size="9880"@}
17718 +download,@{section=".text",section-sent="3584",section-size="6668",
17719 total-sent="3584",total-size="9880"@}
17720 +download,@{section=".text",section-sent="4096",section-size="6668",
17721 total-sent="4096",total-size="9880"@}
17722 +download,@{section=".text",section-sent="4608",section-size="6668",
17723 total-sent="4608",total-size="9880"@}
17724 +download,@{section=".text",section-sent="5120",section-size="6668",
17725 total-sent="5120",total-size="9880"@}
17726 +download,@{section=".text",section-sent="5632",section-size="6668",
17727 total-sent="5632",total-size="9880"@}
17728 +download,@{section=".text",section-sent="6144",section-size="6668",
17729 total-sent="6144",total-size="9880"@}
17730 +download,@{section=".text",section-sent="6656",section-size="6668",
17731 total-sent="6656",total-size="9880"@}
17732 +download,@{section=".init",section-size="28",total-size="9880"@}
17733 +download,@{section=".fini",section-size="28",total-size="9880"@}
17734 +download,@{section=".data",section-size="3156",total-size="9880"@}
17735 +download,@{section=".data",section-sent="512",section-size="3156",
17736 total-sent="7236",total-size="9880"@}
17737 +download,@{section=".data",section-sent="1024",section-size="3156",
17738 total-sent="7748",total-size="9880"@}
17739 +download,@{section=".data",section-sent="1536",section-size="3156",
17740 total-sent="8260",total-size="9880"@}
17741 +download,@{section=".data",section-sent="2048",section-size="3156",
17742 total-sent="8772",total-size="9880"@}
17743 +download,@{section=".data",section-sent="2560",section-size="3156",
17744 total-sent="9284",total-size="9880"@}
17745 +download,@{section=".data",section-sent="3072",section-size="3156",
17746 total-sent="9796",total-size="9880"@}
17747 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
17753 @subheading The @code{-target-exec-status} Command
17754 @findex -target-exec-status
17756 @subsubheading Synopsis
17759 -target-exec-status
17762 Provide information on the state of the target (whether it is running or
17763 not, for instance).
17765 @subsubheading @value{GDBN} Command
17767 There's no equivalent @value{GDBN} command.
17769 @subsubheading Example
17773 @subheading The @code{-target-list-available-targets} Command
17774 @findex -target-list-available-targets
17776 @subsubheading Synopsis
17779 -target-list-available-targets
17782 List the possible targets to connect to.
17784 @subsubheading @value{GDBN} Command
17786 The corresponding @value{GDBN} command is @samp{help target}.
17788 @subsubheading Example
17792 @subheading The @code{-target-list-current-targets} Command
17793 @findex -target-list-current-targets
17795 @subsubheading Synopsis
17798 -target-list-current-targets
17801 Describe the current target.
17803 @subsubheading @value{GDBN} Command
17805 The corresponding information is printed by @samp{info file} (among
17808 @subsubheading Example
17812 @subheading The @code{-target-list-parameters} Command
17813 @findex -target-list-parameters
17815 @subsubheading Synopsis
17818 -target-list-parameters
17823 @subsubheading @value{GDBN} Command
17827 @subsubheading Example
17831 @subheading The @code{-target-select} Command
17832 @findex -target-select
17834 @subsubheading Synopsis
17837 -target-select @var{type} @var{parameters @dots{}}
17840 Connect @value{GDBN} to the remote target. This command takes two args:
17844 The type of target, for instance @samp{async}, @samp{remote}, etc.
17845 @item @var{parameters}
17846 Device names, host names and the like. @xref{Target Commands, ,
17847 Commands for managing targets}, for more details.
17850 The output is a connection notification, followed by the address at
17851 which the target program is, in the following form:
17854 ^connected,addr="@var{address}",func="@var{function name}",
17855 args=[@var{arg list}]
17858 @subsubheading @value{GDBN} Command
17860 The corresponding @value{GDBN} command is @samp{target}.
17862 @subsubheading Example
17866 -target-select async /dev/ttya
17867 ^connected,addr="0xfe00a300",func="??",args=[]
17871 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17872 @node GDB/MI Thread Commands
17873 @section @sc{gdb/mi} Thread Commands
17876 @subheading The @code{-thread-info} Command
17877 @findex -thread-info
17879 @subsubheading Synopsis
17885 @subsubheading @value{GDBN} command
17889 @subsubheading Example
17893 @subheading The @code{-thread-list-all-threads} Command
17894 @findex -thread-list-all-threads
17896 @subsubheading Synopsis
17899 -thread-list-all-threads
17902 @subsubheading @value{GDBN} Command
17904 The equivalent @value{GDBN} command is @samp{info threads}.
17906 @subsubheading Example
17910 @subheading The @code{-thread-list-ids} Command
17911 @findex -thread-list-ids
17913 @subsubheading Synopsis
17919 Produces a list of the currently known @value{GDBN} thread ids. At the
17920 end of the list it also prints the total number of such threads.
17922 @subsubheading @value{GDBN} Command
17924 Part of @samp{info threads} supplies the same information.
17926 @subsubheading Example
17928 No threads present, besides the main process:
17933 ^done,thread-ids=@{@},number-of-threads="0"
17943 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
17944 number-of-threads="3"
17949 @subheading The @code{-thread-select} Command
17950 @findex -thread-select
17952 @subsubheading Synopsis
17955 -thread-select @var{threadnum}
17958 Make @var{threadnum} the current thread. It prints the number of the new
17959 current thread, and the topmost frame for that thread.
17961 @subsubheading @value{GDBN} Command
17963 The corresponding @value{GDBN} command is @samp{thread}.
17965 @subsubheading Example
17972 *stopped,reason="end-stepping-range",thread-id="2",line="187",
17973 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
17977 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
17978 number-of-threads="3"
17981 ^done,new-thread-id="3",
17982 frame=@{level="0",func="vprintf",
17983 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
17984 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
17988 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17989 @node GDB/MI Tracepoint Commands
17990 @section @sc{gdb/mi} Tracepoint Commands
17992 The tracepoint commands are not yet implemented.
17994 @c @subheading -trace-actions
17996 @c @subheading -trace-delete
17998 @c @subheading -trace-disable
18000 @c @subheading -trace-dump
18002 @c @subheading -trace-enable
18004 @c @subheading -trace-exists
18006 @c @subheading -trace-find
18008 @c @subheading -trace-frame-number
18010 @c @subheading -trace-info
18012 @c @subheading -trace-insert
18014 @c @subheading -trace-list
18016 @c @subheading -trace-pass-count
18018 @c @subheading -trace-save
18020 @c @subheading -trace-start
18022 @c @subheading -trace-stop
18025 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18026 @node GDB/MI Variable Objects
18027 @section @sc{gdb/mi} Variable Objects
18030 @subheading Motivation for Variable Objects in @sc{gdb/mi}
18032 For the implementation of a variable debugger window (locals, watched
18033 expressions, etc.), we are proposing the adaptation of the existing code
18034 used by @code{Insight}.
18036 The two main reasons for that are:
18040 It has been proven in practice (it is already on its second generation).
18043 It will shorten development time (needless to say how important it is
18047 The original interface was designed to be used by Tcl code, so it was
18048 slightly changed so it could be used through @sc{gdb/mi}. This section
18049 describes the @sc{gdb/mi} operations that will be available and gives some
18050 hints about their use.
18052 @emph{Note}: In addition to the set of operations described here, we
18053 expect the @sc{gui} implementation of a variable window to require, at
18054 least, the following operations:
18057 @item @code{-gdb-show} @code{output-radix}
18058 @item @code{-stack-list-arguments}
18059 @item @code{-stack-list-locals}
18060 @item @code{-stack-select-frame}
18063 @subheading Introduction to Variable Objects in @sc{gdb/mi}
18065 @cindex variable objects in @sc{gdb/mi}
18066 The basic idea behind variable objects is the creation of a named object
18067 to represent a variable, an expression, a memory location or even a CPU
18068 register. For each object created, a set of operations is available for
18069 examining or changing its properties.
18071 Furthermore, complex data types, such as C structures, are represented
18072 in a tree format. For instance, the @code{struct} type variable is the
18073 root and the children will represent the struct members. If a child
18074 is itself of a complex type, it will also have children of its own.
18075 Appropriate language differences are handled for C, C@t{++} and Java.
18077 When returning the actual values of the objects, this facility allows
18078 for the individual selection of the display format used in the result
18079 creation. It can be chosen among: binary, decimal, hexadecimal, octal
18080 and natural. Natural refers to a default format automatically
18081 chosen based on the variable type (like decimal for an @code{int}, hex
18082 for pointers, etc.).
18084 The following is the complete set of @sc{gdb/mi} operations defined to
18085 access this functionality:
18087 @multitable @columnfractions .4 .6
18088 @item @strong{Operation}
18089 @tab @strong{Description}
18091 @item @code{-var-create}
18092 @tab create a variable object
18093 @item @code{-var-delete}
18094 @tab delete the variable object and its children
18095 @item @code{-var-set-format}
18096 @tab set the display format of this variable
18097 @item @code{-var-show-format}
18098 @tab show the display format of this variable
18099 @item @code{-var-info-num-children}
18100 @tab tells how many children this object has
18101 @item @code{-var-list-children}
18102 @tab return a list of the object's children
18103 @item @code{-var-info-type}
18104 @tab show the type of this variable object
18105 @item @code{-var-info-expression}
18106 @tab print what this variable object represents
18107 @item @code{-var-show-attributes}
18108 @tab is this variable editable? does it exist here?
18109 @item @code{-var-evaluate-expression}
18110 @tab get the value of this variable
18111 @item @code{-var-assign}
18112 @tab set the value of this variable
18113 @item @code{-var-update}
18114 @tab update the variable and its children
18117 In the next subsection we describe each operation in detail and suggest
18118 how it can be used.
18120 @subheading Description And Use of Operations on Variable Objects
18122 @subheading The @code{-var-create} Command
18123 @findex -var-create
18125 @subsubheading Synopsis
18128 -var-create @{@var{name} | "-"@}
18129 @{@var{frame-addr} | "*"@} @var{expression}
18132 This operation creates a variable object, which allows the monitoring of
18133 a variable, the result of an expression, a memory cell or a CPU
18136 The @var{name} parameter is the string by which the object can be
18137 referenced. It must be unique. If @samp{-} is specified, the varobj
18138 system will generate a string ``varNNNNNN'' automatically. It will be
18139 unique provided that one does not specify @var{name} on that format.
18140 The command fails if a duplicate name is found.
18142 The frame under which the expression should be evaluated can be
18143 specified by @var{frame-addr}. A @samp{*} indicates that the current
18144 frame should be used.
18146 @var{expression} is any expression valid on the current language set (must not
18147 begin with a @samp{*}), or one of the following:
18151 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
18154 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
18157 @samp{$@var{regname}} --- a CPU register name
18160 @subsubheading Result
18162 This operation returns the name, number of children and the type of the
18163 object created. Type is returned as a string as the ones generated by
18164 the @value{GDBN} CLI:
18167 name="@var{name}",numchild="N",type="@var{type}"
18171 @subheading The @code{-var-delete} Command
18172 @findex -var-delete
18174 @subsubheading Synopsis
18177 -var-delete @var{name}
18180 Deletes a previously created variable object and all of its children.
18182 Returns an error if the object @var{name} is not found.
18185 @subheading The @code{-var-set-format} Command
18186 @findex -var-set-format
18188 @subsubheading Synopsis
18191 -var-set-format @var{name} @var{format-spec}
18194 Sets the output format for the value of the object @var{name} to be
18197 The syntax for the @var{format-spec} is as follows:
18200 @var{format-spec} @expansion{}
18201 @{binary | decimal | hexadecimal | octal | natural@}
18205 @subheading The @code{-var-show-format} Command
18206 @findex -var-show-format
18208 @subsubheading Synopsis
18211 -var-show-format @var{name}
18214 Returns the format used to display the value of the object @var{name}.
18217 @var{format} @expansion{}
18222 @subheading The @code{-var-info-num-children} Command
18223 @findex -var-info-num-children
18225 @subsubheading Synopsis
18228 -var-info-num-children @var{name}
18231 Returns the number of children of a variable object @var{name}:
18238 @subheading The @code{-var-list-children} Command
18239 @findex -var-list-children
18241 @subsubheading Synopsis
18244 -var-list-children [@var{print-values}] @var{name}
18247 Returns a list of the children of the specified variable object. With
18248 just the variable object name as an argument or with an optional
18249 preceding argument of 0 or @code{--no-values}, prints only the names of the
18250 variables. With an optional preceding argument of 1 or @code{--all-values},
18251 also prints their values.
18253 @subsubheading Example
18257 -var-list-children n
18258 numchild=@var{n},children=[@{name=@var{name},
18259 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
18261 -var-list-children --all-values n
18262 numchild=@var{n},children=[@{name=@var{name},
18263 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
18267 @subheading The @code{-var-info-type} Command
18268 @findex -var-info-type
18270 @subsubheading Synopsis
18273 -var-info-type @var{name}
18276 Returns the type of the specified variable @var{name}. The type is
18277 returned as a string in the same format as it is output by the
18281 type=@var{typename}
18285 @subheading The @code{-var-info-expression} Command
18286 @findex -var-info-expression
18288 @subsubheading Synopsis
18291 -var-info-expression @var{name}
18294 Returns what is represented by the variable object @var{name}:
18297 lang=@var{lang-spec},exp=@var{expression}
18301 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
18303 @subheading The @code{-var-show-attributes} Command
18304 @findex -var-show-attributes
18306 @subsubheading Synopsis
18309 -var-show-attributes @var{name}
18312 List attributes of the specified variable object @var{name}:
18315 status=@var{attr} [ ( ,@var{attr} )* ]
18319 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
18321 @subheading The @code{-var-evaluate-expression} Command
18322 @findex -var-evaluate-expression
18324 @subsubheading Synopsis
18327 -var-evaluate-expression @var{name}
18330 Evaluates the expression that is represented by the specified variable
18331 object and returns its value as a string in the current format specified
18338 Note that one must invoke @code{-var-list-children} for a variable
18339 before the value of a child variable can be evaluated.
18341 @subheading The @code{-var-assign} Command
18342 @findex -var-assign
18344 @subsubheading Synopsis
18347 -var-assign @var{name} @var{expression}
18350 Assigns the value of @var{expression} to the variable object specified
18351 by @var{name}. The object must be @samp{editable}. If the variable's
18352 value is altered by the assign, the variable will show up in any
18353 subsequent @code{-var-update} list.
18355 @subsubheading Example
18363 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
18367 @subheading The @code{-var-update} Command
18368 @findex -var-update
18370 @subsubheading Synopsis
18373 -var-update @{@var{name} | "*"@}
18376 Update the value of the variable object @var{name} by evaluating its
18377 expression after fetching all the new values from memory or registers.
18378 A @samp{*} causes all existing variable objects to be updated.
18382 @chapter @value{GDBN} Annotations
18384 This chapter describes annotations in @value{GDBN}. Annotations were
18385 designed to interface @value{GDBN} to graphical user interfaces or other
18386 similar programs which want to interact with @value{GDBN} at a
18387 relatively high level.
18389 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
18393 This is Edition @value{EDITION}, @value{DATE}.
18397 * Annotations Overview:: What annotations are; the general syntax.
18398 * Server Prefix:: Issuing a command without affecting user state.
18399 * Prompting:: Annotations marking @value{GDBN}'s need for input.
18400 * Errors:: Annotations for error messages.
18401 * Invalidation:: Some annotations describe things now invalid.
18402 * Annotations for Running::
18403 Whether the program is running, how it stopped, etc.
18404 * Source Annotations:: Annotations describing source code.
18407 @node Annotations Overview
18408 @section What is an Annotation?
18409 @cindex annotations
18411 Annotations start with a newline character, two @samp{control-z}
18412 characters, and the name of the annotation. If there is no additional
18413 information associated with this annotation, the name of the annotation
18414 is followed immediately by a newline. If there is additional
18415 information, the name of the annotation is followed by a space, the
18416 additional information, and a newline. The additional information
18417 cannot contain newline characters.
18419 Any output not beginning with a newline and two @samp{control-z}
18420 characters denotes literal output from @value{GDBN}. Currently there is
18421 no need for @value{GDBN} to output a newline followed by two
18422 @samp{control-z} characters, but if there was such a need, the
18423 annotations could be extended with an @samp{escape} annotation which
18424 means those three characters as output.
18426 The annotation @var{level}, which is specified using the
18427 @option{--annotate} command line option (@pxref{Mode Options}), controls
18428 how much information @value{GDBN} prints together with its prompt,
18429 values of expressions, source lines, and other types of output. Level 0
18430 is for no anntations, level 1 is for use when @value{GDBN} is run as a
18431 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
18432 for programs that control @value{GDBN}, and level 2 annotations have
18433 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
18434 Interface, annotate, GDB's Obsolete Annotations}). This chapter
18435 describes level 3 annotations.
18437 A simple example of starting up @value{GDBN} with annotations is:
18440 $ @kbd{gdb --annotate=3}
18442 Copyright 2003 Free Software Foundation, Inc.
18443 GDB is free software, covered by the GNU General Public License,
18444 and you are welcome to change it and/or distribute copies of it
18445 under certain conditions.
18446 Type "show copying" to see the conditions.
18447 There is absolutely no warranty for GDB. Type "show warranty"
18449 This GDB was configured as "i386-pc-linux-gnu"
18460 Here @samp{quit} is input to @value{GDBN}; the rest is output from
18461 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
18462 denotes a @samp{control-z} character) are annotations; the rest is
18463 output from @value{GDBN}.
18465 @node Server Prefix
18466 @section The Server Prefix
18467 @cindex server prefix for annotations
18469 To issue a command to @value{GDBN} without affecting certain aspects of
18470 the state which is seen by users, prefix it with @samp{server }. This
18471 means that this command will not affect the command history, nor will it
18472 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
18473 pressed on a line by itself.
18475 The server prefix does not affect the recording of values into the value
18476 history; to print a value without recording it into the value history,
18477 use the @code{output} command instead of the @code{print} command.
18480 @section Annotation for @value{GDBN} Input
18482 @cindex annotations for prompts
18483 When @value{GDBN} prompts for input, it annotates this fact so it is possible
18484 to know when to send output, when the output from a given command is
18487 Different kinds of input each have a different @dfn{input type}. Each
18488 input type has three annotations: a @code{pre-} annotation, which
18489 denotes the beginning of any prompt which is being output, a plain
18490 annotation, which denotes the end of the prompt, and then a @code{post-}
18491 annotation which denotes the end of any echo which may (or may not) be
18492 associated with the input. For example, the @code{prompt} input type
18493 features the following annotations:
18501 The input types are
18506 @findex post-prompt
18508 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
18510 @findex pre-commands
18512 @findex post-commands
18514 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
18515 command. The annotations are repeated for each command which is input.
18517 @findex pre-overload-choice
18518 @findex overload-choice
18519 @findex post-overload-choice
18520 @item overload-choice
18521 When @value{GDBN} wants the user to select between various overloaded functions.
18527 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
18529 @findex pre-prompt-for-continue
18530 @findex prompt-for-continue
18531 @findex post-prompt-for-continue
18532 @item prompt-for-continue
18533 When @value{GDBN} is asking the user to press return to continue. Note: Don't
18534 expect this to work well; instead use @code{set height 0} to disable
18535 prompting. This is because the counting of lines is buggy in the
18536 presence of annotations.
18541 @cindex annotations for errors, warnings and interrupts
18548 This annotation occurs right before @value{GDBN} responds to an interrupt.
18555 This annotation occurs right before @value{GDBN} responds to an error.
18557 Quit and error annotations indicate that any annotations which @value{GDBN} was
18558 in the middle of may end abruptly. For example, if a
18559 @code{value-history-begin} annotation is followed by a @code{error}, one
18560 cannot expect to receive the matching @code{value-history-end}. One
18561 cannot expect not to receive it either, however; an error annotation
18562 does not necessarily mean that @value{GDBN} is immediately returning all the way
18565 @findex error-begin
18566 A quit or error annotation may be preceded by
18572 Any output between that and the quit or error annotation is the error
18575 Warning messages are not yet annotated.
18576 @c If we want to change that, need to fix warning(), type_error(),
18577 @c range_error(), and possibly other places.
18580 @section Invalidation Notices
18582 @cindex annotations for invalidation messages
18583 The following annotations say that certain pieces of state may have
18587 @findex frames-invalid
18588 @item ^Z^Zframes-invalid
18590 The frames (for example, output from the @code{backtrace} command) may
18593 @findex breakpoints-invalid
18594 @item ^Z^Zbreakpoints-invalid
18596 The breakpoints may have changed. For example, the user just added or
18597 deleted a breakpoint.
18600 @node Annotations for Running
18601 @section Running the Program
18602 @cindex annotations for running programs
18606 When the program starts executing due to a @value{GDBN} command such as
18607 @code{step} or @code{continue},
18613 is output. When the program stops,
18619 is output. Before the @code{stopped} annotation, a variety of
18620 annotations describe how the program stopped.
18624 @item ^Z^Zexited @var{exit-status}
18625 The program exited, and @var{exit-status} is the exit status (zero for
18626 successful exit, otherwise nonzero).
18629 @findex signal-name
18630 @findex signal-name-end
18631 @findex signal-string
18632 @findex signal-string-end
18633 @item ^Z^Zsignalled
18634 The program exited with a signal. After the @code{^Z^Zsignalled}, the
18635 annotation continues:
18641 ^Z^Zsignal-name-end
18645 ^Z^Zsignal-string-end
18650 where @var{name} is the name of the signal, such as @code{SIGILL} or
18651 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
18652 as @code{Illegal Instruction} or @code{Segmentation fault}.
18653 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
18654 user's benefit and have no particular format.
18658 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
18659 just saying that the program received the signal, not that it was
18660 terminated with it.
18663 @item ^Z^Zbreakpoint @var{number}
18664 The program hit breakpoint number @var{number}.
18667 @item ^Z^Zwatchpoint @var{number}
18668 The program hit watchpoint number @var{number}.
18671 @node Source Annotations
18672 @section Displaying Source
18673 @cindex annotations for source display
18676 The following annotation is used instead of displaying source code:
18679 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
18682 where @var{filename} is an absolute file name indicating which source
18683 file, @var{line} is the line number within that file (where 1 is the
18684 first line in the file), @var{character} is the character position
18685 within the file (where 0 is the first character in the file) (for most
18686 debug formats this will necessarily point to the beginning of a line),
18687 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
18688 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
18689 @var{addr} is the address in the target program associated with the
18690 source which is being displayed. @var{addr} is in the form @samp{0x}
18691 followed by one or more lowercase hex digits (note that this does not
18692 depend on the language).
18695 @chapter Reporting Bugs in @value{GDBN}
18696 @cindex bugs in @value{GDBN}
18697 @cindex reporting bugs in @value{GDBN}
18699 Your bug reports play an essential role in making @value{GDBN} reliable.
18701 Reporting a bug may help you by bringing a solution to your problem, or it
18702 may not. But in any case the principal function of a bug report is to help
18703 the entire community by making the next version of @value{GDBN} work better. Bug
18704 reports are your contribution to the maintenance of @value{GDBN}.
18706 In order for a bug report to serve its purpose, you must include the
18707 information that enables us to fix the bug.
18710 * Bug Criteria:: Have you found a bug?
18711 * Bug Reporting:: How to report bugs
18715 @section Have you found a bug?
18716 @cindex bug criteria
18718 If you are not sure whether you have found a bug, here are some guidelines:
18721 @cindex fatal signal
18722 @cindex debugger crash
18723 @cindex crash of debugger
18725 If the debugger gets a fatal signal, for any input whatever, that is a
18726 @value{GDBN} bug. Reliable debuggers never crash.
18728 @cindex error on valid input
18730 If @value{GDBN} produces an error message for valid input, that is a
18731 bug. (Note that if you're cross debugging, the problem may also be
18732 somewhere in the connection to the target.)
18734 @cindex invalid input
18736 If @value{GDBN} does not produce an error message for invalid input,
18737 that is a bug. However, you should note that your idea of
18738 ``invalid input'' might be our idea of ``an extension'' or ``support
18739 for traditional practice''.
18742 If you are an experienced user of debugging tools, your suggestions
18743 for improvement of @value{GDBN} are welcome in any case.
18746 @node Bug Reporting
18747 @section How to report bugs
18748 @cindex bug reports
18749 @cindex @value{GDBN} bugs, reporting
18751 A number of companies and individuals offer support for @sc{gnu} products.
18752 If you obtained @value{GDBN} from a support organization, we recommend you
18753 contact that organization first.
18755 You can find contact information for many support companies and
18756 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
18758 @c should add a web page ref...
18760 In any event, we also recommend that you submit bug reports for
18761 @value{GDBN}. The prefered method is to submit them directly using
18762 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
18763 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
18766 @strong{Do not send bug reports to @samp{info-gdb}, or to
18767 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
18768 not want to receive bug reports. Those that do have arranged to receive
18771 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
18772 serves as a repeater. The mailing list and the newsgroup carry exactly
18773 the same messages. Often people think of posting bug reports to the
18774 newsgroup instead of mailing them. This appears to work, but it has one
18775 problem which can be crucial: a newsgroup posting often lacks a mail
18776 path back to the sender. Thus, if we need to ask for more information,
18777 we may be unable to reach you. For this reason, it is better to send
18778 bug reports to the mailing list.
18780 The fundamental principle of reporting bugs usefully is this:
18781 @strong{report all the facts}. If you are not sure whether to state a
18782 fact or leave it out, state it!
18784 Often people omit facts because they think they know what causes the
18785 problem and assume that some details do not matter. Thus, you might
18786 assume that the name of the variable you use in an example does not matter.
18787 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
18788 stray memory reference which happens to fetch from the location where that
18789 name is stored in memory; perhaps, if the name were different, the contents
18790 of that location would fool the debugger into doing the right thing despite
18791 the bug. Play it safe and give a specific, complete example. That is the
18792 easiest thing for you to do, and the most helpful.
18794 Keep in mind that the purpose of a bug report is to enable us to fix the
18795 bug. It may be that the bug has been reported previously, but neither
18796 you nor we can know that unless your bug report is complete and
18799 Sometimes people give a few sketchy facts and ask, ``Does this ring a
18800 bell?'' Those bug reports are useless, and we urge everyone to
18801 @emph{refuse to respond to them} except to chide the sender to report
18804 To enable us to fix the bug, you should include all these things:
18808 The version of @value{GDBN}. @value{GDBN} announces it if you start
18809 with no arguments; you can also print it at any time using @code{show
18812 Without this, we will not know whether there is any point in looking for
18813 the bug in the current version of @value{GDBN}.
18816 The type of machine you are using, and the operating system name and
18820 What compiler (and its version) was used to compile @value{GDBN}---e.g.
18821 ``@value{GCC}--2.8.1''.
18824 What compiler (and its version) was used to compile the program you are
18825 debugging---e.g. ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
18826 C Compiler''. For GCC, you can say @code{gcc --version} to get this
18827 information; for other compilers, see the documentation for those
18831 The command arguments you gave the compiler to compile your example and
18832 observe the bug. For example, did you use @samp{-O}? To guarantee
18833 you will not omit something important, list them all. A copy of the
18834 Makefile (or the output from make) is sufficient.
18836 If we were to try to guess the arguments, we would probably guess wrong
18837 and then we might not encounter the bug.
18840 A complete input script, and all necessary source files, that will
18844 A description of what behavior you observe that you believe is
18845 incorrect. For example, ``It gets a fatal signal.''
18847 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
18848 will certainly notice it. But if the bug is incorrect output, we might
18849 not notice unless it is glaringly wrong. You might as well not give us
18850 a chance to make a mistake.
18852 Even if the problem you experience is a fatal signal, you should still
18853 say so explicitly. Suppose something strange is going on, such as, your
18854 copy of @value{GDBN} is out of synch, or you have encountered a bug in
18855 the C library on your system. (This has happened!) Your copy might
18856 crash and ours would not. If you told us to expect a crash, then when
18857 ours fails to crash, we would know that the bug was not happening for
18858 us. If you had not told us to expect a crash, then we would not be able
18859 to draw any conclusion from our observations.
18862 If you wish to suggest changes to the @value{GDBN} source, send us context
18863 diffs. If you even discuss something in the @value{GDBN} source, refer to
18864 it by context, not by line number.
18866 The line numbers in our development sources will not match those in your
18867 sources. Your line numbers would convey no useful information to us.
18871 Here are some things that are not necessary:
18875 A description of the envelope of the bug.
18877 Often people who encounter a bug spend a lot of time investigating
18878 which changes to the input file will make the bug go away and which
18879 changes will not affect it.
18881 This is often time consuming and not very useful, because the way we
18882 will find the bug is by running a single example under the debugger
18883 with breakpoints, not by pure deduction from a series of examples.
18884 We recommend that you save your time for something else.
18886 Of course, if you can find a simpler example to report @emph{instead}
18887 of the original one, that is a convenience for us. Errors in the
18888 output will be easier to spot, running under the debugger will take
18889 less time, and so on.
18891 However, simplification is not vital; if you do not want to do this,
18892 report the bug anyway and send us the entire test case you used.
18895 A patch for the bug.
18897 A patch for the bug does help us if it is a good one. But do not omit
18898 the necessary information, such as the test case, on the assumption that
18899 a patch is all we need. We might see problems with your patch and decide
18900 to fix the problem another way, or we might not understand it at all.
18902 Sometimes with a program as complicated as @value{GDBN} it is very hard to
18903 construct an example that will make the program follow a certain path
18904 through the code. If you do not send us the example, we will not be able
18905 to construct one, so we will not be able to verify that the bug is fixed.
18907 And if we cannot understand what bug you are trying to fix, or why your
18908 patch should be an improvement, we will not install it. A test case will
18909 help us to understand.
18912 A guess about what the bug is or what it depends on.
18914 Such guesses are usually wrong. Even we cannot guess right about such
18915 things without first using the debugger to find the facts.
18918 @c The readline documentation is distributed with the readline code
18919 @c and consists of the two following files:
18921 @c inc-hist.texinfo
18922 @c Use -I with makeinfo to point to the appropriate directory,
18923 @c environment var TEXINPUTS with TeX.
18924 @include rluser.texinfo
18925 @include inc-hist.texinfo
18928 @node Formatting Documentation
18929 @appendix Formatting Documentation
18931 @cindex @value{GDBN} reference card
18932 @cindex reference card
18933 The @value{GDBN} 4 release includes an already-formatted reference card, ready
18934 for printing with PostScript or Ghostscript, in the @file{gdb}
18935 subdirectory of the main source directory@footnote{In
18936 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
18937 release.}. If you can use PostScript or Ghostscript with your printer,
18938 you can print the reference card immediately with @file{refcard.ps}.
18940 The release also includes the source for the reference card. You
18941 can format it, using @TeX{}, by typing:
18947 The @value{GDBN} reference card is designed to print in @dfn{landscape}
18948 mode on US ``letter'' size paper;
18949 that is, on a sheet 11 inches wide by 8.5 inches
18950 high. You will need to specify this form of printing as an option to
18951 your @sc{dvi} output program.
18953 @cindex documentation
18955 All the documentation for @value{GDBN} comes as part of the machine-readable
18956 distribution. The documentation is written in Texinfo format, which is
18957 a documentation system that uses a single source file to produce both
18958 on-line information and a printed manual. You can use one of the Info
18959 formatting commands to create the on-line version of the documentation
18960 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
18962 @value{GDBN} includes an already formatted copy of the on-line Info
18963 version of this manual in the @file{gdb} subdirectory. The main Info
18964 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
18965 subordinate files matching @samp{gdb.info*} in the same directory. If
18966 necessary, you can print out these files, or read them with any editor;
18967 but they are easier to read using the @code{info} subsystem in @sc{gnu}
18968 Emacs or the standalone @code{info} program, available as part of the
18969 @sc{gnu} Texinfo distribution.
18971 If you want to format these Info files yourself, you need one of the
18972 Info formatting programs, such as @code{texinfo-format-buffer} or
18975 If you have @code{makeinfo} installed, and are in the top level
18976 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
18977 version @value{GDBVN}), you can make the Info file by typing:
18984 If you want to typeset and print copies of this manual, you need @TeX{},
18985 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
18986 Texinfo definitions file.
18988 @TeX{} is a typesetting program; it does not print files directly, but
18989 produces output files called @sc{dvi} files. To print a typeset
18990 document, you need a program to print @sc{dvi} files. If your system
18991 has @TeX{} installed, chances are it has such a program. The precise
18992 command to use depends on your system; @kbd{lpr -d} is common; another
18993 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
18994 require a file name without any extension or a @samp{.dvi} extension.
18996 @TeX{} also requires a macro definitions file called
18997 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
18998 written in Texinfo format. On its own, @TeX{} cannot either read or
18999 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
19000 and is located in the @file{gdb-@var{version-number}/texinfo}
19003 If you have @TeX{} and a @sc{dvi} printer program installed, you can
19004 typeset and print this manual. First switch to the the @file{gdb}
19005 subdirectory of the main source directory (for example, to
19006 @file{gdb-@value{GDBVN}/gdb}) and type:
19012 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
19014 @node Installing GDB
19015 @appendix Installing @value{GDBN}
19016 @cindex configuring @value{GDBN}
19017 @cindex installation
19018 @cindex configuring @value{GDBN}, and source tree subdirectories
19020 @value{GDBN} comes with a @code{configure} script that automates the process
19021 of preparing @value{GDBN} for installation; you can then use @code{make} to
19022 build the @code{gdb} program.
19024 @c irrelevant in info file; it's as current as the code it lives with.
19025 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
19026 look at the @file{README} file in the sources; we may have improved the
19027 installation procedures since publishing this manual.}
19030 The @value{GDBN} distribution includes all the source code you need for
19031 @value{GDBN} in a single directory, whose name is usually composed by
19032 appending the version number to @samp{gdb}.
19034 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
19035 @file{gdb-@value{GDBVN}} directory. That directory contains:
19038 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
19039 script for configuring @value{GDBN} and all its supporting libraries
19041 @item gdb-@value{GDBVN}/gdb
19042 the source specific to @value{GDBN} itself
19044 @item gdb-@value{GDBVN}/bfd
19045 source for the Binary File Descriptor library
19047 @item gdb-@value{GDBVN}/include
19048 @sc{gnu} include files
19050 @item gdb-@value{GDBVN}/libiberty
19051 source for the @samp{-liberty} free software library
19053 @item gdb-@value{GDBVN}/opcodes
19054 source for the library of opcode tables and disassemblers
19056 @item gdb-@value{GDBVN}/readline
19057 source for the @sc{gnu} command-line interface
19059 @item gdb-@value{GDBVN}/glob
19060 source for the @sc{gnu} filename pattern-matching subroutine
19062 @item gdb-@value{GDBVN}/mmalloc
19063 source for the @sc{gnu} memory-mapped malloc package
19066 The simplest way to configure and build @value{GDBN} is to run @code{configure}
19067 from the @file{gdb-@var{version-number}} source directory, which in
19068 this example is the @file{gdb-@value{GDBVN}} directory.
19070 First switch to the @file{gdb-@var{version-number}} source directory
19071 if you are not already in it; then run @code{configure}. Pass the
19072 identifier for the platform on which @value{GDBN} will run as an
19078 cd gdb-@value{GDBVN}
19079 ./configure @var{host}
19084 where @var{host} is an identifier such as @samp{sun4} or
19085 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
19086 (You can often leave off @var{host}; @code{configure} tries to guess the
19087 correct value by examining your system.)
19089 Running @samp{configure @var{host}} and then running @code{make} builds the
19090 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
19091 libraries, then @code{gdb} itself. The configured source files, and the
19092 binaries, are left in the corresponding source directories.
19095 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
19096 system does not recognize this automatically when you run a different
19097 shell, you may need to run @code{sh} on it explicitly:
19100 sh configure @var{host}
19103 If you run @code{configure} from a directory that contains source
19104 directories for multiple libraries or programs, such as the
19105 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
19106 creates configuration files for every directory level underneath (unless
19107 you tell it not to, with the @samp{--norecursion} option).
19109 You should run the @code{configure} script from the top directory in the
19110 source tree, the @file{gdb-@var{version-number}} directory. If you run
19111 @code{configure} from one of the subdirectories, you will configure only
19112 that subdirectory. That is usually not what you want. In particular,
19113 if you run the first @code{configure} from the @file{gdb} subdirectory
19114 of the @file{gdb-@var{version-number}} directory, you will omit the
19115 configuration of @file{bfd}, @file{readline}, and other sibling
19116 directories of the @file{gdb} subdirectory. This leads to build errors
19117 about missing include files such as @file{bfd/bfd.h}.
19119 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
19120 However, you should make sure that the shell on your path (named by
19121 the @samp{SHELL} environment variable) is publicly readable. Remember
19122 that @value{GDBN} uses the shell to start your program---some systems refuse to
19123 let @value{GDBN} debug child processes whose programs are not readable.
19126 * Separate Objdir:: Compiling @value{GDBN} in another directory
19127 * Config Names:: Specifying names for hosts and targets
19128 * Configure Options:: Summary of options for configure
19131 @node Separate Objdir
19132 @section Compiling @value{GDBN} in another directory
19134 If you want to run @value{GDBN} versions for several host or target machines,
19135 you need a different @code{gdb} compiled for each combination of
19136 host and target. @code{configure} is designed to make this easy by
19137 allowing you to generate each configuration in a separate subdirectory,
19138 rather than in the source directory. If your @code{make} program
19139 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
19140 @code{make} in each of these directories builds the @code{gdb}
19141 program specified there.
19143 To build @code{gdb} in a separate directory, run @code{configure}
19144 with the @samp{--srcdir} option to specify where to find the source.
19145 (You also need to specify a path to find @code{configure}
19146 itself from your working directory. If the path to @code{configure}
19147 would be the same as the argument to @samp{--srcdir}, you can leave out
19148 the @samp{--srcdir} option; it is assumed.)
19150 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
19151 separate directory for a Sun 4 like this:
19155 cd gdb-@value{GDBVN}
19158 ../gdb-@value{GDBVN}/configure sun4
19163 When @code{configure} builds a configuration using a remote source
19164 directory, it creates a tree for the binaries with the same structure
19165 (and using the same names) as the tree under the source directory. In
19166 the example, you'd find the Sun 4 library @file{libiberty.a} in the
19167 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
19168 @file{gdb-sun4/gdb}.
19170 Make sure that your path to the @file{configure} script has just one
19171 instance of @file{gdb} in it. If your path to @file{configure} looks
19172 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
19173 one subdirectory of @value{GDBN}, not the whole package. This leads to
19174 build errors about missing include files such as @file{bfd/bfd.h}.
19176 One popular reason to build several @value{GDBN} configurations in separate
19177 directories is to configure @value{GDBN} for cross-compiling (where
19178 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
19179 programs that run on another machine---the @dfn{target}).
19180 You specify a cross-debugging target by
19181 giving the @samp{--target=@var{target}} option to @code{configure}.
19183 When you run @code{make} to build a program or library, you must run
19184 it in a configured directory---whatever directory you were in when you
19185 called @code{configure} (or one of its subdirectories).
19187 The @code{Makefile} that @code{configure} generates in each source
19188 directory also runs recursively. If you type @code{make} in a source
19189 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
19190 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
19191 will build all the required libraries, and then build GDB.
19193 When you have multiple hosts or targets configured in separate
19194 directories, you can run @code{make} on them in parallel (for example,
19195 if they are NFS-mounted on each of the hosts); they will not interfere
19199 @section Specifying names for hosts and targets
19201 The specifications used for hosts and targets in the @code{configure}
19202 script are based on a three-part naming scheme, but some short predefined
19203 aliases are also supported. The full naming scheme encodes three pieces
19204 of information in the following pattern:
19207 @var{architecture}-@var{vendor}-@var{os}
19210 For example, you can use the alias @code{sun4} as a @var{host} argument,
19211 or as the value for @var{target} in a @code{--target=@var{target}}
19212 option. The equivalent full name is @samp{sparc-sun-sunos4}.
19214 The @code{configure} script accompanying @value{GDBN} does not provide
19215 any query facility to list all supported host and target names or
19216 aliases. @code{configure} calls the Bourne shell script
19217 @code{config.sub} to map abbreviations to full names; you can read the
19218 script, if you wish, or you can use it to test your guesses on
19219 abbreviations---for example:
19222 % sh config.sub i386-linux
19224 % sh config.sub alpha-linux
19225 alpha-unknown-linux-gnu
19226 % sh config.sub hp9k700
19228 % sh config.sub sun4
19229 sparc-sun-sunos4.1.1
19230 % sh config.sub sun3
19231 m68k-sun-sunos4.1.1
19232 % sh config.sub i986v
19233 Invalid configuration `i986v': machine `i986v' not recognized
19237 @code{config.sub} is also distributed in the @value{GDBN} source
19238 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
19240 @node Configure Options
19241 @section @code{configure} options
19243 Here is a summary of the @code{configure} options and arguments that
19244 are most often useful for building @value{GDBN}. @code{configure} also has
19245 several other options not listed here. @inforef{What Configure
19246 Does,,configure.info}, for a full explanation of @code{configure}.
19249 configure @r{[}--help@r{]}
19250 @r{[}--prefix=@var{dir}@r{]}
19251 @r{[}--exec-prefix=@var{dir}@r{]}
19252 @r{[}--srcdir=@var{dirname}@r{]}
19253 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
19254 @r{[}--target=@var{target}@r{]}
19259 You may introduce options with a single @samp{-} rather than
19260 @samp{--} if you prefer; but you may abbreviate option names if you use
19265 Display a quick summary of how to invoke @code{configure}.
19267 @item --prefix=@var{dir}
19268 Configure the source to install programs and files under directory
19271 @item --exec-prefix=@var{dir}
19272 Configure the source to install programs under directory
19275 @c avoid splitting the warning from the explanation:
19277 @item --srcdir=@var{dirname}
19278 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
19279 @code{make} that implements the @code{VPATH} feature.}@*
19280 Use this option to make configurations in directories separate from the
19281 @value{GDBN} source directories. Among other things, you can use this to
19282 build (or maintain) several configurations simultaneously, in separate
19283 directories. @code{configure} writes configuration specific files in
19284 the current directory, but arranges for them to use the source in the
19285 directory @var{dirname}. @code{configure} creates directories under
19286 the working directory in parallel to the source directories below
19289 @item --norecursion
19290 Configure only the directory level where @code{configure} is executed; do not
19291 propagate configuration to subdirectories.
19293 @item --target=@var{target}
19294 Configure @value{GDBN} for cross-debugging programs running on the specified
19295 @var{target}. Without this option, @value{GDBN} is configured to debug
19296 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
19298 There is no convenient way to generate a list of all available targets.
19300 @item @var{host} @dots{}
19301 Configure @value{GDBN} to run on the specified @var{host}.
19303 There is no convenient way to generate a list of all available hosts.
19306 There are many other options available as well, but they are generally
19307 needed for special purposes only.
19309 @node Maintenance Commands
19310 @appendix Maintenance Commands
19311 @cindex maintenance commands
19312 @cindex internal commands
19314 In addition to commands intended for @value{GDBN} users, @value{GDBN}
19315 includes a number of commands intended for @value{GDBN} developers.
19316 These commands are provided here for reference.
19319 @kindex maint info breakpoints
19320 @item @anchor{maint info breakpoints}maint info breakpoints
19321 Using the same format as @samp{info breakpoints}, display both the
19322 breakpoints you've set explicitly, and those @value{GDBN} is using for
19323 internal purposes. Internal breakpoints are shown with negative
19324 breakpoint numbers. The type column identifies what kind of breakpoint
19329 Normal, explicitly set breakpoint.
19332 Normal, explicitly set watchpoint.
19335 Internal breakpoint, used to handle correctly stepping through
19336 @code{longjmp} calls.
19338 @item longjmp resume
19339 Internal breakpoint at the target of a @code{longjmp}.
19342 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
19345 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
19348 Shared library events.
19352 @kindex maint internal-error
19353 @kindex maint internal-warning
19354 @item maint internal-error
19355 @itemx maint internal-warning
19356 Cause @value{GDBN} to call the internal function @code{internal_error}
19357 or @code{internal_warning} and hence behave as though an internal error
19358 or internal warning has been detected. In addition to reporting the
19359 internal problem, these functions give the user the opportunity to
19360 either quit @value{GDBN} or create a core file of the current
19361 @value{GDBN} session.
19364 (gdb) @kbd{maint internal-error testing, 1, 2}
19365 @dots{}/maint.c:121: internal-error: testing, 1, 2
19366 A problem internal to GDB has been detected. Further
19367 debugging may prove unreliable.
19368 Quit this debugging session? (y or n) @kbd{n}
19369 Create a core file? (y or n) @kbd{n}
19373 Takes an optional parameter that is used as the text of the error or
19376 @kindex maint print dummy-frames
19377 @item maint print dummy-frames
19379 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
19384 (gdb) @kbd{print add(2,3)}
19385 Breakpoint 2, add (a=2, b=3) at @dots{}
19387 The program being debugged stopped while in a function called from GDB.
19389 (gdb) @kbd{maint print dummy-frames}
19390 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
19391 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
19392 call_lo=0x01014000 call_hi=0x01014001
19396 Takes an optional file parameter.
19398 @kindex maint print registers
19399 @kindex maint print raw-registers
19400 @kindex maint print cooked-registers
19401 @kindex maint print register-groups
19402 @item maint print registers
19403 @itemx maint print raw-registers
19404 @itemx maint print cooked-registers
19405 @itemx maint print register-groups
19406 Print @value{GDBN}'s internal register data structures.
19408 The command @code{maint print raw-registers} includes the contents of
19409 the raw register cache; the command @code{maint print cooked-registers}
19410 includes the (cooked) value of all registers; and the command
19411 @code{maint print register-groups} includes the groups that each
19412 register is a member of. @xref{Registers,, Registers, gdbint,
19413 @value{GDBN} Internals}.
19415 Takes an optional file parameter.
19417 @kindex maint print reggroups
19418 @item maint print reggroups
19419 Print @value{GDBN}'s internal register group data structures.
19421 Takes an optional file parameter.
19424 (gdb) @kbd{maint print reggroups}
19435 @kindex maint set profile
19436 @kindex maint show profile
19437 @cindex profiling GDB
19438 @item maint set profile
19439 @itemx maint show profile
19440 Control profiling of @value{GDBN}.
19442 Profiling will be disabled until you use the @samp{maint set profile}
19443 command to enable it. When you enable profiling, the system will begin
19444 collecting timing and execution count data; when you disable profiling or
19445 exit @value{GDBN}, the results will be written to a log file. Remember that
19446 if you use profiling, @value{GDBN} will overwrite the profiling log file
19447 (often called @file{gmon.out}). If you have a record of important profiling
19448 data in a @file{gmon.out} file, be sure to move it to a safe location.
19450 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
19451 compiled with the @samp{-pg} compiler option.
19456 @node Remote Protocol
19457 @appendix @value{GDBN} Remote Serial Protocol
19462 * Stop Reply Packets::
19463 * General Query Packets::
19464 * Register Packet Format::
19466 * File-I/O remote protocol extension::
19472 There may be occasions when you need to know something about the
19473 protocol---for example, if there is only one serial port to your target
19474 machine, you might want your program to do something special if it
19475 recognizes a packet meant for @value{GDBN}.
19477 In the examples below, @samp{->} and @samp{<-} are used to indicate
19478 transmitted and received data respectfully.
19480 @cindex protocol, @value{GDBN} remote serial
19481 @cindex serial protocol, @value{GDBN} remote
19482 @cindex remote serial protocol
19483 All @value{GDBN} commands and responses (other than acknowledgments) are
19484 sent as a @var{packet}. A @var{packet} is introduced with the character
19485 @samp{$}, the actual @var{packet-data}, and the terminating character
19486 @samp{#} followed by a two-digit @var{checksum}:
19489 @code{$}@var{packet-data}@code{#}@var{checksum}
19493 @cindex checksum, for @value{GDBN} remote
19495 The two-digit @var{checksum} is computed as the modulo 256 sum of all
19496 characters between the leading @samp{$} and the trailing @samp{#} (an
19497 eight bit unsigned checksum).
19499 Implementors should note that prior to @value{GDBN} 5.0 the protocol
19500 specification also included an optional two-digit @var{sequence-id}:
19503 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
19506 @cindex sequence-id, for @value{GDBN} remote
19508 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
19509 has never output @var{sequence-id}s. Stubs that handle packets added
19510 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
19512 @cindex acknowledgment, for @value{GDBN} remote
19513 When either the host or the target machine receives a packet, the first
19514 response expected is an acknowledgment: either @samp{+} (to indicate
19515 the package was received correctly) or @samp{-} (to request
19519 -> @code{$}@var{packet-data}@code{#}@var{checksum}
19524 The host (@value{GDBN}) sends @var{command}s, and the target (the
19525 debugging stub incorporated in your program) sends a @var{response}. In
19526 the case of step and continue @var{command}s, the response is only sent
19527 when the operation has completed (the target has again stopped).
19529 @var{packet-data} consists of a sequence of characters with the
19530 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
19533 Fields within the packet should be separated using @samp{,} @samp{;} or
19534 @cindex remote protocol, field separator
19535 @samp{:}. Except where otherwise noted all numbers are represented in
19536 @sc{hex} with leading zeros suppressed.
19538 Implementors should note that prior to @value{GDBN} 5.0, the character
19539 @samp{:} could not appear as the third character in a packet (as it
19540 would potentially conflict with the @var{sequence-id}).
19542 Response @var{data} can be run-length encoded to save space. A @samp{*}
19543 means that the next character is an @sc{ascii} encoding giving a repeat count
19544 which stands for that many repetitions of the character preceding the
19545 @samp{*}. The encoding is @code{n+29}, yielding a printable character
19546 where @code{n >=3} (which is where rle starts to win). The printable
19547 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
19548 value greater than 126 should not be used.
19555 means the same as "0000".
19557 The error response returned for some packets includes a two character
19558 error number. That number is not well defined.
19560 For any @var{command} not supported by the stub, an empty response
19561 (@samp{$#00}) should be returned. That way it is possible to extend the
19562 protocol. A newer @value{GDBN} can tell if a packet is supported based
19565 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
19566 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
19572 The following table provides a complete list of all currently defined
19573 @var{command}s and their corresponding response @var{data}.
19577 @item @code{!} --- extended mode
19578 @cindex @code{!} packet
19580 Enable extended mode. In extended mode, the remote server is made
19581 persistent. The @samp{R} packet is used to restart the program being
19587 The remote target both supports and has enabled extended mode.
19590 @item @code{?} --- last signal
19591 @cindex @code{?} packet
19593 Indicate the reason the target halted. The reply is the same as for
19597 @xref{Stop Reply Packets}, for the reply specifications.
19599 @item @code{a} --- reserved
19601 Reserved for future use.
19603 @item @code{A}@var{arglen}@code{,}@var{argnum}@code{,}@var{arg}@code{,@dots{}} --- set program arguments @strong{(reserved)}
19604 @cindex @code{A} packet
19606 Initialized @samp{argv[]} array passed into program. @var{arglen}
19607 specifies the number of bytes in the hex encoded byte stream @var{arg}.
19608 See @code{gdbserver} for more details.
19616 @item @code{b}@var{baud} --- set baud @strong{(deprecated)}
19617 @cindex @code{b} packet
19619 Change the serial line speed to @var{baud}.
19621 JTC: @emph{When does the transport layer state change? When it's
19622 received, or after the ACK is transmitted. In either case, there are
19623 problems if the command or the acknowledgment packet is dropped.}
19625 Stan: @emph{If people really wanted to add something like this, and get
19626 it working for the first time, they ought to modify ser-unix.c to send
19627 some kind of out-of-band message to a specially-setup stub and have the
19628 switch happen "in between" packets, so that from remote protocol's point
19629 of view, nothing actually happened.}
19631 @item @code{B}@var{addr},@var{mode} --- set breakpoint @strong{(deprecated)}
19632 @cindex @code{B} packet
19634 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
19635 breakpoint at @var{addr}.
19637 This packet has been replaced by the @samp{Z} and @samp{z} packets
19638 (@pxref{insert breakpoint or watchpoint packet}).
19640 @item @code{c}@var{addr} --- continue
19641 @cindex @code{c} packet
19643 @var{addr} is address to resume. If @var{addr} is omitted, resume at
19647 @xref{Stop Reply Packets}, for the reply specifications.
19649 @item @code{C}@var{sig}@code{;}@var{addr} --- continue with signal
19650 @cindex @code{C} packet
19652 Continue with signal @var{sig} (hex signal number). If
19653 @code{;}@var{addr} is omitted, resume at same address.
19656 @xref{Stop Reply Packets}, for the reply specifications.
19658 @item @code{d} --- toggle debug @strong{(deprecated)}
19659 @cindex @code{d} packet
19663 @item @code{D} --- detach
19664 @cindex @code{D} packet
19666 Detach @value{GDBN} from the remote system. Sent to the remote target
19667 before @value{GDBN} disconnects via the @code{detach} command.
19671 @item @emph{no response}
19672 @value{GDBN} does not check for any response after sending this packet.
19675 @item @code{e} --- reserved
19677 Reserved for future use.
19679 @item @code{E} --- reserved
19681 Reserved for future use.
19683 @item @code{f} --- reserved
19685 Reserved for future use.
19687 @item @code{F}@var{RC}@code{,}@var{EE}@code{,}@var{CF}@code{;}@var{XX} --- Reply to target's F packet.
19688 @cindex @code{F} packet
19690 This packet is send by @value{GDBN} as reply to a @code{F} request packet
19691 sent by the target. This is part of the File-I/O protocol extension.
19692 @xref{File-I/O remote protocol extension}, for the specification.
19694 @item @code{g} --- read registers
19695 @anchor{read registers packet}
19696 @cindex @code{g} packet
19698 Read general registers.
19702 @item @var{XX@dots{}}
19703 Each byte of register data is described by two hex digits. The bytes
19704 with the register are transmitted in target byte order. The size of
19705 each register and their position within the @samp{g} @var{packet} are
19706 determined by the @value{GDBN} internal macros
19707 @var{DEPRECATED_REGISTER_RAW_SIZE} and @var{REGISTER_NAME} macros. The
19708 specification of several standard @code{g} packets is specified below.
19713 @item @code{G}@var{XX@dots{}} --- write regs
19714 @cindex @code{G} packet
19716 @xref{read registers packet}, for a description of the @var{XX@dots{}}
19727 @item @code{h} --- reserved
19729 Reserved for future use.
19731 @item @code{H}@var{c}@var{t@dots{}} --- set thread
19732 @cindex @code{H} packet
19734 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
19735 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
19736 should be @samp{c} for step and continue operations, @samp{g} for other
19737 operations. The thread designator @var{t@dots{}} may be -1, meaning all
19738 the threads, a thread number, or zero which means pick any thread.
19749 @c 'H': How restrictive (or permissive) is the thread model. If a
19750 @c thread is selected and stopped, are other threads allowed
19751 @c to continue to execute? As I mentioned above, I think the
19752 @c semantics of each command when a thread is selected must be
19753 @c described. For example:
19755 @c 'g': If the stub supports threads and a specific thread is
19756 @c selected, returns the register block from that thread;
19757 @c otherwise returns current registers.
19759 @c 'G' If the stub supports threads and a specific thread is
19760 @c selected, sets the registers of the register block of
19761 @c that thread; otherwise sets current registers.
19763 @item @code{i}@var{addr}@code{,}@var{nnn} --- cycle step @strong{(draft)}
19764 @anchor{cycle step packet}
19765 @cindex @code{i} packet
19767 Step the remote target by a single clock cycle. If @code{,}@var{nnn} is
19768 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
19769 step starting at that address.
19771 @item @code{I} --- signal then cycle step @strong{(reserved)}
19772 @cindex @code{I} packet
19774 @xref{step with signal packet}. @xref{cycle step packet}.
19776 @item @code{j} --- reserved
19778 Reserved for future use.
19780 @item @code{J} --- reserved
19782 Reserved for future use.
19784 @item @code{k} --- kill request
19785 @cindex @code{k} packet
19787 FIXME: @emph{There is no description of how to operate when a specific
19788 thread context has been selected (i.e.@: does 'k' kill only that
19791 @item @code{K} --- reserved
19793 Reserved for future use.
19795 @item @code{l} --- reserved
19797 Reserved for future use.
19799 @item @code{L} --- reserved
19801 Reserved for future use.
19803 @item @code{m}@var{addr}@code{,}@var{length} --- read memory
19804 @cindex @code{m} packet
19806 Read @var{length} bytes of memory starting at address @var{addr}.
19807 Neither @value{GDBN} nor the stub assume that sized memory transfers are
19808 assumed using word aligned accesses. FIXME: @emph{A word aligned memory
19809 transfer mechanism is needed.}
19813 @item @var{XX@dots{}}
19814 @var{XX@dots{}} is mem contents. Can be fewer bytes than requested if able
19815 to read only part of the data. Neither @value{GDBN} nor the stub assume
19816 that sized memory transfers are assumed using word aligned
19817 accesses. FIXME: @emph{A word aligned memory transfer mechanism is
19823 @item @code{M}@var{addr},@var{length}@code{:}@var{XX@dots{}} --- write mem
19824 @cindex @code{M} packet
19826 Write @var{length} bytes of memory starting at address @var{addr}.
19827 @var{XX@dots{}} is the data.
19834 for an error (this includes the case where only part of the data was
19838 @item @code{n} --- reserved
19840 Reserved for future use.
19842 @item @code{N} --- reserved
19844 Reserved for future use.
19846 @item @code{o} --- reserved
19848 Reserved for future use.
19850 @item @code{O} --- reserved
19852 Reserved for future use.
19854 @item @code{p}@var{n@dots{}} --- read reg @strong{(reserved)}
19855 @cindex @code{p} packet
19857 @xref{write register packet}.
19861 @item @var{r@dots{}.}
19862 The hex encoded value of the register in target byte order.
19865 @item @code{P}@var{n@dots{}}@code{=}@var{r@dots{}} --- write register
19866 @anchor{write register packet}
19867 @cindex @code{P} packet
19869 Write register @var{n@dots{}} with value @var{r@dots{}}, which contains two hex
19870 digits for each byte in the register (target byte order).
19880 @item @code{q}@var{query} --- general query
19881 @anchor{general query packet}
19882 @cindex @code{q} packet
19884 Request info about @var{query}. In general @value{GDBN} queries have a
19885 leading upper case letter. Custom vendor queries should use a company
19886 prefix (in lower case) ex: @samp{qfsf.var}. @var{query} may optionally
19887 be followed by a @samp{,} or @samp{;} separated list. Stubs must ensure
19888 that they match the full @var{query} name.
19892 @item @var{XX@dots{}}
19893 Hex encoded data from query. The reply can not be empty.
19897 Indicating an unrecognized @var{query}.
19900 @item @code{Q}@var{var}@code{=}@var{val} --- general set
19901 @cindex @code{Q} packet
19903 Set value of @var{var} to @var{val}.
19905 @xref{general query packet}, for a discussion of naming conventions.
19907 @item @code{r} --- reset @strong{(deprecated)}
19908 @cindex @code{r} packet
19910 Reset the entire system.
19912 @item @code{R}@var{XX} --- remote restart
19913 @cindex @code{R} packet
19915 Restart the program being debugged. @var{XX}, while needed, is ignored.
19916 This packet is only available in extended mode.
19920 @item @emph{no reply}
19921 The @samp{R} packet has no reply.
19924 @item @code{s}@var{addr} --- step
19925 @cindex @code{s} packet
19927 @var{addr} is address to resume. If @var{addr} is omitted, resume at
19931 @xref{Stop Reply Packets}, for the reply specifications.
19933 @item @code{S}@var{sig}@code{;}@var{addr} --- step with signal
19934 @anchor{step with signal packet}
19935 @cindex @code{S} packet
19937 Like @samp{C} but step not continue.
19940 @xref{Stop Reply Packets}, for the reply specifications.
19942 @item @code{t}@var{addr}@code{:}@var{PP}@code{,}@var{MM} --- search
19943 @cindex @code{t} packet
19945 Search backwards starting at address @var{addr} for a match with pattern
19946 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
19947 @var{addr} must be at least 3 digits.
19949 @item @code{T}@var{XX} --- thread alive
19950 @cindex @code{T} packet
19952 Find out if the thread XX is alive.
19957 thread is still alive
19962 @item @code{u} --- reserved
19964 Reserved for future use.
19966 @item @code{U} --- reserved
19968 Reserved for future use.
19970 @item @code{v} --- verbose packet prefix
19972 Packets starting with @code{v} are identified by a multi-letter name,
19973 up to the first @code{;} or @code{?} (or the end of the packet).
19975 @item @code{vCont}[;@var{action}[@code{:}@var{tid}]]... --- extended resume
19976 @cindex @code{vCont} packet
19978 Resume the inferior. Different actions may be specified for each thread.
19979 If an action is specified with no @var{tid}, then it is applied to any
19980 threads that don't have a specific action specified; if no default action is
19981 specified then other threads should remain stopped. Specifying multiple
19982 default actions is an error; specifying no actions is also an error.
19983 Thread IDs are specified in hexadecimal. Currently supported actions are:
19989 Continue with signal @var{sig}. @var{sig} should be two hex digits.
19993 Step with signal @var{sig}. @var{sig} should be two hex digits.
19996 The optional @var{addr} argument normally associated with these packets is
19997 not supported in @code{vCont}.
20000 @xref{Stop Reply Packets}, for the reply specifications.
20002 @item @code{vCont?} --- extended resume query
20003 @cindex @code{vCont?} packet
20005 Query support for the @code{vCont} packet.
20009 @item @code{vCont}[;@var{action}]...
20010 The @code{vCont} packet is supported. Each @var{action} is a supported
20011 command in the @code{vCont} packet.
20013 The @code{vCont} packet is not supported.
20016 @item @code{V} --- reserved
20018 Reserved for future use.
20020 @item @code{w} --- reserved
20022 Reserved for future use.
20024 @item @code{W} --- reserved
20026 Reserved for future use.
20028 @item @code{x} --- reserved
20030 Reserved for future use.
20032 @item @code{X}@var{addr}@code{,}@var{length}@var{:}@var{XX@dots{}} --- write mem (binary)
20033 @cindex @code{X} packet
20035 @var{addr} is address, @var{length} is number of bytes, @var{XX@dots{}}
20036 is binary data. The characters @code{$}, @code{#}, and @code{0x7d} are
20037 escaped using @code{0x7d}.
20047 @item @code{y} --- reserved
20049 Reserved for future use.
20051 @item @code{Y} reserved
20053 Reserved for future use.
20055 @item @code{z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- remove breakpoint or watchpoint @strong{(draft)}
20056 @itemx @code{Z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- insert breakpoint or watchpoint @strong{(draft)}
20057 @anchor{insert breakpoint or watchpoint packet}
20058 @cindex @code{z} packet
20059 @cindex @code{Z} packets
20061 Insert (@code{Z}) or remove (@code{z}) a @var{type} breakpoint or
20062 watchpoint starting at address @var{address} and covering the next
20063 @var{length} bytes.
20065 Each breakpoint and watchpoint packet @var{type} is documented
20068 @emph{Implementation notes: A remote target shall return an empty string
20069 for an unrecognized breakpoint or watchpoint packet @var{type}. A
20070 remote target shall support either both or neither of a given
20071 @code{Z}@var{type}@dots{} and @code{z}@var{type}@dots{} packet pair. To
20072 avoid potential problems with duplicate packets, the operations should
20073 be implemented in an idempotent way.}
20075 @item @code{z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- remove memory breakpoint @strong{(draft)}
20076 @item @code{Z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- insert memory breakpoint @strong{(draft)}
20077 @cindex @code{z0} packet
20078 @cindex @code{Z0} packet
20080 Insert (@code{Z0}) or remove (@code{z0}) a memory breakpoint at address
20081 @code{addr} of size @code{length}.
20083 A memory breakpoint is implemented by replacing the instruction at
20084 @var{addr} with a software breakpoint or trap instruction. The
20085 @code{length} is used by targets that indicates the size of the
20086 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
20087 @sc{mips} can insert either a 2 or 4 byte breakpoint).
20089 @emph{Implementation note: It is possible for a target to copy or move
20090 code that contains memory breakpoints (e.g., when implementing
20091 overlays). The behavior of this packet, in the presence of such a
20092 target, is not defined.}
20104 @item @code{z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- remove hardware breakpoint @strong{(draft)}
20105 @item @code{Z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- insert hardware breakpoint @strong{(draft)}
20106 @cindex @code{z1} packet
20107 @cindex @code{Z1} packet
20109 Insert (@code{Z1}) or remove (@code{z1}) a hardware breakpoint at
20110 address @code{addr} of size @code{length}.
20112 A hardware breakpoint is implemented using a mechanism that is not
20113 dependant on being able to modify the target's memory.
20115 @emph{Implementation note: A hardware breakpoint is not affected by code
20128 @item @code{z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- remove write watchpoint @strong{(draft)}
20129 @item @code{Z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- insert write watchpoint @strong{(draft)}
20130 @cindex @code{z2} packet
20131 @cindex @code{Z2} packet
20133 Insert (@code{Z2}) or remove (@code{z2}) a write watchpoint.
20145 @item @code{z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- remove read watchpoint @strong{(draft)}
20146 @item @code{Z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- insert read watchpoint @strong{(draft)}
20147 @cindex @code{z3} packet
20148 @cindex @code{Z3} packet
20150 Insert (@code{Z3}) or remove (@code{z3}) a read watchpoint.
20162 @item @code{z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- remove access watchpoint @strong{(draft)}
20163 @item @code{Z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- insert access watchpoint @strong{(draft)}
20164 @cindex @code{z4} packet
20165 @cindex @code{Z4} packet
20167 Insert (@code{Z4}) or remove (@code{z4}) an access watchpoint.
20181 @node Stop Reply Packets
20182 @section Stop Reply Packets
20183 @cindex stop reply packets
20185 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
20186 receive any of the below as a reply. In the case of the @samp{C},
20187 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
20188 when the target halts. In the below the exact meaning of @samp{signal
20189 number} is poorly defined. In general one of the UNIX signal numbering
20190 conventions is used.
20195 @var{AA} is the signal number
20197 @item @code{T}@var{AA}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}
20198 @cindex @code{T} packet reply
20200 @var{AA} = two hex digit signal number; @var{n...} = register number
20201 (hex), @var{r...} = target byte ordered register contents, size defined
20202 by @code{DEPRECATED_REGISTER_RAW_SIZE}; @var{n...} = @samp{thread},
20203 @var{r...} = thread process ID, this is a hex integer; @var{n...} =
20204 (@samp{watch} | @samp{rwatch} | @samp{awatch}, @var{r...} = data
20205 address, this is a hex integer; @var{n...} = other string not starting
20206 with valid hex digit. @value{GDBN} should ignore this @var{n...},
20207 @var{r...} pair and go on to the next. This way we can extend the
20212 The process exited, and @var{AA} is the exit status. This is only
20213 applicable to certain targets.
20217 The process terminated with signal @var{AA}.
20219 @item O@var{XX@dots{}}
20221 @var{XX@dots{}} is hex encoding of @sc{ascii} data. This can happen at
20222 any time while the program is running and the debugger should continue
20223 to wait for @samp{W}, @samp{T}, etc.
20225 @item F@var{call-id}@code{,}@var{parameter@dots{}}
20227 @var{call-id} is the identifier which says which host system call should
20228 be called. This is just the name of the function. Translation into the
20229 correct system call is only applicable as it's defined in @value{GDBN}.
20230 @xref{File-I/O remote protocol extension}, for a list of implemented
20233 @var{parameter@dots{}} is a list of parameters as defined for this very
20236 The target replies with this packet when it expects @value{GDBN} to call
20237 a host system call on behalf of the target. @value{GDBN} replies with
20238 an appropriate @code{F} packet and keeps up waiting for the next reply
20239 packet from the target. The latest @samp{C}, @samp{c}, @samp{S} or
20240 @samp{s} action is expected to be continued.
20241 @xref{File-I/O remote protocol extension}, for more details.
20245 @node General Query Packets
20246 @section General Query Packets
20248 The following set and query packets have already been defined.
20252 @item @code{q}@code{C} --- current thread
20254 Return the current thread id.
20258 @item @code{QC}@var{pid}
20259 Where @var{pid} is a HEX encoded 16 bit process id.
20261 Any other reply implies the old pid.
20264 @item @code{q}@code{fThreadInfo} -- all thread ids
20266 @code{q}@code{sThreadInfo}
20268 Obtain a list of active thread ids from the target (OS). Since there
20269 may be too many active threads to fit into one reply packet, this query
20270 works iteratively: it may require more than one query/reply sequence to
20271 obtain the entire list of threads. The first query of the sequence will
20272 be the @code{qf}@code{ThreadInfo} query; subsequent queries in the
20273 sequence will be the @code{qs}@code{ThreadInfo} query.
20275 NOTE: replaces the @code{qL} query (see below).
20279 @item @code{m}@var{id}
20281 @item @code{m}@var{id},@var{id}@dots{}
20282 a comma-separated list of thread ids
20284 (lower case 'el') denotes end of list.
20287 In response to each query, the target will reply with a list of one or
20288 more thread ids, in big-endian hex, separated by commas. @value{GDBN}
20289 will respond to each reply with a request for more thread ids (using the
20290 @code{qs} form of the query), until the target responds with @code{l}
20291 (lower-case el, for @code{'last'}).
20293 @item @code{q}@code{ThreadExtraInfo}@code{,}@var{id} --- extra thread info
20295 Where @var{id} is a thread-id in big-endian hex. Obtain a printable
20296 string description of a thread's attributes from the target OS. This
20297 string may contain anything that the target OS thinks is interesting for
20298 @value{GDBN} to tell the user about the thread. The string is displayed
20299 in @value{GDBN}'s @samp{info threads} display. Some examples of
20300 possible thread extra info strings are ``Runnable'', or ``Blocked on
20305 @item @var{XX@dots{}}
20306 Where @var{XX@dots{}} is a hex encoding of @sc{ascii} data, comprising
20307 the printable string containing the extra information about the thread's
20311 @item @code{q}@code{L}@var{startflag}@var{threadcount}@var{nextthread} --- query @var{LIST} or @var{threadLIST} @strong{(deprecated)}
20313 Obtain thread information from RTOS. Where: @var{startflag} (one hex
20314 digit) is one to indicate the first query and zero to indicate a
20315 subsequent query; @var{threadcount} (two hex digits) is the maximum
20316 number of threads the response packet can contain; and @var{nextthread}
20317 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
20318 returned in the response as @var{argthread}.
20320 NOTE: this query is replaced by the @code{q}@code{fThreadInfo} query
20325 @item @code{q}@code{M}@var{count}@var{done}@var{argthread}@var{thread@dots{}}
20326 Where: @var{count} (two hex digits) is the number of threads being
20327 returned; @var{done} (one hex digit) is zero to indicate more threads
20328 and one indicates no further threads; @var{argthreadid} (eight hex
20329 digits) is @var{nextthread} from the request packet; @var{thread@dots{}}
20330 is a sequence of thread IDs from the target. @var{threadid} (eight hex
20331 digits). See @code{remote.c:parse_threadlist_response()}.
20334 @item @code{q}@code{CRC:}@var{addr}@code{,}@var{length} --- compute CRC of memory block
20338 @item @code{E}@var{NN}
20339 An error (such as memory fault)
20340 @item @code{C}@var{CRC32}
20341 A 32 bit cyclic redundancy check of the specified memory region.
20344 @item @code{q}@code{Offsets} --- query sect offs
20346 Get section offsets that the target used when re-locating the downloaded
20347 image. @emph{Note: while a @code{Bss} offset is included in the
20348 response, @value{GDBN} ignores this and instead applies the @code{Data}
20349 offset to the @code{Bss} section.}
20353 @item @code{Text=}@var{xxx}@code{;Data=}@var{yyy}@code{;Bss=}@var{zzz}
20356 @item @code{q}@code{P}@var{mode}@var{threadid} --- thread info request
20358 Returns information on @var{threadid}. Where: @var{mode} is a hex
20359 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
20366 See @code{remote.c:remote_unpack_thread_info_response()}.
20368 @item @code{q}@code{Rcmd,}@var{command} --- remote command
20370 @var{command} (hex encoded) is passed to the local interpreter for
20371 execution. Invalid commands should be reported using the output string.
20372 Before the final result packet, the target may also respond with a
20373 number of intermediate @code{O}@var{output} console output packets.
20374 @emph{Implementors should note that providing access to a stubs's
20375 interpreter may have security implications}.
20380 A command response with no output.
20382 A command response with the hex encoded output string @var{OUTPUT}.
20383 @item @code{E}@var{NN}
20384 Indicate a badly formed request.
20386 When @samp{q}@samp{Rcmd} is not recognized.
20389 @item @code{qSymbol::} --- symbol lookup
20391 Notify the target that @value{GDBN} is prepared to serve symbol lookup
20392 requests. Accept requests from the target for the values of symbols.
20397 The target does not need to look up any (more) symbols.
20398 @item @code{qSymbol:}@var{sym_name}
20399 The target requests the value of symbol @var{sym_name} (hex encoded).
20400 @value{GDBN} may provide the value by using the
20401 @code{qSymbol:}@var{sym_value}:@var{sym_name} message, described below.
20404 @item @code{qSymbol:}@var{sym_value}:@var{sym_name} --- symbol value
20406 Set the value of @var{sym_name} to @var{sym_value}.
20408 @var{sym_name} (hex encoded) is the name of a symbol whose value the
20409 target has previously requested.
20411 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
20412 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
20418 The target does not need to look up any (more) symbols.
20419 @item @code{qSymbol:}@var{sym_name}
20420 The target requests the value of a new symbol @var{sym_name} (hex
20421 encoded). @value{GDBN} will continue to supply the values of symbols
20422 (if available), until the target ceases to request them.
20427 @node Register Packet Format
20428 @section Register Packet Format
20430 The following @samp{g}/@samp{G} packets have previously been defined.
20431 In the below, some thirty-two bit registers are transferred as
20432 sixty-four bits. Those registers should be zero/sign extended (which?)
20433 to fill the space allocated. Register bytes are transfered in target
20434 byte order. The two nibbles within a register byte are transfered
20435 most-significant - least-significant.
20441 All registers are transfered as thirty-two bit quantities in the order:
20442 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
20443 registers; fsr; fir; fp.
20447 All registers are transfered as sixty-four bit quantities (including
20448 thirty-two bit registers such as @code{sr}). The ordering is the same
20456 Example sequence of a target being re-started. Notice how the restart
20457 does not get any direct output:
20462 @emph{target restarts}
20465 <- @code{T001:1234123412341234}
20469 Example sequence of a target being stepped by a single instruction:
20472 -> @code{G1445@dots{}}
20477 <- @code{T001:1234123412341234}
20481 <- @code{1455@dots{}}
20485 @node File-I/O remote protocol extension
20486 @section File-I/O remote protocol extension
20487 @cindex File-I/O remote protocol extension
20490 * File-I/O Overview::
20491 * Protocol basics::
20492 * The F request packet::
20493 * The F reply packet::
20494 * Memory transfer::
20495 * The Ctrl-C message::
20497 * The isatty call::
20498 * The system call::
20499 * List of supported calls::
20500 * Protocol specific representation of datatypes::
20502 * File-I/O Examples::
20505 @node File-I/O Overview
20506 @subsection File-I/O Overview
20507 @cindex file-i/o overview
20509 The File I/O remote protocol extension (short: File-I/O) allows the
20510 target to use the hosts file system and console I/O when calling various
20511 system calls. System calls on the target system are translated into a
20512 remote protocol packet to the host system which then performs the needed
20513 actions and returns with an adequate response packet to the target system.
20514 This simulates file system operations even on targets that lack file systems.
20516 The protocol is defined host- and target-system independent. It uses
20517 it's own independent representation of datatypes and values. Both,
20518 @value{GDBN} and the target's @value{GDBN} stub are responsible for
20519 translating the system dependent values into the unified protocol values
20520 when data is transmitted.
20522 The communication is synchronous. A system call is possible only
20523 when GDB is waiting for the @samp{C}, @samp{c}, @samp{S} or @samp{s}
20524 packets. While @value{GDBN} handles the request for a system call,
20525 the target is stopped to allow deterministic access to the target's
20526 memory. Therefore File-I/O is not interuptible by target signals. It
20527 is possible to interrupt File-I/O by a user interrupt (Ctrl-C), though.
20529 The target's request to perform a host system call does not finish
20530 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
20531 after finishing the system call, the target returns to continuing the
20532 previous activity (continue, step). No additional continue or step
20533 request from @value{GDBN} is required.
20537 <- target requests 'system call X'
20538 target is stopped, @value{GDBN} executes system call
20539 -> GDB returns result
20540 ... target continues, GDB returns to wait for the target
20541 <- target hits breakpoint and sends a Txx packet
20544 The protocol is only used for files on the host file system and
20545 for I/O on the console. Character or block special devices, pipes,
20546 named pipes or sockets or any other communication method on the host
20547 system are not supported by this protocol.
20549 @node Protocol basics
20550 @subsection Protocol basics
20551 @cindex protocol basics, file-i/o
20553 The File-I/O protocol uses the @code{F} packet, as request as well
20554 as as reply packet. Since a File-I/O system call can only occur when
20555 @value{GDBN} is waiting for the continuing or stepping target, the
20556 File-I/O request is a reply that @value{GDBN} has to expect as a result
20557 of a former @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
20558 This @code{F} packet contains all information needed to allow @value{GDBN}
20559 to call the appropriate host system call:
20563 A unique identifier for the requested system call.
20566 All parameters to the system call. Pointers are given as addresses
20567 in the target memory address space. Pointers to strings are given as
20568 pointer/length pair. Numerical values are given as they are.
20569 Numerical control values are given in a protocol specific representation.
20573 At that point @value{GDBN} has to perform the following actions.
20577 If parameter pointer values are given, which point to data needed as input
20578 to a system call, @value{GDBN} requests this data from the target with a
20579 standard @code{m} packet request. This additional communication has to be
20580 expected by the target implementation and is handled as any other @code{m}
20584 @value{GDBN} translates all value from protocol representation to host
20585 representation as needed. Datatypes are coerced into the host types.
20588 @value{GDBN} calls the system call
20591 It then coerces datatypes back to protocol representation.
20594 If pointer parameters in the request packet point to buffer space in which
20595 a system call is expected to copy data to, the data is transmitted to the
20596 target using a @code{M} or @code{X} packet. This packet has to be expected
20597 by the target implementation and is handled as any other @code{M} or @code{X}
20602 Eventually @value{GDBN} replies with another @code{F} packet which contains all
20603 necessary information for the target to continue. This at least contains
20610 @code{errno}, if has been changed by the system call.
20617 After having done the needed type and value coercion, the target continues
20618 the latest continue or step action.
20620 @node The F request packet
20621 @subsection The @code{F} request packet
20622 @cindex file-i/o request packet
20623 @cindex @code{F} request packet
20625 The @code{F} request packet has the following format:
20630 @code{F}@var{call-id}@code{,}@var{parameter@dots{}}
20633 @var{call-id} is the identifier to indicate the host system call to be called.
20634 This is just the name of the function.
20636 @var{parameter@dots{}} are the parameters to the system call.
20640 Parameters are hexadecimal integer values, either the real values in case
20641 of scalar datatypes, as pointers to target buffer space in case of compound
20642 datatypes and unspecified memory areas or as pointer/length pairs in case
20643 of string parameters. These are appended to the call-id, each separated
20644 from its predecessor by a comma. All values are transmitted in ASCII
20645 string representation, pointer/length pairs separated by a slash.
20647 @node The F reply packet
20648 @subsection The @code{F} reply packet
20649 @cindex file-i/o reply packet
20650 @cindex @code{F} reply packet
20652 The @code{F} reply packet has the following format:
20657 @code{F}@var{retcode}@code{,}@var{errno}@code{,}@var{Ctrl-C flag}@code{;}@var{call specific attachment}
20660 @var{retcode} is the return code of the system call as hexadecimal value.
20662 @var{errno} is the errno set by the call, in protocol specific representation.
20663 This parameter can be omitted if the call was successful.
20665 @var{Ctrl-C flag} is only send if the user requested a break. In this
20666 case, @var{errno} must be send as well, even if the call was successful.
20667 The @var{Ctrl-C flag} itself consists of the character 'C':
20674 or, if the call was interupted before the host call has been performed:
20681 assuming 4 is the protocol specific representation of @code{EINTR}.
20685 @node Memory transfer
20686 @subsection Memory transfer
20687 @cindex memory transfer, in file-i/o protocol
20689 Structured data which is transferred using a memory read or write as e.g.@:
20690 a @code{struct stat} is expected to be in a protocol specific format with
20691 all scalar multibyte datatypes being big endian. This should be done by
20692 the target before the @code{F} packet is sent resp.@: by @value{GDBN} before
20693 it transfers memory to the target. Transferred pointers to structured
20694 data should point to the already coerced data at any time.
20696 @node The Ctrl-C message
20697 @subsection The Ctrl-C message
20698 @cindex ctrl-c message, in file-i/o protocol
20700 A special case is, if the @var{Ctrl-C flag} is set in the @value{GDBN}
20701 reply packet. In this case the target should behave, as if it had
20702 gotten a break message. The meaning for the target is ``system call
20703 interupted by @code{SIGINT}''. Consequentially, the target should actually stop
20704 (as with a break message) and return to @value{GDBN} with a @code{T02}
20705 packet. In this case, it's important for the target to know, in which
20706 state the system call was interrupted. Since this action is by design
20707 not an atomic operation, we have to differ between two cases:
20711 The system call hasn't been performed on the host yet.
20714 The system call on the host has been finished.
20718 These two states can be distinguished by the target by the value of the
20719 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
20720 call hasn't been performed. This is equivalent to the @code{EINTR} handling
20721 on POSIX systems. In any other case, the target may presume that the
20722 system call has been finished --- successful or not --- and should behave
20723 as if the break message arrived right after the system call.
20725 @value{GDBN} must behave reliable. If the system call has not been called
20726 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
20727 @code{errno} in the packet. If the system call on the host has been finished
20728 before the user requests a break, the full action must be finshed by
20729 @value{GDBN}. This requires sending @code{M} or @code{X} packets as they fit.
20730 The @code{F} packet may only be send when either nothing has happened
20731 or the full action has been completed.
20734 @subsection Console I/O
20735 @cindex console i/o as part of file-i/o
20737 By default and if not explicitely closed by the target system, the file
20738 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
20739 on the @value{GDBN} console is handled as any other file output operation
20740 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
20741 by @value{GDBN} so that after the target read request from file descriptor
20742 0 all following typing is buffered until either one of the following
20747 The user presses @kbd{Ctrl-C}. The behaviour is as explained above, the
20749 system call is treated as finished.
20752 The user presses @kbd{Enter}. This is treated as end of input with a trailing
20756 The user presses @kbd{Ctrl-D}. This is treated as end of input. No trailing
20757 character, especially no Ctrl-D is appended to the input.
20761 If the user has typed more characters as fit in the buffer given to
20762 the read call, the trailing characters are buffered in @value{GDBN} until
20763 either another @code{read(0, @dots{})} is requested by the target or debugging
20764 is stopped on users request.
20766 @node The isatty call
20767 @subsection The isatty(3) call
20768 @cindex isatty call, file-i/o protocol
20770 A special case in this protocol is the library call @code{isatty} which
20771 is implemented as it's own call inside of this protocol. It returns
20772 1 to the target if the file descriptor given as parameter is attached
20773 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
20774 would require implementing @code{ioctl} and would be more complex than
20777 @node The system call
20778 @subsection The system(3) call
20779 @cindex system call, file-i/o protocol
20781 The other special case in this protocol is the @code{system} call which
20782 is implemented as it's own call, too. @value{GDBN} is taking over the full
20783 task of calling the necessary host calls to perform the @code{system}
20784 call. The return value of @code{system} is simplified before it's returned
20785 to the target. Basically, the only signal transmitted back is @code{EINTR}
20786 in case the user pressed @kbd{Ctrl-C}. Otherwise the return value consists
20787 entirely of the exit status of the called command.
20789 Due to security concerns, the @code{system} call is refused to be called
20790 by @value{GDBN} by default. The user has to allow this call explicitly by
20794 @kindex set remote system-call-allowed 1
20795 @item @code{set remote system-call-allowed 1}
20798 Disabling the @code{system} call is done by
20801 @kindex set remote system-call-allowed 0
20802 @item @code{set remote system-call-allowed 0}
20805 The current setting is shown by typing
20808 @kindex show remote system-call-allowed
20809 @item @code{show remote system-call-allowed}
20812 @node List of supported calls
20813 @subsection List of supported calls
20814 @cindex list of supported file-i/o calls
20831 @unnumberedsubsubsec open
20832 @cindex open, file-i/o system call
20836 int open(const char *pathname, int flags);
20837 int open(const char *pathname, int flags, mode_t mode);
20840 Fopen,pathptr/len,flags,mode
20844 @code{flags} is the bitwise or of the following values:
20848 If the file does not exist it will be created. The host
20849 rules apply as far as file ownership and time stamps
20853 When used with O_CREAT, if the file already exists it is
20854 an error and open() fails.
20857 If the file already exists and the open mode allows
20858 writing (O_RDWR or O_WRONLY is given) it will be
20859 truncated to length 0.
20862 The file is opened in append mode.
20865 The file is opened for reading only.
20868 The file is opened for writing only.
20871 The file is opened for reading and writing.
20874 Each other bit is silently ignored.
20879 @code{mode} is the bitwise or of the following values:
20883 User has read permission.
20886 User has write permission.
20889 Group has read permission.
20892 Group has write permission.
20895 Others have read permission.
20898 Others have write permission.
20901 Each other bit is silently ignored.
20906 @exdent Return value:
20907 open returns the new file descriptor or -1 if an error
20915 pathname already exists and O_CREAT and O_EXCL were used.
20918 pathname refers to a directory.
20921 The requested access is not allowed.
20924 pathname was too long.
20927 A directory component in pathname does not exist.
20930 pathname refers to a device, pipe, named pipe or socket.
20933 pathname refers to a file on a read-only filesystem and
20934 write access was requested.
20937 pathname is an invalid pointer value.
20940 No space on device to create the file.
20943 The process already has the maximum number of files open.
20946 The limit on the total number of files open on the system
20950 The call was interrupted by the user.
20954 @unnumberedsubsubsec close
20955 @cindex close, file-i/o system call
20964 @exdent Return value:
20965 close returns zero on success, or -1 if an error occurred.
20972 fd isn't a valid open file descriptor.
20975 The call was interrupted by the user.
20979 @unnumberedsubsubsec read
20980 @cindex read, file-i/o system call
20984 int read(int fd, void *buf, unsigned int count);
20987 Fread,fd,bufptr,count
20989 @exdent Return value:
20990 On success, the number of bytes read is returned.
20991 Zero indicates end of file. If count is zero, read
20992 returns zero as well. On error, -1 is returned.
20999 fd is not a valid file descriptor or is not open for
21003 buf is an invalid pointer value.
21006 The call was interrupted by the user.
21010 @unnumberedsubsubsec write
21011 @cindex write, file-i/o system call
21015 int write(int fd, const void *buf, unsigned int count);
21018 Fwrite,fd,bufptr,count
21020 @exdent Return value:
21021 On success, the number of bytes written are returned.
21022 Zero indicates nothing was written. On error, -1
21030 fd is not a valid file descriptor or is not open for
21034 buf is an invalid pointer value.
21037 An attempt was made to write a file that exceeds the
21038 host specific maximum file size allowed.
21041 No space on device to write the data.
21044 The call was interrupted by the user.
21048 @unnumberedsubsubsec lseek
21049 @cindex lseek, file-i/o system call
21053 long lseek (int fd, long offset, int flag);
21056 Flseek,fd,offset,flag
21059 @code{flag} is one of:
21063 The offset is set to offset bytes.
21066 The offset is set to its current location plus offset
21070 The offset is set to the size of the file plus offset
21075 @exdent Return value:
21076 On success, the resulting unsigned offset in bytes from
21077 the beginning of the file is returned. Otherwise, a
21078 value of -1 is returned.
21085 fd is not a valid open file descriptor.
21088 fd is associated with the @value{GDBN} console.
21091 flag is not a proper value.
21094 The call was interrupted by the user.
21098 @unnumberedsubsubsec rename
21099 @cindex rename, file-i/o system call
21103 int rename(const char *oldpath, const char *newpath);
21106 Frename,oldpathptr/len,newpathptr/len
21108 @exdent Return value:
21109 On success, zero is returned. On error, -1 is returned.
21116 newpath is an existing directory, but oldpath is not a
21120 newpath is a non-empty directory.
21123 oldpath or newpath is a directory that is in use by some
21127 An attempt was made to make a directory a subdirectory
21131 A component used as a directory in oldpath or new
21132 path is not a directory. Or oldpath is a directory
21133 and newpath exists but is not a directory.
21136 oldpathptr or newpathptr are invalid pointer values.
21139 No access to the file or the path of the file.
21143 oldpath or newpath was too long.
21146 A directory component in oldpath or newpath does not exist.
21149 The file is on a read-only filesystem.
21152 The device containing the file has no room for the new
21156 The call was interrupted by the user.
21160 @unnumberedsubsubsec unlink
21161 @cindex unlink, file-i/o system call
21165 int unlink(const char *pathname);
21168 Funlink,pathnameptr/len
21170 @exdent Return value:
21171 On success, zero is returned. On error, -1 is returned.
21178 No access to the file or the path of the file.
21181 The system does not allow unlinking of directories.
21184 The file pathname cannot be unlinked because it's
21185 being used by another process.
21188 pathnameptr is an invalid pointer value.
21191 pathname was too long.
21194 A directory component in pathname does not exist.
21197 A component of the path is not a directory.
21200 The file is on a read-only filesystem.
21203 The call was interrupted by the user.
21207 @unnumberedsubsubsec stat/fstat
21208 @cindex fstat, file-i/o system call
21209 @cindex stat, file-i/o system call
21213 int stat(const char *pathname, struct stat *buf);
21214 int fstat(int fd, struct stat *buf);
21217 Fstat,pathnameptr/len,bufptr
21220 @exdent Return value:
21221 On success, zero is returned. On error, -1 is returned.
21228 fd is not a valid open file.
21231 A directory component in pathname does not exist or the
21232 path is an empty string.
21235 A component of the path is not a directory.
21238 pathnameptr is an invalid pointer value.
21241 No access to the file or the path of the file.
21244 pathname was too long.
21247 The call was interrupted by the user.
21251 @unnumberedsubsubsec gettimeofday
21252 @cindex gettimeofday, file-i/o system call
21256 int gettimeofday(struct timeval *tv, void *tz);
21259 Fgettimeofday,tvptr,tzptr
21261 @exdent Return value:
21262 On success, 0 is returned, -1 otherwise.
21269 tz is a non-NULL pointer.
21272 tvptr and/or tzptr is an invalid pointer value.
21276 @unnumberedsubsubsec isatty
21277 @cindex isatty, file-i/o system call
21281 int isatty(int fd);
21286 @exdent Return value:
21287 Returns 1 if fd refers to the @value{GDBN} console, 0 otherwise.
21294 The call was interrupted by the user.
21298 @unnumberedsubsubsec system
21299 @cindex system, file-i/o system call
21303 int system(const char *command);
21306 Fsystem,commandptr/len
21308 @exdent Return value:
21309 The value returned is -1 on error and the return status
21310 of the command otherwise. Only the exit status of the
21311 command is returned, which is extracted from the hosts
21312 system return value by calling WEXITSTATUS(retval).
21313 In case /bin/sh could not be executed, 127 is returned.
21320 The call was interrupted by the user.
21323 @node Protocol specific representation of datatypes
21324 @subsection Protocol specific representation of datatypes
21325 @cindex protocol specific representation of datatypes, in file-i/o protocol
21328 * Integral datatypes::
21334 @node Integral datatypes
21335 @unnumberedsubsubsec Integral datatypes
21336 @cindex integral datatypes, in file-i/o protocol
21338 The integral datatypes used in the system calls are
21341 int@r{,} unsigned int@r{,} long@r{,} unsigned long@r{,} mode_t @r{and} time_t
21344 @code{Int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
21345 implemented as 32 bit values in this protocol.
21347 @code{Long} and @code{unsigned long} are implemented as 64 bit types.
21349 @xref{Limits}, for corresponding MIN and MAX values (similar to those
21350 in @file{limits.h}) to allow range checking on host and target.
21352 @code{time_t} datatypes are defined as seconds since the Epoch.
21354 All integral datatypes transferred as part of a memory read or write of a
21355 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
21358 @node Pointer values
21359 @unnumberedsubsubsec Pointer values
21360 @cindex pointer values, in file-i/o protocol
21362 Pointers to target data are transmitted as they are. An exception
21363 is made for pointers to buffers for which the length isn't
21364 transmitted as part of the function call, namely strings. Strings
21365 are transmitted as a pointer/length pair, both as hex values, e.g.@:
21372 which is a pointer to data of length 18 bytes at position 0x1aaf.
21373 The length is defined as the full string length in bytes, including
21374 the trailing null byte. Example:
21377 ``hello, world'' at address 0x123456
21388 @unnumberedsubsubsec struct stat
21389 @cindex struct stat, in file-i/o protocol
21391 The buffer of type struct stat used by the target and @value{GDBN} is defined
21396 unsigned int st_dev; /* device */
21397 unsigned int st_ino; /* inode */
21398 mode_t st_mode; /* protection */
21399 unsigned int st_nlink; /* number of hard links */
21400 unsigned int st_uid; /* user ID of owner */
21401 unsigned int st_gid; /* group ID of owner */
21402 unsigned int st_rdev; /* device type (if inode device) */
21403 unsigned long st_size; /* total size, in bytes */
21404 unsigned long st_blksize; /* blocksize for filesystem I/O */
21405 unsigned long st_blocks; /* number of blocks allocated */
21406 time_t st_atime; /* time of last access */
21407 time_t st_mtime; /* time of last modification */
21408 time_t st_ctime; /* time of last change */
21412 The integral datatypes are conforming to the definitions given in the
21413 approriate section (see @ref{Integral datatypes}, for details) so this
21414 structure is of size 64 bytes.
21416 The values of several fields have a restricted meaning and/or
21423 st_ino: No valid meaning for the target. Transmitted unchanged.
21425 st_mode: Valid mode bits are described in Appendix C. Any other
21426 bits have currently no meaning for the target.
21428 st_uid: No valid meaning for the target. Transmitted unchanged.
21430 st_gid: No valid meaning for the target. Transmitted unchanged.
21432 st_rdev: No valid meaning for the target. Transmitted unchanged.
21434 st_atime, st_mtime, st_ctime:
21435 These values have a host and file system dependent
21436 accuracy. Especially on Windows hosts the file systems
21437 don't support exact timing values.
21440 The target gets a struct stat of the above representation and is
21441 responsible to coerce it to the target representation before
21444 Note that due to size differences between the host and target
21445 representation of stat members, these members could eventually
21446 get truncated on the target.
21448 @node struct timeval
21449 @unnumberedsubsubsec struct timeval
21450 @cindex struct timeval, in file-i/o protocol
21452 The buffer of type struct timeval used by the target and @value{GDBN}
21453 is defined as follows:
21457 time_t tv_sec; /* second */
21458 long tv_usec; /* microsecond */
21462 The integral datatypes are conforming to the definitions given in the
21463 approriate section (see @ref{Integral datatypes}, for details) so this
21464 structure is of size 8 bytes.
21467 @subsection Constants
21468 @cindex constants, in file-i/o protocol
21470 The following values are used for the constants inside of the
21471 protocol. @value{GDBN} and target are resposible to translate these
21472 values before and after the call as needed.
21483 @unnumberedsubsubsec Open flags
21484 @cindex open flags, in file-i/o protocol
21486 All values are given in hexadecimal representation.
21498 @node mode_t values
21499 @unnumberedsubsubsec mode_t values
21500 @cindex mode_t values, in file-i/o protocol
21502 All values are given in octal representation.
21519 @unnumberedsubsubsec Errno values
21520 @cindex errno values, in file-i/o protocol
21522 All values are given in decimal representation.
21547 EUNKNOWN is used as a fallback error value if a host system returns
21548 any error value not in the list of supported error numbers.
21551 @unnumberedsubsubsec Lseek flags
21552 @cindex lseek flags, in file-i/o protocol
21561 @unnumberedsubsubsec Limits
21562 @cindex limits, in file-i/o protocol
21564 All values are given in decimal representation.
21567 INT_MIN -2147483648
21569 UINT_MAX 4294967295
21570 LONG_MIN -9223372036854775808
21571 LONG_MAX 9223372036854775807
21572 ULONG_MAX 18446744073709551615
21575 @node File-I/O Examples
21576 @subsection File-I/O Examples
21577 @cindex file-i/o examples
21579 Example sequence of a write call, file descriptor 3, buffer is at target
21580 address 0x1234, 6 bytes should be written:
21583 <- @code{Fwrite,3,1234,6}
21584 @emph{request memory read from target}
21587 @emph{return "6 bytes written"}
21591 Example sequence of a read call, file descriptor 3, buffer is at target
21592 address 0x1234, 6 bytes should be read:
21595 <- @code{Fread,3,1234,6}
21596 @emph{request memory write to target}
21597 -> @code{X1234,6:XXXXXX}
21598 @emph{return "6 bytes read"}
21602 Example sequence of a read call, call fails on the host due to invalid
21603 file descriptor (EBADF):
21606 <- @code{Fread,3,1234,6}
21610 Example sequence of a read call, user presses Ctrl-C before syscall on
21614 <- @code{Fread,3,1234,6}
21619 Example sequence of a read call, user presses Ctrl-C after syscall on
21623 <- @code{Fread,3,1234,6}
21624 -> @code{X1234,6:XXXXXX}
21628 @include agentexpr.texi
21640 % I think something like @colophon should be in texinfo. In the
21642 \long\def\colophon{\hbox to0pt{}\vfill
21643 \centerline{The body of this manual is set in}
21644 \centerline{\fontname\tenrm,}
21645 \centerline{with headings in {\bf\fontname\tenbf}}
21646 \centerline{and examples in {\tt\fontname\tentt}.}
21647 \centerline{{\it\fontname\tenit\/},}
21648 \centerline{{\bf\fontname\tenbf}, and}
21649 \centerline{{\sl\fontname\tensl\/}}
21650 \centerline{are used for emphasis.}\vfill}
21652 % Blame: doc@cygnus.com, 1991.